Voltage-sharing control method for cascaded H-bridge direct-hanging energy storage converter

Abstract

The invention discloses a voltage-sharing control method for a cascaded H-bridge direct-hanging energy storage converter, and the method comprises the following steps: collecting the SOC (state of charge) value of a battery of each sub-module, and carrying out the in-phase equalization calculation to obtain an in-phase equalization correction voltage; carrying out inter-phase equalization calculation based on the SOC error, and obtaining a zero-sequence voltage needing to be injected; according to the active power and the reactive power of the system, a virtual synchronous machine is adopted to control and generate a current reference value, a modulation voltage is generated based on the current reference value, and the in-phase equalization correction voltage and the zero sequence voltage are superposed to the modulation voltage; and carrying out carrier phase-shifting modulation on the superposed modulation voltage to generate an H-bridge sub-module switching signal. According to the method, in-phase and inter-phase SOC balance and power control are realized through hierarchical control, and the balance efficiency and the system reliability are improved.

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 the cascade H-bridge direct hanging type energy storage converter.

[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: A cascade H-bridge direct hanging energy storage converter voltage sharing control method, comprising the following steps: S1: Collecting the state of charge (SOC) value of each sub-module, performing intra-phase balancing calculation to obtain the intra-phase balancing correction voltage of each sub-module; S2: Based on the SOC error, performing inter-phase balancing calculation to obtain the required injected zero sequence voltage; S3: Based on the active power and reactive power of the system, generating a current reference value using virtual synchronous machine control, and generating a modulation voltage based on the current reference value, and superimposing the intra-phase balancing correction voltage and the zero sequence voltage on the modulation voltage; S4: Carrier phase shift modulation is performed on the superimposed modulation voltage to generate the switching signal of the H-bridge sub-module.

[0006] Further, step S1 comprises: Calculating the average value of the SOC of each phase battery; According to the difference between the SOC value of each submodule and the corresponding phase SOC average value, combined with the submodule reference voltage and the proportional coefficient, the intra-phase balancing correction voltage is calculated.

[0007] Further, the proportional coefficient is determined according to the battery type and the SOC imbalance degree.

[0008] Further, step S2 comprises: calculating the SOC average value of all submodules; calculating the error of each phase SOC and the SOC average value; multiplying the error by the submodule reference voltage, and then processing through the proportional integral controller to obtain the three-phase injection power; converting the three-phase injection power into two-phase coordinate system components; calculating the zero sequence voltage amplitude and phase based on the two-phase components; generating the zero sequence voltage.

[0009] Further, the calculation of the zero sequence voltage phase comprises: 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 by a preset phase value; if the first-phase component in the two-phase components is zero, the product of one-half π and the positive or negative sign is taken as the phase value according to the positive or negative of the second-phase component.

[0010] Further, the virtual synchronous machine control in step S3 comprises: detecting the three-phase output voltage and output current of the system; calculating the active power and reactive power; calculating the virtual angular velocity through the virtual inertia and damping link based on the active power reference value, the reactive power reference value and the voltage reference value; calculating the virtual potential through the reactive droop and voltage regulation link; generating the current reference value according to the virtual potential.

[0011] Further, the generation of the modulation voltage in step S3 comprises: converting the current reference value and the detected current into the rotating coordinate system; in the rotating coordinate system, combining the cross-coupling term and the proportional integral control to calculate the control output value; obtaining the modulation wave of each phase modulation voltage by inverse transforming the control output value.

[0012] Further, the superposition of the intra-phase balancing correction voltage and the zero sequence voltage to the modulation voltage in step S3 comprises: adding the intra-phase balancing correction voltage of each submodule to the zero sequence voltage to obtain the compensation modulation voltage. The compensation modulation voltage is superimposed on each phase modulation voltage.

[0013] Further, the step S4 comprises: 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.

[0014] 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.

[0015] The present application has the following beneficial effects: The present application provides a cascade H-bridge direct-hanging energy storage converter voltage sharing control method, which aims at the core problem of unbalanced battery state of charge (SOC) at the DC side of each power module of the cascade H-bridge direct-hanging grid-connected type energy storage converter, which restricts the reliable operation of the system, and proposes a hierarchical control equalization control method. The compensation modulation wave calculated by equalization is superimposed on the modulation voltage generated by the grid-connected type control method, and the control signal is generated after carrier phase shift, which 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 equalization control of the cascade H-bridge direct-hanging energy storage converter, and thus improve the reliability and engineering application ability of the system. At the same time, the advantages of this type of converter, such as strong modular expansion, low output voltage harmonic, and direct access to medium and high voltage 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.

[0016] Other beneficial effects of the embodiments of the present application will be further described below. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the overall flowchart of the equalization control method of the cascade H-bridge direct-hanging grid-connected type energy storage converter of the embodiments of the present application.

[0018] Figure 2 is the three-phase grid-connected voltage waveform diagram of the cascade H-bridge energy storage converter system of the embodiments of the present application.

[0019] Figure 3 is the intra-phase SOC equalization control block diagram of the cascade H-bridge energy storage converter system of the embodiments of the present application.

[0020] Figure 4 is the inter-phase SOC equalization control block diagram of the cascade H-bridge energy storage converter system of the embodiments of the present application.

[0021] Figure 5 The voltage equalization effect of the SOC of several modules in the A phase of the cascaded H-bridge energy storage converter system of the embodiment of the application after transformation. DETAILED DESCRIPTION

[0022] The embodiments of the application will be described in detail below. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the application and its applications.

[0023] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the embodiments of the application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0024] Referring to Figure 1 , the embodiment of the application provides a voltage equalization control method for a cascaded H-bridge direct-hanging energy storage converter, comprising the following steps: Step S1: Collect the battery 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.

[0025] In some embodiments, step S1 comprises: calculating the SOC average value of each phase battery; calculating the intra-phase balancing correction voltage by combining the difference between the SOC value of each sub-module and the corresponding phase SOC average value, the sub-module reference voltage, and the proportional coefficient. In some embodiments, the proportional coefficient is determined according to the battery type and the SOC imbalance degree.

[0026] Step S2: Perform inter-phase balancing calculation based on the SOC error to obtain the required injected zero sequence voltage.

[0027] In some embodiments, step S2 comprises: calculating the SOC average value of all sub-modules; calculating the error between the SOC of each phase and the SOC average value; multiplying the error by the sub-module reference voltage, and then processing it through a proportional-integral controller to obtain three-phase injection power; converting the three-phase injection power into two-phase coordinate system components; calculating the zero sequence voltage amplitude and phase based on the two-phase components; and generating the zero sequence voltage.

[0028] In a further preferred embodiment, the calculation of the zero sequence voltage phase comprises: performing an inverse tangent operation according to the ratio of the two-phase components, and when calculating the zero sequence voltage phase, if the first-phase component in the two-phase components is not zero, subtracting the inverse tangent value of the ratio of the two-phase components from the preset phase value; if the first-phase component in the two-phase components is zero, taking the product of one-half of π and the positive or negative sign as the phase value according to the positive or negative of the second-phase component.

[0029] Step S3: generating current reference value according to active power and reactive power of the system by using virtual synchronous machine control, and generating modulation voltage based on the current reference value, and superimposing the in-phase balance correction voltage and the zero sequence voltage to the modulation voltage.

[0030] In some embodiments, the virtual synchronous machine control in step S3 includes: detecting the three-phase output voltage and output current of the system; calculating the active power and reactive power; calculating the virtual angular velocity by a virtual inertia and damping link based on the active power reference value, the reactive power reference value and the voltage reference value; calculating the virtual potential by a reactive droop and voltage regulation link; generating the current reference value according to the virtual potential.

[0031] In further preferred embodiments, the generating modulation voltage in step S3 includes: converting the current reference value and the detected current to a rotating coordinate system; calculating a control output value in the rotating coordinate system by combining a cross-coupling term and a proportional-integral control; and inversely transforming the control output value to obtain a modulation wave of the phase modulation voltage.

[0032] In further preferred embodiments, the superimposing the in-phase balance correction voltage and the zero sequence voltage to the modulation voltage in step S3 includes: adding the in-phase balance correction voltage of each sub-module to the zero sequence voltage to obtain a compensation modulation voltage; and superimposing the compensation modulation voltage to the phase modulation voltage.

[0033] Step S4: performing carrier phase-shift modulation on the superimposed modulation voltage to generate a switching signal of the H-bridge sub-module.

[0034] In some embodiments, step S4 includes: performing carrier phase-shift modulation on the superimposed modulation voltage of each H-bridge module to output a switching signal to drive the H-bridge module. The carrier phase-shift modulation can be that the carrier frequencies of each sub-module in the same phase are the same, the phase is staggered by 2π / N (N is the number of sub-modules per phase), and the switching signal is generated by comparing the superimposed modulation voltage of each sub-module with the corresponding phase-shifted carrier.

[0035] The three-layer control of the application is formed through the following process: the first layer 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 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 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 on the modulation voltage, and the superimposed modulation voltage is subjected to carrier phase shift modulation to generate a switching signal of the H-bridge submodule.

[0036] The main technical advantage of the application is that the battery SOC imbalance core problem of the cascaded H-bridge direct hanging network type energy storage converter is innovatively solved through a 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 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 on the power control modulation voltage, and the switching signal is output after carrier phase shift, thereby finally overcoming the power distribution imbalance, device over-stress, efficiency reduction and chain failure risk caused by SOC imbalance in the traditional system on the basis of maintaining the advantages of strong modular expansion, low output voltage harmonic and direct medium and high voltage access, and greatly improving the system reliability and engineering application potential of the medium and large-scale energy storage scene.

[0037] The specific embodiments of the application, algorithm examples and experimental verification thereof are further described below.

[0038] A cascaded 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 balancing; battery state of charge inter-phase balancing; and superimposing a compensation modulation wave calculated by the balancing on a modulation voltage generated by a network type control method to generate a control signal after carrier phase shift. As a battery state of charge equalization control method based on hierarchical control, the hierarchical control realized thereby comprises: a first layer battery state of charge intra-phase balancing, a second layer battery state of charge inter-phase balancing, and a third layer power control based on network type control. This hierarchical control method can realize more efficient SOC equalization control for the cascaded H-bridge direct hanging energy storage converter. The specific control algorithm implementation process of the method is described in detail as follows:

[0039] I. Battery state of charge intra-phase balancing process The SOC average value of the batteries in each phase is calculated

[0040]

[0041] According to the difference between each module battery SOC and the average value of the phase battery SOC, multiply the reference voltage of the sub-module to get the required correction reference voltage superimposed . The expression is represented by the following formula

[0042]

[0043] The proportional coefficient is selected according to the battery type and the degree of imbalance of each phase SOC. 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.

[0044] Figure 3 The intra-phase SOC balancing control of the cascaded H-bridge energy storage converter system is shown.

[0045] II. Inter-phase battery state of charge balancing process Zero sequence voltage is injected into the cascaded H-bridge energy storage converter system to realize inter-phase SOC balancing control.

[0046] Calculate the average value of the SOC of all sub-modules

[0047]

[0048] Calculate the three-phase SOC error

[0049]

[0050] According to The reference voltage of the sub-module is multiplied , and then the three-phase injection power is obtained through the PI controller , . The PI parameters can be designed and selected according to the power loop control bandwidth and phase angle margin.

[0051] According to the Clark transformation

[0052]

[0053] The zero sequence voltage amplitude And the phase

[0054]

[0055]

[0056] Zero sequence voltage phase can be calculated by four quadrant arctangent function (atan2 (ΔP β, , ΔI α )), ΔP α =0, ΔP β =±π / 2 according to positive and negative, and quadrant adjustment can be combined.

[0057] Calculate the injection voltage

[0058]

[0059] Calculate the compensation modulation voltage of each module

[0060]

[0061] Figure 4 The inter-phase SOC equalization control of the cascaded H-bridge energy storage converter system is shown.

[0062] Three, network type control process Detect the system three-phase output voltage of the cascaded H-bridge energy storage converter And output current , calculate the real-time active power and reactive power of the energy storage converter and the grid.

[0063]

[0064]

[0065] According to the park transformation, calculate , , ,

[0066]

[0067]

[0068] Then calculate the phase angle and virtual potential according to the active power reference value , the reactive power reference value , and the voltage reference value .

[0069]

[0070]

[0071]

[0072] wherein is a virtual moment of inertia coefficient, is an active damping coefficient, is an internal electric 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.

[0073] Then the current reference value

[0074]

[0075] According to the Park transformation calculation to obtain the reference value of the d-axis and the q-axis.

[0076]

[0077] The control output value ,

[0078]

[0079] According to the Park inverse transformation, the modulation wave of each phase modulation voltage is calculated

[0080]

[0081] After the compensation modulation wave of each H-bridge module is added to each phase modulation voltage and then output switch signals are driven after carrier phase shift modulation.

[0082] Figure 2 The three-phase grid-connected voltage waveform of the cascaded H-bridge energy storage converter system of the embodiment of the application is shown. Figure 5 The voltage equalization effect of the cascaded H-bridge energy storage converter system of the embodiment of the application is shown after 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 voltage equalization strategy, it can be consistent, achieving the effect of SOC equalization.

[0083] Compared with the prior art, the application adopts a hierarchical control strategy, the first layer realizes 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 to accurately adjust the SOC equalization of each sub-module in the same phase; the second layer performs inter-phase equalization of the battery state of charge, the zero sequence voltage is calculated and injected based on the SOC error to effectively balance the SOC difference between different phases; the third layer performs power control based on network type control, the current reference value and the modulation voltage are generated by using the virtual synchronous machine control, the switching signal is generated by the carrier phase shift modulation after the intra-phase and inter-phase equalization compensation voltage is superimposed, and the power control and the SOC equalization are coordinated. The 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 network type energy storage converter, avoids the chain failure, significantly improves the efficiency of the SOC equalization control, enhances the system reliability, fully plays the advantages of the converter, such as strong modular expansion, low output voltage harmonic and direct access to the medium and high voltage grid, and is more suitable for the needs of the medium and large scale energy storage scene.

[0084] The embodiment of the application further provides a storage medium for storing a computer program, the computer program being executed to perform at least the method described above.

[0085] The embodiment of the application further provides a control device, including 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.

[0086] The embodiment of the application further provides a processor, the processor executing a computer program to perform at least the method described above.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The methods disclosed in the several method embodiments of the present application can be combined arbitrarily without conflict to obtain new method embodiments.

[0094] The features disclosed in the several product embodiments of the present application can be combined arbitrarily without conflict to obtain new product embodiments.

[0095] 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.

[0096] 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 method for controlling voltage sharing of a cascaded H-bridge direct-mounted energy storage converter, characterized in that: The following steps are involved: S1: Collect the battery state of charge (SOC) value of each submodule, perform intra-phase balancing calculation, and obtain the intra-phase balancing correction voltage of each submodule; S2: Perform phase balancing calculation based on SOC error to obtain the required injected zero-sequence voltage; S3: Generate a current reference value using virtual synchronous machine control according to the active power and reactive power of the system, generate a modulation voltage based on the current reference value, and superimpose the intra-phase balanced correction voltage and the zero-sequence voltage on the modulation voltage; S4: Perform carrier phase shift modulation on the superimposed modulated voltage to generate a switching signal of the H-bridge submodule.

2. The voltage balancing control method for a cascaded H-bridge direct-mounted energy storage converter according to claim 1, characterized in that: Step S1 includes: Calculate the average SOC value of each phase battery; The intra-phase balancing 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 balancing control method for a cascaded H-bridge direct-mounted energy storage converter according to claim 2, characterized in that: The proportional coefficient is determined according to the battery type and the SOC imbalance degree.

4. The voltage sharing control method for a cascaded H-bridge direct-mounted energy storage converter according to any one of claims 1 to 3, characterized in that: Step S2 includes: Calculate the average SOC of all submodules; Calculating the error between the SOC of each phase and the average SOC; After multiplying the error by the submodule reference voltage, the three-phase injection power is obtained by processing through a proportional-integral controller; Convert the three-phase injected power into two-phase coordinate system components; Calculating zero-sequence voltage amplitude and phase based on the two-phase components; The zero-sequence voltage is generated.

5. The voltage balancing control method for a cascaded H-bridge direct-mounted energy storage converter according to claim 4, characterized in that: The calculating of the zero-sequence voltage phase comprises: An inverse tangent operation is performed based on the ratio of the two-phase components. When calculating the zero-sequence voltage phase, if the first phase component of the two-phase components is not zero, the inverse tangent value of the ratio of the two-phase components is subtracted from the preset phase value; if the first phase component of the two-phase components is zero, the product of π divided by two and the positive or negative sign of the second phase component is taken as the phase value.

6. The voltage sharing control method for a cascaded H-bridge direct-mounted energy storage converter according to any one of claims 1 to 3, characterized in that: The virtual synchronous machine control adopted in step S3 includes: Detect the system's three-phase output voltage and output current; Calculate active power and reactive power; Based on the active power reference value, reactive power reference value and voltage reference value, the virtual angular velocity is calculated through the virtual inertia and damping link; Calculate virtual potential through reactive power droop and voltage regulation link; A current reference value is generated based on the virtual potential.

7. The voltage balancing control method for a cascaded H-bridge direct-mounted energy storage converter according to claim 6, characterized in that: Generating the modulation voltage in step S3 includes: Converting the current reference value and the sensed current into a rotating coordinate system; In the rotating coordinate system, the control output value is calculated by combining the cross-coupling term and proportional-integral control; The control output value is inversely transformed to obtain the modulation wave of each phase modulation voltage.

8. The voltage sharing control method for a cascaded H-bridge direct-mounted energy storage converter according to any one of claims 1 to 3, characterized in that: In step S3, superimposing the intra-phase balanced correction voltage and the zero-sequence voltage on the modulation voltage includes: Add the intra-phase balanced correction voltage of each submodule to the zero-sequence voltage to obtain the compensation modulation voltage; The compensation modulation voltage is superimposed on the modulation voltage of each phase.

9. The voltage sharing control method for a cascaded H-bridge direct-mounted energy storage converter according to any one of claims 1 to 3, characterized in that: Step S4 includes: Carrier phase shift modulation is performed on the superimposed modulated voltage of each H-bridge module, and a switching signal is output to drive the H-bridge module.

10. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the method for controlling voltage sharing of a cascaded H-bridge direct-mounted energy storage converter according to any one of claims 1 to 9 is implemented.

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