Method for evaluating robustness of broadband oscillation suppression strategy of wind power through flexible direct current grid-connected system

Abstract

The invention discloses a method for evaluating the robustness of broadband oscillation suppression strategies of a wind power flexible direct current grid-connected system, and the method comprises the steps: 1, building a harmonic state space impedance model of the wind power flexible direct current grid-connected system when different broadband oscillation suppression strategies are adopted, and obtaining the damping indexes of the system before and after the suppression strategies are added; 2, obtaining transient and steady state performance indexes of the system before and after the inhibition strategy is added and a dynamic weight distribution result; and 3, obtaining a robustness evaluation method of the oscillation suppression strategy based on the transient steady state performance index and the damping performance index. According to the method, comprehensive evaluation can be carried out through multi-dimensional index collaborative analysis, so that the broadband oscillation suppression strategy has good robustness under a multi-dimensional index framework after being added, and the balanced performance of the system in dynamic, steady and anti-interference capabilities is ensured.

Description

Technical Field

[0001] The present invention belongs to the field of power system stability analysis, and in particular relates to a method for evaluating the robustness of a broadband oscillation suppression strategy of a wind power flexible direct current grid-connected system. Background Art

[0002] With the rapid development of technologies such as renewable energy generation and multi-module parallel power electronic systems, power electronic converters are increasingly used in power grids. However, these systems are susceptible to parameter perturbations, load mutations, grid impedance changes, and other factors during operation, causing oscillation problems that seriously threaten the stability and power quality of the system. To ensure the safe operation of the system, various oscillation suppression strategies, such as optimizing existing controller parameters and structures, additional damping control, and additional passive filtering devices, have been widely studied and applied. However, how to scientifically evaluate the robustness of these suppression strategies, especially their adaptability under complex working conditions, has become a key challenge in engineering practice. Existing methods for evaluating the robustness of oscillation suppression strategies mainly rely on single indicators, such as transient performance indicators, steady-state performance indicators, and damping performance indicators. However, in the wind power flexible direct current grid-connected system, there are multi-dimensional uncertainties. Considering only a single indicator, it is difficult to comprehensively evaluate the robustness of the suppression strategy. Summary of the invention

[0003] The present invention aims to solve the deficiencies of the above-mentioned prior art and proposes a method for evaluating the robustness of a wide-band oscillation suppression strategy of a wind power flexible direct current grid-connected system, so as to obtain the transient and steady-state performance and damping performance indicators of different wide-band oscillation suppression strategies, and adopt dynamic weight allocation to realize the robustness evaluation of the oscillation suppression strategy of the wind power flexible direct current grid-connected system, thereby ensuring the balanced performance of the system in dynamic, steady-state and anti-interference capabilities.

[0004] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme:

[0005] The present invention provides a method for evaluating the robustness of a broadband oscillation suppression strategy of a wind power grid-connected flexible direct current system. The wind power grid-connected flexible direct current system comprises: a wind turbine, a collector line, and a flexible direct current transmission system. The evaluation method is performed according to the following steps:

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

[0007] 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 added:

[0008] Step S1.2: Obtain the harmonic linearized state space impedance of the wind power flexible direct current grid-connected system after adding the micro-disturbance component:

[0009] Step S1.3: Obtain damping index data of various working conditions with and without adding the wide-band oscillation suppression strategy;

[0010] Step S1.3.1: and The Bode diagrams of the impedances of the flexible DC transmission system and wind turbines are obtained without the wideband suppression strategy.

[0011] Depend on and The Bode diagrams of the impedances of the flexible DC transmission system and wind turbines are obtained when the wide-band suppression strategy is added.

[0012] The phase difference margin is obtained by subtracting the phase difference corresponding to the intersection of the amplitudes of the two Bode diagrams from 180 degrees.

[0013] Solve the phase difference margin of each frequency point in the low frequency band when the wide-band oscillation suppression strategy is not used. , Phase difference margin at each frequency point in the mid-frequency band , Phase difference margin at each frequency point in the high frequency band ;

[0014] Solve the phase difference margin of each frequency point in the low frequency band when adding the wide-band oscillation suppression strategy , Phase difference margin at each frequency point in the mid-frequency band , Phase difference margin at each frequency point in the high frequency band ;

[0015] Step S1.3.2: The number of low-band frequency points is defined as the low-band damping X when the widening band oscillation suppression strategy is not used. 1wv_l ;Will The number of mid-band frequency points is defined as the mid-band damping X when the widening band oscillation suppression strategy is not used. 2wv_m ;Will The number of high-band frequency points is defined as the high-band damping X when the widening band oscillation suppression strategy is not used. 3wv_h ;Will The number of low-band frequency points is defined as the low-band damping X when the wide-band oscillation suppression strategy is added 1sysact_l ;Will The number of mid-band frequency points is defined as the mid-band damping X when the wide-band oscillation suppression strategy is added. 2sysact_m ;Will The number of high-band frequency points is defined as the high-band damping X when the wide-band oscillation suppression strategy is added. 3sysact_h ;

[0016] Step S2: Acquire transient index data of various working conditions with and without adding the wideband oscillation suppression strategy;

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

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

[0019] The method for evaluating the robustness of a broadband oscillation suppression strategy for a wind power flexible direct current grid-connected system described in the present invention is also characterized in that step S1.1 comprises:

[0020] Step S1.1.1: At the steady-state trajectory, the wind power system connected to the flexible direct current grid is linearized, so that the linear time period system is obtained using equation (1):

[0021] (1)

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

[0023] (2)

[0024] (3)

[0025] (4)

[0026] In formula (2)-formula (4), s is a complex variable; It is the complex exponential signal of the wind power flexible direct current grid-connected system; is the Fourier coefficient of the nth harmonic, Z is the set of harmonic orders, j is the imaginary unit, is the fundamental angular frequency of the wind power flexible direct current grid-connected system; t is the time; is the state variable under the nth harmonic;

[0027] Step S1.1.2: Transform equation (1) to obtain equation (5):

[0028] (5)

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

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

[0031] (6)

[0032] In formula (6), X is the state vector containing harmonics of various orders; N is the diagonal matrix reflecting frequency information; A and B are the two Toeplitz matrices of the wind power flexible direct current grid-connected system; U is the input vector containing harmonics of various orders;

[0033] Step S1.1.4: Based on the harmonic state space impedance model of the wind power flexible direct current grid-connected system in steady state, the harmonic state space impedance model of the wind power flexible direct current grid-connected system after adding the micro-disturbance component under a certain wide-band oscillation suppression strategy is obtained using formula (7):

[0034] (7)

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

[0036] Furthermore, step S1.2 includes:

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

[0038] Extracting the state space impedance of flexible DC harmonic linearization without adding broadband oscillation suppression strategy from the impedance of wind power flexible DC grid-connected system Harmonic linearization state space impedance of wind turbines ;

[0039] Extracting the linearized state space impedance of flexible DC harmonics when adding broadband suppression strategy from the impedance of wind power flexible DC grid-connected system Harmonic linearization state space impedance of wind turbines .

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

[0041] Step S2.1: Set the three-phase short circuit grounding fault at the busbar under various working conditions without and with the wide-band oscillation suppression strategy, and obtain the overshoot of the AC voltage X without the wide-band oscillation suppression strategy. 4wv_f and adjust time X 5wv_f , and the overshoot of AC voltage X with broadband oscillation suppression strategy added 4sysact_f and adjust time X 5sysact_f ;

[0042] Step S2.2: Set the AC voltage to generate a step response under various working 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 adjust time X 7wv_s , and the overshoot of AC voltage X under the wide-band oscillation suppression strategy 6sysact_s and adjust time X 7sysact_s .

[0043] Further, step S3 includes:

[0044] Step S3.1: Set various operating conditions with and without the wideband oscillation suppression strategy, and obtain the total harmonic distortion rate X of the grid-side outlet current without the wideband oscillation suppression strategy. 8wv_thi And 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 broadband oscillation suppression strategy 8sysact_thi and the total harmonic distortion rate X of the grid-side output voltage 9sysact_thu ;

[0045] Step S3.2: Set various operating conditions with and without the wideband oscillation suppression strategy, and obtain the steady-state error X of the AC voltage without the wideband oscillation suppression strategy. 10wv_s , and the steady-state error X of the AC voltage when the wide-band oscillation suppression strategy is added 10sysact_s .

[0046] Further, step S4 includes:

[0047] Step S4.1: Let X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , X 8 , X 9 , X 10They are low-frequency band damping, medium-frequency band damping and high-frequency band damping, 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, and any one of them is marked as ;X 1 ∈{X 1wv_l , X 1sysact_l}, X 2 ∈{X 2wv_m , X 2sysact_m}, X 3 ∈{X 3wv_h , X 3sysact_h}, X 4 ∈{X 4wv_f , X 4sysact_f}, X 5 ∈{X 5wv_f , X 5sysact_f}, X 6 ∈{X 6wv_s , X 6sysact_s}, X 7 ∈{X 7wv_s , X 7sysact_s}, X 8 ∈{X 8wv_thi , X 8sysact_thi}, X 9 ∈{X 9wv_thu , X 9sysact_thu}, X 10 ∈{X 10wv_s , X 10sysact_s};

[0048] Step S4.2: Obtain the jth index under the working condition corresponding to the i-th wideband oscillation suppression strategy , using formula (8) Perform standardization to obtain the jth standardized index under the i-th 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 indicators; o represents the total number of operating conditions corresponding to all wide-band oscillation suppression strategies, and o+1 represents the number of operating conditions corresponding to when the wide-band oscillation suppression strategy is not added; the positive indicators include: low-frequency band damping, medium-frequency band damping and high-frequency band damping; the negative indicators 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: Calculate the jth standardized index under the i-th working condition using formula (9): The proportion p ij ;

[0052] (9)

[0053] Step S4.4: Calculate the jth standardized index under all working conditions through formula (10): Information entropy E j :

[0054] (10)

[0055] Step S4.5: Calculate the jth standardized index under all working conditions through formula (11): Weight :

[0056] (11)

[0057] Step S4.6: Calculate the robustness evaluation score under the i-th working condition by using formula (12): ;

[0058] (12).

[0059] An electronic device of the present invention includes a memory and a processor, wherein the memory is used to store a program that supports the processor to execute the evaluation method, and the processor is configured to execute the program stored in the memory.

[0060] The present invention provides a computer-readable storage medium, wherein a computer program is stored on the computer-readable storage medium, and the computer program executes the steps of the evaluation method when executed by a processor.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] 1. This invention 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, and quantifies the robustness of the oscillation suppression strategy through dynamic weight allocation. This method avoids the problem of insufficient coverage of robustness evaluation indicators of the system in uncertain scenarios after evaluation with only a single indicator, thereby accurately quantifying the comprehensive performance of the wide-band oscillation suppression strategy in complex disturbance scenarios, and providing a visual decision-making basis for the parameter setting of the wide-band oscillation suppression strategy.

[0063] 2. The present invention obtains dynamic weight distribution under different operating conditions by quantifying multi-dimensional indicators, and proposes an oscillation suppression strategy robustness evaluation method based on transient steady-state performance and damping performance indicators, which can realize that the wind power flexible direct-current grid-connected system has greater anti-interference ability in different dimensions, thereby ensuring that the wind power flexible direct-current grid-connected system has stronger robustness after the suppression strategy is added. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0065] Figure 2 is a flow chart of the present invention;

[0066] Figure 3 Schematic diagram of the structure of the robustness evaluation device of the present invention;

[0067] Figure 4 It is a structural schematic diagram of the computer device of the present invention;

[0068] Figure 5 It is a d-axis AC voltage response diagram under a three-phase short-circuit grounding fault under different operating conditions of the present invention;

[0069] Figure 6 d-axis AC voltage step response diagram under different operating conditions of the present invention;

[0070] Figure 7 This is a diagram showing the robustness evaluation score results under different operating conditions of the present invention. DETAILED DESCRIPTION

[0071] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0072] In this embodiment, Figure 1 As shown, the wind power flexible direct current grid-connected system mainly includes: wind turbines, collector lines, flexible direct current (flexible direct current transmission is referred to as flexible direct current) system;

[0073] like Figure 2 As shown, a method for evaluating the robustness of a broadband oscillation suppression strategy for a wind power grid-connected flexible direct current system is performed in the following steps:

[0074] Step S1: obtaining the damping index of the wind power flexible direct current grid-connected system after the wide-band oscillation suppression strategy is added;

[0075] 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 added:

[0076] Step S1.1.1: For a linear periodic time-varying system with a period of T, a first-order linear time-varying equation is used to linearize the wind power system connected to the flexible direct current grid at the steady-state trajectory, thereby obtaining a linear time-periodic system using equation (1):

[0077] (1)

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

[0079] Combining the relevant theories of signal analysis, we know that any periodic time-varying signal can be expressed in the form of a sum of Fourier series if it satisfies the Dirichlet condition. Using equation (2), the periodic signal u(t) can be expressed in the form of a sum of Fourier series.

[0080] (2)

[0081] In formula (2), n is the harmonic order, u is 0 represents the DC component, u n With θ n (n=0, 1, 2, …) represent the amplitude and initial phase angle of the nth harmonic, t is the time, ω 1 is the fundamental angular frequency of the system; and using Euler's formula Transform the periodic signal u(t);

[0082] (3)

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

[0084] (4)

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

[0086] (5)

[0087] (6)

[0088] (7)

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

[0090] Step S1.1.2: Transform equation (1) to obtain equation (8):

[0091] (8)

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

[0093] Step S1.1.3: Eliminate the exponential terms on both sides of equation (8), let the complex variable s tend to 0, and simultaneously establish the state equations of each harmonic, so as to obtain the harmonic state space impedance model of the wind power grid-connected system via flexible direct current in steady state using equation (9);

[0094] (9)

[0095] In formula (9), X is the state vector containing harmonics of various orders; N is the diagonal matrix reflecting frequency information; A and B are the two Toeplitz matrices of the wind power flexible direct current grid-connected system; and U is the input vector containing harmonics of various orders.

[0096] Step S1.1.4: Based on the harmonic state space impedance model of the wind power flexible direct current grid-connected system in steady state, the harmonic state space impedance model of the wind power flexible direct current grid-connected system after adding the micro-disturbance component under a certain wide-band oscillation suppression strategy is obtained using formula (10):

[0097] (10)

[0098] In formula (10), Represents the state vector of each order harmonic after adding the perturbation component; and are the 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: Obtain the harmonic linearized state space impedance of the wind power flexible direct current grid-connected system after adding the micro-disturbance component:

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

[0101] Extracting the state space impedance of flexible DC harmonic linearization without adding broadband oscillation suppression strategy from the impedance of wind power flexible DC grid-connected system Harmonic linearization state space impedance of wind turbines ;

[0102] Extracting the linearized state space impedance of flexible DC harmonics when adding broadband suppression strategy from the impedance of wind power flexible DC grid-connected system Harmonic linearization state space impedance of wind turbines .

[0103] Step S1.3: Obtain damping index data of various working conditions with and without adding the wide-band oscillation suppression strategy;

[0104] Step S1.3.1: and The Bode diagrams of the impedances of the flexible DC transmission system and wind turbines are obtained without the wideband suppression strategy.

[0105] Depend on and The Bode diagrams of the impedances of the flexible DC transmission system and wind turbines are obtained when the wide-band suppression strategy is added.

[0106] The phase difference margin is obtained by subtracting the phase difference corresponding to the intersection of the amplitudes of the two Bode diagrams from 180 degrees.

[0107] Solve the phase difference margin of each frequency point in the low frequency band when the wide-band oscillation suppression strategy is not used. , Phase difference margin at each frequency point in the mid-frequency band , Phase difference margin at each frequency point in the high frequency band ;

[0108] Solve the phase difference margin of each frequency point in the low frequency band when adding the wide-band oscillation suppression strategy , Phase difference margin at each frequency point in the mid-frequency band , Phase difference margin at each frequency point in the high frequency band .

[0109] Step S1.3.2: The number of low-band frequency points is defined as the low-band damping X when the widening band oscillation suppression strategy is not used. 1wv_l ;Will The number of mid-band frequency points is defined as the mid-band damping X when the widening band oscillation suppression strategy is not used. 2wv_m ;Will The number of high-band frequency points is defined as the high-band damping X when the widening band oscillation suppression strategy is not used. 3wv_h ;Will The number of low-band frequency points is defined as the low-band damping X when the wide-band oscillation suppression strategy is added 1sysact_l ;Will The number of mid-band frequency points is defined as the mid-band damping X when the wide-band oscillation suppression strategy is added. 2sysact_m ;Will The number of high-band frequency points is defined as the high-band damping X when the wide-band oscillation suppression strategy is added. 3sysact_h .

[0110] Step S2: Acquire transient index data of various working conditions with and without adding the wideband oscillation suppression strategy;

[0111] Step S2.1: Set the three-phase short circuit grounding fault at the busbar under various working conditions without and with the wide-band oscillation suppression strategy, and obtain the overshoot of the AC voltage X without the wide-band oscillation suppression strategy. 4wv_f and adjust time X 5wv_f , and the overshoot of AC voltage X with broadband oscillation suppression strategy added 4sysact_f and adjust time X 5sysact_f ;

[0112] Step S2.2: Set the AC voltage to generate a step response under various working 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 adjust time X 7wv_s , and the overshoot of AC voltage X under the wide-band oscillation suppression strategy 6sysact_s and adjust time X 7sysact_s .

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

[0114] Step S3.1: Set various operating conditions with and without the wideband oscillation suppression strategy, and obtain the total harmonic distortion rate X of the grid-side outlet current without the wideband oscillation suppression strategy. 8wv_thiAnd 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 broadband oscillation suppression strategy 8sysact_thi and the total harmonic distortion rate X of the grid-side output voltage 9sysact_thu ;

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

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

[0117] Step S4.1: The three damping performance index data (X 1 , X 2 , X 3 ), four transient performance index data (X 4 , X 5 , X 6 , X 7 ) and three steady-state performance index data (X 8 , X 9 , X 10 ), summarized as ten index data under each working condition; let X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , X 8 , X 9 , X 10 They are low-frequency band damping, medium-frequency band damping and high-frequency band damping, 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, and any one of them is marked as ;X 1 ∈{X 1wv_l , X 1sysact_l}, X 2 ∈{X 2wv_m , X 2sysact_m}, X 3 ∈{X 3wv_h , X 3sysact_h}, X 4 ∈{X 4wv_f , X 4sysact_f}, X5 ∈{X 5wv_f , X 5sysact_f}, X 6 ∈{X 6wv_s , X 6sysact_s}, X 7 ∈{X 7wv_s , X 7sysact_s}, X 8 ∈{X 8wv_thi , X 8sysact_thi}, X 9 ∈{X 9wv_thu , X 9sysact_thu}, X 10 ∈{X 10wv_s , X 10sysact_s}.

[0118] Step S4.2: Obtain the jth index under the working condition corresponding to the i-th wideband oscillation suppression strategy , using formula (11) Perform standardization to obtain the jth standardized index under the i-th working condition ;

[0119] (11)

[0120] In formula (11), 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 wide-band oscillation suppression strategies, and o+1 represents the number of operating conditions corresponding to the wide-band oscillation suppression strategy without adding it; the positive indicators include: low-frequency band damping, medium-frequency band damping and high-frequency band damping; the negative indicators 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: Calculate the jth standardized index under the i-th working condition using formula (12): The proportion p ij ;

[0122] (12)

[0123] Step S4.4: Calculate the jth standardized index under all working conditions through formula (13): Information entropy E j :

[0124] (13)

[0125] Step S4.5: Calculate the jth standardized index under all working conditions through equation (14): Weight :

[0126] (14)

[0127] Step S4.6: Calculate the robustness evaluation score under the i-th working condition by using formula (15): ;

[0128] (15)

[0129] By calculating the robustness evaluation scores of various working conditions through formulas, it is possible to intuitively quantify the impact of multiple wide-band suppression strategies on system robustness before and after they are added. This quantitative model provides a clear indicator basis for selecting the optimal suppression strategy, allowing the effects of different suppression strategies to 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, wherein the memory is used to store a program that supports the processor to execute the above method, and the processor is configured to execute the program stored in the memory.

[0131] In this embodiment, a computer-readable storage medium stores a computer program on the computer-readable storage medium, and the computer program executes the steps of the above method when executed by a processor.

[0132] The present invention also includes an oscillation suppression strategy robustness evaluation device based on transient steady-state performance and damping performance indicators, using the above method, such as Figure 3 As shown, including:

[0133] The impedance model building module is used to build the harmonic state space impedance model of the wind power flexible direct current grid-connected system before and after the addition of different wide-band oscillation suppression strategies, so as to obtain the damping index of the system in different frequency bands;

[0134] A transient and steady-state index calculation module is used to calculate the step response under transient indicators and the overshoot and adjustment time of the AC voltage under a three-phase ground short circuit fault based on the model measurement module, and calculate the total harmonic distortion rate of current and voltage and the steady-state error under steady-state indicators;

[0135] The robustness evaluation method module is used to evaluate the robustness of each broadband oscillation suppression strategy before and after adding it based on the transient steady state and damping indicators, using the weight distribution method to select the optimal broadband oscillation suppression strategy.

[0136] See also Figure 4A computer device 500 provided in an embodiment of the present application includes: a processor 510 and a memory 520, wherein the memory 520 stores a computer program executable by the processor 510, and when the computer program is executed by the processor 510, the above method is executed.

[0137] The embodiment of the present application further provides a storage medium 530 on which a computer program is stored. When the computer program is run by the processor 510, the above method is executed.

[0138] Among them, the storage medium 530 can be implemented by any type of volatile or non-volatile 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 red-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, disk or optical disk.

[0139] The present invention includes a d-axis AC voltage response diagram under a three-phase short-circuit grounding fault under different operating conditions, such as Figure 5 As shown in the figure, the adjustment time and overshoot of the d-axis AC voltage response under a three-phase short-circuit grounding fault are transient indicator data in the robustness evaluation, which reflects the dynamic performance of the wind power flexible direct current 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, the better. As can be seen from the figure, after the wide-band oscillation suppression strategy is added, the adjustment time of the three-phase short-circuit grounding fault is smaller than the operating condition without the wide-band oscillation suppression strategy, and the adjustment time of the three-phase short-circuit grounding fault is the smallest after the LC filter is added; after the wide-band oscillation suppression strategy is added, the overshoot of the three-phase short-circuit grounding fault is smaller than the operating condition without the wide-band oscillation suppression strategy, and the overshoot of the three-phase short-circuit grounding fault is the smallest after the LC filter is added;

[0140] The present invention includes a d-axis AC voltage step response diagram under different operating conditions, such as Figure 6As shown in the figure, the d-axis AC voltage step response adjustment time and overshoot are transient indicator data in the robustness evaluation, which reflects the dynamic performance of the wind power system connected to the flexible direct current grid before and after the wide-band oscillation suppression strategy is added, and the smaller the d-axis AC voltage step response adjustment time and overshoot, the better. As can be seen from the figure, after the wide-band oscillation suppression strategy is added, the d-axis AC voltage step response adjustment time is consistent with the operating condition without the wide-band oscillation suppression strategy; after the wide-band oscillation suppression strategy is added, the d-axis AC voltage step response overshoot is smaller than the operating condition without the wide-band oscillation suppression strategy, and the d-axis AC voltage step response overshoot is the smallest after the LC filter is added;

[0141] The present invention also includes a robustness evaluation score result diagram under different operating conditions, such as Figure 7 As shown in the figure, it can be seen that after adding the wide-band oscillation suppression strategy, the robustness evaluation score is greater than the operating condition without adding the wide-band oscillation suppression strategy, and the robustness evaluation score is the highest after adding the LC filter.

Claims

1. A method for evaluating the robustness of a broadband oscillation suppression strategy for a wind power grid-connected flexible direct current system, the wind power grid-connected flexible direct current system comprising: Wind turbine, collector line, flexible direct current transmission system; characterized in that the evaluation method is carried out in the following steps: Step S1: obtaining the damping index of the wind power flexible direct current grid-connected system after the wide-band oscillation suppression strategy is added; Step S1.1: Establish the harmonic state space impedance model of the wind power grid-connected system via flexible direct current when a certain broadband oscillation suppression strategy is added: Step S1.2: Obtain the harmonic linearized state space impedance of the wind power flexible direct current grid-connected system after adding the micro-disturbance component: Step S1.3: Obtain damping index data of various working conditions with and without adding the wide-band oscillation suppression strategy; Step S1.3.1: and The Bode diagrams of the impedances of the flexible DC transmission system and wind turbines are obtained without the wideband suppression strategy. Depend on and The Bode diagrams of the impedances of the flexible DC transmission system and wind turbines are obtained when the wide-band suppression strategy is added. The phase difference margin is obtained by subtracting the phase difference corresponding to the intersection of the amplitudes of the two Bode diagrams from 180 degrees. Solve the phase difference margin of each frequency point in the low frequency band when the wide-band oscillation suppression strategy is not used. , Phase difference margin at each frequency point in the mid-frequency band , Phase difference margin at each frequency point in the high frequency band ; Solve the phase difference margin of each frequency point in the low frequency band when adding the wide-band oscillation suppression strategy , Phase difference margin at each frequency point in the mid-frequency band , Phase difference margin at each frequency point in the high frequency band ; Step S1.3.2: The number of low-band frequency points is defined as the low-band damping X when the widening band oscillation suppression strategy is not used. 1wv_l ;Will The number of mid-band frequency points is defined as the mid-band damping X when the widening band oscillation suppression strategy is not used. 2wv_m ;Will The number of high-band frequency points is defined as the high-band damping X when the widening band oscillation suppression strategy is not used. 3wv_h ;Will The number of low-band frequency points is defined as the low-band damping X when the wide-band oscillation suppression strategy is added 1sysact_l ;Will The number of mid-band frequency points is defined as the mid-band damping X when the wide-band oscillation suppression strategy is added. 2sysact_m ;Will The number of high-band frequency points is defined as the high-band damping X when the wide-band oscillation suppression strategy is added. 3sysact_h ; Step S2: Acquire transient index data of various working conditions with and without adding the wideband oscillation suppression strategy; Step S3: obtaining steady-state index data of various working conditions with and without adding the wide-band oscillation suppression strategy; Step S4: Perform robustness evaluation on transient steady state and damping index data of various working conditions with and without adding the wide-band oscillation suppression strategy to obtain a robustness evaluation score.

2. The method for evaluating the robustness of a broadband oscillation suppression strategy for a wind power flexible direct current grid-connected system according to claim 1 is characterized in that: Step S1.1 includes: Step S1.1.1: At the steady-state trajectory, the wind power system connected to the flexible direct current grid is linearized, so that the linear time period system is obtained using equation (1): (1) In formula (1), x(t) and u(t) are the state variable and input variable of the wind power grid-connected system at time t, respectively; represents the differential of x(t); A(t) and B(t) are the two coefficient matrices of the wind power grid-connected system via flexible direct current at time t, and: (2) (3) (4) In formula (2)-formula (4), s is a complex variable; It is the complex exponential signal of the wind power flexible direct current grid-connected system; is the Fourier coefficient of the nth harmonic, Z is the set of harmonic orders, j is the imaginary unit, is the fundamental angular frequency of the wind power flexible direct current grid-connected system; t is the time; is the state variable under the nth harmonic; Step S1.1.2: Transform equation (1) to obtain equation (5): (5) In formula (5), is the state variable under the mth harmonic, is the input variable under the mth harmonic, and is the positive sequence component matrix and negative sequence component matrix of A(t) 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 tend to 0, and simultaneously establish the state equations of each harmonic, so as to obtain the harmonic state space impedance model of the wind power grid-connected system via flexible direct current in steady state using equation (6); (6) In formula (6), X is the state vector containing harmonics of various orders; N is the diagonal matrix reflecting frequency information; A and B are the two Toeplitz matrices of the wind power flexible direct current grid-connected system; U is the input vector containing harmonics of various orders; Step S1.1.4: Based on the harmonic state space impedance model of the wind power flexible direct current grid-connected system in steady state, the harmonic state space impedance model of the wind power flexible direct current grid-connected system after adding the micro-disturbance component under a certain wide-band oscillation suppression strategy is obtained using formula (7): (7) In formula (7), Represents the state vector of each order harmonic after adding the perturbation component; and are the two Toeplitz matrices after adding the perturbation component; Represents the input vector of each order harmonic after adding the perturbation component.

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

4. The method for evaluating the robustness of a broadband oscillation suppression strategy for a wind power flexible direct current grid-connected system according to claim 3 is characterized in that: Step S2 includes: Step S2.1: Set the three-phase short circuit grounding fault at the busbar under various working conditions without and with the wide-band oscillation suppression strategy, and obtain the overshoot of the AC voltage X without the wide-band oscillation suppression strategy. 4wv_f and adjust time X 5wv_f , and the overshoot of AC voltage X under the wide-band oscillation suppression strategy 4sysact_f and adjust time X 5sysact_f ; Step S2.2: Set the AC voltage to generate a step response under various working 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 adjust time X 7wv_s , and the overshoot of AC voltage X with broadband oscillation suppression strategy added 6sysact_s and adjust time X 7sysact_s .

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

6. The method for evaluating the robustness of a broadband oscillation suppression strategy for a wind power flexible direct current grid-connected system according to claim 5 is characterized in that: Step S4 includes: Step S4.1: Let X1, X2, X3, X4, X5, X6, X7, X8, X9, X 10 They are low-frequency band damping, medium-frequency band damping and high-frequency band damping, 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, 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 }; Step S4.2: Obtain the jth index under the working condition corresponding to the i-th wideband oscillation suppression strategy , using formula (8) Perform standardization to obtain the jth standardized index under the i-th working condition ; (8) In formula (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 wide-band oscillation suppression strategies, and o+1 represents the number of operating conditions corresponding to when the wide-band oscillation suppression strategy is not added; the positive indicators include: low-frequency band damping, medium-frequency band damping and high-frequency band damping; the negative indicators 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; Step S4.3: Calculate the jth standardized index under the i-th working condition using formula (9): The proportion p ij ; (9) Step S4.4: Calculate the jth standardized index under all working conditions through formula (10): Information entropy E j : (10) Step S4.5: Calculate the jth standardized index under all working conditions through formula (11): Weight : (11) Step S4.6: Calculate the robustness evaluation score under the i-th working condition by using formula (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 a processor to execute the evaluation method according to any one of claims 1 to 6, and the processor is configured to execute the program stored in the memory.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the evaluation method according to any one of claims 1 to 6 are executed.

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