Evaluation method of robustness of wide-band oscillation suppression strategy for wind power through flexible AC / DC grid integration system

Abstract

The application discloses a kind of wind power through flexible grid-connected system wideband oscillation suppression strategy robustness evaluation method, comprising: 1, establish the harmonic state space impedance model of wind power through flexible grid-connected system when using different wideband oscillation suppression strategy, obtain the damping index of system before and after the suppression strategy is added;2, obtain the transient state performance index of system before and after the suppression strategy is added, and dynamic weight distribution result;3, based on transient state performance index, damping performance index obtains the robustness evaluation method of oscillation suppression strategy.The application can comprehensively evaluate through multidimensional index collaborative analysis, so that wideband oscillation suppression strategy has good robustness under the framework of multidimensional index after adding, ensure that the system is balanced in dynamic, steady and anti-interference ability.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of power system stability analysis, and particularly relates to a method for evaluating the robustness of a wide-band oscillation suppression strategy of a wind power through a flexible direct current grid-connected system. BACKGROUND

[0002] With the rapid development of new energy power generation, multi-module parallel power electronic systems and other technologies, power electronic converters are increasingly used in power grids. However, these systems are easily affected by factors such as parameter perturbation, load mutation, and grid impedance changes during operation, causing oscillation problems, which seriously threaten the stability and power quality of the system. In order to ensure the safe operation of the system, various oscillation suppression strategies, such as optimizing existing controller parameters and structure, adding damping control, and adding passive filtering devices, are widely studied and applied. However, how to scientifically evaluate the robustness of these suppression strategies, especially their adaptability under complex conditions, has become a key challenge in engineering practice. Existing methods for evaluating the robustness of oscillation suppression strategies mainly rely on a single index, such as transient performance index, steady-state performance index, and damping performance index. However, in the wind power through a flexible direct current grid-connected system, there are multiple uncertainties, and it is difficult to comprehensively evaluate the robustness of the suppression strategy by considering only a single index. SUMMARY

[0003] The present application is to solve the above-mentioned deficiencies in the prior art, and proposes a method for evaluating the robustness of a wide-band oscillation suppression strategy of a wind power through a flexible direct current grid-connected system, so as to achieve the robustness evaluation of the oscillation suppression strategy of the wind power through the flexible direct current grid-connected system by using dynamic weight distribution based on the transient and steady-state performance and damping performance indexes of different wide-band oscillation suppression strategies, thereby ensuring the balanced performance of the system in terms of dynamic, steady-state and anti-interference capabilities.

[0004] In order to achieve the above-mentioned application purposes, the following technical solutions are adopted in the present application:

[0005] The present application is a method for evaluating the robustness of a wide-band oscillation suppression strategy of a wind power through a flexible direct current grid-connected system, wherein the wind power through a flexible direct current grid-connected system comprises a wind turbine, a power collection line, and a flexible direct current transmission system, and the evaluation method is performed according to the following steps:

[0006] Step S1: obtaining the damping index of the wind power through a flexible direct current grid-connected system after adding a wide-band oscillation suppression strategy;

[0007] Step S1.1: establishing a harmonic state space impedance model of the wind power through a flexible direct current grid-connected system when a certain wide-band oscillation suppression strategy is added:

[0008] Step S1.2: obtaining the harmonic linearized state space impedance of the wind power through a flexible direct current grid-connected system after adding a perturbation component:

[0009] Step S1.3: Obtain damping index data for various operating conditions with and without broadband oscillation suppression strategy;

[0010] Step S1.3.1: From and Bode plots of the impedances of the flexible DC transmission system and the wind turbine were obtained without widening the bandwidth suppression strategy.

[0011] Depend on and Bode plots of the impedances of the flexible DC transmission system and the wind turbine were obtained when a broadband suppression strategy was incorporated.

[0012] The phase margin is calculated by subtracting the phase difference at the intersection of the magnitudes of the two Bode plots from 180 degrees.

[0013] Solve for the phase difference margin at each frequency point in the low-frequency band without a wideband oscillation suppression strategy. Phase margin at various frequency points in the mid-frequency band Phase margin at various frequency points in the high-frequency band ;

[0014] Solve for the phase difference margin at each frequency point in the low-frequency band when a wideband oscillation suppression strategy is implemented. Phase margin at various frequency points in the mid-frequency band Phase margin at various frequency points in the high-frequency band ;

[0015] Step S1.3.2: [The following is a list of steps / methods] The number of low-frequency points is defined as the low-frequency band damping X when no wideband oscillation suppression strategy is applied. 1wv_l ;Will The number of intermediate frequency points is defined as the intermediate frequency band damping X when no wideband oscillation suppression strategy is applied. 2wv_m ;Will The number of high-frequency points is defined as the high-frequency band damping X when no wideband oscillation suppression strategy is applied. 3wv_h ;Will The number of low-frequency points is defined as the low-frequency damping X when a wideband oscillation suppression strategy is added. 1sysact_l ;Will The number of intermediate frequency points is defined as the intermediate frequency band damping X when a wideband oscillation suppression strategy is added. 2sysact_m ;Will The number of high-frequency points is defined as the high-frequency band damping X when a wideband oscillation suppression strategy is added. 3sysact_h ;

[0016] Step S2: Obtain transient index data for various operating conditions with and without broadband oscillation suppression strategy;

[0017] Step S3: obtaining steady-state index data of various working conditions without and with the wide-band oscillation suppression strategy;

[0018] Step S4: performing robustness evaluation on transient-state and damping index data of various working conditions without and with the wide-band oscillation suppression strategy, to obtain a robustness evaluation score.

[0019] The evaluation method for the robustness of the wide-band oscillation suppression strategy of the wind power through flexible DC grid-connected system according to the application is characterized in that step S1.1 comprises:

[0020] Step S1.1.1: linearizing the wind power through flexible DC grid-connected system at the steady-state trajectory, so as to obtain a linear time-periodic system by using formula (1):

[0021] (1)

[0022] In formula (1), x(t) and u(t) are respectively the state variable of the wind power through flexible DC grid-connected system at time t and the input variable at time t; represents the differential of x(t); A(t) and B(t) are two coefficient matrices of the wind power through flexible DC grid-connected system at time t, and have:

[0023] (2)

[0024] (3)

[0025] (4)

[0026] In formulae (2)-(4), s is a complex variable; is a complex exponential signal of the wind power through flexible DC grid-connected system; is the Fourier coefficient of the nth harmonic, Z is a set of harmonic numbers, j is an imaginary unit, is the fundamental frequency angle of the wind power through flexible DC grid-connected system; t is time; is the state variable under the nth harmonic;

[0027] Step S1.1.2: transforming formula (1) to obtain formula (5):

[0028] (5)

[0029] In formula (5), is the state variable under the mth harmonic, is the input variable under the mth harmonic, and are the positive sequence component matrix and the negative sequence component matrix of A(t) after Euler transformation under the nth harmonic;

[0030] Step S1.1.3: Eliminate the exponential term on both sides of equation (5), let the complex variable s tend to 0, and simultaneously solve the state equation of each harmonic, so as to obtain the harmonic state space impedance model of the wind power through flexible grid-connected system at steady state by using equation (6);

[0031] (6)

[0032] In equation (6), X is a state vector containing each order harmonic; N is a diagonal matrix reflecting frequency information; A and B are two Toeplitz matrices of the wind power through flexible grid-connected system; U is an input vector containing each order harmonic;

[0033] Step S1.1.4: According to the harmonic state space impedance model of the wind power through flexible grid-connected system at steady state, the harmonic state space impedance model of the wind power through flexible grid-connected system after adding the perturbation component under a certain wideband oscillation suppression strategy is obtained by using equation (7):

[0034] (7)

[0035] In equation (7), X represents the state vector of each order harmonic after adding the perturbation component; and are two Toeplitz matrices after adding the perturbation component; U represents the input vector of each order harmonic after adding the perturbation component.

[0036] Further, step S1.2 includes:

[0037] According to equation (7), the frequency domain solution after adding the perturbation component is obtained, and then the voltage disturbance and the current disturbance at the perturbation frequency of the wind power through flexible grid-connected system are obtained, and the impedance of the wind power through flexible grid-connected system is obtained by dividing the two;

[0038] Extract the flexible harmonic linearized state space impedance and the harmonic linearized state space impedance of the wind turbine from the impedance of the wind power through flexible grid-connected system without adding the wideband oscillation suppression strategy;

[0039] Extract the flexible harmonic linearized state space impedance and the harmonic linearized state space impedance of the wind turbine from the impedance of the wind power through flexible grid-connected system after adding the wideband oscillation suppression strategy.

[0040] 4. The method for evaluating the robustness of the wideband oscillation suppression strategy of the wind power through flexible grid-connected system according to claim 3, wherein step S2 comprises:

[0041] Step S2.1: set the wide-band oscillation suppression strategy not to join and join after various working conditions, get the overshoot of the AC voltage X 4wv_f and adjustment time X 5wv_f without joining the wide-band oscillation suppression strategy, and the overshoot X 4sysact_f and adjustment time X 5sysact_f of the AC voltage after joining the wide-band oscillation suppression strategy.

[0042] Step S2.2: set the wide-band oscillation suppression strategy not to join and join after various working conditions, get the overshoot of the AC voltage X 6wv_s and adjustment time X 7wv_s without joining the wide-band oscillation suppression strategy, and the overshoot X 6sysact_s and adjustment time X 7sysact_s of the AC voltage after joining the wide-band oscillation suppression strategy.

[0043] Further, step S3 includes:

[0044] Step S3.1: set the wide-band oscillation suppression strategy not to join and join after various working conditions, get the total harmonic distortion rate X 8wv_thi and the total harmonic distortion rate X 9wv_thu of the grid-side outlet current without joining the wide-band oscillation suppression strategy, and the total harmonic distortion rate X 8sysact_thi and the total harmonic distortion rate X 9sysact_thu of the grid-side outlet voltage after joining the wide-band oscillation suppression strategy.

[0045] Step S3.2: set the wide-band oscillation suppression strategy not to join and join after various working conditions, get the steady-state error X 10wv_s of the AC voltage without joining the wide-band oscillation suppression strategy, and the steady-state error X 10sysact_s of the AC voltage after joining the wide-band oscillation suppression strategy.

[0046] Further, step S4 includes:

[0047] Step S4.1: let X1, X2, X3, X4, X5, X6, X7, X8, X9, X 10 be the low-frequency damping, the medium-frequency damping and the high-frequency damping, the three-phase short-circuit grounding fault overshoot, the three-phase short-circuit grounding fault adjustment time, the step response overshoot, the step response adjustment time, the current total harmonic distortion rate, the voltage total harmonic distortion rate and the steady-state error, respectively, and mark any one of them as ; X1∈{X 1wv_l , X 1sysact_l}, X2∈{X 2wv_m , X2sysact_m}, X3 e {X 3wv_h , X 3sysact_h}, X4 e {X 4wv_f , X 4sysact_f}, X5 e {X 5wv_f , X 5sysact_f}, X6 e {X 6wv_s , X 6sysact_s}, X7 e {X 7wv_s , X 7sysact_s}, X8 e {X 8wv_thi , X 8sysact_thi}, X9 e {X 9wv_thu , X 9sysact_thu}, X 10 e {X 10wv_s , X 10sysact_s} ;

[0048] Step S4.2: obtaining the jth index under the working condition corresponding to the ith wideband oscillation suppression strategy , normalizing the value of the jth index under the ith working condition by using formula (8) to obtain the jth normalized index under the ith working condition ;

[0049] (8)

[0050] In formula (8), i = 1, 2, 3, …, o + 1; j = 1, 2, 3, …, m; m = 10 is the number of indexes; o represents the total number of working conditions corresponding to all wideband oscillation suppression strategies, and o + 1 represents the number of working conditions corresponding to not adding the wideband oscillation suppression strategy; the positive indexes include low-frequency damping, mid-frequency damping, and high-frequency damping; and the negative indexes include three-phase short-circuit grounding fault overshoot, three-phase short-circuit grounding fault adjustment time, step response overshoot, step response adjustment time, current total harmonic distortion rate, voltage total harmonic distortion rate, and steady-state error.

[0051] Step S4.3: calculating the proportion p ij of the jth normalized index under the ith working condition by using formula (9) ;

[0052] (9)

[0053] Step S4.4: calculating the information entropy E j of the jth normalized index under all working conditions by using formula (10) :

[0054] (10)

[0055] ​Step S4.5: calculating the jth normalized indicator under all operating conditions by formula (11) weight of the jth normalized indicator :

[0056] (11)

[0057] Step S4.6: calculating the robustness evaluation score under the ith operating condition by formula (12) ;

[0058] (12).

[0059] The electronic device of the present application comprises a memory and a processor, and is characterized in that the memory is used to store a program supporting the processor to execute the evaluation method, and the processor is configured to execute the program stored in the memory.

[0060] The computer-readable storage medium of the present application has a computer program stored thereon, and is characterized in that the computer program is executed by the processor to perform the steps of the evaluation method.

[0061] Compared with the prior art, the present application has the following advantages:

[0062] 1. The present application breaks through the limitation of a single indicator, comprehensively covers transient, steady-state and damping performance, proposes a multi-dimensional evaluation framework, considers the combination of transient and steady-state performance and damping performance indicators, quantifies the robustness of the oscillation suppression strategy through dynamic weight distribution, avoids the problem that the system robustness evaluation indicator is not covered enough after using a single indicator for evaluation, and accurately quantifies the comprehensive performance of the wideband oscillation suppression strategy in a complex disturbance scenario, thereby providing a visual decision basis for wideband oscillation suppression strategy parameter setting.

[0063] 2. The present application obtains dynamic weight distribution under different operating conditions through multi-dimensional indicator quantization, proposes an oscillation suppression strategy robustness evaluation method based on transient and steady-state performance and damping performance indicators, can realize greater anti-interference in different dimensions of the wind power flexible direct-current grid-connected system, and thus ensures that the wind power flexible direct-current grid-connected system has strong robustness after adding the suppression strategy. BRIEF DESCRIPTION OF DRAWINGS

[0064] Figure 1 is a structural diagram of the wind power flexible direct-current grid-connected system of the present application;

[0065] Figure 2 is a flowchart of the present application;

[0066] Figure 3 is a structural diagram of the robustness evaluation device of the present application;

[0067] Figure 4 The structural schematic diagram of the computer device of the present application is shown in the figure;

[0068] Figure 5 The d-axis AC voltage response graph under the three-phase short-circuit grounding fault in different operating conditions of the present application is shown in the figure;

[0069] Figure 6 The d-axis AC voltage step response graph under different operating conditions of the present application is shown in the figure;

[0070] Figure 7 The robustness evaluation score result graph under different operating conditions of the present application is shown in the figure. DETAILED DESCRIPTION

[0071] The technical solutions of the present application will be specifically described below in combination with the drawings.

[0072] In this embodiment, as shown in the figure, Figure 1 The wind power flexible direct current grid-connected system mainly includes: wind turbine, power collection line, flexible direct current (flexible direct current, short for flexible direct current) system;

[0073] As shown in the figure, Figure 2 A wind power through flexible direct current grid-connected system wideband oscillation suppression strategy robustness evaluation method is as follows:

[0074] Step S1: obtaining the damping index of the wind power through flexible direct current grid-connected system after adding the wideband oscillation suppression strategy;

[0075] Step S1.1: establishing the harmonic state space impedance model of the wind power through flexible direct current grid-connected system when a certain wideband oscillation suppression strategy is added:

[0076] Step S1.1.1: for a linear periodic time-varying system with a period T, a first-order linear time-varying equation is used to linearize the wind power through flexible direct current grid-connected system at the steady-state trajectory, so as to obtain the linear time-periodic system by using formula (1):

[0077] (1)

[0078] In formula (1), x(t) and u(t) are respectively the state variable of the wind power through flexible direct current grid-connected system at time t and the input variable at time t; Dx(t) represents the differential of x(t); A(t) and B(t) are two coefficient matrices of the wind power through flexible direct current grid-connected system at time t.

[0079] According to the related theory of signal analysis, any periodic time-varying signal can be expressed in the form of Fourier series and under the condition of satisfying Dirichlet condition; the periodic signal u(t) is expressed in the form of Fourier series by using formula (2):

[0080] (2)

[0081] In formula (2), n is the harmonic number, u0 represents the direct current component, u n and θ n (n=0, 1, 2, …) respectively represent the amplitude and initial phase angle of the nth harmonic, t is the time, ω1 is the system fundamental angular frequency; and the Euler formula is used The periodic signal u(t) is transformed;

[0082] (3)

[0083] In formula (3), U n is the Fourier coefficient of the nth harmonic, is a complex number containing the signal amplitude and initial phase angle, and Z is a set of harmonic numbers; U n can be expressed as:

[0084] (4)

[0085] In formula (4), since the traditional frequency domain analysis method is only applicable to the extraction of frequency spectrum characteristics under the steady state, when studying the signal energy distribution in the transient process, an extended complex frequency domain modeling method needs to be used; according to the state space theory of linear systems, by introducing a complex exponential signal e st into the original state variable, a frequency domain response model containing transient components can be effectively constructed; input variables for frequency domain analysis of linear time-varying models and state variables and their derivatives of the wind power flexible HVDC grid-connected system are defined by using formula (5)-(7):

[0086] (5)

[0087] (6)

[0088] (7)

[0089] In formula (5)-(7), s is a complex variable; is a complex exponential signal of the wind power flexible HVDC grid-connected system; j is an imaginary unit, is the fundamental angular frequency of the wind power flexible HVDC grid-connected system; is the state variable under the nth harmonic.

[0090] Step S1.1.2: Transforming formula (1) to obtain formula (8):

[0091] (8)

[0092] In formula (8), is the state variable under the mth harmonic, is the input variable under mth harmonic, is the positive sequence component matrix and the negative sequence component matrix of A(t) after Euler transformation under nth harmonic; is the form of A(t) expanded as Fourier series under nth harmonic; is the form of B(t) expanded as Fourier series under nth harmonic.

[0093] Step S1.1.3: eliminating the exponential term on both sides of equation (8), letting the complex variable s tend to 0, and simultaneously solving the state equation of each harmonic, so as to obtain the harmonic state space impedance model of the wind power flexible grid-connected system at steady state by using equation (9);

[0094] (9)

[0095] In equation (9), X is the state vector containing each order harmonic; N is a diagonal matrix reflecting frequency information; A and B are two Toeplitz matrices of the wind power flexible grid-connected system; and U is the input vector containing each order harmonic.

[0096] Step S1.1.4: according to the harmonic state space impedance model of the wind power flexible grid-connected system at steady state, the harmonic state space impedance model of the wind power flexible grid-connected system after adding the perturbation component under a certain wideband oscillation suppression strategy is obtained by using equation (10):

[0097] (10)

[0098] In equation (10), represents the state vector of each order harmonic after adding the perturbation component; are two Toeplitz matrices after adding the perturbation component; represents the input vector of each order harmonic after adding the perturbation component.

[0099] Step S1.2: obtaining the harmonic linearized state space impedance of the wind power flexible grid-connected system after adding the perturbation component:

[0100] According to the frequency domain solution after adding the perturbation component, the voltage disturbance and the current disturbance at the perturbation frequency are obtained, and the impedance of the wind power flexible grid-connected system is obtained by dividing the two;

[0101] The flexible harmonic linearized state space impedance and the wind turbine harmonic linearized state space impedance are extracted from the impedance of the wind power flexible grid-connected system without adding the wideband oscillation suppression strategy.

[0102] ​​Extracting the state-space impedance of the flexible DC harmonic linearization when a broadband suppression strategy is added from the impedance of the flexible DC grid-connected wind power system Harmonic linearization state-space impedance of wind turbine units .

[0103] Step S1.3: Obtain damping index data for various operating conditions with and without broadband oscillation suppression strategy;

[0104] Step S1.3.1: From and Bode plots of the impedances of the flexible DC transmission system and the wind turbine were obtained without widening the bandwidth suppression strategy.

[0105] Depend on and Bode plots of the impedances of the flexible DC transmission system and the wind turbine were obtained when a broadband suppression strategy was incorporated.

[0106] The phase margin is calculated by subtracting the phase difference at the intersection of the magnitudes of the two Bode plots from 180 degrees.

[0107] Solve for the phase difference margin at each frequency point in the low-frequency band without a wideband oscillation suppression strategy. Phase margin at various frequency points in the mid-frequency band Phase margin at various frequency points in the high-frequency band ;

[0108] Solve for the phase difference margin at each frequency point in the low-frequency band when a wideband oscillation suppression strategy is implemented. Phase margin at various frequency points in the mid-frequency band Phase margin at various frequency points in the high-frequency band .

[0109] Step S1.3.2: [The sentence is incomplete and requires more context to be translated accurately.] The number of low-frequency points is defined as the low-frequency band damping X when no wideband oscillation suppression strategy is applied. 1wv_l ;Will The number of intermediate frequency points is defined as the intermediate frequency band damping X when no wideband oscillation suppression strategy is applied. 2wv_m ;Will The number of high-frequency points is defined as the high-frequency band damping X when no wideband oscillation suppression strategy is applied. 3wv_h ;Will The number of low-frequency points is defined as the low-frequency damping X when a wideband oscillation suppression strategy is added. 1sysact_l ;Will The number of intermediate frequency points is defined as the intermediate frequency band damping X when a wideband oscillation suppression strategy is added. 2sysact_m ;Will The number of high-frequency band frequency points is defined as the high-frequency band damping X when the wide-band oscillation suppression strategy is added 3sysact_h .

[0110] Step S2: Obtain transient index data of various conditions without and with the wide-band oscillation suppression strategy being added;

[0111] Step S2.1: Set three-phase short-circuit grounding faults at the bus under various conditions without and with the wide-band oscillation suppression strategy being added, to obtain the overshoot X of the alternating voltage without the wide-band oscillation suppression strategy being added 4wv_f and the adjustment time X 5wv_f , and the overshoot X of the alternating voltage with the wide-band oscillation suppression strategy being added 4sysact_f and the adjustment time X 5sysact_f ;

[0112] Step S2.2: Set step responses of the alternating voltage under various conditions without and with the wide-band oscillation suppression strategy being added, to obtain the overshoot X of the alternating voltage without the wide-band oscillation suppression strategy being added 6wv_s and the adjustment time X 7wv_s , and the overshoot X of the alternating voltage with the wide-band oscillation suppression strategy being added 6sysact_s and the adjustment time X 7sysact_s .

[0113] Step S3: Obtain steady-state index data of various conditions without and with the wide-band oscillation suppression strategy being added;

[0114] Step S3.1: Set various conditions without and with the wide-band oscillation suppression strategy being added, to obtain the total harmonic distortion rate X of the grid-side outlet current without the wide-band oscillation suppression strategy being added 8wv_thi and the total harmonic distortion rate X of the grid-side outlet voltage 9wv_thu , and the total harmonic distortion rate X of the grid-side outlet current with the wide-band oscillation suppression strategy being added 8sysact_thi and the total harmonic distortion rate X of the grid-side outlet voltage 9sysact_thu ;

[0115] Step S3.2: Set various conditions without and with the wide-band oscillation suppression strategy being added, to obtain the steady-state error X of the alternating voltage without the wide-band oscillation suppression strategy being added 10wv_s , and the steady-state error X of the alternating voltage with the wide-band oscillation suppression strategy being added 10sysact_s .

[0116] Step S4: Perform robustness evaluation on the transient and steady-state damping index data of various conditions without and with the wide-band oscillation suppression strategy being added;

[0117] Step S4.1: the three damping performance index data (X1, X2, X3), four transient performance index data (X4, X5, X6, X7) and three steady-state performance index data (X8, X9, X 10 ) obtained are summarized as ten index data under each operating condition; let X1, X2, X3, X4, X5, X6, X7, X8, X9, X 10 be low-frequency damping, medium-frequency damping and high-frequency damping, three-phase short-circuit ground fault overshoot, three-phase short-circuit ground fault adjustment time, step response overshoot, step response adjustment time, current total harmonic distortion, voltage total harmonic distortion and steady-state error, respectively, and any one of them is marked as ; X1∈{X 1wv_l , X 1sysact_l}, X2∈{X 2wv_m , X 2sysact_m}, X3∈{X 3wv_h , X 3sysact_h}, X4∈{X 4wv_f , X 4sysact_f}, X5∈{X 5wv_f , X 5sysact_f}, X6∈{X 6wv_s , X 6sysact_s}, X7∈{X 7wv_s , X 7sysact_s}, X8∈{X 8wv_thi , X 8sysact_thi}, X9∈{X 9wv_thu , X 9sysact_thu}, X 10 ∈{X 10wv_s , X 10sysact_s}.

[0118] Step S4.2: the jth index under the operating condition corresponding to the ith wideband oscillation suppression strategy is obtained, and the standardization processing of is performed by using formula (11) to obtain the jth standardized index under the ith operating condition;

[0119] (11)

[0120] In formula (11), i = 1, 2, 3, …, o + 1; j = 1, 2, 3, …, m; m = 10 is the number of indexes; o represents the total number of working conditions corresponding to all wide-band oscillation suppression strategies, and o + 1 represents the number of working conditions corresponding to no wide-band oscillation suppression strategy; the positive indexes include: low-band damping, mid-band damping and high-band damping; and the negative indexes include: three-phase short-circuit grounding fault overshoot, three-phase short-circuit grounding fault adjustment time, step response overshoot, step response adjustment time, current total harmonic distortion rate, voltage total harmonic distortion rate and steady-state error.

[0121] Step S4.3: calculating the jth standardized index under the ith working condition by using formula (12) The proportion p of the jth standardized index under the ith working condition ij ;

[0122] (12)

[0123] Step S4.4: calculating the information entropy E of the jth standardized index under all working conditions by using formula (13) j :

[0124] (13)

[0125] Step S4.5: calculating the weight w of the jth standardized index under all working conditions by using formula (14) :

[0126] (14)

[0127] Step S4.6: calculating the robustness evaluation score under the ith working condition by using formula (15) ;

[0128] (15)

[0129] The robustness evaluation scores of various working conditions are calculated by using the formula, which can directly and quantitatively reflect the influence of the addition of multiple wide-band suppression strategies on the system robustness. The quantitative model provides a clear index basis for selecting the optimal suppression strategy, so that the effects of different suppression strategies can be directly compared, thereby greatly improving the design efficiency of the suppression strategy.

[0130] In this embodiment, an electronic device includes a memory and a processor, the memory is used to store a program supporting the processor to execute the above method, and the processor is configured to execute the program stored in the memory.

[0131] ​​In this embodiment, a computer readable storage medium stores a computer program, and the computer program is executed by a processor to perform the steps of the above method.

[0132] The application also includes an oscillation suppression strategy robustness evaluation device based on transient and steady state performance and damping performance indicators, which uses the above method, as shown in the formula (1) and the formula (2), and includes: Figure 3

[0133] An impedance model establishment module is configured to establish a harmonic state space impedance model of the wind power flexible direct current grid-connected system before and after adding different wideband oscillation suppression strategies, so as to obtain damping indicators of the system in different frequency bands.

[0134] A transient and steady state indicator calculation module is configured to calculate a step response under a transient indicator and an overmodulation and a regulation time of an alternating voltage under a three-phase ground fault, and to calculate a total harmonic distortion rate of current and voltage and a steady state error under a steady state indicator based on the model measurement module.

[0135] A robustness evaluation method module is configured to evaluate the robustness before and after adding each wideband oscillation suppression strategy by using a weight distribution method based on the transient and steady state indicators, so as to select an optimal wideband oscillation suppression strategy.

[0136] Please refer to Figure 4 The computer device provided by the embodiment of the application includes a processor 510 and a memory 520, the memory 520 stores a computer program executable by the processor 510, and the computer program is executed by the processor 510 to perform the above method.

[0137] The embodiment of the application also provides a storage medium 530, and the storage medium 530 stores a computer program, and the computer program is executed by the processor 510 to perform the above method.

[0138] ​The storage medium 530 can be implemented by any type of volatile or nonvolatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0139] The application includes d-axis AC voltage response graphs under three-phase short-circuit grounding faults in different operating conditions, as shown in FIG. 6. Figure 5 As shown in FIG. 6, the adjustment time and overshoot of the d-axis AC voltage response under the three-phase short-circuit grounding fault are transient index data in robustness evaluation, reflecting the dynamic performance of the wind power through the flexible grid-connected system before and after the wide-band oscillation suppression strategy is added, and the smaller the adjustment time and overshoot of the three-phase short-circuit grounding fault are, the better. As can be seen from the figure, the adjustment time of the three-phase short-circuit grounding fault after the wide-band oscillation suppression strategy is added is smaller than that of the operating condition without the wide-band oscillation suppression strategy, and the adjustment time of the three-phase short-circuit grounding fault after the LC filter is added is the smallest; the overshoot of the three-phase short-circuit grounding fault after the wide-band oscillation suppression strategy is added is smaller than that of the operating condition without the wide-band oscillation suppression strategy, and the overshoot of the three-phase short-circuit grounding fault after the LC filter is added is the smallest.

[0140] The application also includes d-axis AC voltage step response graphs under different operating conditions, as shown in FIG. 7. Figure 6 As shown in FIG. 7, the adjustment time and overshoot of the d-axis AC voltage step response are transient index data in robustness evaluation, reflecting the dynamic performance of the wind power through the flexible grid-connected system before and after the wide-band oscillation suppression strategy is added, and the smaller the adjustment time and overshoot of the d-axis AC voltage step response are, the better. As can be seen from the figure, the adjustment time of the d-axis AC voltage step response after the wide-band oscillation suppression strategy is added is consistent with that of the operating condition without the wide-band oscillation suppression strategy; the overshoot of the d-axis AC voltage step response after the wide-band oscillation suppression strategy is added is smaller than that of the operating condition without the wide-band oscillation suppression strategy, and the overshoot of the d-axis AC voltage step response after the LC filter is added is the smallest.

[0141] The application also includes a robustness evaluation score result graph under different operating conditions, as shown in FIG. 8. Figure 7As shown in the figure, after the broadband oscillation suppression strategy is added, the robustness evaluation score of each operating condition is higher than that without the broadband oscillation suppression strategy, and the robustness evaluation score is the highest after the LC filter is added.

Claims

1. A method for evaluating the robustness of a broadband oscillation suppression strategy in a wind power grid-connected system via flexible DC transmission, wherein the wind power grid-connected system via flexible DC transmission comprises: Wind turbine generators, power collection lines, and flexible DC transmission systems; characterized in that the evaluation method is carried out according to the following steps: Step S1: Obtain the damping index of the wind power system connected to the grid via flexible DC after the broadband oscillation suppression strategy is added; Step S1.1: Establish the harmonic state-space impedance model of the wind power grid-connected system when a certain broadband oscillation suppression strategy is implemented: Step S1.2: Obtain the harmonic linearized state-space impedance of the wind power flexible DC grid-connected system after adding micro-disturbance components: Step S1.3: Obtain damping index data for various operating conditions with and without broadband oscillation suppression strategy; Step S1.3.1: Extract the state-space impedance of the flexible DC harmonic linearization without adding a broadband oscillation suppression strategy from the impedance of the wind power flexible DC grid-connected system. Harmonic linearization state-space impedance Z of wind turbine pmsg Bode plots of the impedances of the flexible DC transmission system and the wind turbine were obtained without widening the bandwidth suppression strategy. Extracting the state-space impedance of flexible DC harmonic linearization when a broadband suppression strategy is added from the impedance of the flexible DC grid-connected wind power system Harmonic linearization state-space impedance of wind turbine units Bode plots of the impedances of the flexible DC transmission system and the wind turbine were obtained when a broadband suppression strategy was incorporated. The phase margin is calculated by subtracting the phase difference at the intersection of the magnitudes of the two Bode plots from 180 degrees. Solve for the phase difference margin at each frequency point in the low-frequency band without a wideband oscillation suppression strategy. Phase margin at various frequency points in the mid-frequency band Phase margin at various frequency points in the high-frequency band ; Solve for the phase difference margin at each frequency point in the low-frequency band when a wideband oscillation suppression strategy is implemented. Phase margin at various frequency points in the mid-frequency band Phase margin at various frequency points in the high-frequency band ; Step S1.3.2: [The following is a list of steps, not a direct translation] The number of low-frequency points is defined as the low-frequency band damping X when no wideband oscillation suppression strategy is applied. 1wv_l ;Will The number of intermediate frequency points is defined as the intermediate frequency band damping X when no wideband oscillation suppression strategy is applied. 2wv_m ;Will The number of high-frequency points is defined as the high-frequency band damping X when no wideband oscillation suppression strategy is applied. 3wv_h ;Will The number of low-frequency points is defined as the low-frequency damping X when a wideband oscillation suppression strategy is added. 1sysact_l ;Will The number of intermediate frequency points is defined as the intermediate frequency band damping X when a wideband oscillation suppression strategy is added. 2sysact_m ;Will The number of high-frequency points is defined as the high-frequency band damping X when a wideband oscillation suppression strategy is added. 3sysact_h ; Step S2: Obtain transient index data for various operating conditions with and without broadband oscillation suppression strategy; Step S3: Obtain steady-state index data for various operating conditions with and without broadband oscillation suppression strategy; Step S4: Perform robustness assessment on the transient steady-state and damping index data of various operating conditions with and without broadband oscillation suppression strategies, and obtain robustness assessment scores.

2. The method for evaluating the robustness of a broadband oscillation suppression strategy for wind power connected to a flexible DC grid system according to claim 1, characterized in that, Step S1.1 includes: Step S1.1.1: At the steady-state trajectory, the wind power system connected to the flexible DC grid is linearized to obtain the linear time-periodic system using equation (1): (1) In equation (1), x(t) and u(t) are the state variable and input variable of the wind power grid-connected system via flexible DC at time t, respectively; Let x(t) represent the differential; A(t) and B(t) are two coefficient matrices of the wind power system connected to the grid via flexible DC at time t, and we have: (2) (3) (4) In equations (2)-(4), s is a complex variable; For a complex exponential signal in a wind power flexible DC grid-connected system; Here, Z represents the Fourier coefficients of the nth harmonic, Z is the set of harmonic orders, and j is the imaginary unit. t represents the fundamental angular frequency of the wind power flexible DC grid-connected system; t represents time. Let n be the state variables under the nth harmonic. Step S1.1.2: Transform equation (1) to obtain equation (5): (5) In equation (5), Let m be the state variable under the mth harmonic. For the input variable under the mth harmonic, and Let A(t) be the positive-order component matrix and the negative-order component matrix after Euler transformation under the nth harmonic; Step S1.1.3: Eliminate the exponential terms on both sides of equation (5), let the complex variable s approach 0, and simultaneously establish the state equations of each harmonic, thereby using equation (6) to obtain the harmonic state space impedance model of the wind power grid-connected system in steady state. (6) In equation (6), X is the state vector containing harmonics of each order; N is the diagonal matrix reflecting frequency information; A and B are the two Toplitz matrices of the wind power flexible DC grid-connected system; U is the input vector containing harmonics of each order. Step S1.1.4: Based on the harmonic state-space impedance model of the wind power flexible DC grid-connected system in steady state, the harmonic state-space impedance model of the wind power flexible DC grid-connected system after adding micro-disturbance components under a certain broadband oscillation suppression strategy is obtained using equation (7): (7) In equation (7), This represents the state vector of each order harmonic after the addition of micro-perturbation components; and These are the two Toplitz matrices after adding the micro-perturbation components; This represents the input vector of each order harmonic after adding micro-perturbation components.

3. The method for evaluating the robustness of a broadband oscillation suppression strategy for wind power connected to a flexible DC grid system according to claim 2, characterized in that, Step S1.2 includes: According to equation (7), the frequency domain solution after adding the micro-perturbation component is obtained, and then the voltage perturbation and current perturbation at the micro-perturbation frequency are obtained. After dividing the two, the impedance of the wind power flexible DC grid connection system is obtained. Extracting the flexible DC harmonic linearization state-space impedance from the impedance of the flexible DC grid-connected wind power system without incorporating a broadband oscillation suppression strategy. Harmonic linearization state-space impedance of wind turbine units ; Extracting the state-space impedance of the flexible DC harmonic linearization when a broadband suppression strategy is added from the impedance of the flexible DC grid-connected wind power system Harmonic linearization state-space impedance of wind turbine units .

4. The method for evaluating the robustness of a broadband oscillation suppression strategy for wind power connected to a flexible DC grid system according to claim 3, characterized in that, Step S2 includes: Step S2.1: Set up three-phase short-circuit ground faults at the busbar under various operating conditions with and without the broadband oscillation suppression strategy, and obtain the overshoot X of the AC voltage without the broadband oscillation suppression strategy. 4wv_f and adjustment time X 5wv_f And the overshoot X of AC voltage under the addition of a wideband oscillation suppression strategy. 4sysact_f and adjustment time X 5sysact_f ; Step S2.2: Set the AC voltage step response under various operating conditions with and without the wideband oscillation suppression strategy, and obtain the overshoot X of the AC voltage without the wideband oscillation suppression strategy. 6wv_s and adjustment time X 7wv_s , and the overshoot X of AC voltage under the addition of a wideband oscillation suppression strategy 6sysact_s and adjustment time X 7sysact_s .

5. The method for evaluating the robustness of a broadband oscillation suppression strategy for wind power connected to a flexible DC grid system according to claim 4, characterized in that, Step S3 includes: Step S3.1: Set up various operating conditions with and without the broadband oscillation suppression strategy, and obtain the total harmonic distortion rate X of the grid-side output current without the broadband oscillation suppression strategy. 8wv_thi The total harmonic distortion rate X of the grid-side output voltage 9wv_thu , and the total harmonic distortion rate X of the grid-side outlet current under the addition of a broadband oscillation suppression strategy. 8sysact_thi The total harmonic distortion rate X of the grid-side output voltage 9sysact_thu ; Step S3.2: Set up various operating conditions with and without the broadband oscillation suppression strategy, and obtain the steady-state error X of the AC voltage without the broadband oscillation suppression strategy. 10wv_s And the steady-state error X of AC voltage under the addition of a wideband oscillation suppression strategy. 10sysact_s .

6. The method for evaluating the robustness of a broadband oscillation suppression strategy for wind power connected to a flexible DC grid system according to claim 5, characterized in that, Step S4 includes: Step S4.1: Let X1, X2, X3, X4, X5, X6, X7, X8, X9, X 10 These are, respectively, low-frequency band damping, mid-frequency band damping, high-frequency band damping, three-phase short-circuit-to-ground fault overshoot, three-phase short-circuit-to-ground fault settling time, step response overshoot, step response settling time, total harmonic distortion of current, total harmonic distortion of voltage, and steady-state error, with any one of these indicators labeled as... ;X1∈{X 1wv_l X 1sysact_l },X2∈{X 2wv_m X 2sysact_m },X3∈{X 3wv_h X 3sysact_h },X4∈{X 4wv_f X 4sysact_f }, X5∈{X 5wv_f X 5sysact_f },X6∈{X 6wv_s X 6sysact_s },X7∈{X 7wv_s X 7sysact_s },X8∈{X 8wv_thi X 8sysact_thi },X9∈{X 9wv_thu X 9sysact_thu }, X 10 ∈{X 10wv_s X 10sysact_s }; Step S4.2: Obtain the j-th index under the operating condition corresponding to the i-th wideband oscillation suppression strategy. Using equation (8) Standardization is performed to obtain the j-th standardized index under the i-th working condition. ; (8) In equation (8), i = 1, 2, 3, ..., o+1; j = 1, 2, 3, ..., m; m = 10 is the number of indicators; o represents the total number of operating conditions corresponding to all broadband oscillation suppression strategies, and o+1 represents the number of operating conditions corresponding to the absence of broadband oscillation suppression strategies; the positive indicators include: low-frequency band damping, mid-frequency band damping and high-frequency band damping; the negative indicators include: three-phase short-circuit ground fault overshoot, three-phase short-circuit ground fault adjustment time, step response overshoot, step response adjustment time, total harmonic distortion of current, total harmonic distortion of voltage and steady-state error; Step S4.3: Calculate the j-th standardized index under the i-th working condition using equation (9). Specific gravity p ij ; (9) Step S4.4: Calculate the j-th standardized index under all operating conditions using equation (10). Information entropy E j : (10) Step S4.5: Calculate the j-th standardized index under all operating conditions using equation (11). weight : (11) Step S4.6: Calculate the robustness assessment score for the i-th working condition using equation (12). ; (12)。 7. An electronic device, comprising a memory and a processor, characterized in that, The memory is used to store a program that supports the processor in executing any of the evaluation methods of claims 1-6, the processor being configured to execute the program stored in the memory.

8. A computer-readable storage medium storing a computer program thereon, characterized in that, The computer program is executed by the processor to perform the steps of any of the evaluation methods described in claims 1-6.

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