Test system and test method for power unit of energy storage system

Abstract

The invention provides an energy storage system power unit test system and test method, the test system comprises a main control circuit and a to-be-tested circuit, the to-be-tested circuit comprises at least one to-be-tested power unit, a current sampling module and a load reactor; the main control circuit comprises a main controller; the main controller is used for receiving a sampling load current parameter obtained by sampling the load reactor by the current sampling module; and according to the sampling load current parameters, adjustment of different modulation degrees is realized through a switching mode so as to adapt to different test environments. According to the exemplary embodiment, the testing flexibility is enhanced, and the testing efficiency of the power unit is improved.

Description

Technical Field

[0001] The present disclosure relates to the field of energy storage technology, and in particular to a testing system and a testing method for a power unit of an energy storage system. Background Art

[0002] The high-voltage cascade energy storage system has a large single-unit capacity and a high system integration. The number of cascaded units increases with the increase in capacity. If there are defects in the products that make up the energy storage system, it will affect the stable operation of the entire energy storage system. Therefore, before the formal set is completed, it is necessary to simulate the conditions of the product during actual use, and through simulation, let the product do aging testing in a simulated environment.

[0003] In the related art, a test system for a power unit of an energy storage system usually tests the communication performance of the product, and during the test, the power units are tested one by one.

[0004] It should be noted that the statements herein merely provide background information related to the present disclosure and do not necessarily constitute prior art. Summary of the invention

[0005] In view of the above problems, a testing system and a testing method for a power unit of an energy storage system are proposed to overcome the above problems or at least partially solve the above problems.

[0006] The embodiments of the present disclosure adopt the following technical solutions:

[0007] In a first aspect, a test system for a power unit of an energy storage system is provided, the test system comprising: a main control circuit and a circuit to be tested, the circuit to be tested comprising at least one power unit to be tested, a current sampling module, and a load inductor; the main control circuit comprises a main controller, the main controller is used to receive a sampled load current parameter obtained by the current sampling module sampling the load inductor; according to the sampled load current parameter, different modulation degrees are adjusted by switching to adapt to different test environments.

[0008] Preferably, the main controller communicates with the power unit to be tested via an optical fiber cable, and the main controller is also used to process the modulation index in a first manner when the sampled load current parameter is less than a; process the modulation index in a second manner when the sampled load current parameter is greater than b; and process the modulation index in a third manner when the sampled load current parameter is greater than a and less than b.

[0009] Preferably, the load reactor comprises: a plurality of parallel reactors, each reactor being configured with the same rated current and the same inductance value, and the plurality of reactors being combined in different ways to achieve different modulation degrees in response to switching by the main controller.

[0010] Preferably, the main control circuit communicates with the power unit to be tested in real time via optical fiber, so as to set a first given current, execute the startup logic control strategy, and start the software and hardware protection when performing a small current functional test; and set a second given current, execute the startup logic control strategy of multiple power units to be tested, and start the software and hardware protection when performing a large current aging test.

[0011] Preferably, the sampled load current parameters include at least the Hall current, and the main controller is also used to integrate and accumulate the modulation index with the first step size when the Hall current is less than N times the given current value; integrate and accumulate the modulation index with the second step size when the Hall current is greater than M times the given current value; and use a PI controller to fine-tune the modulation index when the Hall current is in the range of N to M times the given current value.

[0012] Preferably, the test system also includes a power supply module, which includes a voltage regulator, a transformer and at least one rectifier bridge module, the input end of the voltage regulator is connected to an AC power supply, and the output end of the voltage regulator is connected to the transformer; the output end of the transformer is connected to the circuit to be tested through the rectifier bridge module.

[0013] Preferably, the rectifier bridge module comprises a plurality of rectifier bridge modules, and the plurality of rectifier bridge modules are connected in parallel to the power supply module; the output end of the transformer is respectively connected to each cascaded power unit to be tested through the plurality of parallel rectifier bridge modules.

[0014] Preferably, the test system further comprises a liquid cooling module, and the liquid cooling module is connected to the main control circuit. The current sampling module comprises a Hall current sensor.

[0015] In a second aspect, a testing method is provided, which is applied to a testing system for a power unit of an energy storage system as described in any one of the first aspects, the method comprising: powering on the testing system; starting the power unit to be tested according to a given current value; receiving a sampled load current parameter obtained by the current sampling module from sampling the load inductor; and adjusting different modulation degrees by switching according to the sampled load current parameter to adapt to different testing environments.

[0016] At least one of the above technical solutions adopted by the exemplary embodiment can achieve the following beneficial effects:

[0017] The exemplary embodiments of the present disclosure can perform functional and aging tests on power units in batches through interactive adjustment between the main controller and the circuit to be tested, and can enable the power units to be tested to operate in conditions similar to those on site, thereby realizing long-term simulated operation and achieving an aging effect.

[0018] It should be understood that the invention summary is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of some embodiments of the present disclosure in the accompanying drawings, in which:

[0020] Figure 1 Schematic diagram of a test system for a power unit of an energy storage system in an embodiment of the present disclosure;

[0021] Figure 2 A connection diagram of a test system for a power unit of an energy storage system in an embodiment of the present disclosure;

[0022] Figure 3 A control strategy block diagram of a test system for a power unit of an energy storage system in an embodiment of the present disclosure;

[0023] Figure 4 This is a flow chart of a low current function test in an embodiment of the present disclosure;

[0024] Figure 5 This is a flow chart of a high current aging test in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0025] The principle of the present disclosure will now be described with reference to some embodiments. It should be understood that the description of these embodiments is only for illustrative purposes, and helps those skilled in the art to understand and implement the present disclosure, without any limitation to the scope of the present disclosure. The disclosure described herein can be implemented in a manner different from that described below.

[0026] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0027] References in this disclosure to "one embodiment," "an embodiment," "an exemplary embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. In addition, when a particular feature, structure, or characteristic is described in conjunction with an exemplary embodiment, whether or not explicitly described, those skilled in the art will recognize that such feature, structure, or characteristic affects incorporation into other embodiments.

[0028] It should be understood that although the terms "first" and "second" etc. may be used to describe various elements herein, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the exemplary embodiments, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. The term "and / or" as used herein includes any and all combinations of one or more of the listed terms.

[0029] The terms used herein are only for describing specific embodiments, rather than for limiting exemplary embodiments. The singular forms "one", "an", and "the" used herein also include plural forms, unless the context clearly indicates otherwise. "A group of elements" or "element set" used herein is intended to include one or more elements. It should also be understood that the terms "include", "comprise", "have", "have", "include" and / or "include", when used herein, specify the presence of the features, elements and / or parts, etc., but do not exclude the presence or addition of one or more other features, elements, parts and / or combinations thereof.

[0030] As used in this disclosure, the term "circuitry" may refer to one or more or all of the following:

[0031] (a) Hardware circuit implementation only (e.g., implementation only in analog and / or digital circuits)

[0032] (b) a combination of hardware circuitry and software, such as (where applicable):

[0033] (i) a combination of analog and / or digital hardware circuits and software / firmware; and

[0034] (ii) any portion of a hardware processor (including a digital signal processor) with software, software and memory that work together to enable a device such as a mobile phone or server to perform various functions, and

[0035] (c) A hardware circuit and / or processor, such as a microprocessor or portion of a microprocessor, that requires software (e.g., firmware) to operate, but where software is not required for operation, the software may not be present.

[0036] This definition of circuitry applies to all uses of this term in this disclosure, including in any claims. As another example, as used in this disclosure, the term circuitry also includes merely a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware implementation. The term circuitry also includes, for example, if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing network device.

[0037] The high-voltage cascade energy storage system adopts a cascade topology and control algorithm. Each phase is composed of several H-bridge energy storage converter units that are phase-shifted and superimposed in series, realizing the direct connection to the high-voltage grid without a step-up transformer. The system's single-unit power is greatly improved compared to traditional low-voltage solutions, and the single-unit rated output power range is 10MW to 30MW. It is particularly suitable for high-voltage and large-capacity energy storage applications such as grid-side energy storage peak-shaving and frequency-regulating power stations, thermal power units combined with AGC frequency regulation, and new energy power stations to increase penetration rates.

[0038] The high-voltage cascade energy storage system has a large number of cascade power units, and each unit needs to be tested and aged before it is officially completed, so as to reduce the system failure rate. The applicant has studied the relevant technology and found that the current testing methods for the power units of the high-voltage cascade system include the following.

[0039] One solution is to perform only functional testing. By simulating the control signal of the main controller, the power unit executes the corresponding input and output, which can fully verify the wiring and logic problems of the unit.

[0040] The second solution is to build a small current unit detection platform, where the power unit actually communicates with the main controller through optical fiber, and the system executes normal standby, operation, shutdown and other logics.

[0041] The above two solutions have the following problems in practical application:

[0042] The first method has limited detection capabilities because it does not actually communicate with the main controller and cannot run current, and is only used as a preliminary pre-check test.

[0043] In the second method, the power unit capacitor has a certain DC voltage and can run a small current, but it cannot perform a large current aging test, which is quite different from the actual working conditions. In addition, the small current functional test system uses one source, one load, and one controller to test only one power unit, which is very inefficient.

[0044] In an exemplary embodiment, in response to the current situation in the related art that the energy storage system power unit test is inefficient and incomplete, a test system for the energy storage system power unit with strong universality is designed. The test system can perform functional and aging tests on power units in batches through interactive adjustment of the main controller and the circuit to be tested, and can enable the power units to be tested to operate in conditions similar to those on site, realize long-term simulated operation, and achieve an aging effect.

[0045] The technical solutions provided by various embodiments of the present disclosure are described in detail below in conjunction with the accompanying drawings.

[0046] The disclosed embodiment provides a testing system for a power unit of an energy storage system. Figure 1 As shown, a schematic diagram of a test system 100 for a power unit of an energy storage system in an embodiment of the present disclosure is provided, wherein the test system 100 includes: a main control circuit 110 and a circuit to be tested 120, wherein the circuit to be tested 120 includes at least one power unit to be tested 1203, a current sampling module 1201, and a load inductor 1202; the main control circuit 110 includes a main controller 1101, and the main controller 1101 is used to receive a sampled load current parameter obtained by sampling the load inductor by the current sampling module; and according to the sampled load current parameter, different modulation degrees are adjusted by switching to adapt to different test environments.

[0047] In one example, if Figure 2 As shown, the test system includes a voltage regulator, a transformer and at least one rectifier bridge module. The input end of the voltage regulator is connected to an AC power source, and the output end of the voltage regulator is connected to the transformer; the output end of the transformer is connected to the power unit to be tested through the rectifier bridge module. The circuit to be tested includes multiple power units to be tested, such as Figure 2 The power unit A1, power unit A2 and power unit A3 shown in the figure can also be connected in parallel to perform testing simultaneously according to test requirements.

[0048] Continue to refer Figure 2 When the module to be tested includes multiple power units to be tested, the output end of the transformer is connected to multiple parallel-connected rectifier bridge modules, and each rectifier bridge module is connected to one power unit to be tested.

[0049] The test system also includes a load reactor, which is connected in a load circuit. The load reactor includes a plurality of parallel reactors, each reactor adopts the same rated current and the same inductance value, and the plurality of reactors are combined in different ways to respond to the main controller to achieve different modulation degrees through switching. The current sampling module includes a Hall current sensor for collecting the load circuit current.

[0050] In some embodiments, the main control circuit includes a main controller, which communicates with the power unit to be tested via an optical fiber cable. The main controller is also used to process the modulation index in a first manner when the sampled load current parameter is less than a; process the modulation index in a second manner when the sampled load current parameter is greater than b; and process the modulation index in a third manner when the sampled load current parameter is greater than a and less than b.

[0051] refer to Figure 2 , Figure 3 The DC power supply of the power unit to be tested is a multi-winding (isolated) transformer that passes through a three-phase uncontrolled rectifier bridge to obtain a DC voltage U of the simulated battery cluster. dc A voltage regulator is configured at the front end of the multi-winding transformer, so that the test system can test the power units of battery clusters of various DC voltage levels.

[0052] The load side of the test system is Hall current sampling and load reactor L. In one example, the power unit and the load are required to run at the rated current, so liquid cooling (equipment) is added. The power units to be tested are A1~A3 cascaded, and can be expanded to multiple cascades according to test needs.

[0053] It can be understood that in actual testing, single-unit, two-unit and three-unit combination testing can be carried out according to different test conditions, and the test system is very flexible.

[0054] The main controller communicates with the power unit and the liquid cooling module in real time through optical fiber, and has the functions of liquid cooling machine status input, emergency stop button input, load over-temperature input, etc., and outputs the operating status at the same time. The Hall element samples the load current.

[0055] In one example, let the DC link voltage be U dc , the inductance of the AC side load reactor is L, and the rated current is I N , then the full load aging operation modulation index of a single unit is Since too small a modulation degree may easily lead to large current fluctuations and unstable control, the inductance value of the reactor L needs to be relatively large.

[0056] In another example, assuming the load reactor rated current I N =600A, DC side voltage U dc =1000V, load reactor L=2.5mH, then m N =0.471, the modulation degree of the three units at full load is m N3 =0.157.

[0057] The test system disclosed in the present invention can perform low current functional test and high current aging test, wherein the low current functional test is the basic functional test of a single unit, and the high current aging test is the simultaneous test of multiple power units to be tested, i.e., full load test. When performing the low current functional test, only K1 needs to be closed for testing power unit A1, and the others are similar.

[0058] In one example, when performing a small current function test, the small current effective value is I0=30A. If it is operated according to the parameters of the aging test current, the modulation index is m0=0.02355. At this time, the modulation index is too low and can be adjusted by adjusting the load inductor.

[0059] In one example, the total inductance of the load reactor is 2.5mH, which is composed of multiple reactors connected in parallel to form a switchable load, thereby ensuring that the modulation index is a suitable value, such as setting 10 60A 25mH reactors in parallel, so that the modulation index can be adjusted by switching. The reactor used in the small current function test is a 60A 10mH reactor. At this time, the modulation index can reach m1=0.2355, and the operating conditions are improved. For the large current aging test, multiple 60A 10mH reactors are used simultaneously according to calculations.

[0060] In some embodiments, the sampled load current parameters include at least the Hall current, and the main controller is also used to integrate and accumulate the modulation index with the first step size when the Hall current is less than N times the given current value; integrate and accumulate the modulation index with the second step size when the Hall current is greater than M times the given current value; and use a PI controller to fine-tune the modulation index when the Hall current is in the range of N to M times the given current value.

[0061] refer to Figure 3 When the Hall current is less than the first preset value, such as 0.95 times the given current value, the modulation index is integrated and accumulated with a certain step length m_Step: m_Step = K i *Ts; where Ki is the integration coefficient and Ts is the sampling time.

[0062] When the Hall current is greater than the second preset value, such as 1.05 times the given current value, the modulation index is integrated and accumulated with a certain step length m_Step: m_Step = -K i *Ts; where Ki is the integration coefficient and Ts is the sampling time.

[0063] When the Hall current is between the first preset value and the second preset value, such as a given current value of 0.95 to 1.05, the PI controller is used to fine-tune the modulation index to make the test system work smoothly. Wherein, m_Step is the modulation index step, Ki is the integral coefficient, and Ts is the sampling time.

[0064] In some embodiments, the main control circuit communicates with the power unit to be tested in real time through an optical fiber, so as to set a first given current, execute a startup logic control strategy, and start software and hardware protection when performing a small current function test; and set a second given current, execute a plurality of startup logic control strategies of the power units to be tested, and start software and hardware protection when performing a large current aging test. When performing the test, the method includes: powering on the test system; starting the power unit to be tested according to a given current value; receiving a sampled load current parameter obtained by the current sampling module sampling the load reactor; and adjusting different modulation degrees by switching according to the sampled load current parameter to adapt to different test environments.

[0065] refer to Figure 4 , the low current function test process is as follows:

[0066] Perform primary wiring according to the power unit to be tested, and select a large impedance load by switching method to improve the control effect.

[0067] In the human-machine interaction interface, control the main controller to enter the small current function test mode of the corresponding unit, and set the operating parameters, including the given current value, rated current value, DC over-voltage and under-voltage protection value, etc., where the operating rated current is set to 100A.

[0068] Click "Standby" to execute the soft start process of a single power unit and determine whether the contactor action of the power unit to be tested is normal during the DC soft start process. If not, set the unit status to "Fault".

[0069] After the standby is successful, set the given current value to 30A, click "Start", and the test system executes the startup logic control strategy and executes software and hardware protection at the same time.

[0070] If a fault occurs during normal operation, the state of the power unit to be tested is set to "fault".

[0071] After normal operation, it enters standby mode, performs a discharge operation, and sets the unit state to "normal".

[0072] It can be understood that the low current functional test, on the one hand, performs a basic functional logic test on the power unit, and on the other hand, prepares for the subsequent unit aging test by setting the unit status.

[0073] refer to Figure 5 , the high current aging test process is as follows:

[0074] Connect the power units that are "normal" in the low current function test once and perform an aging test. The power units to be tested may be 1, 2, 3...Y units, and put into full load impedance;

[0075] In the human-machine interaction interface, control the main controller to enter the high-current aging test mode, and set the operating parameters, including the given current value, rated current value, DC over-voltage and under-voltage protection value, etc. The operating rated current is set to 600A.

[0076] Click "Standby" to execute the soft start process of multiple power units, and judge whether the contactor action of the power unit in the "normal state" during the DC soft start process is normal. The unit in the "fault state" will no longer execute the standby action and no fault judgment will be made.

[0077] After the standby is successful, set the given current value to 600A, click "Start", and the test system executes the startup logic control strategy of multiple power units and executes software and hardware protection at the same time.

[0078] After the rated current running time specified for aging is completed, gradually reduce the given current value to 30A.

[0079] Switch to standby mode, perform discharge operation, and complete the high current aging test.

[0080] It can be understood that the test system disclosed in the present invention can be configured with power units of various levels and is easy to expand; the current control strategy of the power unit has good adaptability to working conditions and can smoothly realize the transition from small current functional test to large current aging test, thereby improving the test efficiency. Secondly, the test platform can perform functional tests on power units with small currents, and can also adapt to large current aging tests on power units of different levels. The power unit type can be configured through parameters, and the voltage regulator can be used to simulate the operation of battery clusters at different voltage levels, thereby improving the power unit test efficiency, and also improving the resource utilization of the hardware, thereby ensuring the quality of the product when it leaves the factory.

[0081] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0082] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0083] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0084] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0085] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0086] The memory may include non-permanent storage in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0087] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0088] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0089] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0090] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A test system for a power unit of an energy storage system, characterized in that: The test system comprises: a main control circuit and a circuit to be tested, wherein the circuit to be tested comprises at least one power unit to be tested, a current sampling module, and a load reactor; the main control circuit comprises a main controller, and the main controller is used to Receiving a sampled load current parameter obtained by sampling the load reactor by the current sampling module; According to the sampled load current parameters, different modulation degrees are adjusted by switching to adapt to different test environments.

2. The test system according to claim 1, characterized in that: The main controller communicates with the power unit to be tested via an optical fiber cable, and the main controller is also used When the sampled load current parameter is less than a, the modulation index is processed according to the first method; When the sampled load current parameter is greater than b, the modulation index is processed according to the second method; When the sampled load current parameter is greater than a and less than b, the modulation index is processed according to the third method.

3. The test system according to claim 2, characterized in that: The load reactor comprises: a plurality of parallel reactors, Each reactor is configured with the same rated current and the same inductance value, and a plurality of the reactors are combined in different ways to achieve different modulation degrees in response to the switching of the main controller.

4. The test system according to claim 2, characterized in that: The main control circuit communicates with the power unit to be tested in real time through optical fiber, When performing a low current function test, a first given current is set, a startup logic control strategy is executed, and software and hardware protection is started; When performing a high-current aging test, a second given current is set, a plurality of startup logic control strategies of the power units to be tested are executed, and software and hardware protection are started.

5. The test system according to claim 1, characterized in that: The sampling load current parameter includes at least the Hall current, and the main controller is also used to When the Hall current is less than N times the given current value, the modulation index is integrated and accumulated with the first step length; When the Hall current is greater than M times the given current value, the modulation index is integrated and accumulated with a second step length; When the Hall current is in a given current value in the range of N to M times, a PI controller is used to fine-tune the modulation index.

6. The test system according to any one of claims 1 to 5, characterized in that: The test system further includes a power supply module, which includes a voltage regulator, a transformer and at least one rectifier bridge module. The input end of the voltage regulator is connected to the AC power supply, and the output end of the voltage regulator is connected to the transformer; The output end of the transformer is connected to the circuit to be tested through the rectifier bridge module.

7. The test system according to claim 6, characterized in that: The rectifier bridge module includes a plurality of rectifier bridge modules, and the plurality of rectifier bridge modules are connected in parallel to the power supply module; The output end of the transformer is connected to each cascaded power unit to be tested through a plurality of parallel-connected rectifier bridge modules.

8. The test system according to claim 6, characterized in that: The test system further comprises a liquid cooling module, and the liquid cooling module is connected to the main controller.

9. The test system according to claim 8, characterized in that: The current sampling module includes a Hall current sensor.

10. A testing method, characterized in that: A test system for a power unit of an energy storage system as claimed in any one of claims 1 to 9, wherein the method comprises: Power on the test system; According to a given current value, starting the power unit to be tested; Receiving a sampled load current parameter obtained by sampling the load reactor by the current sampling module; According to the sampled load current parameters, different modulation degrees are adjusted by switching to adapt to different test environments.

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