Energy storage equipment control strategy suitable for power module series-parallel connection

Abstract

The invention relates to the technical field of high-voltage chain type energy storage control, in particular to an energy storage equipment control strategy suitable for power module series-parallel connection. An active current control strategy is adopted for the B-type power module; through power module current closed-loop control, the total output current after cascade connection of the A-type power module and the B-type power module is coordinated and controlled, and the control of the output current of the cascade type converter is completed by adjusting the voltage of an output reactor. The cascade reactive power compensation system has the advantages that in an existing cascade reactive power compensation device composed of pure A-type power modules, only a small number of B-type power modules need to be additionally arranged to be combined with software upgrading, the device can be transformed into the energy storage system with the active power adjusting capacity, an original device body is reused to the maximum extent, overall scrapping and replacement of the device are avoided, and the energy saving and emission reduction effects are achieved. The cost and the period of upgrading from traditional reactive compensation to energy storage transformation are greatly reduced, and the method has extremely high engineering application value and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of high-voltage chain energy storage control technology, and in particular to a control strategy for energy storage devices suitable for hybrid power module connections. Background Technology

[0002] With the advancement of the "carbon neutrality" strategic goal, new energy equipment, represented by wind power and photovoltaic power generation, has been deployed and applied on a large scale, and the demand for supporting high-power power electronic conversion equipment is also growing. Cascaded power electronic converter topologies, due to their modular structure, ease of expansion, and low output voltage harmonic content, have become one of the mainstream solutions for achieving high-power power conversion and regulation, and are particularly widely used in reactive power compensation and power quality management in new energy power plants.

[0003] Currently, in single-phase converters based on cascaded power modules, the power modules used are mainly divided into two types: one is the traditional power module that only has power conversion function and does not integrate energy storage units (i.e., type A power module); the other is the power module that integrates energy storage units (such as batteries, supercapacitors, etc.) and can realize bidirectional energy flow and storage (i.e., type B power module). Type A power modules are usually used to construct reactive power compensation equipment such as static var generators (SVG), while type B power modules can be used to construct energy storage converters (PCS) with active power regulation capabilities.

[0004] However, existing control strategies are typically designed for a single type of power module. When the equipment consists entirely of Class A power modules, the core control function focuses on maintaining the stability of the DC-side capacitor voltage of each module and outputting the required reactive current. When the equipment consists entirely of Class B power modules, the control strategy needs to coordinate the output of both active power (energy storage charging and discharging) and reactive power. When upgrading existing traditional reactive power compensation equipment composed of Class A power modules to energy storage equipment with active power regulation capabilities, an economical and efficient solution is to add some Class B power modules to the existing Class A power module link, forming a hybrid topology of Class A and Class B power modules. This solution can reuse most of the original equipment hardware, significantly reducing upgrade and modification costs and floor space, while quickly giving the equipment active power throughput capabilities.

[0005] However, existing technologies lack effective control strategies to support the mixed operation of Class A and Class B power modules. The main technical challenge lies in: 1. Control objectives are incompatible: The control objective of Class A power modules is to stabilize their own capacitor voltage, which is essentially to maintain internal energy balance; while Class B power modules need to respond to the system's active power commands and control the charging and discharging of the energy storage unit, and their DC voltage will actively change with the charging and discharging state.

[0006] 2. Difficulty in energy coordination: In a hybrid system, Class B power modules need to handle all the active power demand of the system, and at the same time, they need to indirectly assist Class A power modules in maintaining capacitor voltage stability by regulating their output voltage. The control loops of the two types of modules are coupled to each other. If the control strategy of a single type of module is used, it is very easy to cause system oscillation or instability.

[0007] 3. Complex modulation wave synthesis: A new modulation wave generation mechanism needs to be designed to organically integrate information from the output of the voltage control loop of the Class A power module, the output of the current / power control loop of the Class B power module, and the grid voltage feedforward, so as to generate modulation waves to drive the two types of modules respectively, and ensure that the total output voltage after cascading meets the grid connection requirements. Summary of the Invention

[0008] The purpose of this invention is to provide a control strategy for energy storage devices that is suitable for hybrid power module connections, solve the coordination control problem in hybrid topologies of Class A and Class B power modules, and achieve a smooth, economical, and reliable upgrade from reactive power compensation devices to energy storage devices.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A control strategy for energy storage devices with hybrid power modules is provided. The energy storage device is a cascaded converter composed of cascaded Class A power modules and Class B power modules, wherein Class A power modules are power conversion modules without energy storage units, and Class B power modules are power conversion modules with energy storage units. Control strategies include: S1. Independently control the Class A power modules and the Class B power modules respectively; S2. A DC capacitor voltage control strategy is adopted for Class A power modules to maintain the DC capacitor voltage of Class A power modules within a preset target value range. S3. An active current control strategy is adopted for Class B power modules to control the total active power output of the energy storage device to the grid and to control the charging and discharging process of the energy storage unit inside the Class B power module. S4. Through power module current closed-loop control, coordinate the control of the total output current of the cascaded Class A power module and Class B power module, and control the output current of the cascaded converter by adjusting the output reactor voltage.

[0010] In S2, the DC capacitor voltage control strategy includes: Collect the DC capacitor voltage feedback values ​​of all Class A power modules and calculate their average value as the average DC capacitor voltage of Class A power modules; Collect the DC capacitor voltage feedback values ​​of all Class B power modules and calculate their average value as the average DC capacitor voltage of Class B power modules; Calculate the difference between the average DC capacitor voltage of Class A power modules and the average DC capacitor voltage of Class B power modules; The difference is input to a PI regulator for processing, and the output is used as the active voltage regulation component of the modulated wave of the Class B power module.

[0011] In S3, the active current control strategy includes: Based on the deviation between the active power reference value and the active power feedback value output by the energy storage device, the DC voltage control reference value of the Class B power module is generated after processing by the first PI regulator. Based on the deviation between the DC voltage control reference value and the DC voltage feedback value of the Class B power module, the active current reference amplitude of the energy storage device is generated after processing by the second PI regulator. Based on the active current reference amplitude, combined with the grid voltage and the feedforward control quantity introduced by the total modulation wave of the Class A power module, the modulation wave of the Class B power module is calculated and generated to complete the independent active current control of the Class B power module and the charging and discharging management of the energy storage unit.

[0012] In S4, the power module current closed-loop control includes: The active and reactive phases of the grid voltage are obtained through a phase-locked loop; Calculate the total output current reference value of the cascaded converter based on the reactive current reference value and the active current reference value of the cascaded converter. The total output current reference value is compared with the total output current feedback value of the energy storage device. The difference is processed by the PI regulator and combined with the instantaneous grid voltage value and the total modulation wave of the Class A power module as feedforward to generate the total modulation wave of the Class B power module, which is used to control the total output current of the cascaded converter.

[0013] The phase-locked loop adopts a second-order generalized integrator (SOGI) structure to extract the active phase Cosθ and reactive phase Sinθ from the grid voltage.

[0014] In the active current control of Class B power modules, the instantaneous value of the grid voltage and the total modulation wave of Class A power modules are introduced as feedforward quantities.

[0015] The control strategy also includes sequential control logic: Startup sequence control: Close the first-level circuit breaker → charge the DC capacitors of Class A and Class B power modules → close the second-level circuit breaker to bypass the charging resistor → start the energy storage unit control system of Class B power module → unlock all power devices of Class A and Class B power modules. Shutdown sequence control: Reduce the output current of the energy storage device to zero → lock out all power devices of Class A power modules and Class B power modules → lock out the energy storage unit control system of Class B power modules → disconnect the second-level circuit breaker and the first-level circuit breaker.

[0016] Both Class A and Class B power modules adopt the H-bridge full-bridge power module topology.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. The control strategy proposed in this invention enables existing cascaded reactive power compensation equipment (such as SVG) composed of pure Class A (without energy storage) power modules to be transformed into an energy storage system with active power regulation capabilities simply by adding a small number of Class B (with energy storage) power modules and upgrading the software. This maximizes the reuse of the original equipment (such as transformers, cabinets, most power modules and control systems), avoids the overall scrapping and replacement of the equipment, and significantly reduces the cost and cycle of upgrading from traditional reactive power compensation to energy storage. It has extremely high engineering application value and economic benefits. 2. By adopting a "classified independent control + top-level coordination" architecture, the problem of difficult coordinated operation between Class A and Class B power modules due to differences in control objectives and dynamic characteristics is successfully solved: For Class A power modules, DC capacitor voltage control based on output current orientation is adopted to ensure stable operation even when Class B power modules provide active power; for Class B power modules, an independent active current control loop integrating energy storage unit charging and discharging management is designed to ensure accurate response to system active power commands; through top-level current closed-loop control, the control outputs of the two types of modules are unified and synthesized to achieve accurate tracking and rapid response of the total system output current (including active and reactive components); this hierarchical decoupling and re-coordination control method ensures the overall stability and dynamic performance of the hybrid system. 3. In the control strategy, grid voltage feedforward and modulation wave feedforward of Class A power modules are introduced into the active current control loop and system total current control loop of Class B power modules; this can compensate for the impact of grid fluctuations and the operating status of Class A power modules on the output voltage demand of Class B power modules in real time, and significantly improve the dynamic response speed to power commands and grid disturbances. 4. A well-designed sequential control logic standardizes and streamlines the system's startup and shutdown processes. This sequential control logic ensures that during startup, the DC capacitor charges in an orderly manner, the energy storage unit is smoothly connected, and the power devices are unlocked sequentially. During shutdown, the output current smoothly drops to zero, and the power devices and energy storage system are locked in an orderly manner. This sequential control logic effectively avoids current and voltage surges caused by improper operation, protects the power devices and energy storage units, and improves the overall system's operational reliability and service life. 5. The control strategy is based on a modular full-bridge (H-bridge) topology, which does not depend on specific semiconductor devices or energy storage media (batteries, supercapacitors, etc.) and has good versatility. At the same time, it supports flexible configuration of the number of Class A power modules and Class B power modules. Users can adjust the ratio according to the actual reactive power compensation capacity and active energy storage needs. The system configuration is flexible, easy to expand, and can meet the customized needs of different application scenarios. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a Class A power module.

[0019] Figure 2 This is a schematic diagram of a Class B power module.

[0020] Figure 3 This is the startup sequence control logic diagram for a power module hybrid power electronic device.

[0021] Figure 4 This is a shutdown sequential control logic diagram for power module hybrid power electronic equipment.

[0022] Figure 5 This is a waveform diagram of the equipment prototype operating at full load.

[0023] Figure 6 This is a schematic diagram of the control strategy for hybrid power electronic devices with power modules. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0025] The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0026] Example 1 This invention aims to address the need to upgrade existing reactive power compensation equipment to energy storage equipment. It employs the addition of power modules with integrated energy storage units to enable active power regulation. The control strategy first adds an active current control component to the existing reactive current control, allowing the energy storage module to provide active current to the entire equipment, thus achieving active power regulation. The core element of this invention is the ability to independently control the energy storage unit to provide active current while maintaining reactive current regulation. This combined control strategy, achieved through the cascading of different power modules, is crucial. It achieves the goal of providing active current to the equipment using power modules with integrated energy storage units while ensuring stable operation of power modules without these units. This method can be widely applied to the upgrade and retrofitting of reactive power compensation equipment with cascaded full-bridge power modules; simply adding a power module with an integrated energy storage unit is sufficient to upgrade the equipment's functionality.

[0027] See Figure 1 , Figure 2 This paper presents a control strategy for energy storage devices using hybrid power modules. The strategy applies to single-phase cascaded power electronic converters composed of Class A power modules (without energy storage units) and Class B power modules (with energy storage units). The power electronic converter serves as the energy storage device, connecting to the grid and the load. A human-machine interface (HMI) is used to set system operating parameters, send start / stop commands, and display operating status. This system can be used in scenarios such as new energy power plants and industrial parks to achieve integrated "reactive power compensation + energy storage" functions, improving the power quality and operational stability of the grid. The core control module is a unified control strategy for the hybrid Class A and Class B power modules, primarily controlling the DC voltage and steady-state current of the power modules. Active current operation is achieved by adjusting the setpoint of the energy storage unit current control; stable control of the active power is achieved by separately controlling the DC voltage control links of the Class A and Class B power modules.

[0028] The control strategy consists of two parts: sequential control logic and closed-loop control logic. I. Sequential control logic of the experimental platform; In practical applications, once the energy storage unit of the Class B power module meets the operating conditions and the system is fault-free and in a ready state, a system startup command can be issued through the human-machine interface; the specific startup process is as follows: 1) When the main circuit breaker QF01 is closed, the system charges the DC-side capacitors of the Class A power module and the Class B power module through the pre-charging circuit; 2) After the DC capacitor voltage reaches a stable value, close the bypass circuit breaker QF02 to bypass the charging resistor; 3) Start the energy storage unit control system of the Class B power module to smoothly connect the energy storage unit to the DC bus; 4) Once the system is ready, unlock all H-bridge power devices of both Class A and Class B power modules sequentially, and the system will enter normal operation. See [link / reference]. Figure 3 .

[0029] The system shutdown procedure is as follows: 1) Issue a system shutdown command from the human-machine interface; 2) The control equipment gradually reduces the output current to zero; 3) Block out all H-bridge power devices in both Class A and Class B power modules; 4) Lockout of the energy storage unit control system for Class B power modules; 5) Disconnect circuit breakers QF02 and QF01 in sequence, see... Figure 4 .

[0030] II. Closed-loop control logic of the experimental platform; The closed-loop control structure of the entire system is mainly divided into four functional modules: the grid voltage phase-locked loop (PLL) module, the active power control module, the Class A power module modulation wave calculation module, and the Class B power module modulation wave calculation module. See the system control structure diagram below. Figure 6 .

[0031] (I) Mains Voltage PLL Module; This module is used to acquire the phase information of the power grid voltage in real time, providing a synchronization coordinate reference for other control components. In specific implementation: Collect instantaneous values ​​of grid voltage ; Will The input is fed into a phase-locked loop based on a second-order generalized integrator (SOGI) to calculate the active phase Cosθ and reactive phase Sinθ of the grid voltage. The active phase Cosθ and reactive phase Sinθ of the grid voltage are output to the active power control module, the Class A power module, and the Class B power module modulation wave calculation module for coordinate transformation and modulation wave synthesis.

[0032] The transfer function of the second-order generalized integrator (SOGI) is: (1); In formula (1): Represents the Laplace operator; This represents the fundamental angular frequency, expressed in rad / s.

[0033] This represents the damping coefficient.

[0034] (II) Active power control module; This module contains two sub-functions: DC voltage coordination control for Class A power modules and active power control for Class B power modules.

[0035] 1. DC voltage coordination control for Class A power modules; The capacitor voltage control of power modules without energy storage units differs from the capacitor voltage control of traditional H-bridge power modules. It needs to consider the active power control of power modules with energy storage units, as well as the active power control of the power grid. This control strategy adopts a Class A power module capacitor voltage control method based on output current orientation to ensure its stable operation.

[0036] To maintain stable DC-side capacitor voltage in Class A power modules, the following control method is adopted: 1) Collect the DC capacitor voltage of all Class A power modules. , ,......, Calculate its average value ; 2) Collect the DC capacitor voltage of all Class B power modules. , ,......, Calculate its average value ; 3) Calculate the average voltage deviation = - ; 4) The input is a PI regulator, and the output is the active voltage regulation component of the modulated wave of the Class B power module. It is used to coordinate the energy balance between the two types of modules and to help the Class A power module maintain DC voltage.

[0037] The transfer function of the PI controller: ; in: Indicates the proportionality coefficient; Represents the integral coefficient, in units of s. -1 ; 2. Active power control for Class B power modules; For active current control of power modules with energy storage units, the main considerations are the charging and discharging control of the energy storage units and the active power command of the system. The active current is mainly controlled independently for the energy storage unit. The active current output is achieved by introducing the feedforward value of the grid voltage and the sum of the voltages of the cascaded Class A power modules.

[0038] To achieve accurate output of system active power and management of energy storage unit charging and discharging, the following control method is adopted: 1) The system outputs active power feedback values. , and active power reference value The power deviation is obtained through comparison: = - ; 2) Power deviation After processing by the PI regulator, the DC voltage of the Class B power module is controlled. ; 3) Average DC voltage feedback with Class B power modules The deviation is compared and processed by another PI regulator to generate a reference amplitude for the total active current of the system. .

[0039] (III) Class A Power Module Modulation Wave Calculation Module; This module is used to generate the modulation wave for Class A power modules. The specific steps are as follows: 1. Receive active phase Cosθ and reactive phase Sinθ from the PLL and from the active power control module. ; 2. The modulation wave of a Class A power module is used to output reactive current and maintain its own DC voltage. Its fundamental reference value is... From reactive current reference and voltage coordination components Joint decision; 3. Combine with current closed-loop feedback After compensation, the final modulated wave is generated. .

[0040] The formula for calculating the modulated wave can be expressed as: ; in: This represents the fundamental reference amplitude of the modulation wave, in units of V; This represents the modulation function related to the phase θ, which is usually a combination of Cosθ or Sinθ.

[0041] Indicates current feedback The closed-loop compensation term is expressed in V.

[0042] (iv) Class B power module modulation wave calculation module; This module is used to generate the total modulation wave for the Class B power module. It consists of two parts: current closed-loop control and voltage feedforward.

[0043] 1. Current closed-loop control: according to With reactive current reference Composite total current reference vector ; Total output current feedback of the acquisition system Calculate the current deviation ; Will The output current is adjusted via a closed-loop regulation after processing by a PI controller.

[0044] 2. Voltage feedforward calculation: To improve dynamic response, grid voltage feedforward and Class A power module modulated wave feedforward are introduced: ; This represents the instantaneous value of the grid voltage, in units of V; This represents the superposition value of the modulated waves from all Class A power modules, expressed in V.

[0045] 3. Modulated wave synthesis; The final total modulation waveform of the Class B power module is: ; in: This indicates the output of the current closed-loop PI regulator, in volts (V). This represents the voltage feedforward quantity, with the unit being V; Other compensation terms (such as harmonic compensation, damping terms, etc.) are represented in V. Typical waveforms during system unlocking operation are shown below. Figure 5 .

[0046] 3. Current closed-loop control of the power module; The closed-loop current control of the entire cascaded power module equipment is mainly achieved by adjusting the total output of the cascaded H-bridge power modules of different types A and B, while using grid voltage feedback to control the voltage of the output reactor, thereby controlling the total output current.

[0047] The control strategy employs different control strategies for different types of power modules. After summarizing, a new control strategy for current control is integrated into the system, enabling the equipment to achieve stable operation after cascading different types of power modules.

[0048] Example 2 A power module hybrid energy storage device is provided, the structure of which includes: 1. Multiple Class A power modules, using an H-bridge topology, without energy storage units; 2. At least one Class B power module, using an H-bridge topology, integrates an energy storage unit (such as a battery or supercapacitor), with a DC capacitor connected to the energy storage unit, typically a battery or supercapacitor; 3. System controller, used to execute the control strategy of Example 1; 4. Power grid interface, output reactor and human-machine interface.

[0049] This equipment is suitable for upgrading existing reactive power compensation devices (such as SVG) composed of pure Class A power modules into energy storage systems with active power regulation capabilities. It only requires the addition of Class B power modules and updating of the control program, without replacing the main equipment. The transformation cost is low and the cycle is short.

[0050] The control strategy proposed in this invention enables existing cascaded reactive power compensation equipment (such as SVG) composed of pure Class A (without energy storage) power modules to be transformed into an energy storage system with active power regulation capabilities simply by adding a small number of Class B (with energy storage) power modules and upgrading the software. This maximizes the reuse of the original equipment (such as transformers, cabinets, most power modules, and control systems), avoids the complete scrapping and replacement of the equipment, and significantly reduces the cost and time required to upgrade from traditional reactive power compensation to energy storage. It has extremely high engineering application value and economic benefits. Through a "classified independent control + top-level collaboration" architecture, it successfully solves the problem of Class A power... The problem of difficult coordinated operation between Class A and Class B power modules due to differences in control objectives and dynamic characteristics is addressed as follows: For Class A power modules, DC capacitor voltage control based on output current orientation is adopted to ensure stable operation even when Class B power modules provide active power; for Class B power modules, an independent active current control loop integrating energy storage unit charging and discharging management is designed to ensure accurate response to system active power commands; through top-level current closed-loop control, the control outputs of the two types of modules are unified and synthesized to achieve accurate tracking and rapid response of the total system output current (including active and reactive components); this hierarchical decoupling and re-coordination control method ensures the hybrid system... The overall stability and dynamic performance are improved. In the control strategy, grid voltage feedforward and Class A power module modulation wave feedforward are introduced into the active current control loop and system total current control loop of the Class B power module. This enables real-time compensation for grid fluctuations and the impact of the Class A power module's operating state on the output voltage demand of the Class B power module, significantly improving the dynamic response speed to power commands and grid disturbances. A well-designed sequential control logic standardizes and streamlines the system's startup and shutdown processes. The sequential control logic ensures orderly charging of the DC capacitor, smooth connection of the energy storage unit, and sequential unlocking of power devices during startup; and a smooth reduction in output current during shutdown. The system features a zero-to-zero, orderly interlocking mechanism for power devices and energy storage systems. This sequential control logic effectively avoids current and voltage surges caused by improper operation, protecting power devices and energy storage units, and improving the overall system's operational reliability and lifespan. The control strategy is based on a modular full-bridge (H-bridge) topology, independent of specific semiconductor devices or energy storage media (batteries, supercapacitors, etc.), and has good versatility. Simultaneously, it supports flexible configuration of the number of Class A and Class B power modules, allowing users to adjust the ratio according to actual reactive power compensation capacity and active energy storage needs. The system configuration is flexible, easily expandable, and can meet the customized needs of different application scenarios.

Claims

1. A control strategy for energy storage devices suitable for hybrid power module connections, characterized in that, The energy storage device is a cascaded converter consisting of cascaded Class A power modules and Class B power modules, where Class A power modules are power conversion modules without energy storage units, and Class B power modules are power conversion modules with energy storage units. Control strategies include: S1. Independently control the Class A power modules and the Class B power modules respectively; S2. A DC capacitor voltage control strategy is adopted for Class A power modules to maintain the DC capacitor voltage of Class A power modules within a preset target value range. S3. An active current control strategy is adopted for Class B power modules to control the total active power output of the energy storage device to the grid and to control the charging and discharging process of the energy storage unit inside the Class B power module. S4. Through closed-loop control of the power module current, the total output current of the cascaded A-type power module and B-type power module is coordinated and controlled, and the output current of the cascaded converter is controlled by adjusting the voltage of the output reactor.

2. The control strategy for energy storage devices suitable for hybrid power module connection according to claim 1, characterized in that, In S2, the DC capacitor voltage control strategy includes: Collect the DC capacitor voltage feedback values ​​of all Class A power modules and calculate their average value as the average DC capacitor voltage of Class A power modules; Collect the DC capacitor voltage feedback values ​​of all Class B power modules and calculate their average value as the average DC capacitor voltage of Class B power modules; Calculate the difference between the average DC capacitor voltage of Class A power modules and the average DC capacitor voltage of Class B power modules; The difference is input to a PI regulator for processing, and the output is used as the active voltage regulation component of the modulated wave of the Class B power module.

3. The control strategy for energy storage devices suitable for hybrid power module connection according to claim 1, characterized in that, In S3, the active current control strategy includes: Based on the deviation between the active power reference value and the active power feedback value output by the energy storage device, the DC voltage control reference value of the Class B power module is generated after processing by the first PI regulator. Based on the deviation between the DC voltage control reference value and the DC voltage feedback value of the Class B power module, the active current reference amplitude of the energy storage device is generated after processing by the second PI regulator. Based on the active current reference amplitude, combined with the grid voltage and the feedforward control quantity introduced by the total modulation wave of the Class A power module, the modulation wave of the Class B power module is calculated and generated to complete the independent active current control of the Class B power module and the charging and discharging management of the energy storage unit.

4. The control strategy for energy storage devices suitable for hybrid power module connection according to claim 1, characterized in that, In S4, the power module current closed-loop control includes: The active and reactive phases of the grid voltage are obtained through a phase-locked loop; Calculate the total output current reference value of the cascaded converter based on the reactive current reference value and the active current reference value of the cascaded converter. The total output current reference value is compared with the total output current feedback value of the energy storage device. The difference is processed by the PI regulator and combined with the instantaneous grid voltage value and the total modulation wave of the Class A power module as feedforward to generate the total modulation wave of the Class B power module, which is used to control the total output current of the cascaded converter.

5. A control strategy for energy storage devices suitable for hybrid power module connections according to claim 4, characterized in that, The phase-locked loop adopts a second-order generalized integrator (SOGI) structure to extract the active phase Cosθ and reactive phase Sinθ from the grid voltage.

6. A control strategy for energy storage devices suitable for hybrid power module connections according to claim 1, characterized in that, In the active current control of Class B power modules, the instantaneous value of the grid voltage and the total modulation wave of Class A power modules are introduced as feedforward quantities.

7. A control strategy for energy storage devices suitable for hybrid power module connections according to claim 1, characterized in that, The control strategy also includes sequential control logic: Startup sequence control: Close the first-level circuit breaker → charge the DC capacitors of Class A and Class B power modules → close the second-level circuit breaker to bypass the charging resistor → start the energy storage unit control system of Class B power module → unlock all power devices of Class A and Class B power modules. Shutdown sequence control: Reduce the output current of the energy storage device to zero → lock out all power devices of Class A power modules and Class B power modules → lock out the energy storage unit control system of Class B power modules → disconnect the second-level circuit breaker and the first-level circuit breaker.

8. A control strategy for energy storage devices suitable for hybrid power module connections according to claim 1, characterized in that, Both Class A and Class B power modules adopt the H-bridge full-bridge power module topology.

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