• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Method and control system for an electronic converter (1) connected to a power source (2). With the method, a reference current is calculated for a loop that controls the current exchanged between the source (2) and the converter (1), and for this, said exchanged current is measured and the voltage of the source (2) is measured. Calculate the voltage in a virtual impedance series from the measured current, a virtual voltage as the measured voltage minus said calculated voltage, a virtual current through a virtual impedance parallel to a branch formed by the virtual impedance series and the source ( 2), and an error as the difference between the virtual voltage and a reference voltage, and the error is applied as an input for a given controller. The reference current is calculated as the sum of the output of said controller and the virtual current. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2641304A1
    申请号:ES201630590
    申请日:2016-05-06
    公开日:2017-11-08
    发明作者:Iñigo ARTIEDA EZCURRA；David BARRICARTE RIVAS；Roberto Gonzalez Senosiain；Luis Marroyo Palomo；Pablo Sanchis Gurpide；Andoni URTASUN ERBURU
    申请人:Ingeteam Power Technology SA；
    IPC主号:
    专利说明:

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    Method and control system to control the voltage of an electronic converter connected to a power source or storage system
    TECHNICAL SECTOR
    The present invention relates to a voltage control method and system for an electronic converter connected to a power source or a storage system.
    PREVIOUS STATE OF THE TECHNIQUE
    The energy sources or storage systems are connected to the electricity grid, or to the consumptions, through electronic converters. The energy sources can be, for example, a photovoltaic generator, a fuel cell or a wind generator. Storage systems can be, for example, batteries or electrolysers.
    For the correct operation of an energy source or storage system, it is sometimes necessary to control the operating voltage of the energy source or storage system. If this control is necessary, when the power source or storage system is connected to an electronic converter, the voltage is controlled by the converter. For example, during the final process of charging a battery, it is necessary to control the voltage of the battery and this control is performed by the electronic converter to which it is connected. For this, in converters it is common to implement at least one voltage control loop.
    Energy sources or storage systems can have a variable impedance and, sometimes, of unknown value, which can modify the dynamics of the electronic converter voltage control loop, becoming too slow or fast and even unstable under certain circumstances. Figure 1 shows the electronic converter connected to a power source or storage system.
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    The impedance of the Jan ^ a source or storage system can vary over a wide range. Among the factors that can vary the impedance are the following:
    • The source's own technology or storage system, for example, batteries (lead-acid, lithium-ion, nickel-cadmium), photovoltaic generators (monocrystalline silicon, polycrystalline silicon, cadmium telluride) or fuel cells (membrane proton exchange, methanol, alkaline).
    • The configuration used, for example, in the case of batteries or fuel cells, the number of cells in series and in parallel. In the case of photovoltaic generators the number of cells in series and in parallel. In the case of wind turbines, the voltage and current levels of the electric generator.
    • Aging, which generally causes an increase in the impedance of the energy source or storage system.
    • The operating point, since the response of the system sometimes depends on the operating voltage.
    • Environmental conditions can also have a strong influence on the impedance value.
    To avoid the effect of the variation of the impedance on the voltage control, a control that is robust to such variations must be designed. The state-of-the-art solutions propose an adaptive control that, using complex algorithms, estimates the impedance of the energy source or storage system and uses this value to update the parameters of the controller used in the control loop (a proportional controller integral or PI for example). This adaptive control method reduces the effect of the impedance variation but increases the complexity of its implementation, since the estimation of the impedance is complicated and also the parameters of the controller must be modified in real time. An example of this method is shown in the document "D. Pavkovic, M. Lobrovic, M. Hrgetic, A. Komljenovic, V. Smetko. Battery Current and Voltage Control System Design with Charging Applications. 2014 IEEE Conference on Control Applications, 1133-1138, 2014 ".
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    EXHIBITION OF THE INVENTION
    The object of the invention is to provide a control method and system for controlling the voltage of an electronic converter connected to a power source or storage system, as described in the claims.
    With the control method a reference current is determined for a current control loop with which the current exchanged between the energy source or storage system and the electronic converter is controlled. To calculate said reference current, the method comprises the steps of:
    - measure the current exchanged between the energy source or storage system and the electronic converter,
    - measure the voltage at terminals of the power source or storage system or of the electronic converter,
    - calculate the voltage in a series virtual impedance, in series with the energy source or storage system, from the measured current,
    - calculate a virtual voltage as the measured voltage minus the voltage calculated in the series virtual impedance,
    - calculate, considering the virtual voltage, a virtual current through a parallel virtual impedance, parallel to a branch formed by the serial virtual impedance and the energy source or storage system,
    - calculate a voltage error such as the difference between the virtual voltage and a given reference voltage,
    - apply the voltage error as input for a controller comprising previously determined parameters, and
    - calculate the reference current as the sum of the output of said controller and the virtual current through the parallel virtual impedance.
    With the method of the invention, the dynamics of the practically invariant control loop are maintained for the entire possible range of variation of the impedance of the energy source or storage system, in addition to a great robustness in the face of the variation of the parameters of said source of energy or storage system. Thus, with the method of the invention a simple voltage control is obtained, since it does not require for example an estimation of the impedance of the energy source or storage system, and at the same time robust against
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    Large variations in the impedance of the Jan ^ a source or storage system. With the proposed control, in addition, the dynamic characteristics remain practically constant regardless of the value of said impedance, which allows to guarantee stability, extend the useful life of the elements (in the case of storage systems) or extract a greater energy ( in the case of energy sources). In addition, in the case of an analog implementation, this is greatly simplified while, in the case of a digital implementation, with the control executed in a microprocessor, the computational cost will be considerably reduced.
    These and other advantages and features of the invention will become apparent in view of the figures and the detailed description of the invention.
    DESCRIPTION OF THE DRAWINGS
    Figure 1 shows the modeling of an electronic converter as a controlled current source.
    Figure 2 shows a block diagram that generically depicts an embodiment of voltage control, which includes an internal current loop and the impedance of the energy source or storage system.
    Figure 3 shows an equivalent electrical circuit with the virtual impedances that are emulated in a preferred embodiment of the method of the invention.
    Figure 4 shows a block diagram representative of the electrical circuit of Figure 3, including the controller.
    Figure 5 shows a block diagram corresponding to the control of a preferred embodiment of the method of the invention.
    Figure 6 shows the block diagram of Figure 5, including an internal current loop and the impedance of the energy source or storage system.
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    Figure 7 shows a representative electrical circuit of the block diagram of Figure 6.
    Figure 8a shows the result of the simulation with a control method without emulation of virtual impedances and with a controller of fixed parameters, against a step in the reference voltage for three different situations of resistance of a battery as a storage system.
    Figure 8b shows the simulation result with an embodiment of the control method of the invention, compared to a step in the reference voltage for three different situations of resistance of a battery as a storage system.
    DETAILED EXHIBITION OF THE INVENTION
    The method of controlling the invention is adapted to control the voltage of an electronic converter 1 connected to a power source or storage system 2. The power source 2 can be of different types, such as an installation where the power is generated. energy (solar or wind installation for example), a storage system such as a battery, a capacitor bank or, for example, an electrolyzer.
    The control method includes a current control of the energy source or storage system 2, by means of a determined current control loop, and is executed on the electronic converter 1 connected to said energy source or storage system 2. in this way, the electronic converter 1 behaves as a controlled current source for said energy source or storage system 2. The control method is adapted to control the voltage, so it also includes a voltage control loop, which also determines a reference current for the current control loop. Thus, the voltage control is the external loop of the control method and with it the reference current for the internal current loop is obtained.
    In a generic way, the external voltage loop can be represented, for example, by the scheme in Figure 2. From a predetermined voltage reference (voltage setpoint) and voltage and current feedback, the control method obtains the current reference for the internal current loop. From the current reference, there are several
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    ways of performing current control, which is beyond the scope of the present invention. In any case, in the method it is considered that the dynamics of the current loop is much superior to that of the voltage loop, so the transfer function of the current loop can be taken as a unit when analyzing the current loop. tension. The current also causes a change in voltage. The relationship between the current and the voltage of the energy source or storage system 2 is called the plant.
    The relationship between the current and the voltage in the energy source or storage system 2 is determined by an expression that, in general, can be an implicit, non-linear and dynamic function. This relationship can be linearized around the work point obtaining the relation in small signal, which will be equal to the impedance of the energy source or storage system 2 in small signal, with a negative sign due to the use of the generating agreement, v = -Z (s) • i.
    To limit the effect of plant variability, the presence of an impedance ZS (s) in series with the impedance Z (s) of the energy source or storage system 2 is emulated in the control method, and at its instead, an impedance ZP (s) in parallel with the set ZS (s) in series with Z (s), as shown in Figure 3 (although an impedance ZS (s) in series equal to series could be emulated zero).
    The method comprises a controller C (s) with previously determined parameters, and the plant that sees the controller C (s) is modified with respect to the case without emulating impedances, and the relationship becomes vv = -Zeq (s) • iv, where
    Zlt (s) = Zr (s) f / (Z (s) + Zs (s)) =
    Zp (s) jZ (s) + Zs (s)) Zp (5) + Z (5) + Zs (s)
    vv being the virtual voltage between terminals of the emulated parallel impedance ZP (s), and iv being the virtual current or controller output.
    The equivalent circuit of the proposed control method and the modeling of the current control loop LCi and the plant is shown in Figure 4.
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    For frequencies close to the desired cut-off frequency for the voltage loop, choosing the value of the emulated parallel impedance ZP (s) sufficiently less than the sum of the minimum impedance Z (s) = Zmin (s) that may have The energy source or storage system 2 plus the emulated impedance ZS series (s), the following approximation can be made:
    image 1
    In this way, the plant seen by the controller will be equal to the parallel emulated impedance ZP (s), whose value is constant and known, and the effect of the variability and uncertainty of the impedance of the energy source is eliminated. or storage system 2 over the control.
    In this way, controller C (s) can be parameterized for the desired dynamic and stability margin characteristics, taking into account that the plant approaches ZP (s). The C (s) controller can be a simple controller, such as an integral controller, a proportional-integral PI controller, a proportional-integral-derivative PID controller, although it could also be any other type of controller.
    For example, if a power source or storage system varies its impedance from a minimum value Z (s) = Zmin (s) to a maximum value Z (s) = 100Zmin (s), if the control method is not used of the invention, the system will see the previous variation significantly affecting the dynamics of the control. However, with the proposed control method, if, for example, a value ZP (s) = Zmin (s) + ZS (s) is taken, the variation range of the plant will be from Zp (s) / 2 to Zp (s), which significantly reduces the variations in the dynamics of the control.
    Thanks to the emulation of at least one virtual impedance, the voltage control behaves as desired in the entire possible operating range.
    The emulation of the impedance series ZS (s), causes that the control is carried out on the tension
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    virtual vv instead of over the actual voltage v measured at terminals of the power source or storage system 2. Therefore, in permanent regime and depending on the type of impedance Zs (s), it is possible that voltage v real does not equal the reference voltage. In fact, in permanent regime you have to:
    image2
    So that the actual voltage v is equal to the reference voltage v *, a series impedance Zs (s) equal to zero can be emulated (which is the same as not emulating a series impedance Zs (s), or emulating some element that does not have a permanent voltage drop, such as an inductance, that is, ZS (s) = LS s. Both cases are a particular case of the present invention and everything described above remains valid, with the particularity that the voltage v real is exactly equal to the reference voltage in permanent regime.The first option, with ZS (s) = 0, is especially interesting in those applications in which the minimum value of the impedance of the energy source or system Storage 2 is not excessively low.
    However, there are situations in which it may be interesting to emulate a series ZS impedance (s) with permanent voltage drop in the regime, in the event that a certain error can be assumed in the monitoring of the reference voltage. An example of such an application is the case in which the minimum impedance Z (s) = Zmin (s) of the energy source or storage system 2 is very small, so that with ZS (s) = 0, it would require a parallel impedance ZP (s) even less than Zmin (s), which can be problems such as a very high virtual current iZp or an amplification of harmonics. In this case, adding a series ZS impedance (s) allows to increase the value necessary for the parallel impedance ZP (s).
    Next, a detailed description of a preferred embodiment of the method of the invention is described with the aid of Figures 5 to 8. A parallel virtual impedance ZP (s) is formed therein, formed by a resistor RP in series with a capacitor CP. The C (s) controller is a proportional integral PI type controller, and comprises the parameters KP and Ki. The transfer function of this parallel virtual impedance ZP (s) is as follows:
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    image3
    The preferred embodiment applies, for example, to a battery (as storage system 2) connected to an electronic converter 1 which has a current control implemented. The control method by emulating virtual impedances to control the battery voltage comprises the following stages:
    - measure the current i exchanged between the power source or storage system 2 and the electronic converter,
    - measure the voltage v on terminals of the power source or storage system 2 or of the electronic converter,
    - calculate, considering the measured voltage v, a virtual current iZP through a parallel virtual impedance ZP (s), parallel to the energy source or storage system 2,
    - calculate a voltage error such as the difference between the measured voltage v and a given reference voltage, and
    - apply the voltage error as input for a controller C (s) comprising previously determined parameters, and
    - calculate the reference current as the sum of the output of said controller C (s) and the virtual current iZP through the parallel virtual impedance ZP (s).
    This combination of stages is shown schematically in Figure 5. The voltage loop, including both the control proposal and the plant, is shown in Figure 6, where it is assumed that the battery has a resistive impedance around the frequency of tension loop cutting. In the same way, the equivalent circuit of the plant seen by the controller is shown in Figure 7.
    In some embodiments, as in the preferred embodiment for example, the voltage and current measurements i are filtered before considering them for the different calculations, to eliminate high frequency noises.
    A control method has been simulated without virtual impedance emulation and with a fixed parameter controller (figure 8a), and the proposed control method (figure 8b), each
    one of them for three situations with a very different battery resistance. The results are shown in Figures 8a and 8b respectively, for a reference voltage step of 130 to 132 V, in the case of Rbat = Rmin = 10 mQ (v1 in Figures 8a and 8b), Rbat = 100 mQ ( v2 in Figures 8a and 8b) and Rbat = Rmax = 1 Q (v3 in Figures 8a and 8b), 5 Rbat being the battery resistance. It can be observed that, while with the control method without virtual impedance emulation and with a fixed parameter controller the dynamics of the tension control is very variable, with the proposed control the dynamics is practically invariant.
    权利要求:
    Claims (11)
    [1]
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    1. Control method to control the voltage of an electronic converter connected to a power source or storage system, with which a reference current is calculated for a current control loop with which the current exchanged between the energy source or storage system (2) and the electronic converter, characterized in that to calculate said reference current the method comprises the steps of:
    - measure the current (i) exchanged between the energy source or storage system (2) and the electronic converter,
    - measure the voltage (v) on terminals of the power source or storage system (2) or of the electronic converter,
    - calculate the voltage (vzs) in a virtual series impedance (ZS (s)), arranged in series with the energy source or storage system (2), from the measured current (i),
    - calculate a virtual voltage (vv) as the voltage (v) measured minus the calculated voltage (vzs) in the series virtual impedance (ZS (s)),
    - calculate, considering the virtual voltage (vv), a virtual current (iZP) through a parallel virtual impedance (ZP (s)), parallel to a branch formed by the series virtual impedance (ZS (s)) and the source of energy or storage system (2),
    - calculate a voltage error such as the difference between the virtual voltage (vv) and a given reference voltage, and
    - apply the voltage error as input for a controller (C (s)) comprising previously determined parameters,
    the reference current is calculated as the sum of the output of said controller (C (s)) and the virtual current (iZP) through the parallel virtual impedance (Zp (s)).
    [2]
    2. Control method for controlling the voltage of an electronic converter according to claim 1, wherein the voltage in the series virtual impedance (ZS (s)) is equal to zero.
    [3]
    3. Control method to control the voltage of an electronic converter according to
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    any of the preceding claims, wherein the controller is of integral, proportional integral (PI) or proportional integral derivative (PID) type.
    [4]
    4. Control method for controlling the voltage of an electronic converter according to any of the preceding claims, wherein the voltage (v) and current (i) measurements are filtered before considering them for the different calculations, where the filter used is a Low pass filter, high pass or a combination of both.
    [5]
    5. Control method for controlling the voltage of an electronic converter according to any of the preceding claims, wherein the calculation of the reference current is performed in analog or digital form.
    [6]
    6. Control method for controlling the voltage of an electronic converter according to any of the preceding claims, wherein a parallel virtual impedance (ZP (s)) is chosen such that for frequencies close to the desired cutoff frequency for the loop of voltage, said parallel virtual impedance (ZP (s)) is sufficiently smaller than the sum of the minimum impedance of the energy source or storage system (2) plus the serial virtual impedance (ZS (s)).
    [7]
    7. Control system for controlling the voltage of an electronic converter connected to a power source or storage system, characterized in that it is adapted to support a control method according to any of the preceding claims.
    [8]
    8. Control system for controlling the voltage of an electronic converter connected to an energy source or storage system according to claim 7, wherein the power source (2) is a photovoltaic generator, a fuel cell, a wind turbine or a wind turbine connected to a diode bridge.
    [9]
    9. Control system for controlling the voltage of an electronic converter connected to a power source or storage system according to claim 7, wherein the storage system (2) is a battery, a capacitor or an electrolyzer.
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    [10]
    10. Control system for controlling the voltage of an electronic converter connected to a power source or storage system according to any of claims 7 to 9, wherein the virtual impedances (ZP (s), ZS (s)) emulate resistors , capacitors, inductances or any combination of them.
    [11]
    11. Control system for controlling the voltage of an electronic converter connected to an energy source or storage system according to any of claims 7 to 10, wherein the energy source or storage system (2) is an element that is You can model with a relationship between voltage and current of type v = -Z (s) • i, where the impedance Z (s) of the energy source or storage system (2) is variable and / or not known exactly.
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    同族专利:
    公开号 | 公开日
    ES2641304B1|2018-09-06|
    引用文献:
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    CN105305410A|2015-10-16|2016-02-03|国网上海市电力公司|DC distribution system energy storage device adaptive virtual impedance droop control method|ES2805174A1|2019-08-09|2021-02-10|Ingeteam Power Tech Sa|Voltage control method for an electrical power system |
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    申请号 | 申请日 | 专利标题
    ES201630590A|ES2641304B1|2016-05-06|2016-05-06|Method and control system to control the voltage of an electronic converter connected to a power source or storage system|ES201630590A| ES2641304B1|2016-05-06|2016-05-06|Method and control system to control the voltage of an electronic converter connected to a power source or storage system|
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