Double-fed fan impedance modeling method and system based on VM-DPC and medium

Abstract

The invention relates to the technical field of wind power, and particularly provides a VM-DPC-based double-fed fan impedance modeling method and system and a medium, and the method comprises the steps: constructing a VM-DPC-based double-fed fan system based on an induction generator, RSC and GSC; combining the mechanical change information and the electromagnetic change information to construct a small-signal model of the rotating speed of the rotor; establishing an RSC partial impedance model based on rotor voltage control instruction value disturbance in combination with a small signal model of stator power and a small signal model of stator and rotor voltage; establishing a GSC partial impedance model based on the combination of GSC voltage control instruction value disturbance and the small signal model of GSC output power and the small signal model of DC voltage; and integrating the rotor rotating speed small signal model, the RSC partial impedance model and the GSC partial impedance model to construct a VM-DPC-based double-fed fan impedance model under small disturbance. The stability and efficiency of the doubly-fed fan are analyzed, and the reliability of wind power integration is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind power, and in particular relates to a VM-DPC-based doubly-fed wind turbine impedance modeling method, system and medium. Background Art

[0002] Doubly-fed wind turbine is a common wind power generation equipment. By analyzing the impedance characteristics of doubly-fed wind turbine, the grid-connected stability of wind power can be effectively evaluated. Since the dynamic characteristics of doubly-fed wind turbine are mainly dominated by its control strategy, different control strategies will significantly affect its impedance characteristics. Commonly used control strategies include voltage-oriented vector control and direct power control.

[0003] Existing impedance modeling and stability analysis technologies for doubly-fed wind turbines mainly focus on voltage-oriented vector control; there are only a few studies on impedance analysis of direct power control, mainly targeting the scenario where direct power control is applied to converters.

[0004] Therefore, there is currently a lack of a detailed impedance model for doubly-fed wind turbines based on direct power control, making it impossible to evaluate and analyze the impedance characteristics and anti-small disturbance performance of direct power control. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a VM-DPC-based doubly-fed wind turbine impedance modeling method, system and medium to solve the above-mentioned technical problems.

[0006] In a first aspect, the present invention provides a doubly-fed wind turbine impedance modeling method based on VM-DPC, comprising: A doubly-fed wind turbine system using VM-DPC is constructed based on an induction generator, RSC and GSC, and the electrical parameters, operating state variables and mechanical parameters of the generator are obtained based on the doubly-fed wind turbine system; exist αβ In the coordinate system, an aerodynamic model is constructed based on the mechanical parameters and operating state variables of the generator to obtain the mechanical change information of the mechanical torque under small disturbances. The electromagnetic change information of the electromagnetic torque under small disturbances is obtained based on the electrical parameters and operating state variables of the generator. The small signal model of the rotor speed is constructed by combining the mechanical change information and the electromagnetic change information. exist αβ In the coordinate system, the dynamic relationship between the generator stator power and the stator voltage and current is obtained based on the electrical parameters and operating state variables of the generator, the stator power is linearized to obtain the small signal model of the stator power, and the small signal model of the stator-rotor voltage is constructed based on the small signal model of the rotor speed combined with the stator voltage and the rotor voltage; the RSC partial impedance model is established based on the rotor voltage control command value disturbance combined with the small signal model of the stator power and the small signal model of the stator-rotor voltage; exist αβIn the coordinate system, the dynamic relationship between the GSC output power and the stator voltage and GSC current is obtained based on the electrical parameters and operating state variables. The small signal model of the GSC output power is obtained through linearization. The DC voltage equation is constructed based on the AC voltage and current of the RSC and GSC, and the small signal model of the DC voltage is obtained through linearization. The GSC partial impedance model is established based on the GSC voltage control command value disturbance combined with the small signal model of the GSC output power and the small signal model of the DC voltage. The rotor speed small signal model, RSC partial impedance model and GSC partial impedance model are integrated to construct the VM-DPC-based doubly fed wind turbine impedance model under small disturbance.

[0007] In an optional implementation, the doubly-fed wind turbine system based on VM-DPC includes a mechanical subsystem and an electrical subsystem, and the impedance model of the doubly-fed wind turbine based on VM-DPC is specifically:

[0008]

[0009] in, Small disturbances in stator voltage Small disturbance of grid-connected current Conjugate of small perturbations in stator voltage Conjugate of small disturbance of current at the grid connection point i = oh s t + f s ,in f s is the initial phase angle of the fundamental frequency voltage, is the impedance of the doubly-fed wind turbine based on VM-DPC, , , , , is the sub-impedance generated in the derivation process of the doubly-fed wind turbine impedance, expressed as:

[0010]

[0011]

[0012]

[0013]

[0014] in, is the impedance of RSC related to the stator voltage, is the impedance of the RSC related to the rotor speed, is the impedance related to the rotor voltage and rotor current, is the impedance related to the rotor voltage and rotor speed, is the portion of the mechanical subsystem impedance, is the impedance relating the stator voltage to the rotor current, is the impedance of RSC related to the stator current, is the other part of the mechanical subsystem impedance, is the impedance relating the rotor voltage to the stator current, is the impedance related to the stator voltage and stator current, is the impedance of GSC related to the stator voltage, is the impedance of GSC related to the GSC current, is the impedance of GSC related to DC voltage, is the impedance on the DC side related to the GSC voltage, is the impedance on the DC side related to the GSC current, is the impedance on the DC side related to the rotor voltage, is the impedance on the DC side related to the rotor current, is a two-dimensional unit diagonal matrix, is the impedance associated with the grid.

[0015] In an optional implementation, the small signal model of the rotor speed specifically includes: Construct an aerodynamic model as follows:

[0016] in, is the mechanical torque, r is the air density, r is the blade length, is the average wind speed, is the torque coefficient, l = r / represents the tip speed ratio, where is the mechanical angular velocity; Under the assumption of constant wind speed, a small disturbance analysis is performed on the aerodynamic model, and the linear relationship between the small disturbance of mechanical torque and the small disturbance of mechanical angular velocity is obtained; The electromagnetic torque is calculated based on the stator current and the rotor current, and the correlation formula between the electromagnetic torque and the stator current and the rotor current is obtained. The correlation formula is linearized to obtain the electromagnetic change information of the electromagnetic torque under small disturbance; Establish the motion equations of the two mass blocks of the transmission system to describe the dynamic coupling relationship between the mechanical and electromagnetic parts, and perform small signal linearization on the motion equations; The small signal model of the rotor speed is obtained by combining the linear relationship between the small disturbance of mechanical torque and the small disturbance of mechanical angular velocity, the electromagnetic change information of electromagnetic torque under small disturbance and the motion equation after small signal linearization processing, which is:

[0017] in, is a small disturbance in the rotor speed, is a small disturbance in the stator current, is the conjugate of a small perturbation of the stator current, is a small perturbation of the rotor current, is the conjugate of a small perturbation in the rotor current.

[0018] In an optional implementation, before establishing the RSC partial impedance model, an RSC control impedance model is established based on the rotor voltage control command value disturbance combined with a small signal model of the stator power, specifically including: The active circuit and reactive circuit of RSC control are linearized to obtain the rotor voltage control command value disturbance. α Axis components and β Expressions for the axis components, based on α Axis components and β The expression of the axis component represents the rotor voltage control command value disturbance in the form of a complex vector; Based on the double-fed wind turbine system, the electrical parameters and operating state variables are obtained αβ The stator active power and reactive power in the coordinate system, and the active power and reactive power are linearized to obtain the small signal model of the stator power; The RSC control impedance model in the two-dimensional complex vector space is established based on the rotor voltage control command value disturbance expressed in complex vector form and the small signal model of stator power, as follows:

[0019] in, is a small perturbation in the rotor voltage, is the conjugate of a small perturbation in the rotor voltage, is a small disturbance in the stator voltage, is the conjugate of a small perturbation in the stator voltage, is a small disturbance in the stator current, is the conjugate of a small perturbation of the stator current, is a small disturbance in the rotor speed.

[0020] In an optional implementation, obtaining an RSC partial impedance model between the stator voltage and the stator current based on the RSC control impedance model specifically includes: Based on the main circuit of the induction generator, the stator voltage equation and the rotor voltage equation are obtained, and the small signal model of the stator and rotor voltages is constructed after the stator voltage equation and the rotor voltage equation are linearized; Substitute the small signal model of the rotor speed into the RSC control impedance model, and eliminate the rotor voltage and current disturbance based on the small signal model of the stator and rotor voltage to obtain the RSC partial impedance model between the stator voltage and the stator current: .

[0021] In an optional implementation, before establishing the GSC partial impedance model, a GSC control impedance model based on the GSC voltage control command value disturbance combined with a small signal model of the GSC output power specifically includes: The active circuit and reactive circuit of GSC control are linearized respectively to obtain the disturbance of GSC voltage control command value. α Axis components and β Expressions for the axis components, based on α Axis components and β The expression of the axis component represents the GSC voltage control command value disturbance in the form of a complex vector; Based on the double-fed wind turbine system, the electrical parameters and operating state variables are obtained αβ The GSC outputs active power and reactive power in the coordinate system, and the active power and reactive power are linearized to obtain the small signal model of the GSC output power; The GSC control impedance model in two-dimensional complex vector space is established based on the GSC voltage control command value disturbance expressed in complex vector form and the small signal model of GSC output power, as follows:

[0022] in, is a small perturbation of the GSC voltage, is the conjugate of a small perturbation of the GSC voltage, is a small disturbance in the stator voltage, is the conjugate of a small perturbation in the stator voltage, is a small perturbation of the GSC current, is the conjugate of a small perturbation of the GSC current, is a small disturbance in the DC bus voltage.

[0023] In an optional implementation, the DC bus connects the GSC and the RSC, and before establishing the GSC partial impedance model, it also includes obtaining a frequency domain model of the DC voltage disturbance, specifically including: According to the equal instantaneous power of the AC side and the DC side of the converter, the DC bus voltage equation is obtained based on the AC voltage and current of the GSC and RSC; The DC bus voltage equation is linearized at the steady-state operation trajectory to obtain αβ The frequency domain model of DC voltage disturbance represented by complex vector in coordinate system includes: ; The interactive influence between the DC side and the AC side is obtained based on the frequency domain model of DC voltage disturbance, and the GSC partial impedance model is constructed based on the GSC controlled impedance model combined with the frequency domain model of DC voltage disturbance.

[0024] In an optional implementation, based on the GSC controlled impedance model combined with the frequency domain model of the DC voltage disturbance, a GSC partial impedance model between the stator voltage and the stator current and the GSC current is obtained, specifically including: Based on the filter circuit, the relationship equation between the GSC voltage, the GSC current and the stator voltage is obtained, and the relationship equation is linearized to obtain the transmission relationship between the GSC voltage disturbance and the stator voltage disturbance in the two-dimensional complex vector space; Substituting the frequency domain model of the transfer relationship and DC voltage disturbance into the GSC control impedance model, the GSC partial impedance model between the stator voltage, stator current and GSC current is obtained: .

[0025] In a second aspect, the present invention provides a doubly-fed wind turbine impedance modeling system based on VM-DPC. When the system is implemented, the doubly-fed wind turbine impedance modeling method based on VM-DPC is executed. The system includes: System building module, building a doubly-fed wind turbine system using VM-DPC based on induction generator, RSC and GSC, and obtaining the electrical parameters, operating state variables and mechanical parameters of the generator based on the doubly-fed wind turbine system; The small signal model building module of the rotor speed is αβ In the coordinate system, an aerodynamic model is constructed based on the mechanical parameters and operating state variables of the generator to obtain the mechanical change information of the mechanical torque under small disturbances. The electromagnetic change information of the electromagnetic torque under small disturbances is obtained based on the electrical parameters and operating state variables of the generator. The small signal model of the rotor speed is constructed by combining the mechanical change information and the electromagnetic change information. RSC partial impedance model building module, in αβIn the coordinate system, the dynamic relationship between the generator stator power and the stator voltage and current is obtained based on the electrical parameters and operating state variables of the generator, the stator power is linearized to obtain the small signal model of the stator power, and the small signal model of the stator-rotor voltage is constructed based on the small signal model of the rotor speed combined with the stator voltage and the rotor voltage; the RSC partial impedance model is established based on the rotor voltage control command value disturbance combined with the small signal model of the stator power and the small signal model of the stator-rotor voltage; GSC partial impedance model building module, in αβ In the coordinate system, the dynamic relationship between the GSC output power and the stator voltage and GSC current is obtained based on the electrical parameters and operating state variables. The small signal model of the GSC output power is obtained through linearization. The DC voltage equation is constructed based on the AC voltage and current of the RSC and GSC, and the small signal model of the DC voltage is obtained through linearization. The GSC partial impedance model is established based on the GSC voltage control command value disturbance combined with the small signal model of the GSC output power and the small signal model of the DC voltage. The doubly-fed wind turbine impedance model construction module integrates the rotor speed small signal model, RSC partial impedance model and GSC partial impedance model to construct a VM-DPC-based doubly-fed wind turbine impedance model under small disturbances.

[0026] According to a third aspect, a computer-readable storage medium is provided, wherein instructions are stored in the computer-readable storage medium, and when the computer-readable storage medium is run on a computer, the computer executes the methods described in the above aspects.

[0027] The beneficial effect of the present invention lies in that the doubly-fed wind turbine impedance modeling method, system and medium based on VM-DPC provided by the present invention start from constructing a doubly-fed wind turbine system using VM-DPC and obtaining relevant parameters, to respectively establishing a rotor speed small signal model, RSC and GSC partial impedance models, and finally comprehensively constructing a doubly-fed wind turbine impedance model based on VM-DPC, which can accurately describe the dynamic characteristics of the doubly-fed wind turbine under small disturbances, so that we have a deeper understanding of its complex internal electrical and mechanical interactions, thereby providing a solid theoretical basis for optimizing the wind turbine control strategy, helping to improve the operating stability and efficiency of the doubly-fed wind turbine, and enhancing the reliability of wind power grid connection.

[0028] In addition, the invention has a reliable design principle, a simple structure and a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the description will be briefly introduced below. 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 paying creative work.

[0030] Figure 1 It is a schematic flow chart of a doubly-fed wind turbine impedance modeling method based on VM-DPC according to an embodiment of the present invention.

[0031] Figure 2 It is a structural diagram of a doubly-fed wind turbine based on VM-DPC according to an embodiment of the present invention.

[0032] Figure 3 The present invention is an embodiment of the invention and the transmission relationship of small disturbances inside a doubly-fed wind turbine based on VM-DPC.

[0033] Figure 4 This is a comparison result of four impedance models according to an embodiment of the present invention.

[0034] FIG. 5( a ) is a diagram of VM-DPC control parameters according to an embodiment of the present invention. k p,rsc Eigenvalue trace as it decreases from 378 to 31.5.

[0035] FIG. 5( b ) is a diagram of VM-DPC control parameters according to an embodiment of the present invention. k p,gsc Eigenvalue trajectory when decreasing from 3720 to 310.

[0036] FIG. 5( c ) is a diagram of VM-DPC control parameters according to an embodiment of the present invention. k i,rsc The trajectory of the eigenvalues ​​when increasing from 2900 to 50000.

[0037] FIG. 5( d ) is a diagram showing VM-DPC control parameters according to an embodiment of the present invention. k i,gsc The eigenvalue trajectory when increasing from 9800 to 117600.

[0038] Figure 6 It is the comparison result of theoretical derivation and frequency sweep measurement of the comprehensive impedance of the doubly-fed wind turbine according to one embodiment of the present invention.

[0039] FIG. 7( a ) is a modified example of an embodiment of the present invention. k p,rsc The waveform diagram of the simulation results.

[0040] FIG. 7( b ) is a modified example of an embodiment of the present invention. k p,rsc FFT of the simulation results.

[0041] FIG8(a) is a modified example of an embodiment of the present invention. k i,rsc The waveform diagram of the simulation results.

[0042] FIG8(b) is a modified example of an embodiment of the present invention. k i,rsc FFT of the simulation results.

[0043] Figure 9 It is a schematic block diagram of a doubly-fed wind turbine impedance modeling system based on VM-DPC according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0046] The key terms appearing in the present invention are explained below.

[0047] Linearization is a mathematical method commonly used in analyzing complex systems. , at a certain working point Nearby, it is approximately expressed as a linear function. Usually, Taylor series expansion is used, and high-order infinitesimal terms are ignored to obtain the linearized expression ,in yes exist The derivative at .

[0048] The doubly-fed wind turbine impedance modeling method based on VM-DPC provided in the embodiment of the present invention is executed by a computer device, and accordingly, the doubly-fed wind turbine impedance modeling system based on VM-DPC runs in the computer device.

[0049] Figure 1 FIG. 1 is a schematic flow chart of a method for modeling impedance of a doubly-fed wind turbine based on VM-DPC according to an embodiment of the present invention. Figure 1 The execution subject may be a double-fed wind turbine impedance modeling system based on VM-DPC. According to different requirements, the order of the steps in the flow chart may be changed, and some may be omitted.

[0050] like Figure 1 As shown, the method includes: S1, construct a doubly-fed wind turbine system using VM-DPC based on induction generator, RSC and GSC, and obtain the electrical parameters, operating state variables and mechanical parameters of the generator based on the doubly-fed wind turbine system; During the system construction process, the connection methods of various components are reasonably configured to ensure smooth interaction of power transmission and control signals. Then, various sensors such as voltage sensors, current sensors, speed sensors, torque sensors, etc. are installed on the generator to monitor and obtain the generator's electrical parameters (such as stator voltage, rotor voltage, stator current, rotor current, etc.), operating state variables (such as speed, power factor, power, etc.) and mechanical parameters (such as torque, shaft moment of inertia, etc.) in real time.

[0051] Accurately acquired electrical parameters, operating state variables and mechanical parameters can fully understand the initial state of the doubly fed wind turbine system, provide necessary data support for the subsequent construction of various models and system performance analysis, and ensure that subsequent analysis and control decisions have actual physical basis.

[0052] S2, in αβ In the coordinate system, an aerodynamic model is constructed based on the mechanical parameters and operating state variables of the generator to obtain the mechanical change information of the mechanical torque under small disturbances. The electromagnetic change information of the electromagnetic torque under small disturbances is obtained based on the electrical parameters and operating state variables of the generator. The small signal model of the rotor speed is constructed by combining the mechanical change information and the electromagnetic change information. Using known mechanical parameters and operating state variables, an aerodynamic model is established based on aerodynamic principles. The model can be a functional relationship between wind speed, wind wheel radius, pitch angle, etc. and mechanical torque. Through experiments or simulations, small disturbances are applied to the system, and the changes in mechanical torque are observed and calculated, so as to obtain information on the changes in mechanical torque under small disturbances. For electromagnetic torque, electrical parameters and operating state variables are used to calculate the relationship between electromagnetic torque and stator current and rotor current according to the electromagnetic principles of the motor, and information on the changes in electromagnetic torque under small disturbances is obtained. Combining these two parts of information, using the small signal analysis method, the rotor speed is regarded as consisting of a steady-state value and a small disturbance component, and is substituted into the relevant mechanical and electromagnetic torque equations. After linearization and derivation of system equations, a small signal model of the rotor speed is finally constructed.

[0053] The constructed rotor speed small signal model can accurately reflect the combined influence of mechanical and electromagnetic factors on the speed, and provides an important model basis for the subsequent analysis of the stability and control performance of the fan under dynamic conditions.

[0054] S3, in αβIn the coordinate system, the dynamic relationship between the generator stator power and the stator voltage and current is obtained based on the electrical parameters and operating state variables of the generator, the stator power is linearized to obtain the small signal model of the stator power, and the small signal model of the stator-rotor voltage is constructed based on the small signal model of the rotor speed combined with the stator voltage and the rotor voltage; the RSC partial impedance model is established based on the rotor voltage control command value disturbance combined with the small signal model of the stator power and the small signal model of the stator-rotor voltage; Starting from the electrical parameters and operating state variables of the generator, the dynamic relationship expression between the stator power and the stator voltage and current is derived according to the basic equations of the motor (such as the power equation). The linearization method is used for the stator power. Usually, the Taylor series expansion can be used and the high-order terms can be ignored to express the stator power as a combination of steady-state values ​​and small signal components, thereby obtaining the small signal model of the stator power. According to the small signal model of the rotor speed, combined with the physical relationship and equations of the stator voltage and the rotor voltage, the stator-rotor voltage equation is linearized using circuit theory and motor equations to obtain the small signal model of the stator-rotor voltage. Finally, based on the rotor voltage control command value disturbance combined with the small signal model of the stator power and the small signal model of the stator-rotor voltage, the RSC partial impedance model is established, which can be expressed as a complex impedance using methods such as complex frequency domain analysis.

[0055] The RSC partial impedance model can analyze the impact of RSC on stator power and stator-rotor voltage, thereby evaluating the effectiveness of the RSC control strategy and the stability of the system under different operating conditions.

[0056] S4, in αβ In the coordinate system, the dynamic relationship between the GSC output power and the stator voltage and GSC current is obtained based on the electrical parameters and operating state variables. The small signal model of the GSC output power is obtained through linearization. The DC voltage equation is constructed based on the AC voltage and current of the RSC and GSC, and the small signal model of the DC voltage is obtained through linearization. The GSC partial impedance model is established based on the GSC voltage control command value disturbance combined with the small signal model of the GSC output power and the small signal model of the DC voltage. According to the electrical parameters and operating state variables, based on the power conversion and control principle of the converter, the dynamic relationship between the GSC output power and the stator voltage and GSC current is derived, and a method similar to the stator power linearization is used to linearize and obtain its small signal model. The expression of the GSC voltage control command value disturbance is found through theoretical analysis and mathematical derivation on the GSC control loop. According to the principle that the instantaneous power on the AC side and the DC side of the converter is equal, the DC voltage is represented by the AC voltage and current of the GSC and RSC, and the small signal model of the DC voltage is obtained by linearization. The small signal model of the GSC output power and the small signal model of the DC voltage are combined with the expression of the GSC voltage control command value disturbance, and the control and circuit characteristics of the converter are considered. The GSC partial impedance model is established using control theory and circuit analysis methods. The model can be obtained by linearizing and transforming the relationship between power, voltage and current in the frequency domain.

[0057] The GSC partial impedance model provides an important tool for studying the role of GSC in the system. It can be used to evaluate the impact of GSC control strategy on system stability, especially the performance evaluation of DC voltage control and grid-side power control. It helps to optimize the control parameters of GSC and ensure the stability of DC bus voltage and stable transmission of grid-side power.

[0058] S5, the impedance model of the doubly fed wind turbine based on VM-DPC under small disturbance is constructed by integrating the rotor speed small signal model, RSC partial impedance model and GSC partial impedance model.

[0059] The key variables and equations in each model are coupled according to the physical connection and energy transfer relationship of the system. Through appropriate matrix operations, frequency domain transformation and solution of system equations, an overall VM-DPC-based doubly fed wind turbine impedance model is established under the assumption of small disturbance.

[0060] The constructed impedance model of the doubly-fed wind turbine can comprehensively and systematically describe the electrical characteristics of the doubly-fed wind turbine under small disturbances, and provides a unified theoretical model for system analysis, fault diagnosis, stability assessment and control strategy optimization of the doubly-fed wind turbine. It helps to study the stability boundary of the wind power system under different operating conditions, and provides key theoretical support for improving the grid-connected performance of the wind power system, reducing harmonic interference, improving the anti-interference ability of the system and optimizing the overall performance, which promotes the efficient and stable operation of the doubly-fed wind turbine system in practical applications and the efficient use of wind power energy.

[0061] Optionally, as an embodiment of the present invention, the detailed topology of a doubly-fed induction generator (DFIG) based on voltage-modulated direct power control (VM-DPC) is as follows: Figure 2 As shown. u s and u r are the stator and rotor voltages, i s and i r are the stator and rotor currents, u g and i g are the GSC voltage and current, i t is the total current at the DFIG point of common coupling (PCC), u dc is the DC bus voltage. The variables in bold in this application represent αβ A complex vector in a coordinate system, for example, u s = u sα +j u sβ .

[0062] By applying VM-DPC, the rotor-side converter (RSC) is responsible for regulating the stator power, while the grid-side converter (GSC) controls the DC voltage.

[0063] VM-DPC in stator αβ In the coordinate system, the converter output power is directly decoupled and controlled based on the predefined voltage modulation variable, thereby generating the converter voltage command value. For RSC control, since its control object is the stator power, it is necessary to derive the dynamic relationship between the stator power and the RSC output rotor voltage to construct the control equation of the RSC VM-DPC.

[0064] Optionally, as an embodiment of the present invention, the stator active P s and reactive Q s exist αβ The coordinate system can be written as:

[0065] (1) In order to eliminate the stator current in the stator power, αβ The stator and rotor voltage equations of the DFIG main circuit are established in the coordinate system and are expressed as follows: (2) in oh m is the rotor speed, R s and R r are the stator and rotor resistances respectively. ψ s and rotor flux ψ r It can be calculated by the stator and rotor current as follows: (3) in L s and L r are the stator and rotor inductances, respectively, L m is the magnetizing inductance.

[0066] Therefore, by differentiating the stator power (1) and substituting (2) and (3) into it, the control equation of the VM-DPC of the RSC can be finally obtained: (4) in s αβ =1- L s L r / L m L m is the leakage inductance coefficient of VM-DPC, oh s Indicates the fundamental angular frequency of the power grid. Rotor voltage and current angular frequency oh r and oh m The relationship is oh r = oh s - oh m .

[0067] In the above formula u rP and u rQThey are defined as the active control and reactive control voltage modulation variables of VM-DPC on the RSC side, which have a nonlinear relationship with the stator and rotor voltages. By defining the voltage modulation variable, an approximate linear relationship between it and the stator output power can be established, which is expressed as: (5) in k s =-2 s αβ L m / 3 is the VM-DPC gain of RSC. In a large-capacity doubly fed wind turbine system, R r Usually relatively small, it has little effect on control performance. Therefore, the compensation term representing the coupling of stator voltage and rotor current is C rP and C rQ Can be ignored.

[0068] Therefore, for a given stator power reference value, the decoupling term can be set k s oh r Q s and k s oh r P s , and then use PI modulation to control active and reactive power to generate u rP and u rQ Finally, according to the definition of voltage modulation variables in (4), the voltage modulation transformation equation (6) is inferred and the calculation is obtained. αβ The rotor voltage command value in the coordinate system. The control principle of VM-DPC on the RSC side is implemented as follows: Figure 1 As shown in the blue box on the left.

[0069] (6).

[0070] Optionally, as an embodiment of the present invention, the outer control loop of the GSC uses PI modulation to maintain a constant DC bus voltage, while the inner control loop uses VM-DPC to control the output power of the converter according to the power reference value generated by the DC voltage outer loop. Therefore, the control equation of the VM-DPC of the GSC is the dynamic relationship between the output power and the GSC voltage.

[0071] αβ GSC output active power in coordinate system Pg and reactive Q g It can be expressed as: (7) At the same time, according to the GSC filter circuit, the relationship between the GSC voltage, the GSC current and the stator voltage can be obtained as follows: (8) in, R g and L g are the resistance and inductance of the GSC filter.

[0072] Referring to the derivation process of the control equation on the RSC side, differentiate (7) and substitute it into (8) to eliminate the GSC current, and the control equation of the VM-DPC of the GSC can be obtained: (9).

[0073] Similarly, in (9) u gP and u gQ are the nonlinear active control and reactive control voltage modulation variables of VM-DPC on the GSC side, respectively. And the linear relationship between the GSC output power and the voltage modulation variable is: (10) in k g =2 L g / 3 is the VM-DPC gain of GSC.

[0074] Therefore, for the GSC output power reference value given by the DC voltage control outer loop, PI modulation can also be used to achieve active and reactive power control. Then, by setting the decoupling term k g oh s Q g and k g oh s P g generate u gP and u gQ Finally, according to the GSC side voltage modulation transformation equation (11), we can get αβ The GSC voltage command value in the coordinate system. The VM-DPC structure corresponding to the above GSC control principle is as follows: Figure 1As shown in the blue box on the right.

[0075] (11).

[0076] Optionally, as an embodiment of the present invention, different from dq The steady state of the system in the coordinate system is manifested as a constant operating point. αβ The steady state of the system in the coordinate system is a time-varying periodic trajectory. Therefore, αβ Impedance modeling in the coordinate system requires small signal linearization directly at the steady-state operating trajectory. Assume that any variable x = X +Δ x , where capital letters X represents the steady-state value, Δ x represents a small signal disturbance. At the same time, the three-phase disturbance is represented in the 2D complex vector space as [Δ x , e j2θ Δ x * ], and the single-phase disturbance is expressed as [ e jθ Δ x , 0]. The superscript “*” indicates conjugation. i = oh s t + f s ,in f s is the initial phase angle of the fundamental frequency PCC voltage.

[0077] Considering that the DFIG impedance with steady-state operation trajectory is not easy to calculate, the derivation process will use dq The following complex vector and complex transfer function are used to replace the steady-state operating point in the coordinate system. αβ Coordinate system and dq The conversion relationship between coordinate systems: (12) (13) The left side of the arrow is the time domain conversion relationship, and the right side is the frequency domain conversion relationship.

[0078] Optionally, as an embodiment of the present invention, in step S2, there is a dynamic coupling between the mechanical subsystem and the electrical subsystem of the DFIG, and the coupling is mainly achieved through the rotor speed. oh m Therefore, this section mainly considers the mechanical dynamics establishment oh m Small signal model.

[0079] The aerodynamic model calculates the mechanical torque based on the wind power captured by the impeller T tur : (14) in, r is the air density, r is the blade length, V w is the average wind speed, C T ( l , t ) is the torque coefficient. l = Oh tur r / V w represents the tip speed ratio, where Oh tur is the mechanical angular velocity. In particular, when fixed pitch control is used, the pitch angle t is a constant. Therefore, C T and l The relationship between can be fitted by the least squares method as follows: (15) When analyzing the small signal characteristics of a doubly fed wind turbine, it is assumed that the wind speed is constant. Therefore, by linearizing equation (14) with small disturbances, we can obtain Δ T tur With Δ Oh tur Relationship: (16) Electromagnetic torque related to stator and rotor currents T e It can be calculated as: (17) in p is the number of motor pole pairs. Therefore, by linearizing (17) on the steady-state periodic trajectory, the variation information of the electromagnetic torque under small disturbance can be obtained as follows: (18) The mechanical torque and electromagnetic torque are related through the transmission system of DFIG. Considering the balance between stability analysis requirements and model complexity, a two-mass model is adopted. Assuming that all amplitude changes are on the high-speed axis, the motion equation can be written as: (19) in, N is the gearbox speed ratio, Jt and J m is the dual-mass mechanical inertia, D t and D m is the friction coefficient. K tm and the damping coefficient D tm The flexible coupling between the two masses is defined. The generator angular velocity Oh m and oh m The relationship is: Oh m = oh m / p Then, (19) is subjected to small signal linearization and Laplace transform: (20) Therefore, by substituting (16) and (18) into (20), the small signal model of the rotor speed can be derived and written in matrix form as: (twenty one) (twenty two) in, is a small perturbation in the rotor angular velocity, is a small disturbance in the stator current, is the conjugate of a small perturbation of the stator current, is a small perturbation of the rotor current, is the conjugate of a small perturbation of the rotor current, H m Yes oh m With Δ Oh tur The transfer function between: (twenty three).

[0080] Optionally, as an embodiment of the present invention, in step S3, the stator-rotor voltage equation (2) of the generator main circuit is linearized by considering the small signal characteristics of the rotor speed. Thus, a small signal frequency domain model of the stator-rotor voltage equation is constructed in a two-dimensional complex vector space: (twenty four) (25) (26) (27) According to the VM-DPC control principle of RSC, the stator power decoupling term includes oh r .now that oh r = oh s - oh m , then in oh s When constant, there is Δ oh r =-Δ oh m Therefore, the impedance modeling of RSC control also needs to consider the small signal characteristics of the rotor speed. The active circuit and reactive circuit of RSC control are linearized to obtain the rotor voltage command value disturbance. α Axis components and β Axis components and combined into complex vector form: (28) in G rsc (s)= k p,rsc + k i,rsc / s is the PI transfer function of VM-DPC on the RSC side. The small signal model of stator power can be obtained by linearizing (1) at the steady-state time-varying trajectory: (29) Further, take the conjugate of (28) and multiply both sides of the equality by e j2θ At the same time, combined with (28), the RSC controlled impedance model is established in the two-dimensional complex vector space: (30) (31) Optionally, as an embodiment of the present invention, by substituting (21) into (30), and eliminating the rotor voltage and current disturbance according to (24) and (26), the RSC partial impedance model between the stator voltage and the stator current can be obtained: (32) (33) Optionally, as an embodiment of the present invention, according to Figure 1 The VM-DPC structure of the GSC shown in the figure derives the GSC voltage command value disturbance. α Axis components and β The GSC voltage command value disturbance is then written in complex vector form: (34) in G gsc (s)= k p,gsc + k i,gsc / s is the PI transfer function of VM-DPC on the GSC side. G u (s)= k p,u + k i,u / s is the PI transfer function of the DC voltage control on the GSC side. The small signal model of the GSC output power can be obtained by linearizing (7): (35) Similarly, take the conjugate of (34) and multiply both sides of the equality by e j2θ Then, by combining (34), the GSC controlled impedance model in the two-dimensional complex vector space can be established: (36) (37) From (36), it can be seen that the GSC control impedance model includes DC voltage disturbance. This is because the control outer loop of the GSC needs to measure the DC voltage to control it to a given value, which causes the DC voltage disturbance to enter the GSC control. The DC bus connects the GSC and RSC. According to the equal instantaneous power on the AC and DC sides of the converter, the DC bus voltage equation can be expressed by the AC voltage and current of the GSC and RSC as follows: (38) in C dc is the DC bus capacitance. By linearizing the above equation at the steady-state operation trajectory, the αβ The frequency domain model of DC voltage disturbance represented by complex vector in coordinate system: (39) (40) Further linearizing (8) yields the transfer relationship between the GSC voltage disturbance and the stator voltage disturbance in the two-dimensional complex vector space: (41) (42) Therefore, substitute (39) and (41) into (36). Combining (24) and (26), the GSC partial impedance relationship between the stator voltage and the stator current and the GSC current can be obtained: (43) (44) in E is a two-dimensional unit diagonal matrix. It should be noted that the substitution into (24) and (26) in the derivation process is to eliminate the rotor voltage and current disturbances introduced by the DC voltage disturbance. However, this substitution will introduce rotor speed disturbances. Therefore, the rotor speed dynamics will indirectly affect the impedance characteristics of the GSC part through the DC voltage.

[0081] Optionally, as an embodiment of the present invention, step S5 specifically includes: referring to Figure 3 , the transmission relationship of the small disturbance inside the DFIG is established. The transmission signal in the figure is actually a small signal disturbance in the two-dimensional complex vector space. However, for the simplicity of the figure, only one-dimensional complex vector disturbance is marked as a schematic. The figure reveals the dynamic coupling characteristics between the mechanical subsystem, motor, RSC and GSC, and further explains that each part cannot be ignored when modeling impedance. Combining (32) and (43), and noting that Δ i t =Δ i s -Δ i g Finally, the DFIG based on VM-DPC is obtained. αβ Complex vector comprehensive impedance model in coordinate system: (45) in (46) in, Small disturbances in stator voltage Small disturbance of grid-connected current Conjugate of small perturbations in stator voltage Conjugate of small disturbance of current at the grid connection point i = oh s t + f s ,in f s is the initial phase angle of the fundamental frequency voltage, is the impedance of the doubly-fed wind turbine based on VM-DPC, , , , , is the sub-impedance generated in the derivation process of the impedance of the doubly-fed wind turbine. is the impedance of RSC related to the stator voltage, is the impedance of the RSC related to the rotor speed, is the impedance related to the rotor voltage and rotor current, is the impedance related to the rotor voltage and rotor speed, is the portion of the mechanical subsystem impedance, is the impedance relating the stator voltage to the rotor current, is the impedance of RSC related to the stator current, is the other part of the mechanical subsystem impedance, is the impedance relating the rotor voltage to the stator current, is the impedance related to the stator voltage and stator current, is the impedance of GSC related to the stator voltage, is the impedance of GSC related to the GSC current, is the impedance of GSC related to DC voltage, is the impedance on the DC side related to the GSC voltage, is the impedance on the DC side related to the GSC current, is the impedance on the DC side related to the rotor voltage, is the impedance on the DC side related to the rotor current, is a two-dimensional unit diagonal matrix, is the impedance associated with the grid.

[0082] Z DPC The non-main diagonal elements in are non-zero, which indicates that there is frequency coupling in DFIG. oh p In addition to the disturbance with a frequency of oh p In addition to the response, a frequency of 2 oh s - oh p Since the VM-DPC structure is symmetrical and has no PLL, the frequency coupling in the impedance of the VM-DPC-based DFIG is mainly caused by the single-phase mechanical subsystem and the asymmetric DC voltage control outer loop as well as the nonlinear power calculation and voltage modulation transformation. At the same time, since the VM-DPC does not need to be synchronized with the grid voltage through a phase-locked loop (PLL), there is no need to consider the control system caused by the PLL dynamics when modeling the impedance of the VM-DPC-based DFIG. dq Angular disturbance of the coordinate system. This is the main difference between the impedance modeling of DFIG based on VM-DPC and the impedance modeling of DFIG based on voltage-oriented vector control.

[0083] Optionally, as an embodiment of the present invention, the influence of various parts of DFIG on the impedance characteristics is analyzed, and the proposed comprehensive impedance is compared with various simplified DFIG impedances. When analyzing the DFIG impedance characteristics, the influence of the grid impedance is not considered for the time being. Assume Figure 1 The DFIG shown is directly connected to the ideal grid. The basic parameters of DFIG are shown in Table 1. Wind speed V w The total active power output of DFIG is 12m / s. P t Total reactive power Q t They are 1.5MW and 0Mvar respectively.

[0084] Table 1DFIG parameters

[0085] Simplified impedance 1 ignores mechanical dynamics and is expressed as Z DPC In Z ωm1 and Z ωm2 The simplified impedance 2 assumes that the DC bus voltage is constant and ignores the GSC dynamics, which is directly derived from (32). The simplified model 3 only considers the GSC dynamics, and the RSC and the motor are equivalent to a constant power source. Z dc,ir and Z dc,ur After being a zero matrix, it is derived according to (43).

[0086] Optionally, as a comparison result of the above four impedance models in one embodiment of the present invention, Figure 4 As shown in Figure 1, by comparing the proposed comprehensive impedance with the simplified impedance 1, it can be seen that mechanical dynamics will significantly affect the frequency characteristics of DFIG impedance near 50Hz, while the impact is small in other frequency ranges. This is mainly because the mechanical dynamic time scale of DFIG is slow, which will affect the low-frequency characteristics of the rotor speed disturbance. However, in αβ When deriving the DFIG complex vector impedance in the coordinate system, the single-phase rotor speed disturbance needs to be multiplied by e jθ , which is equivalent to a 50Hz frequency shift. Therefore, the mechanical dynamics αβThe influence of DFIG impedance in the coordinate system is ultimately reflected in the sub / supersynchronous frequency band. This conclusion shows that it is necessary to consider mechanical dynamics to obtain more accurate analysis results when studying sub / supersynchronous oscillations or low-frequency power oscillations of DFIG grid-connected. Further comparing the proposed impedance with simplified impedance 2, it can be found that whether the GSC dynamics are considered has little effect on the main diagonal elements of DFIG impedance, and the main difference is also located near 50Hz. However, ignoring the GSC dynamics will significantly affect the accuracy of the non-main diagonal elements of DFIG impedance, reducing its amplitude. This shows that GSC dynamics is one of the main factors causing frequency coupling in DFIG. This can also be proved by the phenomenon that the non-main diagonal elements of simplified impedance 3 have an amplitude far exceeding that of the non-main diagonal elements of simplified impedance 2. This conclusion shows that even if the DFIG impedance characteristics are mainly determined by RSC and motor, GSC dynamics cannot be ignored in the modeling process.

[0087] It is worth noting that the VM-DPC-based DFIG comprehensive impedance has irregular amplitude spikes and strong nonlinear phase angle changes near 50Hz. Combining the frequency characteristics of the four impedances in this frequency band, it can be seen that this phenomenon is the result of the dynamic interaction of various parts of the DFIG, and cannot be simply considered to be caused by only a single factor of mechanical dynamics or GSC dynamics. Therefore, in order to obtain more accurate impedance characteristics, especially in the sub / supersynchronous frequency band, it is necessary to consider the mechanical and GSC dynamics to establish a DFIG comprehensive impedance model based on VM-DPC.

[0088] Optionally, as an embodiment of the present invention, the influence of the control parameters of VM-DPC on the stability of the DFIG grid-connected system is analyzed based on the proposed comprehensive impedance considering the grid impedance. αβ The coordinate system impedance can be expressed as Z grid . Aggregation impedance Z = Z DPC + Z grid The zero point of the determinant is equivalent to the eigenvalue of the DFIG grid-connected system. Therefore, by calculating Z Are all the zeros of the determinant located in the left half? s The small disturbance stability of the DFIG grid-connected system can be evaluated on a plane. αβ The first coordinate system of the aggregate impedance k The real part of the determinant is the same at the zero point, and the imaginary part is about oh s Symmetrical, can be written as l 2k-1 = s k +j oh k and l 2k = s k +j(2 oh s- oh k ). Imaginary part oh k and 2 oh s- oh k It also means that the oscillation mode corresponding to the pair of zero points is αβ The oscillation frequency in the coordinate system reflects the frequency coupling.

[0089] The basic parameters of the DFIG using VM-DPC are still referred to Table 1. The value of the grid impedance is set to make the short-circuit ratio 2, corresponding to the weak grid situation. The wind speed is 12m / s, and the total active power and total reactive power of the DFIG are 1.5MW and 0Mvar respectively. k p,rsc , k p,gsc , k i,rsc and k i,gsc The value of is calculated based on the proposed DFIG comprehensive impedance. Then the variation of the system eigenvalue with the VM-DPC control parameters is analyzed. According to the distance of the eigenvalue from the imaginary axis, l 1,2 , l 3,4 , l 5 is the dominant eigenvalue of the system. Figures 5(a), 5(b), 5(c) and 5(d) respectively show the dominant eigenvalue trajectories when different VM-DPC control parameters change. It can be seen from Figures 5(b) and 5(d) that with the change of the PI parameters on the GSC side, the dominant eigenvalue of the system remains basically unchanged. This shows that the control parameters of the VM-DPC on the GSC side have little effect on the stability of the DFIG grid-connected system. Therefore, this application mainly analyzes the influence of the control parameters of the VM-DPC on the RSC side on the system stability.

[0090] according to Figure 5(a) and 5(c) It can be seen that with k p,rsc The decrease of eigenvalue l 1,2 It will gradually move to the right and eventually cross the imaginary axis to reach the right half plane. k p,rsc =31.5, there is l 1=2.92+j282.32, l2=2.92+j346. Eigenvalue l 3,4 Although the real part of k p,rsc decreases with the decrease of l 1,2 Much smaller, and always on the left half s plane. And the eigenvalue l 5 is basically unaffected. Therefore, near the stability boundary, as the RSC side k p,rsc As the value of increases, the system stability is gradually enhanced. For Figure 5(c), as k i,rsc The increase of eigenvalue l 5 also changes little, and the real part only decreases slightly. l 1,2 and l 3,4 will move to the right, and the real part will gradually increase. l 1,2 The change amplitude of is the largest and will eventually cross the imaginary axis and reach the right half plane. k i,rsc =48000, there is l 1=1.11+j216.85, l 2=1.11+j411.47. Therefore, near the stability boundary, the RSC side k i,rsc The increase of will weaken the system stability until it becomes unstable.

[0091] Optionally, as an embodiment of the present invention, the correctness of the comprehensive impedance of the proposed VM-DPC-based DFIG is verified by a frequency scanning method. At the same time, the influence of VM-DPC parameters on the grid-connected stability of DFIG is verified by simulation. These simulation verifications are all based on the DFIG simulation model built in MATLAB / Simulink. The basic parameters of DFIG refer to Table 1. The wind speed is 12m / s, and the total active power and total reactive power output of DFIG are 1.5MW and 0Mvar respectively.

[0092] The simulation model of the DFIG based on VM-DPC is built based on MATLAB / Simulink. Z DPC Perform frequency sweep measurements. αβ The complex vector impedance in the coordinate system is oh p The value at needs to be obtained through two disturbance injections. The DFIG steady state corresponding to these two disturbance injections must be consistent, and the corresponding disturbance frequencies are ohp and oh p -2 oh s The form of disturbance is chosen αβ The amplitude of the disturbance is set to 0.01 pu, which is small enough to maintain system stability and large enough for impedance identification. αβ By measuring the voltage and current responses of the grid connection point during two disturbance injections in the coordinate system, the DFIG impedance value at the corresponding disturbance frequency can be calculated. The comparison between the frequency sweep measurement results and the theoretically derived DFIG comprehensive impedance is shown in Figure 2. Figure 6 The two have good consistency, which proves the correctness of the DFIG comprehensive impedance based on VM-DPC proposed in the present invention.

[0093] The analysis results of the influence of the above VM-DPC control parameters on the DFIG grid-connected stability are verified by simulation. The numerical setting of the grid impedance makes the short-circuit ratio 2, corresponding to the weak grid situation. The control parameters at the initial state of the simulation are set according to Table 1. According to Figures 5(a), 5(b), 5(c) and 5(d), it can be seen that the system maintains stable operation. First, verify k p,rsc impact. k p,rsc It decreases to 94.5 at the 11th second and continues to decrease to 31.5 at the 15th second. The simulation results are as follows Figure 7(a) and 7(b) Then change k i,rsc Rerun the simulation. k i,rsc It increases to 45000 at the 11th second and continues to increase to 48000 at the 15th second. The simulation results are as follows Figure 8(a) and 8(b) As shown in the results of these two simulations, k p,rsc reduction or k i,rsc As the value of increases, the system stability will gradually weaken and eventually become unstable. This is consistent with the dominant eigenvalue trajectory of the system shown in Figure 5(a), Figure 5(b), Figure 5(c) and Figure 5(d). In addition, through FFT analysis of the voltage, it can be seen that the oscillation frequencies of the two instabilities are consistent with the calculation results of the dominant eigenvalue. The simulation proves that too small k p,rsc and oversized k i,rsc It will indeed make the DFIG grid-connected system more prone to instability.

[0094] In some embodiments, the double-fed wind turbine impedance modeling system based on VM-DPC may include a plurality of functional modules composed of computer program segments. The computer program of each program segment in the double-fed wind turbine impedance modeling system based on VM-DPC may be stored in a memory of a computer device and executed by at least one processor to perform (see Figure 1 Description) Functions of impedance modeling of doubly-fed wind turbines based on VM-DPC.

[0095] In this embodiment, the VM-DPC-based doubly-fed wind turbine impedance modeling system can be divided into multiple functional modules according to the functions it performs, such as Figure 9 As shown. The functional modules of the system may include: a system construction module, a rotor speed small signal model construction module, an RSC partial impedance model construction module, a GSC partial impedance model construction module, and a doubly fed wind turbine impedance model construction module. The module referred to in the present invention refers to a series of computer program segments that can be executed by at least one processor and can perform fixed functions, which are stored in a memory. In this embodiment, the functions of each module will be described in detail in subsequent embodiments. The system includes: System building module, building a doubly-fed wind turbine system using VM-DPC based on induction generator, RSC and GSC, and obtaining the electrical parameters, operating state variables and mechanical parameters of the generator based on the doubly-fed wind turbine system; The small signal model building module of the rotor speed is αβ In the coordinate system, an aerodynamic model is constructed based on the mechanical parameters and operating state variables of the generator to obtain the mechanical change information of the mechanical torque under small disturbances. The electromagnetic change information of the electromagnetic torque under small disturbances is obtained based on the electrical parameters and operating state variables of the generator. The small signal model of the rotor speed is constructed by combining the mechanical change information and the electromagnetic change information. RSC partial impedance model building module, in αβ In the coordinate system, the dynamic relationship between the generator stator power and the stator voltage and current is obtained based on the electrical parameters and operating state variables of the generator, the stator power is linearized to obtain the small signal model of the stator power, and the small signal model of the stator-rotor voltage is constructed based on the small signal model of the rotor speed combined with the stator voltage and the rotor voltage; the RSC partial impedance model is established based on the rotor voltage control command value disturbance combined with the small signal model of the stator power and the small signal model of the stator-rotor voltage; GSC partial impedance model building module, in αβIn the coordinate system, the dynamic relationship between the GSC output power and the stator voltage and GSC current is obtained based on the electrical parameters and operating state variables. The small signal model of the GSC output power is obtained through linearization. The DC voltage equation is constructed based on the AC voltage and current of the RSC and GSC, and the small signal model of the DC voltage is obtained through linearization. The GSC partial impedance model is established based on the GSC voltage control command value disturbance combined with the small signal model of the GSC output power and the small signal model of the DC voltage. The doubly-fed wind turbine impedance model construction module integrates the rotor speed small signal model, RSC partial impedance model and GSC partial impedance model to construct a VM-DPC-based doubly-fed wind turbine impedance model under small disturbances.

[0096] Starting from building a doubly-fed wind turbine system using VM-DPC and obtaining relevant parameters, to establishing the rotor speed small signal model, RSC and GSC partial impedance models, and finally comprehensively building a doubly-fed wind turbine impedance model based on VM-DPC, it has brought many significant benefits to the research and application of doubly-fed wind turbines. It can accurately describe the dynamic characteristics of doubly-fed wind turbines under small disturbances, so that we have a deeper understanding of its complex internal electrical and mechanical interactions, thus providing a solid theoretical basis for optimizing wind turbine control strategies, helping to improve the operating stability and efficiency of doubly-fed wind turbines and enhance the reliability of wind power grid connection.

[0097] The present invention also provides a computer-readable storage medium, wherein the computer storage medium may store a program, and when the program is executed, the program may include some or all of the steps in each embodiment provided by the present invention. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM).

[0098] Therefore, the technical effects that can be achieved by this embodiment can be found in the description above and will not be repeated here.

[0099] Those skilled in the art can clearly understand that the technology in the embodiments of the present invention can be implemented by means of software plus a necessary general hardware platform. Based on this understanding, the technical solution in the embodiments of the present invention, in essence or in other words, the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, and other media that can store program codes, including several instructions for enabling a computer terminal (which can be a personal computer, a server, or a second terminal, a network terminal, etc.) to execute all or part of the steps of the methods described in each embodiment of the present invention.

[0100] In this specification, the same or similar parts between the various embodiments can be referred to each other. In particular, for the terminal embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description in the method embodiment.

[0101] In the several embodiments provided by the present invention, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are only schematic. For example, the division of the modules is only a logical function division. There may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of systems or modules, which can be electrical, mechanical or other forms.

[0102] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0103] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0104] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A doubly-fed wind turbine impedance modeling method based on VM-DPC, characterized in that: The following steps are involved: A doubly-fed wind turbine system using VM-DPC is constructed based on an induction generator, RSC and GSC, and the electrical parameters, operating state variables and mechanical parameters of the generator are obtained based on the doubly-fed wind turbine system; exist αβ In the coordinate system, an aerodynamic model is constructed based on the mechanical parameters and operating state variables of the generator to obtain the mechanical change information of the mechanical torque under small disturbances. The electromagnetic change information of the electromagnetic torque under small disturbances is obtained based on the electrical parameters and operating state variables of the generator. The small signal model of the rotor speed is constructed by combining the mechanical change information and the electromagnetic change information. exist αβ In the coordinate system, the dynamic relationship between the generator stator power and the stator voltage and current is obtained based on the electrical parameters and operating state variables of the generator, the stator power is linearized to obtain the small signal model of the stator power, and the small signal model of the stator-rotor voltage is constructed based on the small signal model of the rotor speed combined with the stator voltage and the rotor voltage; the RSC partial impedance model is established based on the rotor voltage control command value disturbance combined with the small signal model of the stator power and the small signal model of the stator-rotor voltage; exist αβ In the coordinate system, the dynamic relationship between the GSC output power and the stator voltage and GSC current is obtained based on the electrical parameters and operating state variables. The small signal model of the GSC output power is obtained through linearization. The DC voltage equation is constructed based on the AC voltage and current of the RSC and GSC, and the small signal model of the DC voltage is obtained through linearization. The GSC partial impedance model is established based on the GSC voltage control command value disturbance combined with the small signal model of the GSC output power and the small signal model of the DC voltage. The rotor speed small signal model, RSC partial impedance model and GSC partial impedance model are integrated to construct the VM-DPC-based doubly fed wind turbine impedance model under small disturbance.

2. The impedance modeling method of a doubly-fed wind turbine based on VM-DPC according to claim 1, characterized in that: The doubly-fed wind turbine system based on VM-DPC includes a mechanical subsystem and an electrical subsystem. The impedance model of the doubly-fed wind turbine based on VM-DPC is specifically: in, Small disturbances in the stator voltage Small disturbance of grid-connected current Conjugate of small perturbations in stator voltage Conjugate of small disturbance of current at the grid connection point θ = ω s t + φ s ,in φ s is the initial phase angle of the fundamental frequency voltage, is the impedance of the doubly-fed wind turbine based on VM-DPC, , , , , is the sub-impedance generated in the derivation process of the doubly-fed wind turbine impedance, expressed as: in, is the impedance of RSC related to the stator voltage, is the impedance of the RSC related to the rotor speed, is the impedance related to the rotor voltage and rotor current, is the impedance related to the rotor voltage and rotor speed, is the portion of the mechanical subsystem impedance, is the impedance related to the stator voltage and rotor current, is the impedance of RSC related to the stator current, is the other part of the mechanical subsystem impedance, is the impedance relating the rotor voltage to the stator current, is the impedance related to the stator voltage and stator current, is the impedance of GSC related to the stator voltage, is the impedance of GSC related to the GSC current, is the impedance of GSC related to DC voltage, is the impedance on the DC side related to the GSC voltage, is the impedance on the DC side related to the GSC current, is the impedance on the DC side related to the rotor voltage, is the impedance on the DC side related to the rotor current, is a two-dimensional unit diagonal matrix, is the impedance associated with the grid.

3. The impedance modeling method of a doubly-fed wind turbine based on VM-DPC according to claim 2 is characterized in that: The small signal model of rotor speed specifically includes: Construct an aerodynamic model as follows: in, is the mechanical torque, ρ is the air density, r is the blade length, is the average wind speed, is the torque coefficient, λ = r / represents the tip speed ratio, where is the mechanical angular velocity; Under the assumption of constant wind speed, a small disturbance analysis is performed on the aerodynamic model, and the linear relationship between the small disturbance of mechanical torque and the small disturbance of mechanical angular velocity is obtained; The electromagnetic torque is calculated based on the stator current and the rotor current, and the correlation formula between the electromagnetic torque and the stator current and the rotor current is obtained. The correlation formula is linearized to obtain the electromagnetic change information of the electromagnetic torque under small disturbance; Establish the motion equations of the two mass blocks of the transmission system to describe the dynamic coupling relationship between the mechanical and electromagnetic parts, and perform small signal linearization on the motion equations; The small signal model of the rotor speed is obtained by combining the linear relationship between the small disturbance of mechanical torque and the small disturbance of mechanical angular velocity, the electromagnetic change information of electromagnetic torque under small disturbance and the motion equation after small signal linearization processing, which is: in, is a small disturbance in the rotor speed, is a small disturbance in the stator current, is the conjugate of a small perturbation of the stator current, is a small perturbation of the rotor current, is the conjugate of a small perturbation in the rotor current.

4. The impedance modeling method of a doubly-fed wind turbine based on VM-DPC according to claim 3 is characterized in that: Before establishing the RSC partial impedance model, the RSC control impedance model is established based on the rotor voltage control command value disturbance combined with the small signal model of the stator power, which specifically includes: The active circuit and reactive circuit of RSC control are linearized to obtain the rotor voltage control command value disturbance. α Axis components and β Expressions for the axis components, based on α Axis components and β The expression of the axis component represents the rotor voltage control command value disturbance in the form of a complex vector; Based on the double-fed wind turbine system, the electrical parameters and operating state variables are obtained αβ The stator active power and reactive power in the coordinate system, and the active power and reactive power are linearized to obtain the small signal model of the stator power; The RSC control impedance model in the two-dimensional complex vector space is established based on the rotor voltage control command value disturbance expressed in complex vector form and the small signal model of stator power, as follows: in, is a small perturbation in the rotor voltage, is the conjugate of a small perturbation in the rotor voltage, is a small disturbance in the stator voltage, is the conjugate of a small perturbation in the stator voltage, is a small disturbance in the stator current, is the conjugate of a small perturbation of the stator current, is a small disturbance in the rotor speed.

5. The impedance modeling method of a doubly-fed wind turbine based on VM-DPC according to claim 4 is characterized in that: The RSC partial impedance model between the stator voltage and the stator current is obtained based on the RSC control impedance model, which specifically includes: Based on the main circuit of the induction generator, the stator voltage equation and the rotor voltage equation are obtained, and the small signal model of the stator and rotor voltages is constructed after the stator voltage equation and the rotor voltage equation are linearized; Substitute the small signal model of the rotor speed into the RSC control impedance model, and eliminate the rotor voltage and current disturbance based on the small signal model of the stator and rotor voltage to obtain the RSC partial impedance model between the stator voltage and the stator current: 。 6. The impedance modeling method of a doubly-fed wind turbine based on VM-DPC according to claim 5, characterized in that: Before establishing the GSC partial impedance model, the GSC controlled impedance model is based on the GSC voltage control command value disturbance combined with the small signal model of the GSC output power, which specifically includes: The active circuit and reactive circuit of GSC control are linearized respectively to obtain the disturbance of GSC voltage control command value. α Axis components and β Expressions for the axis components, based on α Axis components and β The expression of the axis component represents the GSC voltage control command value disturbance in the form of a complex vector; Based on the double-fed wind turbine system, the electrical parameters and operating state variables are obtained αβ The GSC outputs active power and reactive power in the coordinate system, and the active power and reactive power are linearized to obtain the small signal model of the GSC output power; The GSC control impedance model in two-dimensional complex vector space is established based on the GSC voltage control command value disturbance expressed in complex vector form and the small signal model of GSC output power, as follows: in, is a small perturbation of the GSC voltage, is the conjugate of a small perturbation of the GSC voltage, is a small disturbance in the stator voltage, is the conjugate of a small perturbation in the stator voltage, is a small perturbation of the GSC current, is the conjugate of a small perturbation of the GSC current, is a small disturbance in the DC bus voltage.

7. The impedance modeling method of a doubly-fed wind turbine based on VM-DPC according to claim 6, characterized in that: The DC bus connects the GSC and RSC. Before establishing the GSC partial impedance model, the frequency domain model of the DC voltage disturbance is obtained, including: According to the equal instantaneous power of the AC side and the DC side of the converter, the DC bus voltage equation is obtained based on the AC voltage and current of the GSC and RSC; The DC bus voltage equation is linearized at the steady-state operation trajectory to obtain αβ The frequency domain model of DC voltage disturbance represented by complex vector in coordinate system includes: ； The interactive influence between the DC side and the AC side is obtained based on the frequency domain model of DC voltage disturbance, and the GSC partial impedance model is constructed based on the GSC controlled impedance model combined with the frequency domain model of DC voltage disturbance.

8. The impedance modeling method of a doubly-fed wind turbine based on VM-DPC according to claim 7, characterized in that: Based on the GSC control impedance model and the frequency domain model of DC voltage disturbance, the GSC partial impedance model between the stator voltage, stator current and GSC current is obtained, including: Based on the filter circuit, the relationship equation between the GSC voltage, the GSC current and the stator voltage is obtained, and the relationship equation is linearized to obtain the transmission relationship between the GSC voltage disturbance and the stator voltage disturbance in the two-dimensional complex vector space; Substituting the frequency domain model of the transfer relationship and DC voltage disturbance into the GSC control impedance model, the GSC partial impedance model between the stator voltage, stator current and GSC current is obtained: 。 9. A doubly-fed wind turbine impedance modeling system based on VM-DPC, characterized in that: When the system is implemented, the impedance modeling method of a doubly-fed wind turbine based on VM-DPC as described in any one of claims 1 to 8 is executed, and the system includes: System building module, building a doubly-fed wind turbine system using VM-DPC based on induction generator, RSC and GSC, and obtaining the electrical parameters, operating state variables and mechanical parameters of the generator based on the doubly-fed wind turbine system; The small signal model building module of the rotor speed is αβ In the coordinate system, an aerodynamic model is constructed based on the mechanical parameters and operating state variables of the generator to obtain the mechanical change information of the mechanical torque under small disturbances. The electromagnetic change information of the electromagnetic torque under small disturbances is obtained based on the electrical parameters and operating state variables of the generator. The small signal model of the rotor speed is constructed by combining the mechanical change information and the electromagnetic change information. RSC partial impedance model building module, in αβ In the coordinate system, the dynamic relationship between the generator stator power and the stator voltage and current is obtained based on the electrical parameters and operating state variables of the generator, the stator power is linearized to obtain the small signal model of the stator power, and the small signal model of the stator-rotor voltage is constructed based on the small signal model of the rotor speed combined with the stator voltage and the rotor voltage; the RSC partial impedance model is established based on the rotor voltage control command value disturbance combined with the small signal model of the stator power and the small signal model of the stator-rotor voltage; GSC partial impedance model building module, in αβ In the coordinate system, the dynamic relationship between the GSC output power and the stator voltage and GSC current is obtained based on the electrical parameters and operating state variables. The small signal model of the GSC output power is obtained through linearization. The DC voltage equation is constructed based on the AC voltage and current of the RSC and GSC, and the small signal model of the DC voltage is obtained through linearization. The GSC partial impedance model is established based on the GSC voltage control command value disturbance combined with the small signal model of the GSC output power and the small signal model of the DC voltage. The doubly-fed wind turbine impedance model construction module integrates the rotor speed small signal model, RSC partial impedance model and GSC partial impedance model to construct a VM-DPC-based doubly-fed wind turbine impedance model under small disturbances.

10. A computer-readable storage medium, characterized in that: The readable storage medium stores a doubly-fed wind turbine impedance modeling program based on VM-DPC, and when the doubly-fed wind turbine impedance modeling program based on VM-DPC is executed by a processor, the steps of the doubly-fed wind turbine impedance modeling method based on VM-DPC as described in any one of claims 1 to 8 are implemented.

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