Parameter design method of multi-machine grid-connected inverter interconnection system and computer medium

Abstract

The invention discloses a parameter design method of a multi-machine grid-connected inverter interconnection system and a computer medium. The method comprises the following steps: S1, obtaining a d-axis current inner loop control function and a voltage outer loop control function according to the structure of a single inverter; s2, completing parameter configuration of one inverter according to a first method; the first method comprises the steps of obtaining current inner loop and voltage outer loop control parameters according to a current inner loop control function and a voltage outer loop control function under the constraint of a preset bandwidth and a phase margin; s3, performing parameter configuration on an unconfigured inverter according to the first method in combination with the bandwidth difference constraint and the impedance adaptability constraint between the inverters; drawing a Nyquist curve; s4, judging whether the Nyquist curve surrounds the (-1, j0) point or not, and if not, judging that the parameter configuration of the inverter is completed; if yes, the inverter is judged to be an unconfigured inverter; after the judgment is finished, entering S3; and S5, completing the parameter design of the system after the configuration of the parameters of all inverters is completed.

Description

Technical Field

[0001] The present invention relates to the field of multi-machine grid-connected inverters, and particularly to a parameter design method and a computer medium for a multi-machine grid-connected inverter interconnection system. Background Art

[0002] With the continuous increase in the penetration rate of renewable energy in the power grid, distributed power supply systems with grid-connected inverters as the interface, relying on advantages such as high efficiency, fast response, and flexible control, are gradually increasing their application scope. However, due to the uncertainty and volatility of intermittent energy sources, the interaction between multiple inverters and between the multi-inverter system and the power grid is becoming increasingly complex, directly threatening the safe and stable operation of the power grid.

[0003] In a weak power grid, all inverters are coupled through the grid impedance, resulting in mutual influence between inverters and thus affecting the stability of the entire parallel system. At the same time, with the widespread connection of inverters, a series of harmonic oscillation and stability problems have emerged in distributed systems. Considering factors such as the grid-connected efficiency of inverters, the grid-connected capacity of new energy, and the cost of renewable energy utilization, distributed grid-connected inverters are usually connected in parallel in a series non-isolated structure. This connection method will cause the inverters to be coupled to form a complex high-order electrical network, which will further lead to the interaction of harmonic oscillations between inverters. Such harmonic oscillation phenomena will cause the problem of grid-connected instability of inverters. At the same time, due to factors such as long transmission distance and small short-circuit ratio in the medium- and low-voltage distribution systems in the power grid, the grid impedance is large, which makes the intermittent uncertainty of new energy power generation easily cause voltage fluctuations at the common connection point of inverters, seriously affecting the normal operation of inverters in the system. When multiple grid-connected inverters are interconnected and operated, it may even cause harmonic oscillations in the entire system. In existing research, some scholars have combined the active damping method with dead-zone control on the basis of establishing the Norton circuit of the parallel inverter system to solve the harmonic oscillation problem between multiple inverters. However, the effect of dead-zone control depends to a large extent on the accuracy of system modeling. But for the sake of simplifying the discussion, the parameters of each inverter are usually set the same, making this method have certain limitations.

[0004] Therefore, there is an urgent need for a new technical solution to solve the technical problem of how to improve the operation stability of a multi-machine grid-connected inverter interconnection system through the parameter design of inverters. Summary of the Invention

[0005] The present invention provides a parameter design method and a computer medium for a multi-machine grid-connected inverter interconnection system to solve the technical problem of how to improve the operation stability of a multi-machine grid-connected inverter interconnection system through the bandwidth design of inverters.

[0006] To achieve the above object, the present invention provides a parameter design method for a multi-machine grid-connected inverter interconnection system. The system includes a preset number of grid-following inverters with the same structure and a DC bus voltage control type. The method includes: S1. Obtain the current inner-loop control function and voltage outer-loop control function of the d-axis of the inverter according to the structure of a single inverter.

[0007] S2. Configure the parameters of any one inverter according to the first method; the first method includes obtaining the current inner-loop and voltage outer-loop control parameters according to the current inner-loop control function and voltage outer-loop control function under the constraints of a preset bandwidth and phase margin.

[0008] S3. Configure the parameters of any unconfigured inverter according to the first method in combination with the constraints of a preset bandwidth difference between inverters and impedance adaptability constraints; draw a generalized Nyquist curve according to the minimum loop gain matrix of the system at this time.

[0009] S4. Determine whether the generalized Nyquist curve encloses the point (-1, j0). If not, it is determined that the parameter configuration of this inverter is completed; if so, it is determined that this inverter is an unconfigured inverter and the parameters are cleared; after the determination is completed, enter S3.

[0010] S5. When the parameters of all inverters are configured, the parameter design of the multi-machine grid-connected inverter interconnection system is completed.

[0011] Preferably, the current inner-loop control function and voltage outer-loop control function of the d-axis of the inverter include: The current inner-loop control function includes the closed-loop transfer function of the current inner-loop : ; ; Among them, represents the open-loop transfer function of the current inner-loop; represents the transfer function of the d-axis current controller; the current inner-loop control parameters include and ; represents the proportional coefficient of the transfer function of the d-axis current controller; represents the integral coefficient of the transfer function of the d-axis current controller; represents the Laplace operator; represents the delay transfer function considering the controller delay; represents the transfer function of the main circuit LCL filter; The voltage outer-loop control function includes the closed-loop transfer function of the voltage outer-loop : ; ; Among them, represents the open-loop transfer function of the voltage outer loop; represents the transfer function of the d-axis voltage controller; the voltage outer loop control parameters include and , represents the proportional coefficient of the transfer function of the d-axis voltage controller; represents the integral coefficient of the transfer function of the d-axis voltage controller; represents the steady-state value of the d-axis of the point of common coupling (PCC) voltage; represents the steady-state value of the DC side output current.

[0012] Preferably, the preset bandwidth and phase margin constraints include: The bandwidth constraint includes: ; Among them, represents the cut-off frequency of the open-loop transfer function of the current inner loop ; represents the voltage outer loop bandwidth; represents the current inner loop bandwidth; represents the equivalent switching frequency; The phase margin constraint includes: When configuring the parameters of the inverter, there is a preset positive value for the phase margin of the current inner loop and the voltage outer loop.

[0013] Preferably, obtaining the current inner loop and voltage outer loop control parameters according to the current inner loop control function and the voltage outer loop control function includes: A1. Set a set of preset control parameters for the current inner loop control function and the voltage outer loop control function. The preset control parameters include , , and preset value combinations; A2. Plot the bode analysis curves of the current inner loop control function and the voltage outer loop control function, and obtain the first curve and the second curve respectively; obtain the angular frequencies at -3dB corresponding to the amplitudes of the first curve and the second curve, and obtain the actual values of the current inner loop bandwidth and the voltage outer loop bandwidth respectively; A3. Determine whether the actual values of the current inner loop bandwidth and the voltage outer loop bandwidth meet the preset bandwidth and phase margin constraints; if they meet, it means that the preset control parameters meet the requirements and are retained as the current inner loop and voltage outer loop control parameters; if they do not meet, it means that the preset control parameters do not meet the requirements, and the values of the preset control parameters are adjusted and then enter A2.

[0014] Preferably, the preset bandwidth difference constraint and impedance adaptability constraint between inverters include: The bandwidth difference constraint between inverters includes: ; Among them, represents the voltage outer-loop bandwidth of the nth inverter; represents the current inner-loop bandwidth of the nth inverter; the bandwidth difference constraint between inverters is to constrain that there is a preset difference between the voltage outer-loop bandwidth and the current inner-loop bandwidth of each inverter in the system; The impedance adaptability constraint includes: configuring parameters for the unconfigured inverters under the preset grid impedance.

[0015] Preferably, drawing the generalized Nyquist curve according to the minimum loop gain matrix of the system at this time includes: Assume that the sum of the configured inverters and the unconfigured inverters in the system, that is, the total number of inverters, is ; Select any one from the configured inverters in the system to obtain the equivalent output admittance matrix ; Obtain the equivalent output admittance matrices of all the remaining inverters in the system ; Obtain the grid impedance equivalent admittance matrix of the system according to the preset grid impedance ; According to , the equivalent output admittance matrices of all the remaining inverters and to obtain the minimum loop gain matrix , including: ; According to the minimum loop gain matrix the generalized Nyquist curve can be drawn.

[0016] The present invention also provides a computer medium, including a processor, a memory, and a computer program for implementing the method of the present invention.

[0017] The present invention has the following beneficial effects: The parameter design method of the multi-inverter grid-connected inverter interconnection system of the present invention first obtains the current inner-loop control function and voltage outer-loop control function of the d-axis of the inverter according to the structure of a single inverter, providing a basis for the subsequent configuration of the inverter. The current inner-loop and voltage outer-loop control parameters are obtained through the current inner-loop control function and voltage outer-loop control function, and the initial inverter is configured according to the control parameters, providing a basis for the configuration of other subsequent inverters; at the same time, the preset bandwidth and phase margin constraints are considered when configuring the initial inverter, enabling the configured inverter to operate normally. On the basis of the configuration of the initial inverter, further considering the preset bandwidth difference and impedance adaptability constraints between inverters, the unconfigured inverters are configured one by one and verified as a whole, and the effective configuration of all inverter parameters in the system is completed step by step, so that the method of the present invention improves the operation stability of the multi-inverter grid-connected inverter interconnection system through the parameter design of the inverter. The method of the present invention improves the operation stability of the multi-inverter grid-connected inverter interconnection system by configuring the original inverter parameters in the system, without the need to add an auxiliary control loop, thereby avoiding the problem of increased cost, and at the same time reducing the cumbersome design process of additionally changing the inverter control structure and simplifying the system stability improvement process.

[0018] In addition to the purposes, features and advantages described above, the present invention has other purposes, features and advantages. The following will refer to the accompanying drawings and make a further detailed description of the present invention. Brief Description of the Drawings

[0019] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is a schematic diagram of the structure and control of a DC bus voltage-controlled grid-following inverter according to a preferred embodiment of the present invention.

[0020] Figure 2 It is a schematic diagram of a multi-inverter grid-connected inverter interconnection system according to a preferred embodiment of the present invention.

[0021] Figure 3 It is a schematic diagram of the method flow according to a preferred embodiment of the present invention.

[0022] Figure 4 It is a schematic diagram of the generalized Nyquist curve of the system when the grid impedance is 7.5 mH according to a preferred embodiment of the present invention.

[0023] Figure 5 It is a schematic diagram of the generalized Nyquist curve of the system when the grid impedance is 8.5 mH according to a preferred embodiment of the present invention.

[0024] Figure 6It is a schematic diagram of the output waveform of the system when the grid impedance is 7.5mH according to the preferred embodiment of the present invention.

[0025] Figure 7 It is a schematic diagram of the output waveform of the system when the grid impedance is 8.5mH in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0027] See also Figure 1 The DC bus voltage controlled grid-following inverter of the present invention comprises: a DC bus capacitor , three-phase inverter, inductor and ,capacitance and series damping resistor ;in , and Construct an LCL filter.

[0028] See also Figure 1 In the DC bus voltage controlled grid-following inverter of the present invention, from left to right, the DC power supply Through the DC bus capacitor Maintain the DC voltage of the inverter stable, and then transmit it to the AC circuit through the three-phase inverter to form a three-phase AC voltage The harmonics generated by the inverter are filtered out through the LCL filter circuit to obtain high-quality grid-connected current, which is finally connected to the grid through the public grid connection point.

[0029] See also Figure 1 The control principle of the DC bus voltage control type grid-following inverter of the present invention includes: in order to maintain the DC bus capacitor Voltage stability, extract its voltage Used to control the circuit as feedback real signal for control, and After the difference is made, it passes through the voltage controller Get the d-axis current reference value and make a difference with the real value of the d-axis current extraction The inverter d-axis voltage modulation signal is obtained after the current controller is controlled ;q-axis current reference value The difference between the actual value of the q-axis current extraction and the The inverter q-axis voltage modulation signal is obtained after the current controller is controlled ; Finally, the PWM modulation method is used to control the three-phase inverter based on the voltage modulation signal to realize the inverter operation.

[0030] In Figure 1 , and respectively represent the DC - side capacitor voltage and the output current; represents the output current on the inverter side; represents the grid - side current; represents the voltage at the point of common coupling (PCC); represents the grid impedance; represents the equivalent voltage source of the grid; represents the output phase angle of the phase - locked loop (PLL); represents the voltage reference signal; and respectively represent the d - axis and q - axis reference signals of the current ; is the modulation gain; and represent the voltage modulation signal; represents the DC - power supply current; represents the voltage at the output port of the inverter; and represent the actual value of the inverter output current; PCC represents the point of common coupling of the inverter; abc / dq represents the dq transformation; dq / abc represents the inverse dq transformation.

[0031] In the multi - machine grid - connected inverter interconnection system of the present invention, the inverters are connected in parallel with each other. For the structural schematic diagram of the system, see Figure 2 .

[0032] See Figure 3 . In the preferred embodiment of the present invention, a parameter design method for a multi - machine grid - connected inverter interconnection system is provided. The system includes a preset number of grid - following inverters with the same structure and a DC - bus voltage control type. The method includes: S1. Obtain the current inner - loop control function and voltage outer - loop control function of the d - axis of the inverter according to the structure of a single inverter.

[0033] In the preferred embodiment S1 of the present invention, the current inner - loop control function and voltage outer - loop control function of the d - axis of the inverter include: The current inner - loop control function includes the closed - loop transfer function of the current inner - loop : ; ; Wherein, represents the open - loop transfer function of the current inner - loop; represents the transfer function of the d - axis current controller; The current inner - loop control parameters include and , represents the proportional coefficient of the transfer function of the d-axis current controller; represents the integral coefficient of the transfer function of the d-axis current controller; represents the Laplace operator; represents the delay transfer function considering the controller delay; represents the transfer function of the main circuit LCL filter; The voltage outer loop control function includes the closed-loop transfer function of the voltage outer loop : ; ; wherein, represents the open-loop transfer function of the voltage outer loop; represents the transfer function of the d-axis voltage controller; the voltage outer loop control parameters include and , represents the proportional coefficient of the transfer function of the d-axis voltage controller; represents the integral coefficient of the transfer function of the d-axis voltage controller; represents the steady-state value of the d-axis of the grid connection point PCC voltage; represents the steady-state value of the DC side output current.

[0034] S2. Complete the parameter configuration of any inverter according to the first method; the first method includes obtaining the current inner loop and voltage outer loop control parameters according to the current inner loop control function and the voltage outer loop control function under the constraints of a preset bandwidth and phase margin.

[0035] In S2 of the preferred embodiment of the present invention, the preset bandwidth and phase margin constraints include: The bandwidth constraint includes: ; wherein, represents the cut-off frequency of the open-loop transfer function of the current inner loop ; represents the voltage outer loop bandwidth; represents the current inner loop bandwidth; represents the equivalent switching frequency; The phase margin constraint includes: When configuring the parameters of the inverter, there is a preset positive value for the phase margin of the current inner loop and the voltage outer loop.

[0036] In S2 of the preferred embodiment of the present invention, obtaining the current inner loop and voltage outer loop control parameters according to the current inner loop control function and the voltage outer loop control function includes: A1. Set a group of preset control parameters for the current inner loop control function and the voltage outer loop control function, and the preset control parameters include , , and preset value combinations; A2. Draw the bode analysis curves of the current inner loop control function and the voltage outer loop control function to obtain the first curve and the second curve respectively; obtain the angular frequencies at -3dB corresponding to the amplitudes of the first curve and the second curve to obtain the actual values of the current inner loop bandwidth and the voltage outer loop bandwidth respectively; A3. Determine whether the actual values of the current inner loop bandwidth and the voltage outer loop bandwidth meet the preset bandwidth and phase margin constraints; if they meet, it means that the preset control parameters meet the requirements and are retained as the current inner loop and voltage outer loop control parameters; if they do not meet, it means that the preset control parameters do not meet the requirements, and the values of the preset control parameters are adjusted and then enter A2.

[0037] S3. Configure the parameters of any unconfigured inverter according to the first method in combination with the preset bandwidth difference constraint and impedance adaptability constraint between inverters; draw the generalized Nyquist curve according to the minimum loop gain matrix of the system at this time.

[0038] In S3 of the preferred embodiment of the present invention, the preset bandwidth difference constraint and impedance adaptability constraint between inverters include: The bandwidth difference constraint between inverters includes: ; wherein, represents the voltage outer loop bandwidth of the nth inverter; represents the current inner loop bandwidth of the nth inverter; the bandwidth difference constraint between inverters is to constrain that there is a preset difference between the voltage outer loop bandwidth and the current inner loop bandwidth of each inverter in the system; The impedance adaptability constraint includes: configuring the parameters of the unconfigured inverter under the preset grid impedance.

[0039] In S3 of the preferred embodiment of the present invention, drawing the generalized Nyquist curve according to the minimum loop gain matrix of the system at this time includes: Assume that the sum of the configured inverters and the unconfigured inverters in the system, that is, the total number of inverters, is ; Select any one from the configured inverters in the system to obtain the equivalent output admittance matrix ; obtain the equivalent output admittance matrices of the remaining all inverters in the system ; Obtain the grid impedance equivalent admittance matrix of the system according to the preset grid impedance; According to , the remaining all Equivalent output admittance matrix of an inverter and obtain the minimum loop gain matrix , including: ; According to the minimum loop gain matrix the generalized Nyquist curve can be drawn.

[0040] S4. Determine whether the generalized Nyquist curve encloses the point (-1, j0). If not, it is determined that the parameter configuration of this inverter is completed; if so, it is determined that this inverter is an unconfigured inverter and the parameters are cleared; after the determination, enter S3.

[0041] S5. When the parameters of all inverters are configured, the parameter design of the multi-inverter parallel-connected inverter interconnection system is completed.

[0042] For the parameter design method of the multi-inverter parallel-connected inverter interconnection system of the present invention, first, the current inner-loop control function and voltage outer-loop control function of the d-axis of the inverter are obtained according to the structure of a single inverter, providing a basis for the subsequent configuration of the inverter. The current inner-loop and voltage outer-loop control parameters are obtained through the current inner-loop control function and voltage outer-loop control function, and the initial inverter is configured according to the control parameters, providing a basis for the subsequent configuration of other inverters; at the same time, the preset bandwidth and phase margin constraints are considered when configuring the initial inverter, so that the configured inverter can operate normally. On the basis of the configuration of the initial inverter, further considering the preset bandwidth difference and impedance adaptability constraints between inverters, the unconfigured inverters are configured one by one and verified as a whole, and the effective configuration of all inverter parameters in the system is completed step by step, so that the method of the present invention improves the operation stability of the multi-inverter parallel-connected inverter interconnection system through the parameter design of the inverter. The method of the present invention improves the operation stability of the multi-inverter parallel-connected inverter interconnection system by configuring the original inverter parameters in the system, without adding an auxiliary control loop, thereby avoiding the problem of increased cost, and at the same time reducing the cumbersome design process of additionally changing the inverter control structure and simplifying the system stability improvement process.

[0043] In a preferred embodiment of the present invention, a computer medium is further provided, including a processor, a memory, and a computer program for implementing the method of the present invention.

[0044] Verification part: In a preferred embodiment of the present invention, a set of two DC bus voltage-controlled grid-following inverter interconnection systems is built in MATLAB / Simulink, and the simulation parameters are shown in Table 1: Table 1 Simulation parameters ; To verify the effectiveness of the method of the present inventionFigures 4 to 5 The generalized Nyquist analysis results of completing parameter setting by using the method of the present invention finally are given. Figures 6 to 7 The operation simulation results of the multi-inverter system under different grid impedances are given.

[0045] In Figures 4 to 5 the blue curve represents the generalized Nyquist curve with an eigenvalue of 1; the purple curve represents the generalized Nyquist curve with an eigenvalue of 2; the red curve represents the unit circle for finding the point (-1, j0).

[0046] Figure 4 The drawing results of the generalized Nyquist criterion of the multi-inverter system when the grid impedance is set to 7.5 mH are shown. At this time, the generalized Nyquist curve does not enclose the point (-1, j0), and the system output wave remains stable.

[0047] Figure 5 The drawing results of the generalized Nyquist criterion of the multi-inverter system when the grid impedance is set to 8.5 mH are shown. At this time, the generalized Nyquist curve encloses the point (-1, j0), and the system output wave becomes unstable. In this simulation, 7.5 mH is set as the impedance adaptation target of the multi-inverter system. The method of the present invention can effectively set the parameters of each inverter in the system, and realize the effective determination of the generalized Nyquist criterion for the target-adapted grid impedance of 7.5 mH.

[0048] See Figure 6 , when the system parameters designed by using the method of the present invention are adopted, the system output waveform remains stable when the grid impedance reaches 7.5 m; see Figure 7 when the grid impedance increases to 8.5 mH, the system loses stability, which successfully verifies the effectiveness of the parameter design of the present invention. Figures 6 to 7 In , and respectively represent the phase a, phase b and phase c currents of the inverters configured this time.

[0049] The above analysis results verify the correctness and effectiveness of the method of the present invention, can effectively optimize the control bandwidth of each inverter in the multi-inverter system, and provide direct theoretical guidance for the safe and stable operation of the power grid.

[0050] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A parameter design method for a multi-machine grid-connected inverter interconnection system, the system includes a preset number of grid-following inverters with the same structure of DC bus voltage control, characterized in that, The method includes: S1. Obtain the current inner-loop control function and voltage outer-loop control function of the d-axis of the inverter according to the structure of a single inverter; S2. Complete the parameter configuration of any inverter according to the first method; the first method includes obtaining the current inner-loop and voltage outer-loop control parameters according to the current inner-loop control function and voltage outer-loop control function under the constraints of a preset bandwidth and phase margin; S3. Configure the parameters of any unconfigured inverter according to the first method in combination with the preset bandwidth difference constraint and impedance adaptability constraint between inverters; draw the generalized Nyquist curve according to the minimum loop gain matrix of the system at this time; S4. Determine whether the generalized Nyquist curve encloses the point (-1, j0). If not, it is determined that the parameter configuration of this inverter is completed; if so, it is determined that this inverter is an unconfigured inverter and the parameters are cleared; after the determination, enter S3; S5. When the parameters of all inverters are configured, the parameter design of the multi-inverter parallel-connected inverter interconnection system is completed.

2. The parameter design method for the multi-machine grid-connected inverter interconnection system according to claim 1, characterized in that, The current inner-loop control function and voltage outer-loop control function of the d-axis of the inverter include: The current inner loop control function includes the closed-loop transfer function of the current inner loop : ； ； Among them, represents the open-loop transfer function of the current inner loop; represents the transfer function of the d-axis current controller; the control parameters of the current inner loop include and , represents the proportional coefficient of the transfer function of the d-axis current controller; represents the integral coefficient of the transfer function of the d-axis current controller; represents the Laplace operator; represents the delay transfer function considering the controller delay; represents the transfer function of the main circuit LCL filter; The voltage outer loop control function includes the closed-loop transfer function of the voltage outer loop : ； ； Among them, represents the open-loop transfer function of the voltage outer loop; represents the transfer function of the d-axis voltage controller; the voltage outer loop control parameters include and , represents the proportional coefficient of the transfer function of the d-axis voltage controller; represents the integral coefficient of the transfer function of the d-axis voltage controller; represents the steady-state value of the d-axis of the point of common coupling (PCC) voltage; represents the steady-state value of the DC side output current.

3. The parameter design method for the multi-machine grid-connected inverter interconnection system according to claim 2, characterized in that, The preset bandwidth and phase margin constraints include: The bandwidth constraint includes: ； Among them, represents the cut-off frequency of the open-loop transfer function of the inner current loop ; represents the bandwidth of the outer voltage loop; represents the bandwidth of the inner current loop; represents the equivalent switching frequency; The phase margin constraint includes: When configuring the parameters of the inverter, there is a preset positive value for the phase margin of the current inner-loop and voltage outer-loop.

4. The parameter design method for the multi-machine grid-connected inverter interconnection system according to claim 3, characterized in that, Obtaining the current inner-loop and voltage outer-loop control parameters according to the current inner-loop control function and voltage outer-loop control function includes: A1. Set a set of preset control parameters for the current inner-loop control function and the voltage outer-loop control function, where the preset control parameters include , , and of preset value combinations; A2. Draw the bode analysis curves of the current inner-loop control function and voltage outer-loop control function, and obtain the first curve and the second curve respectively; obtain the angular frequencies at -3dB corresponding to the amplitudes of the first curve and the second curve, and obtain the actual values of the current inner-loop bandwidth and voltage outer-loop bandwidth respectively; A3. Determine whether the actual values of the current inner-loop bandwidth and voltage outer-loop bandwidth meet the preset bandwidth and phase margin constraints; if they meet, it means that the preset control parameters meet the requirements and are reserved as the current inner-loop and voltage outer-loop control parameters; if they do not meet, it means that the preset control parameters do not meet the requirements, and after adjusting the values of the preset control parameters, enter A2.

5. The parameter design method for the multi-machine grid-connected inverter interconnection system according to claim 4, characterized in that, The preset bandwidth difference constraint and impedance adaptability constraint between inverters include: The bandwidth difference constraint between inverters includes: ； Among them, represents the voltage outer-loop bandwidth of the nth inverter; represents the current inner-loop bandwidth of the nth inverter; the bandwidth difference constraint between inverters means that the voltage outer-loop bandwidth and the current inner-loop bandwidth of each inverter in the system need to be constrained to have a preset difference; The impedance adaptability constraint includes: configuring the parameters of the unconfigured inverter under the preset grid impedance.

6. The parameter design method of the multi-machine grid-connected inverter interconnection system according to claim 5, wherein, Drawing the generalized Nyquist curve according to the minimum loop gain matrix of the system at this time includes: Suppose the sum of the inverters with parameter configuration and those without configuration in the said system, i.e., the total number of inverters, is ; Select any one of the inverters with parameter configuration completed within the system to obtain the equivalent output admittance matrix ; Obtain all the remaining equivalent output admittance matrices of the inverters ; Obtain the equivalent admittance matrix of the power grid impedance of the system according to the preset power grid impedance ; According to , all the remaining equivalent output admittance matrix of the inverters and obtain the minimum loop gain matrix , including: ； According to the minimum loop gain matrix the generalized Nyquist curve can be plotted.

7. A computer medium, wherein, Including a processor, a memory, and a computer program for implementing the method according to any one of claims 1 to 6 above.

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