Control parameter adjustment method, device and equipment for suppressing overvoltage of grid-connected point

Abstract

The invention provides a control parameter adjusting method, device and equipment for suppressing overvoltage of a grid-connected point, and belongs to the field of data processing. The method comprises the following steps: acquiring a control parameter of a PLL (Phase Locked Loop) of the VSC and a power grid voltage value and a current instruction value of the VSC in each stage; according to the control parameters, the power grid voltage value of the first stage and the current instruction value, a PLL differential equation is constructed in a staged mode, an approximate analytical solution is solved, and a grid-connected point overvoltage estimated value is obtained based on the approximate analytical solution obtained in the last stage; and adjusting a control parameter according to the grid-connected point overvoltage estimated value so as to suppress the grid-connected point overvoltage. The function of suppressing the transient overvoltage risk of the system based on adjustment of the control parameters can be realized, and the stability of the system is improved.

Description

Technical Field

[0001] This application belongs to the field of data processing, and specifically relates to a method, apparatus and equipment for adjusting control parameters to suppress overvoltage at grid connection points. Background Technology

[0002] Voltage source converters (VSCs) are key power electronic devices for grid connection of new energy sources, and their dynamic control characteristics directly affect the transient behavior of the power grid. When a grid fault occurs, there is a millisecond-level delay in the switching process of the VSC control strategy, which can trigger transient overvoltages in the grid and potentially lead to the cascading disconnection of generating units from the grid.

[0003] Existing research on calculating overvoltage levels using empirical formulas and other methods has two limitations: first, the models do not consider the switching delay before the VSC enters the low-voltage ride-through phase; second, they ignore the impact of the phase-locked loop (PLL) dynamic response after the voltage phase jump. In fact, when a fault occurs, there is a response delay when the VSC switches from normal operation mode to low-voltage ride-through mode. During this time, the system state variables are in a rapid divergence process, which significantly affects the subsequent calculation of the overvoltage level. Furthermore, current schemes do not consider the influence of control parameters on the overvoltage level, therefore they cannot suppress the risk of transient overvoltage based on control parameters. Summary of the Invention

[0004] This application provides a method, apparatus, and device for adjusting control parameters to suppress grid connection point overvoltage, thereby improving the accuracy of calculating the grid connection point overvoltage level and realizing the function of suppressing system transient overvoltage risk based on adjusting control parameters, thus improving system stability.

[0005] This application provides a method for adjusting control parameters to suppress overvoltage at the grid connection point, including: The control parameters of the phase-locked loop (PLL) of the VSC are obtained, as well as the grid voltage and current command values ​​of the VSC in each stage. The PLL includes four stages: the first stage of steady-state operation before the AC fault occurs, the second stage of low voltage ride-through (LVRT) strategy not being activated after the AC fault occurs, the third stage of LVRT strategy activation, and the fourth stage of LVRT strategy not being deactivated after the fault is cleared. The first differential equation of the PLL is determined based on the control parameters, the grid voltage value and current command value of the first stage, and the steady-state phase and steady-state frequency of the PLL are obtained by solving the first differential equation. Based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, the second differential equation is obtained, and the approximate analytical solution of the second differential equation is solved. Based on the grid voltage and current command values ​​of the third stage and the first differential equation, a third differential equation is obtained, and the third differential equation is solved based on the approximate analytical solution of the second differential equation to obtain the approximate analytical solution of the third differential equation. The estimated overvoltage at the grid connection point is obtained based on the grid voltage and current command values ​​in the fourth stage and the approximate analytical solution of the third differential equation. The control parameters are adjusted according to the estimated overvoltage at the grid connection point to suppress the overvoltage at the grid connection point.

[0006] According to the control parameter adjustment method for suppressing overvoltage at the grid connection point provided in this application, the step of obtaining a second differential equation based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, and solving the approximate analytical solution of the second differential equation, includes: determining the steady-state phase as the initial phase of the second stage; obtaining the initial frequency of the second stage based on the control equation of the PLL and the steady-state frequency; replacing the initial phase of the first stage in the first differential equation with the initial phase of the second stage, and replacing the grid voltage and current command values ​​of the first stage in the first differential equation with the grid voltage and current command values ​​of the second stage, to obtain the second differential equation; setting preset parameters based on the second differential equation, and simplifying the second differential equation based on the preset parameters to obtain a simplified second differential equation; and analyzing the simplified second differential equation based on the initial phase and the initial frequency of the second stage to obtain an approximate analytical solution of the second differential equation.

[0007] According to the control parameter adjustment method for suppressing overvoltage at the grid connection point provided in this application, the step of obtaining a third differential equation based on the grid voltage and current command values ​​of the third stage and the first differential equation, and solving the third differential equation based on the approximate analytical solution of the second differential equation to obtain an approximate analytical solution of the third differential equation includes: replacing the grid voltage and current command values ​​of the first stage in the first differential equation with the grid voltage and current command values ​​of the third stage to obtain the third differential equation; solving the third differential equation to obtain a steady-state solution of the third differential equation; simplifying the third differential equation based on the steady-state solution of the third differential equation to obtain a simplified third differential equation; obtaining the final phase value and final frequency value of the second stage based on the approximate analytical solution of the second differential equation; determining the final phase value of the second stage as the initial phase of the third stage; obtaining the frequency mutation amount of the third stage; determining the initial frequency of the third stage based on the final frequency value of the second stage and the frequency mutation amount of the third stage; and analyzing the simplified third differential equation based on the initial phase and the initial frequency to obtain an approximate analytical solution of the third differential equation.

[0008] According to the control parameter adjustment method for suppressing overvoltage at the grid connection point provided in this application, the step of analyzing the third differential simplified equation based on the initial phase and the initial frequency to obtain an approximate analytical solution of the third differential equation includes: decomposing the third differential simplified equation into an outer layer equation describing the slowly varying main characteristics of the system and an inner layer equation describing the rapidly varying boundary layer characteristics of the system; solving the outer layer equation to obtain a first approximate solution, and solving the inner layer equation to obtain a second approximate solution; and combining the first approximate solution and the second approximate solution using a matched asymptotic expansion technique to obtain an approximate analytical solution of the third differential equation.

[0009] According to the control parameter adjustment method for suppressing grid-connected point overvoltage provided in this application, the step of obtaining the grid-connected point overvoltage prediction value based on the grid voltage and current command values ​​of the fourth stage and the approximate analytical solution of the third differential equation includes: replacing the grid voltage and current command values ​​of the first stage in the first differential equation with the grid voltage and current command values ​​of the fourth stage to obtain the fourth differential equation; obtaining the final phase value and final frequency value of the third stage based on the approximate analytical solution of the third differential equation; determining the final phase value of the third stage as the initial phase of the fourth stage; obtaining the frequency mutation amount of the fourth stage; determining the initial frequency of the fourth stage based on the final frequency value of the third stage and the frequency mutation amount of the fourth stage; solving the fourth differential equation based on the initial phase and the initial frequency of the fourth stage to obtain the phase value of the fourth stage; and obtaining the grid-connected point overvoltage prediction value based on the phase value of the fourth stage.

[0010] According to the control parameter adjustment method for suppressing grid connection point overvoltage provided in this application, the step of obtaining the grid connection point overvoltage estimate based on the phase value of the fourth stage includes: obtaining the correlation between the grid connection point voltage and the phase-locked loop phase based on the voltage vector relationship; and obtaining the grid connection point overvoltage estimate based on the phase value of the fourth stage and the correlation relationship.

[0011] This application also provides a control parameter optimization device for suppressing overvoltage at the grid connection point, comprising: The acquisition unit is used to acquire the control parameters of the PLL of the VSC, as well as the grid voltage value and current command value of the VSC in each stage; wherein, the PLL includes four stages, namely the first stage of steady-state operation before the occurrence of AC fault, the second stage of low voltage ride-through LVRT strategy not being put into operation after the occurrence of AC fault, the third stage of LVRT strategy being started, and the fourth stage of LVRT strategy not being withdrawn after the fault is cleared. The first solving unit is used to determine the first differential equation of the PLL based on the control parameters, the grid voltage value and current command value of the first stage, and solve the first differential equation to obtain the steady-state phase and steady-state frequency of the PLL. The second solving unit is used to obtain the second differential equation based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency and the first differential equation, and to solve the approximate analytical solution of the second differential equation. The third solution unit is used to obtain the third differential equation based on the grid voltage and current command values ​​of the third stage and the first differential equation, and to solve the third differential equation based on the approximate analytical solution of the second differential equation to obtain the approximate analytical solution of the third differential equation. The fourth solution unit is used to obtain the estimated overvoltage value at the grid connection point based on the grid voltage and current command values ​​in the fourth stage and the approximate analytical solution of the third differential equation. An adjustment unit is used to adjust the control parameters according to the estimated overvoltage at the grid connection point in order to suppress the overvoltage at the grid connection point.

[0012] This application also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the control parameter optimization method for suppressing grid connection point overvoltage as described above.

[0013] This application also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the control parameter optimization method for suppressing overvoltage at the grid connection point as described above.

[0014] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the control parameter optimization method for suppressing overvoltage at the grid connection point as described above.

[0015] According to the control parameter adjustment method, apparatus, and equipment for suppressing grid connection point overvoltage provided in this application, the control parameters of the PLL of the VSC are first obtained. Then, based on the control parameters, the grid voltage value and current command value of the first stage, the first differential equation of the PLL is determined, and the first differential equation is solved to obtain the steady-state phase and steady-state frequency of the PLL. Next, based on the grid voltage value and current command value of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, a second differential equation is obtained, and the approximate analytical solution of the second differential equation is solved. Then, based on the grid voltage value and current command value of the third stage and the first differential equation, a third differential equation is obtained, and the approximate analytical solution of the second differential equation is solved to obtain the approximate analytical solution of the third differential equation. Next, based on the grid voltage value and current command value of the fourth stage and the approximate analytical solution of the third differential equation, the grid connection point overvoltage prediction value is obtained. Finally, the control parameters are adjusted based on the grid connection point overvoltage prediction value to suppress the grid connection point overvoltage. This scheme constructs PLL differential equations in stages and solves approximate analytical solutions. Combined with the overvoltage prediction at the grid connection point, the control parameters are dynamically adjusted to accurately suppress transient overvoltage at the grid connection point and enhance the operational stability of the VSC grid connection system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is one of the flowcharts illustrating the control parameter adjustment method for suppressing overvoltage at the grid connection point provided in this application.

[0018] Figure 2 This is the VSC control structure diagram provided in this application.

[0019] Figure 3 This is a vector diagram of current and voltage provided in this application.

[0020] Figure 4 This is the second flowchart illustrating the method for adjusting control parameters to suppress overvoltage at the grid connection point, as requested in the application.

[0021] Figure 5This is a schematic diagram of the transient overvoltage 1.3pu isosurface after a short-circuit fault provided in this application.

[0022] Figure 6 The curves showing the voltage changes at the multi-stage grid connection point when the first control parameter provided in this application is used.

[0023] Figure 7 The voltage change curve at the multi-stage grid connection point is the second control parameter provided in this application.

[0024] Figure 8 The voltage change curve at the multi-stage grid connection point is the third control parameter provided in this application.

[0025] Figure 9 This is the multi-stage grid connection point voltage change curve when the fourth control parameter provided in this application is applied.

[0026] Figure 10 This is the multi-stage grid connection point voltage change curve when the fifth control parameter provided in this application is applied.

[0027] Figure 11 This is the multi-stage grid connection point voltage change curve when the sixth control parameter provided in this application is applied.

[0028] Figure 12 This is the multi-stage grid connection point voltage change curve when the seventh control parameter provided in this application is applied.

[0029] Figure 13 This is a block diagram of the functional units of the control parameter adjustment device for suppressing overvoltage at the grid connection point provided in this application.

[0030] Figure 14 This is a schematic diagram of the structure of the electronic device provided in this application. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0033] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0034] Current research on calculating overvoltage levels using empirical formulas and other methods fails to consider the switching delay before the VSC enters the low-voltage ride-through phase, and neglects the impact of the PLL's dynamic response after a voltage phase transition. Furthermore, current solutions do not account for the influence of control parameters on overvoltage levels, thus failing to suppress system transient overvoltage risks based on control parameters.

[0035] To address the aforementioned problems, embodiments of this application provide a method, apparatus, and device for adjusting control parameters to suppress overvoltage at grid connection points. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0036] Please see Figure 1 , Figure 1 This is one of the flowcharts of the control parameter adjustment method for suppressing grid connection point overvoltage provided in this application. The control parameter adjustment method for suppressing grid connection point overvoltage includes the following steps.

[0037] S101, obtain the control parameters of the PLL of the VSC, as well as the grid voltage value and current command value of the VSC at each stage.

[0038] Under normal operating conditions, the converter employs a constant voltage outer loop control strategy. When a short-circuit fault occurs, the converter detects that the grid connection point voltage is lower than the activation value of the low-voltage recovery (LVRT) strategy and enters the active power recovery (LVRT) phase. After the fault is cleared, the converter detects that the grid connection point voltage has returned to normal, exits the LVRT strategy, and enters the active power recovery phase. Due to the time delay in switching the outer loop control strategy, there are switching delay phases both before entering LVRT and after fault clearing. Therefore, the PLL can include four phases: the first phase of steady-state operation before the AC fault occurs, the second phase of LVRT strategy not being activated after the AC fault occurs, the third phase of LVRT strategy activation, and the fourth phase of LVRT strategy not exiting after the fault is cleared.

[0039] Please see Figure 2 ,Depend on Figure 2 It can be seen that VSC includes an outer loop, an inner loop, and a phase-locked loop. Where P is the active power output value of VSC; P in For VSC DC-side active power; C dc For VSC DC side capacitor; U dc U is the DC-side capacitor voltage; dc,ref This is the commanded value for the DC-side capacitor voltage; U t This refers to the voltage at the grid connection point, or the point of common coupling (PCC); U t,ref The voltage command value at PCC; I n VSC rated current; I d and I q These are the d-axis and q-axis components of the filter line current, respectively; I d,ref and I q,ref These are the d-axis and q-axis current command values, respectively; K is the reactive current adjustment coefficient; I d LVRT U is the active current when VSC enters LVRT; d and U q The voltage at PCC (U) t The d-axis and q-axis components of U; x and U y The voltage at PCC (U) t The x-axis and y-axis components of ). For the phase of the PLL; U g This is the mains voltage; its normal value is U. n The fault value is U f .

[0040] The control parameters of this PLL can include proportional-integral (PI) control parameters and d-axis and q-axis current command values. The PI control parameters include the proportional coefficient k. p5and integral coefficient k i5 In the first stage, the grid voltage value is the voltage value under normal operating conditions, and the current command value is the current value under normal operating conditions, i.e., I. d and I q The grid voltage value in the second stage is the fault voltage U. f At this point, the current command value is the initial current value for this stage, i.e., I. d0 and I q0 The grid voltage value in the third stage is the fault value U. f The current command value at this time is I. d,ref and I q,ref In the fourth stage, the grid voltage is the normal voltage value, and the current command value is I. d,ref and I q,ref .

[0041] S102, determine the first differential equation of the PLL based on the control parameters, the grid voltage value and current command value of the first stage, and solve the first differential equation to obtain the steady-state phase and steady-state frequency of the PLL.

[0042] The control equation for the phase-locked loop is shown in equation (1).

[0043] (1) in, The instantaneous frequency of the PLL. The rate of change of the PLL phase error. This represents the phase error of the PLL. U q It's U t The q-axis component can be calculated using equation (2).

[0044] (2) Substituting equation (2) into equation (1), we can obtain the information about the PLL phase. The second-order differential equation, i.e. the first differential equation, is shown in equation (3).

[0045] (3) Among them, L L R is the inductance value of the filter line. L This represents the resistance value of the filter circuit.

[0046] During the steady-state operation phase before the failure occurs, i.e., the first stage. During this stage, the steady-state solutions of the phase-locked loop phase and frequency under normal operating conditions can be obtained according to equation (3), namely: (4) in, For steady-state phase, This is the steady-state frequency.

[0047] S103. Based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, a second differential equation is obtained, and an approximate analytical solution to the second differential equation is solved.

[0048] S104. Based on the grid voltage and current command values ​​of the third stage and the first differential equation, a third differential equation is obtained, and the third differential equation is solved based on the approximate analytical solution of the second differential equation to obtain the approximate analytical solution of the third differential equation.

[0049] S105, based on the grid voltage and current command values ​​of the fourth stage and the approximate analytical solution of the third differential equation, obtain the estimated overvoltage value at the grid connection point.

[0050] S106, adjust the control parameters according to the estimated overvoltage at the grid connection point to suppress the overvoltage at the grid connection point.

[0051] By changing different control parameters, the influence trend of each control parameter on the transient overvoltage level can be analyzed, and control parameters that are beneficial to suppressing overvoltage can be obtained.

[0052] As can be seen, in this embodiment, by constructing the PLL differential equation in stages and solving the approximate analytical solution, and by dynamically adjusting the control parameters in combination with the overvoltage prediction at the grid connection point, the transient overvoltage at the grid connection point can be accurately suppressed, thereby enhancing the operational stability of the VSC grid connection system.

[0053] In one possible embodiment, the step of obtaining a second differential equation based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, and solving the approximate analytical solution of the second differential equation, includes: determining the steady-state phase as the initial phase of the second stage; obtaining the initial frequency of the second stage based on the control equation of the PLL and the steady-state frequency; replacing the initial phase of the first stage in the first differential equation with the initial phase of the second stage, and replacing the grid voltage and current command values ​​of the first stage in the first differential equation with the grid voltage and current command values ​​of the second stage, to obtain the second differential equation; setting preset parameters based on the second differential equation, and simplifying the second differential equation based on the preset parameters to obtain a second simplified differential equation; and analyzing the second simplified differential equation based on the initial phase and initial frequency of the second stage to obtain an approximate analytical solution of the second differential equation.

[0054] In the second stage, which is the handover delay phase after a fault occurs, During this stage, the grid voltage Ug The value suddenly dropped to the fault value U. f This often leads to Where ω0 is the fundamental angular frequency of the power grid. Therefore, the steady-state solution of the phase-locked loop does not exist, leading to phase divergence.

[0055] At the initial moment of the second stage, since the PLL phase does not change abruptly, the initial phase is equal to the phase solution of the first stage. , recorded as However, the phase frequency changed abruptly, from the initial frequency... The frequency is no longer 0 in the steady state phase, but needs to be calculated according to equations (1) and (2), denoted as... .

[0056] (5) At this point, simplifying equation (3), we can reduce the value of equation (3) to 1. Replace with the initial value of this stage. , will the grid voltage U g Replace with fault value U f and I d and I q Replace with the initial value I for this stage. d0 and I q0 The second differential equation is obtained: (6) Set preset parameters K1 and K2, and let (7) Equation (6) can then be simplified to the second differential simplified equation: (8) The approximate analytical expressions for the phase-locked loop phase and frequency during the switching delay stage after the fault can be obtained according to equation (8), namely: (9) in, This refers to the phase value of the second stage. This represents the frequency value for the second stage. This represents the phase value for the second stage.

[0057] It is evident that this scheme, by using the steady-state phase as the initial phase of the second stage, obtaining the initial frequency of the second stage based on the PLL control equation and steady-state frequency, replacing the corresponding grid voltage and current parameters, and simplifying the approximate analytical solution of the second differential equation, can improve the accuracy of PLL dynamic response analysis during the switching delay stage after a fault, provide a reliable basis for subsequent overvoltage prediction at the grid connection point, and thus enhance the pertinence and effectiveness of overvoltage suppression.

[0058] In one possible embodiment, the step of obtaining a third differential equation based on the grid voltage and current command values ​​of the third stage and the first differential equation, and solving the third differential equation based on the approximate analytical solution of the second differential equation to obtain an approximate analytical solution of the third differential equation includes: replacing the grid voltage and current command values ​​of the first stage in the first differential equation with the grid voltage and current command values ​​of the third stage to obtain the third differential equation; solving the third differential equation to obtain a steady-state solution of the third differential equation; simplifying the third differential equation based on the steady-state solution of the third differential equation to obtain a simplified third differential equation; obtaining the final phase value and final frequency value of the second stage based on the approximate analytical solution of the second differential equation; determining the final phase value of the second stage as the initial phase of the third stage; obtaining the frequency mutation amount of the third stage; determining the initial frequency of the third stage based on the final frequency value of the second stage and the frequency mutation amount of the third stage; and analyzing the simplified third differential equation based on the initial phase and the initial frequency to obtain an approximate analytical solution of the third differential equation.

[0059] In the low-voltage ride-through phase, i.e., the third phase, During this phase, the low-voltage ride-through strategy is activated, and the commanded values ​​for the d-axis and q-axis currents are determined according to the given values ​​of the low-voltage ride-through strategy, which are Id and Iq, respectively. d,ref and I q,ref .

[0060] At the initial moment of the third stage, since the PLL phase does not undergo abrupt changes, the phase at the initial moment of the third stage is equal to the final phase value of the second stage. , recorded as However, the phase frequency changed abruptly; the frequency at the initial moment of the third stage was not the final value of the frequency in the previous stage. Instead, the mutation amount needs to be added to the final frequency value of the previous stage, denoted as... .

[0061] (10) At this point, I in equation (3) d and I q Replace with low-through-current command value I d,ref and I q,ref , will the grid voltage U g Replace with fault value U f The third differential equation is obtained: (11) The steady-state solution of this equation for: (12) The differential equation contains nonlinear coefficient terms. and The nonlinear coefficient term in the steady-state solution The Taylor expansion is extended to the second order, i.e.: (13) Equation (11) can be rearranged into a simplified equation based on the system structure parameters and VSC control parameters, i.e., the simplified third differential equation is as follows: (14) Where a, b, c, d, and e are coefficients used to simplify the equations, and are constants related to the system structural parameters and VSC control parameters, respectively. f is a constant. The system structural parameters may include parameters such as resistance R and reactance X, and the VSC control parameters may include parameters such as k. p5 k i5 I dref I qref Parameters such as these.

[0062] In one possible embodiment, the step of analyzing the third differential simplified equation based on the initial phase and the initial frequency to obtain an approximate analytical solution to the third differential equation includes: decomposing the third differential simplified equation into an outer layer equation describing the slowly varying main characteristics of the system and an inner layer equation describing the rapidly varying boundary layer characteristics of the system; solving the outer layer equation to obtain a first approximate solution, and solving the inner layer equation to obtain a second approximate solution; and combining the first approximate solution and the second approximate solution using a matched asymptotic expansion technique to obtain an approximate analytical solution to the third differential equation.

[0063] The third simplified differential equation originates from the dynamic response analysis of the PLL after the LVRT is put into operation. During this stage, the system exhibits both slow-changing dynamic characteristics dominated by grid voltage recovery and PI control parameter adjustment, and fast-changing boundary layer characteristics caused by control switching transients and instantaneous coupling of line impedance. Directly solving the complete nonlinear differential equation can easily lead to analytical complexity or insufficient accuracy due to coupling relationships. Therefore, equation decomposition allows for focusing on the core influencing factors of different dynamic characteristics. The outer equation can isolate fast-changing disturbances and focus on describing the main evolution trend of the system during this stage. The solution process can incorporate ω0 and R... L L L Parameters such as these ensure that the first approximate solution reflects the basic laws of PLL phase tracking. The inner layer equations can accurately capture the rapid transient changes within the boundary layer, avoiding excessive deviation between the analytical solution and the actual dynamic response due to neglecting rapid change characteristics. When solving, the initial phase and initial frequency of this stage can be substituted to ensure the validity of the boundary conditions of the second approximate solution.

[0064] The Method of Matched Asymptotic Expansions (MMAE), as an efficient method for solving singular perturbation problems, can smoothly connect the first and second approximate solutions at different scales. The combined approximate analytical solution can fully integrate the influence of slowly varying host characteristics and rapidly varying boundary layer characteristics, thus avoiding the complex calculations of directly solving nonlinear differential equations while ensuring analytical accuracy. The final unified approximate analytical solution, which is consistently valid throughout the entire time domain and is the approximate analytical solution of the third differential equation, is shown in the following equation: (15) As can be seen, in this embodiment, by replacing the grid voltage and current command values ​​of the third stage to construct the third differential equation and simplifying it by combining its steady-state solution, the initial phase and initial frequency of the third stage are determined by taking the final phase value and frequency value of the second stage, and then obtaining the approximate analytical solution of the third differential equation by decomposing the outer and inner equations, solving and combining the approximate solutions, the accuracy and efficiency of the dynamic response analysis of the phase-locked loop during the low voltage ride-through stage can be improved, providing a reliable theoretical basis for the subsequent overvoltage prediction at the grid connection point, thereby enhancing the transient operation stability of the new energy grid-connected system.

[0065] In one possible embodiment, obtaining the grid connection point overvoltage estimate based on the grid voltage and current command values ​​of the fourth stage and the approximate analytical solution of the third differential equation includes: replacing the grid voltage and current command values ​​of the first stage in the first differential equation with the grid voltage and current command values ​​of the fourth stage to obtain the fourth differential equation; obtaining the final phase value and final frequency value of the third stage based on the approximate analytical solution of the third differential equation; determining the final phase value of the third stage as the initial phase of the fourth stage; obtaining the frequency mutation amount of the fourth stage; determining the initial frequency of the fourth stage based on the final frequency value of the third stage and the frequency mutation amount of the fourth stage; solving the fourth differential equation based on the initial phase and the initial frequency of the fourth stage to obtain the phase value of the fourth stage; and obtaining the grid connection point overvoltage estimate based on the phase value of the fourth stage.

[0066] The fourth stage is the handover delay phase after fault clearance. Upon entering this stage, the grid voltage changes from the fault value U. f Restored to normal value U n However, due to the control strategy switching delay, the command values ​​for the d-axis and q-axis currents are still given according to the low-voltage ride-through strategy, which are I... d,ref and I q,ref .

[0067] At the initial moment of the fourth stage, since the PLL phase does not undergo abrupt changes, the initial phase is equal to the final phase value of the third stage. , recorded as However, the phase frequency changed abruptly; the frequency at the initial moment was not the final value of the frequency in the previous stage. Instead, the mutation amount needs to be added to the final frequency value of the previous stage, denoted as... .

[0068] (16) At this point, I in equation (3) d and I q Replace with low-through-current command value I d,ref and I q,ref , will the grid voltage U g Replace with fault value U n This yields the fourth differential equation. Then, by solving the fourth differential equation using the initial frequency and initial phase of the fourth stage, the phase value of the fourth stage is obtained. This solution process can be referenced from the solution process of the aforementioned third differential equation.

[0069] After the fault is cleared, due to the control switching delay, a large reactive power support current is continuously output, resulting in excess reactive power and transient overvoltage. The voltage value increases significantly at the moment the fault is cleared, and the approximate analytical value of the transient overvoltage at the moment of fault clearing can be obtained based on the relationship between the phase-locked loop phase and the grid connection point voltage.

[0070] In one possible embodiment, obtaining the grid connection point overvoltage estimate based on the phase value of the fourth stage includes: obtaining the correlation between the grid connection point voltage and the phase-locked loop phase based on the voltage vector relationship; and obtaining the grid connection point overvoltage estimate based on the phase value of the fourth stage and the correlation relationship. Among them, based on Figure 4 It can be seen that the voltage at the grid connection point satisfies the following voltage vector relationship: (17) Where I is the transmission line current and Z is the equivalent impedance of the transmission line.

[0071] (18) in, This represents the phase value of the fourth stage. Substituting equation (18) into equation (17), we obtain the expression for the overvoltage at the grid connection point after fault clearance: (19) Among them, U z It is the voltage drop on the transmission line.

[0072] As can be seen, in this embodiment, the fourth differential equation is obtained by replacing the grid voltage and current command values ​​in the fourth stage. The initial phase and initial frequency of the fourth stage are determined based on the final values ​​of the phase and frequency in the third stage to obtain the phase value of this stage. Then, the grid connection point voltage and phase-locked loop phase correlation established by the voltage vector relationship are combined to obtain the grid connection point overvoltage prediction value. This can improve the accuracy and real-time performance of the grid connection point overvoltage prediction in the post-fault recovery stage, and enhance the safety of the transient operation of the new energy grid connection system and the pertinence of the control measures.

[0073] The overall process of this plan can be found in [reference]. Figure 4 As shown, this scheme can be roughly divided into four steps, namely: Stage I: steady-state operation stage, calculating the steady-state phase and frequency of the phase-locked loop; Stage II: switching delay stage after fault occurrence, initializing the phase and frequency of the phase-locked loop, simplifying the second-order differential equation of the PLL, and finding the approximate analytical solution of the simplified second-order differential equation; Stage III: low-voltage ride-through stage: initializing the phase and frequency of the phase-locked loop, and finding the approximate analytical solution of the second-order differential equation of the PLL based on the singular perturbation method; Stage IV: switching delay stage after fault clearance, initializing the phase and frequency of the phase-locked loop, obtaining the relationship between the grid connection point voltage and the phase-locked loop phase based on the voltage vector relationship, and calculating the transient overvoltage level.

[0074] Since the transient overvoltage level of a typical renewable energy power plant is limited to no more than 1.3 pu, this factor needs to be considered when constraining control parameters. The aforementioned scheme yields the result in a three-dimensional parameter coordinate system. The isosurface of the transient overvoltage critical condition, such as Figure 5 As shown, it can be seen that when the q-axis current command value increases, the transient overvoltage level also increases because the q-axis current provides reactive power support, which worsens the transient overvoltage level. When the q-axis current remains constant, increasing the PLL bandwidth also increases the transient overvoltage level. Therefore, the current control parameters can be adjusted based on the grid connection point overvoltage prediction obtained from the current control parameters. For example, when the transient overvoltage level is high, the q-axis current command value can be reduced.

[0075] To further verify the relevant conclusions, simulation verification was performed in RTLAB / Simulink, and the simulation parameters are shown in Table 1. The simulation scenario was set as follows: a short-circuit fault occurs from 0 to 0.1 seconds, and the fault ends after 0.2 seconds. The switching delay time of the converter's control strategy is 50 ms at both the fault occurrence and fault end.

[0076] Table 1: Among them, S base It is the baseline capacity, U base It is the reference voltage, k poc k is the outer ring proportionality coefficient.ioc k represents the outer loop integral coefficient. pcc k is the proportionality coefficient of the inner current loop. icc X is the integral coefficient of the inner current loop. L R is the equivalent reactance of the transmission line. L X is the resistance of the transmission line. f R is the equivalent reactance of the filter circuit. f For the filter line resistance, Y c For the equivalent admittance of the grid connection point to the ground, C dc For the DC side capacitor, U n U is the rated voltage of the power grid. f P is the grid fault voltage. in This refers to the active power on the DC side of the VSC.

[0077] Combination Figures 6-12 The simulation results of transient overvoltage under multiple control parameters shown in the figure verify the conclusions regarding the influence of the aforementioned key parameters on overvoltage. Therefore, based on the results above, reducing the PLL bandwidth and reducing... ,Adjustment It helps to suppress overvoltage. Among them, Figure 6 Control parameters [I d,ref ,I q,ref ,k p5 ,k i5 = [0.2, -0.5, 5, 100] Figure 7 Control parameters [I d,ref ,I q,ref ,k p5 ,k i5 = [0.2, -0.5, 15, 750] Figure 8 Control parameters [I d,ref ,I q,ref ,k p5 ,k i5 = [0.2, -0.5, 25, 1250] Figure 9 Control parameters [I d,ref ,I q,ref ,k p5 ,k i5 = [0.1, -0.5, 15, 750] Figure 10 Control parameters [I d,ref ,I q,ref ,k p5 ,k i5 = [0.3, -0.5, 15, 750] Figure 11 Control parameters [I d,ref ,I q,ref ,k p5 ,k i5= [0.2, -0.4, 15, 750] Figure 12 Control parameters [I d,ref ,I q,ref ,k p5 ,k i5 = [0.2, -0.6, 15, 750].

[0078] The following describes a control parameter optimization device for suppressing grid connection point overvoltage provided in this application. The control parameter optimization device for suppressing grid connection point overvoltage described below corresponds to the control parameter optimization method for suppressing grid connection point overvoltage described above.

[0079] Please see Figure 13 The control parameter optimization device 1300 for suppressing overvoltage at the grid connection point includes: an acquisition unit 1301, used to acquire the control parameters of the PLL of the VSC, and the grid voltage value and current command value of the VSC at each stage; wherein, the PLL includes four stages, namely, a first stage of steady-state operation before the occurrence of an AC fault, a second stage of low-voltage ride-through LVRT strategy not being implemented after the occurrence of an AC fault, a third stage of LVRT strategy activation, and a fourth stage of LVRT strategy not being deactivated after the fault is cleared; a first solution unit 1302, used to determine the first differential equation of the PLL based on the control parameters, the grid voltage value and current command value of the first stage, and solve the first differential equation to obtain the steady-state phase and steady-state frequency of the PLL; a second solution unit 1303, used to... Based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, a second differential equation is obtained, and an approximate analytical solution to the second differential equation is solved; a third solving unit 1304 is used to obtain a third differential equation based on the grid voltage and current command values ​​of the third stage and the first differential equation, and to solve the third differential equation based on the approximate analytical solution to the second differential equation to obtain an approximate analytical solution to the third differential equation; a fourth solving unit 1305 is used to obtain the grid connection point overvoltage prediction value based on the grid voltage and current command values ​​of the fourth stage and the approximate analytical solution to the third differential equation; an adjustment unit 1306 is used to adjust the control parameters based on the grid connection point overvoltage prediction value to suppress the grid connection point overvoltage.

[0080] In one possible embodiment, in the step of obtaining a second differential equation based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, and solving for an approximate analytical solution to the second differential equation, the second solving unit 1303 is specifically configured to: determine the steady-state phase as the initial phase of the second stage; obtain the initial frequency of the second stage based on the control equation of the PLL and the steady-state frequency; replace the initial phase of the first stage in the first differential equation with the initial phase of the second stage, and replace the grid voltage and current command values ​​of the first stage in the first differential equation with the grid voltage and current command values ​​of the second stage, to obtain the second differential equation; set preset parameters based on the second differential equation, and simplify the second differential equation based on the preset parameters to obtain a simplified second differential equation; and analyze the simplified second differential equation based on the initial phase and the initial frequency of the second stage to obtain an approximate analytical solution to the second differential equation.

[0081] In one possible embodiment, in the process of obtaining a third differential equation based on the grid voltage and current command values ​​of the third stage and the first differential equation, and solving the third differential equation based on the approximate analytical solution of the second differential equation to obtain an approximate analytical solution of the third differential equation, the third solving unit 1304 is specifically used to: replace the grid voltage and current command values ​​of the first stage in the first differential equation with the grid voltage and current command values ​​of the third stage to obtain the third differential equation; solve the third differential equation to obtain a steady-state solution of the third differential equation; simplify the third differential equation based on the steady-state solution of the third differential equation to obtain a simplified third differential equation; obtain the final phase value and final frequency value of the second stage based on the approximate analytical solution of the second differential equation; determine the final phase value of the second stage as the initial phase of the third stage; obtain the frequency mutation amount of the third stage; determine the initial frequency of the third stage based on the final frequency value of the second stage and the frequency mutation amount of the third stage; and analyze the simplified third differential equation based on the initial phase and the initial frequency to obtain an approximate analytical solution of the third differential equation.

[0082] In one possible embodiment, in the process of analyzing the third simplified differential equation based on the initial phase and the initial frequency to obtain an approximate analytical solution to the third differential equation, the third solving unit 1304 is specifically configured to: decompose the third simplified differential equation into an outer layer equation describing the slowly varying main characteristics of the system and an inner layer equation describing the rapidly varying boundary layer characteristics of the system; solve the outer layer equation to obtain a first approximate solution, and solve the inner layer equation to obtain a second approximate solution; and combine the first approximate solution and the second approximate solution using a matched asymptotic expansion technique to obtain an approximate analytical solution to the third differential equation.

[0083] In one possible embodiment, in obtaining the grid connection point overvoltage estimate based on the grid voltage and current command values ​​of the fourth stage and the approximate analytical solution of the third differential equation, the fourth solution unit 1305 is specifically configured to: replace the grid voltage and current command values ​​of the first stage in the first differential equation with the grid voltage and current command values ​​of the fourth stage to obtain the fourth differential equation; obtain the final phase value and final frequency value of the third stage based on the approximate analytical solution of the third differential equation; determine the final phase value of the third stage as the initial phase of the fourth stage; obtain the frequency mutation amount of the fourth stage; determine the initial frequency of the fourth stage based on the final frequency value of the third stage and the frequency mutation amount of the fourth stage; solve the fourth differential equation based on the initial phase and the initial frequency of the fourth stage to obtain the phase value of the fourth stage; and obtain the grid connection point overvoltage estimate based on the phase value of the fourth stage.

[0084] In one possible embodiment, in obtaining the grid connection point overvoltage estimate based on the phase value of the fourth stage, the fourth solving unit 1305 is specifically used to: obtain the correlation between the grid connection point voltage and the phase-locked loop phase based on the voltage vector relationship; and obtain the grid connection point overvoltage estimate based on the phase value of the fourth stage and the correlation relationship.

[0085] Please see Figure 14 , Figure 14 This is a schematic diagram of the structure of the electronic device provided in this application. For example... Figure 14As shown, the electronic device may include: a processor 1410, a communication interface 1420, a memory 1430, and a communication bus 1440. The processor 1410, communication interface 1420, and memory 1430 communicate with each other via the communication bus 1440. The processor 1410 can call logic instructions in the memory 1430 to execute a control parameter adjustment method for suppressing overvoltage at the grid connection point. This method includes: acquiring the control parameters of the PLL of the VSC, as well as the grid voltage value and current command value of the VSC at each stage; wherein the PLL includes four stages: a first stage of steady-state operation before an AC fault occurs, a second stage of low-voltage ride-through (LVRT) strategy not being implemented after an AC fault occurs, a third stage of LVRT strategy activation, and a fourth stage of LVRT strategy not being deactivated after fault clearance; determining the first differential equation of the PLL based on the control parameters, the grid voltage value and current command value of the first stage, and solving the first differential equation to obtain the PLL. The steady-state phase and steady-state frequency of LL; based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, a second differential equation is obtained, and an approximate analytical solution to the second differential equation is solved; based on the grid voltage and current command values ​​of the third stage, and the first differential equation, a third differential equation is obtained, and the approximate analytical solution to the third differential equation is solved to obtain an approximate analytical solution to the third differential equation; based on the grid voltage and current command values ​​of the fourth stage and the approximate analytical solution to the third differential equation, an estimated value of the grid connection point overvoltage is obtained; based on the estimated value of the grid connection point overvoltage, the control parameters are adjusted to suppress the grid connection point overvoltage.

[0086] Furthermore, the logical instructions in the aforementioned memory 1430 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0087] On the other hand, this application also provides a non-transitory computer-readable storage medium storing a computer program thereon. When executed by a processor, the computer program implements a control parameter adjustment method for suppressing grid-connected point overvoltage provided by the methods described above. This method includes: acquiring control parameters of the PLL of the VSC, and the grid voltage and current command values ​​of the VSC at each stage; wherein the PLL includes four stages: a first stage of steady-state operation before an AC fault occurs, a second stage where the low-voltage ride-through (LVRT) strategy is not engaged after an AC fault occurs, a third stage where the LVRT strategy is activated, and a fourth stage where the LVRT strategy is not deactivated after the fault is cleared; and determining a first differential equation of the PLL based on the control parameters, the grid voltage and current command values ​​of the first stage. The process involves: solving the first differential equation to obtain the steady-state phase and steady-state frequency of the PLL; obtaining the second differential equation based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation; solving the approximate analytical solution of the second differential equation; obtaining the third differential equation based on the grid voltage and current command values ​​of the third stage and the first differential equation; solving the third differential equation based on the approximate analytical solution of the second differential equation; obtaining the grid connection point overvoltage prediction value based on the grid voltage and current command values ​​of the fourth stage and the approximate analytical solution of the third differential equation; and adjusting the control parameters based on the grid connection point overvoltage prediction value to suppress the grid connection point overvoltage.

[0088] On another front, this application also provides a computer program product, including a computer program that, when executed by a processor, implements any of the above-described methods for adjusting control parameters to suppress overvoltage at the grid connection point. This method includes: acquiring control parameters of the PLL of the VSC, and the grid voltage and current command values ​​of the VSC at each stage; wherein the PLL includes four stages: a first stage of steady-state operation before an AC fault occurs, a second stage of low-voltage ride-through (LVRT) strategy not being implemented after an AC fault occurs, a third stage of LVRT strategy activation, and a fourth stage of LVRT strategy not being deactivated after fault clearance; determining the first differential equation of the PLL based on the control parameters, the grid voltage and current command values ​​of the first stage, and solving the... The first differential equation is used to obtain the steady-state phase and steady-state frequency of the PLL; based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, a second differential equation is obtained, and an approximate analytical solution to the second differential equation is solved; based on the grid voltage and current command values ​​of the third stage, the first differential equation is obtained, and a third differential equation is solved based on the approximate analytical solution of the second differential equation to obtain an approximate analytical solution to the third differential equation; based on the grid voltage and current command values ​​of the fourth stage and the approximate analytical solution to the third differential equation, an estimated value of the grid connection point overvoltage is obtained; based on the estimated value of the grid connection point overvoltage, the control parameters are adjusted to suppress the grid connection point overvoltage.

[0089] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for adjusting control parameters to suppress overvoltage at grid connection points, characterized in that, include: The control parameters of the phase-locked loop (PLL) of the voltage source converter (VSC) are obtained, as well as the grid voltage and current command values ​​of the VSC in each stage. The PLL includes four stages: the first stage of steady-state operation before the AC fault occurs, the second stage of low-voltage ride-through (LVRT) strategy not being engaged after the AC fault occurs, the third stage of LVRT strategy activation, and the fourth stage of LVRT strategy not being deactivated after the fault is cleared. The first differential equation of the PLL is determined based on the control parameters, the grid voltage value and current command value of the first stage, and the steady-state phase and steady-state frequency of the PLL are obtained by solving the first differential equation. Based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, the second differential equation is obtained, and the approximate analytical solution of the second differential equation is solved. Based on the grid voltage and current command values ​​of the third stage and the first differential equation, a third differential equation is obtained, and the third differential equation is solved based on the approximate analytical solution of the second differential equation to obtain the approximate analytical solution of the third differential equation. The estimated overvoltage at the grid connection point is obtained based on the grid voltage and current command values ​​in the fourth stage and the approximate analytical solution of the third differential equation. The control parameters are adjusted according to the estimated overvoltage at the grid connection point to suppress the overvoltage at the grid connection point.

2. The method according to claim 1, characterized in that, The process of obtaining a second differential equation based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency, and the first differential equation, and then solving the approximate analytical solution of the second differential equation, includes: The steady-state phase is determined as the initial phase of the second stage; The initial frequency of the second stage is obtained according to the control equation of the PLL and the steady-state frequency; The initial phase of the first stage in the first differential equation is replaced with the initial phase of the second stage, and the grid voltage value and current command value of the first stage in the first differential equation are replaced with the grid voltage value and current command value of the second stage, to obtain the second differential equation. Based on the second differential equation, preset parameters are set, and the second differential equation is simplified according to the preset parameters to obtain the second simplified differential equation; The second differential simplified equation is analyzed based on the initial phase and initial frequency of the second stage to obtain an approximate analytical solution to the second differential equation.

3. The method according to claim 1 or 2, characterized in that, The process of obtaining a third differential equation based on the grid voltage and current command values ​​of the third stage and the first differential equation, and then solving the third differential equation based on the approximate analytical solution of the second differential equation to obtain an approximate analytical solution for the third differential equation, includes: The first differential equation is obtained by replacing the grid voltage and current command values ​​of the first stage with the grid voltage and current command values ​​of the third stage. Solve the third differential equation to obtain the steady-state solution of the third differential equation; The third differential equation is simplified based on the steady-state solution of the third differential equation to obtain the simplified third differential equation. The final phase value and final frequency value of the second stage are obtained from the approximate analytical solution of the second differential equation. The final phase value of the second stage is determined to be the initial phase of the third stage; Obtain the frequency mutation amount of the third stage; The initial frequency of the third stage is determined based on the final frequency value of the second stage and the frequency mutation amount of the third stage; The third differential simplified equation is analyzed based on the initial phase and the initial frequency to obtain an approximate analytical solution to the third differential equation.

4. The method according to claim 3, characterized in that, The step of analyzing the simplified third differential equation based on the initial phase and the initial frequency to obtain an approximate analytical solution to the third differential equation includes: The third differential simplified equation is decomposed into an outer equation describing the slow-varying main characteristics of the system and an inner equation describing the fast-varying boundary layer characteristics of the system. Solving the outer equation yields a first approximate solution, and solving the inner equation yields a second approximate solution; By combining the first approximate solution and the second approximate solution using the matching asymptotic expansion technique, an approximate analytical solution to the third differential equation is obtained.

5. The method according to claim 1 or 2, characterized in that, The process of obtaining the grid connection point overvoltage estimate based on the grid voltage and current command values ​​in the fourth stage and the approximate analytical solution of the third differential equation includes: The first differential equation is obtained by replacing the grid voltage and current command values ​​of the first stage with the grid voltage and current command values ​​of the fourth stage. The final phase value and final frequency value of the third stage are obtained from the approximate analytical solution of the third differential equation. The final phase value of the third stage is determined to be the initial phase of the fourth stage; Obtain the frequency mutation amount of the fourth stage; The initial frequency of the fourth stage is determined based on the final frequency value of the third stage and the frequency mutation amount of the fourth stage; Solve the fourth differential equation based on the initial phase and initial frequency of the fourth stage to obtain the phase value of the fourth stage; The estimated overvoltage value at the grid connection point is obtained based on the phase value of the fourth stage.

6. The method according to claim 5, characterized in that, The step of obtaining the grid connection point overvoltage estimate based on the phase value of the fourth stage includes: The correlation between the grid connection point voltage and the phase-locked loop phase is obtained based on the voltage vector relationship; The estimated overvoltage value at the grid connection point is obtained based on the phase value of the fourth stage and the correlation.

7. A control parameter optimization device for suppressing overvoltage at grid connection point, characterized in that, include: The acquisition unit is used to acquire the control parameters of the phase-locked loop (PLL) of the voltage source converter (VSC), as well as the grid voltage and current command values ​​of the VSC at each stage; wherein, the PLL includes four stages, namely the first stage of steady-state operation before the occurrence of AC fault, the second stage of low-voltage ride-through (LVRT) strategy not being engaged after the occurrence of AC fault, the third stage of LVRT strategy being activated, and the fourth stage of LVRT strategy not being deactivated after the fault is cleared. The first solving unit is used to determine the first differential equation of the PLL based on the control parameters, the grid voltage value and current command value of the first stage, and solve the first differential equation to obtain the steady-state phase and steady-state frequency of the PLL. The second solving unit is used to obtain the second differential equation based on the grid voltage and current command values ​​of the second stage, the steady-state phase, the steady-state frequency and the first differential equation, and to solve the approximate analytical solution of the second differential equation. The third solution unit is used to obtain the third differential equation based on the grid voltage and current command values ​​of the third stage and the first differential equation, and to solve the third differential equation based on the approximate analytical solution of the second differential equation to obtain the approximate analytical solution of the third differential equation. The fourth solution unit is used to obtain the estimated overvoltage value at the grid connection point based on the grid voltage and current command values ​​in the fourth stage and the approximate analytical solution of the third differential equation. An adjustment unit is used to adjust the control parameters according to the estimated overvoltage at the grid connection point in order to suppress the overvoltage at the grid connection point.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the control parameter adjustment method for suppressing overvoltage at the grid connection point as described in any one of claims 1 to 6.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the control parameter adjustment method for suppressing overvoltage at the grid connection point as described in any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the control parameter adjustment method for suppressing overvoltage at the grid connection point as described in any one of claims 1 to 6.

Images