Modular multilevel converter energy storage integrated device and energy interaction method thereof

Abstract

The invention provides a modular multilevel converter (MMC) energy storage integrated device and an energy interaction method thereof. The device comprises an MMC and an energy storage branch, and the energy storage branch is connected in parallel to an upper bridge arm inductor and a lower bridge arm inductor of each phase of the MMC, and is used for storing the energy of the MMC or releasing the stored energy to the MMC by taking the bridge arm inductors as media. According to the method, energy exchange between the MMC and the energy storage branch can be realized only by connecting the energy storage branch to the two ends of the MMC bridge arm inductor in parallel, the engineering implementation is simple, the transformation cost is extremely low, and the method is suitable for carrying out energy storage upgrading on the MMC transformer substation which is put into operation. The energy storage branch is physically isolated from the MMC main circuit, and can be installed in an independent cabin with special fire-fighting equipment. The problem that faults such as battery thermal runaway directly affect expensive main current conversion equipment is thoroughly avoided, and the safety and reliability of the whole energy storage integrated system are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of new energy grid connection technology, specifically relating to a modular multilevel converter energy storage integration device and its energy interaction method. Background Technology

[0002] As the proportion of renewable energy in the power grid continues to increase, grid operation faces new challenges. Large-scale energy storage systems (ESS) can provide ancillary services such as frequency regulation, power smoothing, and energy buffering, effectively enhancing grid stability and the ability to absorb renewable energy.

[0003] Currently, the main problems with energy storage system integration methods are as follows: Traditional full-power integration schemes require high-power converters that are perfectly matched to the system capacity, resulting in high system costs and large size; while directly embedding energy storage units into modular multilevel converter (MMC) submodules improves integration, it also presents problems such as poor safety, low reliability, and difficulty in modification. In particular, placing energy storage components prone to thermal runaway, such as lithium batteries, within the valve hall of the MMC poses serious safety hazards. In view of these problems, there is an urgent need to propose an energy storage solution applicable to modular multilevel converters. Summary of the Invention

[0004] To address the shortcomings of existing modular multilevel converter energy storage technologies, such as low efficiency, high cost, poor safety, low reliability, and difficulty in retrofitting, this invention proposes a modular multilevel converter energy storage integrated device, comprising: a modular multilevel converter (MMC) and an energy storage branch. The energy storage branch is connected in parallel to the upper and lower bridge arm inductors of each phase of the MMC, and is used to store the energy of the MMC or release the stored energy to the MMC through the bridge arm inductors.

[0005] Preferably, the energy storage branch includes a connected DC / AC converter and an energy storage unit.

[0006] Preferably, the energy storage unit includes a battery or a supercapacitor.

[0007] Based on the same inventive concept, this invention also provides an energy interaction method for a modular multilevel converter energy storage integrated device, comprising: Obtain the electrical parameters of the MMC and energy storage branch in the modular multilevel converter energy storage integrated device; The electrical parameters are input into a pre-built formula for calculating the current setpoint, and the current setpoints for each phase arm of the MMC and the current setpoints for the energy storage branch converter are obtained. Energy interaction is performed between the MMC and the energy storage branch based on the given values ​​of the current in each phase arm of the MMC and the given values ​​of the current in the converter of the energy storage branch. The device described above is a modular multilevel converter energy storage integrated device.

[0008] Preferably, the electrical parameters include: MMC AC side power reference value, MMC DC side power reference value, grid fundamental frequency, number of injected high-frequency harmonics, MMC bridge arm series inductance value, phase angle of each phase output AC current of MMC and phase angle of energy storage branch current.

[0009] Preferably, the step of inputting the electrical parameters into a pre-built current setpoint calculation formula to obtain the current setpoints for each phase arm of the MMC and the current setpoints for the energy storage branch converter connection includes: Based on the AC-side power reference value and DC-side power reference value of the MMC, calculate the DC circulating current setpoint, the fundamental AC circulating current amplitude setpoint of each phase of the MMC, and the reference power of the energy storage branch. The given DC circulating current value, the given amplitude of the fundamental AC circulating current of each phase of the MMC, the reference power of the energy storage branch, the fundamental angular frequency of the power grid, the order of the injected high-frequency harmonics, the series inductance value of the MMC arm, the phase angle of the output AC current of each phase of the MMC, and the phase angle of the current of the energy storage branch are input into the formula for calculating the given current value to obtain the given current value of each phase arm of the MMC and the given current value of the converter connected to the energy storage branch.

[0010] Preferably, the formula for calculating the current setpoint is expressed as follows:

[0011]

[0012]

[0013] In the formula, P es For reference power of energy storage branch, For MMC x Phase arm inductor current amplitude, For energy storage branch converter x Phase arm current amplitude, ω The fundamental angular frequency of the power grid. t For time variables, h The order of the injected high-frequency harmonics. L s This refers to the series inductance value of the MMC bridge arm. For energy storage branch converter x Phase bridge arm current setpoint, θ x For MMC x The phase angle of the output AC current. Ψ e The phase angle of the energy storage branch current. For MMC x Phase bridge arm current setpoint, The given value for the DC circulating current. For MMC x The given value of the amplitude of the phase fundamental wave AC circulation.

[0014] Preferably, the energy interaction between the MMC and the energy storage branch based on the given values ​​of the current in each phase arm of the MMC and the given values ​​of the current connected to the energy storage branch converter includes: Based on the given values ​​of the current in each phase arm of the MMC, an MMC trigger signal is generated through the current closed-loop control of the MMC. Based on the given value of the input current of the energy storage branch converter, the current closed-loop control of the DC / AC converter in the energy storage branch generates the trigger signal of the energy storage branch converter. Based on the MMC trigger signal and the energy storage branch converter trigger signal, a high-frequency circulating current is excited on the bridge arm inductor of the MMC to perform energy interaction between the MMC and the energy storage branch.

[0015] Based on the same inventive concept, the present invention also provides an energy interaction system for a modular multilevel converter energy storage integrated device, comprising: an acquisition module, a calculation module, and an input module; The acquisition module is used to acquire the electrical parameters of the MMC and energy storage branch in the modular multilevel converter energy storage integrated device; The calculation module is used to input the electrical parameters into a pre-built formula for calculating the current setpoint, so as to obtain the current setpoint of each phase arm of the MMC and the current setpoint of the energy storage branch converter. The input module is used to input the given values ​​of the current of each phase arm of the MMC and the given values ​​of the current of the energy storage branch converter into the device to perform energy interaction between the MMC and the energy storage branch. The device is a modular multilevel converter energy storage integrated device as described above.

[0016] Based on the same inventive concept, the present invention also provides an electronic device, comprising: at least one processor and a memory; wherein the memory and the processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, the energy interaction method of the modular multilevel converter energy storage integrated device described above is implemented.

[0017] Based on the same inventive concept, the present invention also provides a readable storage medium having an executable program stored thereon, wherein when the executable program is executed, it implements the energy interaction method of the modular multilevel converter energy storage integrated device described above.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a modular multilevel converter (MMC) energy storage integration device and its energy exchange method. The device includes a MMC and an energy storage branch. The energy storage branch is connected in parallel to the upper and lower arm inductors of each phase of the MMC, and is used to store energy in the MMC or release stored energy to the MMC through the arm inductors. This invention only requires connecting the energy storage branch in parallel to both ends of the MMC arm inductors to achieve energy exchange between the MMC and the energy storage branch. The engineering implementation is simple, the transformation cost is extremely low, and it is particularly suitable for upgrading existing MMC substations to energy storage. The energy storage branch is physically isolated from the MMC main circuit and can be installed in a separate cabin with dedicated fire protection facilities. This completely avoids the problem of faults such as battery thermal runaway directly affecting expensive main converter equipment, greatly improving the safety and reliability of the entire energy storage integration system. Attached Figure Description

[0019] Figure 1 A structural diagram of a modular multilevel converter energy storage integrated device provided by the present invention; Figure 2 This is a flowchart illustrating the energy interaction method of a modular multilevel converter energy storage integrated device according to the present invention. Figure 3 This is an equivalent circuit diagram of a modular multilevel converter energy storage integrated device according to the present invention; Figure 4 This is a control flowchart of a modular multilevel converter energy storage integrated device according to the present invention; Figure 5 This is a schematic diagram of an electronic device structure provided by the present invention. Detailed Implementation

[0020] To better understand the present invention, the following description, in conjunction with the accompanying drawings and embodiments, will further illustrate the content of the present invention.

[0021] Example 1: A modular multilevel converter energy storage integrated device, the structure of which is shown in the figure below. Figure 1 As shown, it includes: a modular multilevel converter (MMC) and an energy storage branch; The energy storage branch is connected in parallel to the upper and lower bridge arm inductors of each phase of the MMC, and is used to store the energy of the MMC or release the stored energy to the MMC through the bridge arm inductors.

[0022] The MMC consists of three-phase bridge arms, each of which includes several series-connected sub-modules (SM1-SMn) and two bridge arm inductors. L s By connecting an energy storage branch containing a partial power converter (such as a DC / AC converter) and an energy storage unit (such as a battery or supercapacitor) in parallel across the upper and lower bridge arm inductors of each phase of the MMC, and by injecting high-order harmonic components into the converter circulating current, the energy storage inductors in the bridge arm inductors are improved. L s Harmonic voltages are generated, thereby enabling energy exchange between the energy storage branch and the MMC. The modular multilevel converter energy storage integrated device proposed in this invention has the following advantages compared to previous solutions: The converter in the energy storage branch can support a portion of the power as needed, only needing to handle a small portion of the total power, without needing to support the entire system rated voltage. This reduces the capacity, size, and cost of the power devices in the energy storage branch converter, significantly reducing the complexity of the retrofit and making large-scale energy storage integration more economically feasible. It only requires parallel connection of the existing busbars at both ends of the bridge arm inductor, making the project simple to implement and the transformation cost extremely low. It can achieve non-disruptive transformation of existing converter substations without changing the original structure, and is particularly suitable for energy storage upgrade of MMC substations that have already been put into operation. The energy storage units (especially lithium batteries) are physically isolated from the MMC main circuit and can be installed in a separate compartment equipped with dedicated fire suppression systems. This completely avoids battery thermal runaway and other malfunctions directly impacting the expensive main converter equipment, greatly improving the safety and reliability of the entire system.

[0023] Example 2: Based on the same inventive concept, this invention also provides an energy interaction method for a modular multilevel converter energy storage integrated device, the flowchart of which is shown below. Figure 2 As shown, it includes: Step 1: Obtain the electrical parameters of the MMC and energy storage branch in the modular multilevel converter energy storage integrated device; Step 2: Input the electrical parameters into the pre-built current setpoint calculation formula to obtain the current setpoint of each phase arm of the MMC and the current setpoint of the energy storage branch converter. Step 3: Based on the given values ​​of the current of each phase arm of the MMC and the given values ​​of the current connected to the energy storage branch converter, perform energy interaction between the MMC and the energy storage branch. The device described herein is a modular multilevel converter energy storage integrated device as described in Example 1.

[0024] This embodiment first analyzes the working principle of the above-mentioned device, and its topology can be equivalent to as follows: Figure 3 The circuit diagram shown.

[0025] In the picture υ dc This is the DC port voltage. x Indicates one of the three phases (which can be chosen) a , b , c ), i xs for x Phase upper arm current, υ xu for x The equivalent controlled voltage source of the upper bridge arm, υ xl for x The equivalent controlled voltage source of the lower bridge arm. υ xe for x The energy storage branch is connected to the controlled voltage source of the MMC. υ x for x Phase grid voltage, υ cm This refers to the voltage at the center point of the three-phase AC to DC bus. i xu for x Phase upper arm bridge arm inductor current, i xl for x Phase lower arm bridge arm inductor current, i xe for x Phase energy storage branch current. L s This refers to the series inductance value of the MMC bridge arm. L 0 represents the equivalent inductance when connected to the AC power grid. L e For the energy storage branch, an inductor is connected, and the corresponding inductor resistances are respectively... r s , r 0、 r e Define the AC output current. i x = i xu - i xl circulation i xz =( i xu + i xl ) / 2, according to the circuit principle above, the AC output current and circulating current are determined by the following two formulas: (1) (2) As can be seen from formulas 1 and 2, by controlling the controlled voltage of each phase upper and lower arm of the MMC... υ xu and υ xl It can control the AC output current i x and circulation i xz .

[0026] The current in the energy storage branch is determined by the following formula, and can be adjusted... υ xe To control the current connected to the energy storage branch i xe It couples with the high-frequency voltage generated by the high-frequency circulating current of the bridge arm inductor, thereby realizing energy interaction between the energy storage branch and the MMC.

[0027] (3) The above analysis shows that, to achieve an energy interaction method for a modular multilevel converter energy storage integrated device, the key is to obtain the current setpoints for the MMC and the energy storage branch. By adjusting the controlled voltage source, the current tracks the setpoints, thus achieving the energy interaction effect. The control flow of a modular multilevel converter energy storage integrated device can be derived from the above analysis, as follows: Figure 4 As shown in the figure, the specific details of steps 2 and 3 are included.

[0028] Step 2 specifically includes: Step 2-1: Based on the MMC AC side power reference value and MMC DC side power reference value obtained in Step 1, calculate the DC circulating current setpoint, the fundamental AC circulating current amplitude setpoint of each phase of the MMC, and the energy storage branch reference power; Using the known MMC AC-side power reference value Pac_ref and MMC DC-side power reference value Pdc_ref, the reference power Pes of the energy storage branch can be obtained as Pac_ref - Pdc_ref. Based on Pac_ref and Pdc_ref, the DC circulating current setpoint and the fundamental AC circulating current amplitude setpoint of each phase of the MMC can be calculated according to the MMC power balance and circulating current characteristic derivation formula.

[0029] Assuming the phase difference between the energy storage branch current and the high-frequency circulating current in the bridge arm is equal to 90 degrees, after adding harmonic circulating current to the MMC, in order to minimize the current stress added to the original converter, the amplitudes of the converter bridge arm inductor current and the energy storage branch connection current should satisfy the following relationship: (4) In the formula, For MMC x Phase arm inductor current amplitude, For energy storage branch converter x Phase arm current amplitude, ω The fundamental angular frequency of the power grid. h The order of the injected high-frequency harmonics. h The recommended frequency is 7 times, which is 350Hz.

[0030] The given value of the energy storage branch current satisfies the following relationship: (5) In the formula, For energy storage branch converter x Phase bridge arm current setpoint, θ x For MMC x The phase angle of the output AC current. t For time variables, Ψ e The phase angle of the energy storage branch current.

[0031] The given value of the current in each phase arm of the MMC satisfies the following relationship: (6) In the formula, For MMC x Phase bridge arm current setpoint, The given value for the DC circulating current. For MMC x The given value of the amplitude of the fundamental wave AC circulation; , can be calculated from Pac_ref and Pdc_ref based on the MMC power balance and circulating current characteristics derivation formula; , is the given value for the high-frequency circulating current.

[0032] Formula 4-6 is the formula for calculating the current setpoint.

[0033] Step 2-2: Input the DC circulating current setpoint, the fundamental AC circulating current amplitude setpoint of each phase of MMC, and the reference power of the energy storage branch obtained in Step 2-1, as well as the grid fundamental angular frequency, the order of the injected high-frequency harmonics, the series inductance value of the MMC bridge arm, the phase angle of the output AC current of each phase of MMC, and the phase angle of the current of the energy storage branch obtained in Step 1, into the current setpoint calculation formula to obtain the current setpoint of each phase bridge arm of MMC and the current setpoint of the converter in the energy storage branch.

[0034] Step 3 specifically includes: After obtaining the setpoint values ​​of the bridge arm currents of the MMC and the input current of the energy storage branch converter, corresponding trigger control signals are generated through the current closed-loop control of each converter. This excites a high-frequency circulating current in the bridge arm inductors of the MMC to facilitate energy exchange between the MMC and the energy storage branch. This control process is similar to that of typical MMC and DC / AC converter control methods.

[0035] This method calculates the given values ​​of the bridge arm currents of each phase of the MMC and the given values ​​of the input current of the energy storage branch converter, and then controls the MMC to generate a high-frequency circulating current on the bridge arm inductor. This current can be used as a "carrier" to transfer energy between the energy storage branch and the MMC main circuit. The solution is simple and fast.

[0036] Example 3: Based on the same inventive concept, the present invention also provides an energy interaction system for a modular multilevel converter energy storage integrated device, characterized in that it includes: an acquisition module, a calculation module, and an input module; The acquisition module is used to acquire the electrical parameters of the MMC and energy storage branch in the modular multilevel converter energy storage integrated device; The calculation module is used to input the electrical parameters into a pre-built formula for calculating the current setpoint, so as to obtain the current setpoint of each phase arm of the MMC and the current setpoint of the energy storage branch converter. The input module is used to input the given values ​​of the current of each phase arm of the MMC and the given values ​​of the current of the energy storage branch converter into the device to perform energy interaction between the MMC and the energy storage branch. The device described herein is a modular multilevel converter energy storage integrated device as described in Example 1.

[0037] The electrical parameters include: MMC AC side power reference value, MMC DC side power reference value, grid fundamental frequency, number of injected high-frequency harmonics, MMC bridge arm series inductance value, phase angle of each phase output AC current of MMC and phase angle of energy storage branch current.

[0038] The computing module is specifically used for: Based on the AC-side power reference value and DC-side power reference value of the MMC, calculate the DC circulating current setpoint, the fundamental AC circulating current amplitude setpoint of each phase of the MMC, and the reference power of the energy storage branch. The given DC circulating current value, the given amplitude of the fundamental AC circulating current of each phase of the MMC, the reference power of the energy storage branch, the fundamental angular frequency of the power grid, the order of the injected high-frequency harmonics, the series inductance value of the MMC arm, the phase angle of the output AC current of each phase of the MMC, and the phase angle of the current of the energy storage branch are input into the formula for calculating the given current value to obtain the given current value of each phase arm of the MMC and the given current value of the converter connected to the energy storage branch.

[0039] The formula for calculating the current setpoint is expressed as follows:

[0040]

[0041]

[0042] In the formula, P es For reference power of energy storage branch, For MMC x Phase arm inductor current amplitude, For energy storage branch converter x Phase arm current amplitude, ω The fundamental angular frequency of the power grid. t For time variables, h The order of the injected high-frequency harmonics. L s This refers to the series inductance value of the MMC bridge arm. For energy storage branch converter x Phase bridge arm current setpoint, θ x For MMC x The phase angle of the output AC current. Ψ e The phase angle of the energy storage branch current. For MMC x Phase bridge arm current setpoint, The given value for the DC circulating current. For MMC x The given value of the amplitude of the phase fundamental wave AC circulation.

[0043] This system calculates the setpoint current of each phase arm of the MMC and the setpoint current of the converter in the energy storage branch, and then controls the MMC to generate a high-frequency circulating current in the arm inductor. This current can be used as a "carrier" to transfer energy between the energy storage branch and the MMC main circuit. The solution is simple and fast.

[0044] Example 4: like Figure 5As shown, the present invention also provides an electronic device, which may be a computer device, a microcontroller device, a smart mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, processor, and transceiver component are connected via a bus; the memory can be used to store executable programs, and an exemplary executable program may include instructions; the processor is used to execute the instructions stored in the memory. The memory can also be used to store data, which can be accessed and / or modified when instructions are executed.

[0045] The processor may be a Central Processing Unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and it is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the storage medium to realize the corresponding method flow or corresponding function, so as to realize the steps of the energy interaction method of a modular multilevel converter energy storage integrated device in the above embodiments.

[0046] This method calculates the given values ​​of the bridge arm currents of each phase of the MMC and the given values ​​of the input current of the energy storage branch converter, and then controls the MMC to generate a high-frequency circulating current on the bridge arm inductor. This current can be used as a "carrier" to transfer energy between the energy storage branch and the MMC main circuit. The solution is simple and fast.

[0047] Example 5: Based on the same inventive concept, this invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory). This readable storage medium is a memory device within an electronic device used to store programs and data. It is understood that the storage medium here can include both built-in storage media within the electronic device and extended storage media supported by the electronic device. The storage medium provides storage space, which stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more executable programs (including program code). It should be noted that the storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. Loading and executing one or more instructions stored in the storage medium by the processor can implement the steps of the energy interaction method of a modular multilevel converter energy storage integrated device in the above embodiments.

[0048] This method calculates the given values ​​of the bridge arm currents of each phase of the MMC and the given values ​​of the input current of the energy storage branch converter, and then controls the MMC to generate a high-frequency circulating current on the bridge arm inductor. This current can be used as a "carrier" to transfer energy between the energy storage branch and the MMC main circuit. The solution is simple and fast.

[0049] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0050] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0051] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0052] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0053] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A modular multilevel converter energy storage integrated device, characterized in that, include: Modular multilevel converter (MMC) and energy storage branch; The energy storage branch is connected in parallel to the upper and lower bridge arm inductors of each phase of the MMC, and is used to store the energy of the MMC or release the stored energy to the MMC through the bridge arm inductors.

2. The apparatus as claimed in claim 1, characterized in that, The energy storage branch includes a connected DC / AC converter and an energy storage unit.

3. The apparatus as described in claim 2, characterized in that, The energy storage unit includes: a battery or a supercapacitor.

4. An energy interaction method for a modular multilevel converter energy storage integrated device, characterized in that, include: Obtain the electrical parameters of the MMC and energy storage branch in the modular multilevel converter energy storage integrated device; The electrical parameters are input into a pre-built formula for calculating the current setpoint, and the current setpoints for each phase arm of the MMC and the current setpoints for the energy storage branch converter are obtained. Energy interaction is performed between the MMC and the energy storage branch based on the given values ​​of the current in each phase arm of the MMC and the given values ​​of the current in the converter of the energy storage branch. The device is a modular multilevel converter energy storage integrated device as described in any one of claims 1-3.

5. The method as described in claim 4, characterized in that, The electrical parameters include: MMC AC side power reference value, MMC DC side power reference value, grid fundamental frequency, number of injected high-frequency harmonics, MMC bridge arm series inductance value, phase angle of each phase output AC current of MMC and phase angle of energy storage branch current.

6. The method as described in claim 5, characterized in that, The step of inputting the electrical parameters into a pre-built current setpoint calculation formula to obtain the current setpoints for each phase arm of the MMC and the current setpoints for the energy storage branch converter connection includes: Based on the AC-side power reference value and DC-side power reference value of the MMC, calculate the DC circulating current setpoint, the fundamental AC circulating current amplitude setpoint of each phase of the MMC, and the reference power of the energy storage branch. The given DC circulating current value, the given amplitude of the fundamental AC circulating current of each phase of the MMC, the reference power of the energy storage branch, the fundamental angular frequency of the power grid, the order of the injected high-frequency harmonics, the series inductance value of the MMC arm, the phase angle of the output AC current of each phase of the MMC, and the phase angle of the current of the energy storage branch are input into the formula for calculating the given current value to obtain the given current value of each phase arm of the MMC and the given current value of the converter connected to the energy storage branch.

7. The method as described in claim 6, characterized in that, The formula for calculating the current setpoint is expressed as follows: In the formula, P es For reference power of energy storage branch, For MMC x Phase arm inductor current amplitude, For energy storage branch converter x Phase arm current amplitude, ω The fundamental angular frequency of the power grid. t For time variables, h The order of the injected high-frequency harmonics. L s This refers to the series inductance value of the MMC bridge arm. For energy storage branch converter x Phase bridge arm current setpoint, θ x For MMC x The phase angle of the output AC current. Ψ e The phase angle of the energy storage branch current. For MMC x Phase bridge arm current setpoint, The given value for the DC circulating current. For MMC x The given value of the amplitude of the phase fundamental wave AC circulation.

8. The method as described in claim 4, characterized in that, The energy interaction between the MMC and the energy storage branch based on the given values ​​of the current in each phase arm of the MMC and the given values ​​of the current connected to the energy storage branch converter includes: Based on the given values ​​of the current in each phase arm of the MMC, an MMC trigger signal is generated through the current closed-loop control of the MMC. Based on the given value of the input current of the energy storage branch converter, the current closed-loop control of the DC / AC converter in the energy storage branch generates the trigger signal of the energy storage branch converter. Based on the MMC trigger signal and the energy storage branch converter trigger signal, a high-frequency circulating current is excited on the bridge arm inductor of the MMC to perform energy interaction between the MMC and the energy storage branch.

9. An energy interaction system for a modular multilevel converter energy storage integrated device, characterized in that, include: The module consists of an acquisition module, a calculation module, and an input module. The acquisition module is used to acquire the electrical parameters of the MMC and energy storage branch in the modular multilevel converter energy storage integrated device; The calculation module is used to input the electrical parameters into a pre-built formula for calculating the current setpoint, so as to obtain the current setpoint of each phase arm of the MMC and the current setpoint of the energy storage branch converter. The input module is used to input the given values ​​of the current of each phase arm of the MMC and the given values ​​of the current of the energy storage branch converter into the device to perform energy interaction between the MMC and the energy storage branch. The device is a modular multilevel converter energy storage integrated device as described in any one of claims 1-3.

10. An electronic device, characterized in that, include: At least one processor and memory; The memory and processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, an energy interaction method for a modular multilevel converter energy storage integrated device as described in any one of claims 4 to 8 is implemented.

11. A readable storage medium, characterized in that, It contains an execution program, which, when executed, implements an energy interaction method for a modular multilevel converter energy storage integrated device as described in any one of claims 4 to 8.

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