Microgrid dc bus midpoint potential balance control method and microgrid energy storage system

Abstract

This invention discloses a method for controlling the DC bus midpoint potential balance in a microgrid and a microgrid energy storage system. The method includes: acquiring sampled positive and negative half-bus voltage values; calculating the difference between the positive and negative half-bus voltage values ​​to obtain a DC bus voltage bias; determining a DC bus midpoint adjustment amount equal to the DC bus voltage bias amount based on the DC bus voltage bias amount when the inverter is in a charging state; determining a DC bus midpoint adjustment amount opposite to the DC bus voltage bias amount based on the DC bus voltage bias amount when the inverter is in a discharging state; and adjusting the DC bus midpoint potential based on the DC bus midpoint adjustment amount. The technical solution provided by this invention enables inverters composed of a three-level T-type topology to achieve DC bus midpoint potential balance when the microgrid system outputs phases separately, reducing the hazards caused by midpoint potential imbalance.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic energy storage power generation technology, specifically to a microgrid DC bus midpoint potential balance control method and a microgrid energy storage system. Background Technology

[0002] With the development of new energy technologies, the application of photovoltaic energy storage systems is gradually maturing. (For general information, please refer to...) Figure 1 A photovoltaic (PV) energy storage system consists of two main components: PV equipment and energy storage equipment. The PV equipment absorbs solar energy and converts it into electricity, while the energy storage equipment stores this electricity. When the PV system's power is insufficient, the energy storage system converts the stored electricity into the required AC power for the grid or loads. Among PV energy storage systems, microgrid energy storage systems are gaining increasing popularity due to their unique characteristics. In microgrid energy storage systems, the energy storage devices simulate grid characteristics during grid failures, establishing a microgrid system to ensure the normal operation of the PV equipment and loads.

[0003] Among them, for inverter power supply equipment in photovoltaic energy storage systems, the column-phase T-type three-level topology can provide single-phase unbalanced or two-phase balanced power supply, offering flexible application. Its topology diagram is shown below. Figure 2 As shown.

[0004] For column-phase T-type three-level topologies, there has always been a problem of midpoint voltage imbalance. There are many reasons for this imbalance, mainly including: inconsistent stray characteristics of the switching devices themselves, and internal factors caused by the characteristics of the converter topology itself.

[0005] However, voltage imbalance at the inverter's neutral point can cause many problems in some applications, such as voltage waveform distortion, reduced voltage levels, uneven voltage distribution on inverter switching devices, and reduced capacitor lifespan. Therefore, to ensure the inverter operates normally, it is necessary to suppress the DC component of the output voltage.

[0006] The existing voltage midpoint potential balancing strategy for the T-type three-level topology is mostly applied to off-grid power supply systems and less so to microgrid energy storage systems. However, the balancing strategy for off-grid power supply systems is not suitable for microgrid energy storage systems because off-grid power supply systems can only output power after a grid fault, cannot absorb power, and can only power electrical equipment, not photovoltaic power generation equipment. Summary of the Invention

[0007] In view of this, embodiments of the present invention provide a method for controlling the midpoint potential balance of the DC bus of a microgrid and a microgrid energy storage system, so as to solve the problem of unbalanced DC bus midpoint potential of the inverter in the phase-T three-level topology of the microgrid energy storage system.

[0008] According to a first aspect, embodiments of the present invention provide a method for controlling the neutral point potential balance of a phase-T type three-level microgrid DC bus, the method comprising:

[0009] Obtain the sampled positive and negative half-bus voltage values;

[0010] The difference between the positive and negative half-bus voltage values ​​is used to obtain the DC bus voltage bias.

[0011] When the inverter is in charging mode, the DC bus midpoint adjustment amount is determined based on the DC bus voltage bias amount, which is the same as the DC bus voltage bias amount.

[0012] When the inverter is in a discharge state, a DC bus midpoint adjustment amount that is opposite to the DC bus voltage bias amount is determined based on the DC bus voltage bias amount.

[0013] Adjust the DC bus midpoint potential based on the DC bus midpoint adjustment amount.

[0014] In some optional embodiments, determining the DC bus midpoint adjustment amount, which is the same as the DC bus voltage bias amount, based on the DC bus voltage bias amount includes:

[0015] Multiply the DC bus voltage bias by a first preset constant, where the first preset constant is a positive number.

[0016] In some optional embodiments, determining a DC bus midpoint adjustment amount that is opposite to the DC bus voltage bias amount based on the DC bus voltage bias amount includes:

[0017] Multiply the DC bus voltage bias by a second preset constant, where the second preset constant is negative.

[0018] In some optional implementations, the absolute value of the second preset constant is not equal to that of the first preset constant.

[0019] In some optional embodiments, before determining the DC bus midpoint adjustment based on the DC bus voltage bias, the method further includes:

[0020] Determine whether the DC bus voltage bias is greater than a first preset threshold, and determine whether the DC bus voltage bias is less than a second preset threshold; wherein, the first preset threshold is greater than the second preset threshold;

[0021] If the DC bus voltage bias is greater than the first preset threshold, the first preset threshold shall be used as the value of the DC bus voltage bias.

[0022] If the DC bus voltage bias is less than the second preset threshold, the second preset threshold shall be used as the value of the DC bus voltage bias.

[0023] If the DC bus voltage bias is greater than the second preset threshold and less than the first preset threshold, or equal to the first preset threshold, or equal to the second preset threshold, the value of the DC bus voltage bias remains unchanged.

[0024] According to a second aspect, embodiments of the present invention provide a phase-T type three-level microgrid DC bus neutral point potential balance control device, comprising:

[0025] The acquisition module is used to acquire the sampled positive and negative half-bus voltage values;

[0026] The calculation module is used to calculate the difference between the positive and negative half-bus voltage values ​​to obtain the DC bus voltage bias.

[0027] The determination module is used to determine a DC bus midpoint adjustment amount that is the same as the DC bus voltage bias amount based on the DC bus voltage bias amount when the inverter is in a charging state; and to determine a DC bus midpoint adjustment amount that is opposite to the DC bus voltage bias amount based on the DC bus voltage bias amount when the inverter is in a discharging state.

[0028] The adjustment module is used to adjust the DC bus midpoint potential based on the DC bus midpoint adjustment amount.

[0029] According to a third aspect, embodiments of the present invention provide an electronic device, comprising:

[0030] The system includes a memory and a processor, which are interconnected. The memory stores a computer program, which, when executed by the processor, implements any of the column-phase T-type three-level microgrid DC bus midpoint potential balance control methods described in the first aspect above.

[0031] According to a fourth aspect, embodiments of the present invention provide a microgrid energy storage system, including: photovoltaic equipment, a column-phase T-type three-level topology energy storage device, and the electronic equipment described in the third aspect above.

[0032] According to a fifth aspect, embodiments of the present invention provide a computer-readable storage medium for storing a computer program, which, when executed by a processor, implements any of the column-phase T-type three-level microgrid DC bus midpoint potential balance control methods described in the first aspect.

[0033] This invention obtains the positive and negative half-bus voltage values ​​BusVolt_P and BusVolt_N, and calculates the difference between them to obtain the DC bus voltage bias BusDiffVolt. Then, based on the DC bus voltage bias BusDiffVolt, it determines the DC bus midpoint adjustment BusDiffAdj corresponding to the overall operating condition of the inverter. This enables the inverter composed of a three-level T-type topology to achieve DC bus midpoint potential balance when the microgrid system outputs phases separately, reducing the harm caused by midpoint potential imbalance. Attached Figure Description

[0034] The features and advantages of the invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the invention in any way. In the drawings:

[0035] Figure 1 A schematic diagram of the main components of a photovoltaic energy storage system;

[0036] Figure 2 This is a schematic diagram of a column-phase T-type three-level topology;

[0037] Figure 3 A flowchart illustrating a method for controlling the neutral point potential balance of a T-type three-level microgrid DC bus, provided in an embodiment of the present invention;

[0038] Figure 4 This invention provides a schematic diagram of the control process for the output voltage of each phase during phase-separated output of a microgrid.

[0039] Figure 5 A flowchart illustrating another method for controlling the neutral point potential balance of a T-type three-level microgrid DC bus provided in this embodiment of the invention;

[0040] Figure 6 A schematic diagram of the structure of a phase-T type three-level microgrid DC bus midpoint potential balance control device provided in an embodiment of the present invention;

[0041] Figure 7 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. In the following descriptions of embodiments, "a plurality of" means two or more, unless otherwise expressly specified.

[0044] Please see Figure 3 This invention provides a method for controlling the neutral point potential balance of a T-type three-level microgrid DC bus, comprising:

[0045] S101: Obtain the sampled positive and negative half-bus voltage values ​​BusVolt_P and BusVolt_N;

[0046] S102: Calculate the difference between the positive and negative half-bus voltage values ​​BusVolt_P and BusVolt_N to obtain the DC bus voltage bias BusDiffVolt;

[0047] S103: When the inverter is in charging mode, a DC bus midpoint adjustment BusDiffAdj is determined based on the DC bus voltage bias BusDiffVolt, which is the same as the DC bus voltage bias BusDiffVolt. When the inverter is in discharging mode, a DC bus midpoint adjustment BusDiffAdj is determined based on the DC bus voltage bias BusDiffVolt, which is opposite to the DC bus voltage bias BusDiffVolt. Because it is a two-phase (i.e., two-phase) T-type three-level topology, there may be a situation where one phase is charging while the other phase is discharging. Therefore, the inverter's operating condition is determined here from the total power of the two phases, i.e., from the overall situation.

[0048] The same or opposite here means that the sign of the DC bus midpoint adjustment BusDiffAdj is the same as or opposite to the DC bus voltage bias BusDiffVolt. Specifically, if the sign of the DC bus midpoint adjustment BusDiffAdj is the same as the DC bus voltage bias BusDiffVolt, then when the DC bus midpoint adjustment BusDiffAdj is positive, the DC bus voltage bias BusDiffVolt is also positive, and when the DC bus midpoint adjustment BusDiffAdj is negative, the DC bus voltage bias BusDiffVolt is also negative. If the sign of the DC bus midpoint adjustment BusDiffAdj is opposite to the DC bus voltage bias BusDiffVolt, then when the DC bus midpoint adjustment BusDiffAdj is positive, the DC bus voltage bias BusDiffVolt is negative, and when the DC bus midpoint adjustment BusDiffAdj is negative, the DC bus voltage bias BusDiffVolt is positive.

[0049] S104: Adjust the DC bus midpoint potential based on the DC bus midpoint adjustment amount BusDiffAdj.

[0050] Column-phase T-type three-level topology as follows Figure 2 As shown, the microgrid can supply power to the L1N phase load (Load_L1N), L2N phase load (Load_L2N), and L1L2 line load (Load_L1L2) in two-phase output. The voltages of L1N and L2N phases differ by 180 degrees, which is half the line voltage of L1L2. Circuit analysis shows that when the microgrid outputs power in phases, there is a certain relationship between the phase voltage and the DC bus midpoint potential. Therefore, by controlling the voltage output of each phase, the DC bus midpoint potential can be adjusted. The control block diagram for each phase is shown below. Figure 4 As shown, the input of the voltage loop controller is obtained by adding the DC bus midpoint adjustment, DC voltage adjustment (i.e., DCV adjustment, obtained using the microgrid DCV correction strategy), inverter reference voltage, and the error of the real-time sampled voltage. The inverter current reference setpoint is obtained through the voltage loop controller. The current error value is obtained by subtracting the inverter current reference setpoint from the sampled real-time current value. The current error value is used as the input of the current loop controller, which obtains the inverter control duty cycle. This duty cycle is then output as the inverter control PWM signal through the SPWM module, ultimately achieving the purpose of outputting the inverter voltage.

[0051] This invention, through obtaining the positive and negative half-bus voltage values ​​BusVolt_P and BusVolt_N, and calculating the difference between them to obtain the DC bus voltage bias BusDiffVolt, then determines the DC bus midpoint adjustment BusDiffAdj corresponding to the overall operating condition of the inverter based on the DC bus voltage bias BusDiffVolt. This enables the inverter composed of a three-level T-type topology to achieve DC bus midpoint potential balance when the microgrid system outputs phases separately, reducing the harm caused by midpoint potential imbalance. Furthermore, this invention considers not only the discharge condition but also the condition of photovoltaic power generation equipment absorbing electrical energy, thus making it suitable for microgrid energy storage systems.

[0052] For some specific implementation methods, please refer to Figure 5 The step of determining a DC bus midpoint adjustment amount that is the same as the DC bus voltage bias amount BusDiffVolt based on the DC bus voltage bias amount BusDiffVolt includes:

[0053] Multiply the DC bus voltage bias BusDiffVolt by a first preset constant, where the first preset constant is a positive number.

[0054] For some specific implementation methods, please refer to Figure 5 The step of determining a DC bus midpoint adjustment amount opposite to the DC bus voltage bias amount BusDiffVolt based on the DC bus voltage bias amount BusDiffVolt includes:

[0055] Multiply the DC bus voltage bias BusDiffVolt by a second preset constant, where the second preset constant is negative.

[0056] Specifically, the values ​​of the first and second preset constants can be adjusted according to the actual situation, and the absolute values ​​of the first and second preset constants can be equal or unequal. Figure 5 The absolute values ​​Kp of the first and second preset constants shown are equal.

[0057] For some specific implementation methods, please refer to Figure 5 Before determining the DC bus midpoint adjustment amount based on the DC bus voltage bias BusDiffVolt, the method further includes:

[0058] Determine whether the DC bus voltage bias amount BusDiffVolt is greater than a first preset threshold HighLimit, and determine whether the DC bus voltage bias amount is less than a second preset threshold LowLimit; wherein, the first preset threshold HighLimit is greater than the second preset threshold LowLimit;

[0059] If the DC bus voltage bias BusDiffVolt is greater than the first preset threshold HighLimit, the first preset threshold HighLimit shall be used as the value of the DC bus voltage bias.

[0060] If the DC bus voltage bias BusDiffVolt is less than the second preset threshold, the second preset threshold LowLimit is used as the value of the DC bus voltage bias.

[0061] If the DC bus voltage bias BusDiffVolt is greater than the second preset threshold LowLimit and less than the first preset threshold HighLimit, or equal to the first preset threshold HighLimit, or equal to the second preset threshold LowLimit, the value of the DC bus voltage bias remains unchanged.

[0062] In this embodiment of the invention, the obtained DC bus voltage bias BusDiffVolt is range-determined to ensure that BusDiffVolt does not exceed the ranges of HighLimit and LowLimit. HighLimit and LowLimit are limits set to prevent excessive adjustment of the DC bus midpoint. Normally, HighLimit is a positive value and LowLimit is a negative value. Their absolute values ​​can be equal or adjusted according to the actual situation.

[0063] Accordingly, please refer to Figure 6 This invention provides a phase-T type three-level microgrid DC bus midpoint potential balance control device, comprising:

[0064] The acquisition module 601 is used to acquire the sampled positive and negative half-bus voltage values;

[0065] Calculation module 602 is used to calculate the difference between the positive and negative half-bus voltage values ​​to obtain the DC bus voltage bias.

[0066] The determining module 603 is used to determine a DC bus midpoint adjustment amount that is the same as the DC bus voltage bias amount based on the DC bus voltage bias amount when the inverter is in a charging state; and to determine a DC bus midpoint adjustment amount that is opposite to the DC bus voltage bias amount based on the DC bus voltage bias amount when the inverter is in a discharging state.

[0067] The adjustment module 604 is used to adjust the DC bus midpoint potential based on the DC bus midpoint adjustment amount.

[0068] This invention obtains the positive and negative half-bus voltage values ​​BusVolt_P and BusVolt_N, and calculates the difference between them to obtain the DC bus voltage bias BusDiffVolt. Then, based on the DC bus voltage bias BusDiffVolt, it determines the DC bus midpoint adjustment BusDiffAdj corresponding to the overall operating condition of the inverter. This enables the inverter composed of a three-level T-type topology to achieve DC bus midpoint potential balance when the microgrid system outputs phases separately, reducing the harm caused by midpoint potential imbalance.

[0069] In some specific implementations, the determining module 603 is used to multiply the DC bus voltage bias by a first preset constant to obtain a DC bus midpoint adjustment amount that is positive or negative and has the same sign as the DC bus voltage bias, wherein the first preset constant is a positive number.

[0070] In some specific embodiments, the determining module 603 is used to multiply the DC bus voltage bias by a second preset constant to obtain a DC bus midpoint adjustment amount that is opposite in sign to the DC bus voltage bias, wherein the second preset constant is a negative number.

[0071] In some specific implementations, the absolute value of the second preset constant is not equal to that of the first preset constant.

[0072] In some specific embodiments, the apparatus further includes:

[0073] The judgment module is used to determine whether the DC bus voltage bias is greater than a first preset threshold and whether the DC bus voltage bias is less than a second preset threshold; wherein the first preset threshold is greater than the second preset threshold.

[0074] The adjustment module is configured to: use the first preset threshold as the value of the DC bus voltage bias when the DC bus voltage bias is greater than the first preset threshold; use the second preset threshold as the value of the DC bus voltage bias when the DC bus voltage bias is less than the second preset threshold; and keep the value of the DC bus voltage bias unchanged when the DC bus voltage bias is greater than the second preset threshold and less than the first preset threshold, or equal to the first preset threshold, or equal to the second preset threshold.

[0075] The embodiments of the present invention are device embodiments based on the same inventive concept as the method embodiments described above. Therefore, for specific technical details and corresponding technical effects, please refer to the method embodiments described above, and they will not be repeated here.

[0076] This invention also provides an electronic device, such as... Figure 7As shown, the electronic device may include a processor 71 and a memory 72, wherein the processor 71 and the memory 72 can communicate with each other via a bus or other means. Figure 7 Taking the example of a connection between China and Israel via a bus.

[0077] Processor 71 can be a central processing unit (CPU). Processor 71 can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations of the above types of chips.

[0078] Memory 72, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as the program instructions / modules corresponding to the column-phase T-type three-level microgrid DC bus midpoint potential balance control method in this embodiment of the invention (e.g., Figure 6 The acquisition module 601, calculation module 602, determination module 603, and adjustment module 604 are shown. The processor 71 executes various functional applications and data processing by running non-transient software programs, instructions, and modules stored in the memory 72, thereby realizing the column-phase T-type three-level microgrid DC bus midpoint potential balance control method in the above method embodiment.

[0079] The memory 72 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created by the processor 71, etc. Furthermore, the memory 72 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 72 may optionally include memory remotely located relative to the processor 71, and these remote memories may be connected to the processor 71 via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0080] The one or more modules are stored in the memory 72, and when executed by the processor 71, they perform the following: Figure 3-5 The embodiment shown illustrates a method for controlling the neutral point potential balance of the DC bus in a T-type three-level microgrid.

[0081] For specific details regarding the aforementioned electronic devices, please refer to the relevant documentation. Figures 3 to 5 The relevant descriptions and effects in the illustrated embodiments are for understanding purposes only and will not be repeated here.

[0082] Accordingly, this embodiment of the invention also provides a microgrid energy storage system, including: photovoltaic equipment, a column-phase T-type three-level topology energy storage device, and the electronic equipment described in the previous embodiment.

[0083] Accordingly, this embodiment of the invention also provides a computer-readable storage medium for storing a computer program. When the computer program is executed by a processor, it implements the various processes of the above-described embodiment of the DC bus midpoint potential balance control method for a three-level microgrid with a phase-T type, and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0084] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, 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 technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0085] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0086] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for controlling the neutral point potential balance of a phase-T type three-level microgrid DC bus, characterized in that, The method includes: Obtain the sampled positive and negative half-bus voltage values; The difference between the positive and negative half-bus voltage values ​​is used to obtain the DC bus voltage bias. Determine whether the DC bus voltage bias is greater than a first preset threshold, and determine whether the DC bus voltage bias is less than a second preset threshold; wherein, the first preset threshold is greater than the second preset threshold; If the DC bus voltage bias is greater than the first preset threshold, the first preset threshold shall be used as the value of the DC bus voltage bias. If the DC bus voltage bias is less than the second preset threshold, the second preset threshold shall be used as the value of the DC bus voltage bias. If the DC bus voltage bias is greater than the second preset threshold and less than the first preset threshold, or equal to the first preset threshold, or equal to the second preset threshold, the value of the DC bus voltage bias remains unchanged. When the inverter is in charging mode, the DC bus midpoint adjustment amount is determined based on the DC bus voltage bias amount, which is the same as the DC bus voltage bias amount. When the inverter is in a discharge state, a DC bus midpoint adjustment amount that is opposite to the DC bus voltage bias amount is determined based on the DC bus voltage bias amount. Adjust the DC bus midpoint potential based on the DC bus midpoint adjustment amount.

2. The method of claim 1, wherein, The step of determining the DC bus midpoint adjustment amount, which is the same as the DC bus voltage bias amount, based on the DC bus voltage bias amount includes: Multiply the DC bus voltage bias by a first preset constant, where the first preset constant is a positive number.

3. The method of claim 2, wherein, The determination of a DC bus midpoint adjustment amount that is opposite to the DC bus voltage bias amount based on the DC bus voltage bias amount includes: Multiply the DC bus voltage bias by a second preset constant, where the second preset constant is negative.

4. The method of claim 3, wherein, The absolute value of the second preset constant is not equal to that of the first preset constant.

5. A column phase T-type three-level microgrid DC bus midpoint potential balance control device, characterized in that, include: The acquisition module is used to acquire the sampled positive and negative half-bus voltage values; The calculation module is used to calculate the difference between the positive and negative half-bus voltage values ​​to obtain the DC bus voltage bias; determine whether the DC bus voltage bias is greater than a first preset threshold, and determine whether the DC bus voltage bias is less than a second preset threshold; wherein, the first preset threshold is greater than the second preset threshold; if the DC bus voltage bias is greater than the first preset threshold, the first preset threshold is used as the value of the DC bus voltage bias; if the DC bus voltage bias is less than the second preset threshold, the second preset threshold is used as the value of the DC bus voltage bias; if the DC bus voltage bias is greater than the second preset threshold and less than the first preset threshold, or equal to the first preset threshold, or equal to the second preset threshold, the value of the DC bus voltage bias remains unchanged; The determination module is used to determine a DC bus midpoint adjustment amount that is the same as the DC bus voltage bias amount based on the DC bus voltage bias amount when the inverter is in a charging state; and to determine a DC bus midpoint adjustment amount that is opposite to the DC bus voltage bias amount based on the DC bus voltage bias amount when the inverter is in a discharging state. The adjustment module is used to adjust the DC bus midpoint potential based on the DC bus midpoint adjustment amount.

6. An electronic device, comprising: include: The system includes a memory and a processor, which are interconnected. The memory stores a computer program, which, when executed by the processor, implements the DC bus midpoint potential balance control method for a column-phase T-type three-level microgrid as described in any one of claims 1 to 4.

7. A microgrid energy storage system, characterized by, include: Photovoltaic equipment, column-phase T-type three-level topology energy storage device, and the electronic device as described in claim 6.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store a computer program, which, when executed by a processor, implements the method for controlling the midpoint potential balance of the DC bus of a column-phase T-type three-level microgrid as described in any one of claims 1 to 4.

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