Multi-unit energy storage converter external characteristic remodeling method and system based on network construction technology

Abstract

The invention discloses a multi-unit energy storage converter external characteristic remodeling method and system based on a network construction technology. The multi-unit energy storage converter comprises a main converter unit and at least one sub-converter unit. Collecting active power and reactive power of a main current transformation unit in real time to obtain a main current transformation internal potential vector; collecting the active power and reactive power of each sub-current conversion unit in real time, and obtaining a sub-current conversion internal potential vector of each sub-current conversion unit by combining the main current conversion internal potential vector and the active power and reactive power of the main current conversion unit; obtaining an internal potential reference wave of the main current transformation unit based on the internal potential vector of the main current transformation, and further obtaining a driving pulse signal of the main current transformation unit; and obtaining an internal potential reference wave of each sub-converter unit based on each sub-converter internal potential vector, and further obtaining a driving pulse signal of each sub-converter unit. According to the technical scheme, the problems of unit external characteristic inconsistency and internal stability of the energy storage converter in a multi-unit parallel connection type application scene can be solved.

Description

Technical Field

[0001] This invention belongs to the field of energy storage system control, and in particular to a method and system for reshaping the external characteristics of a multi-unit energy storage converter based on grid technology. Background Technology

[0002] In recent years, the proportion of renewable energy in the power grid has been continuously increasing, while the grid's capacity to support high proportions of new energy and power electronic equipment has been gradually declining, seriously threatening the safe and stable operation of the next-generation power system. Grid construction technology is currently a feasible means to solve the stability problem of future power grids with high proportions of new energy. Power electronic converters based on grid construction technology have external characteristics similar to conventional synchronous generator units and can provide all the functions of conventional generator units, such as inertia support, frequency and voltage regulation, and increased short-circuit capacity, showing broad application prospects in the construction of new power systems.

[0003] On the other hand, high-power centralized energy storage converters are currently the most widely used technology in large-capacity energy storage projects in China. They feature a simple architecture, low construction, installation, and maintenance costs, and facilitate cluster control of energy storage power stations. To match mainstream large-capacity battery cells, the converter typically uses two or more converter units connected in parallel and sharing a DC bus. Furthermore, for flow batteries, to match their low-voltage, high-current characteristics, multiple converter units must be connected in parallel, while the overall design must appear as a single energy storage converter to facilitate integration into the corresponding battery management system.

[0004] In this application scenario, traditional control strategies for multi-unit parallel energy storage inverters are no longer suitable for grid-connected configurations. One traditional approach is a master-slave control method, where the master generates an outer voltage loop and an inner current loop, while the slave only retains the inner current loop and follows the commands generated by the master. However, this control method has shortcomings; the slave cannot exhibit strong voltage source characteristics, and there are differences in external characteristics between the slave and master. For example, Chinese patent CN106849186A discloses a master-slave control method for energy storage inverters based on a virtual synchronous generator. The master inverter uses a voltage source output method based on a virtual synchronous generator to provide grid voltage amplitude and frequency, while the slave inverter uses a current source output method. Due to the presence of the inner current loop, the slave inverter in this method cannot exhibit strong voltage source characteristics, weakening the technical advantages of grid-connected voltage sources. Chinese patent CN117134381A discloses a coordinated control method and system for grid-type and grid-following energy storage converters. The grid-type and grid-following energy storage converters form a master-slave architecture. However, the system architecture described in this method is not for a single battery cell, and some converters still have the characteristics of current source external.

[0005] Another traditional approach is to use parallel control, simulating all submodules as independent voltage sources and employing a single upper-level controller for power sharing. However, in this method, each submodule generates its own voltage and phase. Due to the low interconnection impedance, this can easily lead to oscillations and circulating currents during grid disturbances. Furthermore, since each submodule presents itself as multiple voltage sources, the power of each module is adjusted downwards according to its own characteristics, resulting in uncontrolled dynamic power summation and making it difficult to respond to current-limiting commands from the battery management system. For example, Chinese patent CN116599139A discloses a flexible DC energy grid control device and an MMC control system. This method controls the capacitor energy of the MMC submodules, enabling the MMC to achieve autonomous grid synchronization without a phase-locked loop. However, in this method, each MMC submodule generates its own phase, which can lead to stability issues during grid disturbances. Additionally, the system contains multiple independent voltage sources, making it unsuitable for integration into a single battery management system. Chinese patent CN117477670A discloses a three-phase cascaded grid power supply structure and its multi-level multi-objective power regulation method. This method uses a central controller to send voltage references to the power modules through droop control. However, its control object is the entire cascaded system, which is difficult to characterize the characteristics of individual sub-modules. In addition, the central controller needs to collect the power values ​​of all modules in real time, resulting in a large amount of communication data. Therefore, it is only suitable for high-voltage cascaded systems with multiple modules connected in series, and is not suitable for the application scenarios of multi-unit parallel energy storage converters. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for reshaping the external characteristics of a multi-unit energy storage converter based on grid technology. This method transmits the voltage source characteristics of the main converter unit to the sub-converter units in real time, enabling all sub-converter units to exhibit strong voltage source characteristics externally. This solves the problems of inconsistent external characteristics and internal stability of energy storage converters in multi-unit parallel application scenarios.

[0007] To achieve the above objectives, the solution of the present invention is:

[0008] A method for reshaping the external characteristics of a multi-unit energy storage converter based on grid-connected technology, wherein the multi-unit energy storage converter includes a main converter unit and at least one sub-converter unit; the method includes the following steps:

[0009] Step 1: Real-time acquisition of active power P1 and reactive power Q1 of the main converter unit to obtain the internal potential vector of the main converter. Where U1 is the magnitude of the internal potential vector, and ω1 is the angular velocity of the internal potential vector.

[0010] Step 2: Real-time acquisition of active and reactive power of each sub-converter unit, and calculation of the sub-converter internal potential vector of each sub-converter unit based on the main converter internal potential vector, the active and reactive power of the main converter unit. Where n represents the serial number of the sub-converter unit, n is an integer, 1≤n≤m-1;

[0011] Step 3: Obtain the internal potential reference wave of the main converter unit based on the internal potential vector of the main converter. The internal potential reference wave of each sub-converter unit is obtained based on the internal potential vector of each sub-converter unit.

[0012]

[0013] Step 4: Based on the internal potential reference wave of the main converter unit, obtain the driving pulse signal of the main converter unit through pulse width modulation; based on the internal potential reference wave of each sub-converter unit, obtain the driving pulse signal of each sub-converter unit through pulse width modulation.

[0014] In step 1 above, the angular velocity ω1 of the internal potential vector is obtained according to the following formula:

[0015]

[0016] Where f1 is the internal potential frequency of the main converter unit, and f DZ For frequency adjustment dead zone, f N P is the rated frequency of the power grid. N K represents the total rated active power of the energy storage converter. f T is the active frequency regulation coefficient. j Let m be the inertial time constant, and m be the total number of main converter units and sub-converter units, where m ≥ 2.

[0017] P ref_unit For active power commands, we have:

[0018]

[0019] Among them, P ref The total active power command received by the energy storage converter.

[0020] In step 1 above, the magnitude U1 of the internal potential vector is obtained according to the following formula:

[0021]

[0022] Where m is the total number of main converter units and sub-converter units; U N S is the rated voltage of the AC port of the energy storage converter. N K represents the total rated apparent power of the energy storage converter. U U is the reactive power voltage regulation coefficient. DZ This is a voltage regulation dead zone;

[0023] Q ref_unit For reactive power commands, we have:

[0024]

[0025] Among them, Q ref The total reactive power command received by the energy storage converter.

[0026] In step 2 above, the active power P1 is subtracted from the active power P. n The obtained error, after PI adjustment, is superimposed with the rotational angular velocity ω1 to obtain the rotational angular velocity ω of the potential vector in the nth sub-converter unit. n ;

[0027] Subtract the reactive power Q from the reactive power Q1 n The obtained error is adjusted by PI and then superimposed with the amplitude U1 to obtain the amplitude U of the potential vector in the nth sub-converter unit. n .

[0028] Step 3 above also includes a fault rate limiting strategy, the content of which is:

[0029] The three-phase alternating current I a_m ,I b_m ,I a_m Perform synchronous rotational coordinate transformation to obtain the dq axis components I d_m ,I q_m The amplitude of the alternating current I is obtained. ac_m Among them, I a_m ,I b_m ,I a_m The three-phase AC current of the main converter unit or the sub-converter unit;

[0030] If I ac_m Greater than threshold I limit If a current-limiting virtual impedance is applied, the current is limited; otherwise, an internal potential reference wave is generated.

[0031] A multi-unit energy storage converter external characteristic reshaping system based on grid-connected technology, wherein the multi-unit energy storage converter includes a main converter unit and at least one sub-converter unit; including,

[0032] The main converter internal potential vector acquisition module is configured to obtain the main converter internal potential vector based on the real-time acquired active power P1 and reactive power Q1 of the main converter unit. Where U1 is the magnitude of the internal potential vector, and ω1 is the angular velocity of the internal potential vector.

[0033] The sub-converter internal potential vector acquisition module is configured to calculate the sub-converter internal potential vector of each sub-converter unit based on the real-time collected active and reactive power of each sub-converter unit, and in combination with the main converter internal potential vector, the active and reactive power of the main converter unit, and so on. Where n represents the serial number of the sub-converter unit, n is an integer, 1≤n≤m-1;

[0034] The internal potential reference wave acquisition module is configured to obtain the internal potential reference wave of the main converter unit based on the internal potential vector of the main converter. The internal potential reference wave of each sub-converter unit is obtained based on the internal potential vector of each sub-converter unit. as well as,

[0035] The drive pulse signal acquisition module is configured to obtain the drive pulse signal of the main converter unit by pulse width modulation based on the internal potential reference wave of the main converter unit; and to obtain the drive pulse signal of each sub-converter unit by pulse width modulation based on the internal potential reference wave of each sub-converter unit.

[0036] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, it implements the steps of the external characteristic reshaping method for a multi-cell energy storage converter based on grid technology as described above.

[0037] A computer-readable storage medium storing a computer program; when executed by a processor, the computer program implements the steps of the aforementioned method for reshaping the external characteristics of a multi-cell energy storage converter based on network technology.

[0038] The main beneficial effects of this invention after adopting the above solution are as follows:

[0039] 1. The main converter unit generates an internal potential with its own electrical quantities as a reference and transmits the characteristics of the grid voltage source to the sub-converter units in real time. Therefore, the external characteristics of the voltage source of all converter units tend to be consistent, which can eliminate or reduce the power oscillation and circulating current problems caused by the differences between units.

[0040] 2. Compared with the traditional master-slave control method, the sub-converter unit of this invention inherits the internal potential characteristics of the master converter unit and does not contain a current inner loop. Therefore, all converter units exhibit strong voltage source characteristics externally and can operate stably under weak power grid conditions.

[0041] 3. When a fault occurs in the external power grid, each converter unit limits its own fault current. Compared with the method of issuing commands from the upper controller, the current limiting speed is faster and the reliability is higher.

[0042] 4. Only the main converter unit communicates with the battery management system, background monitoring system, or coordination control system. Sub-converter modules do not participate in related communications. All units are presented as a single energy storage converter, which facilitates response to real-time current limiting commands from the battery management system.

[0043] This invention is applicable to large-capacity grid-type energy storage power stations or flow battery energy storage power stations. The solution is easy to implement and has high engineering practical value. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the multi-unit energy storage converter structure used in this invention;

[0045] Among them, (a) is the form of a two-winding transformer, and (b) is the form of a double-split transformer;

[0046] Figure 2 This is a control block diagram of a multi-unit energy storage converter external characteristic reshaping method based on grid technology according to the present invention, wherein (a) is the control block diagram of the main converter unit and (b) is the control block diagram of the sub-converter unit.

[0047] Figure 3 This is a flowchart of a method for reshaping the external characteristics of a multi-unit energy storage converter based on grid technology according to the present invention. Detailed Implementation

[0048] The technical solution and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.

[0049] This invention provides a method for reshaping the external characteristics of a multi-cell energy storage converter based on grid-connected technology. The multi-cell energy storage converter used in this method is such as... Figure 1 As shown, (a) uses a dual-winding transformer, and (b) uses a dual-split transformer. The multi-unit energy storage converter includes m converter units, where m is an integer and m≥2; the first converter unit is the main converter unit, and the rest are sub-converter units; all converter units adopt a three-phase three-level topology. The DC side of the main converter unit and (m-1) sub-converter units are connected to the same battery in parallel, and the AC side is connected to their respective transformer windings, and finally connected to the external power grid through the AC bus.

[0050] The method includes the following steps:

[0051] Step 1: Real-time acquisition of active power P1 and reactive power Q1 of the main converter unit to obtain the internal potential vector of the main converter. Where U1 is the magnitude of the internal potential vector, and ω1 is the angular velocity of the internal potential vector.

[0052] Step 2: Real-time acquisition of active and reactive power of each sub-converter unit, and calculation of the sub-converter internal potential vector of each sub-converter unit based on the main converter internal potential vector, the active and reactive power of the main converter unit. Where n represents the serial number of the sub-converter unit, n is an integer, 1≤n≤m-1;

[0053] Step 3: Obtain the internal potential reference wave of the main converter unit based on the internal potential vector of the main converter. The internal potential reference wave of each sub-converter unit is obtained based on the internal potential vector of each sub-converter unit.

[0054]

[0055] Step 4: Based on the internal potential reference wave of the main converter unit, obtain the driving pulse signal of the main converter unit through pulse width modulation; based on the internal potential reference wave of each sub-converter unit, obtain the driving pulse signal of each sub-converter unit through pulse width modulation.

[0056] This invention also provides a multi-unit energy storage converter external characteristic reshaping system based on grid-connected technology, comprising,

[0057] The main converter internal potential vector acquisition module is configured to obtain the main converter internal potential vector based on the real-time acquired active power P1 and reactive power Q1 of the main converter unit. Where U1 is the magnitude of the internal potential vector, and ω1 is the angular velocity of the internal potential vector.

[0058] The sub-converter internal potential vector acquisition module is configured to calculate the sub-converter internal potential vector of each sub-converter unit based on the real-time collected active and reactive power of each sub-converter unit, and in combination with the main converter internal potential vector, the active and reactive power of the main converter unit, and so on. Where n represents the serial number of the sub-converter unit, n is an integer, 1≤n≤m-1;

[0059] The internal potential reference wave acquisition module is configured to obtain the internal potential reference wave of the main converter unit based on the internal potential vector of the main converter. The internal potential reference wave of each sub-converter unit is obtained based on the internal potential vector of each sub-converter unit. as well as,

[0060] The drive pulse signal acquisition module is configured to obtain the drive pulse signal of the main converter unit by pulse width modulation based on the internal potential reference wave of the main converter unit; and to obtain the drive pulse signal of each sub-converter unit by pulse width modulation based on the internal potential reference wave of each sub-converter unit.

[0061] In a preferred embodiment of the present invention, some functions can be modularized, such as... Figure 2 As shown, the control modules involved include: a swing equation module, a droop module, a power calibration module, a fault current limiting module, and a pulse width modulation wave generation module. Among them, the swing equation module and the droop module exist only in the main converter unit, and the power calibration module exists only in the sub-converter unit.

[0062] The present invention discloses a method for reshaping the external characteristics of a multi-unit energy storage converter based on grid-connected technology, which is carried out according to the following steps, such as... Figure 3 As shown.

[0063] Step S01: The main converter unit collects its own real-time active power P1 and reactive power Q1, and calculates the active power command P. ref_unit and reactive power command Q ref_unit Then, it calculates and generates its own internal potential vector through the swing equation module and the drooping module.

[0064] The swing equation module generates the rotational angular velocity ω1 of the internal potential vector according to the following strategy:

[0065]

[0066] Where f1 is the internal potential frequency of the main converter unit, f DZ For frequency adjustment dead zone, f N P is the rated frequency of the power grid. N K represents the total rated active power of the energy storage converter. f T is the active frequency regulation coefficient. j is the inertial time constant.

[0067] The drooping module generates the magnitude U1 of the internal potential vector according to the following strategy:

[0068]

[0069] Among them U N S is the rated voltage of the AC port of the energy storage converter. N K represents the total rated apparent power of the energy storage converter. U U is the reactive power voltage regulation coefficient. DZ This is the voltage regulation dead zone.

[0070] Active power command P ref_unit and reactive power command Q ref_unit Generate according to the following strategy:

[0071] According to the total active power command P received by the energy storage converter ref Total reactive power command Q ref The active power command P of the converter unit is calculated based on the total number of converter units, m. ref_unit and reactive power command Q ref_unit ,Right now

[0072]

[0073] Step S02: The main converter unit converts the internal potential vector Real-time active power P1 and reactive power Q1 are transmitted to the sub-converter unit via real-time communication.

[0074] The sub-converter unit collects its own real-time active power P n and reactive power Q n And with the internal potential vector of the main converter unit Based on active power P1 and reactive power Q1, power calibration is performed through a power calibration module to generate its own internal potential vector. Where n represents the serial number of the converter unit, and n is an integer, 1≤n≤m-1.

[0075] The power calibration module generates the internal potential vector according to the following strategy.

[0076] 1) Use a PI controller to subtract P from P1. n The resulting error is fed into the PI controller for calculation, and the output result is superimposed on the rotational angular velocity ω1 of the internal potential vector, i.e. Where k p_ω k is the proportional coefficient of the PI controller. i_ω is the integral coefficient of the PI controller, and s is a complex variable in the Laplace transform;

[0077] 2) Use a PI controller to subtract Q from Q1. n The resulting error is fed into the PI controller for calculation, and the output result is superimposed on the amplitude U1 of the internal potential vector, i.e. Where k p_u k is the proportional coefficient of the PI controller. i_u is the integral coefficient of the PI controller, and s is a complex variable in the Laplace transform.

[0078] Step S04: Internal potential vector of the main converter unit Internal potential vector of the sub-converter unit Each module generates its own final internal potential reference wave through its respective fault current limiting module. and

[0079]

[0080] The fault current limiting module generates an internal potential reference wave according to the following strategy. and Each converter unit samples its own three-phase AC current I. a_m I b_m I c_m After performing synchronous rotating coordinate transformation, the dq-axis components I of the three-phase alternating current are obtained. d_m and I q_m And the amplitude of the alternating current I is calculated. ac_m ,Right now When the current amplitude I is determined ac_n Greater than threshold I limit When the fault current limiting module is activated, it uses the current limiting virtual impedance to limit the current; otherwise, it directly generates the final internal potential reference wave.

[0081] Step S05: Internal potential reference wave of each converter unit and The pulse width modulation wave generation module ultimately generates the drive pulse signal for each converter unit.

[0082] This invention also provides another computer device, including a processor and a memory configured to store a computer program capable of running on the processor; wherein, when the processor is configured to run the computer program, it performs the method steps described in the foregoing embodiments.

[0083] In practical applications, the aforementioned processor includes a Field-Programmable Gate Array (FPGA), and the processor can be a Central Processing Unit (CPU) or a Digital Signal Processor (DSP). It is understood that for different devices, the electronic devices used to implement the functions of the aforementioned processor can also be other types, and this embodiment of the invention does not impose specific limitations.

[0084] The aforementioned memory can be volatile memory, such as random-access memory (RAM); or non-volatile memory, such as read-only memory (ROM), flash memory, hard disk drive (HDD), or solid-state drive (SSD); or a combination of the above types of memory, and provides instructions and data to the processor.

[0085] In an exemplary embodiment, the present invention also provides a computer-readable storage medium for storing a computer program.

[0086] Optionally, the computer-readable storage medium can be applied to any of the methods in the embodiments of the present invention, and the computer program causes the computer to execute the corresponding processes implemented by the processor in the various methods of the embodiments of the present invention. For the sake of brevity, these will not be described in detail here.

[0087] In the several embodiments provided by this invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be electrical, mechanical, or other forms.

[0088] 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 implemented 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. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0093] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for reshaping the external characteristics of a multi-unit energy storage converter based on grid-connected technology, wherein the multi-unit energy storage converter comprises a main converter unit and at least one sub-converter unit; characterized in that... Includes the following steps: Step 1: Real-time acquisition of active power P1 and reactive power Q1 of the main converter unit to obtain the internal potential vector of the main converter. Where U1 is the magnitude of the internal potential vector, and ω1 is the angular velocity of the internal potential vector. Step 2: Real-time acquisition of active and reactive power of each sub-converter unit, and calculation of the sub-converter internal potential vector of each sub-converter unit based on the main converter internal potential vector, the active and reactive power of the main converter unit. Where n represents the serial number of the sub-converter unit, n is an integer, 1≤n≤m-1; Step 3: Obtain the internal potential reference wave of the main converter unit based on the internal potential vector of the main converter. The internal potential reference wave of each sub-converter unit is obtained based on the internal potential vector of each sub-converter unit. Step 4: Based on the internal potential reference wave of the main converter unit, obtain the driving pulse signal of the main converter unit through pulse width modulation; based on the internal potential reference wave of each sub-converter unit, obtain the driving pulse signal of each sub-converter unit through pulse width modulation.

2. The method as described in claim 1, characterized in that: In step 1, the rotational angular velocity ω1 of the internal potential vector is obtained according to the following formula: Where f1 is the internal potential frequency of the main converter unit, and f DZ For frequency adjustment dead zone, f N P is the rated frequency of the power grid. N K represents the total rated active power of the energy storage converter. f T is the active frequency regulation coefficient. j Let m be the inertial time constant, and m be the total number of main converter units and sub-converter units, where m ≥ 2. P ref_unit For active power commands, we have: Among them, P ref The total active power command received by the energy storage converter.

3. The method as described in claim 1, characterized in that: In step 1, the magnitude U1 of the internal potential vector is obtained according to the following formula: Where m is the total number of main converter units and sub-converter units; U N S is the rated voltage of the AC port of the energy storage converter. N K represents the total rated apparent power of the energy storage converter. U U is the reactive power voltage regulation coefficient. DZ This is a voltage regulation dead zone; Q ref_unit For reactive power commands, we have: Among them, Q ref The total reactive power command received by the energy storage converter.

4. The method as described in claim 1, characterized in that: In step 2, the active power P1 is subtracted from the active power P. n The obtained error, after PI adjustment, is superimposed with the rotational angular velocity ω1 to obtain the rotational angular velocity ω of the potential vector in the nth sub-converter unit. n ; Subtract the reactive power Q from the reactive power Q1 n The obtained error is adjusted by PI and then superimposed with the amplitude U1 to obtain the amplitude U of the potential vector in the nth sub-converter unit. n .

5. The method as described in claim 1, characterized in that: Step 3 also includes a fault-limiting strategy, the content of which is: The three-phase alternating current I a_m ,I b_m ,I a_m Perform synchronous rotational coordinate transformation to obtain the dq axis components I d_m ,I q_m The amplitude of the alternating current I is obtained. ac_m Among them, I a_m ,I b_m ,I a_m The three-phase AC current of the main converter unit or the sub-converter unit; If I ac_m Greater than threshold I limit If a current-limiting virtual impedance is applied, the current is limited; otherwise, an internal potential reference wave is generated.

6. A multi-unit energy storage converter external characteristic reshaping system based on grid-connected technology, wherein the multi-unit energy storage converter comprises a main converter unit and at least one sub-converter unit; characterized in that: include, The main converter internal potential vector acquisition module is configured to obtain the main converter internal potential vector based on the real-time acquired active power P1 and reactive power Q1 of the main converter unit. Where U1 is the magnitude of the internal potential vector, and ω1 is the angular velocity of the internal potential vector. The sub-converter internal potential vector acquisition module is configured to calculate the sub-converter internal potential vector of each sub-converter unit based on the real-time collected active and reactive power of each sub-converter unit, and in combination with the main converter internal potential vector, the active and reactive power of the main converter unit, and so on. Where n represents the serial number of the sub-converter unit, n is an integer, 1≤n≤m-1; The internal potential reference wave acquisition module is configured to obtain the internal potential reference wave of the main converter unit based on the internal potential vector of the main converter. The internal potential reference wave of each sub-converter unit is obtained based on the internal potential vector of each sub-converter unit. as well as, The drive pulse signal acquisition module is configured to obtain the drive pulse signal of the main converter unit by pulse width modulation based on the internal potential reference wave of the main converter unit; and to obtain the drive pulse signal of each sub-converter unit by pulse width modulation based on the internal potential reference wave of each sub-converter unit.

7. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, it implements the steps of the external characteristic reshaping method for a multi-cell energy storage converter based on network technology as described in any one of claims 1 to 5.

8. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by the processor, it implements the steps of the external characteristic reshaping method for a multi-cell energy storage converter based on network technology as described in any one of claims 1 to 5.

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