method of determining the contribution of a network subsystem to oscillations in the frequency of th

专利摘要:
grid oscillation analysis method and apparatus for the same. method to determine the contribution of a network subsystem (12) to the oscillations in the network frequency experienced by an external electrical network (14) in an electrical energy network (10). a measurement of the frequency of the grid is made in the grid subsystem (12) and / or in the external power grid (14). the measurement of the mains frequency can be used to extract fluctuations in the mains frequency in the mains subsystem (12) and / or in the external mains (14). a measurement of the active power is recorded on a transmission line (16c) between the grid subsystem (12) and the external power grid (14). the phase relationship between oscillations in the mains frequency and oscillations in active power allows the contribution of the mains subsystem (2) to oscillations in the mains frequency in the external mains (14) to be determined.
公开号:BR112012012712B1
申请号:R112012012712-8
申请日:2010-11-18
公开日:2021-02-23
发明作者:Douglas Wilson
申请人:Psymetrix Limited；
IPC主号:

专利说明:

FIELD OF THE INVENTION
[001] The present invention relates to a method of analyzing network oscillation and an apparatus for the same. More specifically, the invention relates to a method for determining whether a grid subsystem of an electrical grid is contributing to fluctuations in the grid frequency. BACKGROUND OF THE INVENTION
[002] Electricity networks are prone to network fluctuations. For example, fluctuations can be seen in the grid frequency, grid energy, grid voltage angle and / or the speed of generators and other equipment used as part of a network.
[003] The invention here mainly refers to fluctuations in the grid frequency and fluctuations in the grid energy. However, it should be noted that fluctuations in other network metrics are intentionally covered in the scope of the description.
[004] Fluctuations in the frequency of the network can be detrimental to the proper functioning of an electrical network. Fluctuations in the frequency of the network can, for example, trigger interconnector, relay trip, loss of load or generate plant stress. Such oscillations often involve (and affect) many generating plants. For example, frequency fluctuations can be caused by rotor speed fluctuations in generators. In addition, these fluctuations in the frequency of the network can span the boundaries between network areas under the control of different operating companies or limits, perhaps even national ones.
[005] For the avoidance of doubt, it should be noted that, as used herein, the term "Oscillation in the network frequency", when related to electrical power networks, includes variations in the nominal frequency of the network. For example, an electrical network can supply power at a frequency of 60 Hz. However, the frequency can vary between 59 Hz and 61 Hz, with a period of, say, 20 seconds, although this is an extreme example of fluctuations. the frequency of the network. Therefore, the term "oscillation in the grid frequency" refers to the periodic deviations over time of the frequency of an electricity grid, for example, the periodic variations in the nominal frequency of the 60 Hz grid between 59 Hz and 61 Hz .
[006] Variations in the grid frequency and / or energy also have an oscillation frequency associated with them.
[007] The term "grid frequency" includes the frequency of energy supplied by the grid, for example, the nominal value of 50 Hz or 60 Hz of the grid frequency and any deviation from the nominal value.
[008] Under certain network conditions, fluctuations in the network frequency may be poorly dampened or even unstable. Figure 1 illustrates an unstable oscillation in the network frequency that led to the separation of the system and load protection retransmission trigger. More specifically, Figure 1 shows a graph of the frequency of the network over time, in which a nominal system of 60 Hz oscillates at low frequency with a period of about 20 seconds, with oscillations from 59 Hz to 61 Hz.
[009] The present inventors appreciated that it is currently difficult to determine whether a given network subsystem, such as a plant, the generation control area of some or the defined region of the network is contributing positively or negatively to the stability of an oscillation in the network frequency, or simply responding to the frequency fluctuation of the network.
[0010] It is, therefore, an objective of the present invention to provide a network comprising an electrical apparatus that is operable to determine whether a network subsystem contributes positively or negatively to the stability of oscillation in the frequency of the network.
[0011] It is still an objective of the present invention to provide a method for determining whether a grid subsystem of an electrical grid is contributing positively or negatively to the stability of oscillations in the grid frequency. DECLARATION OF THE INVENTION
[0012] According to the invention, in a first embodiment, a method is provided to determine the contribution of a network subsystem of oscillations in the frequency of the network in an external electrical network of an electrical power network, the method comprising: receiving a first amount corresponding to the network frequency fluctuations in the external power grid, which receive at least a second quantity, at least a second amount corresponding to active energy fluctuations transmitted in at least one electrical connection between the grid subsystem and the electrical network external, and determine at least one phase relationship between the first quantity and at least a second quantity to determine the second component that contributes to the number of fluctuations in the frequency of the grid in the external electrical network.
[0013] The applicant has identified that, in determining the phase relationship between oscillations in the network frequency and oscillations in the active power transmitted in an electrical connection, it can be determined whether the subsystem is contributing to or responding to the oscillation. In addition, the magnitude of the component of energy oscillations in quadrature with the frequency oscillations of the network allows the quantification of the contribution of the network subsystem to the frequency oscillations of the network.
[0014] As used herein, the term "network subsystem" includes one or more electrical components that may form part of an electrical power network. For example, a network subsystem may include one or more generators and substations.
[0015] As used herein, the term "external electrical network" encompasses all elements of an electrical energy network that are external to a network subsystem. The external network can therefore represent the largest network or, to put it another way, the rest of the electricity network.
[0016] As used herein, the term "electrical energy network" encompasses any network of electrical elements that are interconnected for the purpose of providing electrical energy.
[0017] The first quantity can be measured in the network subsystem. Alternatively, the first quantity can be measured on the external power grid.
[0018] Note that a phase relationship is a relationship between two quantities that oscillate on the same frequency, in such a way that there is a consistent time change between the peaks of the oscillating quantities. This time shift can be expressed in terms of a phase angle, or the "phase relationship" between the quantities. There is an amplitude of oscillation associated with each amount of oscillation, and together the phase angle can be expressed as a vector. This vector can be broken down into components for analysis.
[0019] Optionally, the method can also comprise the determination of the magnitude of the component of the second quantity that is squaring with the first quantity.
[0020] The components of a sign that are in quadrature are orthogonal to another sign. This is what can lead or stay for another 90 degree signal. The applicant identified that the contribution of a grid subsystem to fluctuations in the grid frequency in an external power grid can be determined by determining the component of fluctuations in the active power that leads to or keeps the fluctuations in the grid frequency.
[0021] Optionally, the first quantity can comprise fluctuations in the frequency of the network in the network subsystem.
[0022] Often, the grid subsystem can be more accessible than the elements of the external power grid. This may be because certain elements of the external electrical network may be located in other countries or territories. Therefore, the advantages of ease of measurement arise when the first quantity corresponds to fluctuations in the network frequency in the network subsystem.
[0023] Measurements of fluctuations in the mains frequency in the mains subsystem can correspond to the mains frequency fluctuations in the external mains indicating the type of oscillation grid as explained below. That is, if the type of oscillation grid is common, then the oscillations of the external mains frequency will be the same phase as the oscillation in the mains subsystem mains frequency. If the type of oscillation grid is of the opposite phase, then the oscillations of the grid frequency in the external power grid will be in opposite phase to the oscillations in the grid frequency in the grid subsystem. In this way, the measurements of the grid frequency, both in the grid subsystem and in the external power grid correspond to fluctuations in the grid frequency in the external power grid.
[0024] Optionally, the method can also comprise a third amount of reception comprising fluctuations in the frequency of the network within the external electrical network.
[0025] Receiving measurements corresponding to fluctuations in the grid frequency within the external power grid allows a more robust determination of the contribution to the fluctuations as explained below.
[0026] Optionally, the method can also comprise measuring the quantity of first within the network subsystem, measuring the second quantity of at least one electrical connection to the network subsystem and measuring the third quantity within the external electrical network.
[0027] Optionally, the method can also comprise determining whether the network frequency oscillations of the network subsystem is in the common mode for the oscillations in the network frequency in the external power grid depending on the frequency of the first quantity being less than 0.1 Hz .
[0028] Optionally, the method can also comprise determining whether oscillations in the network frequency of the grid subsystem are in the common mode for oscillations in the frequency of the network in the external power grid depending on the first quantity being the same amplitude and phase, while the third quantity.
[0029] The determination that the type of network frequency oscillations is common allows the determination of whether a network subsystem is contributing positively or negatively to the oscillations in the network frequency based on the phase relationship of the first quantity with the second quantity. In the common mode, if a component of the second quantity conducts the phase of the first quantity, then the network subsystem is determined to be negatively contributing to the oscillations.
[0030] Optionally, the method can also comprise the determination of the magnitude of a component of the second quantity that conducts the phase of the first quantity by 90 degrees.
[0031] Optionally, the method can also comprise determining whether oscillations of the grid frequency in the grid subsystem are in phase opposition with the oscillations of the grid voltage in the external power grid depending on the frequency of the first quantity being greater than 0.2 Hz.
[0032] Optionally, the method can further comprise determining whether oscillations of the grid frequency in the grid subsystem are in phase opposition with the oscillations of the grid voltage in the external power grid in dependence on the first being the amount of 180 degrees outside phase with the third quantity.
[0033] The determination that the type of network frequency oscillations is of the opposite phase allows the determination of whether a network subsystem is contributing positively or negatively to the oscillations in the network frequency based on the phase relation of the first quantity with the second quantity. In the opposite phase, if a component of the second quantity is in the phase of the first, when the first quantity quantity comprises oscillations in the frequency of the network in the network subsystem, then the network subsystem is determined to be contributing negatively to the oscillations.
[0034] Optionally, the method may also comprise determining a magnitude of a component of the second phase delay amount of the first quantity by 90 degrees.
[0035] Optionally, at least one electrical connection may comprise a plurality of electrical connections between the grid subsystem and the external electrical network, and the second quantity may correspond to a sum of the active energy oscillations carried in each of the plurality of connections electrical.
[0036] Optionally, at least one electrical connection may comprise a plurality of electrical connections between the network subsystem and the external electrical network and receiving at least a second quantity may comprise receiving a plurality of second quantities, each second quantity corresponding to fluctuations of active energy carried in one of a plurality of electrical connections, and determining at least one phase relationship may comprise determining a plurality of phase relationships between the first quantity and the plurality of second quantities to determine the components of the plurality second quantities that contribute to fluctuations in the frequency of the grid in the external power grid.
[0037] Optionally, the method can also comprise the determination of the magnitudes of the components of the second quantity that are square with the first quantity.
[0038] Optionally, the method can also comprise adding the magnitudes of the components of the second quantity that are squaring with the first quantity.
[0039] According to the invention, in a second embodiment, a method is provided to determine the contribution of a network subsystem from a plurality of network subsystems of oscillations in the frequency of the network in an external electrical network of an electrical energy network , comprising the method: determining the contribution of a first network subsystem from a plurality of network subsystems according to the method above, which determines the contribution of a second network subsystem according to the method above, in which the magnitude of the contribution of the first network subsystem is greater than the magnitude of the contribution of the second network subsystem, and normalize the magnitude of the second network subsystem to the magnitude of the first network subsystem.
[0040] Optionally, the method can also comprise the determination that the second network subsystem is contributing to the network frequency oscillations in the external power grid, if the normalized magnitude of the second network subsystem is 0.5 or more.
[0041] According to the invention, in a third embodiment, a computer program product is provided which comprises the program code executable on a computer processor computer to carry out the method described above.
[0042] According to the invention in the fourth embodiment, an apparatus is provided to determine the contribution of a network subsystem of oscillations in the frequency of the network in an external electrical network of an electrical power network, comprising the apparatus: a processor configured to receive a first corresponding amount for the oscillations in the external mains frequency, receiving at least a second amount, at least a second amount corresponding to oscillations in the active power carried in at least one electrical connection between the grid subsystem and the external electrical network, and determine at least one phase relationship between the first quantity and at least a second quantity to determine the second component that contributes to the number of oscillations in the frequency of the network in the external electrical network.
[0043] Optionally, the processor can be further configured to determine the magnitude of the component of the second quantity that is squaring with the first quantity.
[0044] Optionally, the device also comprises a first measurement unit in connection with communications with the processor and for at least one electrical connection for the network subsystem, the first measurement unit designed to measure the first and / or second quantities and provide them to the processor.
[0045] Optionally, the first measurement unit can comprise a phasor unit of measurement.
[0046] In accordance with the invention, in a fifth embodiment, an electrical network is provided comprising the apparatus described above.
[0047] When referring to oscillations in the grid frequency, in the first and second zones of the grid, being 180 degrees out of phase, it should be noted that this includes oscillations in the network frequency, which are about 180 degrees out of phase . For example, the mains frequency oscillation can be 180 degrees out of phase + / - 45 degrees.
[0048] According to the invention, in a fifth embodiment, an electric grid is provided, comprising: a network subsystem; measuring devices that are operable to measure a first quantity that corresponds to the network frequency of an electrical connection to the network subsystem over time and to measure a second quantity that corresponds to the active power carried in an electrical connection from the subsystem of network over time, each of the first quantity and the second quantity changing oscillatively over time, and a processing apparatus that is operable to determine a phase relationship between the first and second oscillating quantities.
[0049] In use, the measuring device measures the first quantity, for example, the mains frequency, and the second quantity, for example, the active power. The first quantity, which corresponds to the oscillating mains frequency, oscillates at a frequency, for example, below the nominal mains frequency at a frequency such as 0.06 Hz, which is characteristic of the mains oscillation. The second quantity oscillates in a way that is also a characteristic of the oscillation of the network. Thus, it is the change, that is, the oscillation, in each of the first and second quantities over time, that is operated by the processing apparatus.
[0050] More specifically, the first quantity can be the network frequency.
[0051] Alternatively, the first quantity can be a measurement of angles. An oscillation in the angle of a measuring voltage is equivalent to an oscillation in the mains frequency measured at substantially the same location, for example, on the same bus, with a phase shift of 90 degrees. Alternatively, the first quantity may be the angle of a generator rotor, although the same 90 degree phase change is required. Alternatively, the first amount can be the speed of the generator rotor. The generator rotor can rotate at a frequency corresponding to the mains frequency and therefore fluctuations in the mains voltage can be apparent in the speed of the generator rotor.
[0052] Alternatively, or, in addition, the second quantity can be the active current. Active power can be derived from voltage measurements, for example, on a bus, and current measurements, for example, on a link circuit for the bus.
[0053] Alternatively, or, in addition, the second quantity may be current, for example, as measured in a connection circuit for the bus. Therefore, the measured current may correspond to fluctuations in active energy.
[0054] The processing apparatus is operative to determine the phase relationship between the first and second oscillating quantities. For example, the processing apparatus can be operative to determine whether there is a phase difference between the first and second oscillating amounts.
[0055] A frequency oscillation for an electrical network can represent an oscillation in the speed of rotation of machines, for example, generators, rotating within the network. Periodic oscillation involves accelerating and decelerating the network, or parts of it, and rotating machines are accelerating and decelerating together with the frequency of oscillation. These cyclic changes in the speed of rotation occur due to binary cycles that act on the rotating components. The presence of oscillations in the speed of masses in a network or subsystem of rotation can mean that there are oscillations of mechanical and / or electrical energy supplied or exported from the subsystem.
[0056] Depending on the physical properties of its constituent parts, and the contribution of control systems, a network subsystem can supply energy to maintain oscillation or remove energy from oscillations.
[0057] When measuring the oscillations of the first quantity, for example, the network frequency, in the subsystem and in the second quantity, for example, the power flow from the wider network subsystem, it is possible to identify whether the subsystem is improving or degrading the stability of the oscillations. In the case of common mode oscillations, if the oscillations of the second quantity lead to oscillations of the first quantity between zero and 180 degrees, the subsystem is degrading the stability of the oscillation by supplying energy to maintain the oscillation. Thus, the operating company can carry out investigations on the network subsystem to determine the nature of the problem. If the oscillations in the second quantity are in the oscillations of the first quantity, which is between zero and 180 degrees, the subsystem is improving the stability of the oscillation by extracting energy from the oscillation and providing damping of the oscillation. Thus, the operating company does not need to carry out investigations on the network subsystem. Alternatively, and where there is a cross-border problem, involving, for example, two or more operating companies, an exploration company can demonstrate that its network area is not contributing to the oscillation of the network. The extent of the positive or negative contribution may be related to the amplitude of the power fluctuations and also how close the phase difference is to 90 degrees.
Thus, alternatively or in addition, the processing apparatus can be operated to determine whether one of the first and second quantities leads to another of the first and second quantities.
[0059] Alternatively or in addition, the measuring device may comprise a phasor measuring unit (PMU), which is operative to measure the first and second quantities in electrical connection. Thus, the PMU can work to measure the frequency of the oscillating network and active power signals.
[0060] The first quantity can be measured in a number of ways. More specifically, if the subsystem comprises a generation plant, the first quantity can be measured by measuring the speed of at least one rotation device, such as an axis of rotation, or the turbine generator of the generation plant. When the generation of plants comprises a plurality of generating units, an average of speed measurements in each of the rotation devices can be determined. Alternatively, or in addition, the first quantity can be derived from a voltage measurement of the sine waveform, for example, on a bus.
[0061] Alternatively or in addition, a first measured quantity can be synchronized with an external time reference, for example, a Global Positioning System (GPS), source of time.
[0062] Alternatively or in addition and in which the subsystem comprises a plurality of generators, the first quantity can be measured in each of a plurality of different locations to provide plural first quantitative measurements. More specifically, the first amount of oscillation operated by the processing apparatus can be determined by one of the following: the average of the plural measurements first quantity, determining a weighted average of the plural first quantity measurements, and selection of a single first measured quantity more of the plural measurements of the first quantity.
[0063] Alternatively or in addition, the measuring device may comprise an analog to digital converter, which is operative in such a way that the first and second measured quantities are output in digital format. For example, the measuring device can be operative to measure voltage and current waveforms, to convert the voltage of each of the measured current signals and to a digital format and to derive the first and second quantities of the digital voltage and current signals.
[0064] Alternatively or in addition, the processing apparatus may be operative to determine a measure of the phase difference between the first and second measured oscillating quantities.
[0065] Alternatively or in addition, the processing apparatus may comprise cross-correlation apparatus which are operative to correlate the first and second quantities with each other. Thus, the cross-correlation analysis apparatus can be operative to determine a measure of the phase difference between the first and second oscillating quantities.
[0066] Alternatively or in addition, the processing apparatus may comprise an output apparatus that can be operated to provide an output to a user. More specifically, the output apparatus can be operable to provide a phase relationship between the first and second oscillation quantities for the user. The user can then call one of the following conclusions from the phase relationship: • The subsystem is degrading the stability of the network with respect to the type of oscillation; • The subsystem is responding to an oscillation in the network and is contributing to dampening the oscillation; • The subsystem is responding to an oscillation in the network, but is not providing any positive or negative contribution to dampening the oscillation; • The oscillation is transferred through a network of the subsystem, the subsystem, but is not responding substantially in any way.
[0067] Alternatively, or in addition, an oscillation frequency of the first quantity and the second quantity may be less than a grid frequency, for example, a grid frequency of 50 Hz or 60 Hz.
[0068] More specifically, the oscillation frequency can be substantially less than 10 Hz. More specifically, the oscillation frequency can be substantially less than 5 Hz. More specifically, the oscillation frequency can be substantially less than 100 mHz. Alternatively, or in addition, the oscillation frequency can be substantially between 0.003 Hz and substantially 2 Hz.
[0069] Alternatively or in addition, the grid subsystem may comprise one of the following: a power unit, such as a generator, a control zone, and an area of the electricity network. The electricity grid area can include at least one power plant or the control area. The term "control area" as used here can mean the area of an electrical network that a transmission system operator has a responsibility to control.
[0070] The subsystem can be interconnected with the broader system, through any number of electric current transmission lines. The second quantity, for example, active power, used in accordance with the invention may represent the oscillation in the total value of, for example, the active power of the subsystem for the external electrical network. The second quantity can be adequately represented by the sum of the second quantities in the main transmission routes. Thus, alternatively, or in addition, the electrical current may comprise a plurality of electrical connections, for example, main transmission paths, to the network subsystem. For example, a first electrical connection can connect the subsystem of another subsystem, and a second electrical connection can connect the subsystem to yet another subsystem. More specifically, the electric current may comprise a plurality of measuring devices, each measuring device being operable to measure at least one of the first and second quantities in a different one than a plurality of electrical connections. More specifically, the processing apparatus can be operative: to determine the extent of the contribution between at least one of the first and second quantities of each electrical connection, and to summarize the determined extensions. Thus, when there are a plurality of electrical connections in a network subsystem, it may be possible to determine whether the network subsystem is contributing positively or negatively to the stability of the oscillation network.
[0071] Alternatively, or in addition, the electrical network may be an electrical energy network.
[0072] According to a sixth embodiment of the present invention, a method is provided to determine whether a grid subsystem of a power grid is contributing to the grid oscillation or not, the method comprising: measuring a first quantity corresponding to the frequency of the network from an electrical connection to the network subsystem over time, and a second quantity corresponding to the active power carried in an electrical connection to the network subsystem over time by means of measuring devices, each of the first and second quantities of oscillatory change over time, and the determination by means of the apparatus processing a phase relationship between the first and second quantities that oscillate.
[0073] The embodiments of the sixth embodiment of the present invention can comprise one or more features of the fifth embodiment of the present invention.
[0074] In accordance with a seventh embodiment of the present invention, there is provided a kit of parts configured to be installed in an electricity network comprising a network subsystem, the kit of parts comprising: measuring device which after installation is configured to and operable to measure a first quantity corresponding to the network frequency of an electrical connection to the network subsystem over time, and a second quantity corresponding to the active power transmitted from an electrical connection from the electrical connection to the network subsystem over time. time, of each of the first and second quantities changing oscillatively over time, and the processing apparatus which after installation is operable to determine a phase relationship between the first and second oscillating quantities.
[0075] The embodiments of the seventh embodiment of the present invention may comprise one or more features of the fifth embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0076] Other characteristics and advantages of the present description will be evident from the following specific description, which is given by way of example only and with reference to the attached drawings, in which: Figure 1 is a graph of the network frequency along the time, which is subject to the effects of network oscillation; Figure 2 is a schematic diagram of a network subsystem connected to an electrical network; Figure 3 shows a method for determining the contribution of a network subsystem of oscillations in the frequency of the network in an external electrical network; Figure 4A is a graph in which the active oscillating power slows down the frequency of the oscillating network; Figure 4B is a graph in which the active oscillating power slows down the frequency of the oscillating network and Figures 5A-C show illustrative screens that can be provided by a device according to the invention. DESCRIPTION OF ACCOMPLISHMENTS OF THE INVENTION
[0077] Note that the unstable oscillations in Figure 1 must be distinguished more than stable oscillations, which are oscillations that are dampened and remain small. Stable oscillations can be inherently dampened by the elements of the electrical network without the input of an operator. An operator can indirectly influence the damping of the electric grid, changing the generation dispatch and, therefore, the energy flows in the grid. With the appropriate information, the operator can improve the stability of the system by changing the generation outputs.
[0078] Unstable oscillations grow in amplitude to a level that threatens the security of an electric power network, while stable oscillations remain small and do not necessarily threaten the security of an electric power network.
[0079] The method of the invention applies in both cases and can be used to determine the contributions of the network subsystems to unstable oscillations in the network frequency and / or stable oscillations in the network frequency. Figure 1 shows an example of unstable oscillations in the network frequency.
[0080] Generally, oscillations in the network frequency can be divided into two groups: frequency oscillations in common mode, and opposing phase frequency oscillations.
[0081] Common mode frequency oscillations occur when the entire frequency of the network oscillates with substantially a coherent phase, that is, in phase. If the frequency is measured anywhere on the grid, practically the same oscillation would be seen. Both the amplitude and the phase of the oscillation are substantially equal across the grid. Common frequency oscillation mode where the frequency oscillation is in phase, the whole system tends to be in very low frequency, for example, 0.06Hz.
[0082] The person skilled in the art will appreciate that two oscillating quantities measured are rarely precisely "in phase". For example, errors inherent in measurement techniques may mean that two signals that are in phase will not be measured as being exactly in phase. In addition, it is rare in an electrical power network that signals that are "in phase" have exactly the same phase. Indeed, the person skilled in the art will appreciate that "in phase" is a term that can be applied to two signals, which are substantially in phase, as explained below.
[0083] Opposite phase frequency oscillations occur where there are two groups of generators that operate in two areas of an electrical power network. Within a generator set of frequencies that oscillate in phase with each other, but from one group to another, there is a phase change in frequency oscillations of about 180 degrees. Opposite phase frequency oscillations generally occur at a slightly higher frequency than common mode frequency oscillations, typically between 0.1 Hz and 2 Hz. Inter-area electro-mechanical oscillations are an example of opposite phase oscillations in the grid frequency that occur in different areas of an electricity grid. Likewise, the local electro-mechanical oscillations mode are also opposite phase oscillations, but the amplitude of the oscillations of the opposite phase are much smaller than the oscillations in the main generator or participating generators.
[0084] Thus, with opposite phase frequency oscillations, if a frequency oscillation is observed in the network area of the first generator group, it would be possible to find a location in the grid area of the opposite group where the oscillation frequency was substantially as opposed to phase. There may be a different amplitude, but the shape of an oscillating frequency waveform is about a mirror image of the other scale.
[0085] As with the definition of the common mode stated above, two signals in opposition phase are rarely exactly 180 degrees out of phase. Indeed, the person skilled in the art will appreciate that the characteristics of an electrical power network can determine that the opposite phase is a term that can be applied to two signals that are substantially 180 degrees out of phase.
[0086] Inter-zone oscillations are an example of the opposite phase oscillations in which the opposite phase of the network frequency oscillations that occur in different areas of an electric power network. An example of inter-zone phase frequency fluctuations is that generators in Scotland may be in a first network area and fluctuate together, as a group, and northern England generators may be in a second network area and they also oscillate together forming a group. The two groups can oscillate in the opposite phase to say approximately 0.5 Hz. In other examples, the areas of the network can be very large. There are frequency oscillation modes that cross the whole of Europe, with Spanish, Portuguese and French generators oscillating in the opposite phase of the Balkans and the Eastern Europe.
[0087] Note that when referring to the phase of taking or delaying power fluctuations, the convention used here is of positive energy flow being from a grid subsystem of a grid.
[0088] Referring to Figure 2, the schematic representation of an electric power network 10 is shown. Figure 2 shows an electric power network 10, in which it can be determined whether a network subsystem 12 is contributing to oscillations in the network frequency.
[0089] The electric power network 10 is composed of a network subsystem 12 and an external electric network 14. The network subsystem 12 can be one or more energy generators. The external electrical network 14 can also include power generators and / or interconnected control areas within the external electrical network.
[0090] The term "external electrical network" 14 refers to all elements of the electrical energy network, which are separate or external to the network subsystem 12.
[0091] The network subsystem 12 is connected to the external electrical network 14, through electrical connections (or transmission lines) 16a, 16b, 16c.
[0092] Frequency measuring units 18a, 18b, 18c, which can be phasor measuring units (PMU), are operable to measure the frequency of a voltage present in the network subsystem 12. The PMU 18a, 18b, 18c can be positioned at the end of transmission lines 16a, 16b, 16c, respectively, and can therefore only be positioned within or at the limit of the network subsystem 12. However, the skilled person will understand that the PMU 18a, 18b, 18c can be placed at other locations within the appropriate network subsystem 12 to measure the frequency of the voltage within the network subsystem 12.
[0093] The frequency of the voltage waveform fluctuates or varies over time and the measured variation may constitute a first quantity.
[0094] The active power and frequency measurements of the PMU are transmitted electrically to a central location 32. This is shown schematically in Figure 2 via the communications link 20 from the PMU 18a to the central location 32. The communications link 20 can be a wired or wireless communication connection, an optical data connection or any other form of data communication connection, as will be known to the person skilled in the art. Central location 32 comprises a computer having a central processor 36, data storage 38 and an output device 40. The central processor unit 36 is configured to perform digital signal processing operations, such as cross correlation. The design and implementation of the aforementioned electronic device present in the central location and the firmware needed to perform the data processing, including cross-correlation, is readily within the scope of the qualified person's common project skills.
[0095] The frequency and power measurements taken by the PMU 18a, 18b, 18c are routed to the processor 36 via a communications link 20.
[0096] In addition, one or more measurement units can be placed inside the external electrical network 14. The measurement units within the external mains 14 transmit frequency measurements from within the external mains 14 to the processor 36 via a communications link 22.
[0097] The fundamental characteristics of an oscillation in the mains frequency can be seen in voltage phasor angle measurements, for example, or in generator rotor speed oscillations, which can be used as a substitute for frequency measurement . In the case of the voltage angle, it is generally not a 90 degree phase shift, but the concept still stands.
[0098] PMU 18a, 18b, 18c can also be operable to measure variations in active power, which can constitute a second quantity, carried in electrical connections 16a, 16b, 16c.
[0099] The quantities measured with the PMU 18a, 18b, 18c are synchronized. Synchronization can be achieved within a PMU or can be achieved with an external time reference, such as from a GPS time source. Each PMU 18a, 18b, 18c can be an AREVA P847 from AREVA T & D of St. Leonards Avenue, ST17 4 LX, Stafford, United Kingdom. Each PMU is operative to produce digital data.
[00100] The electric power network 10 of figure 2 can be the subject of an oscillation in the mains frequency, for example, a common mode of oscillation as shown in Figure 1 or an opposite phase oscillation.
[00101] The frequency of the network in the network subsystem is measured by the PMU 18a. In addition, the frequency of the mains on the external mains 14 is measured at a location within the external mains 14. The location at which the frequency of mains 14 on the external mains is measured is not shown in Figure 2. In general, the The location of such a measurement must be far from the network subsystem 12, so that it is less likely to be influenced by oscillations in the network subsystem 12.
[00102] The unit of measurement, located in the external electrical network can be the PMU. However, other units of measurement that are within the knowledge of the person skilled in the art and are suitable for measuring the network frequency can be used. In addition, the person skilled in the art will appreciate that there may be a plurality of frequency measurements recorded in the network subsystem 12 and / or in the external electrical network14.
[00103] PMU 18a can be configured to measure the frequency of the voltage in the network subsystem 12. The frequency of the voltage in the network subsystem can be transmitted to the processor 36. From the frequency of the voltage waveform of the processor 36 it is able to measure the oscillation in the network frequency within the network subsystem over time. It will be apparent to the person skilled in the art that other methods of measuring the frequency of grid oscillation can be used within the scope of the present invention.
[00104] If there is more than one network frequency measurement arrangement in network subsystem 12, the most important one can be selected for use. The most important measure can be, for example, the measurement showing the highest oscillation frequency within the subsystem 12.
[00105] Likewise, the measurement unit located on the external power supply 14 can be configured to measure the frequency of the voltage on the external power supply 14. The frequency of the voltage is transported to the processor 36 via a communications link 22. The communications link 22 can be a wired or wireless communication link, an optical data link or any other form of data communication link, as will be known to the person skilled in the art. From the frequency of the voltage, the processor 36 is able to calculate the oscillation in the mains frequency within the external mains over time. It will be apparent to the person skilled in the art that other methods of measuring the frequency of grid oscillation can be used within the scope of the present invention.
[00106] Using the oscillation extracted from the grid frequency in the grid subsystem 12 and extracting the oscillation in the grid frequency from the external power grid 14, the processor can be configured to determine whether the oscillations in the grid voltage of the grid subsystem 12 and the external electrical network 14 are in common mode or opposite phase.
[00107] This can be done by comparing the amplitude and phase of measurements of fluctuations in the grid frequency in grid subsystem 12 with the amplitude and phase of measurements of fluctuations in the grid frequency in the external electrical grid 14. If both sets measurements are substantially similar in amplitude and phase, so it can be determined that oscillations in the network frequency are common. Otherwise, the frequency fluctuations in the network are considered to be in phase opposition.
[00108] In the case of common mode, when comparing the oscillations in the grid frequency in the grid subsystem 12 and the oscillations in the grid voltage in the electrical grid 14, the errors inherent in the measurement of the two quantities may mean that the oscillations in frequency they are not precisely the same phases. In addition, the characteristics of the electric power network 10 can be such that signals that are not exactly in phase can still be considered in common oscillation mode.
[00109] There must be a phase change between the frequencies of different places, otherwise, there would be no oscillation energy flow and no oscillation would be sustained. This phase difference tends to be small, for example, less than 10 degrees.
[00110] For example, in some realizations of the phase of the oscillations in the network frequency in the network subsystem 12 and the external electrical network 14 can oscillate in common mode if they are in the same phase of plus or minus 45 degrees. Alternatively, the phase of the oscillations in the grid frequency in the grid subsystem 12 and the external power grid 14 can be in common oscillation mode if they are in the same phase of plus or minus 30 degrees. Alternatively, the phase of the oscillations in the grid frequency in the grid subsystem 12 and the external power grid 14 can be in the common oscillation mode, if they are the same phase plus or minus 20 degrees. Alternatively, the phase of the oscillations in the grid frequency in the grid subsystem 12 and the external electrical grid 14 can be in the common oscillation mode, if they are the same phase plus or minus 10 degrees.
[00111] Alternatively, the phase of oscillations in the frequency of the grid 12 in the grid subsystem and the external electrical grid 14 can be in the common oscillation mode, if they are the same phase more or less 5 degrees.
[00112] In addition, similar phenomena can be seen when comparing measurements of the amplitude of oscillations in the network frequency.
[00113] Therefore, the oscillations in the frequency of the grid 12 in the grid subsystem and the external electrical grid 14 can be considered the same to determine the oscillation in common mode, if they are the same amplitude of plus or minus 20%. Alternatively, the amplitude of the oscillations of the mains voltage, in the mains subsystem 12 and the external electrical network 14 can be considered the same for the determination of oscillation in a common way if they are the same amplitude of plus or minus 10%. The amplitude of the oscillations in the grid frequency in the grid subsystem 12 and the external power grid 14 can be considered the same for the determination of oscillation in a common way if they are the same amplitude of plus or minus 5%.
[00114] In the case of the opposite phase, when the frequency oscillations of the network in the network subsystem 12 and the oscillations in the network voltage in the electrical network 14 are compared, the errors inherent in the measurement of two quantities may mean that the frequencies are not precisely 180 degrees out of phase. In addition, the characteristics of the electric power network 10 can be such that signals that are not 180 degrees out of phase can still be considered in opposition to the oscillation phase.
[00115] Considering that the angles refer to the relative positions of the generator rotors of different sizes and types of machines connected through power transmission lines, an exactly opposite symmetrical phase oscillation can be very unlikely in a power grid electrical.
[00116] For example, in some realizations of the phase of the oscillations in the grid frequency in the grid subsystem 12 and the external power grid 14 may be in phase opposition, if the oscillation of 180 degrees out of phase by plus or minus 45 degrees . Alternatively, the phase of the oscillations in the grid frequency in the grid subsystem 12 and the external electrical grid 14 may be in phase opposition, if the oscillation of 180 degrees out of phase by plus or minus 30 degrees. Alternatively, the phase of the oscillations in the grid frequency in the grid subsystem 12 and the external electrical grid 14 can be in phase opposition, if the oscillation of 180 degrees out of phase by plus or minus 10 degrees. Alternatively, the phase of the oscillations in the grid frequency in the grid subsystem 12 and the external electrical grid 14 may be in phase opposition, if the oscillation of 180 degrees out of phase by plus or minus 5 degrees. The term "phase opposition", therefore, applies to frequency measurements that correspond to any of the above examples.
[00117] It is also possible to determine whether oscillations in the network frequency are the common mode, or opposition phase, without any comparison of oscillations in network frequency measurements of the network subsystem 12 and the external electrical network 14. For example, if the oscillation calculated in the mains frequency is only available from the mains subsystem or external mains, then the type of oscillation can be inferred.
[00118] In such circumstances, the type of fluctuations in the mains voltage can be determined based on the frequency of the fluctuations calculated in the mains frequency.
[00119] That is, if the frequency of oscillation calculated in a grid inside the subsystem of the grid 12 or, the external power grid 14 is less than 0.2 Hz, then the variations in the grid voltage can be determined as being the mode common across the entire power grid 10, which includes subsystem 12. Alternatively, if the oscillation frequency calculated in a grid within the grid 12 subsystem or, the external power grid 14 is less than 0.1 Hz, then fluctuations in the mains voltage can be determined to be the common mode across the entire power grid 10, which includes subsystem 12. Alternatively, if the oscillation frequency calculated in a grid within the grid subsystem 12 or, the external electrical network 14 is less than 0.06 Hz, then the network frequency fluctuations can be determined to be the common mode throughout the entire electrical energy network 10, which includes subsystem 12.
[00120] Otherwise, if the fluctuations in the grid frequency measured within the grid subsystem 12 or the external power grid 14 are greater than 0.2 Hz, then the fluctuations in the grid frequency can be determined in opposition to phase. In other embodiments, if the oscillations in the mains frequency measured within the mains subsystem 12 or the external mains 14 is greater than 0.1 Hz, then the oscillations in the mains frequency can be determined in phase opposition.
[00121] Therefore, it is possible to infer from measurements in a network subsystem that there is a part of the network oscillating at about 180 degrees out of phase for the network subsystem, even if there are no measurements that are performed to display this . In practice, if the oscillation is observed in a network subsystem, with a significant / measurable amplitude in one location, and the oscillation is not measurable, it is measurable or with a much smaller amplitude in another location, then it can be inferred that somewhere in the network there is an opposite oscillation frequency.
[00122] The threshold for determining whether oscillations are common mode or opposite phase can be adjusted between 0.1 Hz and 0.2 Hz. Oscillations below the threshold are considered the common mode and oscillations above the threshold are considered to be in opposition phase.
[00123] The same principles can also be applied, if a measurement of the external electrical current 14 is close to the network subsystem 12.
[00124] The active power can be measured at the electrical connection 16a between the network subsystem 12 and the external power network 14. The measurement of active power can be taken by PMU 18a and forwarded to central processor 36. The central processor can be configured to calculate (or extract) oscillations in active power over time.
[00125] The central processor 36 is operative to cross-correlate the oscillations calculated in the network frequency and oscillations in the active power signals of the PMU 18a to determine the phase relationship between the oscillations in active power and the oscillations in the network frequency. In one embodiment, the central processor 36 can be configured to determine a magnitude of the power fluctuation component that is squaring with the frequency fluctuations of the network.
[00126] In addition, central processor 36 can be operative to cross-correlate calculated network frequency oscillations and oscillations in active power signals from other PMUs to determine a magnitude of the energy oscillation component that is in quadrature with the frequency oscillations of the network.
[00127] If it is determined that the oscillations of the mains voltage are common, then the contribution of the network subsystem 12 to the mains frequency oscillations can be determined by determining the amplitude of the oscillations of the active power that is in quadrature with the frequency fluctuations of the network. That is, the magnitude of the oscillation component in the active power that leads to oscillations in the mains voltage of 90 degrees. The central processor 36 is therefore configured to determine the contribution of the network subsystem to the frequency fluctuations of the network, in this way, if it is determined that the fluctuations in the network voltage are in common mode.
[00128] The contribution of a grid subsystem 12 to fluctuations in the grid frequency in the external power grid 14 can be measured in power.
[00129] The contribution can be determined as the component of a vector representing oscillations in the active power in quadrature, that is, at 90 degrees, for a vector representing oscillations in the network frequency in the network subsystem or the external electrical network.
[00130] The phase angle between the vector representing oscillations in the active power and the vector representing oscillations in the network frequency can be used in conjunction with the magnitude of the vector representing oscillations in the active power, in order to obtain the contribution. The contribution can be determined as: Contribution = P. sine (delta), where P is the magnitude of the vector that represents oscillations of active energy and delta is the phase angle between the vector representing oscillations in active power and the vector that represents oscillations the frequency of the network.
[00131] This is the energy oscillation component in quadrature with the frequency of oscillation.
[00132] The phase angle can also be used without magnitude to identify whether the subsystem contributes positively or negatively to the oscillation.
[00133] For the avoidance of doubt, it is observed that, if the oscillations in active power lead to oscillations in the mains frequency between 0 and 180 degrees, a component of the oscillations in active power will cause the oscillations in the mains frequency to be 90 degrees.
[00134] If it is determined that the mains voltage oscillations are in phase opposition, then the contribution of the mains subsystem of 12 to the mains frequency oscillations can be determined by determining the amplitude of the oscillations of the active power which is in quadrature with the oscillations in the mains frequency in the external mains 14. This is the magnitude of the oscillation component in the active power that leads to oscillations in the mains voltage in the external mains 14 to 90 degrees. The central processor 36 is, therefore, configured to determine the contribution of the network subsystem to the frequency fluctuations of the network, in this way, if it is determined that the fluctuations in the network voltage are in phase opposition.
[00135] The person skilled in the art will appreciate that, if the network oscillations are in phase opposition, then the oscillations of the network subsystem 12 are substantially 180 degrees out of phase with the oscillations of the external electrical network 14. Therefore , the magnitude of the component of active energy fluctuations, which leads to fluctuations in the mains voltage in the external power grid 14 to 90 degrees correspond to the magnitude of the component of the fluctuations in the active power, which slows down the fluctuation in the grid frequency network subsystem 12 in 90 degrees.
[00136] In addition, either fluctuations in the grid frequency in the grid subsystem 12 or fluctuations in the grid voltage in the external grid 14 can be inferred as described above. Therefore, the contribution of grid subsystem 12 to oscillations in the frequency of the grid in the external power grid can be determined by comparing oscillations in active energy with an inferred estimate of oscillations in the grid frequency.
[00137] The result, that is, the positive contribution, the negative contribution or no contribution, and the extent or magnitude of the contribution is then at the exit of the output device 40 whereby the operator can take appropriate action. The nature of the phase relationship between mains voltage fluctuations and active energy fluctuations is described below with reference to Figures 4A and 4B, which specify as a generator of the grid subsystem.
[00138] Figure 3 shows a method for the contribution of a network subsystem of 12 to fluctuations in the frequency of the network in an external electrical network 14 in an electrical energy network 10. The method includes receiving a first quantity 42 from a processor 36 .
[00139] The first quantity corresponds to fluctuations in the network frequency in the network subsystem 12. This is the first quantity that can be used to determine fluctuations in the network frequency in the network subsystem. However, it should be noted that the first quantity may correspond to fluctuations in the external network's mains frequency. This is the first quantity that can be used to determine the fluctuations in the mains voltage in the external mains.
[00140] The first quantity may be the frequency of the network of a voltage waveform in the network subsystem 12 recorded over time. Alternatively, the first quantity can be a measure of the angle, that is, a measure of the phase angle of the voltage. Variations in the first quantity over time are, therefore, representative of the oscillation in the network frequency.
[00141] The method also comprises receiving a second quantity 44 in processor 36.
[00142] The second quantity corresponds to the oscillations of active power transmitted in at least one of the electrical connections 16a, 16b, 16c between the external electrical network 14 and the network subsystem 12. That is, the second quantity can be used to determine the variation of active power over time. The second quantity can be active power derived from the voltage and current measurements recorded over time. The person skilled in the art will be aware of how to calculate active power based on the combination of these measures. The second quantity may, alternatively, be a current registered over time. The person skilled in the art will be aware of how to calculate the active power based on any of these measurements. Oscillations in the second quantity over time, therefore, represent variations in the active power, or alternatively, variations in the current.
[00143] The method also comprises the determination of a phase relationship between the first 46 and the second to determine the amount of the second component that contributes to the amount of oscillations in the frequency of the network in the external power grid. This phase relationship can be determined by processor 36. The determination of a phase relationship can comprise determining whether there is a phase difference between the first and second quantities. In addition, processor 36 can be configured to determine whether oscillations of active power lead to oscillations in the frequency of the network between 0 and 180 degrees. In addition, processor 36 can be configured to determine the magnitude of a component of the active energy swings that cause the swings in the network frequency to be 90 degrees.
[00144] If oscillations in active power lead to oscillations in the frequency of the grid in the external power grid 14 between 0 and 180 degrees, then the grid subsystem is contributing negatively to the oscillations in the frequency of the grid in the external power grid 14. That is, the power supply network subsystem is maintaining the oscillation of the network frequency of the external power grid.
[00145] If the oscillations of active power are the oscillations in the frequency of the grid in the external power grid 14, between 0 and 180 degrees, then the grid subsystem is positively contributing to the oscillations in the frequency of the grid in the external power grid 14 In other words, the network subsystem is the extraction of energy in order to dampen fluctuations in the frequency of the network in the external power grid.
[00146] The extent of the positive or negative effect is related to the magnitude of a component of the oscillations of active power that lead or delay oscillations in the frequency of the external mains network, substantially 90 degrees.
[00147] That is, in the case of common mode (for example, frequency fluctuations in the entire phase of a grid subsystem) a phase advance of the active energy fluctuations during fluctuations in the external mains voltage 14 indicates that the network subsystem 12 is contributing to the fluctuations in the frequency of the network in the external electrical network 14 negatively (ie, making it worse).
[00148] The method may also comprise the measurement of the first and / or second quantities. This can be done using the measurement units 18a, 18b, 18c, which provide the measured quantities for processor 36. The frequency oscillation of the network and the active power oscillation can be calculated by means of discrete sequential time analysis measurements of the first quantity and the second quantity, respectively. The analysis can be performed by a measurement unit 18a, 18b, 18c or by the processor 36.
[00149] In some embodiments of the present description, the active power can be measured with a plurality of electrical connections 16a, 16b, 16c between the network subsystem 12 and the external electrical network 14. The plurality of measurements of active power can be made by PMU 18a, 18b and 18c, respectively, and transported to the central processor via communications links (not shown).
[00150] If a plurality of measurements of the active power is made from electrical connections 16a, 16b, 16c, then the central processor 36 can be configured to calculate (or extract) a plurality of oscillations of active power, a corresponding at each electrical connection 16a, 16b, 16c. The second quantity can comprise a sum of all the calculated values of oscillations in the active power. In this case, the energy flow convention from the network subsystem 12 to the external electrical network 14 being positive is used. The central processor 36 can also be further configured to determine the contribution of the network subsystem 12 in the manner described above, using the active powers added for the second quantity.
[00151] In alternative embodiments, a plurality of second quantities may comprise the plurality of oscillations calculated in active power. The central processor 36 can therefore be configured to determine a plurality of phase relationships. In some embodiments, the central processor can be configured to determine a plurality of amplitudes of active energy oscillation components, which is in quadrature of oscillations in the network frequency. The central processor can also be configured to determine the contribution of the network subsystem to oscillations in the frequency of the network adding the plurality of magnitudes of the components of oscillations of active energy that are in quadrature with oscillations in the frequency of the network.
[00152] This method provides an indication as to whether the first network subsystem 12 is contributing positively or negatively to the stability of fluctuations in the frequency of the network in the power grid and in the measure of the contribution.
[00153] In other embodiments of the present invention, the electrical power network may comprise a plurality of network subsystems. In such realizations, the contribution of each grid subsystem to the fluctuations in the grid frequency in the external power grid can be determined according to the method described above.
[00154] In such cases, the magnitude of the contribution of each network subsystem will be different. The magnitude of the contribution of one network subsystem will be greater than the magnitude of the contribution of the other network subsystems.
[00155] Applicants have already realized that it is advantageous when a plurality of network subsystems are contributing to fluctuations in the frequency of the network in an external electrical network to determine the contribution of each network subsystem in relation to the other network subsystems. Therefore, in the event that a first network subsystem has the largest magnitude of the contribution to the network frequency fluctuations, then a magnitude of the contribution of a second (and subsequent) network subsystem is normalized to the contribution of the first subsystem network.
[00156] That is, the magnitude of the contribution of the first network subsystem is normalized to 1 and the magnitude of the contributions of the other subsystems of the network is changed to be a value between -1 and 1. For example, if the magnitude of the contribution of the second network subsystem is half the magnitude of the contribution of the first network subsystem, then the normalized values of the magnitude of the contributions of the first and second network subsystems would be 0.5 and 1, respectively. As an additional example, if the magnitude of the contribution of the second network subsystem is half the magnitude (and negative, that is, in the opposite direction), the contribution of the first network subsystem, then the normalized values of the magnitude of contributions of the first and second network subsystems would be -0.5 and 1, respectively.
[00157] In some embodiments of the present invention, the second (and subsequent) network subsystems are considered to be contributing to the network frequency oscillations in the external power grid if the normalization of the contribution amplitude is 0.5 or higher. That is, the contribution of a network subsystem of oscillations in the frequency of the network in an external electrical network is only considered significant if the normalized magnitude of the contribution of the network subsystem is 0.5 or higher.
[00158] Figure 4A shows 50 oscillations in the network frequency 52 by means of the dotted line and oscillations in active energy 54 by means of the solid line against time. The frequency fluctuations of the network at points 52 are shown as deviation from the network frequency, which in the present case is 60 Hz. That is, 0 Hz in figure 4A represents a network frequency of 60 Hz. The active energy fluctuations graph 54 is also rectified to show oscillations in active power around 0 MW. Thus, the graphs in Figure 4A only show the oscillation in the mains frequency and active power over time, and not the steady state components that are caused by the oscillation in the mains frequency. As can be seen, the graph of active power delays the graph in relation to the grid frequency, which is indicative of the generator responding to the oscillation in the grid frequency.
[00159] Figure 4B shows points 60 of oscillations in the frequency network 62 by means of the dotted line and oscillations of active energy 64 by means of the solid line against time. As with Figure 4A, the graphs in Figure 4B are detached such that they only show the oscillations of the grid frequency and active power over time, and not the steady state components that are caused by the grid oscillation. As can be seen, the oscillations of the active energy portion take the frequency points, which is an indication that the generator contributes to the oscillation in the grid frequency.
[00160] The person skilled in the art will appreciate that the measurement units (PMU) 18a, 18b, 18c are not essential. The magnitude of the contribution of a network subsystem can be determined by determining the phase relationship between the first quantity and the second quantity measured by a PMU. Measurements of the first and second quantities can be provided to the processor 36, by other parts or means. For example, measurements of frequency and active power can be made in other countries or territories by third parties, and transported to central location 32, where the method of the present invention can be performed.
[00161] In addition, in embodiments where a measurement unit is used to measure the first and second quantities of an electrical connection to a network subsystem, a single measurement unit can provide sufficient information to determine whether the network subsystem is contributing to fluctuations in the frequency of the external power grid in a grid. In such embodiments, there is no requirement to summarize the quantities as mentioned above. The phase relationship between the first and second quantity of the unit of measurement is sufficient to determine whether there is a contribution. The magnitude of the contribution can be determined from the magnitude of a component of the oscillations of active energy, which leads to oscillations in the mains voltage of 90 degrees.
[00162] Referring to Figure 5 ac, a series of screens are shown that can be emitted by device 40. The screens show maps of different regions with network subsystems 92, 94, 96, 98 and various electrical connections for the subsystems of network. The arrows are shown on the electrical connections. The size of each arrow corresponds with the magnitude of a contribution from the network subsystem 12 to fluctuations in the frequency of the network in the external electrical network 14.
[00163] Referring to Figure 5a, the unshaded hexagon 90 indicates a measurement of the oscillation frequency of a network subsystem. This oscillation in the frequency is defined as the phase reference, that is, 0 degrees. Shaded hexagons 92 and 94 represent oscillation frequency measurements in opposite phase to reference 90, in an external electrical network.
[00164] Thus, referring to figure 2, the non-shaded hexagon 90 may be within the network subsystem 12 and the shaded hexagons 92, 94 may be within the external electrical network 14.
[00165] The electrical connection 100 has arrows 102, 104 displayed on top of it. Arrow 102 represents the influence of variations in active power in oscillations in the frequency of the external mains network. The arrow 104 represents the influence of oscillations of active power in the electrical connection 100 on the oscillations in the frequency of the grid in the grid subsystem. The size of the arrows 102, 104 is determined, first, the determination of a phase relationship between the oscillation in the network frequency of the external power grid or the grid subsystem and the oscillation of active power carried on the electrical connection 100. The the size of the arrows 102, 104 can correspond to the magnitude of the component of the active energy oscillations that take the oscillations of the network frequency in the shaded and shadowless groups respectively, by substantially 90 degrees.
[00166] Referring to Figure 5b, electrical connections 106, 108 both connected to a network subsystem 12. The network subsystem 12 has a measure of the fluctuations in the network frequency recorded within subsystem 96. Arrows 110, 112 are displayed on connections 106, and arrows 114, 116 are displayed on connection 108. The size of the arrows is determined as described above, and represents the magnitude of the contribution of the network subsystem 12 to the oscillations in the external electrical network.
[00167] Therefore, the sum of the arrows 121 (negative) and 116 (positive) shows the contribution of the network subsystem 12 on the external electrical network.
[00168] Specifically, the magnitude of the connection contribution 106 corresponding to an arrow 12 that can be subtracted from the magnitude of the contribution on connection 108 corresponding to an arrow 16, to determine the contribution of the network subsystem 12 on the oscillations in the network frequency of the external electrical network.
[00169] In the example shown in Figure 5b, the grid subsystem 12 is for dampening the oscillations of the grid frequency of the external power grid as a sum of the contributions illustrated by arrows 112 and 116 gives a negative result.
[00170] Referring to Figure 5c, the network subsystem 12 does not contribute to the network frequency oscillations of the external electrical network, as shown by the relative dimensions of arrows 112 and 124, which illustrate the contributions of the network subsystem, that are substantially the same.
[00171] The present invention allows the determination and presentation of: network subsystems, regions or units that contribute to an oscillation in the frequency of the network in an external electrical network, and the transmission corridors or connections where the energy oscillations are influencing the fluctuations in the mains frequency of the external power grid. The operator of an electric power network can then identify the network subsystem, for example, generator or group of generators, contributing to fluctuations in the frequency of the network and generation of forwarding in the network in such a way that the energy is reduced in the connection relevant.
[00172] The person skilled in the art will be able to identify other embodiments of the invention without departing from the scope of the attached claims.

权利要求:
Claims (20)
[0001]
1. METHOD OF DETERMINING THE CONTRIBUTION OF A NETWORK SUBSYSTEM (12) TO SWITCHES IN NETWORK FREQUENCY on an external electrical network (14) on an electrical energy network (10), characterized by understanding: receiving (42) a first quantity corresponding to fluctuations in the mains frequency (10) in the external electrical network (14); receiving (44) at least a second quantity, at least a second quantity corresponding to oscillations in the active power transmitted in at least one electrical connection (16a, 16b, 16c) between the network subsystem (12) and the external electrical network ( 14); and determining (46) at least one phase relationship between the first quantity and at least a second quantity to determine the component of the second quantity that contributes to the fluctuations in the frequency of the network (10) in the external electrical network (14).
[0002]
2. METHOD, according to claim 1, characterized in that it further comprises determining the magnitude of the component of the second quantity that is squaring with the first quantity.
[0003]
METHOD, according to claim 1, characterized in that the first quantity comprises oscillations in the frequency of the network (10) in the network subsystem (12).
[0004]
4. METHOD, according to claim 3, characterized in that it also comprises receiving a third quantity comprising oscillations in the frequency of the network (10) within the external electrical network (14).
[0005]
5. METHOD, according to claim 4, characterized in that it also comprises the measurement of the first quantity inside the network subsystem (12), measuring the second quantity over at least one electrical connection (16a, 16b, 16c) for the network subsystem (12) and measuring the third quantity within the external electrical network (14).
[0006]
6. METHOD, according to claim 5, characterized in that it further comprises determining whether oscillations in the frequency of the network (10) in the network subsystem (12) are, in common mode, for oscillations in the frequency of the network (10) in the network external electrical (14) depending on the frequency of the first quantity being less than 0.1 Hz.
[0007]
7. METHOD, according to claim 4, characterized by further comprising determining whether oscillations in the frequency of the network (10) in the subsystem of the network (12) are, in common mode for oscillations in the frequency of the network (10) in the electrical network external (14) depending on the first quantity being the same amplitude and phase as the third quantity.
[0008]
METHOD according to any one of claims 6 to 7, characterized in that it further comprises determining the magnitude of a component of the second quantity that conducts the phase of the first quantity by 90 degrees.
[0009]
9. METHOD, according to any of claims 3 to 8, characterized in that it further comprises determining whether oscillations in the frequency of the network (10) in the network subsystem (12) are in phase opposition for oscillations in the frequency of the network (10) in the external electrical network (14) depending on the frequency of the first quantity being greater than 0.2 Hz.
[0010]
10. METHOD, according to claim 4, characterized by further comprising determining whether oscillations in the frequency of the network (10) in the network subsystem (12) are in phase opposition to oscillations in the frequency of the network (10) in the external electrical network (14) depending on the first quantity, being 180 degrees out of phase for the third quantity.
[0011]
Method according to any one of claims 9 to 10, characterized in that it further comprises determining a magnitude of a component of the second quantity which slows down the phase of the first quantity by 90 degrees.
[0012]
METHOD according to any one of claims 1 to 11, characterized in that the at least one electrical connection (16a, 16b, 16c) comprises a plurality of electrical connections (16a, 16b, 16c) between the network subsystem (12 ) and the external electrical network (14), and in which the second quantity corresponds to a sum of the oscillations of the active power transmitted in each of the plurality of electrical connections (16a, 16b, 16c).
[0013]
13. METHOD according to any of claims 1 to 11, characterized in that the at least one electrical connection (16a, 16b, 16c) comprises a plurality of electrical connections (16a, 16b, 16c) between the network subsystem (12) and the external electrical network (14), and in which receiving at least a second quantity comprises receiving a plurality of second quantities, each second quantity corresponding to oscillations in the active power transmitted in one of the plurality of electrical connections (16a, 16b, 16c) , and wherein determining at least one phase relationship comprises determining a plurality of phase relationships between the first quantity and the second plurality of quantities to determine the components of the plurality of second quantities that contribute to fluctuations in the network frequency (10) on the external electrical network (14).
[0014]
14. METHOD, according to claim 13, characterized by further comprising the determination of the magnitudes of the components of the second quantities, which are in quadrature with the first quantity.
[0015]
15. METHOD FOR DETERMINING THE CONTRIBUTION OF A NETWORK SUBSYSTEM (12) FROM A NETWORK SUBSYSTEM PLURALITY TO SWITCHES IN THE NETWORK FREQUENCY on an external electrical network (14) on an electrical power network (10), the method characterized by comprising: determining the contribution of a first network subsystem (12) of the plurality of network subsystems, as defined by any one of claims 1 to 14; determining the contribution of a second network subsystem, as defined by any one of claims 1 to 14, wherein the magnitude of the contribution of the first network subsystem (12) is greater than the magnitude of the contribution of the second network subsystem, and normalize the magnitude of the second network subsystem to the magnitude of the first network subsystem (12).
[0016]
16. METHOD, according to claim 15, characterized by further comprising the determination that the second network subsystem is contributing to oscillations in the frequency of the network (10) in the external electrical network (14) if the normalized magnitude of the second subsystem network is 0.5 or more.
[0017]
17. APPARATUS to determine the contribution of a network subsystem (12) to oscillations in the frequency of the network in an external electrical network (14) in an electrical energy network (10), the device characterized by comprising: a processor (36) configured to receive a first quantity corresponding to the fluctuations in the network frequency (10) in the external electrical network (14), to receive at least a second quantity, to at least a second quantity corresponding to fluctuations in the active power transmitted in at least one electrical connection (16a, 16b, 16c) between the network subsystem (12) and the external electrical network (14), and determining at least one phase relationship between the first quantity and at least a second quantity to determine the component of the second quantity which contributes to fluctuations in the network frequency (10) in the external electrical network (14).
[0018]
18. Apparatus according to claim 17, characterized in that it also comprises a first measurement unit (18a, 18b, 18c) in communications connection with the processor (36) and for at least one electrical connection (16a, 16b, 16c ) for the network subsystem (12), the first measurement unit (18a, 18b, 18c) arranged to measure the first and / or second quantities and supply them to the processor (36).
[0019]
19. Apparatus according to claim 18, characterized in that the first measurement unit (18a, 18b, 18c) comprises a phasor measurement unit.
[0020]
20. ELECTRICAL NETWORK (10), characterized by comprising the apparatus, as defined by any one of claims 17 to 19.

类似技术:

---

公开号 | 公开日 | 专利标题

---

BR112012012712B1|2021-02-23|method of determining the contribution of a network subsystem to oscillations in the frequency of the network, device and electrical network

---

Sarmadi et al.2015|Inter-area resonance in power systems from forced oscillations

---

TWI404292B|2013-08-01|Method of determining a service phase of an endpoint device in a power distribution system

---

Rietveld et al.2015|Measurement infrastructure to support the reliable operation of smart electrical grids

---

Tsai et al.2007|Frequency sensitivity and electromechanical propagation simulation study in large power systems

---

Artale et al.2017|Smart interface devices for distributed generation in smart grids: The case of islanding

---

Gallo et al.2013|Low cost smart power metering

---

US9425650B2|2016-08-23|Systems, methods, and devices for control of multimode UPS

---

Frankie et al.2013|PMU data validation at ISO New England

---

KR100824515B1|2008-04-22|Apparatus and method for computing digital electricpower system

---

Rodrigues et al.2016|A low cost prototype of a Phasor Measurement Unit using Digital Signal Processor

---

Amin et al.2012|Wide area measurement system for smart grid applications involving hybrid energy sources

---

Rajeev et al.2016|Notice of Violation of IEEE Publication Principles: Applications of PMU in renewable energy generation

---

Antunes et al.2017|Voltage sag detection methods based on synchronized phasor measurements using rtds

---

Roscoe et al.2009|Measurement, control and protection of microgrids at low frame rates supporting security of supply

---

Xia2009|Frequency monitoring network | algorithm improvements and application development

---

Morales et al.2018|Statistical assessment of the impact of renewable energy sources on transient stability

---

CN108663601A|2018-10-16|A kind of distribution network failure current management method based on IIDG

---

JP5903143B1|2016-04-13|Disconnection detection apparatus and method

---

Brijesh et al.2018|Synchrophasors evaluation and applications

---

Vrkic et al.2016|Real Time Power Swing Monitoring In a Hydro Power Plant Supported by Synchronized Measurements

---

BR102019010033A2|2020-12-01|MODULAR ENERGY QUALITY MEASUREMENT EQUIPMENT FOR MEDIUM VOLTAGE REGULATORS AND MODULAR DATA PROCESSING SYSTEM WITH MULTIPLE FUNCTIONALITIES

---

Götz et al.2015|A grid-tie micro-inverter software development based on a low cost multiprocessor platform

---

Ding et al.2004|Protection and control of networks with distributed generators capable of operating in islanded mode

---

Zhao2018|Performance improvement of wide-area-monitoring-system | and applications development

同族专利:

---

公开号 | 公开日

---

GB0920206D0|2010-01-06|

---

BR112012012712A2|2018-04-17|

---

AU2010320675A1|2012-05-24|

---

US20120232820A1|2012-09-13|

---

ES2698385T3|2019-02-04|

---

WO2011061538A2|2011-05-26|

---

WO2011061538A3|2012-02-02|

---

US9496715B2|2016-11-15|

---

MX2012005175A|2012-07-30|

---

EP2502320B1|2018-10-17|

---

EP2502320A2|2012-09-26|

---

RU2012117530A|2013-12-27|

引用文献:

---

公开号 | 申请日 | 公开日 | 申请人 | 专利标题

---

---

JP3250147B2|1997-10-22|2002-01-28|株式会社日立製作所|Method and apparatus for estimating frequency characteristics of power system|

---

WO2003001645A2|2001-06-22|2003-01-03|Psymetrix Limited|Method of monitoring a high voltage grid power system|

---

EP1737098A1|2005-06-24|2006-12-27|Abb Research Ltd.|Damping electromagnetic oscillations in power system|

---

WO2008122253A1|2007-04-05|2008-10-16|Siemens Aktiengesellschaft|Method and device for determining the contribution to electrical disturbances|

---

US8000914B2|2008-03-04|2011-08-16|Washington State University|Systems and methods for electromechanical oscillation monitoring|

---

CA2763497C|2009-06-11|2016-11-08|Abb Research Ltd.|Improved control of a power transmission system|

---

EP2462673B1|2009-08-06|2016-03-30|ABB Research Ltd.|Power or voltage oscillation damping in a power transmission system|WO2012118768A1|2011-03-01|2012-09-07|Williams Michael Lamar|Method and apparatus for controlling electrical loads to provide positive damping of power grid oscillation|

---

GB201303735D0|2013-03-01|2013-04-17|Psymetrix Ltd|Osdilation analysis method and apparatus|

---

CN103326384B|2013-06-07|2015-04-29|国家电网公司|Stable emergency control method based on call wire double-peak track|

---

GB201312267D0|2013-07-09|2013-08-21|Psymetrix Ltd|Method of determining a condition of an electrical power network and apparatus therefor|

---

CN103346719B|2013-07-20|2018-11-23|魏强|The method and system of low-frequency oscillation between a kind of elimination generator|

---

US10447040B2|2014-10-15|2019-10-15|Cummins Power Generation Ip, Inc.|Programmable inverter for controllable grid response|

---

US10291025B2|2015-04-22|2019-05-14|General Electric Company|Systems and methods for improved stability of power systems|

---

US10027119B2|2016-05-28|2018-07-17|PXiSE Energy Solutions, LLC|Decoupling synchrophasor based control system for multiple distributed energy resources|

---

US10599175B1|2017-02-28|2020-03-24|PXiSE Energy Solutions, LLC|Time synchronized frequency and voltage regulation of electric power balancing areas|

---

US10615604B2|2016-05-28|2020-04-07|PXiSE Energy Solutions, LLC|Decoupling synchrophasor based control system for distributed energy resources|

---

US10452032B1|2016-09-08|2019-10-22|PXiSE Energy Solutions, LLC|Optimizing power contribution of distributed energy resources for real time power demand scheduling|

---

US10990072B2|2017-11-28|2021-04-27|PXiSE Energy Solutions, LLC|Maintaining power grid stability using predicted data|

---

CN109378817B|2018-10-23|2021-09-21|国网天津市电力公司电力科学研究院|Stability evaluation method based on primary frequency modulation|

---

CN109462227A|2018-10-23|2019-03-12|国网天津市电力公司电力科学研究院|One kind being based on primary frequency modulation rapidity evaluation method|

---

US11056912B1|2021-01-25|2021-07-06|PXiSE Energy Solutions, LLC|Power system optimization using hierarchical clusters|

法律状态:
2019-01-08| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

---

2019-09-03| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

---

2019-12-10| B25G| Requested change of headquarter approved|Owner name: PSYMETRIX LIMITED (GB) |

---

2020-10-06| B06A| Notification to applicant to reply to the report for non-patentability or inadequacy of the application [chapter 6.1 patent gazette]|

---

2020-12-29| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

---

2021-02-23| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 10 (DEZ) ANOS CONTADOS A PARTIR DE 23/02/2021, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

---

申请号 | 申请日 | 专利标题

---

GBGB0920206.0A|GB0920206D0|2009-11-18|2009-11-18|An electrical grid and method therefor|

---

GB0920206.0|2009-11-18|

---

PCT/GB2010/051922|WO2011061538A2|2009-11-18|2010-11-18|A grid oscillation analysis method and apparatus therefor|

---