Extensible network construction type converter test system and control method thereof

Abstract

The invention discloses an extensible network construction type converter test system and a control method thereof, and belongs to the technical field of converter test. The test system comprises a power supply module, a real-time simulation module, a controllable test power supply and a direct current voltage stabilization source. And the power supply module provides a power supply, so that the controllable test power supply and the direct-current voltage-stabilizing source can operate normally. According to the invention, the real-time simulation module provides a modulation signal to the controllable test power supply, and based on the modulation of the controllable test power supply, the AC side electric signal of the tested network-forming converter is changed and is transmitted to the real-time simulation module to realize the closed-loop simulation test. Moreover, based on at least one first converter included in the controllable test power supply and at least one second converter included in the direct-current voltage-stabilizing source, the controllable test power supply and the direct-current voltage-stabilizing source can provide alternating-current electric signals and direct-current electric signals which are adaptive to the tested network-forming converters with different capacities. Therefore, the network construction characteristic test of the network construction type converters with different capacity levels can be realized.

Description

Technical Field

[0001] This application relates to the technical field of converter testing, and in particular to a scalable grid-type converter testing system and its control method. Background Technology

[0002] In power systems, grid-connected converters, as voltage sources with low series impedance and controllable amplitude and phase, exhibit unique advantages. They can autonomously construct their internal potential and achieve excellent self-synchronization performance without a phase-locked loop, playing a crucial supporting role in the stable operation of the power grid. However, there are multiple technical routes for implementing grid-connected technology, and the implementation methods and characteristics of different converter manufacturers also vary. Therefore, to ensure that grid-connected converters can effectively support the power grid during grid connection, rigorous grid-connection characteristic tests must be conducted before grid connection.

[0003] Currently, grid-connected converters cover a wide range of capacity levels, from hundreds of kilowatts to megawatts. However, existing testing platforms cannot meet the testing requirements for the grid characteristics of grid-connected converters of different capacity levels. Summary of the Invention

[0004] This application provides a scalable grid-type converter testing system and its control method, which can realize grid characteristic testing of grid-type converters with different capacity levels.

[0005] In a first aspect, embodiments of this application provide a scalable grid-type converter testing system, comprising:

[0006] Power module;

[0007] The real-time simulation module is connected to the AC side of the grid-type converter under test. The real-time simulation module is used to output a modulated signal based on the AC side electrical signal of the grid-type converter under test.

[0008] The controllable test power supply includes at least one first converter. Each first converter is connected to the power module, the real-time simulation module, and the AC side of the grid-type converter under test. At least one first converter in the controllable test power supply is used to modulate based on the modulation signal to output an AC signal to the AC side of the grid-type converter under test.

[0009] A DC regulated power supply includes at least one second converter. Each second converter is connected to a power module and the DC side of the grid-type converter under test. At least one second converter in the DC regulated power supply is used to output a DC signal to the DC side of the grid-type converter under test.

[0010] In some embodiments, the testing system further includes:

[0011] Circuit breakers are installed between each first converter and the power module, and between each second converter and the power module.

[0012] In some embodiments, the circuit breaker includes a plurality of sub-circuit breakers, one end of each sub-circuit breaker being connected to a power module, and the other end of any sub-circuit breaker being connected to at least one first converter and / or at least one second converter.

[0013] In some embodiments, the testing system further includes:

[0014] Transformers are installed between each first converter and the power module, and between each second converter and the power module.

[0015] In some embodiments, the transformer includes multiple sub-transformers, each sub-transformer having a power module connected to its primary side, and the secondary winding of any sub-transformer being connected to a first converter or a second converter.

[0016] In some embodiments, the secondary winding of the sub-transformer is connected in a delta configuration.

[0017] In some embodiments, the testing system further includes:

[0018] Multiple reactors are provided, with at least one reactor between the AC side of each first converter and the grid-type converter under test.

[0019] In some embodiments, the real-time simulation module is used to output a modulated signal based on the AC side electrical signal of the grid-type converter under test, including:

[0020] Construct a preset power model, which includes power models for each preset test scenario;

[0021] Based on the power model of each preset test scenario and the AC side electrical signal of the grid-type converter under test, the modulation signal corresponding to the power model of each preset test scenario is output.

[0022] Secondly, this application also provides a control method for a scalable grid-type converter test system, comprising:

[0023] Start the real-time simulation module, which outputs a modulated signal based on the AC side electrical signal of the grid-type converter under test.

[0024] Start the controllable test power supply. Based on the set power of the grid converter under test, at least one first converter in the controllable test power supply modulates based on the modulation signal to output an AC signal to the AC side of the grid converter under test.

[0025] Start the DC regulated power supply. Based on the set power of the grid converter under test, at least one second converter in the DC regulated power supply outputs a DC signal to the DC side of the grid converter under test.

[0026] The real-time simulation module is used to construct a preset power system model, which includes the power model of each preset test scenario. Based on the power model of each preset test scenario and the AC side electrical signal of the grid-type converter under test, the real-time simulation module outputs the modulation signal corresponding to the power model of each preset test scenario.

[0027] In some embodiments, when multiple second converters in a DC regulated power source output DC signals, the multiple second converters in the DC regulated power source output DC signals to the DC side of the grid-type converter under test based on a multi-converter parallel coordinated control strategy.

[0028] In some embodiments, multiple second converters in a DC regulated power supply output DC signals to the DC side of the grid-type converter under test based on a multi-converter parallel coordinated control strategy, including:

[0029] The controller of any second converter determines the AC current control command through PI calculation based on the DC voltage signal on the DC side of the grid converter under test and the reference voltage signal of the grid converter under test;

[0030] In a DC regulated power supply, multiple secondary converters output DC signals to the DC side of the grid-type converter under test based on AC current control commands.

[0031] This application provides an scalable grid-type converter testing system, which includes a power supply module, a real-time simulation module, a controllable test power supply, and a DC regulated power supply. The power supply module provides power to enable the controllable test power supply and the DC regulated power supply to operate normally. This application provides a modulation signal to the controllable test power supply through the real-time simulation module. Based on the modulation of the controllable test power supply, the AC side electrical signal of the grid-type converter under test is changed and transmitted to the real-time simulation module to achieve closed-loop simulation testing. Furthermore, based on at least one first converter included in the controllable test power supply and at least one second converter included in the DC regulated power supply, the controllable test power supply and the DC regulated power supply can provide AC and DC electrical signals adapted to grid-type converters under test with different capacities, thereby enabling grid characteristic testing of grid-type converters with different capacity levels.

[0032] This application also provides a control method for a scalable grid-type converter test system, which is applied to a scalable grid-type converter test system. The control method for the scalable grid-type converter test system includes the effects of all the features of the scalable grid-type converter test system, which will not be elaborated here. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0035] Figure 1 A schematic block diagram of a scalable grid-type converter test system provided for embodiments of this application;

[0036] Figure 2 A schematic diagram of the topology of another scalable grid-type converter test system provided in this application embodiment;

[0037] Figure 3 A topology diagram of another scalable grid-type converter test system provided in this application embodiment;

[0038] Figure 4 A topology diagram of another scalable grid-type converter test system provided in this application embodiment;

[0039] Figure 5 This is a flowchart illustrating a control method for a scalable grid-type converter testing system provided in an embodiment of this application.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1. Power supply module; 2. Controllable test power supply; 21. First converter; 3. Real-time simulation module; 4. DC regulated power supply; 41. Second converter; 5. Test grid converter; 6. Circuit breaker; 61. Sub-circuit breaker; 7. Transformer; 71. Sub-transformer; 8. Reactor. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0043] In the embodiments of this application, "at least one" refers to one or more; "multiple" refers to two or more. In the description of this application, the terms "first," "second," "third," etc., are used only for the purpose of distinguishing descriptions and should not be construed as indicating or implying relative importance, nor should they be construed as indicating or implying order.

[0044] References such as “one embodiment” or “some embodiments” as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the terms “comprising,” “including,” “having,” and variations thereof, as used in this specification, mean “including, but not limited to,” unless otherwise specifically emphasized.

[0045] It should be noted that in the embodiments of this application, "and / or" describes the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. In addition, the character " / ", unless otherwise specified, generally indicates that the associated objects before and after it are in an "or" relationship.

[0046] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0047] With the introduction of carbon reduction and energy conservation goals and the rapid development of renewable energy, the proportion of new energy installed capacity in my country's power system has been continuously increasing, gradually forming a development trend of high proportion of new energy and high proportion of power electronic equipment connected to the grid. However, due to the volatility, intermittency, and uncertainty of new energy power generation, traditional grid-connected control methods suffer from insufficient stability when transmitted through weak grids. Furthermore, grid-connected control exhibits current source characteristics, resulting in weak voltage control capabilities of the grid and affecting the safe operation of the power system. To address the numerous problems associated with grid-connected control, grid-connected control using power electronic inverters with voltage source characteristics has gained widespread attention.

[0048] In power systems, grid-connected converters, as voltage sources with low series impedance and controllable amplitude and phase, exhibit unique advantages. They can autonomously construct their internal potential and achieve excellent self-synchronization performance without a phase-locked loop, playing a crucial supporting role in the stable operation of the power grid. However, there are multiple technical routes for implementing grid-connected technology, and the implementation methods and characteristics of different converter manufacturers also vary. Therefore, to ensure that grid-connected converters can effectively support the power grid during grid connection, rigorous grid-connection characteristic tests must be conducted before grid connection.

[0049] Testing of grid-connected converters can be conducted through methods such as hardware-in-the-loop (HIL) real-time simulation testing, full-power testing on physical test platforms, and field fault testing. Among these, physical test platforms can not only simulate various fault conditions in the field and simulation systems but also perform full-power testing on actual converters, making them a crucial testing method. However, grid-connected converters have a wide capacity range, ranging from hundreds of kilowatts to megawatts. Therefore, different capacity levels of grid-connected converters require different test platform capacities, and a single physical test platform cannot meet the testing needs of grid-connected converters of varying capacity levels.

[0050] In view of this, this application proposes a scalable grid-type converter testing system, which aims to solve at least one of the above-mentioned technical problems.

[0051] Please see Figure 1 As shown, Figure 1 This is a schematic block diagram of a scalable grid-type converter test system provided in an embodiment of this application.

[0052] This application provides an scalable grid-type converter test system, including: a power supply module 1, a real-time simulation module 3, a controllable test power supply 2, and a DC regulated power supply 4. The real-time simulation module 3 is connected to the AC side of the grid-type converter 5 under test. The real-time simulation module 3 is used to output a modulation signal based on the AC side electrical signal of the grid-type converter 5 under test. The controllable test power supply 2 includes at least one first converter 21. Each first converter 21 is connected to the power supply module 1, the real-time simulation module 3, and the AC side of the grid-type converter 5 under test. At least one first converter 21 in the controllable test power supply 2 is used to modulate based on the modulation signal to output an AC electrical signal to the AC side of the grid-type converter 5 under test. The DC regulated power supply 4 includes at least one second converter 41. Each second converter 41 is connected to the power supply module 1 and the DC side of the grid-type converter 5 under test. At least one second converter 41 in the DC regulated power supply 4 is used to output a DC electrical signal to the DC side of the grid-type converter 5 under test.

[0053] In this system, power module 1 provides basic power to the entire test system. Power module 1 is connected to both the controllable test power supply 2 and the DC regulated power supply 4. Power from power module 1 flows through the controllable test power supply 2 to the grid-type converter 5 under test, and then back to power module 1 through the DC regulated power supply 4, forming the test power loop. This ensures the normal operation of the controllable test power supply 2 and the DC regulated power supply 4, and maintains the stability of the test system. It should be understood that there can be only one power module 1, which is powered through the same power bus. Each first converter 21 in the controllable test power supply 2 and each second converter 41 in the DC regulated power supply 4 are connected to this power bus, ensuring that disturbances in the test power loop do not affect power module 1, thus maintaining the stability of the power supply from power module 1. For example, power module 1 can be an AC power source, such as mains power.

[0054] The real-time simulation module 3 is connected to the AC side of the grid-connected converter 5 under test, and also connected to each of the first converters 21 in the controllable test power supply 2. Thus, the real-time simulation module 3 is used to acquire the AC side electrical signals of the grid-connected converter 5 under test, and outputs a modulation signal to the first converter 21 in the controllable test power supply 2 based on the acquired AC side electrical signals. The modulation signal can simulate the dynamic behavior and response characteristics of the grid connection point in a real power system, thereby enabling the controllable test power supply 2 to modulate and simulate the grid conditions corresponding to the modulation signal. It should be noted that the AC side electrical signals include at least one of the voltage and current at the AC side port of the grid-connected converter 5 under test. The real-time simulation module 3 can acquire the voltage and current at the AC side port of the grid-connected converter 5 under test through voltage and current sensors. It should also be noted that the real-time simulation module 3 can simulate various dynamic changes in the power grid, such as voltage fluctuations, frequency changes, and harmonic interference. By combining this with the AC side electrical signal of the grid-connected converter 5 under test, it outputs a corresponding modulation signal to modulate the controllable test power supply 2, thereby testing the adaptability of the grid-connected converter 5. For example, the real-time simulation module 3 can use RTDS (Real-Time Digital Simulator), RT-LAB (Real-Time Lab), etc., depending on the specific implementation requirements.

[0055] The controllable test power supply 2 includes multiple first converters 21. Each first converter 21 may include an interconnected rectifier and an inverter. The AC terminal of each rectifier is connected to the power module 1, and each inverter is connected to the real-time simulation module 3 and the AC side of the grid-type converter under test 5, respectively. The mains power supplies power to the rectifier, which in turn provides DC power to the inverter. The inverter modulates the signal output from the real-time simulation module 3 to output an AC signal to the AC side of the grid-type converter under test 5. In other words, the inverter simulates the voltage and frequency fluctuations of the real power grid based on the modulated signal and outputs it to the AC side of the grid-type converter under test 5, thus allowing the grid-type converter under test 5 to actively follow the AC signal output by the controllable test power supply 2. It should be understood that the controllable test power supply 2 simulates the grid conditions corresponding to the modulated signal, thereby enabling the grid-type converter under test 5 to undergo performance evaluation under the corresponding simulated grid conditions. Its grid-connection characteristics can be evaluated by analyzing the data of various parameters of the grid-type converter under test 5 during the tracking process. Furthermore, it allows for accurate determination of the performance and stability of the grid-type converter under test 5 under simulated grid conditions. Through the control of the modulated signal, the controllable test power supply 2 can reproduce various grid fluctuations, thus providing a reliable test environment for converter performance evaluation. It should be understood that multiple first converters 21 allow the controllable test power supply 2 to provide at least one first converter 21 to adapt to the AC signals of grid-type converters under test 5 of different capacities, thereby enabling the controllable test power supply 2 to support grid-connection characteristic testing of grid-type converters of different capacity levels. It should be noted that the AC signal can include at least one of AC voltage and AC current. Furthermore, multiple first converters 21 can be connected to the AC side of the grid-type converter 5 under test via the same AC bus, or they can be connected to the AC side of the grid-type converter 5 under test without an AC bus.

[0056] The DC regulated power supply 4 includes multiple second converters 41. Each second converter 41 may include a rectifier. The AC terminal of each rectifier is connected to the power module 1, and the DC terminal of each rectifier is connected to the DC side of the grid-type converter under test 5. The mains power supplies power to the rectifiers, and the rectifiers output a DC signal to the DC side of the grid-type converter under test 5 to stabilize the DC signal of the grid-type converter under test 5. It should be understood that the multiple second converters 41 allow the DC regulated power supply 4 to provide at least one second converter 41 to accommodate the DC signals of grid-type converters under test 5 with different capacities, thereby enabling the DC regulated power supply 4 to support grid characteristic testing of grid-type converters with different capacity levels. It should be noted that the DC signal may include at least one of DC voltage and DC current. Furthermore, multiple second converters 41 can be connected to the DC side of the grid-type converter 5 under test via the same DC bus, or they can be connected to the DC side of the grid-type converter 5 under test without a DC bus.

[0057] Through the above technical solution, this application provides an scalable grid-type converter testing system. The system includes a power supply module 1, a real-time simulation module 3, a controllable test power supply 2, and a DC regulated power supply 4. The power supply module 1 provides power to enable the controllable test power supply 2 and the DC regulated power supply 4 to operate normally. This application provides a modulation signal to the controllable test power supply 2 through the real-time simulation module 3. Based on the modulation of the controllable test power supply 2, the AC side electrical signal of the grid-type converter 5 under test is changed and transmitted to the real-time simulation module 3 to achieve closed-loop simulation testing. Furthermore, based on at least one first converter 21 included in the controllable test power supply 2 and at least one second converter 41 included in the DC regulated power supply 4, the controllable test power supply 2 and the DC regulated power supply 4 can provide AC and DC electrical signals adapted to grid-type converters 5 of different capacities under test, thereby enabling grid characteristic testing of grid-type converters with different capacity levels. Furthermore, the controllable test power supply 2 includes multiple first converters 21, and the DC regulated power supply 4 includes multiple second converters 41, enhancing the flexibility of the test system configuration and enabling it to meet the testing requirements of grid-type converters with different capacities. It should be noted that the capacity of the grid-type converter under test refers to its rated capacity.

[0058] like Figure 2 As shown, Figure 2 A topology diagram of another scalable grid-type converter test system provided in this application embodiment.

[0059] In some embodiments, the test system further includes a circuit breaker 6 disposed between each first converter 21 and power module 1, and between each second converter 41 and power module 1.

[0060] It is important to understand that circuit breaker 6 is positioned between power module 1 and controllable test power supply 2, and between power module 1 and DC regulated power supply 4. Circuit breaker 6 is used to select between multiple first converters 21 in controllable test power supply 2 and multiple second converters 41 in DC regulated power supply 4, so that controllable test power supply 2 and DC regulated power supply 4 can provide AC and DC signals suitable for different capacities of the grid-type converter 5 under test. That is, circuit breaker 6 can select at least one first converter 21 in controllable test power supply 2 and at least one second converter 41 in DC regulated power supply 4 to connect to power module 1. First converters 21 and second converters 41 disconnected from power module 1 stop working, while first converters 21 and second converters 41 connected to power module 1 operate to provide corresponding AC and DC signals to the AC and DC sides of the grid-type converter 5 under test. For example, circuit breaker 6 can employ switching devices such as relays, contactors, and transistors, and circuit breaker 6 can be operated manually or automatically. When circuit breaker 6 is operated automatically, the first converter 21 and the second converter 41 can be selected based on the set power conditions of the grid-type converter 5 under test, according to the control module of the test system. It is sufficient that the number of selected first converters 21 and second converters 41 meets the set power requirements of the grid-type converter.

[0061] In some embodiments, the circuit breaker 6 includes a plurality of sub-circuit breakers 61, one end of each sub-circuit breaker 61 is connected to the power module 1, and the other end of any sub-circuit breaker 61 is connected to at least one first converter 21 and / or at least one second converter 41.

[0062] In other words, one end of each sub-circuit breaker 61 is connected to the power module 1, and the other end of any sub-circuit breaker 61 can be connected to at least one first converter 21, at least one second converter 41, or at least one first converter 21 and at least one second converter 41. For example, the sub-circuit breaker 61 can be a relay, contactor, transistor, or other switching device. It should be noted that each first converter 21 and each second converter 41 are connected to the power module 1 through at least one sub-circuit breaker 61.

[0063] In some embodiments, the plurality of sub-circuit breakers 61 can be divided into a first group of sub-circuit breakers and a second group of sub-circuit breakers. The other end of each sub-circuit breaker 61 in the first group of sub-circuit breakers is connected to a first converter 21, and the other end of each sub-circuit breaker 61 in the second group of sub-circuit breakers is connected to a second converter 41. That is, the other end of each sub-circuit breaker 61 in the first group of sub-circuit breakers can be connected to at least one first converter 21, and the other end of each sub-circuit breaker 61 in the second group of sub-circuit breakers can be connected to at least one second converter 41.

[0064] Please see Figure 2 and Figure 3 As shown, Figure 3 This is a topology diagram of another scalable grid-type converter test system provided in the embodiments of this application.

[0065] Specifically, such as Figure 2 As shown, in some examples, the other end of each sub-circuit breaker 61 in the first group of sub-circuit breakers can be connected to a first converter 21; the other end of each sub-circuit breaker 61 in the second group of sub-circuit breakers can be connected to a second converter 41. For example... Figure 3 As shown, in some other examples, the other end of each sub-circuit breaker 61 in the first group of sub-circuit breakers can be connected to multiple first converters 21, such as two first converters 21; the other end of each sub-circuit breaker 61 in the second group of sub-circuit breakers can be connected to multiple second converters 41, such as two second converters 41. In still other examples, the other end of each sub-circuit breaker 61 in the first group of sub-circuit breakers can be connected to one first converter 21; the other end of each sub-circuit breaker 61 in the second group of sub-circuit breakers can be connected to multiple second converters 41, such as two second converters 41. Alternatively, the other end of each sub-circuit breaker 61 in the first group of sub-circuit breakers can be connected to multiple first converters 21, such as two first converters 21; the other end of each sub-circuit breaker 61 in the second group of sub-circuit breakers can be connected to one second converter 41. In some examples, the other end of some sub-circuit breakers 61 in the first group of sub-circuit breakers can be connected to a first converter 21, and the other end of the remaining sub-circuit breakers 61 in the first group of sub-circuit breakers can be connected to multiple first converters 21, such as two first converters 21; the other end of each sub-circuit breaker 61 in the second group of sub-circuit breakers is connected to multiple second converters 41 or a single second converter 41, such as two second converters 41. Alternatively, the other end of each sub-circuit breaker 61 in the first group of sub-circuit breakers can be connected to multiple first converters 21 or a single first converter 21, such as two first converters 21; the other end of some sub-circuit breaker 61 in the second group of sub-circuit breakers can be connected to a single second converter 41, and the other end of the remaining sub-circuit breaker 61 in the second group of sub-circuit breakers can be connected to multiple second converters 41, such as two second converters 41. Alternatively, one end of some sub-circuit breakers 61 in the first group of sub-circuit breakers can be connected to a first converter 21, and the other end of the remaining sub-circuit breakers 61 in the first group of sub-circuit breakers can be connected to multiple first converters 21, such as two first converters 21; the other end of some sub-circuit breakers 61 in the second group of sub-circuit breakers can be connected to a second converter 41, and the other end of the remaining sub-circuit breakers 61 in the second group of sub-circuit breakers can be connected to multiple second converters 41, such as two second converters 41.

[0066] Please see Figure 4 As shown, Figure 4 This is a topology diagram of another scalable grid-type converter test system provided in an embodiment of this application.

[0067] In some embodiments, the plurality of sub-circuit breakers 61 can be a third group of sub-circuit breakers, and the other end of each sub-circuit breaker 61 in the third group of sub-circuit breakers can be connected to the first converter 21 and the second converter 41, respectively. That is, the other end of each sub-circuit breaker 61 in the third group of sub-circuit breakers can be connected to at least one first converter 21 and at least one second converter 41, respectively. Figure 4 As shown, for example, the other end of each sub-circuit breaker 61 in the third group of sub-circuit breakers is connected to a first converter 21 and a second converter 41, respectively.

[0068] It should be understood that, in some embodiments, the multiple sub-circuit breakers 61 can be further divided into a first group of sub-circuit breakers and a third group of sub-circuit breakers. The connection methods of the first group of sub-circuit breakers and the third group of sub-circuit breakers can be referred to the description in the above embodiments, and will not be repeated here. In other embodiments, the multiple sub-circuit breakers 61 can be further divided into a first group of sub-circuit breakers, a second group of sub-circuit breakers, and a third group of sub-circuit breakers. The connection methods of the first group of sub-circuit breakers, the second group of sub-circuit breakers, and the third group of sub-circuit breakers can be referred to the description in the above embodiments, and will not be repeated here. In still other embodiments, the multiple sub-circuit breakers 61 can be further divided into a first group of sub-circuit breakers, a second group of sub-circuit breakers, and a third group of sub-circuit breakers. The connection methods of the first group of sub-circuit breakers, the second group of sub-circuit breakers, and the third group of sub-circuit breakers can be referred to the description in the above embodiments, and will not be repeated here.

[0069] Understandably, the sub-circuit breaker 61 is used to select from multiple first converters 21 in the controllable test power supply 2 and multiple second converters 41 in the DC regulated power supply 4, so that at least one first converter 21 selected from the controllable test power supply 2 and at least one second converter 41 selected from the DC regulated power supply 4 can provide AC and DC signals suitable for different capacities of the grid-type converter 5 under test. This allows the test system to flexibly adapt to different test requirements and ensures accurate electrical signal support for the grid-type converter 5 under test. It should be noted that the selection action can be performed by the controller corresponding to the test system. The controller can select from multiple first converters 21 in the controllable test power supply 2 and multiple second converters 41 in the DC regulated power supply 4, i.e., control the closing of the corresponding sub-circuit breaker 61, so that the controllable test power supply 2 and the DC regulated power supply 4 can provide AC and DC signals suitable for different capacities of the grid-type converter 5 under test.

[0070] In some embodiments, the test system further includes a transformer 7 disposed between each first converter 21 and the power module 1, and between each second converter 41 and the power module 1.

[0071] It is important to understand that transformer 7 is positioned between power module 1 and controllable test power supply 2, and between power module 1 and DC regulated power supply 4. Transformer 7 is used to control the DC signal of the grid-connected converter 5 under test. That is, transformer 7 can adjust the voltage and current levels of the DC signal of the grid-connected converter 5 under test by stepping up or stepping down, enabling DC regulated power supply 4 to support grid characteristic testing of grid-connected converters of different capacity levels, and ensuring that the converter can efficiently and safely provide DC signals within its rated parameter range. Furthermore, transformer 7 provides electrical isolation, enhancing system safety and preventing electrical interference and fault propagation between power module 1 and DC regulated power supply 4, and between power module 1 and controllable test power supply 2. It should be noted that the selection and configuration of transformer 7 can be adjusted according to the specific requirements of the test system. For example, transformers 7 with different turns ratios can be selected to adapt to different voltage conversion requirements. Simultaneously, the capacity and insulation class of transformer 7 should also be designed according to the maximum load and safety standards of the system.

[0072] It should also be noted that the transformer 7 can be set between the circuit breaker 6 and the controllable test power supply 2, and between the circuit breaker 6 and the DC regulated power supply 4. That is, each first converter 21 and each second converter 41 are connected to the circuit breaker 6 through the transformer 7. In other words, the other end of any sub-circuit breaker 61 is connected to at least one first converter 21 and / or at least one second converter 41 through the transformer 7.

[0073] In some embodiments, the transformer 7 includes a plurality of sub-transformers 71, the primary side of each sub-transformer 71 is connected to the power module 1, and the secondary winding of any sub-transformer 71 is connected to a first converter 21 or a second converter 41.

[0074] In other words, the primary winding of each sub-transformer 71 is connected to the power module 1, and the secondary winding of any sub-transformer 71 can be connected to either a first converter 21 or a second converter 41. That is, each secondary winding of any sub-transformer 71 is connected to only one first converter 21 or one second converter 41. It should be noted that each first converter 21 and each second converter 41 are connected to the power module 1 through at least one sub-transformer 71, that is, each first converter 21 and each second converter 41 are connected to the secondary winding of at least one sub-transformer 71.

[0075] In some embodiments, the plurality of sub-transformers 71 can be divided into a first group of sub-transformers and a second group of sub-transformers. The secondary winding of each sub-transformer 71 in the first group of sub-transformers is connected to a first converter 21, and the secondary winding of each sub-transformer 71 in the second group of sub-transformers is connected to a second converter 41. That is, each secondary winding of each sub-transformer 71 in the first group of sub-transformers is connected to a first converter 21, and each secondary winding of each sub-transformer 71 in the second group of sub-transformers is connected to a second converter 41.

[0076] Specifically, such as Figure 2 As shown, in some examples, each sub-transformer 71 in the first group of sub-transformers is connected to a first converter 21, and each sub-transformer 71 in the second group of sub-transformers is connected to a second converter 41. Exemplarily, each sub-transformer 71 in the first group of sub-transformers and each sub-transformer 71 in the second group of sub-transformers can be a two-winding transformer, and thus each sub-transformer 71 in both groups has a secondary winding. Therefore, the secondary winding of each sub-transformer 71 in the first group of sub-transformers is connected to a first converter 21, and the secondary winding of each sub-transformer 71 in the second group of sub-transformers is connected to a second converter 41. Figure 3As shown, in some other examples, each sub-transformer 71 in the first group of sub-transformers can be connected to multiple first converters 21, and each sub-transformer 71 in the second group of sub-transformers can be connected to multiple second converters 41. For example, each sub-transformer 71 in the first group of sub-transformers and each sub-transformer 71 in the second group of sub-transformers can be a three-winding transformer, and thus each sub-transformer 71 in both groups has two secondary windings. Therefore, each secondary winding of each sub-transformer 71 in the first group of sub-transformers is connected to one first converter 21, and each secondary winding of each sub-transformer 71 in the second group of sub-transformers is connected to one second converter 41. In still other examples, each sub-transformer 71 in the first group of sub-transformers can be connected to one first converter 21, and each sub-transformer 71 in the second group of sub-transformers can be connected to multiple second converters 41, such as two second converters 41. Alternatively, each sub-transformer 71 in the first group of sub-transformers can be connected to multiple first converters 21, such as two first converters 21; each sub-transformer 71 in the second group of sub-transformers can be connected to one second converter 41. In some other examples, some sub-transformers 71 in the first group of sub-transformers can be connected to one first converter 21, and the remaining sub-transformers 71 in the first group of sub-transformers can be connected to multiple first converters 21, such as two first converters 21; each sub-transformer 71 in the second group of sub-transformers can be connected to multiple second converters 41 or one second converter 41, or multiple second converters 41, such as two second converters 41. Alternatively, each sub-transformer 71 in the first group of sub-transformers can be connected to multiple first converters 21 or one first converter 21, such as two first converters 21; some sub-transformers 71 in the second group of sub-transformers can be connected to one second converter 41, and the remaining sub-transformers 71 in the second group of sub-transformers can be connected to multiple second converters 41, such as two second converters 41. Alternatively, some sub-transformers 71 in the first group of sub-transformers can be connected to one first converter 21, and the remaining sub-transformers 71 in the first group of sub-transformers can be connected to multiple first converters 21, such as two first converters 21; some sub-transformers 71 in the second group of sub-transformers can be connected to one second converter 41, and the remaining sub-transformers 71 in the second group of sub-transformers can be connected to multiple second converters 41, such as two second converters 41.

[0077] Please see Figure 4As shown, in some embodiments, the multiple sub-transformers 71 can be a third group of sub-transformers, and each sub-transformer 71 in the third group of sub-transformers can be connected to the first converter 21 and the second converter 41. That is, each sub-transformer 71 in the third group of sub-transformers can be connected to one first converter 21 and one second converter 41. For example, each sub-transformer 71 in the third group of sub-transformers can be a three-winding transformer, and thus each sub-transformer 71 in the third group of sub-transformers has two secondary windings, one of which is connected to one first converter 21, and the other secondary winding is connected to one second converter 41.

[0078] It should be noted that when a transformer has one secondary winding, the transformer is connected to only one converter through the secondary winding, which can be either the first converter or the second converter; when a transformer has multiple secondary windings, each secondary winding is connected to a converter, which can be either the first converter or the second converter.

[0079] It should be understood that in some embodiments, the multiple sub-transformers 71 can be further divided into a first group of sub-transformers and a third group of sub-transformers. The connection methods of the first group of sub-transformers and the third group of sub-transformers can be referred to the description in the above embodiments, and will not be repeated here. In other embodiments, the multiple sub-transformers 71 can be further divided into a second group of sub-transformers and a third group of sub-transformers. The connection methods of the second group of sub-transformers and the third group of sub-transformers can be referred to the description in the above embodiments, and will not be repeated here. In still other embodiments, the multiple sub-transformers 71 can be further divided into a first group of sub-transformers, a second group of sub-transformers, and a third group of sub-transformers. The connection methods of the first group of sub-transformers, the second group of sub-transformers, and the third group of sub-transformers can be referred to the description in the above embodiments, and will not be repeated here. It should be noted that each sub-transformer 71 can be connected to the power module 1 through at least one sub-circuit breaker 61.

[0080] Understandably, the sub-transformer 71 can adjust the voltage and current levels of the DC signal of the grid-connected converter 5 under test by stepping up or stepping down, enabling the DC regulated power supply 4 to support grid-connected converter characteristic tests of different capacity levels and ensuring that the converter can efficiently and safely provide DC signals within its rated parameter range. Furthermore, the sub-transformer 71 can also provide electrical isolation, enhancing system safety and preventing electrical interference and fault propagation between the power module 1 and each first converter 21 and each second converter 41.

[0081] like Figure 3 and Figure 4 As shown, in some embodiments, the secondary winding of the sub-transformer 71 is connected in a delta configuration.

[0082] It is important to understand that when the secondary side of the sub-transformer 71 is connected to two first converters 21 or two second converters 41, and when the secondary side of the sub-transformer 71 is connected to one first converter 21 and one second converter 41, the secondary winding of the sub-transformer 71 adopts a delta connection. For example, the sub-transformer 71 is a three-winding transformer, comprising one primary winding and two secondary windings. Furthermore, the delta connection means that the three windings of the sub-transformer 71 are connected to form a closed delta circuit. The end of each winding is connected to the beginning of the next winding, forming a ring structure, with three terminals exposed externally. In the delta connection configuration of the secondary winding of the sub-transformer 71, the two terminals corresponding to the two secondary windings of the sub-transformer 71 can be connected to two first converters 21 or two second converters 41 respectively, and the two secondary windings of the sub-transformer 71 can also be connected to one first converter 21 and one second converter 41 respectively.

[0083] Understandably, the delta connection of the sub-transformer 71 effectively reduces circulating current between the two converters when connected to it, thereby improving the consistency of their outputs. Furthermore, the delta connection effectively suppresses third harmonics, contributing to converter stability and ultimately improving the stability and efficiency of the testing system. Moreover, the delta connection adapts to various load conditions, providing stable power support. This allows the converter to maintain stable performance under different operating conditions.

[0084] In some embodiments, the testing system further includes:

[0085] Multiple reactors 8 are provided, with at least one reactor 8 between the AC side of each first converter 21 and the grid-type converter 5 under test.

[0086] It should be understood that at least one reactor 8 is provided between the AC side of each first converter 21 and the AC side of the grid-type converter under test 5. That is, at least one reactor 8 is provided between the AC terminal of the inverter in each first converter 21 and the AC side of the grid-type converter under test 5. It should be noted that each first converter 21 can be connected to the same AC bus via the reactor 8, and then connected to the AC side of the grid-type converter under test 5 via the AC bus. Alternatively, it can be without an AC bus, with each first converter 21 connected to the AC side of the grid-type converter under test 5 via the reactor 8. It should also be noted that the real-time simulation module is used to acquire the AC side electrical signal on the line between the reactor 8 and the AC side of the grid-type converter under test 5.

[0087] Understandably, reactor 8 can limit rapid changes in current by increasing the circuit's inductance, thus helping to protect the converter from current spikes and reducing overcurrent damage to the test system. Additionally, reactor 8 can suppress high-frequency harmonics, improving power quality and enabling stable operation of the test system. Furthermore, reactor 8 can help regulate the AC voltage, ensuring the converter operates within its rated voltage range, contributing to improved system reliability and efficiency.

[0088] In some embodiments, the real-time simulation module 3 is used to output a modulated signal based on the AC side electrical signal of the grid-type converter 5 under test, including:

[0089] Construct a preset power model, which includes power models for each preset test scenario;

[0090] Based on the power model of each preset test scenario and the AC side electrical signal of the grid-type converter 5 under test, the modulation signal corresponding to the power model of each preset test scenario is output.

[0091] It is important to understand that the real-time simulation module 3 can be used to build and simulate preset power models. By modeling with preset power models, the dynamic behavior and response characteristics of grid-connected points in real power systems can be simulated. These preset power models include power models for various preset test scenarios. Each preset test scenario power model can simulate disturbances in the actual power system, such as system faults, frequency changes, and phase jumps. Specifically, the power models for each preset test scenario can be obtained by changing the model structure and parameters of the built power model.

[0092] It should be noted that the preset power models included in the preset test scenarios can be a single power model obtained by changing model parameters or adding disturbances, thereby simulating system faults, frequency changes, phase jumps, etc., in actual power systems. Alternatively, the preset power models included in the preset test scenarios can be multiple different power models obtained by changing the model structure of the constructed power model. Different power models are used to simulate different actual power systems. Each power model can be obtained by changing model parameters or adding disturbances, thereby simulating system faults, frequency changes, phase jumps, etc., in actual power systems. Therefore, the preset power models included in the preset test scenarios can also be different power models, and each power model can be obtained by changing model parameters or adding disturbances.

[0093] In some embodiments, the real-time simulation module can build a corresponding preset power model according to the actual power grid conditions. Then, the real-time simulation module collects the AC side port electrical signal of the grid-type converter 5 under test in real time. Based on the real-time collected AC side port electrical signal of the grid-type converter 5 under test and the preset power model built, the real-time simulation module updates the output modulation signal to the controllable test power supply 2 in real time. Understandably, when the preset power model changes—that is, when the preset power model changes between the power models of various preset test scenarios—the real-time simulation module will output a new modulation signal for modulation, so as to output an AC signal to the AC side of the grid-type converter under test 5. The AC side of the grid-type converter under test 5 will generate a new AC side electrical signal, which will be input to the real-time simulation module 3. The real-time simulation module 3 will feed back the new AC side electrical signal to the power grid system to determine the AC side electrical signal of the grid-type converter under test 5 under fluctuations, thereby realizing the simulation test of the grid-type converter under test 5. Furthermore, the real-time simulation module 3 will generate a new modulation signal based on the current preset power model and the AC side electrical signal of the grid-type converter under test 5, and transmit it to the controllable test power supply 2. Among them, the real-time simulation module 3 outputs the modulation signal through the bus in the constructed preset power model.

[0094] In other embodiments, the real-time simulation module 3, based on a pre-built power model, can provide an initial reference voltage for the grid connection point simulating a real power system. Furthermore, the real-time simulation module 3 can determine the modulation signal in real time based on the unlocking total signal of the controllable test power supply 2, the DC voltage of the controllable test power supply 2, and the initial reference voltage. Specifically, firstly, the reference voltage of the grid connection point is determined in real time based on the unlocking total signal and the initial reference voltage. For example, when the unlocking total signal is valid, all selected first converters 21 in the controllable test power supply 2 are in operating state. The real-time reference voltage of the grid connection point is determined based on the product of the real-time data of the initial reference voltage and the preset start-stop coefficient. At this time, the preset start-stop coefficient increases from a first threshold to a second threshold based on a first preset rate, causing the real-time value of the reference voltage at the grid connection point to increase based on the increase of the preset start-stop coefficient until it is equal to the initial reference voltage of the grid connection point. The first threshold can be greater than or equal to 0, the second threshold is 1, and the first threshold is less than the second threshold. The first preset rate can be a constant rate, a uniform acceleration rate, or a variable rate, set according to the requirements of the actual implementation scheme. Furthermore, if the unlock signal is invalid, at least one of the first converters 21 selected by the controllable test power supply 2 is in a stopped working state. The real-time reference voltage of the grid connection point is determined based on the product of the real-time data of the initial reference voltage and the preset start-stop coefficient. At this time, the preset start-stop coefficient decreases from the second threshold to the first threshold based on a second preset rate, causing the real-time value of the reference voltage at the grid connection point to decrease based on the decrease in the preset start-stop coefficient. The second preset rate can be the same in magnitude but opposite in direction as the first preset rate, or it can be different from the first preset rate, set according to the requirements of the actual implementation scheme. Then, based on the reference voltage and the DC voltage, the modulation signal of the controllable power supply module 1 is determined in real time. For example, the modulation signal = half of the reference voltage at the grid connection point / half of the DC voltage.

[0095] It should be noted that if the preset power model is changed or the AC side electrical signal of the grid-type converter 5 under test is changed, the initial reference voltage will also change accordingly. Furthermore, the unlock signal is obtained by performing a logical operation on the unlock signals of each selected first converter 21. The DC voltage of the controllable test power supply 2 is obtained by averaging the DC bus voltage of each operating first converter 21. It should also be noted that, based on the modulation signal, the controller corresponding to the controllable test power supply 2 will output trigger pulses to the inverters of each selected first converter 21 in the controllable test power supply 2, causing the controllable test power supply 2 to modulate.

[0096] Understandably, the real-time simulation module 3 can simulate various real-world scenarios and provide different voltage conditions in a timely manner to adapt to various power system scenarios, thereby covering a wide range of operating conditions of grid-connected converters to modulate the controllable test power supply 2, which helps to thoroughly evaluate the grid-connected performance of grid-connected converters.

[0097] Please see Figures 2 to 4 As shown below, the scalable grid-type converter test system provided in this application will be described by way of example:

[0098] like Figure 2 As shown, in some embodiments, the scalable grid-type converter test system includes: an AC power supply (power module 1), a controllable test power supply 2, a real-time simulation module 3, a DC regulated power supply 4, the grid-type converter under test 5, a circuit breaker 6, a transformer 7, and a reactor 8. The controllable test power supply 2 consists of one or more first converters 21, which can be connected in parallel. Each first converter 21 includes an AC / DC converter (rectifier) ​​and a DC / AC converter (inverter). Additionally, each first converter 21 is optionally equipped with a sub-circuit breaker 61, a sub-transformer 71, and a reactor 8. The DC regulated power supply 4 consists of one or more second converters 41, which can be connected in parallel. Each second converter 41 includes an AC / DC converter (rectifier), and each second converter 41 is optionally equipped with a sub-circuit breaker 61 and a sub-transformer 71. The AC power supply is connected to the incoming sub-circuit breakers 61 corresponding to each of the first converters 21 and each of the second converters 41. The connecting reactors 8 corresponding to each of the first converters 21 are connected in parallel to the AC side of the grid-type converter 5 under test. The DC side of each of the second converters 41 is connected in parallel to the DC side of the grid-type converter 5 under test. The real-time simulation module 3, by building and running a suitable power model, is connected to the DC / AC converter signal input terminal of each of the first converters 21. The output side of the sub-circuit breaker 61 corresponding to each of the first converters 21 is connected to the I side (primary side) of the corresponding sub-transformer 71, the II side (secondary side) of the corresponding sub-transformer 71 is connected to the AC side of the internal AC / DC converter, the DC side of the internal AC / DC converter is connected to the DC side of the internal DC / AC converter, and the AC side of the internal DC / AC converter is connected to one side of the corresponding reactor 8. The output side of the corresponding sub-circuit breaker 61 of each second converter 41 is connected to the I side of the corresponding sub-transformer 71, and the II side of the corresponding sub-transformer 71 is connected to the AC side of the internal AC / DC converter.

[0099] The real-time simulation module 3 can be different real-time simulation modules such as RTDS and RTLAB. The real-time simulation module 3 can flexibly build simulation models and send the final signal to each of the first converters 21. The DC voltage output by the DC regulated power supply 4 is determined by the DC voltage required by the grid-type converter 5 under test. The AC power supply is the same. The output voltage level of the controllable test power supply 2 matches the AC side voltage level of the grid-type converter 5 under test. The output voltage level of the DC regulated power supply 4 matches the DC side voltage level of the grid-type converter 5 under test. Each first converter 21 can have an AC bus or not. Each second converter 41 can have a DC bus or not.

[0100] It should be noted that each of the second converters 41 adopts a multi-converter parallel coordinated control strategy to control the output electrical signal. Furthermore, the real-time simulation module 3 uses a synchronous output control method to output an AC reference voltage signal (modulated signal) to each of the first converters 21. Additionally, the power model built by the real-time simulation module 3 is not limited to a single model; it can be different models, depending on the testing requirements. It should also be noted that in this application, the grid-connected converter 5 under test can be any one of a grid-connected energy storage converter, a grid-connected photovoltaic converter, or a grid-connected wind power converter.

[0101] Please see Figure 2 As shown, each first converter 21 can be configured with one sub-circuit breaker 61 and one double-winding transformer. Please refer to [link / reference]. Figure 3 As shown, it can also be configured such that multiple first converters 21 share one sub-circuit breaker 61 and one multi-winding transformer 7. Please refer to [link / reference]. Figure 2 As shown, the sub-circuit breaker 61 and sub-transformer 71 corresponding to the second converter 41 can be configured such that each second converter 41 is equipped with one sub-circuit breaker 61 and one double-winding transformer. Please refer to [link / reference]. Figure 3 As shown, it can also be configured such that multiple second converters 41 share one sub-circuit breaker 61 and one multi-winding transformer 7. Please refer to [link / reference]. Figure 4 As shown, it can also be configured such that the first converter 21 and the second converter 41 share one circuit breaker 61 and one multi-winding transformer 7.

[0102] like Figure 3 As shown, for example, two sets of controllable test power supplies 2 or two sets of DC regulated power supplies 4 can share one three-winding transformer. The rated capacity of the high-voltage side winding is twice that of the low-voltage side winding, thereby reducing the number of transformers 7 and the floor space occupied.

[0103] like Figure 4 As shown, for example, one set of controllable test power supply 2 and one set of DC regulated power supply 4 share one three-winding transformer, and the capacity of the high-voltage side winding is the system loss, thereby further reducing the volume and cost of transformer 7.

[0104] Please see Figure 5 As shown, Figure 5 This is a flowchart illustrating a control method for a scalable grid-type converter testing system provided in an embodiment of this application.

[0105] Secondly, this application also provides a control method for a scalable grid-type converter test system, comprising:

[0106] Start the real-time simulation module 3. The real-time simulation module 3 outputs a modulated signal based on the AC side electrical signal of the grid-type converter 5 under test.

[0107] Start the controllable test power supply 2. Based on the set power of the grid converter 5 under test, at least one first converter 21 in the controllable test power supply 2 modulates based on the modulation signal to output an AC signal to the AC side of the grid converter 5 under test.

[0108] When the DC regulated power supply 4 is started, based on the set power of the grid converter 5 under test, at least one second converter 41 in the DC regulated power supply 4 outputs a DC signal to the DC side of the grid converter 5 under test.

[0109] Among them, the real-time simulation module 3 is used to construct a preset power system model. The preset power model includes the power model of each preset test scenario. Based on the power model of each preset test scenario and the AC side electrical signal of the grid-type converter 5 under test, the real-time simulation module 3 outputs the modulation signal corresponding to the power model of each preset test scenario.

[0110] It should be understood that the set power of the grid-type converter 5 under test refers to the set power corresponding to the capacity level of the grid-type converter to be tested.

[0111] An exemplary test system based on a scalable grid-connected converter can be described, with the control method of the system specifically following the steps outlined below:

[0112] S1: Select one or more sets of first converters 21 and one or more sets of second converters 41 according to the set power of the grid-type converter 5 under test, and close the sub-circuit 61 corresponding to each first converter 21 and second converter 41 to connect the first converter 21 and second converter 41 to the power module 1.

[0113] S2: The selected second converters 41 provide DC voltage to the network converter 5 under test;

[0114] S3: Operate the selected AC / DC converters of each first converter 21 to provide DC voltage support to the DC / AC converters;

[0115] S4: Run the real-time simulation module 3 according to the preset power model corresponding to the preset test content. The real-time simulation module synchronously sends the corresponding modulation signal to the DC / AC converter of each first converter 21 to provide AC side voltage for the grid-type converter 5 under test.

[0116] S5: Operate the grid-type converter 5 under test. The power of the grid-type converter 5 under test gradually increases to the set point P at a set rate. GFC.Set Furthermore, the AC side electrical signal of the grid-type converter 5 under test will be acquired by the real-time simulation module to update the modulation signal. It should be noted that the setpoint P... GFC.Set This refers to the target or final power value of the grid-connected converter 5 under test, which is set according to the scheme requirements. The set rate refers to the speed or rate at which the power of the grid-connected converter 5 increases. To ensure the stability of the power system, the set rate may need to be limited to a safe range to avoid impacting the grid or equipment. This can be automatically set by the controller corresponding to the grid-connected converter 5 under test. It should also be noted that the control method of the test system in this application is not limited by the order of S1 to S5; in actual execution, different sequences can be used.

[0117] Furthermore, based on the above S1 to S5 processes, the test system is started, thereby enabling the performance testing of the grid-type converter 5 under test.

[0118] It should be noted that during the operation of the real-time simulation module 3 according to the preset power model corresponding to the preset test content, the real-time simulation module 3 can perform operations such as fault simulation and load switching according to the requirements of the test content, thereby testing the relevant performance of the grid-type converter 5 under test. It should also be noted that when a test content is completed, steps S1 to S5 are repeated to proceed to the next test content; if the test content is not completed, step S5 is repeated until the test content is completed.

[0119] The testing system described in this application can simulate disturbances in power systems such as grounding faults, frequency changes, phase jumps, and overvoltages. The testing content can include, but is not limited to, fault ride-through capability testing, short-circuit current support capability testing, inertia support capability testing, harmonic suppression capability testing, reactive power compensation capability testing, and imbalance compensation capability testing. The models corresponding to the testing content can be multiple models or a single model. For each testing content, at least one of the port voltage and current data of the grid-connected converter 5 under test can be collected, and at least one of the active power, reactive power, active current, reactive current, voltage amplitude, voltage peak value, and current peak value at the ports of the grid-connected converter 5 under test can be calculated. Thus, the performance of the grid-connected converter 5 under test under the corresponding testing content can be characterized through the collected or calculated data.

[0120] In some embodiments, when multiple second converters 41 in the DC regulated power source 4 output DC signals, the multiple second converters 41 in the DC regulated power source 4 output DC signals to the DC side of the grid-type converter 5 under test based on a multi-converter parallel coordinated control strategy.

[0121] It is important to understand that each second converter 41 has its own corresponding controller. Therefore, when multiple second converters 41 in the DC regulated power supply 4 output DC signals, these multiple second converters 41, based on a multi-converter parallel coordinated control strategy, output DC signals to the DC side of the grid-type converter 5 under test. That is, any one of the multiple second converters 41 adopts a DC voltage control mode, calculates an AC current control command through its corresponding controller, and then controls the AC current of that second converter 41 according to this AC current control command. Simultaneously, the AC current control command is sent to the controllers corresponding to the other second converters 41. The other second converters 41 adopt a constant current control mode, controlling the AC current of their converters according to the received AC current command.

[0122] In some embodiments, multiple second converters 41 in the DC regulated power source 4 output DC signals to the DC side of the grid-type converter 5 under test based on a multi-converter parallel coordinated control strategy, including:

[0123] The controller of any second converter 41 determines the AC current control command through PI calculation based on the DC voltage signal on the DC side of the grid converter 5 under test and the reference voltage signal of the grid converter 5 under test.

[0124] Multiple second converters 41 in the DC regulated power source 4 output DC signals to the DC side of the grid-type converter 5 under test based on AC current control commands.

[0125] It should be understood that the multiple second converters 41 selected in the DC regulated power supply 4 execute the same AC current control command, and therefore the DC signals output by the multiple second converters 41 selected in the DC regulated power supply 4 to the DC side of the grid-type converter 5 under test are the same. Furthermore, the DC voltage signal on the DC side of the grid-type converter 5 under test refers to the DC voltage signal on the DC bus of the multiple second converters 41 connected in parallel.

[0126] Understandably, in this application, the DC regulated power source 4 outputs a DC signal to the DC side of the grid-type converter 5 under test through a multi-converter parallel coordinated control strategy. The controller of one of the second converters 41 determines the current control command based on PI (proportional-integral) calculations. Then, all the second converters 41 perform AC current control according to the current control command, thereby achieving precise DC voltage control. Specifically, the controller receives the DC side voltage signal of the grid-type converter 5 under test and compares it with the reference voltage signal corresponding to the set power. That is, it calculates the difference between the current reference voltage signal and the DC side voltage signal, and then uses PI calculation to calculate the current control command. The proportional part is responsible for quickly responding to voltage errors, while the integral part eliminates steady-state errors, ensuring the stability and accuracy of the system. Furthermore, in this application, multiple second converters 41 are connected in parallel to share the load, ensuring uniform current distribution and reducing current imbalance and related losses.

[0127] It is understood that the embodiments of this application also provide a control method for a scalable grid-type converter test system, which is applied to the scalable grid-type converter test system. Therefore, the control method for the scalable grid-type converter test system includes the effects of all the features of the scalable grid-type converter test system, which will not be elaborated here.

[0128] In summary, this application provides a scalable grid-connected converter testing system and its control method. This system integrates a real-time simulation module 3, a controllable test power supply 2, a DC regulated power supply 4, a transformer 7, a reactor 8, and a circuit breaker 6, aiming to provide an efficient and flexible testing environment for the grid-connected converter under test 5. A simulation model is built through the real-time simulation module. The common bus voltage is transmitted as a modulation signal to the controllable test power supply 2, while the electrical signal output by the grid-connected converter under test 5 is transmitted to the real-time simulation module for closed-loop simulation. The test power loop runs from the AC power supply through the controllable test power supply 2 to the grid-connected converter under test 5, and then back to the power supply module 1 through the DC regulated power supply 4. Both the controllable test power supply 2 and the DC regulated power supply 4 can be formed by paralleling at least one converter unit, ensuring a simple system structure and a flexible simulation model that can adapt to multi-functional testing of converters with different capacities. Specifically, the real-time simulation module 3 and the controllable test power supply 2 are used to simulate the AC power grid, load, and faults, while the DC regulated power supply 4 is used to simulate photovoltaic and battery characteristics. This testing system can comprehensively verify the diverse characteristics of grid-connected converters of different capacities, including control performance, protection capabilities, and various performance indicators. Its grid model is highly adjustable, has a simple structure, and offers diverse and flexible testing functions with good scalability. By flexibly configuring different numbers of controllable test power supplies 2 and DC regulated power supplies 4, the system can meet the testing requirements of converters of various capacities.

[0129] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0130] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Although this application has disclosed preferred embodiments as above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A scalable grid-type converter testing system, characterized in that, include: Power module (1); The real-time simulation module (3) is connected to the AC side of the grid-type converter (5) under test. The real-time simulation module (3) is used to output a modulation signal based on the AC side electrical signal of the grid-type converter (5) under test. The controllable test power supply (2) includes at least one first converter (21), each of the first converters (21) being connected to the power supply module (1), the real-time simulation module (3), and the AC side of the grid-type converter under test (5). At least one of the first converters (21) in the controllable test power supply (2) is used to modulate based on the modulation signal to output an AC signal to the AC side of the grid-type converter under test (5). The DC regulated power supply (4) includes at least one second converter (41), each of the second converters (41) being connected to the power module (1) and the DC side of the grid-type converter under test (5), and at least one of the second converters (41) in the DC regulated power supply (4) is used to output a DC signal to the DC side of the grid-type converter under test (5).

2. The scalable grid-type converter testing system according to claim 1, characterized in that, Also includes: A circuit breaker (6) is disposed between each of the first converters (21) and the power module (1), and between each of the second converters (41) and the power module (1).

3. The scalable grid-type converter testing system according to claim 2, characterized in that, The circuit breaker (6) includes a plurality of sub-circuit breakers (61), one end of each sub-circuit breaker (61) is connected to the power module (1), and the other end of any sub-circuit breaker (61) is connected to at least one first converter (21) and / or at least one second converter (41).

4. The scalable grid-type converter testing system according to claim 1, characterized in that, Also includes: A transformer (7) is disposed between each of the first converters (21) and the power module (1), and between each of the second converters (41) and the power module (1).

5. The scalable grid-type converter testing system according to claim 4, characterized in that, The transformer (7) includes multiple sub-transformers (71), the primary side of each sub-transformer (71) is connected to the power module (1), and the secondary winding of any sub-transformer (71) is connected to a first converter (21) or a second converter (41).

6. The scalable grid-type converter testing system according to claim 5, characterized in that, The secondary winding of the sub-transformer (71) adopts a delta connection method.

7. The scalable grid-type converter testing system according to claim 1, characterized in that, Also includes: Multiple reactors (8) are provided, with at least one of the reactors (8) between the AC side of each of the first converter (21) and the grid-type converter under test (5).

8. The scalable grid-type converter testing system according to claim 1, characterized in that, The real-time simulation module (3) is used to output a modulated signal based on the AC side electrical signal of the grid-type converter under test (5), including: Construct a preset power model, which includes power models for each preset test scenario; Based on the power model of each preset test scenario and the AC side electrical signal of the grid-type converter (5) under test, the modulation signal corresponding to the power model of each preset test scenario is output.

9. A control method for a scalable grid-type converter test system, characterized in that, include: Start the real-time simulation module (3), which outputs a modulation signal based on the AC side electrical signal of the grid converter (5) under test; Start the controllable test power supply (2), and based on the set power of the grid converter (5) under test, at least one first converter (21) in the controllable test power supply (2) is modulated based on the modulation signal to output an AC signal to the AC side of the grid converter (5) under test. When the DC regulated power supply (4) is started, based on the set power of the grid converter (5) under test, at least one second converter (41) in the DC regulated power supply (4) outputs a DC signal to the DC side of the grid converter (5) under test; The real-time simulation module (3) is used to construct a preset power system model, which includes the power model of each preset test scenario. The real-time simulation module (3) outputs the modulation signal corresponding to the power model of each preset test scenario based on the power model of each preset test scenario and the AC side electrical signal of the grid-type converter (5) under test.

10. The control method for the scalable grid-type converter test system according to claim 9, characterized in that, When multiple second converters (41) in the DC voltage regulator (4) output the DC signal, the multiple second converters (41) in the DC voltage regulator (4) output the DC signal to the DC side of the grid-type converter under test (5) based on the multi-converter parallel coordinated control strategy.

11. The control method for the scalable grid-type converter test system according to claim 10, characterized in that, The multiple second converters (41) in the DC regulated power supply (4) output the DC signal to the DC side of the grid-type converter under test (5) based on a multi-converter parallel coordinated control strategy, including: The controller of any of the second converters (41) determines the AC current control command through PI calculation based on the DC voltage signal on the DC side of the grid converter (5) under test and the reference voltage signal of the grid converter (5) under test. The multiple second converters (41) in the DC regulated power source (4) output the DC electrical signal to the DC side of the grid-type converter under test (5) based on the AC current control command.

Images