METHOD FOR CONTROLLING A WIND POWER PLANT, WIND PLANT, AND, WIND POWER INSTALLATION

专利摘要:
method for controlling a wind farm, wind farm, and wind power installation. the invention relates to a method for controlling a wind power plant (200) comprising several wind power installations (202) (202) to supply electric power to an alternating current grid (206) at a common coupling point (pcc) ( 204). the method comprises feeding a three-phase power at the common coupling point (204), identifying a mains voltage (un) at the common coupling point, comparing the mains voltage (un) that was identified at the common coupling point (204) with at least a predetermined setpoint value, determine setpoint values for wind power installations (202) depending on the comparison conducted to satisfy a stability criterion at the common coupling point (204), transmit the determined values of setpoint for the installation control units (212) of the individual wind energy installations (202), and produce electrical energy (i'1, i'2, i'3) in each of the wind energy installations (202 ) depending on the predetermined setpoint values, to be fed together at the common coupling point (204).
公开号:BR112015001114B1
申请号:R112015001114-4
申请日:2013-07-02
公开日:2021-04-27
发明作者:Volker Diedrichs
申请人:Wobben Properties Gmbh；
IPC主号:

专利说明:

[001] The present invention relates to a method for controlling a wind farm, as well as such a wind farm. In particular, the present invention relates to the control of a wind farm to supply electricity to an alternating current grid at a common coupling point, as well as such a wind farm.
[002] Wind power plants are generally known; they refer to several wind power installations that are included together in organizational terms. In particular, all of the wind power installations that belong to a wind farm supply an alternating current electrical network at a common coupling point. Usually, each wind energy installation itself generates an electrical current that must be fed, that is, usually a three-phase electrical current that must be fed. For this purpose, the installation of wind energy refers to the voltage in the AC grid, which must be supplied, which is also simply referred to below as the grid, in particular according to the amplitude, frequency, and phase of the voltage.
[003] In addition, in the meantime it is known and desirable to use wind power installations, particularly wind farms, to support the grid. In other words, the objective is not only to feed as much energy as possible to the grid, but also to feed it in such a way, and, if necessary, even to reduce the powered power, that the grid can be supported in electrical terms. . The first patent applications that dealt with such topics are WO 02/086315, WO 02/086314, WO 01/86143, WO99 / 33165, and WO 02/044560. One method is known from WO 03/030329 A1, according to which all of the energy output from the wind farm can be reduced externally by the operator of the connected electrical supply network.
[004] In addition, reference is made to the "Loss of (Angle of) stability of wind energy installations" test by V. Diedrichs et al., Submitted and presented at the "10th International Workshop on Large-Scale Integration of Wind Power into Power Systems as well as on Transmission Networks for Offshore Wind Farms ", Aarhus (Denmark), October 25 - 26, 2011". There, reference was basically made to the problem that loss of stability in the network can basically also occur for power installations. wind energy that are connected to the supply network, for power.
[005] Here, the operator can predetermine a percentage value, by which the respective wind energy installations can reduce their power.
[006] Such proposals are already partially provided to stabilize the network. In particular, these solutions consider an adjustment of the power supplied to the current demand; in particular, they must consider a power surplus or under-supply in the network.
[007] When supplying electricity, that is, both active power as well as reactive power, there is a global need to ensure the stability of energy systems and energy installations, including wind power installations and wind farms. Here, stability refers to frequency and voltage, simultaneously, in all areas of the power system.
[008] The loss of such stability is generally also referred to as "Loss of stability", and can be abbreviated as LOS. "Loss of stability" describes physical processes and conditions, which no longer guarantee that stability, and illustrates that these should be avoided or stopped as soon as possible, if they already exist. These problems are basically rare, but are therefore increasingly serious. For example, this includes a disconnection, generally known, of portions of the grid, as occurred, for example, in 2004 in the USA, or of the global power system, as occurred in 2004 in Italy.
[009] Basically, technical knowledge regarding the topic of stability has been developed in depth and dealt with in a wide variety of publications. An internationally recognized standard work is Kundur, P .: Power Systems Stability and Control, McGraw-Hill.
[0010] The so-called "short-circuit ratio" (SCR) serves to assess the operability of power installations on a global scale, most often with synchronous generators, at the point of common couplings with power systems.
[0011] In addition to such an overall or absolute assessment through SCR, other assessments are conducted according to special criteria. Such criteria point to different types of processes that are relevant to stability, such as the process of a voltage depression, or the stability of an angle, that is, phase angles in the network, which is generally referred to as "angle stability. ". These assessments particularly provide metrics or standards for stability distances.
[0012] This short-circuit current ratio is the ratio between the short-circuit energy and the connected load. Here, short-circuit energy is the energy that the respective supply network at the point considered to be the common coupling, to which the relevant power installation must be connected, can provide in the event of a short circuit. The connected load is the connected load of the power installation to be connected, in particular the nominal capacity of the generator to be connected.
[0013] Regarding the requirements of a short-circuit current ratio, SCR, a short-circuit current ratio of SCR> 4, however, practically often SCR> 10, was considered necessary for the reliable operation of power with synchronous generators. For this purpose, for Germany, reference is made to the 2007 VDN Transmission Code. A SCR short-circuit current ratio> 4 ... 6 is usually required in the market for the connection of wind power installations or wind power plants.
[0014] The consequently required quantity of the SCR limits the power of the energy installation at a given "common coupling point" (PCC), as it is generally referred to, or determines the required network reinforcements.
[0015] The short-circuit energy is a network characteristic at the respective common coupling point, and thus initially a predetermined value, if the respective network already exists there. As the short-circuit current ratio must not fall below a certain value, that is, particularly in the area of 4 to 6, the power of the energy installation or of a wind power plant that must be connected to a coupling point common is limited. Therefore, power installations can only be connected up to a certain value, or it becomes necessary to expand the network in order to facilitate the connection of the power installation with the highest output.
[0016] The German Patent Mark Office investigated the following state of the art with respect to the priority order: DE 10 2009 030 725 A2, WO2011 / 050807 A2 and Loss of (Angle) Stability of Wind Power Installations - The Phenomenon Underestimated in the Very Low Short Circuit Ratio Case at the "10th International Workshop on Large- Scale Integration of Wind Power into Power Systems as well as on Transmission Networks for Offshore Wind Farms", Aarhus, October 26, 2011 by Volker Diedrichs, Alfred Beekmann, Stephan Adloff.
[0017] The purpose of the present invention is to address at least one of the problems mentioned above. In particular, a solution must be proposed, whereby a wind power installation or a wind power plant can be connected to a common coupling point and operated in a stable manner, with a short-circuit current ratio that is so low as possible, particularly with a SCR short-circuit current ratio> 1.5 ... 2. In particular, this must be achieved for a wind power installation or a wind power plant with a power supply using full power converters, that is, the so-called voltage-controlled inverters, which are also referred to as "source converters. of tension "(VSC). An alternative solution must at least be proposed.
[0018] According to the invention, a method for controlling a wind power plant comprising one or more wind power installations is proposed according to claim 1. According to this, a wind power plant with several wind power installations is proposed, which supplies electrical energy to an alternating current electrical network at a common common coupling point (PCC). The method for controlling the wind farm can thus also be considered or referred to as a method for feeding electricity through a wind farm. Here, three-phase current is first fed to the common coupling point.
[0019] In addition, a mains voltage is identified at the common coupling point. The detection is particularly carried out by measurement, in which the values of the given grid voltage, which are currently still used, can still be processed, particularly by arithmetic processing.
[0020] The identified mains voltage is then compared with at least a given setpoint value. The method refers to the stable supply of electrical energy to an alternating current electrical network, which is simply referred to below as the network. Consequently, the expert knows that the comparison must be carried out as quickly as possible in real time, and as often as possible, preferably continuously or almost continuously. In addition, a common AC network is basically considered, which has a 50 Hz or 60 Hz frequency network. Consequently, the detection of the mains voltage must be performed quickly and frequently at the common coupling point.
[0021] In addition, at least one setpoint value is determined for each wind power installation. This setpoint value is determined depending on the comparison made, that is, the identified mains voltage with a setpoint value for the voltage. The respective setpoint value is determined in such a way that a stability criterion can be implemented at the common coupling point. Consequently, this setpoint value is also determined on an ongoing basis, and adjusted depending on the comparison, which is also carried out on an ongoing basis, and is thus updated according to a changing situation. As a result, the setpoint value can change constantly, and thus, there are several setpoint values, temporally subsequent. Consequently, the method also refers to the determination of setpoint values. These setpoint values can be identical (only initially, as the case may be) for various wind power installations in the plant, or they can be adjusted individually for each wind power installation. Such an individual adjustment depends, not least, on the type of setpoint value, as well as whether or not the respective wind energy installations are the same. The assignment of the setpoint value may also depend on the local arrangement of the respective wind energy installations in the plant, that is, particularly if the electrical connection lines from the respective wind energy installation in common, common coupling point are significantly different of the electrical connection between the respective wind energy installation and the common coupling point.
[0022] Setpoint values are transferred or sent to the installation control units of the individual wind power installations. Therefore, it is provided that each wind power installation has its own control unit, and that setpoint values are transferred or sent to that control unit. As a result, the wind power installation or its individual installation control unit receives at least one setpoint value or a sequence of setpoint values from a central location; however, it individually adjusts the specific control in the wind power installation. In particular, the three-phase current, which must be supplied, that is, the individual phase currents, which must be supplied according to the amount, phase and frequency, is specifically produced by each installation control unit of each energy installation. wind power, individually.
[0023] The electrical currents produced to supply each wind power installation are then jointly transferred or sent to, and fed to, the common coupling point of the wind farm. In particular, for this purpose, the currents are linearly superimposed with other currents from other wind power installations. For this purpose, each wind power installation may comprise an output inductor and / or an output transformer.
[0024] Basically, the reasons for determining a short-circuit current ratio of SCR> 4, or even SCR> 6, are justified. With low short-circuit current ratios, strong increases or decreases (in particular, exponential increases or decreases in current sensitivities at the common coupling point [PCC]) are to be expected, that is, depending on the active power and power reactive, respectively fed, or as a response to this. Here, internal controls in wind power installations can become unstable, if the voltage at the common coupling point is used as a current value for these controls. In addition, tension controls may become unstable. Similarly, there is a threat of a loss of stability based on the mechanisms of a stress depression and / or based on a stability angle or a loss of such a stability angle.
[0025] The proposed solution is particularly intended to prevent the internal controls of wind power installations from becoming unstable when using the voltage at the common coupling point as a current value.
[0026] Similarly, voltage controls must be prevented from becoming unstable, which use the reactive power of the wind power installation or wind farm as a manipulated variable.
[0027] Finally, it must also be prevented that the system, that is, particularly the supply of the wind power plant, is too close to a stability limit or a so-called LOS limit (loss of stability).
[0028] Preferably, it is proposed that the current that is fed at the common coupling point is also identified, and particularly measured there, or that the fed current is identified based on a measurement, directly at, or directly behind, the common coupling. This leads to the control being based on the currents, which are currently fed. Possible deviations between the adjusted current or the adjusted currents and the current, which is currently supplied, are thus taken into account. Similarly, the power that is currently supplied, particularly the active powered power, can be identified, if the respective currents and voltages are known according to the amount and phase. During measurement on the network, the network response is also identified and considered. This grid response reacts to the energy currently fed, that is, to the currents currently fed, and, with respect to this, the measurements allow the grid responses to be attributed to the electrical variables currently fed.
[0029] In addition or alternatively, the detection of the fed current, the detection of the mains voltage at the common coupling point, the comparison of the mains voltage measured at the common coupling point with at least a predetermined setpoint value and / or the determination of the setpoint value is done by a central control unit. Therefore, a unit for several wind power installations, particularly for all wind power installations at the plant, is provided, which identifies, measures and / or calculates the said sensitive data. This also serves to prevent individual wind power installations or their controls from working against each other, because such a central control unit can also predetermine a setpoint value that is stable over time. A minor control fluctuation, therefore, is not immediately noticeable, and / or may not result, or is very unlikely to result, in a chain reaction for the other wind power installations connected to the same common coupling point. In particular, such effects are avoided, so that, for example, a first wind energy installation leads to a voltage change at the common coupling point, and a second wind energy installation, based on this identified voltage change, for example , acts contrary in terms of control, which, in turn, can lead to an effect, such as a change in voltage, which, in turn, causes the first installation of electrical energy to act contrary, which could start a Chain reaction.
[0030] The installation control units of the individual wind energy installations, which receive their setpoint values particularly here from the central control unit, individually control the wind energy installation and particularly the production of the three-phase electrical current , which must be fed, respectively. Thus, this production is adapted to the specific wind energy installation, and this installation control unit is consequently controlled individually. With respect to referencing, that is, particularly the identification of frequency and phase, each installation control unit of each wind energy installation can measure individually, and individually consider the measured values or input values, centrally recorded, at the point common coupling. However, said direct consideration of measured values in the individual installation control units is limited particularly to said referencing. In particular, the amount of active power and reactive power, which must be supplied, is not determined by each individual installation control unit, but is predetermined by said central control unit.
[0031] In simple terms, the central control unit is a calming influence, and provides the possibility of specifying important setpoint values, which are relevant to stability jointly and individually, while installation control units, individual, are functionally adapted to each individual wind energy installation, in order to particularly predetermine the specific currents that must be fed.
[0032] The individual and functional adaptation of the individual installation control units can preferably act on the operational control of the wind energy installation, and, for example, control a reduction of the energy produced by the wind by adjusting the rotor blades of the installation of wind power. wind energy. The adjustment of the rotor blades is generally known as the paddle step and is carried out individually by the wind power installation, particularly by its installation control unit. However, it is particularly the central control unit that predetermines and triggers the implementation of such a reduction.
[0033] The said division between a central control unit and individual installation control units, with the tasks described or the distribution of tasks described, can particularly prevent an internal control of a wind power installation from becoming unstable when the Common coupling point voltage is used as a current value, if it is not only used for referencing. Similarly, voltage controls, which use the reactive power of the wind power installation or wind farm as a manipulated variable, must be prevented from becoming unstable.
[0034] In addition or alternatively, the setpoint values are determined depending on at least one variable stability criterion, where the stability criterion particularly depends on a grid condition of the AC network at the common coupling point . For example, the stability criterion may depend on the amplitude of the mains voltage, or on a change or speed of change in the amplitude of the mains voltage, or on the frequency or change in frequency of the mains voltage. The stability criterion, as such, can be a deviation from the current voltage from the setpoint voltage, and depends on the voltage itself.
[0035] To cite a simple and illustrative example, the stability criterion could be a maximum permissible voltage deviation of, for example, 10% overvoltage, if the voltage frequency corresponds exactly to the setpoint value. If the frequency, however, is at least slightly higher than the setpoint frequency, or if the frequency rises in the network, the aforementioned permissible overvoltage could be reduced from 10% to 5%. Therefore, in this example, the stability criterion would be examined based on the voltage, that is, by examining the voltage level, and at the same time adjusted for the frequency dependence, that is, in an illustrative example, it would vary between 5% and 10% of the overvoltage.
[0036] Here, it is possible to consider the voltage at the common coupling point on the network side or the plant side. Voltages at the terminals of wind power installations can also be considered.
[0037] Depending on this stability criterion, at least one setpoint value is changed for wind power installations. In particular, a setpoint value can be changed for reactive power, active power, or both, respectively.
[0038] Alternatively, the reactive power and / or the active power that is fed by the wind power plant can also be taken as a basis for a stability criterion. In this case, the stability criterion may particularly be an existing specification in the form of a value or an area for the active power or the reactive power, which must be fed, together with compliance with the provision that this specification be examined. The active power fed can only be influenced to a certain extent, as the active power that can be fed depends on the prevailing wind. With a proposed stability criterion, the ratio between active power and reactive power may be relevant. For example, a certain adaptation of reactive power to active power may be relevant and taken as a basis.
[0039] Preferably, the determination of the setpoint value is based on a decomposition of the positive sequence component and the negative sequence component according to the symmetric component method, and the setpoint values are the values of the component positive sequence, that is, at least one reactive power of the respective wind energy installation, which must be powered, and related to the positive sequence component, and, in addition or alternatively, at least one output or clamping voltage of the respective wind power installation that is related to the positive sequence component, and in addition or alternatively at least one active power of the respective wind energy installation, which must be powered, and related to the positive sequence component, particularly a maximum active power that must be fed.
[0040] By predetermining the reactive power and / or the active power, which must be fed, an important value can be predetermined, which supports the network or influences the network stability. A respective reactive power can help to cancel or reduce a voltage drop in a long supply line or long line in the AC network.
[0041] The threatening instability due to a very low short-circuit current ratio, that is, due to a comparatively large connected load, can be canceled out by reducing the active power supplied. The predetermination of a maximum active power, which must be fed, is particularly provided because the prevailing wind permanently limits the active power, which must be fed, and thus a specific energy setpoint value, which exceeds such a limit, it cannot be implemented.
[0042] A combined and coordinated specification of the active power and the reactive power, which must be fed, is also advantageous, because an operating point, which is determined according to the active power and the reactive power, is particularly crucial for the stability of the wind farm during supply.
[0043] By taking the symmetric component method as a basis, an asymmetric three-phase system can also be considered. Ideally, the components of the negative sequence component are set to 0, that is, if the three-phase system is symmetrical.
[0044] According to one modality, it is proposed that a stability limit be previously calculated and stored for the control, particularly that it be stored in the central control unit as a characteristic field. For example, such a stability limit can be a characteristic field or, graphically shown, a characteristic, which is formed by several pairs of reactive and active power values. Consequently, the setpoint values for reactive power and active power are determined respectively in such a way, that an operating point, which is defined according to the reactive power and the active power, is positioned only on one side of said stability limit, that is, on the stable side.
[0045] Such a stability limit is particularly a characteristic of the connected network with respect to the network supply point. Consequently, it is preferably proposed to measure or otherwise identify the connected AC network in order to determine such a stability limit. When such a stability limit is determined and stored, a stable operating point can therefore be easily and / or reliably adjusted or monitored. Control of the wind farm, that is, power at the common coupling point, is therefore not required, or at least required in a lesser way to identify a threatening loss of stability due to suddenly identified dynamic processes, particularly at the common coupling point. Instead, it can be recognized at an early stage, in which (and, as the case may be, also when) the loss of stability would occur if countermeasures were not taken. Thus, possible abrupt countermeasures or radical countermeasures can be avoided, if an operating point is set safely. Preferably, such an operating point can be defined by the fed active power and the reactive fed power, and preferably the active power and the reactive power, which must be fed, are consequently limited and / or an operating point is adjusted accordingly. Preferably, such an operating point is adjusted or limited in such a way, that a safety distance between the operating point and the stability limit is established and maintained.
[0046] According to another modality, it is proposed that parameters of the mains supply point or parameters of the alternating current mains, according to measurements at the mains supply point, be compared with respect to the mains supply point, in accordance with in order to evaluate the characteristics of the alternating current network. In particular, the voltage identified at the mains supply point and / or the current identified at the mains supply point are used. Here, a parameter can be a network sensitivity to feed values. Such sensitivity is a change in voltage at the common coupling point with respect to a change in the powered power. In particular, it can be calculated from the sum of the change in voltage depending on the change in the active fed power and the change in voltage depending on the change in the reactive fed power. In other words, the sensitivity is calculated here from a partial derivative of the voltage according to the active power, on the one hand, and the reactive power, on the other hand. Said sensitivity, which is also referred to as network sensitivity, and which refers to the common coupling point, possibly also serves to identify a threatening loss of stability, or at least a weakening of network stability. In addition or alternatively, it is proposed to use this for an assessment of the quality, and particularly the stability of the operating point of the wind farm or the operating point of the wind power installation. Based on this, it is possible, if required, to take corrective action.
[0047] Preferably, it is proposed that network sensitivities are recorded and stored during a network analysis, previously conducted, and that, in addition, network sensitivities for a current operating point are identified. A control, specification and / or change of at least one setpoint value is then carried out depending on the comparison of the current network sensitivities with the previously registered network sensitivities. In particular, a setpoint value for the active power, which must be fed, is reduced if the comparison reveals that a deviation exceeds a predetermined limit value. Network sensitivities are the network responses to changes, particularly changes in food. Here, particularly a consideration of a network sensitivity is considered to be a response to a change in the fed active power, and a network sensitivity is considered to be a response to a change in the reactive fed power. These two network sensitivities can also be combined or considered together. Such a network sensitivity is a network characteristic and can therefore be previously registered and stored. It can help to identify instabilities at an early stage and to prevent them. In particular, a high network sensitivity means that the network is very strong, that is, that it is very sensitive and already responds to small changes. The control can therefore be adjusted as proposed according to a modality.
[0048] In addition, it should be noted that conditions can also change in the network, and limit conditions can have an impact on network sensitivity. By comparing the network sensitivities currently collected with the respective network sensitivities previously determined, it is possible to identify whether the network is still behaving in the manner previously determined or whether divergent behavior should be expected. In the latter case, special care may be necessary, as the control specifications could no longer be sufficient, or at least no longer optimally adapted to the network. For this case, the reduction of the active powered power can be the first protection measure. In particular, this can help to increase the distance between the operating point and the stability limit.
[0049] According to another modality, a sudden change or a change in one or two steps of a setpoint value for the reactive power, which must be fed, and / or for the active power, which must be fed , is proposed. This results in a major change with a consequently strong impact. In addition, a gradual change can also lead to the fact that a change is required in less cases, particularly that the active power and / or the reactive power, which must be fed, is not required to be continuously changed. Preferably, such a sudden or gradual change is made with a predetermined delay.
[0050] According to a modality, it is also proposed, based on a response of the network voltage, at the common coupling point, to such a sudden change, to determine a current network sensitivity. Here, the network sensitivity can be obtained by generating a difference, that is, by detecting the voltage as well as the active power or reactive power, suddenly changed, in an instant before the sudden change, and in an instant after the sudden change , and by placing the said two differences in relation to each other.
[0051] According to one modality, it is additionally proposed that a hysteresis controller be used to predetermine the setpoint values. A hysteresis controller is a controller whose output, that is, the manipulated variable (such as, in this case, the specification of the setpoint values), is not directly and clearly related to a respective input value, but also depends on of previous values. If a voltage forms the input of the controller, which in this case is used merely as a general example, and a reactive power forms the output of the controller, an increase in the voltage beyond its setpoint value can, for example, lead to an increase in reactive power. If the voltage returns to its setpoint value, or at least to the area, the reactive power can then, at least temporarily, maintain its value. Similarly, a proposed hysteresis controller may include a delay, so that, using the same illustrative example, an excess voltage does not immediately lead to a response from the controller, but only after a certain period of time. However, if an excess voltage no longer exists before this time lapse, there is no response at the controller output. In particular, a hysteresis controller is also a non-linear controller. As a purely precautionary measure, it is noted that a controller, whose transmission behavior is amplitude dependent, is a non-linear controller.
[0052] In addition or alternatively, it is proposed that the method for controlling a wind farm is characterized by the fact that a change of at least one of the setpoint values is made if a status parameter in the grid meets a specific criterion, and if a predetermined downtime has elapsed and the predetermined criterion remains satisfied. This particularly refers to the mains voltage at the common coupling point, and here, the satisfaction or fulfillment of the predetermined criterion may exceed or fall below the predetermined limit value or other predetermined limit value or exceed the value thereof. Another criterion that can be considered is that the relevant value, particularly the line voltage, is outside the tolerance band.
[0053] Preferably, it is proposed that, when specifying the setpoint values, the impedance of at least one supply line from a wind power installation to the common coupling point is taken into account, in order to take into account a voltage drop to be expected in the supply line. Here, in particular, a line impedance to the common coupling point in common can be considered, even if it is positioned away from the wind farm. In particular, in the aforementioned case, the said impedance from the installation of wind energy to the point of common coupling can be similar for many wind energy installations in the plant, and simply be taken as identical. The setpoint values of the wind power installation, that is, particularly for the reactive power and active power, which must be supplied, and thus for the currents which must be supplied, are preferably based on a virtual voltage in the installation. wind energy. Preferably, an output voltage as a virtual voltage is taken here as a base, which, due to a voltage drop, is caused by, or should be expected because of, the effective impedance from the supply line to the coupling point ordinary.
[0054] The load flow calculation, described below, is used to analyze stationary operating conditions of power supply systems. The underlying basis is the representation (figure 9) of the respective network through its Z impedances or its Y admittances (complex conductances).
Fig. 9
[0055] Classical network analysis determines the network through Ohm's Law with the following system of linear equations in matrix notation, which describes the correlation for n nodes.
that is,: (system of linear equations).
[0056] The goal is to determine voltages at each of the network nodes (→ voltage maintenance).
[0057] As the currents in the networks are unknown, but the (planned) supplies and electrical outages are known, the currents are expressed as outputs.

[0058] Representing the network equations through output results in the formation of a system of non-linear equations.

[0059] This system of non-linear equations is solved numerically (usually by Newton's method). When solving the system of equations numerically, it must be linearized. This is done by the partial derivatives of the matrix elements based on the unknown, more specifically still, amplitude (U2 ... Un) and the angle (δ2 ... δN) of the node voltages here.
[0060] The matrix with partial derivatives is called a Jacobian matrix. In order to solve the system of equations, it must be reversible, that is, regular.

[0061] The invention will be described in more detail below by modalities as examples with reference to the attached figures.
[0062] Figure 1 shows a wind power installation in a perspective view.
[0063] Figure 2 shows a schematic view of a wind power installation that is connected to a grid, based on a voltage control system (VCS).
[0064] Figure 3 shows a schematic view of a circuit arrangement of a voltage-controlled supply of a wind power installation in an alternating current network.
[0065] Figure 4 shows a schematic view of two wind energy installations connected to a grid over a common coupling point.
[0066] Figure 5 illustrates parameters that can influence the sensitivity of a wind energy installation connected to a grid.
[0067] Figure 6 shows a diagram analyzing the network behavior at the common coupling point as voltage courses depending on the reactive power fed and active power fed.
[0068] Figure 7 shows a sensitivity as a voltage change caused by changes in active power depending on reactive power and active power fed and standardized.
[0069] Figure 8 shows a sensitivity as a voltage change caused by a change in reactive power depending on the standardized reactive power and active power.
[0070] Figure 9 shows an illustration of generalized network.
[0071] Figure 10 shows a schematic view of a control structure for a wind farm including a central control unit and an installation control unit as an example.
[0072] Figure 11 shows a schematic view of the structure of the central control unit shown in figure 10.
[0073] Figure 12 shows a schematic view of a sub-control block shown in the central control unit of figure 11.
[0074] Figure 13 shows a schematic view of an installation control unit that is also shown in figure 10.
[0075] Below, identical reference signs for similar, but not identical, elements can be provided, or they can also be provided for elements that are only illustrated schematically or symbolically, and that may have different details, but that are not relevant to explanation.
[0076] Figure 1 shows the installation of wind power 100 with tower 102 and gondola 104. Rotor 106 with three rotor blades 108 and rotator 110 is positioned on gondola 104. Rotor 106 is placed in operation by the wind in a rotary movement, thus activating a generator in the gondola 104.
[0077] Figure 2 shows a schematic view of a wind power installation 1, connected to the electrical supply network 4 over the common coupling point 2. The electrical supply network 4 is simply referred to as a grid 4 or network (4), in which these terms are used synonymously.
[0078] The wind energy installation 1 comprises generator 6, which is driven by the wind, thus producing electrical energy. One of the modes of generator 6 is a synchronous generator 6, multiphase, electrically excited, with 2 three-phase systems with star-shaped wires, which is illustrated by means of the two star symbols in generator 6 of figure 2. The alternating current generated, more specifically, the six-phase alternating current in the example mentioned, is rectified by rectifier 8, and transmitted as direct current through the respective direct current line 10, which can comprise several individual lines, from the gondola 12 down in the tower 14 to the inverter 16. The inverter 16 produces alternating current from the direct current, more specifically in the example shown, a three-phase alternating current to be fed to the grid 4. For this purpose, the alternating current generated by the inverter 16 is graduated upwards by means of transformer 18 in order to be fed to the mains 4 at the common coupling point 2. Transformer 18, illustrated, uses a delta star connection, more speci and, firstly, a star connection and, secondly, a delta connection, which is illustrated here merely as an example of a modality. The supply to the grid 4 may also include, in addition to the active power supply P, the supply of the reactive power Q, which is illustrated by the arrow 20. For the specific supply, the inverter 16 is controlled by the respective control unit 22, in which control unit 22 can be structurally combined with inverter 16. Figure 2 is to illustrate the basic construction, and the specific arrangement of the individual elements can be chosen differently than the one illustrated here. For example, transformer 18 can be provided outside tower 14.
[0079] In particular, the control unit 22 controls the inverter 16 so that the manner of supply to the grid is controlled. The tasks are thus carried out, in order to adjust the current that must be fed to the situation in network 4, in particular the frequency, phase and amplitude of the voltage in the network. In addition, the control unit 22 is designed to control the portion of the active power P and the reactive power Q of the energy that is currently fed to network 4. Here, measurements are made on network 4, in particular at the common coupling point 2 , and are evaluated accordingly. Among other factors, the current voltage in network 4 is measured, in particular in the form of the actual effective value of the voltage, and compared with the standard value for the voltage, more specifically the standard value ADJUSTED.
[0080] Consequently, the illustrated system, and in particular the inverter 16 with control unit 22, form a voltage control system, which is abbreviated as VCS.
[0081] To control the generator of the wind energy installation, the energy control block 24 and the energy evaluation block 26 are provided in the area of the gondola. In the example of the illustrated embodiment, the energy control block 24 particularly controls the excitation, more specifically the excitation current of the synchronous generator, separately excited. The energy evaluation block 26 evaluates the energy conducted to the rectifier 8, and compares it with the output energy released by the rectifier 8 over the direct current line 10 to the inverter 16. The result of this evaluation is transmitted to the block power control 24.
[0082] Figure 2 also illustrates that the system shown must have a voltage control system for intelligent power in order to operate the wind energy installation as steadily as possible, in particular close to the stability limit.
[0083] Figure 3 illustrates the connection of the wind power installation 1 ', the so-called weak network 4'. A weak network here refers to a network with a high impedance. This is illustrated in figure 3 by means of 5 'serial impedance. In addition, said 5 'serial impedance was provided in a test structure that corresponds to the structure in figure 3, and which was used to examine the behavior of the wind power installation 1' in the weak grid 4 '.
[0084] The structure of figure 3 assumes generator 6 ', which is driven by the wind and provided as a synchronous generator. The electrical energy generated from the generator 6 'is rectified in the rectifier 8', and supplied to the inverter 16 'on the input side in a direct current connection with intermediate circuit capacitor 28'. The structure shown compares direct current line 10 'with the direct current line of inverter 16', on the input side, to simplify the illustration. The direct current line on the input side can, more specifically, be electrically identical to an intermediate circuit, or an amplification converter is provided on the input side, which is not explained in detail here. The rectifier 8 'and the inverter 16' can also be physically separated from each other, as already explained in figure 2 with respect to the rectifier 8 and the inverter 16.
[0085] Finally, exciter control 24 'is provided, which can be supplied with energy from the direct current line that is presented by the intermediate circuit capacitor 28'. Said exciter control 24 'controls the excitation current of the separately excited generator 6' and basically corresponds to the energy control block 24 of figure 2.
[0086] The inverter 16 'can supply active power P and / or reactive power Q. Figure 3 verifies the voltage of the inverter 16' on the output side as the voltage of the VWEC wind power installation. For the supply, it is graduated upwards by the transformer 18, and then fed to the grid 4 'at the common coupling point 2'. Here, network 4 'also comprises network transformer 30'. The current network starting after the network transformer 30 'is specified with the reference signal 4 ". The voltage at the common coupling point 2' is referred to as the network voltage VRede.
[0087] To illustrate the weak network, the serial impedance 5 'is shown in front of the common coupling point 2'. Said serial impedance 5 'exists only in this test structure or illustration structure, and indicates the network impedance. Therefore, the point shown directly after transformer 18 'can also be referred to as the common 2 "coupling point. This differentiation between these two network connection points 2' and 2 '' only results from this use of serial impedance 5 ', and usually does not exist in this form in real networks.
[0088] Figure 4 shows another illustrative and schematic example, according to which two wind power installations 1 are connected to a supply network 4. Each wind power installation 1 is basically designed as explained in figure 2, more specifically with generator 6, rectifier 8 and direct current line 10, which more specifically comprises at least two individual lines, more specifically for positive current and negative current, which also applies to direct current line 10 of the figure 2. In addition, wind power installation 1 comprises inverter 16 and transformer 18. Access line 32 leads from each of the two wind power installations 1 to one, or o, the common coupling point 2 'on the side of the wind power installation. Thus, these two wind power installations 1 shown as examples, which may be representative for a wind power plant with many wind power installations, feed their jointly generated energy at this common 2 'coupling point on the side of the wind power installation. The energy supplied P and the reactive power fed Q, if present, are then conducted to the connection point 2 'on the network side, and fed to the electrical supply network 4.
[0089] The connection between the common coupling point 2 'on the side of the wind power installation and the connection point 2' 'on the network side cannot be ignored, and consequently, the VWP voltage is obtained on the side of the power installation wind at the common coupling point 2 'on the side of the wind power installation, while the VRede voltage is obtained at the connection point 2' 'on the network side.
[0090] The VWP voltage on the side of the wind power installation is determined and evaluated in evaluation block 34 for the control. The evaluation is initially carried out in such a way that the measured values are recorded with measurement block 36. The measurement results are transmitted, among other things, to the stability control block 38, which can also be referred to as the measurement block. SVCS (Stability Voltage Control System). The stability control block 38 calculates a default value QAadjusted for the reactive power that must be provided. This reactive power that must be obtained is then transferred as the respective default value for both wind power installations 1, and consequently would be transferred to all wind power installations in an amount. This standard value can be transferred as an absolute value, in particular if the wind power installations 1 are the same size and are subject to the same wind conditions. However, it can also be provided as a standard value, such as a percentage value, which refers to the properties of the respective wind power installation, for example, as the nominal capacity of the relevant wind power installation.
[0091] In addition, measurement block 36 transmits the values to observer block 40, which calculates other conditions based on the determined measurement values, such as the active powered power or the reactive powered power, and transmits its results to the system model block 42. Observer block 40 can also obtain or derive information on energy demand, if necessary.
[0092] The system model of the system model block 42 is used to determine a maximum active power Pmax, to be supplied, and to supply it to wind power installations 1. This maximum active power, to be supplied, can be provided as an absolute value or a relative value. It is noted that the illustration of evaluation block 34 is to explain the structure. In general, it is not necessary for the evaluation block 34 to be physically designed as an independent device.
[0093] The preset reactive power Qadjusted and the maximum active power Pmax are then transferred to the FACTS control block 44 of each wind power installation 1. The term "FACTS" is also used in German and is an abbreviation for "Flexible AC Transmission System" (Flexible AC Transmission System). The FACTS 44 control block then implements the default values and, consequently, controls the inverter 16, and it can also consider measured values from conditions of the wind power installation.
[0094] In particular, but not exclusively, evaluation block 34 can provide standards relevant to stability for a stable supply to the grid 4. In particular, an operating point can be adjusted, which is favorable with respect to the amount of energy to be supplied. be fed or with respect to the amount of energy and stability. In particular, an operating point with a stability reserve can be determined here. In this case, the stability control block 38 can achieve a stability reserve with respect to the reactive power that must be supplied by means of a respective pattern of the adjusted Q reactive power.
[0095] Figure 5 illustrates the sensitivity of a wind energy installation, connected to a grid, and the corresponding influencing factors. The network block 50 of figure 5 is specified representatively for the network behavior, more specifically at the common coupling point. The network block 50 illustrates that the network can react to influences due to a change in voltage. All influences are illustrated here as changes in active power ΔP and changes in reactive power ΔQ. The active power block 52 considers influences of energy changes, and the reactive power block 54 considers influences of changes in reactive power. The active power block 52 shows a partial voltage derivation based on the active power, and, correspondingly, the reactive power block 54 shows a partial voltage derivation based on the reactive power. This is a possibility to consider the respective dynamics of the network behavior, that is, the network sensitivity, more specifically reactions to changes in active power and reactive power, by means of respective partial derivations, the results of which are added to the block of sum 56. The grid block 50, together with the sum block 56, thus considers a dependence on the grid voltage at the common coupling point of two variables, more specifically the active power and the reactive power. Dependency is considered here by partial derivations.
[0096] Changes in active power result in particular from changes in wind speed Δ vw, which impacts wind power installation block 58. This wind power installation block 58 illustrates the influence of change in wind speed Δ vw in the change in active power Δ p, in which the control of the wind energy installation is also to be considered, and is considered by this block 58.
[0097] The change in reactive power ΔQ may also depend on the installation of wind energy, or at least the control of the installation of wind energy; however, it generally depends on other contexts that are independent of wind speed. Its change is illustrated by control block 60. For explanatory purposes, this control block 60 is divided into reactive power pattern block 62 and FACTS block 64. Control block 60, and thus the pattern block of reactive power. reactive power 62, are initially dependent on a voltage deviation Δ v, more specifically at the common coupling point, minus a predetermined voltage deviation Δ VSET. Based on this resulting voltage deviation, the reactive power pattern block 62 determines the reactive power, which must be fed, or, depending on a voltage change, a predetermined change in the reactive power to be fed. This is transmitted to the FACTS 64 block, which consequently implements the reactive power supply or the change in the reactive power supply.
[0098] The wind power installation block 58 and the control block 60 can also be understood as a function of transferring the respective input value, and the reactive power standard block 62 and the FACTS block 64 can each one, be understood as individual transfer functions that are interconnected in the control block 60
[0099] Figure 6 shows a voltage dependence for a modality at the common coupling point based on reactive power fed Q and active power fed P. The reactive power Q is standardized for the SSC short-circuit energy of the grid at the point of common coupling, examined, and traced on the abscissa. The P energy is also standardized to the SSC short-circuit energy of the same common coupling point, and is established in the ordinate. The VPCC voltage is the voltage at the common coupling point, standardized for the nominal voltage VN. This standardized voltage at the common coupling point is plotted as a graph for different values respectively and depending on the standardized reactive power Q and the standardized active power P. Consequently, the graph or characteristic with the value 1 is a characteristic representing the power values reactive and active power, required to obtain rated voltage.
[00100] For example, the nominal voltage is obtained if 10% of the reactive power Q and 50% of the active power P are supplied with respect to the short-circuit energy SSC.
[00101] The graph in figure 6 shows characteristics of a common coupling point of a network with high impedance, at least with respect to this common coupling point.
[00102] Usually, for the common coupling point, illustrated, of the network example, a supply would be carried out within a standard operating range 200. The supply would thus be carried out with an active power P of approximately 10% of the short-circuit energy - SSC circuit, with a supply of approximately 5% of the reactive power of the SSC short-circuit energy. Upon the idealized assumption that the active power fed P corresponds to the nominal power or connected load of the generator or to the sum of the generators connected to the common coupling point, the supply of 10% of SSC short-circuit energy would mean that the connected load PGen is 10% of the SSC short-circuit energy. The short-circuit current ratio Scr = SSC / PGen is therefore approximately 10. This corresponds to approximately the center of the standard operating range 200 shown. Figure 6 shows other short-circuit current ratios Scr as short dashes for orientation, more specifically for values for Scr of 10; 6; 4; 2 and 1.5.
[00103] According to the invention, however, it is proposed to supply significantly more active power P, more specifically within the range of 60% to 70% of the SSC short-circuit energy. Consequently, a supply of 20% to 30% of the reactive power Q related to the SSC short-circuit energy must be provided so that this keeps the voltage at the common coupling point within the range of 100% to 110% of the rated voltage. As a precautionary measure, it is noted that supplying 110% of the rated voltage at the common coupling point does not mean that an increased voltage of 110% can be measured on the consumer side. First, there is usually a considerable section of network between the common coupling point and the first relevant consumer. Second, step transformers can be provided in the network, which can provide a balance to a certain extent. The measures to be taken in relation to this, which depend on the individual network, including consumer and generator and several other structural conditions, cannot be addressed in this order. A specialist is usually familiar with the required measures.
[00104] This proposed section is shown in figure 6 as an increasing operating range 210. This increasing operating range has a Scr short-circuit current ratio of approximately 1.5. No noteworthy generator has yet been connected to the grid with such a short-circuit current ratio.
[00105] The illustration in figure 6 is the result of a network analysis of the underlying network with respect to the relevant common coupling point. For this purpose, as explained above, the relevant elements in the network were analyzed and determined respectively by resolution of the Jacobian matrix. This results in the present illustration of figure 6, according to which, in simple terms, the characteristics for the right side, that is, with the highest reactive power fed Q, also reflect increased voltages at the common coupling point. With decreasing reactive power Q, that is, to the left side, the voltage at the common coupling point decreases. However, the reactive power Q cannot decrease arbitrarily, and with too low (already negative) reactive power Q, the Jacobian matrix becomes singular, according to the associated active power P, that is, impossible to solve in mathematical terms. A singular Jacobian matrix means that there is an unstable condition. This results in stability limit 202, which is consequently shown on the left side of the illustration in figure 6. The area to the left of stability limit 202, which has a higher active power P and / or a lower reactive power Q, respectively , is the unstable area 204. As a purely precautionary measure, it is noted that the stability limit 202 does not coincide with a single characteristic of a voltage value at the common coupling point, but, on the contrary, it appears to cut off the plurality of characteristics . However, a plurality of characteristics cannot be cut, as there are no values, and thus no plurality of characteristics, beyond the stability limit 202.
[00106] The preferable operating range, more specifically the increasing operating range 210, has a smaller distance to the stability limit 202 than the standard operating range 200. However, it should be noted that specific considerations or analyzes have not been made with respect to to the network characteristics, as shown in figure 6. In particular, the distance to the stability limit, as shown in figure 6 as the stability limit 202, has not been known, at least not in the quality and quantity shown in figure 6. On the contrary, the installation of large power installations is oriented towards the criterion of the short-circuit current ratio, and this is as large as possible, preferably above (or even significantly above) 10. Small generators, such as installations of wind power, have so far usually been connected to strong networks that were easily able to handle the connection of another wind power installation. As a result, the connection was made, either intentionally or unintentionally, with a high SSC short-circuit current ratio.
[00107] The proposed solution analyzes precisely the network with respect to the common coupling point provided, in particular by quantitatively incorporating contexts, as shown in figure 6 - and preferably in figures 7 and 8, which will be explained below. In particular, such an analysis is carried out by repeated training and solving the Jacobian matrix for several points. Based on such a network analysis, a stability limit according to stability limit 202 can be determined, and a desired operating range according to increasing operating range 210 in figure 6 can be chosen.
[00108] In addition, it is proposed that the wind energy installation be controlled in the sense of a closed control link, as shown in particular in figure 2 and figure 4. In figure 2, the control link basically comprises the inverter 16, the transformer 18 and the control unit 22, take measured values at the common coupling point 2 and control the inverter 16 in order to obtain the fed active power P and the reactive power Q according to arrow 20. The control it can also impact on the control of the wind energy installation in the generator area 6; however, the control link described, comprising inverter 16, transformer 18 and control unit 22, requires no mechanical elements and is able to react very quickly. For this, the knowledge of the network characteristics at the common coupling point, that is, the common coupling point 2 according to figure 2, can also be considered, in particular in the control unit 22. Thus, a fast control can be implemented, which recognizes the network behavior at the common coupling point, particularly the stability limit. This makes it possible to operate the wind power installation or wind farm - and other generators, if applicable - within a desired operating range, such as the increasing operating range 210 in figure 6, while ensuring high stability and high safety.
[00109] Figures 7 and 8 show the voltage sensitivity depending on reactive power Q and active power P. Figures 7 and 8 thus use the same values in the abscissa and ordinate, more specifically reactive power standardized in the abscissa and power active standardized in ordinate.
[00110] The voltage sensitivity shown is the change in voltage with the change in active power according to figure 7 or the change in voltage with reactive power according to figure 8. In other words, the partial derivation of the voltage at the common coupling point according to the active power in figure 7 and the partial derivation of the voltage according to the reactive power in figure 8 are illustrated. Figure 7 thus shows the behavior of the active power block 52 of figure 5. Figure 8 shows the behavior of the reactive power block 54 of figure 5, in which in both cases, the illustration is shown depending on the operating points. , which are determined by the reactive power currently fed Q and the active power fed P. The values of the respective characteristics refer to a common coupling point with a short-circuit energy SSC = 3.73 MVA, to which two power installations wind turbines with a nominal power of 2 MW each must be connected, as an example. Thus, this test arrangement allows for the performance of tests with a short-circuit current ratio of as small as 1. However, for the tests carried out, the respective current power of the test wind farm was used as a basis, and determined as the connected load of the target wind farm, that is, the (fictitious) wind farm that must be examined.
[00111] With respect to the present modality, that is, the example configuration, the change in the standardized voltage, related to a change in energy P in MW or a change in reactive power Q in MVAr, is described. Figures 7 and 8 also illustrate the desired one, that is, the increasing operating range 210. Therefore, the voltage sensitivity with respect to changes in active power according to figure 7 is approximately -0.2 to -0, 4. The voltage sensitivity in the increasing operating range 210 with respect to changes in reactive power according to figure 8 is approximately 0.3 to 0.5. Therefore, it is proposed that, when designing the wind energy installation, it is connected to the concrete common coupling point, to incorporate and consider this voltage sensitivity in the control with respect to changes in the active power, as shown in the example in the figure 7 and / or with respect to changes in reactive power, as shown in the example in figure 8. In particular, these values should also be considered in the control, and preferably also in the design of the control. Preferably, a controller amplification is chosen depending on the sensitivity, in particular the voltage sensitivity.
[00112] In particular, it is proposed to consider these values in the closed link, as schematically performed by the elements shown in figure 2, that is, the inverter 16, the transformer 18 and the control unit 22. Here, the transformer 18 is less important ; however, it must often be present and is required to supply a respectively high voltage at the common coupling point 2. In particular, findings regarding the voltage sensitivity in the control unit 22 are considered. In this way, with the knowledge of these values, it is possible to design and implement a customized control for the concrete common coupling point. This makes it possible to reduce the previously high values of the short-circuit current ratio to 10 and even higher, and to provide low values, such as 1.5, for the short-circuit current ratio, and thus operate the installation. of wind energy in the increasing operating range 210, which is shown in figures 6 to 8.
[00113] The invention thus proposes in particular that a wind power installation, and finally also a wind power plant, are no longer connected according to the old principle of parallel grid operation, assuming that the grid capacity is sufficient, but, on the contrary, that the connection point is specifically analyzed and that the results are already considered before the operation, and that a customized wind energy installation or a customized wind energy plant is then connected there. Preferably, the control and the operating range that must be chosen, in particular with respect to reactive power Q and active power P to be fed, are customized and arranged closer to a stability limit that was previously done by specialists. In doing so, the benefits of a wind power installation are used in a targeted manner, more specifically to respond quickly and intentionally to changes, in particular changes in grid conditions. This is to avoid an excessively large size of the grid, in particular the specific common coupling point, at least for the connection of wind power installations to the grid. Nevertheless, it is possible to maintain and even improve stability, if the control or regulator recognizes the characteristics of the common coupling point or the network very well in relation to the common coupling point, and if it observes the network conditions.
[00114] As a purely precautionary measure, it is highlighted that a regulator is basically understood as a closed link with feedback, in which a control basically refers to an open "link", that is, the situation without feedback. However, a control block, which implements a control method, can be used in a control link. With respect to the example in figure 2, this means that the control unit 22 is a control to the extent that it comprises a certain control function or transfer function, which can also be non-linear and / or volatile, and / or refer to various sizes. However, this control unit is used on the link shown in figure 2, which basically comprises, in addition to the control unit 22, the inverter 16, the transformer 18 and finally the measurement unit at the common coupling point 2 with a control unit. comparison 23. The control unit 22 controls the inverter and is therefore integrated into the closed link, forming part of a control.
[00115] Figure 10 shows a schematic view of a wind farm 200, comprising in this example 3 wind energy installations 202, which are indicated by the symbol WEC. Other control elements are attached to each wind power installation 202, which is indicated by a dashed box. Such a dashed box is indicated for each wind energy installation 202, while the combined elements are shown in only one wind energy installation, that is, the wind energy installation 202 shown in figure 10 above. Most of these elements can also be locally arranged in the wind power installation, for example, in the tower of the wind power installation.
[00116] Insofar as, until now, the control structures of figures 10 to 13 are different from the statements mentioned above with respect to figure 2 and figure 4, the aforementioned structures mentioned in figures 2 to 4 are useful as complementary explanations and useful as general explanations.
[00117] The wind farm 200 is connected to the AC power grid 206 through common coupling point 204, which is also referred to as PCC. The alternating current electric network 206, and consequently also the common coupling point 204, are of 3 phases, which is not highlighted, to simplify the matter, in figure 10, however.
[00118] At, or behind, the common coupling point 204, a network voltage UN is measured, comprising the 3 voltages ui, U2 and U3. In addition, the current fed IN is identified at, or just behind, the common coupling point 204, containing the individual current components ii, i2 and i3. These measured values for the grid voltage UN and the current fed IN are identified continuously, and fed to the central control unit 208. The central control unit 208 is provided as a central control unit for the entire wind farm 200. In addition , the central control unit 208 receives some default values at its standard input 2i0, that is, a setpoint value for the positive sequence component voltage UW + EC, SOLL, which should be used as the setpoint voltage value of stapling of all wind power installations, and considers an expected voltage drop in the line between wind power installation and common coupling point. Alternatively, such a value can also be fed here for each of the wind power installations 202. In addition, controller parameters are predetermined, that is, a difference voltage, ΔUt as well as the first and second timer times tA and tB , and an increment of reactive powerΔQl // EC. In addition, an effective ZPCC-WEC impedance and, in addition, 2 characteristic fields are predetermined. The effective impedance ZPCC-WEC describes the supply line impedance between the wind power installation 202 and the common coupling point 204. This value can be predetermined together for each connection line between the wind power installation 202 and the point common coupling 204, respectively, or particularly with large deviations, for each individual wind energy installation within the wind power plant.
[00ii9] The said impedance serves to compensate for a voltage drop in the respective lines, which is also referred to as line loss compensation, which is only virtually possible due to the large degree of parallel connection of the individual wind power installations in a power plant. . This consideration is made particularly in the sense of a consideration that is effective, on average. For this reason, it is preferably proposed to consider only a single impedance for the entire plant.
[00120] The central control unit 208 then passes 3 setpoint values to the wind power installation 202, that is, the reactive power of the positive sequence component, which must be supplied, QW + EC, the voltage of the component positive sequence UW + EC, which must be set at the output of the wind power installation, and a maximum value for the active power of the positive sequence component, which must be supplied, PM + AX WEC.
[00121] These 3 setpoint values are basically predetermined for each wind power installation 202, which is only suggested in figure 10.
[00122] These default values are then fed to installation control unit 212, in which the cosine current component of the positive sequence component I + C is calculated based on the predetermined maximum active power. For example, that component can be calculated using the following formula:

[00123] In correspondence with the aforementioned, a current sine component of the positive sequence component of the + S IWEC wind power installation is calculated using the formula:

[00124] Installation control unit 212 is explained in detail below in connection with figure 13. Installation control unit 212 then outputs the setpoint values for currents i1 ', i2' and i3 'that should be adjusted. These currents are fed to control block 214 to implement pulse width modulation, and said control block is also indicated as PWM in figure 10. PWM 214 then controls inverter 216, which receives its input energy at the intermediate circuit 218. The inverter 216 therefore operates on a voltage basis, and is also referred to by experts as "voltage source control" (VSC).
[00125] As a result, inverter 216 emits a current of the positive sequence component, IW + EC, which feeds the common common coupling point 204 through transformer 220 and supply line 222 within the plant. Common coupling point 204 shows a schematic view of other connections 224 for connecting other wind power installations 202.
[00126] For internal control of the wind power installation, particularly through installation control unit 212, the 3 voltages u1 ', u2' and u3 'are identified at output 226 of the wind power installation or inverter 216, and fed to the status observer 228, which is also indicated as SO1 in figure 10. Based on this, the status observer 228 determines a phase angle ^ u, which is fed to the installation control unit 212. The functionality of the status observer state 228 is described in detail in German patent application DE 10 2009 031 017 A1. In particular, state observer 228 is described there in figure 4. There, the voltages u1, u2 and u3 are specified as input values, and the phase angles ^ '^ 2unD (p3 as output values. The content of the said German patent application must therefore also be seen as the content of this application. In any case, the description of the state observer according to figure 4 of the German patent application must be part of this application. US 13 / 381,302 exists together with the German patent application.
[00127] Consequently, the central control unit 208 measures the voltages and the total current at the connection point 204 of the wind power plant.
[00128] The structure of the central control unit 208 is illustrated in figure 11. Consequently, the voltages u1, u2 and u3 measured at the common coupling point 204 and the currents i1, i2, and i3 measured there are also input measurements for the central control unit 208. The said voltages and currents are instantaneous values and are fed to the calculation block 230, which is also indicated as Unit 1.1 in figure 11.
[00129] Based on the currents and voltages fed, which are measured at the common coupling point 204, for example, with a sampling rate of 5 KHz, the calculation block 230 calculates the active and reactive powers fed P and Q, as well such as the current I and the voltage of the positive sequence component UP + CC. The decomposition of a 3-phase system (such as, in this case, a 3-phase voltage according to the symmetric component method) into a positive sequence component and a negative sequence component is basically known. The calculation in this calculation block 230 can, for example, be carried out as described in German patent application 10 2011 084 9 10.6, in connection with figure 3.
[00130] The estimation block 232, which is also indicated as unit 1.2 in figure 11, calculates or estimates, based on the values measured in the common coupling point 204 or values derived from them, the voltage that should be expected in the wind power installation fasteners, that is, the positive sequence component voltage UW + EC in the wind energy installation fasteners, particularly at output 226 of inverter 216. For this purpose, the positive sequence component voltage at the coupling point common UPCC, current I and phase angle Φ = arctan (^ / p) are used. In addition, the effective impedance between the common coupling point and the ZPCC-WEC wind power installation is required, which has been previously determined, and is fed here at central control unit 208 and estimate block 232. Basically, a voltage drop in the connection line between the wind power installation to the common coupling point is considered. This voltage drop is considered or compensated for. The identified and calculated voltage of the positive sequence component in the UW + EC wind power installation is an estimate for an equivalent, that is, for an assumed virtual voltage.
[00131] Control block 234, also indicated in figure 11 as unit 1.3, is an important element of central control unit 208. Said control block 234 is explained in detail below in connection with figure 12. In any In this case, it receives the positive sequence component voltage of the wind power installation as an input value, UwEC, as well as several controller parameters, that is, ΔQl // EC'Δu <'TA' TB and the point value voltage adjustment of the UW + ECSOLL wind power installation.
[00132] Control block 234 supplies the voltage of the positive sequence component of the wind power installation UW + EC, basically slows down the value, and provides a setpoint value for the reactive power of the positive sequence component, which must be powered through the installation of wind power QW + EC. In addition, control block 234 provides timer2, which is required by sensitivity block 236, and passed to said sensitivity block. Sensitivity block 236 is also indicated as unit 1.4 in figure 11.
[00133] Sensitivity block 236 determines the network sensitivity based on the values calculated in calculation block 230 based on the measurements at the common coupling point. The calculation is conducted with the following formulas:

[00134] The difference that is taken as a basis for said calculation refers to values that belong to different time points, and consequently, those calculated values are taken as a basis, which result from the time interval of the value of timer2, particularly in an instant when timer2 has a value of 0, and in an instant when timer2 has its maximum value, which is described by the following formulas:

[00135] The value of timer2 = 0, therefore, describes the values that were registered or determined directly before timer2 was set or started.
[00136] Consequently, the block of sensitivity 236 provides the network sensitivities, that is, with respect to the change in active power or in reactive power, that is,

[00137] Finally, a characteristic field block 238 exists, which is also indicated as unit 1.5 in figure 11.
[00138] Said characteristic field block 238 receives the active power and the reactive power and the network sensitivity as input signals. In addition, characteristic fields are fed and stored there, that is, as a result of a network analysis, previously conducted. The characteristic field block 238 therefore contains the network sensitivity dUpcc Idp and dUpcc IdQ as values that were previously registered and stored in the characteristic fields, that is, in 2 characteristic fields, and as current values for the current operating point , which results from the current value of the active fed power and the current value of the reactive fed power. Here, the 2 network sensitivities are compared, respectively, that is, to one previously stored with the one currently registered, that is, dUpcc 1 dp from the network analysis with dUpcc 1 dp from the current operating point and dUpcc 1 dQ from the analysis of network with dUpcc 1 dQ of the current operating point.
[00139] Preferably, a stability limit is also stored here, and the distance from the current operating point to a stability limit is identified. If the current operating point falls below a predetermined distance to the stability limit, and / or if a marked deviation from the sensitivity to be expected, that is, the previously recorded network sensitivity from the currently identified network sensitivity, which is stored in the characteristic fields, the maximum active power PmaxWEC, which must be fed, is reduced. Said value is provided accordingly in the characteristic field block 238.
[00140] Control block 234 - Unit 1.3 - is described in detail in figure 12, also in the sense of a schematic flowchart. In step S1, the positive sequence component voltage of the wind power installation UW + EC is compared with a corresponding setpoint value, ie UW + ECSOLL. The voltage of the positive sequence component in the UW + EC wind power installation is the virtual voltage, which was determined by the estimation block 232 according to the voltage measured at the common coupling point and the consideration of the effective impedance. In said step S1, it is initially examined whether said virtual voltage UW + EC is in the tolerance band 240. Here, the tolerance band 240 is a band whose margins around the predetermined difference voltage ΔUt are over, or below, voltage setpoint value UW + ECSOLL.
[00141] If the voltage, for example, exceeds the tolerance band at time t1, a first timer1 is started.
[00142] Then, the time is measured, which passes to the point in time t2, when the voltage returns to tolerance band 240. A similar procedure is possible, if the voltage leaves the tolerance band underneath, as indicated in graph in step 1.
[00143] Logic step S2 describes the behavior of timer1. Steps S1 and S2 and other steps described below basically take place simultaneously, and can also take place simultaneously. Said steps S1 and S2 thus describe partial functions or partial processes or functionalities of control block 234.
[00144] Step S2 explains that timer1 increases until it exceeds the value tA. In the referred case in which the value is exceeded, timer1 is set to 0, and the acceleration link described in step S2 starts again. If the voltage in the tolerance band returns before timer1 has exceeded the tA value, timer1 is set to 0 again, and remains there until the voltage again leaves tolerance band 240. Nothing else is triggered.
[00145] However, if timer1 has exceeded the tA value, the predetermined reactive power is changed suddenly or by a step, which is explained in step S3. Therefore, a reactive power difference of the positive sequence component Δ ° -7EC is predetermined, if the uwEc - uwECSOII difference exceeds the Δ Ut value or falls below the -ΔUt value. Consequently, a reactive power value of difference of the positive sequence component Δ ° W- EC or a corresponding negative value - Δ ° W- EC is adjusted. The predetermined reactive power value of the positive sequence component for the ° W-EC wind power installation is then, based on its current value, changed by the difference value, that is, increased by one step, if the voltage has abandoned the tolerance band 240 up, or decreased by one step, if the voltage has left tolerance band 240 down. This is shown in the equation in step S4. Therefore, the value Δ ° W- EC is the step quantity.
[00146] By changing the reactive power of the wind energy installation by one step, a timer2 is additionally started. This is illustrated by step S5 for the example where the reactive power of the positive sequence component of the ° W- EC wind power installation is increased by step Δ ° W- EC. Correspondingly, the same applies to a decrease. Timer2 increases by one link until said increase in reactive power for one step is pending. If timer2 exceeds the comparative value tB, it is provided for timer2 so that it can still be used in sensitivity block 236. The link for timer2 is illustrated in step S6.
[00147] It is proposed to wait for timer2 by all means, before the reactive power can be changed again. Thus, during this period, the reactive power is not reduced by one step.
[00148] Control block 234 provides, among other things, the voltage setpoint value UW + ECSOLL and UW + ECSOLL is then used by wind power installations like UW + EC, respectively.
[00149] In addition, the reactive power of the positive sequence component of the wind power installation QW + EC, which must be adjusted and, if necessary, altered, is provided in a way that can be supplied, in total, by the central control unit 208, and passed to the respective installation control unit 212, as shown in figure 10.
[00150] The control block 234, therefore, indicates a special hysteresis downtime controller, which has the values Δut, TA • TB and ΔQvEC as parameters. Timers have the meaning and effect that an activation of the step to increase or decrease reactive power is only conducted if timer1 reaches the value tA. If the voltage returns to tolerance band 240 earlier, leaving or leaving the tolerance band, it has no impact on the control. However, if timer1 reaches the value tA, the increase or decrease of reactive power by one step is activated, and timer2 is started. It is then necessary to wait by all means until timer2 reaches the tB value.
[00151] Said hysteresis controller, which is described in control block 234, is intended to prevent, in combination with installation control unit 212, that the internal control of the wind energy installation from becoming unstable, if the voltage of the common coupling point is used as a current value. In addition, it must be prevented that voltage controls, which use the reactive power of the wind energy installation or the wind farm as a manipulated variable, from becoming unstable.
[00152] The control block 234, or unit 1.3, performs mathematical functions, which can also be used in different locations than in the central control unit 208 (the Central Unit 1), that is, in the installation control unit 212 of the individual wind power installations. Other input data, particularly measurement data, then leads to different findings, that is, different results.
[00153] Installation control unit 212, several of which are provided in a wind power plant, particularly performs some calculations, as explained in figure 13. The cosine component of the positive sequence + C component current of the wind power installation IWEC then enters said installation control unit 212. In addition, the voltage or virtual voltage of the positive sequence component of the wind power installation UW + EC enters, and the reactive power (which must be adjusted) of the positive sequence component of the wind power installation QW + EC. Said two values are conducted respectively through a delay element of the first order 242 or 244, and then lead to the sine component block 246. In the sine component block 246, the current sine component, which must be adjusted, of the positive sequence component of the + S IWEC wind power installation, is calculated according to the formula shown there, that is:

[00154] Based on the cosine component and the sine component of the current to be adjusted, the current amplitude of the current to be adjusted from the positive sequence component / ++ 'EC and its angle <p / wc is then calculated in total power block 248, as shown in block 248, that is, by the formula:

[00155] Finally, in the subsequent individual power block 250, the 3 individual phase currents, which must be adjusted, i1 ', i2' and i3 ', are calculated by the equations shown there, and the result is provided for the unit of installation control 212, and passed to the PWM block 214, according to figure 10. Consequently, the powers are calculated by the following equations:

[00156] Thus, the current components are determined by the installation control unit 212, individually for each wind power installation 202, based on the values that were centrally predetermined by the central control unit 208. In the example shown, the angle 0U it depends on the specific measurement at the output of the specific wind energy installation, and is therefore individualized for the wind energy installation. + C
[00157] In addition, the IWEC cosine portion results from the power control of the wind energy installation. First order delay elements 242 and 244 thus constitute filters. Said filters are parametrically adapted to the control block 234.
[00158] Therefore, the control of wind energy installation + C limits the power, and thus, if necessary, in more detail, the IWEC current for PMAX WEC value.

权利要求:
Claims (14)
[0001]
1. Method for controlling a wind power plant (200) comprising several wind power installations (202) to supply electrical energy, at a common coupling point (PCC) (204), to an alternating current electrical network (206), characterized because it comprises the following steps: - supplying a three-phase current at the common coupling point (204), - detecting a grid voltage (UN) at the common coupling point, - comparing the grid voltage (UN), which has been detected at the common coupling point (204), with at least a predetermined setpoint value, - determine setpoint values for wind power installations (202) based on the comparison made, so that a stability criterion at the common coupling point (204) it is observed, - where the stability criterion is dependent on the reactive power fed by the wind power plant (200), and / or the active power fed by the wind power plant, - transfer the determined values of ajus for the installation control units (212) of the individual wind energy installations (202), and - generate electric current (I1, I2, I3) in each of the wind energy installations (202) based on the predetermined values of set point for the purpose of common feeding at the common coupling point (204).
[0002]
2. Method according to claim 1, characterized by the fact that: - the current (IN) fed at the common coupling point (204) is detected, and is measured, particularly, at the common coupling point (204), - the detection of the supplied current (IN), the detection of the mains voltage (UN) at the common coupling point (204), the comparison of the mains voltage (UN) detected at the common coupling point (206) with at least one value of the predetermined setpoint, and / or the determination of the setpoint values is / are performed by a central control unit (208), - the determination of the setpoint values is carried out on the basis of at least a variable stability criterion, in which the stability criterion is particularly dependent on a grid condition of the alternating current network (206) at the common coupling point (204).
[0003]
Method according to either of claims 1 or 2, characterized in that: the determination of the setpoint values is carried out on the basis of a decomposition in a positive phase sequence system and a phase sequence system negative, using the symmetric components method, and where the setpoint values are values of the positive phase sequence system, that is: - in each case, at least one reactive power QW + EC to be fed, with reference to the positive phase sequence system, of the respective wind energy installation (202), - in each case, at least one output or clamping voltage UW + EC, with reference to the positive phase sequence system, of the respective energy installation wind power (202), and / or - in each case, at least one active power to be supplied, with reference to the positive phase sequence system, of the respective wind power installation (202), particularly a maximum active power PM + THE X, WEC to be fed.
[0004]
Method according to any one of claims 1 to 3, characterized in that: a stability limit is previously calculated and stored for the control, in particular it is stored in the central control unit (208) as a characteristic map.
[0005]
Method according to any one of claims 1 to 4, characterized by the fact that: the active power QWEC, to be fed, and the reactive power PWEC, to be fed, are limited, and the respective setpoint values are determined and transferred to the installation controls.
[0006]
Method according to any one of claims 1 to 5, characterized in that: parameters of the mains supply point (204) are derived from measurements at the mains supply point (204), particularly from the detection of voltage and / or current, in order to evaluate the characteristics of the alternating current network (206).
[0007]
7. Method according to any one of claims 1 to 6, characterized by the fact that: network sensitivities are recorded and stored during a network analysis, previously conducted, and current network sensitivities are detected at a current operating point, and a control, in particular, that at least one setpoint value is predetermined and changed based on a comparison of the current network sensitivity with the previously registered network sensitivity, particularly, where a setpoint value for power active, to be fed, is reduced if, as a result of the comparison, a deviation exceeds or falls below a predetermined limit value (Δ Ut).
[0008]
Method according to any one of claims 1 to 7, characterized by the fact that: a change in a setpoint value for the reactive power, to be fed, and / or the active power, to be fed, is made suddenly and / or, a current network sensitivity is determined based on a response of the network voltage (206) at the common coupling point (204), on one or the aforementioned sudden change.
[0009]
Method according to any one of claims 1 to 8, characterized in that: a hysteresis controller is used to predetermine the setpoint values, and / or a change in at least one of the setpoint values is done, if a status parameter in the grid (206), particularly the grid voltage at the common coupling point (204), meets a predetermined criterion, that is, it exceeds or falls below a predetermined limit value, or exceeds the value of a predetermined limit value, or it leaves a tolerance band, and a predetermined downtime has elapsed after that, and the status parameter continues to satisfy the predetermined criterion.
[0010]
Method according to any one of claims 1 to 9, characterized by the fact that: the impedance of at least one supply line from a wind power installation (202) to the common coupling point (204) is taken into account consideration in specifying setpoint values, to take into account a voltage drop to be expected in the supply line.
[0011]
11. Wind power plant (200) with several wind power installations (202), characterized by the fact that the wind power plant (200) is controlled using a method as defined in any one of claims 1 to 10.
[0012]
12. Wind power plant (200) according to claim 11, characterized by the fact that: the wind power plant (200) comprises a central control unit (208), and each wind power installation (202) of the wind power plant (200) ) comprises an installation control unit (212), in which the central control unit (208) is prepared to provide the installation control units (212) with predetermined setpoint values for reactive power and / or active power, to be fed.
[0013]
Wind power plant (200) according to either of claims 11 or 12, characterized by the fact that at the common coupling point (204), there is a short circuit current ratio (SCR) of less than 4, in particularly less than 2, in particular less than 1.5.
[0014]
14. Wind power installation (202) to produce electricity from the wind, characterized by the fact that: the wind power installation (202) is prepared to be used in a wind power plant (200), as defined in any one of claims 11 to 13, and, in particular, comprises a respective installation control unit (212) for receiving setpoint values from the central control unit (208) of the wind power plant (200).

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同族专利:

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公开号 | 公开日

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RU2015105756A|2016-09-10|

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BR112015001114A2|2017-06-27|

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RU2608955C2|2017-01-27|

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NZ703980A|2016-05-27|

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WO2014012789A1|2014-01-23|

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DE102012212777A1|2014-01-23|

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CA2878993A1|2014-01-23|

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MX364386B|2019-04-25|

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AU2013292247B2|2016-07-07|

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TW201415759A|2014-04-16|

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AR091841A1|2015-03-04|

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AU2013292247A1|2015-02-05|

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JP2015523048A|2015-08-06|

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CL2015000138A1|2015-04-24|

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KR20150036699A|2015-04-07|

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CN104521090B|2018-07-06|

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US20150148974A1|2015-05-28|

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CN104521090A|2015-04-15|

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JP6181177B2|2017-08-16|

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JP2017163838A|2017-09-14|

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MX2015000688A|2015-07-06|

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US10174742B2|2019-01-08|

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IN2015DN00246A|2015-06-12|

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UA116450C2|2018-03-26|

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EP2875562A1|2015-05-27|

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TWI550993B|2016-09-21|

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法律状态:
2018-12-04| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2019-12-24| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2021-02-23| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-04-27| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 02/07/2013, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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DE102012212777.1A|DE102012212777A1|2012-07-20|2012-07-20|Method for controlling a wind farm|

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DE102012212777.1|2012-07-20|

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PCT/EP2013/063974|WO2014012789A1|2012-07-20|2013-07-02|Method for controlling a wind farm|

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