Multi-band power grid simulator power distribution optimization method

Abstract

The application provides a multi-band power grid simulator power distribution optimization method, aiming at a power grid simulator for grid-connected converter stability test, comprising: determining the equivalent voltage and equivalent impedance of the simulated power grid; determining the series equivalent item of impedance network A of the current control type converter; obtaining the AC test port voltage; calculating the impedance compensation component according to the equivalent voltage, equivalent impedance, series equivalent item of impedance network A and AC test port voltage; and injecting the impedance compensation component into the modulation signal of the current control type converter. The application improves the power tracking capability of the current control type converter, optimizes the overall power distribution of the multi-band power grid simulator, reduces the overload risk of the voltage control type converter in harsh test conditions such as harmonics and transients, expands the testable power capacity of the multi-band power grid simulator, and is effective in the bandwidth range of the multi-band power grid simulator without complex parameter adjustment or additional hardware support.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and more specifically, to a power allocation optimization method for a multi-band power grid simulator. Background Technology

[0002] With more and more power electronic converters being connected to modern power grids, the stability of the interaction between the converters and the grid is receiving increasing attention. For converters, their grid-connected stability changes with variations in grid impedance conditions, thus requiring verification during actual operation.

[0003] To meet these stability testing requirements, existing research has proposed grid simulators with impedance simulation capabilities. To balance control bandwidth and power capacity, multi-band grid simulators combining current- and voltage-controlled converters have become a competitive technical solution. For example, in the multi-band grid simulator described in patent "202111534978.2; A grid simulator and testing device for grid-connected converter stability testing," the current-controlled converter typically handles the main test power, while the voltage-controlled converter focuses on shaping port characteristics.

[0004] However, due to the low switching frequency and limited control bandwidth of current-controlled converters, they struggle to accurately track harmonics and transient power. For grid simulators employing parallel current- and voltage-controlled converters, in test scenarios with high harmonics and transient power, such as grid-connected resonant conditions, voltage-controlled converters face the risk of overload damage, while the power capacity of current-controlled converters is not fully utilized. Therefore, it is necessary to optimize the power distribution among parallel current- and voltage-controlled converters.

[0005] Some research has been conducted on the power distribution problem of parallel converters. For parallel systems containing only voltage-controlled converters, abnormal power distribution is generally caused by output voltage mismatch or load impedance mismatch. In the literature "Control of Distributed Uninterruptible Power Supply Systems," output voltage mismatch is corrected by feeding back the output power to adjust the voltage reference value, which is a common droop control method. For load impedance mismatch, the literature "Modeling, Analysis, and Design of Stationary Reference Frame Droop Controlled Parallel Three-Phase Voltage Source Inverters" describes introducing a virtual impedance to correct the power output characteristics.

[0006] However, the above methods are only applicable to parallel systems with multiple voltage-controlled converters, while multi-band grid simulators can include both voltage-controlled and current-controlled converters simultaneously. Furthermore, the improper power allocation in multi-band grid simulators stems from the inability of current-controlled converters to accurately track harmonics and transient power; the root cause is bandwidth mismatch, not voltage or impedance mismatch. The paper "Microgrids Operation Based on Master-Slave Cooperative Control" describes the widespread use of master-slave control for power allocation in parallel systems containing both voltage-controlled and current-controlled converters. However, this method also cannot solve the bandwidth mismatch problem.

[0007] In summary, existing methods are insufficient for optimizing power allocation in multi-band power grid simulators. Summary of the Invention

[0008] In view of one of the defects in the prior art, the purpose of this application is to provide a power allocation optimization method for a multi-band power grid simulator.

[0009] A first aspect of this application provides a power allocation optimization method for a multi-band power grid simulator, specifically for a power grid simulator used for stability testing of grid-connected converters, comprising:

[0010] Determine the equivalent voltage of the simulated power grid v sref and equivalent impedance Z ref (s);

[0011] Determine the series equivalent terms of the impedance network A of the current-controlled converter. Z series (s);

[0012] Obtain the AC test port voltage of the power grid simulator used for grid-connected converter stability testing. v PCC ;

[0013] Based on the equivalent voltage of the simulated power grid v sref and equivalent impedance Z ref (s) The impedance network A series equivalent term of the current-controlled converter Z series (s) and the AC test port voltage of the power grid simulator used for grid-connected converter stability testing. v PCC Calculate the impedance compensation component v cp :

[0014]

[0015] in, v cp This represents the impedance compensation component;

[0016] The impedance compensation component v cp The modulation signal injected into the current-controlled converter is used to optimize the power distribution of the multi-band power grid simulator.

[0017] Optionally, the method further includes:

[0018] The simulated power grid is equivalent to a Thevenin form, and the equivalent port characteristics of the simulated power grid are based on the equivalent voltage. v sref and the equivalent impedance Z ref (s) description.

[0019] Optionally, under typical power grid conditions, the equivalent impedance of the simulated power grid is resistive-inductive.

[0020] Optionally, the AC test port voltage of the grid simulator used for grid-connected converter stability testing... v PCC Equivalent to the equivalent voltage of the simulated power grid v sref With the equivalent impedance Z ref The difference in series voltage drop across (s).

[0021] Optionally, the series equivalent terms of the impedance network A of the current-controlled converter are determined. Z series (s), including:

[0022] If the impedance network A of the current-controlled converter is an L-type filter or an LCL-type filter, the total inductive reactance of the L-type filter or the LCL-type filter is used as the series equivalent term of the impedance network A. Z series (s);

[0023] If the impedance network A of the current-controlled converter is a non-L-type filter and a non-LCL filter, determine the series equivalent term of the impedance network A based on circuit theory. Z series (s).

[0024] A second aspect of this application provides a multi-band power grid simulator, employing the power allocation optimization method for a multi-band power grid simulator as described in any one of the first aspects to achieve power allocation optimization, including:

[0025] Optionally, a current-controlled converter, a current converter controller, a voltage-controlled converter, a voltage converter controller, and an impedance compensation branch;

[0026] The DC side of the current-controlled converter is connected to the first DC power supply port, and the DC side of the voltage-controlled converter is connected to the second DC power supply port. The first DC power supply port and the second DC power supply port are connected to an external DC power supply.

[0027] The AC side of the current-controlled converter and the AC side of the voltage-controlled converter are connected in parallel to form an AC test port, which is used to connect the device under test.

[0028] The current-controlled converter is used to handle the main input power and main output power of the AC side port, and the voltage-controlled converter is used to reproduce the equivalent port characteristics of the simulated power grid.

[0029] The impedance compensation branch is used to adjust the voltage based on the equivalent voltage of the simulated power grid. v sref and equivalent impedance Z ref (s) The impedance network A series equivalent term of the current-controlled converter Z series (s) and the AC test port voltage of the grid simulator used for grid-connected converter stability testing. v PCC Generate impedance compensation component v cp and the impedance compensation component v cp It is injected into the first modulation wave output by the current converter controller.

[0030] Optionally, the current-controlled converter includes a low-frequency switching bridge and an impedance network A, wherein the low-frequency switching bridge and the impedance network A are connected in series, and the impedance network A is used to filter out current ripple.

[0031] The voltage-controlled converter includes a high-frequency switching bridge and an impedance network B, which are connected in series. The impedance network B is used to filter out voltage ripple.

[0032] Optionally, the current converter controller includes a current controller and a low-frequency pulse width modulation module. The current controller transmits the first modulation wave to the low-frequency pulse width modulation module. The current converter controller uses a current control algorithm to control the current-controlled converter to track the AC test port current.

[0033] The voltage converter controller includes a simulated power grid model, a voltage controller, and a high-frequency pulse width modulation module. The simulated power grid model transmits a control reference signal to the voltage controller, and the voltage controller transmits a second modulation wave to the high-frequency pulse width modulation module. The voltage converter controller uses a voltage control algorithm to control the voltage-controlled converter to generate AC test port voltage.

[0034] Optionally, the switching frequency of the voltage-controlled converter is higher than that of the current-controlled converter.

[0035] Optionally, the simulated power grid model is used to describe the port characteristics of the simulated power grid;

[0036] The simulated power grid model adopts the Thevenin form and includes two parameters: equivalent voltage and equivalent impedance.

[0037] The power allocation optimization method for a multi-band power grid simulator in this application utilizes the equivalent voltage and equivalent impedance of the simulated power grid, the series equivalent terms of the impedance network A of the current-controlled converter, and the AC test port voltage of the multi-band power grid simulator to achieve differential-free calculation of the impedance compensation component. This impedance compensation component is then injected into the modulation signal of the current-controlled converter, thereby improving the current-controlled converter's ability to track harmonics and transient power, reducing the overload risk of the voltage-controlled converter under harsh test conditions, and expanding the testable power capacity of the multi-band power grid simulator. Furthermore, this method requires no complex parameter adjustments or the introduction of additional hardware and remains effective throughout the simulation bandwidth of the multi-band power grid simulator.

[0038] Other technical effects resulting from the additional features will be further illustrated in the corresponding embodiments. Attached Figure Description

[0039] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0040] Figure 1 This is a flowchart illustrating a power allocation optimization method for a multi-band power grid simulator according to an exemplary embodiment.

[0041] Figure 2 This is a schematic diagram illustrating the structure of a multi-band power grid simulator according to an exemplary embodiment.

[0042] In the diagram: 1. Current-controlled converter; 2. Low-frequency switching bridge; 3. Impedance network A; 4. Current converter controller; 5. Current controller; 6. Low-frequency pulse width modulation module; 7. Voltage-controlled converter; 8. High-frequency switching bridge; 9. Impedance network B; 10. Voltage converter controller; 11. Simulated power grid model; 12. Voltage controller; 13. High-frequency pulse width modulation module; 14. Impedance compensation branch; 15. AC test port; 16. First DC power supply port; 17. Second DC power supply port. Detailed Implementation

[0043] The present application will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application. These all fall within the protection scope of the present application.

[0044] In the description of the embodiments in this application, "multiple" means two or more, unless otherwise explicitly specified. In this application, unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0045] The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or devices.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0047] In existing technologies, power allocation for parallel converters mainly employs droop control to correct output voltage mismatch or introduces virtual impedance to correct power output characteristics. These methods are only applicable to parallel systems with multiple voltage-controlled converters and not to multi-band grid simulators that simultaneously include both voltage-controlled and current-controlled converters. Existing technologies also utilize master-slave control for power allocation in parallel systems with both voltage-controlled and current-controlled converters, but this method cannot address bandwidth mismatch issues. Based on these problems, this application provides a power allocation optimization method for a multi-band grid simulator to solve these issues.

[0048] Figure 1 This is a flowchart illustrating a power allocation optimization method for a multi-band power grid simulator according to an exemplary embodiment.

[0049] Reference Figure 1 As shown in the figure, one embodiment of this application provides a power allocation optimization method for a multi-band power grid simulator, which is used for the stability testing of grid-connected converters, including steps S11 to S15.

[0050] S11, Determine the equivalent voltage of the simulated power grid. v sref and equivalent impedance Z ref (s).

[0051] S12, determine the series equivalent terms of the impedance network A of the current-controlled converter. Z series (s).

[0052] S13, Obtain the AC test port voltage of the grid simulator used for grid-connected converter stability testing. v PCC .

[0053] The above steps S11 to S13 can be performed simultaneously.

[0054] S14, based on the equivalent voltage of the simulated power grid v sref and equivalent impedance Z ref (s) Series equivalent term of impedance network A of current-controlled converter Z series (s) and the AC test port voltage of the grid simulator used for grid-connected converter stability testing. v PCC Calculate the impedance compensation component v cp :

[0055]

[0056] in, v cp This represents the impedance compensation component.

[0057] S15, impedance compensation component v cp Injecting the modulation signal into the current-controlled converter to achieve power distribution optimization in the multi-band power grid simulator.

[0058] The embodiments described above utilize the equivalent voltage and equivalent impedance of the simulated power grid, the series equivalent terms of the impedance network A of the current-controlled converter, and the AC test port voltage of the multi-band power grid simulator to achieve differential-free calculation of the impedance compensation component. This impedance compensation component is then injected into the modulation signal of the current-controlled converter, thereby improving the current-controlled converter's ability to track harmonics and transient power, reducing the overload risk of the voltage-controlled converter under harsh test conditions, and expanding the testable power capacity of the multi-band power grid simulator. Furthermore, this method requires no complex parameter adjustments or the introduction of additional hardware and remains effective throughout the simulation bandwidth of the multi-band power grid simulator.

[0059] To obtain the equivalent voltage of the simulated power grid v sref and equivalent resistance Z ref (s), in some specific embodiments of this application, the following can be adopted:

[0060] Equivalent voltage of the simulated power grid v sref This is the instantaneous voltage value, used to characterize the voltage behavior of the simulated power grid.

[0061] Equivalent impedance of the simulated power grid Z ref (s) is a complex frequency domain polynomial used to characterize the impedance behavior of the simulated power grid.

[0062] Equivalent voltage of the simulated power grid v sref and equivalent resistance Z ref (s) together describe its port characteristics, which can be obtained through analytical modeling or numerical frequency sweeping. These are known quantities and can be obtained without additional operations.

[0063] In some specific embodiments of this application, for S12, the series equivalent term of the impedance network A of the current-controlled converter is determined. Z series (s) can be S121 or S122.

[0064] S121, If ​​the impedance network A of the current-controlled converter is an L-type filter or an LCL-type filter, the total inductive reactance of the L-type filter or LCL-type filter is used as the series equivalent term of the impedance network A. Z series (s).

[0065] Specifically, if the impedance network A of the current-controlled converter is an L-type filter or an LCL-type filter, then the series equivalent terms of impedance network A will be... Z series (s) is approximately the total impedance of the filter.

[0066] S122, If the impedance network A of the current-controlled converter is a non-L-type filter and a non-LCL-type filter, determine the series equivalent term of the impedance network A based on circuit theory. Z series (s).

[0067] Specifically, if the impedance network A of the current-controlled converter is another filtering structure, then the series equivalent term of the impedance network A can be calculated according to basic circuit theory. Z series (s).

[0068] The series equivalent of impedance network A in this embodiment Z series (s) can be a time-varying or time-invariant complex frequency domain polynomial.

[0069] The embodiments described above in this application comprehensively consider the parameter variations of impedance network A under different operating conditions, and obtain the series equivalent term of impedance network A according to the type of impedance network A. Z series (s) requires no complex parameter adjustments and no additional hardware support.

[0070] To obtain the AC test port voltage v PCC In some specific embodiments of this application, a voltage sensor can be directly used to obtain the AC test port voltage of the multi-band power grid simulator. v PCC Alternatively, other sampling methods can be used to obtain the data.

[0071] In the above embodiments of this application, the grid simulator or other multi-band grid simulator used for grid-connected converter stability testing originally required the use of voltage sensors to measure the AC test port voltage, thus eliminating the need for additional hardware sensor requirements.

[0072] To obtain the differential-free calculation expression for the impedance compensation component, in some specific embodiments of this application, the simulated power grid is equivalent to the Thevenin form, and the equivalent port characteristics of the simulated power grid are represented by the equivalent voltage. v sref and equivalent impedance Z ref (s) description.

[0073] Specifically, within the simulation bandwidth of the multi-band power grid simulator, the simulated power grid model adopts the Thevenin form.

[0074] In some specific embodiments of this application, under typical power grid conditions, the equivalent impedance of the simulated power grid is resistive-inductive.

[0075] Specifically, when the equivalent impedance of the simulated power grid exhibits resistive-inductive characteristics, then the equivalent impedance... Z ref The existence of a differential term in (s) makes it applicable to the power allocation optimization method for the multi-band power grid simulator provided in this application.

[0076] In some specific embodiments of this application, the AC test port voltage of the power grid simulator used for grid-connected converter stability testing is described. v PCC Equivalent to the equivalent voltage of the simulated power grid v sref With equivalent impedance Z ref The difference in series voltage drop across (s) is the equivalent port characteristic.

[0077] Specifically,

[0078]

[0079] in, v PCC Indicates the AC test port voltage. v sref This represents the equivalent voltage of the simulated power grid. i PCC Indicates the AC test port current. Z ref (s) represents the equivalent impedance of the simulated power grid.

[0080] To achieve differential-free calculation of impedance compensation components, in some specific embodiments of this application, for S14, the equivalent voltage of the simulated power grid is used... v sref and equivalent impedance Z ref (s) The impedance network A series equivalent term of the current-controlled converter Z series(s) and the AC test port voltage of the grid simulator used for grid-connected converter stability testing. v PCC Calculate the impedance compensation component v cp S141 to S143 can be used.

[0081] S141, equate the AC test port current to the output current of the current-controlled converter, and determine the impedance compensation component. v cp A new expression.

[0082] Specifically, the new expression for the impedance compensation component is: v cp The equivalent term for AC test port current and impedance network in series Z series The product of (s).

[0083]

[0084] in, v cp Indicates the impedance compensation component. i g_i This indicates the output current of a current-controlled converter. Z series (s) represents the series equivalent term of the impedance network. i PCC This indicates the AC test port current.

[0085] In a grid simulator used for stability testing of grid-connected converters, a current-controlled converter is used to handle the main test power. The main output current of the current-controlled converter is... i g_i It can be approximated as the AC test port current. i PCC .

[0086] Since impedance network A contains inductive elements, such as a typical L-type or LCL-type filter, the series equivalent term of the impedance network... Z series (s) will include a differential element. If the series voltage drop on impedance network A is calculated directly by multiplying the current by the impedance, the series equivalent term of the impedance network will be... Z series The differentiating element in (s) amplifies high-frequency noise, thus the new expression for the impedance compensation component cannot be directly applied.

[0087] This application utilizes the equivalent port characteristics shaped by a power grid simulator to achieve differential-free calculation of the series voltage drop on impedance network A, as detailed below:

[0088] S142, based on the equivalent port characteristics, determine the expression for the AC test port current.

[0089] Specifically,

[0090]

[0091] in, i PCC Indicates the AC test port current. v sref This represents the equivalent voltage of the simulated power grid. v PCC This represents the AC test port voltage of the power grid simulator used for stability testing of grid-connected converters. Z series (s) represents the series equivalent term of the impedance network A of the current-controlled converter.

[0092] S143, substitute the AC test port current expression into the impedance compensation component. v cp A new expression is used to determine the impedance compensation component. v cp .

[0093] Specifically, the equivalent impedance under typical power grid conditions Z ref (s) exhibits resistive-inductive behavior, and the current at the aforementioned AC test port is... i PCC 1 / in the expression Z ref The (s) term has integral characteristics and can be used to cancel the equivalent term of impedance network series. Z series The differential element in (s) can be used to derive the impedance compensation component. v cp The formula for calculating the derivative without differentiation is as follows:

[0094]

[0095] in, v cp Indicates the impedance compensation component. v sref This represents the equivalent voltage of the simulated power grid. v PCC This represents the AC test port voltage of the power grid simulator used for stability testing of grid-connected converters. Z series (s) represents the series equivalent term of the impedance network A of the current-controlled converter. Z ref (s) represents the equivalent impedance. ig_i This indicates the output current of a current-controlled converter. i PCC This indicates the AC test port current.

[0096] In the embodiments described above, the calculation of the impedance compensation component does not depend on the differential operation of voltage or current, thereby avoiding the problem of high-frequency noise amplification.

[0097] To optimize power allocation in a multi-band power grid simulator, in some specific embodiments of this application, for S15, the impedance compensation component... v cp The modulation signal injected into the current-controlled converter is used to counteract the bandwidth limitation of the current-controlled converter by the low-pass characteristic of the impedance network A, thereby achieving power allocation optimization in the multi-band power grid simulator.

[0098] The injection of impedance compensation components is a feedforward control method that improves the power point tracking capability of current-controlled converters without affecting their internal stability.

[0099] In the embodiments described above, the injection of impedance compensation components can effectively improve the tracking capability of current-controlled converters for harmonics and transient power, reduce the overload risk of voltage-controlled converters under harsh test conditions, and expand the testable power capacity of multi-band power grid simulators. Furthermore, the power allocation optimization method does not require complex parameter adjustments or additional hardware support and remains effective within the simulation bandwidth of the multi-band power grid simulator.

[0100] In a multi-band power grid simulator, the impedance network A of the current-controlled converter has low-pass characteristics. Although it can filter out current ripple, it limits the control bandwidth of the current-controlled converter, making it difficult for the current-controlled converter to accurately track harmonics and transient power. The power distribution optimization method for a multi-band power grid simulator provided in this application is to compensate for the series voltage drop on the impedance network A. Its effect is equivalent to removing the impedance network A at the control level, thereby expanding the control bandwidth of the current-controlled converter.

[0101] Figure 2 This is a schematic diagram illustrating the structure of a multi-band power grid simulator according to an exemplary embodiment.

[0102] Reference Figure 2 As shown in the figure, one embodiment of this application provides a multi-band power grid simulator, which uses the power allocation optimization method of the multi-band power grid simulator provided in this application to achieve power allocation optimization, including: a current-controlled converter 1, a current converter controller 4, a voltage-controlled converter 7, a voltage converter controller 10, a first DC power supply port 16, a second DC power supply port 17, an AC test port 15, and an impedance compensation branch 14.

[0103] The DC side of the current-controlled converter 1 is connected to the first DC power supply port 16, and the DC side of the voltage-controlled converter 7 is connected to the second DC power supply port 17. The first DC power supply port 16 and the second DC power supply port 17 are connected to an external DC power supply. The AC side of the current-controlled converter 1 and the AC side of the voltage-controlled converter 7 are connected in parallel to form an AC test port 15, which is used to connect the device under test.

[0104] Specifically, the current-controlled converter 1 is used to handle the main input power and main output power of the AC side port, that is, to provide test power, while the voltage-controlled converter 7 is used to reproduce the equivalent port characteristics of the simulated power grid.

[0105] Impedance compensation branch 14 is used to adjust the impedance based on the equivalent voltage of the simulated power grid. v sref and equivalent impedance Z ref (s) The impedance network A series equivalent term of the current-controlled converter Z series (s) and the AC test port voltage of the grid simulator used for grid-connected converter stability testing. v PCC Generate impedance compensation component v cp and impedance compensation component v cp The first modulation wave is injected into the output of the current-controlled converter 1.

[0106] In the above embodiments of this application, the equivalent port characteristics shaped by the voltage-controlled converter 7 are used to realize the differential-free calculation of the impedance compensation component; and the impedance compensation component is injected into the modulation signal of the current-controlled converter 1 through the impedance compensation branch 14 to improve the power point tracking capability of the current-controlled converter 1 and optimize the overall power distribution of the power grid simulator.

[0107] In some specific embodiments of this application, the current-controlled converter 1 includes a low-frequency switching bridge 2 and an impedance network A3, which are connected in series. The impedance network A3 is used to filter out current ripple.

[0108] Specifically, the impedance network A3 contains inductive elements with low-pass characteristics to filter out current ripple.

[0109] For example, the impedance network A3 can be an LC filter or an LCL filter.

[0110] The low-frequency switching bridge 2 can use silicon-based semiconductor devices to achieve high power capacity.

[0111] The voltage-controlled converter 7 includes a high-frequency switching bridge 8 and an impedance network B 9. The high-frequency switching bridge 8 and the impedance network B 9 are connected in series, and the impedance network B 9 is used to filter out voltage ripple.

[0112] Specifically, impedance network B9 contains inductive elements with low-pass characteristics to filter voltage ripple.

[0113] For example, impedance network B 9 can be an LC filter.

[0114] High-frequency switching bridges can use wide-bandgap semiconductor devices to achieve high switching frequencies.

[0115] The current converter controller 4 includes a current controller 5 and a low-frequency pulse width modulation module 6. The current controller 5 transmits a first modulation wave to the low-frequency pulse width modulation module 6. The current converter controller 4 is used to control the current-controlled converter 1 to track the current at the AC test port 15. i PCC .

[0116] Specifically, the current controller 5 generates a first modulation wave, which is then converted into a gate drive signal by the low-frequency pulse width modulation module 6 to control the switching behavior of the low-frequency switching bridge 2.

[0117] In some specific embodiments of this application, the current converter controller 4 employs a current control algorithm.

[0118] The current controller 5 implements current control using a closed-loop structure, including but not limited to proportional-integral control and hysteresis control.

[0119] The voltage converter controller 10 includes a simulated power grid model 11, a voltage controller 12, and a high-frequency pulse width modulation module 13. The simulated power grid model 11 transmits a control reference signal to the voltage controller 12, and the voltage controller 12 transmits a second modulation wave to the high-frequency pulse width modulation module 13. The voltage converter controller 10 is used to control the voltage-controlled converter 7 to generate the AC test port 15 voltage. v PCC .

[0120] Specifically, the simulated power grid model 11 generates a voltage reference signal for the AC test port 15 and inputs it into the voltage controller 12; the voltage controller 12 generates a second modulation wave and inputs it into the high-frequency pulse width modulation module 13; the high-frequency pulse width modulation module 13 generates a gate drive signal to control the switching behavior of the high-frequency switching bridge 8.

[0121] The voltage controller 12 implements voltage control using a closed-loop structure, including but not limited to proportional-integral control and hysteresis control.

[0122] In some specific embodiments of this application, the voltage converter controller 10 employs a voltage control algorithm.

[0123] In some specific embodiments of this application, the switching frequency of the voltage-controlled converter is higher than that of the current-controlled converter.

[0124] Preferably, the switching frequency of the voltage-controlled converter is 5 times or more the switching frequency of the current-controlled converter.

[0125] In some specific embodiments of this application, the simulated power grid model 11 is used to describe the port characteristics of the simulated power grid.

[0126] In some specific embodiments of this application, the simulated power grid model 11 adopts the Thevenin form and includes equivalent voltage. v sref and equivalent impedance Z ref (s) Two parameters.

[0127] The voltage at AC test port 15 is equal to the equivalent voltage of the simulated power grid. v sref and equivalent impedance Z ref The difference in series voltage drop across (s).

[0128]

[0129] in, v PCC This indicates the voltage at AC test port 15 of the multi-band power grid simulator. v sref This represents the equivalent voltage of the simulated power grid. i PCC This indicates the current at AC test port 15. Z ref (s) represents the equivalent impedance.

[0130] This application provides a multi-band power grid simulator, which includes a voltage-controlled converter 7 and a current-controlled converter 1, and the voltage-controlled converter 7 and the current-controlled converter 1 are connected in parallel. The multi-band power grid simulator adopts the power allocation optimization method of the multi-band power grid simulator provided in this application. By utilizing the equivalent port characteristics shaped by the voltage-controlled converter 7, the impedance compensation component is calculated without differentiation. The impedance compensation component is injected into the modulation signal of the current-controlled converter 1 through the impedance compensation branch 14 to improve the power point tracking capability of the current-controlled converter 1 and optimize the overall power allocation of the power grid simulator.

[0131] The preferred features in the above embodiments can be used individually in any embodiment, or in any combination thereof, provided they do not conflict with each other. Furthermore, parts not described in detail in the embodiments can be implemented using existing technologies.

[0132] The specific embodiments of this application have been described above. It should be understood that this application is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the substantive content of this application. The above-described preferred features can be used in any combination without conflict.

Claims

1. A power allocation optimization method for a multi-band power grid simulator, specifically for a power grid simulator used for stability testing of grid-connected converters, characterized in that... include: Determine the equivalent voltage of the simulated power grid v sref and equivalent impedance Z ref (s); Determine the series equivalent terms of the impedance network A of the current-controlled converter. Z series (s); Obtain the AC test port voltage of the power grid simulator used for grid-connected converter stability testing. v PCC ; Based on the equivalent voltage of the simulated power grid v sref and equivalent impedance Z ref (s) The impedance network A series equivalent term of the current-controlled converter Z series (s) and the AC test port voltage of the power grid simulator used for grid-connected converter stability testing. v PCC Calculate the impedance compensation component v cp : in, v cp This represents the impedance compensation component; The impedance compensation component v cp The modulation signal injected into the current-controlled converter is used to optimize the power distribution of the multi-band power grid simulator.

2. The power allocation optimization method for a multi-band power grid simulator according to claim 1, characterized in that, The method further includes: The simulated power grid is equivalent to a Thevenin form, and the equivalent port characteristics of the simulated power grid are based on the equivalent voltage. v sref and the equivalent impedance Z ref (s) description.

3. The power allocation optimization method for a multi-band power grid simulator according to claim 2, characterized in that, Under typical power grid conditions, the equivalent impedance of the simulated power grid exhibits resistivity and inductance.

4. The power allocation optimization method for a multi-band power grid simulator according to claim 1, characterized in that, The AC test port voltage of the power grid simulator used for grid-connected converter stability testing v PCC Equivalent to the equivalent voltage of the simulated power grid v sref With the equivalent impedance Z ref The difference in series voltage drop across (s).

5. The power allocation optimization method for a multi-band power grid simulator according to claim 1, characterized in that, Determine the series equivalent terms of the impedance network A of the current-controlled converter. Z series (s), including: The impedance network A of the flow-controlled converter is of the type of L-type filter or LCL filter, and the total inductive reactance of the L-type filter or the LCL filter is used as the series equivalent term of the impedance network A. Z series (s); The impedance network A of the flow-controlled converter is a non-L-type filter and a non-LCL filter. Based on circuit theory, the series equivalent term of the impedance network A is determined. Z series (s).

6. A multi-band power grid simulator, employing the power allocation optimization method for a multi-band power grid simulator as described in any one of claims 1 to 5 to achieve power allocation optimization, characterized in that, include: Current-controlled converters, current converter controllers, voltage-controlled converters, voltage converter controllers, and impedance compensation branches; The DC side of the current-controlled converter is connected to the first DC power supply port, and the DC side of the voltage-controlled converter is connected to the second DC power supply port. The first DC power supply port and the second DC power supply port are connected to an external DC power supply. The AC side of the current-controlled converter and the AC side of the voltage-controlled converter are connected in parallel to form an AC test port, which is used to connect the device under test. The current-controlled converter is used to handle the main input power and main output power of the AC test port, and the voltage-controlled converter is used to reproduce the equivalent port characteristics of the simulated power grid. The impedance compensation branch is used to adjust the voltage based on the equivalent voltage of the simulated power grid. v sref and equivalent impedance Z ref (s) The impedance network A series equivalent term of the current-controlled converter Z series (s) and the AC test port voltage of the grid simulator used for grid-connected converter stability testing. v PCC Generate impedance compensation component v cp and the impedance compensation component v cp It is injected into the first modulation wave output by the current converter controller.

7. The multi-band power grid simulator according to claim 6, characterized in that, The current-controlled converter includes a low-frequency switching bridge and an impedance network A, which are connected in series. The impedance network A is used to filter out current ripple. The voltage-controlled converter includes a high-frequency switching bridge and an impedance network B, which are connected in series. The impedance network B is used to filter out voltage ripple.

8. The multi-band power grid simulator according to claim 6, characterized in that, The current converter controller includes a current controller and a low-frequency pulse width modulation module. The current controller transmits the first modulation wave to the low-frequency pulse width modulation module. The current converter controller uses a current control algorithm to control the current-controlled converter to track the AC test port current. The voltage converter controller includes a simulated power grid model, a voltage controller, and a high-frequency pulse width modulation module. The simulated power grid model transmits a control reference signal to the voltage controller, and the voltage controller transmits a second modulation wave to the high-frequency pulse width modulation module. The voltage converter controller uses a voltage control algorithm to control the voltage-controlled converter to generate AC test port voltage.

9. The multi-band power grid simulator according to claim 6, characterized in that, The switching frequency of the voltage-controlled converter is higher than that of the current-controlled converter.

10. The multi-band power grid simulator according to claim 6, characterized in that, The simulated power grid model is used to describe the port characteristics of the simulated power grid; The simulated power grid model adopts the Thevenin form and includes two parameters: equivalent voltage and equivalent impedance.

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