Parameter setting method and device for grid-connected double-fed wind power plant

Abstract

The invention discloses a parameter setting method and device for a grid-connected double-fed wind power plant, and the method comprises the steps: building a full-order linear state space model based on the interaction behaviors of N fans in the grid-connected double-fed wind power plant and a power grid, and N is a positive integer; performing equivalent order reduction processing on the basis of the full-order linearization state space model to obtain N independent single grid-connected doubly-fed fan equivalent subsystem models; according to the N mutually independent single grid-connected doubly-fed fan equivalent subsystem models, constructing a dynamic characteristic equation of a grid-connected doubly-fed wind power plant under a direct-current voltage control time scale; and performing stability judgment on the dynamic characteristic equation of the grid-connected double-fed wind power plant to obtain the parameter setting method suitable for the grid-connected double-fed wind power plant under the slow time scale. According to the method, the analysis calculation amount is effectively reduced, the efficiency and feasibility of small-interference stability analysis of the wind power plant are remarkably improved, and complex large-scale wind power plant analysis is more efficient.

Description

Technical Field

[0001] The present invention relates to the technical field of wind farms, and in particular to a parameter setting method and device for a grid-connected double-fed wind farm. Background Art

[0002] With the rapid growth of demand for clean energy, wind energy, as an important renewable energy, has increased its share in the energy structure year by year. At present, wind farms have become an important part of the power system. At the same time, with the gradual increase in wind power grid-connected installed capacity, the impact of wind farms on the safe and stable operation of the power grid has become increasingly prominent, and the stability problem of wind farm grid connection needs to be solved urgently. Summary of the invention

[0003] In view of the problems in the prior art, the embodiments of the present invention provide a parameter setting method and device for a grid-connected double-fed wind farm. The present invention decomposes the high-order state space model of a complex large-scale grid-connected double-fed wind farm into multiple independent subsystem models, significantly reducing the complexity of the model while retaining the original dynamic characteristics. This processing method not only effectively reduces the amount of calculation in the analysis process, but also significantly improves the efficiency and feasibility of small-disturbance stability analysis of wind farms, making the analysis of complex large-scale wind farms more efficient.

[0004] The embodiment of the present invention provides a parameter setting method for a grid-connected double-fed wind farm, comprising:

[0005] A full-order linearized state space model of the interaction between N wind turbines and the power grid in a grid-connected doubly-fed wind farm is established, where N is a positive integer.

[0006] Based on the full-order linearized state space model, equivalent order reduction processing is performed to obtain N mutually independent single grid-connected double-fed wind turbine equivalent subsystem models;

[0007] According to the N mutually independent single grid-connected double-fed wind turbine equivalent subsystem models, a dynamic characteristic equation of a grid-connected double-fed wind farm under a DC voltage control time scale is constructed;

[0008] The stability of the dynamic characteristic equation of the grid-connected double-fed wind farm is judged, and a parameter setting method suitable for the grid-connected double-fed wind farm under a slow time scale is obtained.

[0009] In one embodiment, the establishment of a full-order linearized state-space model based on the interactive behavior between N wind turbines and the power grid in a grid-connected doubly-fed wind farm includes: obtaining a full-order linearized state-space model based on the interactive behavior between N wind turbines and the power grid in a grid-connected doubly-fed wind farm according to the state space system matrix of the grid-connected doubly-fed wind farm, the state variable column vector of the grid-connected doubly-fed wind farm, and the wind farm network impedance matrix.

[0010] In one embodiment, the equivalent order reduction processing based on the full-order linearized state space model to obtain N independent single grid-connected doubly fed wind turbine equivalent subsystem models includes: performing a similarity diagonal transformation on the state space system matrix of the grid-connected doubly fed wind farm, and then equivalently reducing the full-order linearized state space model into N independent single grid-connected doubly fed wind turbine equivalent subsystem models.

[0011] In one embodiment, the construction of the dynamic characteristic equation of the grid-connected doubly-fed wind farm under the DC voltage control time scale based on the N mutually independent single grid-connected doubly-fed wind turbine equivalent subsystem models includes:

[0012] According to the dynamic behaviors of rotor-side converter, grid-side converter and ideal phase-locked loop, an overall simplified model is constructed;

[0013] Combining the overall simplified model with the line model of the grid-connected double-fed wind farm, a reduced-order characteristic equation of the grid-connected double-fed wind farm under the DC voltage control time scale is obtained;

[0014] According to the reduced-order characteristic equation and the N mutually independent equivalent subsystem models of single grid-connected doubly-fed wind turbines, a dynamic characteristic equation of a grid-connected doubly-fed wind farm under a DC voltage control time scale is obtained.

[0015] In one embodiment, the method of performing stability judgment on the dynamic characteristic equation of the grid-connected doubly fed wind farm to obtain a parameter setting method suitable for the grid-connected doubly fed wind farm under a slow time scale includes: performing stability judgment on the dynamic characteristic equation of the grid-connected doubly fed wind farm through the Routh-Hurwitz criterion to obtain a parameter setting method suitable for the grid-connected doubly fed wind farm under a slow time scale.

[0016] In one embodiment, the method of determining the stability of the dynamic characteristic equation of the grid-connected doubly-fed wind farm by using the Routh-Hurwitz criterion to obtain a parameter setting method suitable for the grid-connected doubly-fed wind farm under a slow time scale includes:

[0017] According to the Routh-Hurwitz criterion, the stability condition of the dynamic characteristic equation of the grid-connected doubly-fed wind farm is obtained;

[0018] Simplifying the coefficients in the dynamic characteristic equation of the grid-connected double-fed wind farm into an algebraic expression about the line equivalent impedance;

[0019] According to the algebraic expression and the stability condition, a slow stability criterion between the grid-connected double-fed wind turbine generator set and the line equivalent reactance under the DC voltage control time scale is obtained;

[0020] The parameters of the full-order linearized state space model are set to meet the slow stability criterion, so that the grid-connected double-fed wind farm can operate stably at a slow time scale.

[0021] The embodiment of the present invention further provides a parameter setting device for a grid-connected double-fed wind farm, comprising:

[0022] A model building module is used to establish a full-order linearized state space model based on the interaction behavior between N wind turbines and the power grid in a grid-connected double-fed wind farm, where N is a positive integer;

[0023] An equivalent order reduction module is used to perform equivalent order reduction processing based on the full-order linearized state space model to obtain N independent equivalent subsystem models of single grid-connected double-fed wind turbines;

[0024] A dynamic characteristic equation construction module, used to construct a dynamic characteristic equation of a grid-connected double-fed wind farm under a DC voltage control time scale according to the N mutually independent single grid-connected double-fed wind turbine equivalent subsystem models;

[0025] The parameter setting module is used to judge the stability of the dynamic characteristic equation of the grid-connected double-fed wind farm and obtain a parameter setting method suitable for the grid-connected double-fed wind farm under a slow time scale.

[0026] An embodiment of the present invention further provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements any of the above methods when executing the computer program.

[0027] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, any of the above methods is implemented.

[0028] An embodiment of the present invention further provides a computer program product, wherein the computer program product includes a computer program, and when the computer program is executed by a processor, any of the above methods is implemented.

[0029] The embodiment of the present invention provides a parameter setting method and device for a grid-connected doubly-fed wind farm. The present invention significantly reduces the complexity of the model while retaining the original dynamic characteristics by decomposing the high-order state space model of a complex large-scale grid-connected doubly-fed wind farm into multiple independent subsystem models. This processing method not only effectively reduces the amount of calculation in the analysis process, but also significantly improves the efficiency and feasibility of small-disturbance stability analysis of wind farms, making complex large-scale wind farm analysis more efficient. The derived characteristic equation fully considers the dynamic characteristics of the rotor-side converter power control and the grid-side converter DC voltage control link, and can more accurately describe the stability behavior and its influence mechanism of the doubly-fed wind turbine control system under the DC voltage time scale, providing a more intuitive basis for stability analysis; the proposed parameter setting method can provide effective guidance for the stability analysis and control parameter adjustment of large-scale grid-connected doubly-fed wind farms, and improve the grid-connected stability and reliability of wind farms. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0031] Figure 1 A flow chart of a parameter setting method for a grid-connected double-fed wind farm is provided for an embodiment of the present invention;

[0032] Figure 2 A topological diagram of a grid-connected double-fed wind farm provided by an embodiment of the present invention;

[0033] Figure 3 A topological diagram of a single grid-connected double-fed wind turbine provided in an embodiment of the present invention;

[0034] Figure 4 A schematic diagram of the steps of a method for constructing a dynamic characteristic equation of a grid-connected double-fed wind farm under a DC voltage control time scale provided by an embodiment of the present invention;

[0035] Figure 5 A schematic diagram of the coordinate transformation relationship between the output current and the terminal voltage of a doubly-fed wind turbine phase-locked loop provided by an embodiment of the present invention;

[0036] Figure 6 A flow chart of a parameter setting method for a grid-connected double-fed wind farm under a slow time scale provided by an embodiment of the present invention;

[0037] Figure 7It is a schematic diagram of simulation results under different line impedances listed in Table 1;

[0038] Figure 8 It is a schematic diagram of simulation results under different numbers of fans listed in Table 2;

[0039] Fig. 9 A schematic diagram of the structure of a parameter setting device for a grid-connected double-fed wind farm provided by an embodiment of the present invention;

[0040] Fig.10 A schematic diagram of the physical structure of a computer device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0042] In order to facilitate understanding of the technical solution provided by the present invention, the research background of the technical solution of the present invention is briefly described below.

[0043] Doubly-fed wind turbines are one of the most widely used large-scale wind farm grid-connected technologies. Their unique adjustment flexibility makes them occupy an important position in wind power grid-connected systems. The grid-connected control of doubly-fed wind turbines relies on converters and their control systems to ensure that wind turbines can operate safely and stably. Since the control system of doubly-fed wind turbines involves dynamic characteristics of multiple different time scales, including AC current control time scale, DC voltage control time scale, and electromechanical control time scale, they exhibit unique dynamic characteristics at different time scales. Most of the current research focuses on the dynamic behavior of wind power systems at fast time scales, especially at the AC current control time scale. However, the research on the stable operation of wind farms at slow time scales (such as DC voltage control time scale) is relatively weak.

[0044] Therefore, in order to ensure the stability of large-scale grid-connected doubly-fed wind farms under slow time scales, an effective parameter setting method is urgently needed to ensure the stable operation of doubly-fed wind power systems under slow time scales. Reasonable control parameter setting can improve the dynamic response of wind farms, thereby ensuring the stable grid connection of wind farms under different operating conditions and providing technical support for large-scale wind power grid connection.

[0045] like Figure 1 The figure shows a flow chart of a parameter setting method for a grid-connected double-fed wind farm provided by an embodiment of the present invention. The embodiment of the present invention provides a parameter setting method for a grid-connected double-fed wind farm, the method comprising:

[0046] S1. Establish a full-order linearized state space model based on the interaction behavior between N wind turbines and the power grid in a grid-connected doubly-fed wind farm, where N is a positive integer.

[0047] In one embodiment, the establishment of a full-order linearized state-space model based on the interactive behavior between N wind turbines and the power grid in a grid-connected doubly-fed wind farm includes: obtaining a full-order linearized state-space model based on the interactive behavior between N wind turbines and the power grid in a grid-connected doubly-fed wind farm according to the state space system matrix of the grid-connected doubly-fed wind farm, the state variable column vector of the grid-connected doubly-fed wind farm, and the wind farm network impedance matrix.

[0048] Specifically, Figure 2 The topology diagram of a grid-connected doubly-fed wind farm provided by an embodiment of the present invention is shown. Considering the complexity of a large-scale grid-connected doubly-fed wind farm, it is assumed that the grid-connected doubly-fed wind farm includes N doubly-fed wind turbines, and these wind turbines are connected to the busbar B through M branches. The doubly-fed wind turbines in each branch are connected to the busbar B of the wind farm grid connection point in series, and the branches are connected in parallel. The wind farm grid connection point is connected to the busbar B through the external transmission line x L Connect to external power system, x1-x N is the internal line impedance of the wind farm.

[0049] Assume that the state space equation of the kth doubly fed wind turbine is as follows:

[0050]

[0051] Among them, X k A represents the state variable column vector of the kth doubly fed wind turbine, k , B k , C k are the system matrix, input matrix, and output matrix of the doubly fed wind turbine respectively. k =[I kx I ky ] T and U k =[U kx U ky ] T are the output current and voltage vectors of the kth doubly fed wind turbine at the grid connection point, and Δ represents a small increment of the corresponding variables.

[0052] Furthermore, suppose the kth doubly fed wind turbine is connected to the jth branch in the wind farm, Figure 1 It can be seen that the flow through x k The current is 1+N j-1 ~N j The sum of the currents of the units is In addition, the line reactance connecting the kth wind turbine to the k+1th wind turbine is x k , so x k(k≠N j ) can be expressed as:

[0053]

[0054] Where ω0 is the power frequency of the AC power grid in steady state, U kx , U ky is the x-axis and y-axis grid connection point voltage of the kth wind turbine, U (k+1)x , U (k+1)y is the x-axis and y-axis grid connection point voltage of the k+1th wind turbine; ΔI lkx and ΔI lky are the x-axis and y-axis grid-connected point currents of the kth wind turbine respectively.

[0055] The following equation can be derived from the above formula:

[0056]

[0057] Where s is the differential operator and E2 is the second-order unit matrix.

[0058] When k = N j When , the kth fan is directly connected to the busbar B, satisfying the equation:

[0059]

[0060] Among them, U B =[U Bx U By ] T is the voltage vector at bus B terminal;

[0061]

[0062] is the sum of the currents of N wind turbines in the wind farm.

[0063] From the above formula, we can get the following relationship:

[0064]

[0065] Furthermore, the following equation can be derived:

[0066]

[0067] The following overall network equation of the wind farm can be further derived:

[0068] ΔU=X G ΔI;

[0069] Where, ΔU=[ΔU1 T ΔU2 T… ΔU N T ] T is the voltage column vector of the grid-connected node of N wind turbines in the wind farm, ΔI=[ΔI1 T ΔI2 T … ΔI N T ] T is the output current column vector, and:

[0070]

[0071] in, is the transformation matrix, s is the differential operator, ω0 is the power frequency, x 11 -x NN is the internal impedance of the wind farm.

[0072] Therefore, for the grid-connected double-fed wind farm, the network reactance matrix can be defined as:

[0073]

[0074] Therefore, the full-order linearized state space model can be derived by combining the state space model and the network equation:

[0075]

[0076] Among them, A DFIG is the state space system matrix, ΔX DFIG =[ΔX1 T ΔX2 T …ΔX N T ] T is the column vector of state variables of the grid-connected double-fed wind farm, and A DFIG =diag(A k )+diag(B k )X G diag(C k ), where diag(A k )、diag(B k ) and diag(C k ) represent A k , B k and C k (k=1,2,…,N) is a block diagonal matrix with diagonal elements, X G is the wind farm network impedance matrix.

[0077] According to the above derivation, the above formula is Figure 2 The full-order linearized state space model of the grid-connected doubly-fed wind farm is shown.

[0078] S2. Perform equivalent order reduction processing based on the full-order linearized state space model to obtain N independent equivalent subsystem models of single grid-connected doubly-fed wind turbines.

[0079] In one embodiment, the equivalent order reduction processing based on the full-order linearized state space model to obtain N independent single grid-connected doubly fed wind turbine equivalent subsystem models includes: performing a similarity diagonal transformation on the state space system matrix of the grid-connected doubly fed wind farm, and then equivalently reducing the full-order linearized state space model into N independent single grid-connected doubly fed wind turbine equivalent subsystem models.

[0080] Specifically, in actual production, wind turbines in the same wind farm usually use the same model and come from the same manufacturer, so their initial parameter settings are very close or exactly the same. Although external factors such as changes in wind speed may cause certain differences in the steady-state operating points of each wind turbine, when the parameter settings and models are basically the same, this difference will not cause significant changes in the linearized models between wind turbines. Therefore, it can be considered that the dynamic characteristics of each wind turbine in the wind farm are approximately the same. Based on this assumption, it is assumed that the dynamic characteristics of all wind turbines in the power farm are the same, that is, the differences in the linearized models between them are not considered, so that the state matrix, input matrix, and output matrix of the Kth wind turbine are expressed as follows:

[0081] A k =A c ,B k =B c ,C k =C c ,k=1,2,…,N;

[0082] Among them, A k ,B k ,C k They are the state matrix, input matrix and output matrix of the Kth wind turbine respectively.

[0083] Under this premise, the state matrix, input matrix, and output matrix of the Kth wind turbine are substituted into the full-order linearized state space model, and the following is obtained:

[0084]

[0085] Let λ k (k=1,2,…,N) is the wind farm network reactance matrix X gr The eigenvalues ​​of , then there exists the following matrix:

[0086]

[0087] In the formula, diag(λ k ) represents the k(k=1,2,…,N) is a diagonal matrix with main diagonal elements, x 11 -x NN is the internal impedance matrix element of the wind farm,

[0088] Therefore, the similar diagonal transformation matrix can be defined as:

[0089]

[0090] In the formula, the order of the linear model of a single doubly fed wind turbine is n, E n is the n-th order identity matrix.

[0091] Further we can get:

[0092]

[0093] Make an equivalent transformation ΔX DFIG =Q fc ΔY DFIG , combined with the full-order linearized state space model and the state matrix, input matrix, and output matrix of the Kth wind turbine, we can obtain:

[0094] sΔY DFIG =Q fc -1 diag(A c )Q fc ΔY DFIG +Q fc -1 diag(B c )X G diag(C c )Q fc ΔY DFIG ;

[0095] In the formula, A c , B c , C c , is the state matrix, input matrix, and output matrix of the wind turbine, Y DFIG is the equivalent fan model, X G is the wind farm network impedance matrix.

[0096] Further we can get:

[0097] Q fc -1 diag(A c )Q fc =diag(A c );

[0098] Further we can get:

[0099]

[0100] In the formula, λ k is the characteristic value of the equivalent impedance corresponding to the kth wind turbine.

[0101] Further we can get:

[0102] Q fc -1 A DFIG Q fc =A pd ;

[0103] In the formula,

[0104] According to the above formula, the matrix A pd With the matrix A DFIG is a similar matrix, and the eigenvalues ​​of the two are the same, indicating that the fan systems they correspond to have the same dynamic characteristics. pd It can be seen that the original wind farm can be equivalent to N independent subsystems, which have consistent dynamic characteristics. The model of the kth equivalent subsystem can be expressed as:

[0105]

[0106] In the formula, represents the state matrix of the kth equivalent subsystem model, E n is the n-th order identity matrix.

[0107] like Figure 3 The figure shows a topology diagram of a single grid-connected double-fed wind turbine provided by an embodiment of the present invention. Figure 3 The equivalent subsystem model of the grid-connected double-fed wind turbine is shown in Figure 2. It can be seen from the equivalent subsystem model of the grid-connected double-fed wind turbine that the kth equivalent subsystem can be regarded as a single double-fed wind turbine with reactance λ. k The transmission line is connected to the wind farm grid-connected port A. DFIG is the wind turbine grid connection point voltage, I ac Its output current phasor, U A is the terminal voltage phasor of the wind farm grid-connected port A.

[0108] It is worth noting that the dynamic characteristics of a doubly-fed wind farm are jointly determined by its internal line dynamics and the control characteristics of the doubly-fed wind turbine. In a doubly-fed wind farm, the dynamic response of the wind turbine is affected by the time scales of multiple control links. Specifically, the rotor speed control is located at the speed time scale (1 second level), the DC voltage control outer loop is at the DC voltage time scale (0.1 second level), and the AC current control inner loop is at the AC current time scale (0.01 second level). Different control links act on oscillations in different frequency bands, so it can be considered that the stability problems at each time scale are decoupled to a certain extent, so that the stability of the wind farm can be discussed separately at different time scales. In this study, only the dynamic characteristics of the rotor-side converter control outer loop and the grid-side converter outer loop at the DC voltage time scale are focused on, so as to further analyze the influence of the configuration of control parameters at this time scale on the small disturbance stability of the wind farm.

[0109] S3. Based on the N mutually independent equivalent subsystem models of single grid-connected doubly-fed wind turbines, a dynamic characteristic equation of a grid-connected doubly-fed wind farm under a DC voltage control time scale is constructed.

[0110] like Figure 4 The figure shows a schematic diagram of the steps of a method for constructing a dynamic characteristic equation of a grid-connected double-fed wind farm under a DC voltage control time scale provided by an embodiment of the present invention. In one embodiment, the method of constructing a dynamic characteristic equation of a grid-connected double-fed wind farm under a DC voltage control time scale based on the N mutually independent single grid-connected double-fed wind turbine equivalent subsystem models includes:

[0111] S301, constructing an overall simplified model according to the dynamic behaviors of the rotor-side converter, the grid-side converter and the ideal phase-locked loop;

[0112] S302, combining the overall simplified model and the line model of the grid-connected doubly-fed wind farm to obtain a reduced-order characteristic equation of the grid-connected doubly-fed wind farm under a DC voltage control time scale;

[0113] S303: According to the reduced-order characteristic equation and the N mutually independent single grid-connected doubly-fed wind turbine equivalent subsystem models, a dynamic characteristic equation of the grid-connected doubly-fed wind farm under a DC voltage control time scale is obtained.

[0114] Specifically, in a grid-connected doubly-fed wind turbine, the DC capacitance equation between the rotor-side converter and the grid-side converter can be expressed as:

[0115]

[0116] Where V dc0 Represents the steady-state value of DC voltage, C is the DC capacitance; ΔP r and ΔP nare the active power output from the rotor-side converter and the active power output to the grid-side converter, respectively. The linearized equation is:

[0117]

[0118] Where V sd0 、V sq0 ,I sd0 ,I sq0 are the steady-state values ​​of the d-axis voltage, q-axis voltage, d-axis current, and q-axis current of the grid-side converter respectively; V rd0 、V rq0 ,I rd0 ,I rq0 They are the steady-state values ​​of the d-axis voltage, q-axis voltage, d-axis current and q-axis current of the rotor-side converter respectively.

[0119] Furthermore, the state equations of the rotor-side converter outer loop control and the grid-side converter outer loop control are expressed as follows:

[0120]

[0121] In the formula, Δx1 and Δx2 are the intermediate variables of the active power outer loop control and reactive power outer loop control of the rotor side converter, respectively, and Δx3 is the DC voltage state quantity corresponding to the outer loop control of the grid side converter; They are respectively the amplification factors of the active outer loop, reactive outer loop and DC voltage outer loop control integral link.

[0122] The linearized equations of the rotor-side converter, rotor voltage and stator can be expressed as:

[0123]

[0124] Where: and are the proportional link coefficients of the active outer loop, reactive outer loop, q-axis inner loop and d-axis inner loop respectively; P sref , P s , Q sref , Q s They are the reference value and actual value of active power, and the reference value and actual value of reactive power respectively; I rdref ,I rqref is the reference value of the d-axis and q-axis components of the inner current loop; I rd ,I rq is the actual value of the d-axis and q-axis components of the inner current loop; X m is the magnetizing reactance; X ss =X m +X s , where X s is the stator leakage reactance.

[0125] like Figure 5 The figure shows a schematic diagram of the coordinate transformation relationship between the output current and terminal voltage of a doubly-fed wind turbine phase-locked loop provided by an embodiment of the present invention. In the figure, the phase angle difference between the dq axis and the xy axis includes two parts, namely the phase angle difference caused by the dynamics of the phase-locked loop itself and the line impedance. The corresponding coordinate transformation formula can be expressed as:

[0126]

[0127] Where ΔV xy =[ΔV x ΔV y ] T ; ΔI xy =[ΔI x ΔI y ] T ; is the small disturbance component of the port voltage vector and output current vector of the double-fed wind turbine in the xy common coordinate system; θ0 is the initial value of the phase angle, and Δθ is the phase angle state quantity. I dq and V dq are the components of current and voltage in the dq coordinate system respectively.

[0128] Since the research focus of the present invention is the outer loop control of the DC voltage time scale, the inner loop control dynamics of the phase-locked loop, rotor-side converter and grid-side converter are relatively fast, and their response time is much smaller than the DC voltage control time scale, so the dynamic effects of these inner loops can be ignored in the model.

[0129] Then we can get:

[0130]

[0131] In the formula, I sd , I sq , are the grid-side converter d-axis current, the grid-side converter d-axis current reference value, the grid-side converter q-axis current, and the grid-side converter q-axis current reference value respectively; I rd , I rq , They are respectively the d-axis current of the rotor side converter, the d-axis current reference value of the rotor side converter, the q-axis current of the rotor side converter, and the q-axis current reference value of the rotor side converter.

[0132] When analyzing the dynamics of wind farms on the DC voltage time scale, the dynamic behaviors of the rotor-side converter, the grid-side converter, and the ideal phase-locked loop can be combined into an overall simplified model. The core idea of ​​this simplified processing is to ignore high-frequency dynamic effects such as inner loop control, thereby greatly reducing the complexity of the wind power system and simplifying the modeling of the wind farm control link. On this basis, combined with the line model of the grid-connected wind farm and the overall simplified model, the reduced-order characteristic equation of the doubly fed wind farm on the DC voltage time scale can be obtained.

[0133] Furthermore, by substituting this reduced-order model into the equivalent subsystem model of the grid-connected doubly-fed wind farm, the dynamic characteristic equation of the grid-connected wind farm can be derived as follows:

[0134] d c4 s 4 +d c3 s 3 +d c2 s 2 +d c1 s+d c0 =0;

[0135] Among them, d c4 d c3 d c2 d c1 d c0 They represent the coefficients in the characteristic equation respectively, which are related to parameters such as the rotor-side converter, the grid-side converter, and the ideal phase-locked loop.

[0136] That is, in order to facilitate model construction, the present invention focuses on hardware equipment such as the rotor-side converter, the grid-side converter, and the ideal phase-locked loop, and constructs an overall simplified model according to the parameters in the rotor-side converter, the grid-side converter, and the ideal phase-locked loop.

[0137] The coefficients of the above characteristic equation can be specifically expressed as:

[0138]

[0139]

[0140]

[0141] S4. Perform stability judgment on the dynamic characteristic equation of the grid-connected double-fed wind farm to obtain a parameter setting method suitable for the grid-connected double-fed wind farm under a slow time scale.

[0142] In one embodiment, the stability of the dynamic characteristic equation of the grid-connected doubly fed wind farm is judged to obtain a parameter setting method suitable for the grid-connected doubly fed wind farm under a slow time scale, including: judging the stability of the dynamic characteristic equation of the grid-connected doubly fed wind farm by the Routh-Hurwitz criterion to obtain a parameter setting method suitable for the grid-connected doubly fed wind farm under a slow time scale.

[0143] like Figure 6 The flowchart of a parameter setting method for a grid-connected double-fed wind farm under a slow time scale provided by an embodiment of the present invention is shown. In one embodiment, the stability of the dynamic characteristic equation of the grid-connected double-fed wind farm is judged by the Routh-Hurwitz criterion, and the parameter setting method for the grid-connected double-fed wind farm under a slow time scale is obtained, which includes:

[0144] S401, obtaining a stability condition of the dynamic characteristic equation of the grid-connected doubly-fed wind farm according to the Routh-Hurwitz criterion;

[0145] S402, simplifying the coefficients in the dynamic characteristic equation of the grid-connected doubly-fed wind farm into an algebraic expression about the line equivalent impedance;

[0146] S403, according to the algebraic expression and the stability condition, obtaining a slow stability criterion between the grid-connected double-fed wind turbine generator set and the line equivalent reactance under the DC voltage control time scale;

[0147] S404: Setting parameters of the full-order linearized state space model to meet the slow stability criterion, so that the grid-connected double-fed wind farm can operate stably at a slow time scale.

[0148] Specifically, the stability of a wind power system is closely related to the distribution of the roots of its characteristic equation. According to control theory, a necessary and sufficient condition for the stable operation of a wind farm is that all eigenvalues ​​of the characteristic equation are located on the left half of the complex plane. Using the Routh-Hurwitz criterion, the stability condition of the equivalent subsystem model of a doubly-fed wind farm for the dynamic characteristic equation of a grid-connected wind farm can be obtained as shown below.

[0149]

[0150] In order to further analyze the stability condition, the coefficients in the characteristic equation are first simplified to the equivalent impedance η of the line. k The algebraic expression is as follows:

[0151]

[0152] Substituting this algebraic expression into the above stability condition, we can deduce that the equivalent reactance η of the doubly-fed wind turbine and the line under the DC voltage time scale isk The slow stability criterion between is as follows.

[0153] η k <z L ;

[0154] The slow stability condition of the doubly fed wind farm is given in the formula.

[0155] Among them, z L yes The smallest positive real root of the formula, the coefficient d i It is only related to the system parameters such as the grid-side converter, the proportional-integral controller of the rotor-side converter, the line impedance and capacitance. Only when the conditions of the slow stability criterion are met, the wind farm will operate stably at the slow time scale.

[0156] Considering the wind farm network matrix X F is a real symmetric matrix, and all elements of the matrix are positive real numbers, so its eigenvalues ​​are all greater than zero. In particular, the subsystem with the largest real part of the eigenvalue usually has the worst stability. Therefore, when the wind turbine subsystem with the largest real part of the eigenvalue operates stably, the entire wind farm will remain stable. Therefore, let X F The maximum eigenvalue of max , and then we can get the following formula:

[0157] η max <z L .

[0158] Next, the dynamic characteristic equation of the grid-connected wind farm is simplified to obtain an algebraic polynomial about P0:

[0159]

[0160] In the formula, are the coefficients of this equation.

[0161] By substituting the algebraic polynomial into the aforementioned stability condition, the low-frequency stability criterion of the doubly-fed wind turbine at rated active power P0 can be derived as follows:

[0162] P0<z P ;

[0163] In the formula, z P Yes The smallest positive real root of the formula, the coefficient e i ; i=0,1,2,…9 is related to the outer loop proportional integral coefficient and operating parameters of the grid-side and rotor-side converters. The above formula is the power analysis criterion for the stable operation of the doubly fed wind turbine under the DC voltage time scale. Only when the control parameters meet the low-frequency stability criterion can the doubly fed wind turbine maintain stable operation with small disturbances under the slow time scale.

[0164] The stability analysis method of the doubly-fed wind farm provided by the present invention includes a stability analysis and parameter setting method, which can effectively evaluate and adjust the stability of the wind power system. Specifically, the increase in the external transmission line reactance of the grid-connected doubly-fed wind turbine will lead to an increase in the equivalent impedance of the wind power system, thereby increasing the risk of instability of the wind power system. Therefore, the control parameters of the doubly-fed wind turbine must satisfy η max <z L To ensure stable operation. P The maximum load condition of the wind power system is defined. P The two results show that under weak connection or heavy load conditions, the stability limit of the doubly fed wind turbine on a slow time scale is low, and the risk of instability of the wind power system is increased.

[0165] By using these criteria, when judging the stability of the doubly fed wind turbine at the DC voltage scale, there is no need to build a complete high-order wind power system model. Only certain key parameters of the wind power system need to be substituted into the above formula to quickly judge the stability of the doubly fed wind turbine at the DC voltage time scale. At the same time, the control parameters and operating parameters can be adjusted to increase the limit of stable operation of the wind farm, which greatly simplifies the computational complexity of the stability analysis.

[0166] The feasibility and effectiveness of the above method will be verified by specific examples below.

[0167] In one embodiment, the present invention uses a grid-connected wind farm consisting of 15 double-fed wind turbines as an example to verify the effectiveness of the above parameter setting method. The wind farm is connected to the external AC system via a long line. In the analysis of the present invention, since the wind turbines are approximately considered to be isomorphic, the double-fed wind farm can be equivalent to one equivalent wind turbine and equivalent reactance according to the above theory. The simulation sets the output power P of each double-fed wind turbine k0 is 0.2, and the fan related parameters are substituted into η max <z L The stability index z of the wind power system can be calculated L =2.75. This index is affected by two main factors: the equivalent transmission line reactance when connected to the grid, and the number of wind turbines in the wind farm. Tables 1 and 2 list the stability analysis criteria results for different line impedances and different numbers of wind turbines, respectively. Table 1 shows the calculation results for the criteria for different impedances of the collector line, and Table 2 shows the calculation results for different numbers of wind turbines N.

[0168] Table 1

[0169] <![CDATA[x L ]]> <![CDATA[η max ]]> Judgment results Oscillation mode 0.18 2.7 Stablize -0.47±j58.02 0.19 2.85 Unstable 0.11±j53.41

[0170] Table 2

[0171] N <![CDATA[η max ]]> Judgment results Oscillation mode 14 2.5 Stablize -1.13±j52.21 17 3.2 Unstable 0.64±j50.09

[0172] It can be seen from Table 1 that as the reactance of the wind power system transmission line increases (i.e., the short-circuit ratio decreases and the connection strength of the wind power system weakens), the dominant characteristic mode of the wind power system gradually moves to the right of the complex plane and eventually crosses the imaginary axis, causing the wind farm output power to become unstable. L =0.18, S CR =1.85,η max =2.7, the wind farm meets the stability analytical criterion z L , the output power stability is high; however, when the line reactance increases, that is, x L =0.19, S CR =1.75,η max =2.85, which is greater than the stability analytical criterion z L The change of characteristic roots leads to the appearance of positive real roots, which in turn leads to unstable output power of the wind farm. This verifies that the stability analytical criterion method proposed in the present invention can effectively judge the stability of the wind farm.

[0173] It can be seen from Table 2 that the increase in the number of wind turbines in the wind farm will lead to a gradual decrease in the stability of the grid-connected wind farm under the DC voltage time scale. The results of the mode analysis and the stability analytical criterion are highly consistent, which proves the correctness and reliability of the proposed stability analysis method and parameter setting method.

[0174] In order to further verify the effectiveness of the stability analytical criterion, the present invention conducted nonlinear simulation tests under different line reactances and numbers of wind turbines. The disturbance in the simulation was set as follows: at 0.5 seconds, the wind speed of the No. 1 double-fed wind turbine increased by 5% and recovered at 0.55 seconds. By comparing with the results of the stability analytical criterion, the effectiveness of the criterion method in judging the stable operation of the wind farm was further confirmed.

[0175] like Figure 7 The following is a schematic diagram of the simulation results under different line impedances listed in Table 1. Figure 8 The following is a schematic diagram of the simulation results under different numbers of fans listed in Table 2. Figure 7 and Figure 8 The dynamic changes of active power response of wind power system under different conditions are shown respectively.

[0176] like Fig. 9 The figure is a schematic diagram of the structure of a parameter setting device for a grid-connected double-fed wind farm provided by an embodiment of the present invention. The embodiment of the present invention also provides a parameter setting device for a grid-connected double-fed wind farm, including:

[0177] A model building module is used to establish a full-order linearized state space model based on the interaction behavior between N wind turbines and the power grid in a grid-connected double-fed wind farm, where N is a positive integer;

[0178] An equivalent order reduction module is used to perform equivalent order reduction processing based on the full-order linearized state space model to obtain N independent equivalent subsystem models of single grid-connected double-fed wind turbines;

[0179] A dynamic characteristic equation construction module, used to construct a dynamic characteristic equation of a grid-connected double-fed wind farm under a DC voltage control time scale according to the N mutually independent single grid-connected double-fed wind turbine equivalent subsystem models;

[0180] The parameter setting module is used to judge the stability of the dynamic characteristic equation of the grid-connected double-fed wind farm and obtain a parameter setting method suitable for the grid-connected double-fed wind farm under a slow time scale.

[0181] It is worth noting that the method embodiments of the present invention and the aforementioned virtual device embodiments can be implemented one-to-one, and will not be described in detail herein.

[0182] An embodiment of the present invention further provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements any of the above methods when executing the computer program.

[0183] like Fig.10 The figure shows a physical structure diagram of a computer device provided by an embodiment of the present invention, wherein the computer device includes a processor, a memory and a bus, wherein the processor and the memory communicate with each other via the bus.

[0184] The processor is used to call the program instructions in the memory to execute the methods provided by the above-mentioned method embodiments.

[0185] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, any of the above methods is implemented.

[0186] An embodiment of the present invention further provides a computer program product, wherein the computer program product includes a computer program, and when the computer program is executed by a processor, any of the above methods is implemented.

[0187] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0188] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0189] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0190] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0191] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A parameter setting method for a grid-connected double-fed wind farm, characterized in that: include: A full-order linearized state space model of the interaction between N wind turbines and the power grid in a grid-connected doubly-fed wind farm is established, where N is a positive integer. Based on the full-order linearized state space model, equivalent order reduction processing is performed to obtain N mutually independent single grid-connected double-fed wind turbine equivalent subsystem models; According to the N mutually independent single grid-connected double-fed wind turbine equivalent subsystem models, a dynamic characteristic equation of a grid-connected double-fed wind farm under a DC voltage control time scale is constructed; The stability of the dynamic characteristic equation of the grid-connected double-fed wind farm is judged, and a parameter setting method suitable for the grid-connected double-fed wind farm under a slow time scale is obtained.

2. The method according to claim 1, characterized in that: The method of establishing a full-order linearized state space model based on the interactive behavior between N wind turbines and the power grid in a grid-connected doubly-fed wind farm comprises: obtaining a full-order linearized state space model based on the interactive behavior between N wind turbines and the power grid in a grid-connected doubly-fed wind farm according to a state space system matrix of the grid-connected doubly-fed wind farm, a state variable column vector of the grid-connected doubly-fed wind farm, and a wind farm network impedance matrix.

3. The method according to claim 1 or 2, characterized in that: The equivalent order reduction processing based on the full-order linearized state space model to obtain N mutually independent single grid-connected double-fed wind turbine equivalent subsystem models includes: performing a similarity diagonal transformation on the state space system matrix of the grid-connected double-fed wind farm, and then equivalently reducing the full-order linearized state space model into N mutually independent single grid-connected double-fed wind turbine equivalent subsystem models.

4. The method according to claim 1, characterized in that: The dynamic characteristic equation of the grid-connected doubly-fed wind farm under the DC voltage control time scale is constructed according to the N mutually independent single grid-connected doubly-fed wind turbine equivalent subsystem models, including: According to the dynamic behaviors of rotor-side converter, grid-side converter and ideal phase-locked loop, an overall simplified model is constructed; Combining the overall simplified model with the line model of the grid-connected double-fed wind farm, a reduced-order characteristic equation of the grid-connected double-fed wind farm under the DC voltage control time scale is obtained; According to the reduced-order characteristic equation and the N mutually independent equivalent subsystem models of single grid-connected doubly-fed wind turbines, a dynamic characteristic equation of a grid-connected doubly-fed wind farm under a DC voltage control time scale is obtained.

5. The method according to claim 1, characterized in that: The method of performing stability judgment on the dynamic characteristic equation of the grid-connected doubly-fed wind farm to obtain a parameter setting method suitable for the grid-connected doubly-fed wind farm under a slow time scale includes: performing stability judgment on the dynamic characteristic equation of the grid-connected doubly-fed wind farm by using the Routh-Hurwitz criterion to obtain a parameter setting method suitable for the grid-connected doubly-fed wind farm under a slow time scale.

6. The method according to claim 5, characterized in that The method of determining the stability of the dynamic characteristic equation of the grid-connected double-fed wind farm by using the Routh-Hurwitz criterion to obtain a parameter setting method suitable for the grid-connected double-fed wind farm under a slow time scale includes: According to the Routh-Hurwitz criterion, the stability condition of the dynamic characteristic equation of the grid-connected doubly-fed wind farm is obtained; Simplifying the coefficients in the dynamic characteristic equation of the grid-connected double-fed wind farm into an algebraic expression about the line equivalent impedance; According to the algebraic expression and the stability condition, a slow stability criterion between the grid-connected double-fed wind turbine generator set and the line equivalent reactance under the DC voltage control time scale is obtained; The parameters of the full-order linearized state space model are set to meet the slow stability criterion, so that the grid-connected double-fed wind farm can operate stably at a slow time scale.

7. A parameter setting device for a grid-connected double-fed wind farm, characterized in that: include: A model building module is used to establish a full-order linearized state space model based on the interaction behavior between N wind turbines and the power grid in a grid-connected double-fed wind farm, where N is a positive integer; An equivalent order reduction module is used to perform equivalent order reduction processing based on the full-order linearized state space model to obtain N independent equivalent subsystem models of single grid-connected double-fed wind turbines; A dynamic characteristic equation construction module, used to construct a dynamic characteristic equation of a grid-connected double-fed wind farm under a DC voltage control time scale according to the N mutually independent single grid-connected double-fed wind turbine equivalent subsystem models; The parameter setting module is used to judge the stability of the dynamic characteristic equation of the grid-connected double-fed wind farm and obtain a parameter setting method suitable for the grid-connected double-fed wind farm under a slow time scale.

8. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the method according to any one of claims 1 to 6 is implemented.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

10. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

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