Transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement method and system

Abstract

This application discloses a transient damping-embedded photovoltaic energy storage power station grid-connected stability enhancement control method and system. This method preprocesses input data to construct a complex transfer function model of the interaction between the photovoltaic energy storage system and the grid. Combined with Bode plots and Nyquist stability curves, it analyzes the influence trends of parameters such as transient damping, further optimizes and executes parameter control, and realizes the stability interaction analysis and enhancement of the grid-connected and grid-integrated hybrid control system. Compared with traditional high-dimensional and physically multi-input multi-output models, this method is more practical, versatile, and scalable. It is of great significance and high practical value for promoting the consumption of new energy sources and enhancing the safety and stability support capabilities of energy storage and new energy sources for new power systems. It can be widely applied in the fields of new energy and energy storage technologies.

Description

Technical Field

[0001] This invention relates to the fields of new energy and energy storage technology, and in particular to a method and system for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded. Background Technology

[0002] With the increasing proportion of new energy sources and the large-scale integration of power electronic converters, the inertia level of new power systems is gradually decreasing while random uncertainty is increasing. The safe and stable operation of power systems faces increasingly severe challenges, particularly in the safety and stability of frequency and voltage, urgently requiring new technologies to provide safe and stable support. Photovoltaic energy storage grid-connected power generation systems offer a promising approach to solving these problems and are currently a hot research topic globally. Typically, due to differences in manufacturers and other factors, photovoltaic energy storage grid-connected power generation systems may contain hybrid control modes with different control strategies, such as grid connection and grid integration, which can lead to interactions between the photovoltaic system and the energy storage system, affecting the overall safety and stability support capability of the system. Therefore, constructing methods to enhance the stability of photovoltaic energy storage grid-connected power generation systems and address the interaction effects on grid connection stability is crucial for photovoltaic energy storage power generation systems to provide safe and stable support to the grid and promote the consumption of new energy sources.

[0003] Current research mainly focuses on three types of methods: methods based on multiple-input multiple-output state-space models, methods based on impedance models, and methods based on a combination of state-space and impedance models. These methods typically face problems such as high-dimensional models, difficulty in providing clear physical interpretations, and difficulty in analyzing and evaluating the interaction effects and stability regions between subsystems. They are not convenient for widespread application and urgently require the development of new technologies and methods. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art; to this end, the present invention proposes a method and system for enhancing grid-connected stability of photovoltaic energy storage power stations with transient damping embedded in them.

[0005] A first aspect of the present invention provides a method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in it, comprising: Step 1: Construct grid-connected control strategies for photovoltaic power generation systems and grid-connected control strategies for energy storage systems; Step 2: Construct the inner-loop control admittance model of the photovoltaic energy storage system; Step 3: Construct a complex transfer function model of the interaction effects of the photovoltaic energy storage system; Step 4: Analyze and evaluate the interactive effects on the stability of the photovoltaic energy storage system; Step 5: Construct a method to enhance the grid-connected stability of photovoltaic energy storage power stations with embedded transient damping; Step 6: Evaluate the grid-connected stability enhancement effect of photovoltaic energy storage power stations with embedded transient damping.

[0006] Step 1, which involves constructing a grid-connected control strategy for the photovoltaic power generation system and a grid-connected control strategy for the energy storage system, includes: a grid-connected control strategy for the photovoltaic power generation system and a grid-connected control strategy for the energy storage system.

[0007] The mathematical expression for the grid-connected control strategy of the photovoltaic power generation system is: (1) (2) (3) (4) in, For the complex variable in the Laplace transform, The phase-locked loop outputs the angle, used for the transformation from dq coordinates to abc coordinates; The rated angular frequency of the power system; K p,pll and K i,pll These are the proportional gain and integral gain of the phase-locked loop PI controller, respectively. v pv,d and v pv,q These are the d-axis and q-axis components of the photovoltaic inverter output voltage, respectively. and These are the d-axis and q-axis reference components of the filter inductor current of the photovoltaic inverter, respectively. and These are the d-axis and q-axis components of the filter inductor current in the photovoltaic inverter, respectively. V dc and V dcref These are the reference and actual DC voltage values ​​on the DC side of the photovoltaic power generation system, respectively. K p,DC and K i,DC These are the proportional gain and integral gain of the PI controller for the DC voltage of the photovoltaic power generation system, respectively. and These are the proportional gain and integral gain of the PI controller for the inner loop current of the photovoltaic power generation system inverter, respectively. L pv,f The filter inductor is the LC filter of the photovoltaic inverter; k pv,VF This refers to the voltage feedforward coefficient of the current control loop in a photovoltaic inverter. and These are the d-axis and q-axis components of the output voltage reference command for the photovoltaic inverter, respectively.

[0008] The mathematical expression for the grid-connected control strategy of the energy storage system is: (5) (6) (7) (8) (9) in, The output angle for the active power synchronization control of the energy storage system converter is used for the transformation from dq coordinates to abc coordinates; and These are the virtual inertia and virtual damping of the energy storage system, respectively. P es,ref and P es,out These are the reference value and the measured value of the active power output by the energy storage system, respectively. The angular frequency of the power grid; and These are the proportional gain and integral gain of the PI controller in the voltage control loop of the energy storage system converter, respectively. and These are the proportional gain and integral gain of the PI controller in the current control loop of the energy storage system converter, respectively. v pv,d and v pv,q These are the d-axis and q-axis components of the photovoltaic inverter output voltage, respectively. and These are the d-axis and q-axis reference components of the filter inductor current of the energy storage system converter, respectively, which serve as the input reference values ​​for the inner loop current controller. and These are the d-axis and q-axis components of the filter inductor current of the energy storage converter, respectively. and These are the reference values ​​for the d-axis and q-axis of the energy storage converter output voltage, respectively. and These are the d-axis and q-axis components of the energy storage converter output voltage, respectively. L es,f The filter inductor is the LC filter of the energy storage converter; f es,VF This represents the voltage feedforward coefficient of the current control loop in the energy storage converter. and These are the d-axis and q-axis components of the energy storage system converter output voltage reference command, respectively. L es,v This is a virtual inductance.

[0009] Step 2 involves constructing the inner-loop control admittance model of the photovoltaic energy storage system, including the inner-loop control admittance model of the grid-connected photovoltaic power generation system and the inner-loop admittance model of the grid-connected energy storage system.

[0010] The mathematical expression for the inner-loop control admittance model of the grid-connected photovoltaic power generation system is as follows: (10) in, L pv,f and C pv,f These are the filter inductor and filter capacitor of the LC filter in a photovoltaic inverter, respectively. The transfer function for the PI control of the inner loop current in the inverter of a photovoltaic power generation system; and These are the positive and negative components of the complex admittance model of the inner loop control of a grid-controlled photovoltaic power generation system.

[0011] The mathematical expression for the inner-loop admittance model of the grid-controlled energy storage system is as follows: (11) in, and These are the transfer functions for the PI control of the internal current loop and voltage loop of the energy storage system converter, respectively. The voltage feedforward control transfer function of the internal current control loop of the energy storage system converter ( For voltage feedforward control gain, (This refers to the voltage feedforward control time constant); and These are the positive and negative components of the complex admittance model of the inner loop control of a grid-controlled energy storage system.

[0012] Step 3, constructing a complex transfer function model of the interaction between the photovoltaic power generation system and the energy storage system, includes: ① constructing a complex transfer function model of the interaction between the output power angle of the photovoltaic power generation system, the output power angle of the energy storage system, and the power angle of the grid in the first coordinate system; ② constructing a complex transfer function model of the interaction between the output power angle of the photovoltaic power generation system, the output power angle of the energy storage system, and the power angle of the grid in the second coordinate system; ③ constructing a complex transfer function model considering the influence of the grid power angle on the output power angle of the photovoltaic power generation system, including the role of the energy storage system; ④ constructing a complex transfer function model considering the influence of the grid power angle on the output power angle of the energy storage system, including the role of the photovoltaic power generation system.

[0013] The complex transfer function model of the interaction between the output power angle of the photovoltaic power generation system, the output power angle of the energy storage system, and the power angle of the power grid in the first coordinate system is expressed as follows: (12) in, (13) (14) (15) in, , , , and They represent , and The conjugate of complex numbers, This is the transfer function for the phase-locked loop.

[0014] The complex transfer function model of the interaction between the output power angle of the photovoltaic power generation system, the output power angle of the energy storage system, and the power angle of the power grid in the second coordinate system is expressed as follows: (16) in, (17) (18) (19) in, , and They are respectively and The conjugate of complex numbers.

[0015] The complex transfer function model considering the influence of the grid power angle on the output power angle of the photovoltaic power generation system, including the role of the energy storage system, has the following mathematical expression: (20) in, This refers to the change in the output power angle of the photovoltaic power generation system. This is the change in the power angle of the power grid. Let be the closed-loop transfer function of the phase-locked loop. and The transfer functions for the two intermediate variables of the photovoltaic system are as follows: (twenty one) (twenty two) in, For the transfer function related to power synchronization control; This is the internal transfer function of the energy storage system. This represents the coupling transfer function from photovoltaics to energy storage; This refers to the internal transfer function of the photovoltaic system. This represents the coupling transfer function from energy storage to photovoltaics.

[0016] The complex transfer function model considering the influence of the grid power angle on the output power angle of the energy storage system, including the effect of the photovoltaic power generation system, has the following mathematical expression: (twenty three) in, This refers to the change in the output power angle of the energy storage system. and These are the transfer functions for two intermediate variables in the energy storage system, and their specific expressions are as follows: (twenty four) (25) in, Let the transfer function be the phase-locked loop transfer function of the photovoltaic system. This refers to the internal transfer function of the photovoltaic system. This represents the coupling transfer function from energy storage to photovoltaics. This represents the coupling transfer function from photovoltaics to energy storage. This is the internal transfer function of the energy storage system.

[0017] The analysis and evaluation of the interaction between the photovoltaic energy storage system and the stability of the photovoltaic energy storage system in step 4 includes: step 41. analyzing and evaluating the stability of the photovoltaic system without the energy storage system; step 42. analyzing and evaluating the impact of the energy storage system on the stability of the photovoltaic system; step 43. evaluating the impact of the energy storage system on the overall system stability support capability, and analyzing the factors that affect the stability support capability of the energy storage system, including the photovoltaic system.

[0018] Step 41, which analyzes and evaluates the stability of the photovoltaic system without an energy storage system, mainly includes the following steps: Step 410: Set the positive components of the inner-loop control complex admittance model of the grid-controlled energy storage system to zero, i.e. ; Step 411: Based on Step 410 and Equation (20), construct the small-signal stability condition for the photovoltaic system, namely: (26) 412: Analyze the changes in power grid strength (Lg increases from small to large) and the parameters of the phase-locked loop (PLL). K p,pll and K i,pll From small to large, photovoltaic system current control loop parameters ( and ) and DC voltage control parameters ( K p,DC andK i,DC When the values ​​increase from small to large, the stability of the photovoltaic system is determined by combining Bode plots and Nyquist curves, and the influence trend of the above parameters on its stability is evaluated. Step 42, which analyzes and evaluates the impact of the energy storage system on the stability of the photovoltaic system, mainly includes the following steps: Step 420: Based on the above equation (20), construct the equivalent Nyquist stability condition for the photovoltaic system, i.e.: transfer function f δpv1 (s) f PLL (s) and transfer function ( G pv (s)+ G in,es (s)) f PSC (s) satisfies the Nyquist stability criterion; Step 421: When analyzing the changes in voltage loop control parameters, virtual impedance parameters, current loop control parameters, and voltage feedforward control parameters of the energy storage system, combine Bode plots and Nyquist curves to analyze and judge the stability of the photovoltaic system and evaluate the influence trend of the above parameters on its stability.

[0019] Step 43 assesses the impact of the energy storage system on the overall system stability and analyzes the factors affecting the stability support capability of the energy storage system, including the photovoltaic system. Specific steps mainly include: Step 430: Based on the stability criterion established in the first step of analyzing and evaluating the impact of the energy storage system on the stability of the photovoltaic system in Step 42, and combined with the Bode plot and Nyquist curve, analyze and evaluate the impact of changes in the active power synchronous control loop parameters (virtual inertia and virtual damping) of the energy storage system on the stability support capability of the grid-controlled energy storage system. Step 431: Combining Bode plots and Nyquist curves, analyze and evaluate the impact of the photovoltaic system's phase-locked loop parameters and its output active power on the overall support capability of the energy storage system. Step 432: Based on the analysis results of steps 41, 42 and 43, identify the main influencing factors and influencing modes of the stability support capability of the overall structure network-controlled energy storage system.

[0020] Step 5, the method for enhancing the grid-connected stability of a photovoltaic energy storage power station with embedded transient damping, includes: Step 51: Perform feedforward compensation according to frequency, and adjust the d-axis voltage control reference command of the inner loop of the energy storage converter. The adjusted d-axis voltage reference command of the inner loop of the energy storage converter is as follows: (27) in, This is the reference command for the d-axis voltage control of the inner loop of the energy storage converter after adjustment. K es,q The reactive power-voltage droop coefficient of the energy storage system; K es,D The feedforward compensation coefficient is used for frequency compensation. ω es and ω g These are the angular frequencies of the energy storage system and the power grid, respectively. Q es,ref and Q es These are the reference value and the actual measured value of the reactive power output by the energy storage converter, respectively.

[0021] Step 52: Following Steps 2 and 3, construct new inner-loop control admittance models for the photovoltaic energy storage system after adjusting the inner-loop d-axis voltage control reference command of the energy storage converter (using...). , and , A new complex transfer function model for the interaction between photovoltaic energy storage systems and photovoltaic energy storage systems; (28) (29) in, and It can be obtained by calculation according to the methods of equations (13)-(15), (21) and (22); and It can be obtained by calculation according to the methods of equations (17)-(19), (24) and (25); and These are respectively called the complex transfer functions of the interaction between the photovoltaic system and the energy storage system.

[0022] Step 6 evaluates the grid-connected stability enhancement effect of the photovoltaic energy storage power station with embedded transient damping: Step 61: Using the results obtained in Step 5, i.e., equations (28) and (29), reconstruct the equivalent Nyquist stability condition of the photovoltaic system, i.e., the transfer function. and transfer function Satisfies the Nyquist stability criterion; Step 62: When the energy storage system compensates for the feedforward coefficient according to the frequency... K es,D When changes occur, the stability evolution trend of the photovoltaic system is analyzed and judged by combining Bode plots and Nyquist curves, and the feedforward compensation coefficient is evaluated. K es,D It enhances the stability of its grid connection.

[0023] Step 63: Based on the analysis and evaluation results of Step 2, and considering the system stability, dynamic response characteristics, and steady-state characteristics, select the optimal feedforward compensation coefficient. K es,D。

[0024] A second aspect of the present invention provides a transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement control system, comprising: Data acquisition and pre-storage module: used to acquire and store the input data and corresponding output results required to build the interaction influence model of photovoltaic energy storage system, calculate Bode plot, Nyquist curve and amplitude-phase stability margin, as well as the data required to demonstrate the grid connection stability enhancement effect of photovoltaic energy storage power station; Data preprocessing module: used to process the input data acquired by the data acquisition module to obtain preprocessed input data; Photovoltaic energy storage system interaction influence model construction module: used to construct a complex transfer function model of the interaction influence of photovoltaic energy storage system based on the preprocessed input data obtained by the data processing module; Bode plot, Nyquist curve and amplitude and phase stability margin calculation module: used to draw Bode plot and Nyquist stability curve based on the preprocessed input data obtained from the data processing module, and calculate the amplitude and phase stability margin under different parameters; Effect output and display module: used to demonstrate the enhancement effect of the feedforward compensation coefficient based on frequency perturbation on the grid-connected stability of photovoltaic energy storage power stations.

[0025] The transient damping-embedded photovoltaic energy storage power station grid-connected stability enhancement control system includes the following process steps: Step 1: Obtain the input data required to provide the grid-connected stability enhancement control system for transient damping embedded in photovoltaic energy storage power stations; Step 2: Preprocess the acquired input data; Step 3: Based on the preprocessed input data, construct a complex transfer function model of the interaction effects of the photovoltaic energy storage system. Step 4: Based on the complex variable transfer function model of interaction constructed in Step 3, plot the Bode plot and Nyquist stability curve, and calculate the magnitude and phase stability margin under different parameters; Step 5: Based on the results obtained in Step 4, optimize the grid-connected stability enhancement parameters of the photovoltaic energy storage system and control it according to the optimal parameters; Step 6: Demonstrate the grid-connected stability enhancement control effect of photovoltaic energy storage power station based on transient damping.

[0026] The first step, embedding transient damping into the photovoltaic energy storage power station's grid-connected stability enhancement control system, requires the following input data: proportional and integral gains of all PI controllers (voltage control loop, current control loop, DC voltage control, active power synchronous control, and phase-locked loop control); reactive power-voltage droop coefficient, virtual inertia and virtual damping, virtual impedance; grid connection inductance, line impedance, LC filter inductance and capacitance, voltage feedforward control parameters, transient damping coefficients for frequency disturbance compensation, grid rated voltage and frequency, rated DC voltage on the DC side of the photovoltaic system; measured values ​​of filter inductor current, output voltage, and output current of the photovoltaic and energy storage systems, measured values ​​of grid point of common coupling frequency and voltage, and measured values ​​of DC voltage on the DC side of the photovoltaic system.

[0027] The second step, preprocessing the acquired input data, refers to using a low-pass filter to filter and remove noise from the measured values ​​of the photovoltaic energy storage system's filter inductor current, output voltage and current, DC voltage on the DC side of the photovoltaic system, and the frequency and voltage of the grid's point of common coupling.

[0028] The third step of constructing the complex transfer function model of the interaction between the photovoltaic energy storage system refers to constructing models (20), (23), (28) and (29), specifically according to steps 2, 3 and 5 of the first aspect of the present invention.

[0029] The sixth step demonstrates the grid-connected stability enhancement control effect of the photovoltaic energy storage power station based on transient damping embedding, including: displaying the frequency and voltage of the grid's point of common coupling before and after the disturbance; the active and reactive power injected by the photovoltaic energy storage power station to the point of common coupling before and after the disturbance; and comparing the active power, reactive power, frequency (power angle), and voltage curves of the photovoltaic energy storage power station before and after using stability enhancement to optimize the light parameters, thus demonstrating the stability enhancement control effect.

[0030] A third aspect of the present invention provides a readable storage medium for a transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement control system, comprising: at least one processor and a memory communicatively connected to the at least one processor; the processor executes the transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement method as described in any of the first aspects by calling a computer program stored in the memory; the computer-readable storage medium stores computer-executable instructions for causing a computer to execute the method as described in any of the first aspects.

[0031] The beneficial effects of this invention are: This application discloses a transient damping-embedded photovoltaic energy storage power station grid-connected stability enhancement control method and system. By acquiring and preprocessing the required input data, a complex transfer function model of the interaction between the photovoltaic energy storage system and the grid is constructed. Based on this model, combined with the plotted Bode plot and Nyquist stability curve, the system amplitude and phase stability margin under different parameters are calculated. The influence trend of parameters such as transient damping on the stability of the photovoltaic energy storage system is analyzed, and the grid-connected stability enhancement parameters of the photovoltaic energy storage system are further optimized. Control is then performed according to the optimized parameters, realizing the stability interaction analysis and stability enhancement of the grid-connected photovoltaic energy storage system with hybrid grid-connected control. The proposed transient damping-embedded photovoltaic energy storage power station grid-connected stability enhancement control method solves the problems of high dimensionality, unclear physical meaning, and difficulty in analyzing the interaction effects and stability domain between subsystems, which are faced by traditional multi-input multi-output state-space models and impedance models from the perspective of single-input single-output transfer function. It is more practical, versatile and scalable, and has great significance and high practical value for promoting the consumption of new energy and improving the safety and stability support capability of energy storage and new energy for new power systems. It can be widely applied in the fields of new energy and energy storage technology. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a photovoltaic energy storage grid-connected power generation system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the grid-connected control strategy structure of the photovoltaic power generation system according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the grid control strategy structure of the energy storage system according to an embodiment of the present invention; Figure 4 This is the construction process of the photovoltaic energy storage power station grid-connected stability enhancement control method with transient damping embedded in the embodiments of the present invention; Figure 5 This is a block diagram of the interactive structure of a photovoltaic energy storage system according to embodiments of the present invention; Figure 6 This is a flowchart illustrating the stability interaction analysis of a photovoltaic energy storage system according to an embodiment of the present invention. Figure 7 This is a schematic diagram of the transient damping embedding method for enhancing grid-connected stability of photovoltaic energy storage power stations according to an embodiment of the present invention; Figure 8 This is a flowchart for evaluating the grid-connected stability enhancement effect of photovoltaic energy storage power stations with transient damping embedded in an embodiment of the present invention; Figure 9 This is a schematic diagram of the grid-connected stability enhancement control system for a photovoltaic energy storage power station with embedded transient damping according to an embodiment of the present invention; Figure 10 This is a control flowchart of the photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded in an embodiment of the present invention. Detailed Implementation

[0033] The specific embodiments of the present invention will now be described with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. Those skilled in the art can obtain other drawings and other embodiments based on these drawings without any creative effort.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Example

[0035] This invention provides a transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement control method.

[0036] like Figure 1 The diagram shown is a schematic of a photovoltaic energy storage grid-connected power generation system according to an embodiment of the present invention. The diagram includes: a grid-controlled photovoltaic power generation system, a grid-controlled energy storage system, and an equivalent main grid. Both the photovoltaic power generation system and the energy storage system are connected to the grid's point of common coupling (PCC) via a converter; an LC filter is installed at the converter output; the line parameters (inductance) between the photovoltaic power generation system and the PCC are... L line1 This indicates that the power grid line parameters (inductance) are expressed using... L g express.

[0037] like Figure 2 The diagram shown is a schematic diagram of the grid-connected control strategy structure of a photovoltaic power generation system according to an embodiment of the present invention: like Figure 3 The diagram shown is a schematic diagram of the grid control strategy structure of the energy storage system according to an embodiment of the present invention: like Figure 4 The diagram shows a flowchart of a photovoltaic energy storage power station grid-connected stability enhancement control method with transient damping embedded according to an embodiment of the present invention. The method includes the following specific steps: Step 1: Construct grid-connected control strategies for photovoltaic power generation systems and grid-connected control strategies for energy storage systems; Step 2: Construct the inner-loop control admittance model of the photovoltaic energy storage system; Step 3: Construct a complex transfer function model of the interaction effects of the photovoltaic energy storage system; Step 4: Analyze and evaluate the interactive effects on the stability of the photovoltaic energy storage system; Step 5: Construct a method to enhance the grid-connected stability of photovoltaic energy storage power stations with embedded transient damping; Step 6: Evaluate the grid-connected stability enhancement effect of photovoltaic energy storage power stations with embedded transient damping.

[0038] Furthermore, the flowchart of the photovoltaic energy storage power station grid-connected stability enhancement control method with transient damping embedded in the embodiment of the present invention ( Figure 4 Step 1 of the process involves constructing a grid-connected control strategy for the photovoltaic power generation system and a grid-connected control strategy for the energy storage system, including: a grid-connected control strategy for the photovoltaic power generation system and a grid-connected control strategy for the energy storage system.

[0039] Please combine Figure 2 The schematic diagram of the grid-following control strategy structure of the photovoltaic power generation system according to an embodiment of the present invention is shown below. The mathematical expression of the grid-following control strategy of the photovoltaic power generation system is as follows: (1) (2) (3) (4) in, For the complex variable in the Laplace transform, The phase-locked loop outputs the angle, used for the transformation from dq coordinates to abc coordinates; The rated angular frequency of the power system; K p,pll and K i,pll These are the proportional gain and integral gain of the phase-locked loop PI controller, respectively. v pv,d and v pv,q These are the d-axis and q-axis components of the photovoltaic inverter output voltage, respectively. and These are the d-axis and q-axis reference components of the filter inductor current of the photovoltaic inverter, respectively. and These are the d-axis and q-axis components of the filter inductor current in the photovoltaic inverter, respectively. V dc and V dcref These are the reference and actual DC voltage values ​​on the DC side of the photovoltaic power generation system, respectively. K p,DC and K i,DC These are the proportional gain and integral gain of the PI controller for the DC voltage of the photovoltaic power generation system, respectively. and These are the proportional gain and integral gain of the PI controller for the inner loop current of the photovoltaic power generation system inverter, respectively. L pv,f The filter inductor is the LC filter of the photovoltaic inverter; k pv,VFThis refers to the voltage feedforward coefficient of the current control loop in a photovoltaic inverter. and These are the d-axis and q-axis components of the output voltage reference command for the photovoltaic inverter, respectively.

[0040] Please combine Figure 3 The schematic diagram of the grid control strategy of the energy storage system in this embodiment of the invention is shown. The mathematical expression of the grid control strategy of the energy storage system is as follows: (5) (6) (7) (8) (9) in, The output angle for the active power synchronization control of the energy storage system converter is used for the transformation from dq coordinates to abc coordinates; and These are the virtual inertia and virtual damping of the energy storage system, respectively. P es,ref and P es,out These are the reference value and the measured value of the active power output by the energy storage system, respectively. The angular frequency of the power grid; and These are the proportional gain and integral gain of the PI controller in the voltage control loop of the energy storage system converter, respectively. and These are the proportional gain and integral gain of the PI controller in the current control loop of the energy storage system converter, respectively. v pv,d and v pv,q These are the d-axis and q-axis components of the photovoltaic inverter output voltage, respectively. and These are the d-axis and q-axis reference components of the filter inductor current of the energy storage system converter, respectively, which serve as the input reference values ​​for the inner loop current controller. and These are the d-axis and q-axis components of the filter inductor current of the energy storage converter, respectively. and These are the reference values ​​for the d-axis and q-axis of the energy storage converter output voltage, respectively. and These are the d-axis and q-axis components of the energy storage converter output voltage, respectively. L es,f The filter inductor is the LC filter of the energy storage converter; f es,VFThis represents the voltage feedforward coefficient of the current control loop in the energy storage converter. and These are the d-axis and q-axis components of the energy storage system converter output voltage reference command, respectively. L es,v This is a virtual inductance.

[0041] Furthermore, such as Figure 4 As shown, in the transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement control method of the present invention, step 2 of constructing the inner loop control admittance model of the photovoltaic energy storage system includes the inner loop control admittance model of the grid-connected photovoltaic power generation system and the inner loop admittance model of the grid-connected energy storage system.

[0042] Please combine Figure 2 The schematic diagram of the grid-following control strategy structure of the photovoltaic power generation system according to the embodiment of the present invention, and the mathematical expression of the inner-loop control admittance model of the grid-following control photovoltaic power generation system are as follows: (10) in, L pv,f and C pv,f These are the filter inductor and filter capacitor of the LC filter in a photovoltaic inverter, respectively. The transfer function for the PI control of the inner loop current in the inverter of a photovoltaic power generation system; and These are the positive and negative components of the complex admittance model of the inner loop control of a grid-controlled photovoltaic power generation system.

[0043] Please combine Figure 3 The schematic diagram of the grid-connected control strategy structure of the energy storage system according to an embodiment of the present invention, and the mathematical expression of the inner-loop admittance model of the grid-connected control type energy storage system are as follows: (11) in, and These are the transfer functions for the PI control of the internal current loop and voltage loop of the energy storage system converter, respectively. The voltage feedforward control transfer function of the internal current control loop of the energy storage system converter ( For voltage feedforward control gain, (This refers to the voltage feedforward control time constant); and These are the positive and negative components of the complex admittance model of the inner loop control of a grid-controlled energy storage system.

[0044] Furthermore, the flowchart of the photovoltaic energy storage power station grid-connected stability enhancement control method with transient damping embedded in the embodiment of the present invention ( Figure 4Step 3 of the process involves constructing a complex transfer function model of the interaction between the photovoltaic power generation system, the energy storage system, and the grid power angle in the first coordinate system. This includes: ① constructing a complex transfer function model of the interaction between the output power angle of the photovoltaic power generation system, the output power angle of the energy storage system, and the grid power angle in the second coordinate system; ③ constructing a complex transfer function model that considers the influence of the grid power angle, including the role of the energy storage system, on the output power angle of the photovoltaic power generation system; and ④ constructing a complex transfer function model that considers the influence of the grid power angle, including the role of the photovoltaic power generation system, on the output power angle of the energy storage system.

[0045] Please combine Figure 5 The diagram shown in the embodiment of the present invention illustrates the interactive structure of a photovoltaic energy storage system. The complex transfer function model of the interaction between the output power angle of the photovoltaic power generation system, the output power angle of the energy storage system, and the power angle of the power grid in the first coordinate system is expressed as follows: (12) in, (13) (14) (15) in, , , , and They represent , and The conjugate of complex numbers, This is the transfer function for the phase-locked loop.

[0046] Please combine Figure 5 The diagram shown in the embodiment of the present invention illustrates the interactive structure of a photovoltaic energy storage system. The complex transfer function model of the interaction between the output power angle of the photovoltaic power generation system, the output power angle of the energy storage system, and the power angle of the power grid in the second coordinate system is expressed mathematically as follows: (16) in, (17) (18) (19) in, , and They are respectively and The conjugate of complex numbers.

[0047] Please combine Figure 5 The diagram shown in the embodiment of the present invention illustrates the interaction structure of a photovoltaic energy storage system. The complex transfer function model considering the influence of the grid power angle, including the energy storage system's effect, on the output power angle of the photovoltaic power generation system is expressed mathematically as follows: (20) in, This refers to the change in the output power angle of the photovoltaic power generation system. This is the change in the power angle of the power grid. Let be the closed-loop transfer function of the phase-locked loop. and The transfer functions for the two intermediate variables of the photovoltaic system are as follows: (twenty one) (twenty two) in, For the transfer function related to power synchronization control; This is the internal transfer function of the energy storage system. This represents the coupling transfer function from photovoltaics to energy storage; This refers to the internal transfer function of the photovoltaic system. This represents the coupling transfer function from energy storage to photovoltaics.

[0048] Please combine Figure 5 The diagram shown in the embodiment of the present invention illustrates the interaction structure of a photovoltaic energy storage system. The complex transfer function model, which considers the influence of the grid power angle, including the photovoltaic power generation system, on the output power angle of the energy storage system, has the following mathematical expression: (twenty three) in, This refers to the change in the output power angle of the energy storage system. and These are the transfer functions for two intermediate variables in the energy storage system, and their specific expressions are as follows: (twenty four) (25) in, Let the transfer function be the phase-locked loop transfer function of the photovoltaic system. This refers to the internal transfer function of the photovoltaic system. This represents the coupling transfer function from energy storage to photovoltaics. This represents the coupling transfer function from photovoltaics to energy storage. This is the internal transfer function of the energy storage system.

[0049] Furthermore, such as Figure 4As shown, step 4 of the transient damping-embedded photovoltaic energy storage power station grid-connected stability enhancement control method of the present invention analyzes and evaluates the interactive influence of the stability of the photovoltaic energy storage system, including: step 41. Analyzing and evaluating the stability of the photovoltaic system without the energy storage system; step 42. Analyzing and evaluating the impact of the energy storage system on the stability of the photovoltaic system; step 43. Evaluating the impact of the energy storage system on the overall system stability support capability, and analyzing the factors including the photovoltaic system that affect the stability support capability of the energy storage system.

[0050] Please combine Figure 6 The flowchart shown in this embodiment of the invention illustrates the analysis of the interaction between the stability of a photovoltaic energy storage system and its instability. Step 41, which analyzes and evaluates the stability of the photovoltaic system without an energy storage system, includes the following specific steps: Step 410: Set the positive components of the inner-loop control complex admittance model of the grid-controlled energy storage system to zero, i.e. ; Step 411: Based on Step 410 and Equation (20), construct the small-signal stability condition for the photovoltaic system, namely: (26) 412: Analyze the changes in power grid strength (Lg increases from small to large) and the parameters of the phase-locked loop (PLL). K p,pll and K i,pll From small to large, photovoltaic system current control loop parameters ( and ) and DC voltage control parameters ( K p,DC and K i,DC When the values ​​increase from small to large, the stability of the photovoltaic system is determined by combining Bode plots and Nyquist curves, and the influence trend of the above parameters on its stability is evaluated. Please combine Figure 6 The flowchart shown in this embodiment of the invention illustrates the interaction analysis of the stability of a photovoltaic energy storage system. Step 42 analyzes and evaluates the impact of the energy storage system on the stability of the photovoltaic system, and the specific steps include: Step 420: Based on the above equation (20), construct the equivalent Nyquist stability condition for the photovoltaic system, i.e.: transfer function f δpv1 (s) f PLL (s) and transfer function ( G pv (s)+ G in,es (s)) f PSC (s) satisfies the Nyquist stability criterion; Step 421: When analyzing the changes in voltage loop control parameters, virtual impedance parameters, current loop control parameters, and voltage feedforward control parameters of the energy storage system, combine Bode plots and Nyquist curves to analyze and judge the stability of the photovoltaic system and evaluate the influence trend of the above parameters on its stability.

[0051] Step 421: When analyzing the changes in voltage loop control parameters, virtual impedance parameters, current loop control parameters, and voltage feedforward control parameters of the energy storage system, combine Bode plots and Nyquist curves to analyze and judge the stability of the photovoltaic system and evaluate the influence trend of the above parameters on its stability.

[0052] Please combine Figure 6 The flowchart shown in this embodiment of the invention illustrates the interaction analysis of the stability of a photovoltaic energy storage system. Step 43 assesses the impact of the energy storage system on the overall system stability and analyzes factors affecting the stability support capability of the energy storage system, including the photovoltaic system. The specific steps mainly include: Step 430: Based on the stability criterion established in the first step of analyzing and evaluating the impact of the energy storage system on the stability of the photovoltaic system in Step 42, and combined with the Bode plot and Nyquist curve, analyze and evaluate the impact of changes in the active power synchronous control loop parameters (virtual inertia and virtual damping) of the energy storage system on the stability support capability of the grid-controlled energy storage system. Step 431: Combining Bode plots and Nyquist curves, analyze and evaluate the impact of changes in the photovoltaic system's phase-locked loop parameters and its output active power on the energy storage system's support capability; Step 432: Based on the analysis results of steps 41, 42 and 43, identify the main influencing factors and influencing modes of the stability support capability of the overall structure network-controlled energy storage system.

[0053] Furthermore, such as Figure 4 As shown, step 5 of the transient damping-embedded photovoltaic energy storage power station grid-connected stability enhancement control method in the embodiment of the present invention includes: Step 51: Please combine Figure 7 The schematic diagram shown here illustrates the transient damping embedding method for enhancing grid-connected stability of a photovoltaic energy storage power station according to an embodiment of the present invention. Feedforward compensation is performed according to frequency, and the d-axis voltage control reference command of the inner loop of the energy storage converter is adjusted. The adjusted d-axis voltage reference command of the inner loop of the energy storage converter is as follows: (27) in, This is the reference command for the d-axis voltage control of the inner loop of the energy storage converter after adjustment. K es,q The reactive power-voltage droop coefficient of the energy storage system; K es,DThe feedforward compensation coefficient is used for frequency compensation. ω es and ω g These are the angular frequencies of the energy storage system and the power grid, respectively. Q es,ref and Q es These are the reference value and the actual measured value of the reactive power output by the energy storage converter, respectively.

[0054] Step 52: Please combine Figure 4 The flowchart of the photovoltaic energy storage power station grid-connected stability enhancement control method with transient damping embedded in the embodiment of the present invention is shown below. Figure 5 The diagram shown in the embodiment of the present invention illustrates the interaction structure of a photovoltaic energy storage system. Following steps 2 and 3, new inner-loop control admittance models for the photovoltaic and energy storage systems are constructed after adjusting the inner-loop d-axis voltage control reference command of the energy storage converter (using...). , and , A new complex transfer function model for the interaction between photovoltaic energy storage systems and photovoltaic energy storage systems; (28) (29) in, and It can be obtained by calculation according to the methods of equations (13)-(15), (21) and (22); and It can be obtained by calculation according to the methods of equations (17)-(19), (24) and (25); and These are respectively called the complex transfer functions of the interaction between the photovoltaic system and the energy storage system.

[0055] Furthermore, the flowchart of the photovoltaic energy storage power station grid-connected stability enhancement control method with transient damping embedded in the embodiment of the present invention ( Figure 4 Step 6 of the evaluation process assesses the grid-connected stability enhancement effect of the photovoltaic energy storage power station with embedded transient damping: Please refer to... Figure 8 The evaluation process for enhancing the grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in the embodiment of the present invention, as shown in the figure, is carried out according to the following steps: Step 61: Using the results obtained in Step 5, i.e., equations (28) and (29), reconstruct the equivalent Nyquist stability condition of the photovoltaic system, i.e., the transfer function. and transfer function Satisfies the Nyquist stability criterion; Step 62: When the energy storage system compensates for the feedforward coefficient according to the frequency... Kes,D When changes occur, the stability evolution trend of the photovoltaic system is analyzed and judged by combining Bode plots and Nyquist curves, and the feedforward compensation coefficient is evaluated. K es,D It enhances the stability of its grid connection.

[0056] Step 63: Based on the analysis and evaluation results of Step 2, and considering the system stability, dynamic response characteristics, and steady-state characteristics, select the optimal feedforward compensation coefficient. K es,D。

[0057] Example 2: Embodiment 2 of the present invention provides a transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement control system. Please refer to the following... Figure 9 The diagram shows the configuration of a photovoltaic energy storage power station grid-connected stability enhancement control system with embedded transient damping. The grid-connected stability enhancement control system with embedded transient damping described in this embodiment includes the following main modules: Data acquisition and pre-storage module 100: used to acquire and store the input data and corresponding output results required for constructing the interaction influence model of the photovoltaic energy storage system, calculating the Bode plot, Nyquist curve and amplitude-phase stability margin, as well as the data required to demonstrate the grid-connected stability enhancement effect of the photovoltaic energy storage power station; Data preprocessing module 200: used to process the input data acquired by the data acquisition module to obtain preprocessed input data; Photovoltaic energy storage system interaction influence model construction module 300: used to construct a complex transfer function model of the interaction influence of photovoltaic energy storage system based on the preprocessed input data obtained by the data processing module; Bode plot, Nyquist curve and amplitude and phase stability margin calculation module 400: used to draw Bode plot and Nyquist stability curve based on the preprocessed input data obtained by the data processing module, and calculate the amplitude and phase stability margin under different parameters; And the effect output and display module 500: used to display the enhancement effect of the feedforward compensation coefficient according to frequency disturbance on enhancing the grid connection stability of photovoltaic energy storage power station.

[0058] Please refer to the following: Figure 10 The control flowchart of the photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded in the present invention is shown in the embodiment of the present invention. The photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded in the present invention includes the following main process steps: Step 1: Obtain the input data required for the grid-connected stability enhancement control of the photovoltaic energy storage power station with transient damping embedded in it; The input data required for the transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement control system described in this embodiment of the invention includes: the proportional gain and integral gain of all PI controllers (voltage control loop, current control loop, DC voltage control, active power synchronous control, phase-locked loop control); reactive power-voltage droop coefficient, virtual inertia and virtual damping, virtual impedance; grid connection inductance, line impedance, LC filter inductance and capacitance, voltage feedforward control parameters, transient damping coefficient for frequency disturbance compensation, grid rated voltage and frequency, rated DC voltage on the DC side of the photovoltaic system; measured values ​​of filter inductor current, output voltage and output current of the photovoltaic and energy storage systems, measured values ​​of grid point of common coupling frequency and voltage, and measured values ​​of DC voltage on the DC side of the photovoltaic system, etc.

[0059] Step 2: Preprocess the acquired input data; The preprocessing of the acquired input data described in this embodiment of the invention refers to using a low-pass filter to filter and remove noise from the measured values ​​of the photovoltaic energy storage system's filter inductor current, output voltage and current, DC voltage on the DC side of the photovoltaic system, and the frequency and voltage of the grid's point of common coupling.

[0060] Step 3: Based on the preprocessed input data, construct a complex transfer function model of the interaction effects of the photovoltaic energy storage system. The construction of the complex transfer function model of the interaction of photovoltaic energy storage system described in the embodiments of the present invention refers to the construction of models (20), (23), (28) and (29), specifically executed according to steps 200, 300 and 500 of the first aspect of the present invention.

[0061] Step 4: Based on the complex variable transfer function model of interaction constructed in Step 3, plot the Bode plot and Nyquist stability curve, and calculate the magnitude and phase stability margin under different parameters; Step 5: Based on the results obtained in Step 4, optimize the grid-connected stability enhancement parameters of the photovoltaic energy storage system and control it according to the optimal parameters; Step 6: Demonstrate the grid-connected stability enhancement control effect of photovoltaic energy storage power station based on transient damping.

[0062] The embodiments of this invention demonstrate the enhanced grid-connected stability control effect of a photovoltaic energy storage power station based on transient damping embedding, including: displaying the frequency and voltage of the grid's point of common coupling before and after a disturbance; the active and reactive power injected by the photovoltaic energy storage power station into the point of common coupling before and after the disturbance; and comparing the active power, reactive power, frequency (power angle), and voltage curves of the photovoltaic energy storage power station before and after optimizing the light parameters using stability enhancement, thus demonstrating the stability enhancement control effect.

[0063] It is not difficult to understand the control flowchart of the photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded. Figure 10 The first step in the process provides the input data required for the grid-connected stability enhancement control of the photovoltaic energy storage power station with transient damping embedded in it. This is constituted by the grid-connected stability enhancement control system of the photovoltaic energy storage power station with transient damping embedded in it. Figure 9 The data acquisition and storage module 100 obtains the control flow diagram of the photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded in it. Figure 10 The second step of input data preprocessing in the process is constituted by the photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded in it. Figure 9 The data preprocessing module 200 processes the data to obtain the preprocessed input data; the control flowchart of the photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded is shown below. Figure 10 The third step in the process involves constructing a complex transfer function model of the interaction between the photovoltaic energy storage system and the grid-connected stability enhancement control system of the photovoltaic energy storage power station with transient damping embedded in it. Figure 9 The photovoltaic energy storage system interaction influence model construction module 300 is used for calculation; the control flow diagram of the photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded is shown in the figure. Figure 10 The fourth step in the process is to plot the Bode plot and Nyquist stability curve, calculate the amplitude and phase stability margin under different parameters, and the fifth step is to optimize the grid-connected stability enhancement parameters of the photovoltaic energy storage system and control it according to the optimized parameters. This is achieved through a photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded in it. Figure 9 The Bode plot, Nyquist curve, and amplitude-phase stability margin calculation module 400 are used to calculate and plot the control flow diagram of the photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded. Figure 10 Step 6 in the document demonstrates the grid-connected stability enhancement control effect of a photovoltaic energy storage power station based on transient damping. This is achieved through a grid-connected stability enhancement control system for the photovoltaic energy storage power station with embedded transient damping. Figure 9 The effect output and display module 500 is used to demonstrate the results. This application presents a transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement control method. From the perspective of single-input single-output transfer function, it solves the problems of high dimensionality, unclear physical meaning, and difficulty in analyzing the interaction influence and stability domain between subsystems faced by traditional multi-input multi-output state-space models and impedance models. It is more practical, versatile and scalable, and has great significance and high practical value for promoting the consumption of new energy and improving the safety and stability support capability of energy storage and new energy for new power systems. It can be widely used in the fields of new energy and energy storage technology.

[0064] In addition, Embodiment 3 of this application also provides a computing device and computer-readable storage medium for a transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement control system, including: at least one processor and a memory communicatively connected to the at least one processor; wherein, the processor executes the transient damping embedded photovoltaic energy storage power station grid-connected stability enhancement method as described in any one of Embodiments 1 and 2 by calling a computer program stored in the memory.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in it, characterized in that, include: Step 1: Construct grid-connected control strategies for photovoltaic power generation systems and grid-connected control strategies for energy storage systems; Step 2: Construct the inner-loop control admittance model of the photovoltaic energy storage system; Step 3: Construct a complex transfer function model of the interaction effects of the photovoltaic energy storage system; Step 4: Analyze and evaluate the interactive effects on the stability of the photovoltaic energy storage system; Step 5: Construct a method to enhance the grid-connected stability of photovoltaic energy storage power stations with embedded transient damping; Step 6: Evaluate the grid-connected stability enhancement effect of photovoltaic energy storage power stations with embedded transient damping.

2. The method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in it, as described in claim 1, is characterized in that... Step 2 involves constructing the inner-loop control admittance model of the photovoltaic energy storage system, which includes: the inner-loop control admittance model of the grid-connected photovoltaic power generation system and the inner-loop admittance model of the grid-connected energy storage system.

3. The method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in it, as described in claim 1, is characterized in that... Step 3 involves constructing a complex transfer function model of the interaction between the photovoltaic power generation system and the energy storage system, including: ① constructing a complex transfer function model of the interaction between the output power angle of the photovoltaic power generation system, the output power angle of the energy storage system, and the power angle of the grid in the first coordinate system; ② constructing a complex transfer function model of the interaction between the output power angle of the photovoltaic power generation system, the output power angle of the energy storage system, and the power angle of the grid in the second coordinate system; ③ constructing a complex transfer function model considering the influence of the grid power angle on the output power angle of the photovoltaic power generation system, including the role of the energy storage system; and ④ constructing a complex transfer function model considering the influence of the grid power angle on the output power angle of the energy storage system, including the role of the photovoltaic power generation system.

4. The method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded according to claims 1 and 3, characterized in that, The complex transfer function model that considers the influence of the grid power angle, including the role of the energy storage system, on the output power angle of the photovoltaic power generation system, has the following mathematical expression: ， in, This refers to the change in the output power angle of the photovoltaic power generation system. This is the change in the power angle of the power grid. Let be the closed-loop transfer function of the phase-locked loop. and These are two intermediate transfer functions for the photovoltaic system, and their specific expressions are as follows: ， ， in, For the transfer function related to power synchronization control; This is the internal transfer function of the energy storage system. This represents the coupling transfer function from photovoltaics to energy storage; This refers to the internal transfer function of the photovoltaic system. This represents the coupling transfer function from energy storage to photovoltaics; the English term for a phase-locked loop is: Phase Locked Loop. The complex transfer function model that considers the influence of the grid power angle, including the photovoltaic power generation system, on the output power angle of the energy storage system, has the following mathematical expression: ， in, This refers to the change in the output power angle of the energy storage system. and These are two intermediate transfer functions for the energy storage system, and their specific expressions are as follows: ， ， in, Let the transfer function be the phase-locked loop transfer function of the photovoltaic system. This refers to the internal transfer function of the photovoltaic system. This represents the coupling transfer function from energy storage to photovoltaics. This represents the coupling transfer function from photovoltaics to energy storage. This is the internal transfer function of the energy storage system.

5. The method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in it, as described in claim 1, is characterized in that... Step 4, which analyzes and evaluates the interactive effects on the stability of the photovoltaic energy storage system, specifically includes: Step 41. Analyzing and evaluating the stability of the photovoltaic system without the energy storage system; Step 42. Analyzing and evaluating the impact of the energy storage system on the stability of the photovoltaic system; Step 43. Evaluating the impact of the energy storage system on the overall system stability support capability, and analyzing the factors, including the photovoltaic system, that affect the stability support capability of the energy storage system.

6. The method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in it, as described in claim 5, is characterized in that... The analysis and evaluation of the stability of the photovoltaic system without an energy storage system includes the following specific steps: Step 410: Set the positive components of the inner loop control complex admittance model of the grid-controlled energy storage system to zero; Step 411: Construct the small-signal stability conditions for the photovoltaic system, namely: ， Step 412: Analyze the change in grid strength from strong to weak, i.e., when the grid equivalent inductance Lg increases, the phase-locked loop parameters increase, and the photovoltaic system current control loop parameters and DC voltage control parameters increase. By combining Bode plots and Nyquist curves, determine the stability of the photovoltaic system and evaluate the influence trend of the above parameters on its stability; the phase-locked loop parameters refer to... K p,pll and K i,pll These refer to the proportional gain and integral gain of the phase-locked loop (PLL) PI controller; the photovoltaic system current control loop parameters refer to... and These refer to the proportional gain and integral gain of the PI controller in the photovoltaic system's current control loop; the DC voltage control parameters refer to: K p,DC and K i,DC These represent the proportional gain and integral gain of the PI controller in the DC voltage control loop of the photovoltaic system, respectively.

7. The method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in claim 5, characterized in that, The specific steps for analyzing and evaluating the impact of the energy storage system on the stability of the photovoltaic system include: Step 420: Construct and determine the equivalent Nyquist stability condition for the photovoltaic system, i.e., the open-loop transfer function. and open-loop transfer function ( G pv (s)+ G in,es (s)) f PSC (s) satisfies the Nyquist stability criterion; Step 421: When analyzing the changes in voltage loop control parameters, virtual impedance parameters, current loop control parameters, and voltage feedforward control parameters of the energy storage system, combine Bode plots and Nyquist curves to analyze and judge the stability of the photovoltaic system and evaluate the influence trend of the above parameters on its stability.

8. The method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in claim 5, characterized in that, The assessment of the impact of the energy storage system on the overall system stability, and the analysis of factors affecting the stability support capability of the energy storage system, including photovoltaic systems, include the following specific steps: Step 430: Based on the stability criterion established in Step 420 in the analysis and evaluation of the impact of the energy storage system on the stability of the photovoltaic system, and in combination with Bode plots and Nyquist curves, analyze and evaluate the impact of changes in the active power synchronization control loop parameters of the energy storage system on the stability support capability of the grid-controlled energy storage system; the control loop parameters include: virtual inertia and virtual damping; Step 431: Combining Bode plots and Nyquist curves, analyze and evaluate the impact of the photovoltaic system's phase-locked loop parameters and its output active power on the energy storage system's support capability; Step 432: Based on the analysis results of steps 41, 42 and 43, identify the main influencing factors and influencing modes of the stability support capability of the overall structure network-controlled energy storage system.

9. The method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in it, as described in claim 1, is characterized in that... Step 5, the method for enhancing the grid-connected stability of a photovoltaic energy storage power station with embedded transient damping, specifically includes: Step 51: Perform feedforward compensation according to frequency, and adjust the d-axis voltage control reference command of the inner loop of the energy storage converter; the adjusted d-axis voltage reference command of the inner loop of the energy storage converter is as follows: ， in, To adjust the reference command for the d-axis voltage control of the inner loop of the energy storage converter. This is the reference command for the d-axis voltage control of the inner loop of the energy storage converter after adjustment. K es,q The reactive power-voltage droop coefficient of the energy storage system; K es,D The feedforward compensation coefficient is used for frequency-based compensation. ω es For the angular frequency of the energy storage system, ω g The angular frequency of the power grid; Q es,ref This provides a reference value for the reactive power output of the energy storage converter. Q es The actual measured value of reactive power output by the energy storage converter; Step 52: Following Step 2 and Step 3, construct a new inner-loop control admittance model for the photovoltaic energy storage system after adjusting the inner-loop d-axis voltage control reference command of the energy storage converter, and a new complex transfer function model of the interaction between the photovoltaic energy storage system and the photovoltaic energy storage system.

10. The method for enhancing grid-connected stability of a photovoltaic energy storage power station with transient damping embedded in it, as described in claim 1, is characterized in that... Step 6 evaluates the grid-connected stability enhancement effect of the photovoltaic energy storage power station with embedded transient damping: Step 61: Using the results obtained in Step 5, reconstruct the equivalent Nyquist stability conditions for the photovoltaic system, i.e., the transfer function. and transfer function Satisfies the Nyquist stability criterion; Step 62: When the energy storage system compensates for the feedforward coefficient according to the frequency... K es,D When changes occur, the stability evolution trend of the photovoltaic system is analyzed and judged by combining Bode plots and Nyquist curves, and the feedforward compensation coefficient is evaluated. K es,D The effect of enhancing its grid connection stability; Step 63: Based on the analysis and evaluation results of Step 2, and considering the system stability, dynamic response characteristics, and steady-state characteristics, select the optimal feedforward compensation coefficient. K es,D .

11. A transient damping-embedded grid-connected stability enhancement control system for photovoltaic energy storage power stations, characterized in that, include: Data acquisition and pre-storage module: used to acquire and store the input data and corresponding output results required to build the interaction influence model of photovoltaic energy storage system, calculate Bode plot, Nyquist curve and amplitude-phase stability margin, as well as the data required to demonstrate the grid connection stability enhancement effect of photovoltaic energy storage power station; Data preprocessing module: used to process the input data acquired by the data acquisition module to obtain preprocessed input data; Photovoltaic energy storage system interaction influence model construction module: used to construct a complex transfer function model of the interaction influence of photovoltaic energy storage system based on the preprocessed input data obtained by the data processing module; Bode plot, Nyquist curve and amplitude and phase stability margin calculation module: used to draw Bode plot and Nyquist stability curve based on the preprocessed input data obtained from the data processing module, and calculate the amplitude and phase stability margin under different parameters; And the effect output and display module: used to demonstrate the enhancement effect of the feedforward compensation coefficient based on frequency disturbance on the grid connection stability of photovoltaic energy storage power station.

12. The photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded according to claim 11, characterized in that, The transient damping-embedded photovoltaic energy storage power station grid-connected stability enhancement control system includes the following process steps: Step 1: Obtain the input data required to provide the grid-connected stability enhancement control system for transient damping embedded in photovoltaic energy storage power stations; Step 2: Preprocess the acquired input data; Step 3: Based on the preprocessed input data, construct a complex transfer function model of the interaction effects of the photovoltaic energy storage system. Step 4: Based on the complex variable transfer function model of interaction constructed in Step 3, plot the Bode plot and Nyquist stability curve, and calculate the magnitude and phase stability margin under different parameters; Step 5: Based on the results obtained in Step 4, optimize the grid-connected stability enhancement parameters of the photovoltaic energy storage system and control it according to the optimal parameters; Step 6: Demonstrate the grid-connected stability enhancement control effect of photovoltaic energy storage power station based on transient damping.

13. The photovoltaic energy storage power station grid-connected stability enhancement control system with transient damping embedded according to claim 12, characterized in that, The first step of embedding transient damping into the grid-connected stability enhancement control system of the photovoltaic energy storage power station requires the following input data: the proportional gain and integral gain of the PI controller corresponding to each control link in the photovoltaic energy storage system; reactive power-voltage droop coefficient, virtual inertia and virtual damping, virtual impedance; grid connection inductance, line impedance, LC filter inductance and capacitance, voltage feedforward control parameters, transient damping coefficient for frequency disturbance compensation, grid rated voltage and frequency, rated DC voltage on the DC side of the photovoltaic system; measured values ​​of filter inductor current, output voltage and output current of the photovoltaic and energy storage systems, measured values ​​of grid point of common coupling frequency and voltage, and measured values ​​of DC voltage on the DC side of the photovoltaic system, etc. The second step, preprocessing the acquired input data, refers to using a low-pass filter to filter and remove noise from the measured values ​​of the photovoltaic energy storage system's filter inductor current, output voltage and current, DC voltage on the DC side of the photovoltaic system, and the frequency and voltage of the grid's point of common coupling. The third step, constructing a complex transfer function model of the interaction between the photovoltaic energy storage system, is specifically performed according to steps 2, 3, and 5 of the first aspect of this invention. The sixth step demonstrates the grid-connected stability enhancement control effect of the photovoltaic energy storage power station based on transient damping embedding, including: displaying the frequency and voltage of the grid's point of common coupling before and after the disturbance; the active and reactive power injected by the photovoltaic energy storage power station into the point of common coupling before and after the disturbance; and the active power, reactive power, frequency, and voltage curves of the photovoltaic energy storage power station before and after using the stability enhancement optimization of light parameters, comparing and demonstrating the stability enhancement control effect.

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