Parameter identification method for active power control of grid-forming photovoltaic converter based on frequency damping

Abstract

The application discloses a parameter identification method for active power control of a network-constructed photovoltaic converter based on frequency damping, which comprises the following steps: collecting the voltage and current of a grid-connected point, and obtaining corresponding direct current components after coordinate transformation; obtaining the output active power and reactive power of the photovoltaic grid-connected converter and the active power and reactive power after low-pass filtering; outputting the frequency and voltage amplitude through active power control and reactive-voltage droop control of the frequency damping; and sending the voltage amplitude and the feedback deviation into a voltage-current double closed loop to generate a converter driving signal through modulation. When the parameter identification of the active power control equation based on the frequency damping is performed, the active power control model is first discretized and then reformed into a difference equation; the unknown parameters in the difference equation are identified and the active power control parameters are calculated. The application can realize the optimization and enhancement of the frequency damping in the active power control of the network-constructed photovoltaic converter, and realize the identification and prediction of the control parameters, so that the photovoltaic converter operates more stably.

Description

Technical Field

[0001] The present invention relates to the field of new energy access and control technology, and more specifically, to a parameter identification method for active power control of a grid-connected photovoltaic converter based on frequency damping. Background Art

[0002] As my country's energy structure continues to optimize, the proportion of renewable energy sources is gradually increasing, with the penetration rate of photovoltaic power generation continuing to rise. As a key link connecting photovoltaic modules to the grid, the converter's control structure is crucial to the stable operation of the system. Unlike the passive following of grid-following control, grid-forming control can achieve active support characteristics, which can improve the dynamic performance and stability of photovoltaic converter control systems. However, the common virtual synchronous grid-forming control has poor active power dynamic response characteristics, slow system dynamic response process, and large overshoot. In existing research, to address the problem of reduced system small-signal stability caused by adjusting control parameters to improve the synchronous stability of photovoltaic converter control systems, a control method that incorporates auxiliary damping in synchronization has been proposed, which improves the synchronous stability and small-signal stability of the control system. However, conventional auxiliary damping control schemes have little effect on the dynamic performance of active power.

[0003] At the same time, current parameter identification of active power response models under grid-connected control typically involves establishing a second-order model of the grid-connected inverter under VSG control. This linearized model determines the applicable range of power perturbations imposed by the model, and ultimately proposes a VSG inertia and damping identification algorithm based on the least-squares method. However, this identification model does not consider the impact of the voltage-current dual closed-loop control structure. During actual system operation, the voltage-current dual closed-loop exhibits a certain lag relative to the preceding power control loop, resulting in a negative damping effect during the dynamic response of active power. Therefore, when modeling active power closed-loop control and studying its power response characteristics, it is necessary to consider the impact of the subsequent voltage and current closed-loop. Summary of the Invention

[0004] In order to address the deficiencies of the above-mentioned prior art, the present invention proposes a parameter identification method for active power control of a grid-connected photovoltaic converter based on frequency damping, in order to improve the damping characteristics in the frequency response process, suppress overshoot in the active power dynamic response process, and accelerate the dynamic response speed of the system, thereby optimizing the dynamic response characteristics of the active power and providing better support for the power grid.

[0005] In order to achieve the above-mentioned object, the present invention adopts the following technical solutions:

[0006] The parameter identification method for active power control of a grid-type photovoltaic converter based on frequency damping of the present invention is characterized by comprising:

[0007] Collect the phase a, phase b, and phase c voltages of the grid-connected point of the grid-connected photovoltaic converter 、 、 and the inductor currents of phases a, b, and c 、 、 After transformation, we can get the voltages of phase a, phase b, and phase c. 、 、 DC components of d-axis and q-axis voltages in a synchronously rotating coordinate system 、 And the inductor currents of phases a, b, and c 、 、 The DC components of the d-axis and q-axis currents in the synchronously rotating coordinate system 、 ;

[0008] based on 、 as well as 、 , obtain the active power output of the grid-connected photovoltaic converter and the reactive power output of the stator ;

[0009] based on and , respectively obtain the active power after low-pass filter and reactive power ;

[0010] Under the premise of considering the voltage outer loop, the frequency of the grid-type photovoltaic converter is output using the active power control equation based on frequency damping. ,angle ;

[0011] Calculate the voltage amplitude of reactive power-voltage droop control output ;

[0012] Calculate the synchronous rotation coordinate system and the DC component of the d-axis voltage Deviation, zero value and The deviation is input into the PI regulator of the voltage outer loop for processing, thereby outputting the d-axis and q-axis current instructions. 、 ;

[0013] Calculate the synchronous rotation coordinate system and The deviation between and The deviation between them is input into the PI regulator of the current inner loop for processing, thereby outputting the PWM modulated d-axis and q-axis voltage instructions. 、 ;

[0014] Will 、 After coordinate inverse transformation and SVPWM modulation, the switch control signal of the grid-type photovoltaic converter is generated to realize active power control of the photovoltaic converter.

[0015] The parameter identification method for active power control of grid-connected photovoltaic converter based on frequency damping of the present invention is also characterized in that the voltages of phases a, b and c at the grid connection point are obtained by using formula (1). 、 、 DC components of d-axis and q-axis voltages in a synchronously rotating coordinate system 、 And the a-phase, b-phase, and c-phase inductor currents 、 、 The DC components of the d-axis and q-axis currents in the synchronously rotating coordinate system 、 :

[0016] (1)

[0017] In formula (1), is the orientation angle of the coordinate transformation, 、 、 Represents the AC components of voltage and current in the stationary coordinate system of phase a, phase b, and phase c, 、 Represents the d-axis and q-axis DC components of voltage and current in the synchronous rotating coordinate system;

[0018] Use formula (2) to obtain the active power output of the photovoltaic converter and output reactive power :

[0019] (2)

[0020] Use formula (3) to obtain the active power after the low-pass filter and reactive power after low-pass filter ,include:

[0021] (3)

[0022] In formula (3), represents the cutoff frequency of the low-pass filter, represents the Laplace operator.

[0023] Furthermore, the active power control equation based on frequency damping is constructed using formula (4):

[0024] (4)

[0025] In formula (4), is the inertia constant; D d is the damping coefficient; is the rated frequency; are active power reference value, For customized parameters.

[0026] Furthermore, the voltage amplitude is obtained using formula (5): , and used as the d-axis voltage reference value:

[0027] (5)

[0028] In formula (5), is the voltage reference value, is the reactive power reference value, is the droop proportional coefficient.

[0029] Furthermore, the d-axis and q-axis voltage instructions of PWM modulation are obtained using formula (6): 、 :

[0030] (6)

[0031] In formula (6), and are the proportional coefficient and integral coefficient of the PI regulator of the current inner loop, and are the proportional coefficient and integral coefficient of the PI regulator of the voltage outer loop, is the inductance value of the filter inductor, is the capacitance value of the filter capacitor.

[0032] Furthermore, the parameters of the active power control equation based on frequency damping are identified according to the following process:

[0033] The active power control equation based on frequency damping is used to construct the active power control model based on frequency damping;

[0034] The active power control model is discretized by using bilinear transformation to obtain the discretized active power control model;

[0035] Construct the difference equation based on the discretized active power control model;

[0036] The damped recursive least squares method is used to identify the parameters in the difference equation, and then the inertia constant of the active power control equation based on frequency damping is calculated using the identified parameters. , damping coefficient D d As well as the proportional coefficient and integral coefficient of the PI regulator of the voltage outer loop.

[0037] Furthermore, the active power control model based on frequency damping is constructed using formula (7): :

[0038] (7)

[0039] In formula (7), represents the gain coefficient;

[0040] Using formula (8), we can get the discretized active power control model: :

[0041] (8)

[0042] In formula (8), 、 are the power setpoint input variation and power response output variation during the power response process, respectively. 、 、 、 、 、 、 There are 7 parameters to be identified respectively. represents a complex frequency variable;

[0043] Use formula (9) to construct the difference equation:

[0044] (9)

[0045] In formula (9), 、 、 、 Respectively represent , No. , No. , No. The power response output change of the wheel, 、 、 、 Respectively represent , No. , No. , No. The change in the power setpoint input of the wheel;

[0046] The recursive relationship of the damped recursive least squares method is constructed using formula (10):

[0047] (10)

[0048] In formula (10), is the damping factor, 、 、 are the parameter vectors to be identified In the , No. , No. The identification value of the wheel, when k=0, let , Indicates the The criterion coefficient of the wheel, Indicates the The inverse of the wheel criterion coefficient, For the The data vector of the round input, T represents the transpose, and there are:

[0049] (11)

[0050] (12)

[0051] The termination criterion is constructed using formula (13), so that when formula (13) is satisfied, the parameters after 7 parameter identification are obtained. 、 、 、 、 、 、 :

[0052] (13)

[0053] In formula (13), Indicates the The wheel identification value, is the threshold of error accuracy.

[0054] Furthermore, the inertia constant is obtained using formula (14): , damping coefficient D d And the proportional coefficient of the PI regulator of the voltage outer loop and the integral coefficient K iu :

[0055] (14)

[0056] In formula (14), 、 、 They represent the inertia transfer coefficient, damping transfer coefficient, and voltage transfer coefficient respectively. is the sampling time of the bilinear transform, and:

[0057] (15).

[0058] The electronic device of the present invention includes a memory and a processor, and is characterized in that the memory is used to store a program that supports the processor to execute the parameter identification method for active power control of the grid-type photovoltaic inverter based on frequency damping, and the processor is configured to execute the program stored in the memory.

[0059] The present invention provides a computer-readable storage medium, and the computer-readable storage medium stores a computer program, which is characterized in that when the computer program is run by a processor, it executes the steps of the parameter identification method for active power control of a grid-type photovoltaic converter based on frequency damping.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] 1. To optimize the dynamic response characteristics of active power in grid-connected photovoltaic converters during grid-connected power generation and better support the power grid, this paper proposes a frequency-damping-based active power response optimization strategy for grid-connected photovoltaic converters. This strategy addresses the issue of insufficient damping during the frequency response process, improves the damping characteristics during the frequency response process, effectively suppresses overshoot during the active power dynamic response process, and accelerates the system's dynamic response speed.

[0062] 2. The present invention fully considers the hysteresis characteristics of voltage loop control, overcomes the problem of inaccurate traditional active power modeling, establishes a complete active power response identification model considering voltage loop control, realizes the identification and prediction of active power control parameters, and ultimately realizes the efficient and stable operation of the grid-type photovoltaic converter.

[0063] 3. The present invention proposes a relevant parameter identification scheme based on the damped recursive least squares method, which overcomes the problem of large computational complexity and easy divergence in traditional least squares parameter identification and realizes the predictive identification of active power control parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is a control structure diagram of a grid-type photovoltaic converter based on frequency damping in the present invention;

[0065] Figure 2 This is a structure diagram of the active power VSG control based on frequency damping in the present invention;

[0066] Figure 3 This is a diagram of the reactive power-voltage droop control structure in the present invention;

[0067] Figure 4 This is a diagram of the voltage and current dual closed-loop control structure of the present invention;

[0068] Figure 5 This is a structural diagram of the active power control model based on frequency damping in the present invention. DETAILED DESCRIPTION

[0069] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0070] In this embodiment, a parameter identification method for active power control of a grid-type photovoltaic converter based on frequency damping has the function of suppressing overshoot of the active power dynamic response process and accelerating the dynamic response speed of the system. At the same time, considering the hysteresis characteristics of the voltage loop control, the active power control parameters are identified and predicted. Specifically, reference is made to Figure 1 , the method is carried out as follows:

[0071] Step 1: Collect the voltages of phases A, B, and C at the grid connection point of the grid-connected photovoltaic inverter. 、 、 and the inductor currents of phases a, b, and c 、 、 And after transformation using formula (1), we can get the voltages of phase a, phase b, and phase c: 、 、 DC components of d-axis and q-axis voltages in a synchronously rotating coordinate system 、 And the inductor currents of phases a, b, and c 、 、 The DC components of the d-axis and q-axis currents in the synchronously rotating coordinate system 、 ;

[0072] (1)

[0073] In formula (1), is the orientation angle of the coordinate transformation, 、 、 Represents the AC components of voltage and current in the stationary coordinate system of phase a, phase b, and phase c, 、 Represents the d-axis and q-axis DC components of voltage and current in the synchronous rotating coordinate system;

[0074] Step 2: Based on 、 as well as 、 , use formula (2) to obtain the active power output of the grid-connected photovoltaic converter and the reactive power output of the stator ;

[0075] Get the active power output of the photovoltaic converter and output reactive power :

[0076] (2)

[0077] Step 3: Based on and , use formula (3) to obtain the active power after low-pass filter and reactive power ;

[0078] (3)

[0079] In formula (3), represents the cutoff frequency of the low-pass filter, represents the Laplace operator.

[0080] Step 4. Reference Figure 2 , using formula (4) to construct the active power control equation based on frequency damping, so that under the premise of considering the voltage outer loop, the frequency of the grid-type photovoltaic converter is output using the active power control equation based on frequency damping. ,angle :

[0081] (4)

[0082] In formula (4), is the inertia constant; D d is the damping coefficient; is the rated frequency; are active power reference value, For customized parameters.

[0083] In the specific implementation, the parameter identification of the active power control equation based on frequency damping is carried out according to the following process:

[0084] Step a, reference Figure 5 , the active power control equation based on frequency damping, using formula (7) to construct the active power control model based on frequency damping ;

[0085] (7)

[0086] In formula (7), represents the gain coefficient;

[0087] Step b: Discretize the active power control model using the bilinear transformation shown in formula (8) to obtain the discretized active power control model ;

[0088] (8)

[0089] In formula (8), 、 are the power setpoint input variation and power response output variation during the power response process, respectively. 、 、 、 、 、 、 There are 7 parameters to be identified respectively. represents a complex frequency variable;

[0090] Step c: Based on the discretized active power control model, a differential equation is constructed using formula (9);

[0091] (9)

[0092] In formula (9), 、 、 、 Respectively represent 、 、 、 The power response output change of the wheel, 、 、 、 Respectively represent 、 、 、 The input change of the power setting value of the wheel

[0093] Step d: Identify the parameters in the differential equation using the damped recursive least squares method to obtain the identified parameters: Step d1: Use formula (10) to construct the recursive relationship of the damped recursive least squares method:

[0094] (10)

[0095] In formula (10), is the damping factor, 、 、 are the parameter vectors to be identified , in 、 、 The wheel identification value, Indicates the Wheel criterion coefficient, Indicates the The inverse of the wheel criterion coefficient, For the The input data vector is round, T represents transpose, specifically:

[0096] (11)

[0097] (12)

[0098] Step d2: Set the initial value of the parameter to be identified, and then use the damped recursive least squares method to iterate. For convenience, in actual application, the initial value is As the recursive process progresses, when the error reaches a certain accuracy When , the operation process terminates, and the termination criterion is:

[0099] (13)

[0100] in Indicates the The identification value of the wheel.

[0101] Step d3: Use the damped recursive least squares method to obtain the actual values ​​of the seven parameters after identification. 、 、 、 、 、 、 .

[0102] Step e: Using the identified parameters, calculate the inertia constant of the active power control equation based on frequency damping as follows: , damping coefficient D d As well as the proportional coefficient and integral coefficient of the PI regulator of the voltage outer loop.

[0103] Step e1: Combining equations (7) and (9), the relationship between the parameters to be identified and the active power control parameters can be obtained as shown in equation (14):

[0104] (14)

[0105] In formula (14), 、 、 They represent the inertia transfer coefficient, damping transfer coefficient, and voltage transfer coefficient respectively. is the sampling time of the bilinear transform. And:

[0106] (15)

[0107] Step e2: Substitute the actual values ​​of the 7 parameters after identification into formula (14) to obtain the control parameters of the active power control system: 、D d and voltage outer loop control parameters , K iu The value of .

[0108] Step 5. Reference Figure 3 , use formula (5) to calculate the voltage amplitude of reactive power-voltage droop control output , and used as the d-axis voltage reference value;

[0109] (5)

[0110] In formula (5), is the voltage reference value, is the reactive power reference value, is the droop proportional coefficient.

[0111] Step 6: Calculate the synchronous rotation coordinate system and the DC component of the d-axis voltage Deviation, zero value and The deviation is input into the PI regulator of the voltage outer loop for processing, thereby outputting the d-axis and q-axis current instructions. 、 ;

[0112] Step 7. Reference Figure 4 , use formula (6) to calculate the synchronous rotating coordinate system and The deviation between and The deviation between them is input into the PI regulator of the current inner loop for processing, thereby outputting the PWM modulated d-axis and q-axis voltage instructions. 、 ;

[0113] (6)

[0114] In formula (6), and are the proportional coefficient and integral coefficient of the PI regulator of the current inner loop, and are the proportional coefficient and integral coefficient of the PI regulator of the voltage outer loop, is the inductance value of the filter inductor, is the capacitance value of the filter capacitor.

[0115] Step 8: 、 After coordinate inverse transformation and SVPWM modulation, the switch control signal of the grid-type photovoltaic converter is generated to realize active power control of the photovoltaic converter.

[0116] In this embodiment, an electronic device includes a memory and a processor, wherein the memory is used to store a program that supports the processor to execute the above method, and the processor is configured to execute the program stored in the memory.

[0117] In this embodiment, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the above method are executed.

[0118] In summary, the present invention adds a control structure based on frequency damping to the traditional grid-type VSG active power control, improves the damping characteristics in the frequency response process, effectively suppresses the overshoot of the active power dynamic response process, and accelerates the dynamic response speed of the system. The active power control output based on frequency damping controls the angle of the system coordinate transformation, the reactive-voltage droop control outputs the reference value of the voltage outer loop, the voltage outer loop output is used as the reference value of the current inner loop, and finally the current inner loop output is PWM modulated to generate the switch tube control signal of the photovoltaic converter. At the same time, the present invention takes into account the hysteresis characteristics of the voltage loop control, establishes a complete active power response identification model considering the voltage loop control, proposes a related parameter identification scheme based on the damped recursive least squares method, and realizes the prediction and identification of the active power control parameters.

Claims

1. A parameter identification method for active power control of a grid-connected photovoltaic converter based on frequency damping, characterized in that: include: Collect the phase a, phase b, and phase c voltages of the grid-connected point of the grid-connected photovoltaic converter 、 、 and the inductor currents of phases a, b, and c 、 、 After transformation, we can get the voltages of phase a, phase b, and phase c. 、 、 DC components of d-axis and q-axis voltages in a synchronously rotating coordinate system 、 And the inductor currents of phases a, b, and c 、 、 The DC components of the d-axis and q-axis currents in the synchronously rotating coordinate system 、 ; based on 、 as well as 、 , obtain the active power output of the grid-connected photovoltaic converter and the reactive power output of the stator ; based on and , respectively obtain the active power after low-pass filter and reactive power ; Under the premise of considering the voltage outer loop, the frequency of the grid-type photovoltaic converter is output using the active power control equation based on frequency damping. ,angle ; Among them, the parameters in the differential equation constructed by the active power control equation based on frequency damping are identified according to the following process, so as to calculate the inertia constant of the active power control equation based on frequency damping using the identified parameters , damping coefficient D d And the proportional coefficient and integral coefficient of the PI regulator of the voltage outer loop: Use Equation (7) to construct an active power control model based on frequency damping : (7) In formula (7), represents the gain coefficient; represents the Laplace operator, is the inertia constant; D d is the damping coefficient, For customized parameters; and are the proportional coefficient and integral coefficient of the PI regulator of the voltage outer loop, Using formula (8), we can get the discretized active power control model: : (8) In formula (8), 、 are the power setpoint input variation and power response output variation during the power response process, respectively. 、 、 、 、 、 、 There are 7 parameters to be identified respectively. represents a complex frequency variable; Use formula (9) to construct the difference equation: (9) In formula (9), 、 、 、 Respectively represent , No. , No. , No. The power response output change of the wheel, 、 、 、 Respectively represent , No. , No. , No. The change in the power setpoint input of the wheel; The recursive relationship of the damped recursive least squares method is constructed using formula (10): (10) In formula (10), is the damping factor, 、 、 are the parameter vectors to be identified In the , No. , No. The identification value of the wheel, when k=0, let , Indicates the The criterion coefficient of the wheel, Indicates the The inverse of the wheel criterion coefficient, For the The data vector of the round input, T represents the transpose, and there are: (11) (12) The termination criterion is constructed using formula (13), so that when formula (13) is satisfied, the parameters after 7 parameter identification are obtained. 、 、 、 、 、 、 : (13) In formula (13), Indicates the The wheel identification value, is the threshold of error accuracy; Calculate the voltage amplitude of reactive power-voltage droop control output ; Calculate the synchronous rotation coordinate system and the DC component of the d-axis voltage Deviation, zero value and The deviation is input into the PI regulator of the voltage outer loop for processing, thereby outputting the d-axis and q-axis current instructions. 、 ; Calculate the synchronous rotation coordinate system and The deviation between and The deviation between them is input into the PI regulator of the current inner loop for processing, thereby outputting the PWM modulated d-axis and q-axis voltage instructions. 、 ; Will 、 After coordinate inverse transformation and SVPWM modulation, the switch control signal of the grid-type photovoltaic converter is generated to realize active power control of the photovoltaic converter.

2. The parameter identification method for active power control of a grid-connected photovoltaic converter based on frequency damping according to claim 1 is characterized in that: Use formula (1) to obtain the phase a, phase b, and phase c voltages of the grid connection point 、 、 DC components of d-axis and q-axis voltages in a synchronously rotating coordinate system 、 And the a-phase, b-phase, and c-phase inductor currents 、 、 The DC components of the d-axis and q-axis currents in the synchronously rotating coordinate system 、 : (1) In formula (1), is the orientation angle of the coordinate transformation, 、 、 Represents the AC components of voltage and current in the stationary coordinate system of phase a, phase b, and phase c, 、 Represents the d-axis and q-axis DC components of voltage and current in the synchronous rotating coordinate system; Use formula (2) to obtain the active power output of the photovoltaic converter and output reactive power : (2) Use formula (3) to obtain the active power after the low-pass filter and reactive power after low-pass filter ,include: (3) In formula (3), Indicates the cutoff frequency of the low-pass filter.

3. The parameter identification method for active power control of a grid-connected photovoltaic converter based on frequency damping according to claim 2 is characterized in that: Formula (4) is used to construct the active power control equation based on frequency damping: (4) In formula (4), is the rated frequency; are the active power reference values ​​respectively.

4. The parameter identification method for active power control of a grid-connected photovoltaic converter based on frequency damping according to claim 3 is characterized in that: Using formula (5) to get the voltage amplitude , and used as the d-axis voltage reference value: (5) In formula (5), is the voltage reference value, is the reactive power reference value, is the droop proportional coefficient.

5. The parameter identification method for active power control of a grid-connected photovoltaic converter based on frequency damping according to claim 4 is characterized in that: Using formula (6), we can get the d-axis and q-axis voltage instructions of PWM modulation: 、 : (6) In formula (6), and are the proportional coefficient and integral coefficient of the PI regulator of the current inner loop, is the inductance value of the filter inductor, is the capacitance value of the filter capacitor.

6. The parameter identification method for active power control of a grid-connected photovoltaic converter based on frequency damping according to claim 5, characterized in that: The parameter identification of the active power control equation based on frequency damping is performed according to the following process: The active power control equation based on frequency damping is used to construct the active power control model based on frequency damping; The active power control model is discretized by using bilinear transformation to obtain the discretized active power control model; Construct the difference equation based on the discretized active power control model; The damped recursive least squares method is used to identify the parameters in the difference equation, and then the inertia constant of the active power control equation based on frequency damping is calculated using the identified parameters. , damping coefficient D d As well as the proportional coefficient and integral coefficient of the PI regulator of the voltage outer loop.

7. The parameter identification method for active power control of grid-type photovoltaic converter based on frequency damping according to claim 6 is characterized in that the inertia constant is obtained by using formula (14) , damping coefficient D d And the proportional coefficient of the PI regulator of the voltage outer loop and the integral coefficient K iu : (14) In formula (14), 、 、 They represent the inertia transfer coefficient, damping transfer coefficient, and voltage transfer coefficient respectively. is the sampling time of the bilinear transform, and: (15)。 8. An electronic device comprising a memory and a processor, characterized in that: The memory is used to store a program that supports the processor to execute the parameter identification method for active power control of a grid-type photovoltaic converter based on frequency damping as described in any one of claims 1-7, and the processor is configured to execute the program stored in the memory.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the parameter identification method for active power control of a grid-connected photovoltaic converter based on frequency damping according to any one of claims 1 to 7 are executed.

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