A method for controlling voltage equalization of a cascade H-bridge direct-coupled energy storage converter

Abstract

The application discloses a kind of cascade H bridge direct hanging energy storage converter voltage-sharing control methods, comprising the following steps: acquisition each submodule battery state of charge SOC value, and the voltage of in-phase equalization correction is obtained by in-phase equalization calculation;Based on SOC error, inter-phase equalization calculation is carried out, and the zero sequence voltage to be injected is obtained;According to the active power and reactive power of system, current reference value is generated using virtual synchronous machine control, and modulation voltage is generated based on the current reference value, and the in-phase equalization correction voltage and the zero sequence voltage are superimposed to the modulation voltage;The modulation voltage after superposition is carried out carrier phase-shift modulation, and H bridge submodule switching signal is generated.The method realizes in-phase, inter-phase SOC equalization and power control by hierarchical control, and improves equalization efficiency and system reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to power electronic control technology, in particular to a cascade H-bridge direct hanging energy storage converter voltage sharing control method. BACKGROUND

[0002] The cascade H-bridge (CHB) direct hanging type network configuration energy storage converter has strong modular expansion, low output voltage harmonics, and can be directly connected to the medium and high voltage power grid, etc. It has shown significant potential in medium and large scale energy storage scenarios. However, the problem of unbalanced state of charge (SOC) of the DC side battery of each power module in the cascade H-bridge structure has become a core challenge to the reliable operation of the system. The unbalanced state of charge of the battery will lead to uneven power distribution between modules, device over-stress, system efficiency decline, and even trigger a chain of failures, which seriously limits its engineering application. Therefore, there is an urgent need for a more efficient SOC voltage sharing control method for cascade H-bridge direct hanging type energy storage converters.

[0003] It should be noted that the information disclosed in the above background section is only for understanding the background of the present application, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0004] The main purpose of the present application is to overcome the defects in the background art, and to provide a cascade H-bridge direct hanging energy storage converter voltage sharing control method, which efficiently and cooperatively solves the problem of system overall reliability decline caused by unbalanced battery SOC in the cascade H-bridge direct hanging energy storage converter.

[0005] To achieve the above purpose, the present application adopts the following technical solutions:

[0006] A cascade H-bridge direct hanging energy storage converter voltage sharing control method, comprising the following steps:

[0007] S1: Collect the state of charge (SOC) value of each sub-module, perform intra-phase balancing calculation, and obtain the intra-phase balancing correction voltage of each sub-module;

[0008] S2: Perform inter-phase balancing calculation based on the SOC error, and obtain the required injected zero sequence voltage;

[0009] S3: Generate current reference values using virtual synchronous machine control based on the active power and reactive power of the system, and generate modulation voltages based on the current reference values, and superimpose the intra-phase balancing correction voltage and the zero sequence voltage to the modulation voltages;

[0010] S4: Carrier phase shift modulation is performed on the superimposed modulation voltage to generate the switching signal of the H-bridge sub-module.

[0011] Further, step S1 comprises:

[0012] calculating the SOC average value of each phase battery;

[0013] According to the difference between the SOC value of each sub-module and the corresponding phase SOC average value, combined with the sub-module reference voltage and the proportional coefficient, the intra-phase equalization correction voltage is calculated.

[0014] Further, the proportional coefficient is determined according to the battery type and the SOC imbalance degree.

[0015] Further, step S2 comprises:

[0016] calculating the SOC average value of all sub-modules;

[0017] calculating the error of each phase SOC and the SOC average value;

[0018] After multiplying the error by the sub-module reference voltage, the three-phase injection power is obtained through the proportional integral controller;

[0019] Convert the three-phase injection power into two-phase coordinate system components;

[0020] Calculate the zero sequence voltage amplitude and phase based on the two-phase components;

[0021] Generate the zero sequence voltage.

[0022] Further, the calculation of the zero sequence voltage phase comprises:

[0023] When calculating the zero sequence voltage phase according to the arctangent operation of the two-phase component ratio, if the first-phase component in the two-phase components is not zero, the arctangent value of the ratio of the two-phase components is subtracted from the preset phase value; if the first-phase component in the two-phase components is zero, according to the positive and negative of the second-phase component, the product of π / 2 and the positive and negative sign is taken as the phase value.

[0024] Further, the virtual synchronous machine control in step S3 comprises:

[0025] Detect the three-phase output voltage and output current of the system;

[0026] Calculate the active power and reactive power;

[0027] Based on the active power reference value, the reactive power reference value and the voltage reference value, calculate the virtual angular velocity through the virtual inertia and damping link;

[0028] Calculate the virtual potential through the reactive droop and voltage regulation link;

[0029] Generate the current reference value according to the virtual potential.

[0030] Further, the generation of the modulation voltage in step S3 comprises:

[0031] transforming the current reference value and the detected current to a rotating coordinate system;

[0032] under the rotating coordinate system, combining a cross-coupling term and a proportional-integral control to calculate a control output value;

[0033] inverse transforming the control output value to obtain a modulation wave of each phase modulation voltage.

[0034] Further, the step S3 of superimposing the in-phase balancing correction voltage and the zero sequence voltage to the modulation voltage comprises:

[0035] adding the in-phase balancing correction voltage and the zero sequence voltage of each sub-module to obtain a compensation modulation voltage;

[0036] superimposing the compensation modulation voltage to each phase modulation voltage.

[0037] Further, the step S4 comprises:

[0038] carrier phase-shifted modulation is performed on the superimposed modulation voltage of each H-bridge module to output a switching signal to drive the H-bridge module.

[0039] A computer program product comprising a computer program which, when executed by a processor, implements the cascade H-bridge direct-hanging energy storage converter voltage sharing control method.

[0040] The present application has the following beneficial effects:

[0041] The present application provides a cascade H-bridge direct-hanging energy storage converter voltage sharing control method, which aims at the core problem of the unbalanced battery state of charge (SOC) of each power module on the direct current side of the cascade H-bridge direct-hanging type network-forming energy storage converter, which restricts the reliable operation of the system, and proposes a hierarchical control balancing control method. Through the first layer of in-phase balancing of the battery state of charge, the second layer of inter-phase balancing of the battery state of charge, and the third layer of power control based on network-forming control, the compensation modulation wave calculated by the balancing is superimposed to the modulation voltage generated by the network-forming control method, and then the control signal is generated through carrier phase-shifted generation. It can effectively solve the problems of uneven power distribution between modules, device over-stress, and system efficiency decline, avoid the occurrence of chain failure, realize more efficient SOC balancing control of the cascade H-bridge direct-hanging type energy storage converter, and thus improve the reliability and engineering application ability of the system. At the same time, the advantages of the type of converter, such as strong modular expansion, low output voltage harmonic, and direct access to medium and high voltage power grid, are fully utilized, and the demand of medium and large-scale energy storage scenarios is better met. Through the hierarchical collaborative control architecture, the overall reliability and engineering application potential of the cascade H-bridge direct-hanging energy storage converter under the condition of unbalanced battery SOC are fundamentally improved.

[0042] Other beneficial effects in the embodiments of the present application will be further described in the following. Attached Figure Description

[0043] Figure 1 This is a flowchart illustrating the overall process of the cascaded H-bridge direct-connected grid-type energy storage converter equalization control method according to an embodiment of the present invention.

[0044] Figure 2 This is a three-phase grid-connected voltage waveform diagram of a cascaded H-bridge energy storage converter system according to an embodiment of the present invention.

[0045] Figure 3 This is a block diagram of the intra-phase SOC equalization control of a cascaded H-bridge energy storage converter system according to an embodiment of the present invention.

[0046] Figure 4 This is a block diagram of the phase-to-phase SOC equalization control of a cascaded H-bridge energy storage converter system according to an embodiment of the present invention.

[0047] Figure 5 This describes the voltage equalization effect of the cascaded H-bridge energy storage converter system in this embodiment of the invention after the SOC transformation of several modules in phase A. Detailed Implementation

[0048] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0050] See Figure 1 This invention provides a voltage equalization control method for a cascaded H-bridge direct-connected energy storage converter, comprising the following steps:

[0051] Step S1: Collect the battery state of charge (SOC) value of each submodule, perform phase-to-phase equalization calculation, and obtain the phase-to-phase equalization correction voltage of each submodule.

[0052] In some embodiments, step S1 includes: calculating the average SOC of each phase battery; and calculating the intra-phase equalization correction voltage based on the difference between the SOC value of each submodule and the average SOC of the corresponding phase, combined with the submodule reference voltage and a scaling factor. In some embodiments, the scaling factor is determined based on the battery type and the degree of SOC imbalance.

[0053] Step S2: Perform phase-to-phase equalization calculations based on the SOC error to obtain the required injected zero-sequence voltage.

[0054] In some embodiments, step S2 comprises: calculating an average value of the SOC of all sub-modules; calculating an error of the SOC of each phase from the average value of the SOC; obtaining three-phase injection power after multiplying the error by a sub-module reference voltage and processing by a proportional-integral controller; converting the three-phase injection power into two-phase coordinate system components; calculating a zero-sequence voltage amplitude and phase based on the two-phase components; and generating the zero-sequence voltage.

[0055] In further preferred embodiments, the calculation of the zero-sequence voltage phase comprises: performing an arctangent operation according to the ratio of the two-phase components, and when calculating the zero-sequence voltage phase, if the first-phase component of the two-phase components is not zero, subtracting the arctangent value of the ratio of the two-phase components from a preset phase value; and if the first-phase component of the two-phase components is zero, taking the product of one-half of π and the positive or negative sign of the second-phase component as the phase value.

[0056] Step S3: generating a current reference value using virtual synchronous machine control according to the active power and the reactive power of the system, and generating a modulation voltage based on the current reference value, and superimposing the intra-phase balance correction voltage and the zero-sequence voltage on the modulation voltage.

[0057] In some embodiments, the virtual synchronous machine control in step S3 comprises: detecting the three-phase output voltage and the output current of the system; calculating the active power and the reactive power; calculating a virtual angular velocity through a virtual inertia and damping link based on the active power reference value, the reactive power reference value, and the voltage reference value; calculating a virtual potential through a reactive droop and voltage regulation link; and generating a current reference value according to the virtual potential.

[0058] In further preferred embodiments, the generation of the modulation voltage in step S3 comprises: converting the current reference value and the detected current into a rotating coordinate system; calculating a control output value in the rotating coordinate system in combination with a cross-coupling term and a proportional-integral control; and obtaining a modulation wave of each-phase modulation voltage by inverse transformation of the control output value.

[0059] In further preferred embodiments, the superimposition of the intra-phase balance correction voltage and the zero-sequence voltage on the modulation voltage in step S3 comprises: adding the intra-phase balance correction voltage and the zero-sequence voltage of each sub-module to obtain a compensation modulation voltage; and superimposing the compensation modulation voltage on each-phase modulation voltage.

[0060] Step S4: performing carrier phase-shifted modulation on the superimposed modulation voltage to generate a switching signal of the H-bridge sub-module.

[0061] In some embodiments, step S4 comprises: carrier phase-shift modulation of the superimposed modulation voltage of each H-bridge module, and outputting a switching signal to drive the H-bridge module. The carrier phase-shift modulation can be that the carrier frequencies of each submodule in the same phase are the same, the phase is staggered by 2π / N (N is the number of submodules per phase), and each submodule superimposed modulation voltage is compared with the corresponding phase-shifted carrier to generate a switching signal.

[0062] The three-layer control of the application is formed by the following steps: the first layer of battery state of charge intra-phase balancing corresponds to step S1, that is, the battery state of charge SOC value of each submodule is collected, intra-phase balancing calculation is performed, and the intra-phase balancing correction voltage of each submodule is obtained; the second layer of battery state of charge inter-phase balancing corresponds to step S2, that is, inter-phase balancing calculation is performed based on the SOC error, and the required injected zero sequence voltage is obtained; the third layer of power control based on network type control corresponds to steps S3 and S4, that is, according to the active power and reactive power of the system, a current reference value is generated by using virtual synchronous machine control, and a modulation voltage is generated based on the current reference value, the intra-phase balancing correction voltage and the zero sequence voltage are superimposed to the modulation voltage, and the superimposed modulation voltage is carrier phase-shift modulated to generate the switching signal of the H-bridge submodule.

[0063] The main technical advantage of the application is that the battery SOC imbalance core problem of the cascaded H-bridge direct connection network type energy storage converter is innovatively solved by the hierarchical control architecture, wherein the intra-phase balancing layer dynamically generates a correction voltage based on the difference between the submodule SOC and the average value of the phase to eliminate the difference between the modules, the inter-phase balancing layer actively adjusts the inter-phase power by calculating the three-phase SOC error and injecting a zero sequence voltage, and the virtual synchronous machine technology of the network type control layer is combined to accurately generate a current reference value and maintain the grid support function; the three layers work together to seamlessly superimpose the compensation modulation wave to the power control modulation voltage, and output the switching signal after carrier phase-shift, so that the system reliability and engineering application potential of the medium and large-scale energy storage scene are significantly improved on the basis of maintaining the advantages of strong modular expansion, low output voltage harmonic and direct medium and high voltage access, and overcoming the power distribution imbalance, device over-stress, efficiency decline and chain failure risk caused by SOC imbalance in the traditional system.

[0064] The specific embodiments of the application, algorithm examples and experimental verification are further described below.

[0065] A cascade H-bridge direct hanging network type energy storage converter equalization control method adopts hierarchical control, and the method comprises: battery state of charge intra-phase equalization; battery state of charge inter-phase equalization; and superimposing a compensation modulation wave calculated through equalization to a modulation voltage generated through a network type control method, and then generating a control signal through carrier phase shift. As a battery state of charge equalization control method based on hierarchical control, hierarchical control realized by the method comprises: first layer battery state of charge intra-phase equalization, second layer battery state of charge inter-phase equalization, and third layer power control based on network type control. The hierarchical control method can realize more efficient SOC equalization control for a cascade H-bridge direct hanging type energy storage converter. The specific control algorithm implementation process of the method is described as follows:

[0066] I. Battery state of charge intra-phase equalization process

[0067] The SOC average value of each phase battery of three phases is calculated

[0068]

[0069] According to the difference between the SOC of each module battery of each phase and the SOC average value of the battery of the phase, the reference voltage of the sub-module is multiplied to obtain the required correction reference voltage to be superimposed . The expression is represented by the following formula

[0070]

[0071] is a proportional coefficient, and the size of the proportional coefficient is related to the battery selection and the SOC imbalance degree of each phase. The battery charging and discharging capacity, the rated voltage of the sub-module and the system bandwidth can be combined to balance the response speed and stability through simulation or experiment setting.

[0072] Figure 3 The intra-phase SOC equalization control of the cascade H-bridge energy storage converter system is shown.

[0073] II. Battery state of charge inter-phase equalization process

[0074] Zero sequence voltage is injected into the cascade H-bridge energy storage converter system to realize inter-phase SOC equalization control.

[0075] The SOC average value of all sub-modules is calculated

[0076]

[0077] The three-phase SOC error is calculated

[0078]

[0079] According to The reference voltage of the submodule is multiplied by The three-phase injection power is obtained after PI controller , The PI parameters can be selected according to the power loop control bandwidth and phase angle margin.

[0080] According to the Clarke transformation calculation

[0081]

[0082] The zero-sequence voltage amplitude And the phase

[0083]

[0084]

[0085] The zero-sequence voltage phase can be calculated by the four-quadrant inverse tangent function (atan2 (ΔP β, ΔP α ) ), ΔP α =0 is taken as ΔP β ±π / 2 according to the positive and negative, and the quadrant can be adjusted.

[0086] The injection voltage is calculated

[0087]

[0088] The compensation modulation voltage of each module is calculated

[0089]

[0090] Figure 4 The inter-phase SOC equalization control of the cascaded H-bridge energy storage converter system is shown.

[0091] Three, network type control process

[0092] The system three-phase output voltage of the cascaded H-bridge energy storage converter is detected And the output current The real-time active power And the reactive power of the energy storage converter and the grid are calculated.

[0093]

[0094]

[0095] According to the Park transformation, the phase angle , , ,

[0096]

[0097]

[0098] Then, according to the active power reference value , the reactive power reference value , and the voltage reference value , the phase angle and the virtual potential are calculated.

[0099]

[0100]

[0101]

[0102] wherein is a virtual moment of inertia coefficient, is an active damping coefficient, is an internal potential virtual angular velocity, is a system rated angular velocity, is an active power-frequency droop coefficient, t is time, is a reactive droop coefficient, is a reactive voltage regulation coefficient. The virtual moment of inertia coefficient , the active damping coefficient and other parameters can be configured according to the power grid frequency support requirements and system stability requirements.

[0103] Then, the current reference value

[0104]

[0105] According to the Park transformation, the reference values of the d-axis and the q-axis are calculated .

[0106]

[0107] The control output value ,

[0108]

[0109] According to the Park inverse transformation, the modulation wave of each phase modulation voltage is calculated

[0110]

[0111] The compensation modulation wave of each H-bridge module is added to each phase modulation voltage After the carrier phase shift modulation, the switch signal is output to drive each H-bridge module.

[0112] Figure 2 The three-phase grid-connected voltage waveform of the cascaded H-bridge energy storage converter system is shown. Figure 5 The voltage equalization effect of the cascaded H-bridge energy storage converter system is shown, in which the SOC of several modules in the A phase is changed. It can be seen that the initial SOC of the modules is different, but after the equalization strategy, it can be consistent, achieving SOC equalization effect.

[0113] Compared with the prior art, the present application adopts a hierarchical control strategy, the first layer realizes the intra-phase equalization of the battery state of charge, the SOC value of the sub-module is collected and the intra-phase equalization correction voltage is calculated, the SOC equalization of each sub-module in the same phase is accurately adjusted; the second layer performs inter-phase equalization of the battery state of charge, based on the SOC error calculation and injection of zero sequence voltage, effectively balancing the SOC difference between different phases; the third layer performs power control based on the grid-forming control, generates current reference value and modulation voltage by using virtual synchronous machine control, generates switch signal after carrier phase shift modulation of the superimposed intra-phase and inter-phase equalization compensation voltage, realizes the cooperation of power control and SOC equalization. This method solves the problems of uneven power distribution, device over-stress and system efficiency reduction caused by the SOC imbalance of each power module of the cascaded H-bridge direct hanging type grid-forming energy storage converter, avoids the chain failure, significantly improves the efficiency of the SOC equalization control, enhances the system reliability, fully utilizes the advantages of the type of converter such as strong modular expansion, low output voltage harmonic, direct access to medium and high voltage grid, and better meets the needs of medium and large-scale energy storage scenarios.

[0114] The embodiment of the present application also provides a storage medium for storing a computer program, which is executed to perform at least the method described above.

[0115] The embodiment of the present application also provides a control device, which comprises a processor and a storage medium for storing a computer program; wherein the processor is used to execute the computer program to perform at least the method described above.

[0116] The embodiment of the present application also provides a processor, which executes a computer program to perform at least the method described above.

[0117] The storage medium can be implemented by any type of nonvolatile storage device, or a combination thereof. The nonvolatile memory can be a Read Only Memory (ROM), a Programmable Read-Only Memory (PROM), an Erasable Programmable Read-Only Memory (EPROM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), a Ferromagnetic Random Access Memory (FRAM), a Flash Memory, a magnetic surface storage, an optical disc or a Compact Disc Read-Only Memory (CD-ROM). The magnetic surface storage can be a magnetic disc memory or a magnetic tape memory. The storage medium described in the embodiments of the present application is intended to include, but is not limited to, these and any other suitable type of memory.

[0118] In several embodiments provided by the present application, it should be understood that the disclosed system and method can be implemented in other manners. The described device embodiments are merely schematic, and the division of the units is merely a logical function division. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed coupling or direct coupling or communication connection between the components can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0119] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e., can be located in one place or distributed on a plurality of network units; some or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0120] In addition, each functional unit in the embodiments of the present application can be integrated into one processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit; the integrated unit can be implemented in the form of hardware, or in the form of hardware plus software functional units.

[0121] Those skilled in the art can understand that all or part of the steps of the above-mentioned method embodiments can be completed by program instruction related hardware, and the foregoing program can be stored in a computer readable storage medium, and the program performs the steps of the above-mentioned method embodiments when executed; and the foregoing storage medium includes a mobile storage device, a read-only memory (ROM), a random access memory (RAM), a magnetic disc or an optical disc and various storage medium capable of storing program codes.

[0122] Alternatively, the integrated unit of the present application can be stored in a computer readable storage medium if it is realized in the form of a software function module and sold or used as an independent product. Based on such understanding, the technical solutions of the embodiments of the present application can be embodied in the form of a software product, and the computer software product is stored in a storage medium, includes several instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute all or part of the methods described in the embodiments of the present application. The foregoing storage medium includes a mobile storage device, a ROM, a RAM, a magnetic disc or an optical disc and various storage medium capable of storing program codes.

[0123] The methods disclosed in the several method embodiments of the present application can be combined arbitrarily without conflict to obtain new method embodiments.

[0124] The features disclosed in the several product embodiments of the present application can be combined arbitrarily without conflict to obtain new product embodiments.

[0125] The features disclosed in the several method or device embodiments of the present application can be combined arbitrarily without conflict to obtain new method or device embodiments.

[0126] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For those skilled in the art, without departing from the concept of the present application, a number of equivalent substitutions or obvious modifications can be made, and the same performance or use should be regarded as falling within the protection scope of the present application.

Claims

1. A voltage equalization control method for a cascaded H-bridge direct-connected energy storage converter, characterized in that, Includes the following steps: S1: Collect the state of charge (SOC) value of the battery in each submodule, perform phase-to-phase equalization calculation, and obtain the phase-to-phase equalization correction voltage for each submodule; S2: Perform phase-to-phase equalization calculations based on SOC error to obtain the required injected zero-sequence voltage; Step S2 includes: calculating the average SOC of all submodules; calculating the error between the SOC of each phase and the average SOC; multiplying the error by the submodule reference voltage and processing it through a proportional-integral controller to obtain the three-phase injected power; converting the three-phase injected power into two-phase coordinate system components; calculating the zero-sequence voltage amplitude and phase based on the two-phase coordinate system components; generating the zero-sequence voltage; S3: Based on the system's active and reactive power, a virtual synchronous machine is used to generate a current reference value, and a modulation voltage is generated based on the current reference value. The phase-to-phase equalization correction voltage and the zero-sequence voltage are superimposed on the modulation voltage. Step S3, using a virtual synchronous machine, includes: detecting the system's three-phase output voltage and output current; calculating active and reactive power; calculating virtual angular velocity based on the active power reference value, reactive power reference value, and voltage reference value, using virtual inertia and damping; calculating virtual electromotive force through reactive power droop and voltage regulation; generating a current reference value based on the virtual electromotive force. Step S3, generating the modulation voltage, includes: converting the current reference value and the detected current to a rotating coordinate system; calculating the control output value in the rotating coordinate system; and inversely transforming the control output value to obtain the modulation wave of each phase's modulation voltage. S4: Perform carrier phase-shift modulation on the superimposed modulation voltage to generate the switching signal for the H-bridge submodule.

2. The voltage equalization control method for cascaded H-bridge direct-connected energy storage converters as described in claim 1, characterized in that, Step S1 includes: Calculate the average SOC of each phase battery; The phase equalization correction voltage is calculated based on the difference between the SOC value of each submodule and the average SOC value of the corresponding phase, combined with the submodule reference voltage and the proportional coefficient.

3. The voltage equalization control method for cascaded H-bridge direct-connected energy storage converters as described in claim 2, characterized in that, The proportional coefficient is determined based on the battery type and the degree of SOC imbalance.

4. The voltage equalization control method for cascaded H-bridge direct-connected energy storage converters as described in any one of claims 1 to 3, characterized in that, The calculation of the zero-sequence voltage phase includes: When calculating the zero-sequence voltage phase, the arctangent of the ratio of the two-phase coordinate system components is performed based on the ratio of the two-phase coordinate system components. If the first phase component in the two-phase coordinate system components is not zero, the arctangent of the ratio of the two-phase coordinate system components is subtracted from the preset phase value. If the first phase component in the two-phase coordinate system components is zero, the product of half of π and the sign of the second phase component is taken as the phase value.

5. The voltage equalization control method for cascaded H-bridge direct-connected energy storage converters as described in any one of claims 1 to 3, characterized in that, In step S3, the control output value is calculated in the rotating coordinate system by combining the cross-coupling term and proportional-integral control.

6. The voltage equalization control method for a cascaded H-bridge direct-connected energy storage converter as described in any one of claims 1 to 3, characterized in that, Step S3, which involves superimposing the in-phase equalization correction voltage and the zero-sequence voltage onto the modulation voltage, includes: The in-phase equalization correction voltage of each submodule is added to the zero-sequence voltage to obtain the compensation modulation voltage; The compensation modulation voltage is superimposed on the modulation voltage of each phase.

7. The voltage equalization control method for a cascaded H-bridge direct-connected energy storage converter as described in any one of claims 1 to 3, characterized in that, Step S4 includes: The superimposed modulation voltage of each H-bridge module is subjected to carrier phase shift modulation, and a switching signal is output to drive the H-bridge module.

8. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the voltage equalization control method for cascaded H-bridge direct-connected energy storage converters as described in any one of claims 1 to 7.

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