Design and parameter setting method for active power controller of network-forming converter

Abstract

The invention relates to a design and parameter setting method for an active power controller of a network construction type converter. The method comprises the following steps: determining performance index requirements of the active power controller of the network construction type converter; according to performance index requirements and an automatic control principle, a mathematical model of an active power loop of a grid-connected inverter is used as a to-be-corrected object, proper rotational inertia and damping coefficient are selected to calculate steady-state gain, and then a controller is designed; according to a Bode diagram of a system open-loop transfer function after the controller is added, verifying whether the controller meets performance index requirements or not; the controller is corrected, a system open-loop transfer function at the moment is regarded as a new object to be corrected, and a correction network is designed according to frequency domain characteristics of the new object to be corrected; and correcting the new to-be-corrected object by adopting the correction network to obtain the final active power controller of the network construction type converter. According to the method, the active power controller meeting the performance index requirements is efficiently designed, and a theoretical basis is provided for the design of a control loop of a network-forming converter.

Description

Technical Field

[0001] The invention relates to a design of an active power controller of a grid-type converter and a parameter setting method, and belongs to the technical field of new energy and intelligent microgrids. Background Art

[0002] With the large-scale grid connection of new energy, the proportion of power electronic equipment in the power system has increased significantly, which has led to a gradual decrease in grid inertia, which in turn has an adverse effect on the voltage and frequency stability of the grid. In this context, the traditional grid-following inverter control strategy cannot provide system inertia and is difficult to cope with the challenges brought by the stable grid connection of large-scale new energy. The grid-building control strategy can provide inertia and damping characteristics for the system, which is conducive to improving the stability and adaptability of the grid. Therefore, various grid-building control strategies have emerged, including droop control and virtual synchronous generator (VSG) control. These control strategies aim to enhance the regulation capability of the grid by simulating the dynamic characteristics of traditional generators. For example, droop control adjusts the relationship between the output power of the inverter and the grid frequency so that it can adaptively respond to changes in the grid frequency; while VSG control enhances the frequency and voltage regulation capability of the grid by introducing inertia and damping characteristics similar to synchronous generators in the inverter.

[0003] In the above control strategy, the controller, as its core component, determines the performance of the overall system. Therefore, the design of the active power controller plays a vital role. Through the controller design, the grid-connected converter can flexibly provide inertia and damping for the grid, effectively cope with frequency fluctuations and load changes in the grid, and thus provide support for the reliable operation of the grid under the condition of high proportion of new energy grid connection.

[0004] The currently disclosed technical solutions for the design of grid-connected converter controllers mainly rely on empirical trial and error and test verification methods to adjust controller parameters, and lack theoretical basis. The design method of its active power controller is as follows. First, observe the grid-connected open-loop gain Bode diagram and the step response diagram of the off-grid open-loop transfer function corresponding to each set of controller parameters to evaluate its performance. The applicability of the set of controller parameters is judged by analyzing the slope and phase margin at the cutoff frequency in the Bode diagram. If it is found that the actual parameter indicators do not match the expected parameter indicators, they need to be adjusted according to the analysis results. For example, when the slope and phase margin at the cutoff frequency are both lower than the standard value, a negative zero point can be introduced to improve the system performance by using its phase lead effect; if the step change of load power causes a sharp fluctuation in frequency, a negative pole can be introduced to reduce the system's sensitivity to the step response.

[0005] The currently disclosed technical solutions usually adopt the trial and error method to design the controller. Although it can meet the needs to a certain extent, the process is cumbersome, the workload is large, and it takes a long time. It often requires repeated adjustment and optimization of parameters, and it is difficult to quickly obtain the ideal control effect. Therefore, the present invention proposes a systematic design method for the active power controller of the grid-type converter. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a systematic active power controller design and parameter setting method for a grid-type converter, which can efficiently design an active power controller that meets the performance index requirements and provide a theoretical basis for the control loop design of the grid-type converter.

[0007] The technical solution adopted by the present invention to solve the technical problem is:

[0008] An embodiment of the present invention provides a method for designing and setting parameters of a grid-connected converter active power controller, comprising the following steps:

[0009] Step S1, determining the performance index requirements of the active power controller of the grid-connected converter;

[0010] Step S2, according to the performance index requirements and the automatic control principle, the mathematical model of the active power loop of the grid-connected inverter is used as the object to be corrected G, the appropriate moment of inertia J and damping coefficient D are selected, and the steady-state gain K is calculated, and then the controller G1 is designed;

[0011] Step S3, verifying whether the controller G1 meets the performance index requirements according to the Bode diagram of the system open-loop transfer function G0 after the controller G1 is added at this time;

[0012] Step S4, modifying the controller G1, treating the open-loop transfer function G0 as a new object to be corrected, and designing the correction network G2 according to the frequency domain characteristics of the open-loop transfer function G0; the frequency domain characteristics include the cutoff frequency and the phase margin;

[0013] Step S5, using the correction network G2 to correct the object to be corrected G0, to obtain the final grid-connected converter active power controller Gcontrol = G1*G2.

[0014] As a possible implementation method of this embodiment, the performance indicator requirements include: the dynamic response characteristics of active power satisfy the overshoot less than or equal to 30%, the system adjustment time less than or equal to 0.5s (error band is 2%), and the steady-state error at unit ramp input is 2%.

[0015] As a possible implementation of this embodiment, the performance indicators include steady-state error, overshoot and adjustment time;

[0016] The steady-state error e ss (∞) is 2%. For a second-order system, the overshoot calculation method is: The adjustment time t s The calculation method is Where ζ is the damping ratio, ω n is the undamped natural oscillation frequency, and the error band of the adjustment time is 2%.

[0017] As a possible implementation of this embodiment, the frequency domain characteristics corresponding to the performance index requirement can be calculated based on the damping ratio and the natural oscillation frequency. For a second-order system, the cutoff frequency ω c The calculation method is The calculation method of phase margin γ is: Among them, ω n is the undamped natural oscillation frequency, and ζ is the damping ratio.

[0018] As a possible implementation of this embodiment, the mathematical model of the active power loop of the grid-connected inverter is:

[0019]

[0020] Where s is the Laplace operator, is the maximum active power.

[0021] As a possible implementation of this embodiment, according to the performance index requirements and the automatic control principle, the mathematical model of the active power loop of the grid-connected inverter is used as the object to be corrected G, the appropriate moment of inertia J and damping coefficient D are selected, and the steady-state gain K is calculated, and then the controller G1 is designed, including:

[0022] Comprehensively consider the dynamic performance and stability requirements of the system, select appropriate inertia and damping coefficient, and adjust the inertia J appropriately to improve the system's anti-disturbance ability while maintaining a good balance between response speed and frequency stability; a reasonably designed damping coefficient D can achieve an optimal balance between response speed and system stability;

[0023] Using the steady-state error e ss (∞) and static velocity error coefficient k v Find the steady-state gain K:

[0024] e ss (∞)=2%

[0025]

[0026] Finalizing the controller design.

[0027] As a possible implementation of this embodiment, the design of the correction network G2 according to the frequency domain characteristics of the open-loop transfer function G0 includes:

[0028] When the cut-off frequency and phase margin are both less than the performance index requirements, an advance correction network is designed to increase the cut-off frequency and phase margin;

[0029] When the cut-off frequency is less than the performance index requirement and the phase margin is greater than the performance index requirement, a hysteresis correction network is designed to increase the cut-off frequency while maintaining system stability;

[0030] When the cutoff frequency is greater than the performance index requirement and the phase margin is less than the performance index requirement, an advance correction network is designed to improve the phase margin and adjust the cutoff frequency at the same time;

[0031] When the cut-off frequency and phase margin are both greater than the performance index requirements, a lag-lead correction network is designed to balance the response speed and stability of the system.

[0032] The beneficial effects of the technical solution of the embodiment of the present invention are as follows:

[0033] The present invention uses correction technology and frequency domain analysis methods and other theoretical calculation methods to design the controller. By analyzing the frequency domain characteristics of the object to be corrected, simulating the moment of inertia and damping characteristics of the synchronous generator, and combining the performance index requirements of the system, the structural form of the controller is determined and the parameters are adjusted, ensuring that the controller design can meet the expected performance index requirements, such as adjustment time, overshoot, etc. Compared with the traditional trial and error method, the design method of the present invention is more efficient and can quickly and directly calculate a controller that meets the performance index requirements, greatly shortening the design cycle.

[0034] The present invention uses theoretical calculation means such as correction technology and frequency domain analysis method to design the controller, combines theoretical calculation with practical application needs, and efficiently designs an active power controller that meets the performance index requirements. It provides a systematic and theoretical design process and calculation tools for the control loop of the grid-type converter, and provides a theoretical basis for the design of the control loop of the grid-type converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of a design and parameter setting method of an active power controller of a grid-connected converter according to an exemplary embodiment;

[0036] Figure 2 It is a schematic diagram of a small signal simplified model of an active power loop in the prior art;

[0037] Figure 3 is a topology diagram of a grid-connected inverter according to an exemplary embodiment;

[0038] Figure 4 is a power control block diagram of a grid-connected converter according to an exemplary embodiment;

[0039] Figure 5 is a block diagram of virtual admittance and current control of a grid-connected converter according to an exemplary embodiment;

[0040] Figure 6 is an equivalent model diagram of an inverter grid-connected according to an exemplary embodiment;

[0041] Figure 7 is a simplified model diagram of an active loop small signal according to an exemplary embodiment;

[0042] Figure 8 is a Bode diagram of an active branch object G(s) to be corrected according to an exemplary embodiment;

[0043] Fig. 9 is a Bode diagram of a system open-loop transfer function G0(s) according to an exemplary embodiment;

[0044] Fig.10 is a Bode diagram of a system open-loop transfer function according to an exemplary embodiment;

[0045] Fig.11 is a closed-loop transfer function step response diagram according to an exemplary embodiment;

[0046] Fig.12 is a global diagram of an active power simulation result shown according to an exemplary embodiment;

[0047] Fig.13 is a partial diagram showing an active power simulation result according to an exemplary embodiment. DETAILED DESCRIPTION

[0048] In order to more clearly illustrate the technical features of the solution of the present invention, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0049] This paper proposes a systematic controller design method for the active power loop of the grid-connected inverter. First, the mathematical model of the active power loop of the grid-connected inverter is taken as the object to be corrected. In order to reduce the cutoff frequency and simulate the rotational inertia and damping characteristics of the synchronous generator, a controller is designed. Then, according to the frequency domain characteristics of the system open-loop transfer function after adding the controller, the appropriate correction network is selected and the relevant parameters of the correction network are calculated to finally complete the design of the controller.

[0050] like Figure 1As shown, a grid-connected converter active power controller design and parameter setting method provided by an embodiment of the present invention includes the following steps:

[0051] Step S1, determining the performance index requirements of the active power controller of the grid-connected converter;

[0052] Step S2, according to the performance index requirements and the automatic control principle, the mathematical model of the active power loop of the grid-connected inverter is used as the object to be corrected G, the appropriate moment of inertia J and damping coefficient D are selected, and the steady-state gain K is calculated, and then the controller G1 is designed;

[0053] Step S3, verifying whether the controller G1 meets the performance index requirements according to the Bode diagram of the system open-loop transfer function G0 after the controller G1 is added at this time;

[0054] Step S4, modifying the controller G1, treating the open-loop transfer function G0 as a new object to be corrected, and designing the correction network G2 according to the frequency domain characteristics of the open-loop transfer function G0; the frequency domain characteristics include the cutoff frequency and the phase margin;

[0055] Step S5, using the correction network G2 to correct the object to be corrected G0, to obtain the final grid-connected converter active power controller Gcontrol = G1*G2.

[0056] As a possible implementation method of this embodiment, the performance indicator requirements include: the dynamic response characteristics of active power satisfy the overshoot less than or equal to 30%, the system adjustment time less than or equal to 0.5s (error band is 2%), and the steady-state error at unit ramp input is 2%.

[0057] As a possible implementation of this embodiment, the performance indicators include steady-state error, overshoot and adjustment time;

[0058] The steady-state error e ss (∞) is 2%. For a second-order system, the overshoot calculation method is: The adjustment time t s The calculation method is Where ζ is the damping ratio, ω n is the undamped natural oscillation frequency, and the error band of the adjustment time is 2%.

[0059] As a possible implementation of this embodiment, the frequency domain characteristics corresponding to the performance index requirement can be calculated based on the damping ratio and the natural oscillation frequency. For a second-order system, the cutoff frequency ω c The calculation method is The calculation method of phase margin γ is: Among them, ω nis the undamped natural oscillation frequency, and ζ is the damping ratio.

[0060] As a possible implementation of this embodiment, the mathematical model of the active power loop of the grid-connected inverter is:

[0061]

[0062] Where s is the Laplace operator, is the maximum active power.

[0063] As a possible implementation of this embodiment, according to the performance index requirements and the automatic control principle, the mathematical model of the active power loop of the grid-connected inverter is used as the object to be corrected G, the appropriate moment of inertia J and damping coefficient D are selected, and the steady-state gain K is calculated, and then the controller G1 is designed, including:

[0064] Comprehensively consider the dynamic performance and stability requirements of the system, select appropriate inertia and damping coefficient, and adjust the inertia J appropriately to improve the system's anti-disturbance ability while maintaining a good balance between response speed and frequency stability; a reasonably designed damping coefficient D can achieve an optimal balance between response speed and system stability;

[0065] Using the steady-state error e ss (∞) and static velocity error coefficient k v Find the steady-state gain K:

[0066] e ss (∞)=2%

[0067]

[0068] Finalizing the controller design.

[0069] As a possible implementation of this embodiment, the design of the correction network G2 according to the frequency domain characteristics of the open-loop transfer function G0 includes:

[0070] When the cut-off frequency and phase margin are both less than the performance index requirements, an advance correction network is designed to increase the cut-off frequency and phase margin;

[0071] When the cut-off frequency is less than the performance index requirement and the phase margin is greater than the performance index requirement, a hysteresis correction network is designed to increase the cut-off frequency while maintaining system stability;

[0072] When the cutoff frequency is greater than the performance index requirement and the phase margin is less than the performance index requirement, an advance correction network is designed to improve the phase margin and adjust the cutoff frequency at the same time;

[0073] When the cut-off frequency and phase margin are both greater than the performance index requirements, a lag-lead correction network is designed to balance the response speed and stability of the system.

[0074] The present invention uses correction technology and frequency domain analysis methods and other theoretical calculation methods to design the controller. First, the active power loop of the inverter grid-connected is mathematically modeled, and its model is used as the object to be corrected. Through the selection of the controller form and the theoretical design of parameters, the external characteristics of the synchronous generator are simulated to provide inertia and damping for the power grid. Then, based on the frequency domain characteristics of the open-loop transfer function of the system after adding the controller, such as the cut-off frequency and phase margin, the correction network is designed and the parameters are calculated. The present invention combines theoretical calculations with practical application needs, efficiently designs an active power controller that meets the performance index requirements, and provides a systematic and theoretical design process and calculation tools for the control loop of the grid-connected converter.

[0075] Figure 2 is a schematic diagram of a small signal simplified model of an active power circuit in the prior art; in the generalized droop control, the small signal simplified model of the active power circuit is as follows Figure 2 The grid-connected open-loop gain is shown in equation (1), and the off-grid open-loop transfer function is shown in equation (2).

[0076] T loop =G control ·G·H CPF (1)

[0077]

[0078] In view of the current situation that active power controllers of grid-connected converters lack a systematic design method, a comprehensive and detailed active power controller design process of the present invention is as follows.

[0079] Figure 3 This is the topology diagram of the inverter grid-connected circuit. The circuit includes a filter inductor L f1 , L f2 , filter capacitor C f , line impedance Z line , load Z load ; Three-phase full-bridge power switch S a , S b , S c And its corresponding lower bridge arm switch The upper and lower switches of the same bridge arm work in complementary mode. The direction of current flowing from the inverter into the grid is defined as the positive direction, denoted by i a ,i b ,i c The grid voltage is e a ,e b ,e c , the DC side voltage is Vdc .

[0080] Figure 4 and Figure 5 They are the power control diagram and virtual admittance and current control diagram of the grid-connected converter. The specific control process is as follows: the phase angle θ is obtained through the active-frequency control loop, the reference amplitude E of the inverter output voltage is obtained through the reactive-voltage control loop, and the voltage amplitude and phase angle are synthesized into a voltage vector E∠θ through the coordinate transformation module. Then, the voltage vector E∠θ is combined with the grid voltage v measured at the grid connection point. PCC The virtual admittance module outputs the inductance L f2 Current reference value In the dq coordinate system, the d and q axis components of the inverter output voltage are output respectively through the current controller (PI controller) d 、e q . d 、e q Transformed to the natural coordinate system, the output three-phase modulation wave v a 、v b 、v c , and the modulation signal of the inverter switch tube is output through the SPWM modulation module.

[0081] Figure 6 This is an inverter grid-connected equivalent model of a grid-connected converter active power controller design method of the present invention. The output voltage on the inverter side is equivalent to For the convenience of calculation, the grid side phase angle is selected as 0°, then the grid side voltage is equivalent to V∠0°, and the inverter output impedance is Z∠θ. Figure 6 Calculate the maximum active power. The complex power S on the bus can be expressed as:

[0082] S=P+jQ (3)

[0083] Among them, P and Q are active power and reactive power respectively, and the formula is as follows:

[0084]

[0085] If the virtual impedance is:

[0086] Z out =R+jwL (6)

[0087] Then the impedance modulus Z and impedance angle θ of the inverter output impedance Z∠θ are:

[0088]

[0089] The maximum active power is:

[0090]

[0091] in,

[0092] k=1-cos(θ) (10)

[0093] Usually, the inverter output impedance is mainly inductive, that is, θ=90°, k=1.

[0094] Figure 7 It is a simplified small signal model of the active loop of a grid-connected converter. Figure 7 middle According to the relevant contents of the system correction technology, the present invention regards the mathematical model of the inverter grid-connected active loop as the object to be corrected, as shown in formula (11), and performs active loop controller G control (s) design.

[0095]

[0096] The specific plan is as follows:

[0097] The performance index requirements of the designed controller are: the dynamic response characteristics of active power meet the requirements that the overshoot is less than or equal to 30%, the system adjustment time is less than or equal to 0.5s, and the steady-state error at unit ramp input is 2%.

[0098] The cutoff frequency and phase margin can be calculated based on the damping ratio and natural oscillation frequency. For a second-order system (in the design of the correction network, it means that the object to be corrected is second-order), according to the relationship between the time domain index and the frequency domain index, that is, the overshoot Adjustment time Cutoff frequency Phase Margin It can be seen that the time domain indicator overshoot is 30% and the adjustment time is 0.5s, which corresponds to the frequency domain indicator cutoff frequency of 21.5rad / s and the phase margin of 39.4°. n is the undamped natural oscillation frequency, ζ is the damping ratio, and Δ is the error band.

[0099] Based on the above-mentioned form of the object to be corrected It usually has the characteristics of a large cut-off frequency and a phase margin of 90°.

[0100] In order to reduce the cut-off frequency, reduce the system's sensitivity to high-frequency noise, and simulate the moment of inertia and damping characteristics of the synchronous generator to improve the dynamic stability of the system, a controller is designed.

[0101] By properly adjusting the inertia J, the system's anti-disturbance capability can be improved while maintaining a good balance between response speed and frequency stability. Similarly, a properly designed damping coefficient D can achieve an optimal balance between response speed and system stability. Therefore, during the design process, it is necessary to comprehensively consider the system's dynamic performance and stability requirements and select appropriate inertia and damping coefficients.

[0102] And using the steady-state error e ss (∞) and static velocity error coefficient k v Calculate the steady-state gain K. The calculation process is shown in equations (12)(13)(14).

[0103] e ss (∞)=2% (12)

[0104]

[0105] Finalizing the controller design.

[0106] At this time, the system open-loop transfer function is shown in equation (15).

[0107]

[0108] Analyze the system open-loop transfer function G 0 (s) frequency domain characteristics, compared with the performance index requirements, to determine whether the system meets the design standards. If it does not meet the index requirements, according to the correction technology in the automatic control principle, G 0 (s) is the object to be corrected, and the correction network G is designed. 2 (s).

[0109] When the cutoff frequency and phase margin are both lower than the performance index requirements, an advance correction network can be designed to increase the cutoff frequency and phase margin; when the cutoff frequency is lower than the performance index requirements and the phase margin is higher than the performance index requirements, a lag correction network can be designed to increase the cutoff frequency while maintaining system stability; when the cutoff frequency is higher than the performance index requirements and the phase margin is lower than the performance index requirements, an advance correction network can be designed to improve the phase margin and adjust the cutoff frequency at the same time; when the cutoff frequency and phase margin are both higher than the performance index requirements, a lag-lead correction network can be designed to balance the response speed and stability of the system.

[0110] In summary, taking G(s) as the object to be corrected, the active loop controller is designed as G control (s) = G 1 (s)G 2 (s).

[0111] The design process of the specific example is as follows:

[0112] by is the active loop to be corrected, where V o =V g =220V.

[0113] The virtual impedance is:

[0114] Z out =0.121+j1.452 (16)

[0115] The impedance modulus and impedance angle are:

[0116] Z=1.457Ω (17)

[0117] k=1-cos(85.2°)=0.92 (18)

[0118] Depend on Figure 8 From the Bode diagram of G(s), we can see that the cutoff frequency of the active power loop to be corrected G(s) is 3.06×10 4 rad / s, phase margin is 90°.

[0119] (1) In order to reduce the cut-off frequency and simulate the moment of inertia and damping characteristics of the synchronous generator, the controller is designed

[0120] Considering the response speed and frequency stability, the inertia J=0.2kg·m is selected in this design process. 2 , damping coefficient D = 1N·m / rad. According to equations (12), (13), (14), using the steady-state error and static speed error coefficient at unit ramp input, the steady-state gain K can be obtained as:

[0121]

[0122] Therefore, we get the controller G 1 (s) is:

[0123]

[0124] At this time, the system open-loop transfer function is:

[0125]

[0126] Depend on Fig. 9 Shown G 0 From the Bode diagram of (s), we can see that G 0 The cut-off frequency of (s) is 15.4rad / s<21.5rad / s, and the phase margin is 17.9°<39.4°.

[0127] (2) To improve G 0 (s) cut-off frequency and phase margin, then G0 (s) is the object to be corrected, and an advance correction network is designed

[0128] Choose the cutoff frequency:

[0129]

[0130] By G 0 The Bode diagram of (s) shows that:

[0131]

[0132] And because:

[0133]

[0134] so:

[0135] a≈3.6 (25)

[0136]

[0137] aT=0.088 (27)

[0138] but:

[0139]

[0140] In summary, For the object to be corrected, the active loop controller is designed as:

[0141]

[0142] At this time, the system open-loop transfer function is:

[0143]

[0144] Depend on Fig.10 The Bode diagram of the open-loop transfer function of the system shown in Fig.11 From the closed-loop transfer function step response diagram shown, it can be seen that the cutoff frequency is 21.4rad / s, the phase margin is 47°, the overshoot is 25.3%, and the adjustment time is 0.244s. The overshoot is less than 30% and the adjustment time is less than 0.5s, which meets the performance index requirements.

[0145] Verified, controller G control The slope of (s) at the cutoff frequency is -28.67dB / dec. This slope is within the reasonable range of engineering applications. This result shows that the controller can effectively meet the system performance requirements in actual operation and has sufficient stability and reliability.

[0146] Finally, the effectiveness of the present invention is verified by simulation. The initial reference value of active power is 6kW, and a step change occurs at t=2s, and the final value is 9kW. Fig.12 and Fig.13 They are the global and local graphs of the active power simulation results. From the simulation results, it can be seen that in the first dynamic response process, the overshoot is 28.9% and the adjustment time is 0.376s; in the second dynamic response process, the overshoot is 26.7% and the adjustment time is 0.375s, both of which meet the performance index requirements of overshoot less than or equal to 30% and system adjustment time less than or equal to 0.5s. The simulation results prove the effectiveness of the proposed scheme.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A grid-connected converter active power controller design and parameter setting method, characterized in that: The steps include: Step S1, determining the performance index requirements of the active power controller of the grid-connected converter; Step S2, according to the performance index requirements and the automatic control principle, the mathematical model of the active power loop of the grid-connected inverter is used as the object to be corrected G, the appropriate moment of inertia J and damping coefficient D are selected, and the steady-state gain K is calculated, and then the controller G1 is designed; Step S3, verifying whether the controller G1 meets the performance index requirements according to the Bode diagram of the system open-loop transfer function G0 after the controller G1 is added at this time; Step S4, modifying the controller G1, treating the open-loop transfer function G0 as a new object to be corrected, and designing the correction network G2 according to the frequency domain characteristics of the open-loop transfer function G0; the frequency domain characteristics include the cutoff frequency and the phase margin; Step S5, using the correction network G2 to correct the object to be corrected G0, to obtain the final grid-connected converter active power controller Gcontrol = G1*G2.

2. The design and parameter setting method of active power controller of grid-connected converter according to claim 1, characterized in that: The performance index requirements include: the dynamic response characteristics of active power meet the overshoot less than or equal to 30%, the system adjustment time less than or equal to 0.5s, and the steady-state error of unit ramp input is 2%.

3. The design and parameter setting method of active power controller for grid-connected converter according to claim 1, characterized in that: The performance indicators include steady-state error, overshoot and adjustment time; The steady-state error e ss (∞) is 2%. For a second-order system, the overshoot calculation method is: The adjustment time t s The calculation method is Where ζ is the damping ratio, ω n is the undamped natural oscillation frequency, and the error band of the adjustment time is 2%.

4. The design and parameter setting method of active power controller for grid-connected converter according to claim 1, characterized in that: The frequency domain characteristics corresponding to the performance index requirements can be calculated based on the damping ratio and the natural oscillation frequency. For a second-order system, the cutoff frequency ω c The calculation method is The calculation method of phase margin γ is: Among them, ω n is the undamped natural oscillation frequency, and ζ is the damping ratio.

5. The design and parameter setting method of active power controller for grid-connected converter according to claim 1, characterized in that: The mathematical model of the active power loop of the grid-connected inverter is: Where s is the Laplace operator, is the maximum active power.

6. The design and parameter setting method of active power controller for grid-connected converter according to claim 1, characterized in that: According to the performance index requirements and the automatic control principle, the mathematical model of the active power loop of the grid-connected inverter is taken as the object to be corrected G, the appropriate moment of inertia J and damping coefficient D are selected, and the steady-state gain K is calculated, and then the controller G1 is designed, including: Comprehensively consider the dynamic performance and stability requirements of the system, select the inertia and damping coefficient, and adjust the inertia J appropriately to improve the system's anti-disturbance ability while maintaining a good balance between response speed and frequency stability; a reasonably designed damping coefficient D can achieve an optimal balance between response speed and system stability; Using the steady-state error e ss (∞) and static velocity error coefficient k v Find the steady-state gain K: e ss (∞)＝2％ Finalizing the controller design.

7. The method for designing and setting parameters of active power controller of grid-connected converter according to any one of claims 1 to 6, characterized in that: The design of the correction network G2 according to the frequency domain characteristics of the open-loop transfer function G0 includes: When the cut-off frequency and phase margin are both less than the performance index requirements, an advance correction network is designed to increase the cut-off frequency and phase margin; When the cut-off frequency is less than the performance index requirement and the phase margin is greater than the performance index requirement, a hysteresis correction network is designed to increase the cut-off frequency while maintaining system stability; When the cutoff frequency is greater than the performance index requirement and the phase margin is less than the performance index requirement, an advance correction network is designed to improve the phase margin and adjust the cutoff frequency at the same time; When the cut-off frequency and phase margin are both greater than the performance index requirements, a lag-lead correction network is designed to balance the response speed and stability of the system.

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