A three-phase four-wire energy storage converter pair test system and test method

Abstract

The application provides a three-phase four-wire energy storage converter pair test system and a test method, the test system comprising a bus transformer, a controller and a plurality of energy storage converter pair test modules, the energy storage converter pair test module comprising an isolation transformer, a pre-charging power supply device and n groups of two-by-two energy storage converter pairs, each two-by-two energy storage converter pair comprising two energy storage converters, the DC sides of the two energy storage converters being connected through DC switches and DC fuses, the AC sides being connected to the two sides of the isolation transformer through AC switches respectively, one end of the pre-charging power supply device being connected to the output line of the bus transformer, and the other end being connected to the DC side of the energy storage converter; and the plurality of energy storage converter pair test modules being capable of operating in a three-phase power misplacement complementary working condition. The application can realize three-phase unbalanced operation test of the three-phase four-wire energy storage converter, without generating unbalanced working conditions on the bus transformer and the power grid, and can realize large-scale and efficient test.

Description

Technical Field

[0001] This invention provides a three-phase four-wire energy storage converter test system and test method, belonging to the field of energy storage converter test technology. Background Technology

[0002] As the core power conversion device of an energy storage system, the reliability of the power conversion system (PCS) directly affects the safe and stable operation of the energy storage power station. Factory reliability testing of PCS typically involves testing two PCS in parallel. Traditional methods can only test two PCS at a time and require separate AC power supplies and DC pre-charge power supplies. This necessitates additional power supplies, is cumbersome and inefficient, and is not conducive to large-scale, high-efficiency testing.

[0003] Importantly, for testing three-phase four-wire energy storage converters, traditional reverse-drive testing schemes do not consider the unbalanced three-phase AC power conditions, resulting in incomplete testing that fails to fully expose reliability issues.

[0004] For example, the multi-PCS module parallel drag test system with authorization announcement number CN223193045U can realize many-to-many drag tests, but it does not consider the problem of AC three-phase power imbalance. Similarly, the patent application with publication number CN120669041A can realize the synchronous charging and discharging test of multiple energy storage converters in one go, but it also does not consider the problem of AC three-phase power imbalance.

[0005] Therefore, there is an urgent need to construct a test system and test method that supports multiple three-phase four-wire energy storage converters operating under three-phase unbalanced conditions, so as to achieve comprehensive and efficient testing. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a three-phase four-wire energy storage converter parallel testing system and method, which solves the problems of the prior art being unable to operate under multiple three-phase unbalanced conditions in parallel testing of energy storage converters and the difficulty in efficiently conducting simultaneous testing of multiple energy storage converters.

[0007] Technical solution: To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a three-phase four-wire energy storage converter paired-up testing system, characterized in that it includes a bus transformer, a controller, and multiple sets of energy storage converter paired-up testing modules. Each energy storage converter paired-up testing module includes an isolation transformer, a pre-charging power supply device, and n sets of paired-up energy storage converters. Each paired-up energy storage converter includes two energy storage converters, with their DC sides connected via a DC switch and a DC fuse, and their AC sides connected to both sides of the isolation transformer via AC switches. One end of the pre-charging power supply device is connected to the output line of the bus transformer, and the other end is connected to the DC side of the energy storage converter; where n is a positive integer; the multiple sets of energy storage converter paired-up testing modules can operate under three-phase power misalignment and complementarity conditions; the controller is connected to the multiple sets of energy storage converter paired-up testing modules to control the operation of the energy storage converter paired-up testing modules.

[0009] In one specific scheme, the energy storage converter has three sets of drag test modules.

[0010] It should be noted that a three-phase AC system must have three groups, because it utilizes the interleaved three-phase power. Theoretically, it can also have multiples of three groups, but it is not necessary.

[0011] In a specific scheme, the three-phase power misalignment and complementarity operating condition is as follows: the first group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the test module. A1 ,P B1 ,P C1 = (P1, P2, P3); The second group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the drag test module. A2 ,P B2 ,P C2 = (P2, P3, P1); The third group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the drag test module. A3 ,P B3 ,P C3 ) = (P3, P1, P2); where P A1 P represents the A-phase power of the first energy storage converter. B1 P represents the B-phase power of the first energy storage converter. C1 P represents the C-phase power of the first energy storage converter. A2 P represents the A-phase power of the second energy storage converter. B2 P represents the B-phase power of the second energy storage converter. C2 P represents the C-phase power of the second energy storage converter. A3 P represents the A-phase power of the third energy storage converter. B3 P represents the B-phase power of the third energy storage converter.C3 P1 represents the C-phase power of the third energy storage converter; P2 and P3 represent the three-phase power settings of the energy storage converter.

[0012] In one specific embodiment, the pre-charging power supply device is connected to the DC side of n pairs of energy storage converters via n sets of DC relays; the controller is connected to the DC relays to control the opening and closing of the DC relays.

[0013] In one specific embodiment, the pre-charge power supply device includes a voltage regulating transformer, a three-phase full-bridge uncontrolled rectifier circuit, and an overcurrent protection fuse arranged in sequence.

[0014] Preferably, the pre-charging power supply device also includes a switching switch, which is located at the input end, that is, between the output lines of the voltage regulating transformer and the bus transformer. This allows for independent switching of the pre-charging circuit without affecting the power supply of the bus transformer to other modules, thus preventing pre-charging faults from affecting the overall system.

[0015] In one specific scheme, the pulse phase of the energy storage converters in the same group is synchronized with that of the energy storage converters operating under the same conditions in the drag test module.

[0016] In one specific scheme, energy storage converters in the same group of the test modules operating under the same conditions are connected via a bus, and the mode is one master and multiple slaves. The energy storage converters in each group of the test modules operating in AC power control mode and the energy storage converters operating in DC voltage control mode are separately connected to form a pulse phase synchronization network.

[0017] Setting pulse phase synchronization can avoid circulating current problems in energy storage converters caused by common-mode voltage differences resulting from asynchrony.

[0018] In one specific scheme, an incoming line switch and an output main switch are also included. The incoming line switch is connected between the power grid and the bus transformer, and the output main switch is connected to the output terminal of the bus transformer.

[0019] Secondly, the present invention provides a testing method for a drag-and-drop test system based on any one of the claims of the first aspect, comprising: step S1: controlling the drag-and-drop test system to power on, and closing the AC switch and DC switch of the primary circuit; step S2: controlling the DC relay of the pre-charging power supply device to close, supplying power to the DC side of all energy storage converters, and controlling the energy storage converters in DC voltage control mode to complete the DC capacitor pre-charging; step S3: controlling the DC relay of the pre-charging power supply device to open, and controlling all energy storage converters in DC voltage control mode to start up according to the set DC voltage. Step S4: Control all energy storage converters in AC power control mode to start up and run at zero power. During operation, power commands are sent to multiple energy storage converters in power operation mode in the drag test module according to the three-phase power mismatch and complementarity condition. Switch between different three-phase power settings. The switching process uses gradual commands to be sent simultaneously. Step S5: Control the energy storage converters in AC power control mode and DC voltage control mode to shut down in sequence. Change the control mode of the energy storage converter and repeat steps S2 to S5. Step S6: Control the drag test system to power down.

[0020] It should be noted that the primary circuit refers to the main circuit, which is the core circuit in the drag test system that carries the main current and directly realizes the transmission of electrical energy.

[0021] Preferably, switching the control mode of the energy storage converter means switching the energy storage converter, which was originally set to DC voltage control mode, to AC power control mode; at the same time, switching the energy storage converter, which was originally set to AC power control mode, to DC voltage control mode.

[0022] In a specific scheme, the three-phase power mismatch and complementarity working condition is as follows: the first group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the test module. A1 ,P B1 ,P C1 = (P1, P2, P3); The second group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the drag test module. A2 ,P B2 ,P C2 = (P2, P3, P1); The third group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the drag test module. A3 ,P B3 ,P C3 ) = (P3, P1, P2); where P A1 P represents the A-phase power of the first energy storage converter. B1 P represents the B-phase power of the first energy storage converter. C1 P represents the C-phase power of the first energy storage converter.A2 P represents the A-phase power of the second energy storage converter. B2 P represents the B-phase power of the second energy storage converter. C2 P represents the C-phase power of the second energy storage converter. A3 P represents the A-phase power of the third energy storage converter. B3 P represents the B-phase power of the third energy storage converter. C3 P1 represents the C-phase power of the third energy storage converter; P2 and P3 represent the three-phase power settings of the energy storage converter.

[0023] Beneficial effects:

[0024] The dual-drive testing system provided by this invention includes multiple sets of energy storage converter dual-drive testing modules. Each set of dual-drive testing modules includes an isolation transformer, a pre-charging power supply device, and n sets of paired energy storage converters. Each set of dual-drive testing modules can complete the testing of 2n energy storage converters, which solves the problem that the traditional method can only test two at a time and requires separate configuration of AC power supply and DC pre-charging power supply. The testing system provided by this invention does not require the configuration of an additional power supply and is simple to operate, enabling large-scale and efficient testing.

[0025] The reverse-drive testing system provided by this invention has three sets of reverse-drive testing modules that can operate under three-phase power misalignment and complementarity conditions. This enables the testing of three-phase unbalanced operation of a three-phase four-wire energy storage converter without generating unbalanced conditions on the bus transformer and the power grid. It solves the problems of traditional reverse-drive testing schemes that do not consider AC three-phase power imbalance conditions and have complex testing systems, thus achieving comprehensive and efficient testing of energy storage converters. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of the drag testing system in this invention;

[0027] Figure 2 This is a schematic diagram of a ring network shared by the synchronization network and the control network in this invention;

[0028] Figure 3 This is a schematic diagram of the multi-channel switching of the pre-charge power supply device in this invention;

[0029] Figure 4 This is a flowchart illustrating the drag testing method in this invention. Detailed Implementation

[0030] The invention will now be further described with reference to the accompanying drawings.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] This invention provides a test system for paired energy storage converters, including a bus transformer, a controller, and multiple sets of paired energy storage converter test modules. Each paired energy storage converter test module includes an isolation transformer, a pre-charging power supply device, and n sets of paired energy storage converters. Each paired energy storage converter consists of two energy storage converters. The DC sides of the two energy storage converters are connected via a DC switch and a DC fuse, while their AC sides are connected to both sides of the isolation transformer via AC switches. One end of the pre-charging power supply device is connected to the output line of the bus transformer, and the other end is connected to the DC side of the energy storage converter. Here, n is a positive integer. The multiple sets of paired energy storage converter test modules can operate under three-phase power misalignment and complementarity conditions. The controller is connected to the multiple sets of paired energy storage converter test modules to control their operation.

[0033] The paired-drive testing system provided by this invention includes multiple sets of paired-drive energy storage converter testing modules. Each paired-drive testing module includes an isolation transformer, a pre-charging power supply device, and n sets of paired-drive energy storage converters. Each paired-drive testing module can complete the testing of 2n energy storage converters, solving the problem that the traditional method can only test two at a time and requires separate configuration of AC power supply and DC pre-charging power supply. The testing system provided by this invention does not require the configuration of an additional power supply and is simple to operate, enabling large-scale and efficient testing.

[0034] The reverse-drive testing system provided by this invention has three sets of reverse-drive testing modules that can operate under three-phase power misalignment and complementarity conditions. This enables the testing of three-phase unbalanced operation of a three-phase four-wire energy storage converter without generating unbalanced conditions on the bus transformer and the power grid. It solves the problems of traditional reverse-drive testing schemes that do not consider AC three-phase power imbalance conditions and have complex testing systems, thus achieving comprehensive and efficient testing of energy storage converters.

[0035] Example 1

[0036] Please see Figure 1 This embodiment provides a test system for energy storage converters, including: an incoming line switch, a bus transformer, an output main switch, a controller, a switch, and three sets of energy storage converter test modules.

[0037] Each energy storage converter pairing test module consists of 2n energy storage converters, operating in pairs. It also includes one isolation transformer, one pre-charge power supply, 2n AC switches, 2n DC switches, and n DC fuses, where n is a positive integer. The DC sides of the two energy storage converters are connected together via DC switches and DC fuses, while their AC sides are connected to both sides of the isolation transformer via AC switches.

[0038] The pre-charging power supply unit includes a voltage regulating transformer, a three-phase full-bridge uncontrolled rectifier circuit, an overcurrent protection fuse, and a switching switch. Power is drawn from the output line of the bus transformer, and the rectified DC voltage is connected to the DC side of n pairs of energy storage converters via n sets of high-voltage DC relays. The opening and closing of the DC relays can be controlled by a controller.

[0039] In this embodiment, n is 5. The number of energy storage converters in the three sets of energy storage converter-to-charge test modules is 30, numbered PCS1-1~5, PCS2-1~5, PCS3-1~5, PCS4-1~5, PCS5-1~5, and PCS6-1~5. The AC switches on both sides of the energy storage converters are numbered ACK1-1~5, ACK2-1~5, ACK3-1~5, ACK4-1~5, ACK5-1~5, and ACK6-1~5, and the DC switches are numbered DCK1-1~5, DCK2-1~5, DCK3-1~5, DCK4-1~5, DCK5-1~5, and DCK6-1~5. They are divided into PCS #1 to PCS #6 groups, and each group is connected via CAN bus networking, with a master-slave configuration to achieve pulse phase synchronization.

[0040] The DC sides of the energy storage converters in PCS #1 and PCS #2 are connected one-to-one via DC fuses, numbered FU1-1 to FU1-5; the DC relays connected to the pre-charge power supply 1 on the aforementioned DC side are numbered DCJ1-1 to FU1-5; all energy storage converters are connected to the switch via network cables, and the controller is networked through the switch to control the operating status of all energy storage converters and to control the status of the DC relays output by all pre-charge power supplies through the output ports.

[0041] For further details, please refer to Figure 2 Each energy storage converter can share the same network with the controller control network in the pulse phase synchronization function of the drag test module. It adopts a daisy-chain ring network method, which saves the need to build a separate synchronization network and improves the convenience of network wiring.

[0042] The energy storage converters of PCS #1 and PCS #2 are located in the first pair of towing control modules, the energy storage converters of PCS #3 and PCS #4 are located in the second pair of towing control modules, and the energy storage converters of PCS #5 and PCS #6 are located in the third pair of towing control modules.

[0043] Please see Figure 4 This embodiment provides a control method for a test system consisting of multiple three-phase four-wire energy storage converters, specifically including the following steps: First, according to this embodiment... Figure 1 Set up the test system, and sequentially close the control power supply, the AC switch of the primary circuit, and the DC switch to supply power to the test system; set the PCS #1, PCS #3, and PCS #5 energy storage converters to operate in DC voltage control mode, and set the PCS #2, PCS #4, and PCS #6 energy storage converters to operate in AC power control mode; check the monitoring backend to ensure that the controller and energy storage converters communicate normally, the energy storage converters are synchronized normally, the switch status is normal, and the voltage and current sampling is normal.

[0044] Please see Figure 3 The system controls all DC relays of the pre-charging power supply device to close and supply power to the DC side of all energy storage converters. Then, it controls the energy storage converters of PCS #1, PCS #3, and PCS #5 in DC voltage control mode to complete the DC capacitor pre-charging.

[0045] Optionally, the energy storage converter in DC voltage control mode can simultaneously issue DC capacitor pre-charge commands, which requires a large pre-charge power supply capacity; or it can issue DC capacitor pre-charge commands sequentially, which requires a smaller pre-charge power supply capacity, but the total time also increases.

[0046] After the DC capacitors of the energy storage converters in PCS #1, PCS #3, and PCS #5 in DC voltage control mode are pre-charged, the DC relays of the pre-charge power supply device are disconnected, and the controller controls all energy storage converters in DC voltage control mode to operate according to the set DC voltage.

[0047] Subsequently, the controller controls all AC power control modes of PCS #2, PCS #4, and PCS #6 energy storage converters to start operation according to the principle of alternating power complementarity, setting the AC phase power of each phase. The specific power is: the three-phase AC power of PCS #2 in the first energy storage converter connected to the test module (P A1 ,P B1 ,P C1 =(P1,P2,P3), the three-phase AC power (P) of PCS #4 group in the second group of energy storage converters in the test module. A2 ,P B2 ,P C2 = (P1,P2,P3), the three-phase AC power (P) of PCS #6 group in the third group of energy storage converters in the test module. A3 ,P B3 ,P C3= (P1,P2,P3), where P1, P2, and P3 are single-phase power values ​​that can be independently set according to the requirements of unbalanced operating conditions.

[0048] Specifically, for three-phase balanced operation, P1=P2=P3=Pn / 3 is set, where Pn is the rated power of the energy storage converter, including rectification and inverter operation. For three-phase unbalanced operation, under single-phase load, P1=Pn / 3, P2=P3=0, or P2=Pn / 3, P1=P3=0, or P3=Pn / 3, P1=P2=0. For two-phase unbalanced operation, P1=P2=Pn / 3, P3=0, or P2=P3=Pn / 3. P1=0, or P3=P1=Pn / 3, P2=0; For the two-phase power complementary operation, specifically set P1=-P2=2Pn / 3√(3), P3=0, or P2=-P3=2Pn / 3√(3), P1=0, or P3=-P1=2Pn / 3√(3), P2=0; These unbalanced operation conditions correspond to the rated current of the N-phase output, which is the maximum unbalanced operation condition. Running these operation conditions in sequence can cover the operating conditions of the three-phase four-wire energy storage converter to the maximum extent.

[0049] When the energy storage converters in PCS #2, PCS #4, and PCS #6 are operating in AC power control mode, the energy storage converters in PCS #1, PCS #3, and PCS #5, operating in DC voltage control mode, provide DC-side voltage and power support, corresponding to balanced three-phase power output on the AC side. Although the total three-phase power of each energy storage converter paired with the test module is unbalanced, the three energy storage converters operate under a three-phase power misalignment and complementarity condition. After mutual cancellation, only balanced three-phase power is needed to compensate for system losses at the bus transformer and the power grid system.

[0050] In accordance with the aging test requirements, the power-paired delayed control energy storage converter should be shut down first, followed by the energy storage converter in AC power control mode, and then the energy storage converter in DC voltage control mode.

[0051] Optionally, the control mode of the energy storage converter can be switched. That is, the energy storage converters of PCS #1, PCS #3, and PCS #5, which were originally in DC voltage control mode, can be set to AC power operation mode, and the energy storage converters of PCS #2, PCS #4, and PCS #6, which were originally in AC power control mode, can be set to DC power control mode. The above steps of pre-charging, starting up, power matching, and stopping can be repeated.

[0052] After the energy storage converter test is completed, disconnect the AC switch, DC switch, and secondary control power supply of the primary circuit in sequence, and then remove the test wiring to end the test.

[0053] In summary, this application achieves three-phase unbalanced operation testing of three-phase four-wire energy storage converters by setting up three sets of paired test modules operating under three-phase power mismatch and complementarity conditions, without generating unbalanced conditions on the bus transformer and the power grid. Furthermore, the hierarchical design of the test system allows for simultaneous testing and operation of multiple energy storage converters within each paired system, offering flexible expansion and high testing efficiency. This method solves the problems of traditional paired testing schemes, such as not considering AC three-phase power imbalance conditions and complex test systems, achieving comprehensive and efficient testing of energy storage converters.

[0054] Through the above-described configuration, this invention also has the following advantages: 1. It can perform three-phase unbalanced operation testing of three-phase four-wire energy storage converters without causing imbalance to the power grid, greatly improving the comprehensiveness of the test. 2. The test system is designed in a hierarchical manner, allowing multiple energy storage converters to be tested and operated simultaneously in each pair of systems, providing flexible expansion and high testing efficiency. 3. The entire system issues operating commands through a controller, making the system flexible and easy to control.

[0055] Example 2

[0056] Based on the same inventive concept as Embodiment 1, this embodiment provides a testing method. This testing method is implemented based on the testing system of Embodiment 1, and includes the following steps: Step S1: Powering on the test system and closing the AC and DC switches of the primary circuit; Step S2: Closing the DC relay of the pre-charging power supply device to supply power to the DC side of all energy storage converters, and controlling the energy storage converters in DC voltage control mode to complete DC capacitor pre-charging; Step S3: Disconnecting the DC relay of the pre-charging power supply device, and controlling all energy storage converters in DC voltage control mode to perform pre-charging according to the set parameters. DC voltage start-up operation; Step S4: Control all energy storage converters in AC power control mode to start up and run at zero power. During operation, power commands are sent to multiple energy storage converters in the power operation mode of the drag test module according to the three-phase power mismatch and complementarity condition. Switch between different three-phase power settings. The switching process uses gradual commands to be sent simultaneously; Step S5: Control the energy storage converters in AC power control mode and DC voltage control mode to shut down in sequence; Change the control mode of the energy storage converter and repeat steps S2 to S5; Step S6: Control the drag test system to power down.

[0057] Furthermore, the three-phase power mismatch and complementarity operating condition is specifically as follows: the first group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the test module. A1 ,P B1 ,P C1 = (P1, P2, P3); The second group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the drag test module.A2 ,P B2 ,P C2 = (P2, P3, P1); The third group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the drag test module. A3 ,P B3 ,P C3 ) = (P3, P1, P2); where P A1 P represents the A-phase power of the first energy storage converter. B1 P represents the B-phase power of the first energy storage converter. C1 P represents the C-phase power of the first energy storage converter. A2 P represents the A-phase power of the second energy storage converter. B2 P represents the B-phase power of the second energy storage converter. C2 P represents the C-phase power of the second energy storage converter. A3 P represents the A-phase power of the third energy storage converter. B3 P represents the B-phase power of the third energy storage converter. C3 P1 represents the C-phase power of the third energy storage converter; P2 and P3 represent the three-phase power settings of the energy storage converter.

[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A three-phase four-wire energy storage converter reverse-drive testing system, characterized in that, include: Busbar transformer; A multi-group energy storage converter paired-up test module is provided. The module includes an isolation transformer, a pre-charging power supply unit, and n pairs of paired energy storage converters. Each pair of paired energy storage converters consists of two energy storage converters. The DC sides of the two energy storage converters are connected via DC switches and DC fuses, while their AC sides are connected to both sides of the isolation transformer via AC switches. One end of the pre-charging power supply unit is connected to the output line of the bus transformer, and the other end is connected to the DC side of the energy storage converter. Here, n is a positive integer. Multiple sets of the aforementioned energy storage converters can be used to drive the test modules under three-phase power mismatch and complementation conditions; A controller is connected to multiple sets of energy storage converter-to-charge test modules to control the operation of the energy storage converter-to-charge test modules; The three-phase power misalignment and complementarity operating condition is as follows: The first group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the drag test module. A1 ,P B1 ,P C1 = (P1, P2, P3); The second group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the drag test module. A2 ,P B2 ,P C2 = (P2, P3, P1); The third group of energy storage converters controls the three-phase AC power (P) of the energy storage converters in the power operation mode of the drag test module. A3 ,P B3 ,P C3 = (P3, P1, P2); Among them, P A1 P represents the A-phase power of the first energy storage converter. B1 P represents the B-phase power of the first energy storage converter. C1 P represents the C-phase power of the first energy storage converter. A2 P represents the A-phase power of the second energy storage converter. B2 P represents the B-phase power of the second energy storage converter. C2 P represents the C-phase power of the second energy storage converter. A3 P represents the A-phase power of the third energy storage converter. B3 P represents the B-phase power of the third energy storage converter. C3 P1 represents the C-phase power of the third energy storage converter; P2 and P3 represent the three-phase power settings of the energy storage converter.

2. The energy storage converter-to-charge test system according to claim 1, characterized in that, The energy storage converter has three sets of drag test modules.

3. The three-phase four-wire energy storage converter test system according to claim 1, characterized in that, The pre-charging power supply device is connected to the DC side of n pairs of energy storage converters through n sets of DC relays respectively. The controller is connected to the DC relay to control the opening and closing of the DC relay.

4. The three-phase four-wire energy storage converter test system according to claim 3, characterized in that, The pre-charge power supply device includes a voltage regulating transformer, a three-phase full-bridge uncontrolled rectifier circuit, and an overcurrent protection fuse arranged in sequence.

5. The energy storage converter-to-charge test system according to claim 1, characterized in that, The pulse phase of the energy storage converters in the same group is synchronized with that of the energy storage converters under the same operating conditions in the drag test module.

6. The energy storage converter-to-charge test system according to claim 5, characterized in that, Energy storage converters in the same group of the test modules operating under the same conditions are connected via a bus and are in a master-slave mode. In each group of the test modules, the energy storage converters operating in AC power control mode and the energy storage converters operating in DC voltage control mode form a separate pulse phase synchronization network.

7. The energy storage converter-to-charge test system according to claim 1, characterized in that, It also includes an incoming line switch and an output main switch, wherein the incoming line switch is connected between the power grid and the bus transformer, and the output main switch is connected to the output terminal of the bus transformer.

8. A test method for a drag test system based on the energy storage converter as described in claim 3, characterized in that, include: Step S1: Power on the control system for the drag test and close the AC and DC switches of the primary circuit; Step S2: Control the DC relay of the pre-charging power supply device to close, supply power to the DC side of all energy storage converters, and control the energy storage converters in DC voltage control mode to complete the DC capacitor pre-charging. Step S3: Control the DC relay of the pre-charge power supply device to disconnect, and control all energy storage converters in DC voltage control mode to start up and run according to the set DC voltage; Step S4: Control all energy storage converters in AC power control mode to start up and run at zero power. During operation, power commands are sent to multiple energy storage converters in the power operation mode of the power supply test module according to the three-phase power mismatch and complementation condition. Switch between different three-phase power settings. The switching process uses gradual commands to be sent simultaneously. Step S5: Sequentially shut down the energy storage converter in AC power control mode and the energy storage converter in DC voltage control mode; switch the control mode of the energy storage converter and repeat steps S2 to S5. Step S6: Power off the drag test system.

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