A method, device and equipment for controlling multiple energy storage converters in parallel, and a storage medium

Abstract

The application provides a multi-machine parallel control method, device and equipment of an energy storage converter and a storage medium. The method comprises the following steps: firstly, a grid-connected system in parallel with the energy storage converter is disassembled into multiple equivalent circuits under separate excitation, and a transfer function between a response current of each equivalent circuit and an excitation source is established. Subsequently, a Bode diagram of the transfer function changing with the number of parallel connections is determined, and a frequency response closed-loop transfer function of each energy storage converter is obtained according to the transfer function and a power expression of the energy storage converter to a common bus voltage. Finally, control parameters are determined in combination with the Bode diagram and the closed-loop transfer function, and multi-machine parallel control is realized. The method discloses the interaction of the frequency responses among the energy storage converters, and provides a theoretical basis for system control parameter selection and frequency optimization control.

Description

Technical Field

[0001] This application belongs to the field of power grid peak shaving, and in particular relates to a method, device, equipment and storage medium for multi-unit parallel control of energy storage converters. Background Technology

[0002] As the interface between the energy storage system and the power grid, the performance of the energy storage converter has a significant impact on the stability of the power system. As new energy sources gradually become the main source of electricity in the power system, more devices with active support capabilities, such as energy storage, are needed to take on the responsibility of voltage and frequency regulation. Active support energy storage systems not only have the ability to support grid stability but also combine conventional energy storage, reactive power compensation, and other functions, making them crucial for ensuring the stable operation of high-proportion new energy systems.

[0003] In renewable energy grid-connected scenarios, multiple energy storage VSCs are often required to operate in parallel to provide greater capacity and more flexible control strategies. Complex interactions exist between the power sources in a multi-VSC parallel system, including the characteristics of the VSC itself, the interactions between VSCs, and the interactions between the VSCs and the grid power source. These complex interactions can lead to system stability issues, especially as the number of parallel units increases. Summary of the Invention

[0004] The purpose of this application is to overcome the above-mentioned prior art and provide a method, device, equipment and storage medium for multi-machine parallel control of energy storage converters.

[0005] This application provides a method for controlling multiple parallel operation of energy storage converters, including:

[0006] The grid-connected system with parallel energy storage converters is decomposed into multiple equivalent circuits under separate excitations;

[0007] Establish the transfer function between the response current and the excitation source when each of the equivalent circuits operates independently;

[0008] Determine the Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters;

[0009] Based on the transfer function between the response current and the excitation source and the power expression of the i-th energy storage converter to the common bus voltage, the frequency response closed-loop transfer function of the i-th energy storage converter is determined.

[0010] The control parameters of the energy storage converter are determined based on the Bode plot and the frequency response closed-loop transfer function, and multi-machine parallel control is performed.

[0011] Optionally, the grid-connected system with parallel energy storage converters can be decomposed into multiple equivalent circuits under separate excitations, including:

[0012] Based on the voltage source configuration, the grid-connected system of multiple energy storage converters connected in parallel is equivalent to an equivalent circuit under the excitation of multiple individual voltage sources.

[0013] Optionally, the transfer function between the response current and the excitation source includes: transfer functions G1, G2, and G3 under the action of Us1 alone, Usk alone, and Ug alone.

[0014] Optionally, determining the Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters includes:

[0015] Bode plots under different excitation sources are obtained by calculating the changes in transfer functions G1, G2, and G3 as the number of parallel energy storage converters increases.

[0016] Optionally, in the step of determining the control parameters of the energy storage converter based on the Bode plot and the frequency response closed-loop transfer function,

[0017] By analyzing the impact of changes in the inertia and damping parameters of each energy storage converter in a grid-connected system with parallel energy storage converters on the frequency response characteristics of other energy storage converters, optimized control parameters are determined.

[0018] Optionally, the control parameters include virtual inertia and virtual damping.

[0019] Optionally, it also includes:

[0020] A simulation model of the energy storage converter was built using MATLAB / Simulink software.

[0021] This application also provides a multi-unit parallel control device for energy storage converters, including:

[0022] The decomposition module decomposes the grid-connected system with parallel energy storage converters into multiple equivalent circuits under separate excitations;

[0023] The transfer module establishes the transfer function between the response current and the excitation source when each equivalent circuit acts alone.

[0024] The mapping module determines the Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters;

[0025] The closed-loop module determines the frequency response closed-loop transfer function of the i-th energy storage converter based on the transfer function between the response current and the excitation source and the power expression of the i-th energy storage converter to the common bus voltage.

[0026] The control module determines the control parameters of the energy storage converter based on the Bode plot and the frequency response closed-loop transfer function, and performs multi-unit parallel control.

[0027] This application also provides a multi-unit parallel control device for energy storage converters, including:

[0028] Memory;

[0029] The processor is configured to retrieve the computer-executable program of the above-described multi-unit parallel control method for energy storage converters from the memory, and execute the following steps: decomposing the grid-connected system of parallel energy storage converters into multiple equivalent circuits under individual excitation; establishing the transfer function between the response current and the excitation source when each equivalent circuit operates independently; determining the Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters; determining the frequency response closed-loop transfer function of the i-th energy storage converter based on the transfer function between the response current and the excitation source and the power expression of the i-th energy storage converter transferred to the common bus voltage; and determining the control parameters of the energy storage converter based on the Bode plot and the frequency response closed-loop transfer function, thereby performing multi-unit parallel control.

[0030] This application also provides a storage medium, comprising: storing a computer-executable program, the computer-executable program being invoked by a processor to execute the steps of the above-described energy storage converter multi-machine parallel control method.

[0031] The beneficial effects of this application are:

[0032] This application provides a method for parallel control of multiple energy storage converters, comprising: decomposing a grid-connected system of parallel energy storage converters into multiple equivalent circuits under individual excitation; establishing the transfer function between the response current and the excitation source when each equivalent circuit operates independently; determining a Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters; determining the frequency response closed-loop transfer function of the i-th energy storage converter based on the transfer function between the response current and the excitation source and the power expression of the voltage transferred to the common bus by the i-th energy storage converter; determining the control parameters of the energy storage converter based on the Bode plot and the frequency response closed-loop transfer function, and performing multi-converter parallel control. This application discloses the interaction between the control parameter changes of one energy storage converter and the frequency response of another in the system, providing a theoretical basis for the selection of control parameters and the optimized control of the system frequency in a grid-connected system of multiple parallel energy storage converters. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the multi-unit parallel control process of the energy storage converter in this application;

[0034] Figure 2 This is a schematic diagram of a typical control structure for energy storage VSC in this application;

[0035] Figure 3 This is a schematic diagram of the equivalent circuit under the interaction of various excitation sources in this application;

[0036] Figure 4(a) shows the U in this application. s1 Bode plot under the influence of excitation sources;

[0037] Figure 4(b) shows the U in this application. sk Bode plot under the influence of excitation sources;

[0038] Figure 4(c) shows the U in this application. g Bode plot under the influence of excitation sources;

[0039] Figure 5(a) is a Bode plot of the motion trajectory of J2 in this application;

[0040] Figure 5(b) is a Bode plot of motion trajectory of D2 increasing in this application;

[0041] Figure 5(c) is the root locus diagram when J2 and D2 increase in this application;

[0042] Figure 6(a) is a harmonic analysis diagram of the output current when the number of parallel energy storage VSCs increases in this application;

[0043] Figure 6(b) is a harmonic analysis diagram of the output current when the number of parallel 3 energy storage VSCs in this application increases;

[0044] Figure 7(a) is a waveform diagram of PCS-VSC1 frequency when J2 changes in this application;

[0045] Figure 7(b) is the active power waveform of PCS-VSC1 when J2 changes in this application;

[0046] Figure 7(c) is a waveform diagram of PCS-VSC1 frequency when D2 changes in this application;

[0047] Figure 7(d) is the active power waveform of PCS-VSC1 when D2 changes in this application. Detailed Implementation

[0048] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0049] Please refer to Figure 1As shown, this application provides a method for multi-unit parallel control of energy storage converters, including:

[0050] S101. Decompose the grid-connected system with parallel energy storage converters into multiple equivalent circuits under separate excitations.

[0051] like Figure 2 As shown, this is the grid-connected architecture of an energy storage converter (energy storage VSC).

[0052] In the main circuit structure, L and R L C and L represent the filter inductor, resistor, and capacitor of the inverter, respectively; g and R g These are the line inductance and resistance, respectively.

[0053] DC side V dc This refers to the voltage of the energy storage system.

[0054] e ck (k = a, b, c) means that the voltage of the AC filter capacitor is equal to the AC output voltage of the energy storage VSC.

[0055] e cd e cq It is the dq axis component after coordinate transformation.

[0056] i Lk and i k (k = a, b, c) represent the inductor current of the AC filter and the AC output current of the energy storage VSC, respectively.

[0057] i Ld i Lq and i d i q is i Lk and i k The dq axis components.

[0058] uk represents the grid voltage at the connection point.

[0059] u od and u oq These are the dq-axis components of the VSC control voltage, respectively.

[0060] Virtual synchronous machine control mainly consists of two parts:

[0061] (1) Active-frequency control is introduced into the mathematical model of the synchronous machine. The rotor mechanical equation model of the synchronous machine is used to determine the inertia and damping characteristics of the synchronous machine.

[0062] (2) Reactive power-voltage control simulates the excitation characteristics of a synchronous machine, giving the energy storage VSC voltage regulation capability, as shown in the following formula;

[0063]

[0064] In the formula, J and D are the virtual inertia and virtual damping, respectively, and ω, ω0, and Δω are the VSC output angular frequency, rated frequency, and the difference between the two, respectively; ω bus AC bus angular frequency; P ref This is the active power reference value; P out δ represents the output active power of VSC; δ represents the output voltage phase of the converter, i.e., the reference phase.

[0065]

[0066] In the formula, K q Q is the integral coefficient; ref Q0 is the reactive power reference value; Q0 is the reactive power output of VSC; D q e is the reactive power voltage regulation coefficient; cn is the reference value for voltage amplitude; E is the internal potential of the energy storage VSC.

[0067] like Figure 3 As shown, the energy storage VSC multi-unit parallel grid-connected system mainly consists of the energy storage VSC equivalent power supply Us, the equivalent impedance of the LCL filter circuit, the line equivalent impedance, and the grid power supply.

[0068] This application utilizes MATLAB / Simulink software to build... Figure 2 The main simulation parameters of the energy storage VSC simulation model shown are shown in Table 1.

[0069] Table 1 Main Control Parameters of Voltage Source Type Energy Storage Parallel System

[0070]

[0071]

[0072] S102. Establish the transfer function between the response current and the excitation source when each of the equivalent circuits operates alone.

[0073] Based on the equivalent circuit, establish U respectively s1 U sk U g When used alone, it corresponds to I r1 The transfer functions G1, G2, and G3 between the response current and the three excitation sources are expressed as follows:

[0074]

[0075] in:

[0076]

[0077] S103. Determine the Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters.

[0078] like Figure 4(a) , 4(b) As shown in Figure 4(c), the Bode plots of the transfer functions G1, G2, and G3 as a function of the number of parallel energy storage VSCs are shown.

[0079] WhenU s1 Under its own excitation, as the number of parallel connections increases, the resonant peak point shifts towards lower frequencies. Therefore, the possibility of low-frequency resonance in the parallel VSC energy storage system will increase under the excitation of the converter itself.

[0080] WhenU sk Under excitation, as the number of parallel connections increases, the resonant point at low frequencies remains unchanged, while the resonant point at high frequencies shifts to low frequencies. Although the amplitude decreases, the possibility of resonance still exists.

[0081] When the grid power supply U g Under excitation, as the number of parallel connections increases, the high-frequency resonant peak shifts towards the low-frequency direction, while the low-frequency resonant peak does not shift, and the amplitude changes of both are small; under the excitation of the corresponding grid power source, the probability of the first energy storage VSC grid-connected current experiencing low-frequency resonance increases.

[0082] As the above analysis shows, with the number of parallel energy storage VSCs gradually increasing, the entire parallel energy storage VSC system exhibits different resonance characteristics under different voltage source excitations. Overall, the increased number of parallel units increases the likelihood of resonance in the parallel energy storage VSC system.

[0083] S104. Based on the transfer function between the response current and the excitation source and the power expression of the i-th energy storage converter transferred to the common bus voltage, determine the frequency response closed-loop transfer function of the i-th energy storage converter.

[0084] The power transferred from the i-th energy storage VSC to the common bus voltage can be expressed as:

[0085]

[0086] In the formula: e ci K represents the output voltage amplitude. i =1.5eciUg / Xg, where Xg is the equivalent line inductive reactance; P outi Let be the active power output of the i-th energy storage VSC.

[0087] Combining the transfer function and the power transferred from the i-th energy storage VSC to the common bus voltage, we can obtain:

[0088]

[0089] From the above equation, the closed-loop transfer function of the frequency response of the i-th energy storage VSC can be obtained as follows:

[0090]

[0091] For example:

[0092] When the J2 and D2 parameters of the parallel PCS-VSC2 change, its Δω1(s) / ΔP load The Bode plot of the amplitude-frequency response curve of (s) is shown below. Figure 5(a) , 5(b) As shown.

[0093] Figures 5(a) and 5(b) show the effects of control parameters J2 and D2 of PCS-VSC2 on the frequency response of PCS-VSC1 in a parallel system of two energy storage VSCs. When J2 of PCS-VSC2 increases, the low-frequency resonant point of PCS-VSC1 moves to the lower left corner of the Bode plot. It can be seen that with the same load fluctuation, increasing J2 will affect the frequency response stability of PCS-VSC1, but has no significant effect in the high-frequency region, that is, it has no significant effect on the maximum frequency deviation rate (RoCoF) of Δω1. When D2 of PCS-VSC2 increases, the low-frequency resonant point of PCS-VSC1 weakens, and the amplitude-frequency characteristic curve in the high-frequency region does not change significantly. It can be seen that the value of D2 has a smaller effect on the RoCoF of PCS-VSC1 frequency response. However, as D2 increases, the amplitude in the low-frequency range (<1Hz) decreases. It can be seen that increasing D2 can improve the frequency response stability of PCS-VSC1.

[0094] Figure 5(c) shows the Δω1(s) / ΔP as J2 and D2 increase. load From the root locus diagram of (s), we can see that there are 5 eigenvalues, among which S 11 S 12 S is a pair of invariant conjugate complex roots. 21 S 22 These are a pair of conjugate complex roots, and their directions of change are shown by the arrows in the figure. S3 lies on the real axis, and its direction of change is as indicated by the arrows. When J2 increases, S... 21 S 22 As J2 moves to the left of the complex plane, the stability of PCS-VSC1 improves, but if J2 is too large, S3 moves to the right of the complex plane, reducing the stability margin. When D2 increases, S21, S22, and S3 all move to the left of the complex plane, indicating that increasing D2 will improve the frequency modulation stability of PCS-VSC1 to a greater extent.

[0095] Here's another example:

[0096] Figures 6(a) and 6(b) show the PCC current harmonic analysis diagrams for two and three energy storage VSCs connected in parallel. PCS-VSC2 and PCS-VSC3 have the same configuration. As the number of energy storage VSCs connected in parallel increases, the output current THD value of the parallel energy storage VSC system increases. It can be seen that for energy storage VSCs with the same configuration, the stability will deteriorate as the number of parallel connections increases.

[0097] Taking two energy storage VSCs connected in parallel to the grid as an example, this paper analyzes the impact of changes in the inertia and damping parameters of PCS-VSC2 on the frequency characteristics of PCS-VSC1.

[0098] Please refer to Figures 7(a), 7(b), 7(c), and 7(d) for the changes in inertia and damping parameters of PCS-VSC2, the frequency change of PCS-VSC1, and the active power output waveform under grid frequency disturbance.

[0099] Figures 7(a) and 7(b) show that when the grid frequency fluctuates at 2.5s, PCS-VSC1 performs frequency modulation. When the inertia of PCS-VSC2 increases, the overshoot of the output frequency of PCS-VSC1 decreases, and the overshoot of the output power also decreases, but the maximum RoCoF does not change significantly, and the frequency response stabilization time is prolonged.

[0100] Figures 7(c) and 7(d) show that when the damping of PCS-VSC2 increases, the overshoot of PCS-VSC1 output frequency and output power decreases, the frequency response settling time is shortened, and the maximum RoCoF does not change significantly.

[0101] S105. Determine the control parameters of the energy storage converter based on the Bode diagram and the frequency response closed-loop transfer function, and perform multi-machine parallel control.

[0102] First, Bode plots can be used to observe the resonance characteristics of the parallel VSC energy storage system under different excitation sources. As the number of parallel connections increases, the probability of low-frequency resonance increases. This information is crucial for determining control parameters to suppress resonance and improve system stability.

[0103] Secondly, by utilizing the frequency response closed-loop transfer function, the impact of changes in control parameters (such as virtual inertia J and virtual damping D) on the frequency response characteristics of other energy storage VSCs can be analyzed. For example, when the inertia or damping parameters of one parallel energy storage VSC change, it will significantly affect the frequency response of other energy storage VSCs. By adjusting these control parameters, the system's frequency response characteristics can be optimized, such as reducing frequency overshoot and shortening settling time.

[0104] Specifically, when determining control parameters, factors such as system stability, frequency response speed, and accuracy are comprehensively considered. The system performance under different combinations of control parameters can be verified through simulation or experiments, and the optimal parameter combination can be selected for multi-machine parallel control.

[0105] Finally, when implementing multi-unit parallel control, it is necessary to ensure coordinated operation among the various energy storage VSCs. This can be achieved through advanced control strategies and algorithms, such as distributed control, centralized control, or hybrid control. These control strategies can be selected and optimized according to the actual situation and requirements of the system.

[0106] This application also provides a multi-unit parallel control device for energy storage converters, including:

[0107] The decomposition module decomposes the grid-connected system with parallel energy storage converters into multiple equivalent circuits under separate excitations;

[0108] The transfer module establishes the transfer function between the response current and the excitation source when each equivalent circuit acts alone.

[0109] The mapping module determines the Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters;

[0110] The closed-loop module determines the frequency response closed-loop transfer function of the i-th energy storage converter based on the transfer function between the response current and the excitation source and the power expression of the i-th energy storage converter to the common bus voltage.

[0111] The control module determines the control parameters of the energy storage converter based on the Bode plot and the frequency response closed-loop transfer function, and performs multi-unit parallel control.

[0112] This application also provides a multi-unit parallel control device for energy storage converters, including:

[0113] Memory;

[0114] The processor is configured to retrieve the computer-executable program of the above-described multi-unit parallel control method for energy storage converters from the memory, and execute the following steps: decomposing the grid-connected system of parallel energy storage converters into multiple equivalent circuits under individual excitation; establishing the transfer function between the response current and the excitation source when each equivalent circuit operates independently; determining the Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters; determining the frequency response closed-loop transfer function of the i-th energy storage converter based on the transfer function between the response current and the excitation source and the power expression of the i-th energy storage converter transferred to the common bus voltage; and determining the control parameters of the energy storage converter based on the Bode plot and the frequency response closed-loop transfer function, thereby performing multi-unit parallel control.

[0115] This application also provides a storage medium, comprising: storing a computer-executable program, the computer-executable program being invoked by a processor to execute the steps of the above-described energy storage converter multi-machine parallel control method.

Claims

1. A method for controlling multiple parallel operation of energy storage converters, characterized in that, include: Decomposing a grid-connected system with parallel energy storage converters into multiple equivalent circuits under individual excitation, including: converting the grid-connected system with multiple parallel energy storage converters into equivalent circuits under multiple individual voltage source excitations according to the voltage source form; Establish the transfer function between the response current and the excitation source when each of the equivalent circuits operates independently, including: acting alone Individual function and The transfer function under single action, where, , , These are the equivalent excitation sources for the first energy storage converter, the equivalent excitation sources for other energy storage converters, and the equivalent excitation source for the power grid, respectively. Determining the Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters includes: obtaining the Bode plot under different excitation sources based on the change of the transfer function as the number of parallel energy storage converters increases; Based on the transfer function between the response current and the excitation source and the power expression transferred from the i-th energy storage converter to the common bus voltage, the closed-loop transfer function of the frequency response of the i-th energy storage converter is determined, and the closed-loop transfer function is: ； ； ； in, Let be the deviation of the output angular frequency of the i-th energy storage converter. This refers to the change in load power in the power grid. For Laplace operator, representing the complex frequency domain, Let n be the rated angular frequency of the system, and n be the total number of units in the system. , Let be the virtual inertia of the i-th and m-th energy storage converters. , Let the virtual damping of the i-th energy storage converter be , , Let be the power transfer coefficient of the i-th energy storage converter. , Let be the equivalent admittance transfer function from the equivalent voltage source of the i-th and m-th converters to their output current; Based on the Bode plot and the frequency response closed-loop transfer function, the control parameters of the energy storage converter are determined, and multi-machine parallel control is performed, including: determining the control parameters by analyzing the influence of the changes in the inertia and damping parameters of each energy storage converter in the grid-connected system of parallel energy storage converters on the frequency response characteristics of other energy storage converters, wherein the control parameters include virtual inertia and virtual damping.

2. The multi-unit parallel control method for energy storage converters according to claim 1, characterized in that, Also includes: A simulation model of an energy storage converter was built using MATLAB / Simulink software.

3. A multi-unit parallel control device for energy storage converters, characterized in that, include: The decomposition module decomposes the grid-connected system of energy storage converters in parallel into multiple equivalent circuits under individual excitation, including: converting the grid-connected system of multiple energy storage converters in parallel into equivalent circuits under multiple individual voltage source excitations according to the voltage source form; The transfer module establishes the transfer function between the response current and the excitation source when each equivalent circuit operates independently, including: acting alone Individual function and The transfer function under single action, where, , , These are the equivalent excitation sources for the first energy storage converter, the equivalent excitation sources for other energy storage converters, and the equivalent excitation source for the power grid, respectively. The mapping module determines the Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters, including: obtaining the Bode plot under different excitation sources based on the change of the transfer function as the number of parallel energy storage converters increases; The closed-loop module determines the frequency response closed-loop transfer function of the i-th energy storage converter based on the transfer function between the response current and the excitation source and the power expression transferred from the i-th energy storage converter to the common bus voltage. The closed-loop transfer function is as follows: ； ； ； in, Let be the deviation of the output angular frequency of the i-th energy storage converter. This refers to the change in load power in the power grid. For Laplace operator, representing the complex frequency domain, Let n be the rated angular frequency of the system, and n be the total number of units in the system. , Let be the virtual inertia of the i-th and m-th energy storage converters. , Let the virtual damping of the i-th energy storage converter be , , Let be the power transfer coefficient of the i-th energy storage converter. , Let be the equivalent admittance transfer function from the equivalent voltage source of the i-th and m-th converters to their output current; The control module determines the control parameters of the energy storage converter based on the Bode plot and the frequency response closed-loop transfer function, and performs multi-machine parallel control, including: determining the control parameters by analyzing the influence of changes in the inertia and damping parameters of each energy storage converter in the grid-connected system of parallel energy storage converters on the frequency response characteristics of other energy storage converters, wherein the control parameters include virtual inertia and virtual damping.

4. A multi-unit parallel control device for energy storage converters, characterized in that, include: Memory; The processor is configured to retrieve, from the memory, the computer-executable program of the multi-unit parallel control method for energy storage converters according to any one of claims 1-2, and execute: decomposing the grid-connected system of parallel energy storage converters into multiple equivalent circuits under individual excitation, including: equipping the grid-connected system of parallel energy storage converters into equivalent circuits under multiple individual voltage source excitations according to the voltage source form; and establishing the transfer function between the response current and the excitation source for each equivalent circuit when it operates independently, including: acting alone Individual function and The transfer function under single action, where, , , The equivalent excitation sources for the first energy storage converter, the other energy storage converters, and the power grid are respectively considered. The Bode plot of the transfer function between the response current and the excitation source as a function of the number of parallel energy storage converters is determined, including: obtaining Bode plots under different excitation sources based on the change in the transfer function as the number of parallel energy storage converters increases; and determining the closed-loop transfer function of the frequency response of the i-th energy storage converter based on the transfer function between the response current and the excitation source and the power expression transferred from the i-th energy storage converter to the common bus voltage. The closed-loop transfer function is: ； ； ； in, Let be the deviation of the output angular frequency of the i-th energy storage converter. This refers to the change in load power in the power grid. For Laplace operator, representing the complex frequency domain, Let n be the rated angular frequency of the system, and n be the total number of units in the system. , Let be the virtual inertia of the i-th and m-th energy storage converters. , Let the virtual damping of the i-th energy storage converter be , , Let be the power transfer coefficient of the i-th energy storage converter. , The equivalent admittance transfer function is given from the equivalent voltage source of the i-th and m-th converters to their output current. The control parameters of the energy storage converters are determined based on the Bode plot and the frequency response closed-loop transfer function, and multi-machine parallel control is performed, including: determining the control parameters by analyzing the influence of the changes in the inertia and damping parameters of each energy storage converter in the grid-connected system of parallel energy storage converters on the frequency response characteristics of other energy storage converters. The control parameters include virtual inertia and virtual damping.

5. A storage medium, characterized in that, include: The device contains a computer-executable program that is invoked by a processor to perform the steps of the multi-machine parallel control method for energy storage converters as described in any one of claims 1 to 2.

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