Grid-connected electric energy quality compensation control method and system of wind turbine generator converter

Abstract

The embodiment of the invention relates to the technical field of intelligent control, and provides a grid-connected electric energy quality compensation control method and system for a wind turbine generator converter, and the method comprises the steps: dynamically generating a self-adaptive cooperative weight which can reflect a power grid support demand and the current capability of the converter through the real-time decomposition and evaluation of the voltage state of a grid-connected point; and furthermore, the positive and negative sequence current instructions are cooperatively generated based on the self-adaptive cooperative weight, so that the control system can perform continuous and smooth dynamic balancing between two opposite targets, optimal distribution of the capacity of the converter is realized, and finally safe and stable operation of the wind turbine generator is considered while a power grid is effectively supported and the electric energy quality is improved. And the grid-connected adaptability of the wind turbine generator under the asymmetric fault is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of intelligent control, in particular to a wind turbine converter grid-connected power quality compensation control method and system. BACKGROUND

[0002] With the increasing proportion of wind power in the global energy structure, large-scale grid-connected wind power has put forward higher requirements for the stable operation and power quality of the power grid. Especially in adverse conditions such as unbalanced grid voltage caused by asymmetric faults, wind turbines not only need to have low voltage ride-through capability to maintain grid-connected operation, but also need to provide necessary support for the power grid to ensure the safety of the power system. Therefore, it is of great significance to study efficient wind turbine converter grid-connected power quality compensation control strategies to improve the environmental adaptability and grid friendliness of wind turbines.

[0003] However, the existing technology usually faces two mutually restrictive control objectives when dealing with grid voltage imbalance: on the one hand, by injecting negative sequence current to support grid voltage and suppress voltage imbalance; on the other hand, by controlling negative sequence current to suppress the active power and electromagnetic torque pulsation of the wind turbine itself to protect the mechanical components of the transmission chain. Limited by the capacity of the converter, it is difficult to achieve optimal control of the two control objectives at the same time. Traditional control strategies often use fixed weights or choose one of the two objectives, lacking the ability to dynamically coordinate control according to the actual imbalance degree of the grid and the current margin of the converter itself. This approach cannot flexibly balance the grid support demand and the safety operation requirement of wind turbines under complex fault conditions, limiting the comprehensive performance of wind turbines during grid faults. SUMMARY

[0004] The present application aims to at least solve one of the problems existing in the prior art, and provides a wind turbine converter grid-connected power quality compensation control method and system.

[0005] In one aspect of the present application, a wind turbine converter grid-connected power quality compensation control method is provided, which comprises: real-time decomposition and evaluation of the three-phase grid-connected point instantaneous voltage to obtain positive sequence voltage d-q components, negative sequence voltage d-q components and voltage imbalance degree; adaptive collaborative weight dynamic generation based on voltage imbalance degree to obtain adaptive collaborative weight; based on the adaptive collaborative weight, positive and negative sequence current instruction collaborative generation is performed on the active power reference value and the positive sequence voltage d-q component to obtain positive sequence d-q axis current reference value and negative sequence d-q axis current reference value; Dual-loop current control is performed on the positive-sequence dq-axis current reference value and the negative-sequence dq-axis current reference value to obtain the dq component of the final voltage modulation signal; Space vector pulse width modulation is performed on the dq component of the final voltage modulation signal to obtain the three-phase PWM gate drive signal.

[0006] Optionally, the instantaneous voltage at the three-phase grid connection point is decomposed and evaluated in real time to obtain the positive-sequence voltage dq component, the negative-sequence voltage dq component, and the voltage imbalance, including: The Clarke transform is performed on the instantaneous voltage at the three-phase grid connection point to obtain Voltage components in the coordinate system; right The voltage components in the coordinate system are separated into positive and negative sequence components and phase-locked based on a dual second-order generalized integrator to obtain... Positive sequence voltage components in coordinate system Negative sequence voltage component and grid voltage phase angle in coordinate system; Based on the grid voltage phase angle, positive sequence voltage components in coordinate system The negative sequence voltage component in the coordinate system is projected onto the rotating coordinate system and the unbalance is calculated to obtain the positive sequence voltage dq component, the negative sequence voltage dq component, and the voltage unbalance.

[0007] Optionally, based on the grid voltage phase angle, for positive sequence voltage components in coordinate system The negative sequence voltage component in the coordinate system is projected onto a rotating coordinate system and the unbalance is calculated to obtain the positive sequence voltage dq component, the negative sequence voltage dq component, and the voltage unbalance, including: Based on the grid voltage phase angle, the following formula is used to... positive sequence voltage components in coordinate system The negative sequence voltage component in the coordinate system is projected onto the rotating coordinate system to obtain the positive sequence voltage dq component and the negative sequence voltage dq component: ; ; in, This represents the negative sequence voltage dq component. It is the negative sequence d-axis voltage. It is the negative sequence q-axis voltage. The positive sequence voltage dq component. The positive-sequence d-axis voltage, This is the positive-sequence q-axis voltage. Let be the phase angle of the grid voltage at time t. For time t Positive sequence voltage components in the coordinate system For time t Positive sequence voltage in coordinate system Quantity, For time t Positive sequence voltage in coordinate system Quantity, For time t Negative sequence voltage component in coordinate system For time t Negative sequence voltage in coordinate system Quantity, For time t Negative sequence voltage in coordinate system Quantity.

[0008] Optionally, based on the grid voltage phase angle, for positive sequence voltage components in coordinate system The negative sequence voltage component in the coordinate system is projected onto a rotating coordinate system and the unbalance is calculated to obtain the positive sequence voltage dq component, the negative sequence voltage dq component, and the voltage unbalance. This also includes: The voltage imbalance is calculated based on the positive-sequence voltage dq component and the negative-sequence voltage dq component using the following formula: ; in, This refers to the voltage imbalance.

[0009] Optionally, adaptive cooperative weights are dynamically generated based on the voltage imbalance to obtain adaptive cooperative weights, including: Calculate the current margin based on the maximum current of the converter and the current amplitude of the grid-side converter; The current margin and voltage imbalance are normalized to obtain the normalized grid support demand factor and the normalized current capacity factor. The adaptive collaborative weight is obtained by multi-factor fusion and collaborative weight generation of the normalized power grid support demand factor and the normalized current capacity factor.

[0010] Optionally, the adaptive coordinated weights are obtained by multi-factor fusion and coordinated weight generation of the normalized grid support demand factor and the normalized current capacity factor, including: The normalized power grid support demand factor and the normalized current capacity factor are multi-factor fusion and coordinated weight generation using the following formula: ; ; in, and All are basic strategy weight coefficients. and respectively are normalized grid support demand factor and normalized current capability factor, is adaptive coordination initial weight, is adaptive coordination weight.

[0011] Optionally, based on the adaptive coordination weight, the active power reference value and the positive sequence voltage d-q component are coordinated to generate positive and negative sequence current instruction to obtain positive sequence d-q axis current reference value and negative sequence d-q axis current reference value, including: Based on the active power reference value and the reactive power reference value, the positive sequence voltage d-q component is processed based on the LVRT strategy and the power instruction to generate a reference positive sequence current instruction to obtain the positive sequence d-q axis current reference value; Based on the negative sequence compensation admittance, the negative sequence voltage d-q component is processed to generate a reference negative sequence current instruction of two opposite targets to obtain a negative sequence d-q axis current reference value for supporting the grid and a negative sequence d-q axis current reference value for suppressing torque ripple; Based on the adaptive coordination weight, the negative sequence d-q axis current reference value for supporting the grid and the negative sequence d-q axis current reference value for suppressing torque ripple are adaptively fused to obtain the final negative sequence d-q axis current reference value.

[0012] Optionally, based on the active power reference value and the reactive power reference value, the positive sequence voltage d-q component is processed based on the LVRT strategy and the power instruction to generate a reference positive sequence current instruction to obtain the positive sequence d-q axis current reference value, including: Based on the LVRT strategy, the active power reference value, the reactive power reference value and the positive sequence voltage d-q component are processed according to the following formula to obtain a dynamic reactive power reference value: ; Wherein, is the dynamic reactive power reference value, is the reactive power reference value, is the reactive power support coefficient specified in the grid code, is the positive sequence d-axis voltage, is the positive sequence q-axis voltage, is the system nominal voltage; Based on the dynamic reactive power reference value and the active power reference value, the positive sequence voltage d-q component is calculated according to the following formula to obtain the positive sequence d-q axis current reference value: ; ; Wherein, is the active power reference value, a positive sequence d-axis current reference value, a positive sequence q-axis current reference value.

[0013] Optionally, based on the adaptive cooperative weight, the negative sequence d-q axis current reference value for supporting the power grid and the negative sequence d-q axis current reference value for suppressing torque ripple are adaptively weighted and fused to obtain a final negative sequence d-q axis current reference value, including: Based on the adaptive cooperative weight, the negative sequence d-q axis current reference value for supporting the power grid and the negative sequence d-q axis current reference value for suppressing torque ripple are adaptively weighted and fused according to the following formula: ; Wherein, and respectively, the negative sequence d-q axis current reference value for supporting the power grid and the negative sequence d-q axis current reference value for suppressing torque ripple, is the adaptive cooperative weight, is the final negative sequence d-q axis current reference value.

[0014] Another aspect of the present application provides a wind turbine converter grid-connected power quality compensation control system, which comprises: A grid point power grid state real-time decomposition and evaluation module is configured to perform grid point power grid state real-time decomposition and evaluation on three-phase grid point instantaneous voltage to obtain positive sequence voltage d-q components, negative sequence voltage d-q components and voltage unbalance degree. An adaptive cooperative weight dynamic generation module is configured to perform adaptive cooperative weight dynamic generation based on the voltage unbalance degree to obtain an adaptive cooperative weight. A positive and negative sequence current instruction cooperative generation module is configured to perform positive and negative sequence current instruction cooperative generation based on the adaptive cooperative weight, on the active power reference value and the positive sequence voltage d-q components, to obtain a positive sequence d-q axis current reference value and a negative sequence d-q axis current reference value. A double-loop current control module is configured to perform double-loop current control on the positive sequence d-q axis current reference value and the negative sequence d-q axis current reference value to obtain d-q components of a final voltage modulation signal. A space vector pulse width modulation module is configured to perform space vector pulse width modulation on the d-q components of the final voltage modulation signal to obtain a three-phase PWM gate drive signal.

[0015] The present application, relative to the prior art, dynamically generates an adaptive coordination weight reflecting the grid support demand and the current capacity of the converter by real-time decomposition and evaluation of the grid point voltage state; further generates the positive and negative sequence current instructions based on the adaptive coordination weight, so that the control system can continuously and smoothly dynamically weigh between the two opposite targets, realize the optimal allocation of the converter capacity, and finally effectively support the grid and improve the power quality while taking into account the safe and stable operation of the wind turbine itself, and improve the grid connection adaptability of the wind turbine under asymmetric fault. BRIEF DESCRIPTION OF DRAWINGS

[0016] One or more embodiments are illustrated by way of example in the figures that are part of this disclosure and which will help understand various aspects of the present application. The appended drawings and their descriptions thereof are incorporated in and constitute part of this disclosure. Unless otherwise noted, elements of one embodiment that are the same as or similar to elements of another embodiment are identified with the same reference numerals and different reference numerals are used to identify different elements of the embodiments. The figures are not to scale, and the size, location, and / or relative size of the elements in the figures are intended to illustrate but not limit the present application.

[0017] Figure 1 A flow chart of a wind turbine converter grid-connected power quality compensation control method according to an embodiment of the present application is provided. Figure 2 A data flow schematic diagram of a wind turbine converter grid-connected power quality compensation control method according to another embodiment of the present application is provided. Figure 3 A block diagram of a wind turbine converter grid-connected power quality compensation control system according to another embodiment of the present application is provided. DETAILED DESCRIPTION

[0018] Hereinafter, example embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, and do not represent all the embodiments of the present application. It should be understood that the present application is not limited to the example embodiments described herein.

[0019] As shown in the specification and claims of the present application, unless the context clearly indicates otherwise, the words "one", "an", "a", and / or "the" do not mean a single number, but can also include a plurality. Generally, the terms "comprise" and "include" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements.

[0020] Although the present application makes various references to certain modules in the system according to the embodiments of the present application, however, any number of different modules can be used and run on the user terminal and / or server. The modules are only illustrative, and different aspects of the system and method can use different modules.

[0021] Flowcharts are used in the present disclosure to illustrate the operations performed by the system according to embodiments of the present disclosure. It should be understood that the foregoing or following operations are not necessarily performed in sequence. Instead, various steps can be processed in reverse order or simultaneously, as needed. Meanwhile, other operations can be added to these processes, or one or more steps can be removed from these processes.

[0022] In the technical solution of the present disclosure, a wind turbine converter grid-connected power quality compensation control method is provided. Figure 1 A flowchart of the wind turbine converter grid-connected power quality compensation control method according to an embodiment of the present disclosure. Figure 2 A data flow diagram of the wind turbine converter grid-connected power quality compensation control method according to an embodiment of the present disclosure. In combination with Figure 1 and Figure 2 The wind turbine converter grid-connected power quality compensation control method according to an embodiment of the present disclosure includes the following steps: S1, real-time decomposition and evaluation of the three-phase grid-connected point instantaneous voltage to obtain positive sequence voltage d-q components, negative sequence voltage d-q components, and voltage unbalance degree; S2, adaptive collaborative weight dynamic generation based on the voltage unbalance degree to obtain an adaptive collaborative weight; S3, positive and negative sequence current instruction collaborative generation based on the adaptive collaborative weight to obtain positive sequence d-q axis current reference values and negative sequence d-q axis current reference values; S4, double-loop current control on the positive sequence d-q axis current reference values and the negative sequence d-q axis current reference values to obtain d-q components of the final voltage modulation signal; and S5, space vector pulse width modulation on the d-q components of the final voltage modulation signal to obtain three-phase PWM gate drive signals.

[0023] In particular, in S1, the three-phase grid-connected point instantaneous voltage is decomposed and evaluated in real time to obtain positive sequence voltage d-q components, negative sequence voltage d-q components, and voltage unbalance degree. Here, it should be understood that in an ideal symmetrical power grid, the voltage only contains positive sequence components. However, in an actual power grid, due to factors such as uneven load and asymmetric faults, negative sequence voltage components are generated, resulting in three-phase voltage imbalance. This imbalance can have a serious impact on the stable operation of the wind turbine, for example, negative sequence voltage can cause negative sequence current in the generator stator winding, which in turn can cause torque pulsation, equipment overheating and vibration, and shorten the service life of the unit. Therefore, by decomposing the positive and negative sequence voltage components in real time, the symmetrical and asymmetrical parts of the power grid can be clearly understood. At the same time, the calculated voltage unbalance degree provides a quantitative index for the subsequent control strategy, so that the control system can dynamically adjust its compensation target according to the severity of the imbalance, and decide whether to prioritize supporting the grid voltage stability or prioritize suppressing the torque pulsation of the unit, thereby achieving intelligent and adaptive compensation and control of power quality.

[0024] The instantaneous voltage at the three-phase grid connection point refers to the real-time values ​​of the A, B, and C phase voltages measured at the point of common coupling (PCC) between the wind turbine converter and the grid, serving as the original input signal for the entire analysis. The positive-sequence voltage component is a symmetrical component within the three-phase unbalanced voltage; its phase sequence matches the normal phase sequence of the grid's fundamental voltage, representing a healthy and symmetrical voltage portion used for transmitting effective power in the grid. The negative-sequence voltage component is another symmetrical component, with a phase sequence opposite to the normal phase sequence; its existence is a direct indicator of grid voltage imbalance. Converting these AC quantities to dq components involves a coordinate transformation (Park transformation) that transforms the variables in the three-phase AC system into a synchronously rotating two-dimensional orthogonal coordinate system (d-axis and q-axis). Under steady-state conditions, the AC quantities are represented as DC quantities in this coordinate system, greatly simplifying controller design, especially for PI controllers. Voltage imbalance is a key indicator for quantifying the degree of grid voltage asymmetry, typically defined as the ratio of the negative-sequence voltage amplitude to the positive-sequence voltage amplitude; a larger value indicates a more severe grid voltage imbalance.

[0025] In a specific implementation, S1 first involves performing a Clarke transformation on the instantaneous voltage at the three-phase grid connection point to obtain... Voltage components in a coordinate system. That is, transforming the instantaneous voltage values ​​collected in the three-phase stationary coordinate system (A, B, C) to a two-phase stationary coordinate system. In a coordinate system. The purpose of this transformation is to reduce the dimensionality, converting the three-phase AC system into an equivalent two-phase system, thus simplifying subsequent calculations and analysis; Next, regarding The voltage components in the coordinate system are separated into positive and negative sequence components and phase-locked based on a dual second-order generalized integrator to obtain... Positive sequence voltage components in coordinate system The negative-sequence voltage component and the phase angle of the grid voltage in the coordinate system. Among them, the Dual Second-Order Generalized Integrator (DSOGI) is an advanced digital signal processing algorithm commonly used in phase-locked loops (PLLs). It can extract the fundamental component of a signal while generating a signal orthogonal to it, and can effectively separate the input signal into its positive-sequence and negative-sequence components, exhibiting excellent filtering performance and dynamic response speed. In this process, the PLL module receives the voltage output from the Clarke transform. Components and voltage After component analysis, the module begins operation. Internally, this phase-locked loop (PLL) module contains two parallel SOGI structures, one for processing positive-sequence components and the other for processing negative-sequence components. Through specific algorithm design, this module can simultaneously achieve three objectives: firstly, to process the input... The voltage component is decomposed into components representing symmetrical parts. positive-sequence voltage component in the stationary coordinate system and the component representing the asymmetric part negative-sequence voltage component in the stationary coordinate system; secondly, the fundamental voltage phase angle of the power grid is tracked and output accurately by phase-locked loop of the positive-sequence component thirdly, harmonic and noise interference is effectively filtered out, ensuring the accuracy of the decomposition result Further, based on the power grid voltage phase angle, the positive-sequence voltage d-q component, the negative-sequence voltage d-q component and the voltage unbalance degree are obtained by rotating coordinate system projection and unbalance degree calculation of the positive-sequence voltage component in the stationary coordinate system and the negative-sequence voltage component in the stationary coordinate system That is, the positive-sequence and negative-sequence voltage components separated out in the stationary coordinate system are respectively subjected to Park transformation and projected onto the synchronous rotating d-q coordinate system by using the power grid voltage phase angle obtained in the previous step Specifically, to calculate the d component of the positive-sequence voltage, the positive-sequence voltage component in the stationary coordinate system is multiplied by the cosine value of the power grid voltage phase angle, and then added to the positive-sequence voltage component in the stationary coordinate system multiplied by the sine value of the power grid voltage phase angle To calculate the q component of the positive-sequence voltage, the positive-sequence voltage component in the stationary coordinate system is multiplied by the negative sine value of the power grid voltage phase angle, and then added to the positive-sequence voltage component in the stationary coordinate system multiplied by the cosine value of the power grid voltage phase angle For the calculation of the negative-sequence voltage d-q component, the same calculation logic is adopted to convert the alternating signal in the stationary coordinate system to a coordinate system synchronous with the positive-sequence voltage of the power grid, so that the originally sinusoidal positive-sequence voltage component becomes a constant direct current, which greatly facilitates the design and implementation of the subsequent controller Specifically, based on the power grid voltage phase angle, the positive-sequence voltage component in the stationary coordinate system and the negative-sequence voltage component in the stationary coordinate system are subjected to rotating coordinate system projection to obtain the positive-sequence voltage d-q component and the negative-sequence voltage d-q component ​​​​​​​​​​​​​​​​the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t the positive-sequence voltage component in the d-q coordinate system at time t After obtaining the positive-sequence voltage d-q component and the negative-sequence voltage d-q component, the voltage unbalance degree is calculated immediately. In this process, first, the amplitudes of the negative-sequence voltage and the positive-sequence voltage are calculated respectively, and then the two are divided. The calculation of the voltage amplitude follows the calculation method of the vector module, that is, the sum of the square of the d component and the square of the q component is taken, and then the square root of the sum value is taken. Therefore, the specific calculation steps of the voltage unbalance degree are as follows: first, the square root of the sum of the square of the negative-sequence d-axis voltage and the square of the negative-sequence q-axis voltage is calculated to obtain the amplitude of the negative-sequence voltage; then the amplitude of the positive-sequence voltage is calculated in the same way; finally, the calculated amplitude of the negative-sequence voltage is divided by the amplitude of the positive-sequence voltage to obtain the voltage unbalance degree. This process strictly follows the standard definition of the voltage unbalance degree, that is, the ratio of the amplitude of the unhealthy negative-sequence component to the amplitude of the healthy positive-sequence component in the power grid, thereby obtaining a normalized index that can accurately quantify the degree of asymmetry of the power grid. Specifically, the voltage unbalance degree is calculated based on the positive-sequence voltage d-q component and the negative-sequence voltage d-q component as follows: ; wherein, is the voltage unbalance degree.

[0026] Through the above steps, the overall and real-time decomposition and evaluation of the grid state of the grid connection point are completed.

[0027] In particular, the S2 is based on the voltage imbalance degree to adaptively generate a dynamic cooperative weight to obtain an adaptive cooperative weight. It should be understood that when the power grid is unbalanced, the converter usually faces two opposite control objectives: one is to support the stability of the power grid, that is, to compensate for the negative sequence voltage of the power grid by actively injecting negative sequence current, thereby improving the power quality of the grid point and helping the power grid to restore balance; the second is to ensure the smooth operation of itself, that is, to completely eliminate the negative sequence current in the stator winding by adjusting the control strategy, so as to suppress the torque ripple and power fluctuation generated thereby, and to protect the generator and the mechanical transmission chain. However, due to the limited current output capacity of the converter, these two objectives cannot be perfectly achieved at the same time in most cases. Injecting negative sequence current to support the power grid will inevitably occupy the capacity of the converter, while completely suppressing the negative sequence current of itself means giving up the support for the power grid. The traditional fixed and preset control strategy cannot adapt to the dynamic changes of the power grid imbalance degree and the operation state of the converter itself, so in the technical solution of the present application, a dynamic and intelligent decision mechanism is established to evaluate the necessity and feasibility of supporting the power grid in real time, and to integrate it into a single adaptive cooperative weight. The adaptive cooperative weight will guide the system to find a best balance point between supporting the power grid and self-protection, and maximize the control benefit.

[0028] In the specific implementation of the S2, first, based on the maximum current of the converter and the current amplitude of the grid-side converter, the current margin is calculated. It should be understood that the converter, as the core component of power transformation, its carrying current capacity is strictly limited by its internal power semiconductor devices (such as IGBT) physical characteristics, there is an absolute upper limit, that is, the maximum current of the converter. At any time, the current output by the converter is used to meet various needs, such as transmitting active power, providing reactive power support, etc. When the power grid is unbalanced, if you want to perform compensation tasks such as injecting negative sequence current to support the power grid, you must output an additional part of the current. Therefore, before making any compensation decision, based on the maximum current of the converter and the current amplitude of the grid-side converter, the current margin is calculated, which provides a clear and direct physical quantity for the control system by evaluating the gap between the current load and the hardware limit. Among them, the current margin refers to the current capacity of the converter that can be used to perform additional control tasks, specifically the difference between the rated maximum output current of the converter and the current actual output current amplitude. It directly reflects the ability or load pressure of the converter, and is an important basis for evaluating whether it has enough capacity to support the power grid. In an example, the greater the margin, the less the pressure, the more resources can be allocated.

[0029] The maximum current of the converter is a static parameter representing the hardware capability of the converter, which refers to the maximum current effective value or amplitude that the converter can continuously and safely output under normal working conditions when designed and manufactured. This value is jointly determined by the rated current of the power switch device inside the converter, the capacity of the heat dissipation system, and the related protection settings, and is an insurmountable physical limit of the converter. In the control software, it usually exists as a fixed configuration parameter. The current amplitude of the grid-side converter is a dynamic variable reflecting the current workload of the converter, which refers to the synthesized amplitude of the three-phase current output by the converter to the grid in the space vector, which comprehensively considers the current component for active power transmission, the current component for reactive power regulation, and any other compensation current component that may exist, and is a real-time measurement of the total output current of the converter.

[0030] Then, the S2 normalizes the current margin and the voltage imbalance to obtain a normalized grid support demand factor and a normalized current capability factor. The normalized grid support demand factor is a dimensionless index that maps the voltage imbalance calculated in the previous step to a standardized interval (such as 0 to 1), and the size of this factor directly represents the urgency of the demand for negative sequence compensation of the grid. The more serious the voltage imbalance, the larger the value of this factor. The normalized current capability factor is another dimensionless index that also maps the calculated current margin to a standardized interval, and the size of this factor represents the strength of the converter's ability to provide additional compensation current. The larger the current margin, the larger the value of this factor. Here, it should be understood that the original voltage imbalance and current margin have different physical units and value ranges, and are not convenient for direct fusion calculation. Therefore, in the technical solution of the present application, the current margin and the voltage imbalance are normalized to map them to a unified and comparable scale, usually the [0, 1] interval. For the voltage imbalance, it is converted into a normalized grid support demand factor according to a predetermined rule. For example, a threshold value of the imbalance can be set, and when the actual imbalance exceeds the threshold value, the demand factor is 1, indicating that the grid urgently needs support; when the imbalance is below a certain dead zone value, the demand factor is 0. For the current margin, it is converted into a normalized current capability factor. For example, a proportional value can be obtained as the capability factor by dividing the actual current margin by the maximum current of the converter, and when the margin is zero, the capability factor is 0, indicating that the converter is full load and cannot provide additional support.

[0031] Further, the S2 performs multi-factor fusion and collaborative weight generation on the normalized grid support demand factor and the normalized current capability factor to obtain the adaptive collaborative weight. In this process, the normalized grid support demand factor is multiplied by its corresponding basic strategy weight coefficient to obtain a first product; at the same time, the normalized current capability factor is multiplied by its corresponding basic strategy weight coefficient to obtain a second product; finally, the two products are added, and the sum is the generated adaptive collaborative initial weight; then the adaptive collaborative initial weight is compared with 1, and the minimum of the two is taken with the maximum value in 0, which is the final adaptive collaborative weight. The basic strategy weight coefficient predefines the basic importance of the two factors in decision-making. In this way, complex and multi-dimensional working condition information (the severity of grid imbalance and the load condition of the converter itself) is ingeniously fused into a single and clear guiding weight. Specifically, the multi-factor fusion and collaborative weight generation of the normalized grid support demand factor and the normalized current capability factor are as follows: ; ; wherein, and are basic strategy weight coefficients, and are the normalized grid support demand factor and the normalized current capability factor, is the adaptive collaborative initial weight, is the adaptive collaborative weight.

[0032] In particular, the S3, based on the adaptive coordination weight, generates positive and negative sequence current instruction in coordination with the active power reference value and the positive sequence voltage d-q component to obtain the positive sequence d-q axis current reference value and the negative sequence d-q axis current reference value. The wind turbine is connected to the grid, and its primary task is to deliver active power to the grid and adjust the necessary reactive power according to the wind energy conditions and the upper-level scheduling instructions, which is mainly achieved by controlling the positive sequence current. However, when the grid voltage is unbalanced, it is not enough to control the positive sequence current alone. In order to cope with the negative effects of imbalance, the system must actively manage the negative sequence current at the same time. The core of this step is to generate in coordination: instead of calculating the positive and negative sequence current instructions separately, the two are planned as a whole. The generation of the positive sequence current instruction ensures the basic power generation task of the unit and the conventional support to the grid (such as reactive power support during low voltage ride through); while the generation of the negative sequence current instruction is guided by the adaptive coordination weight generated in the previous step, and the compensation strategy for imbalance is accurately executed. This coordination mechanism ensures that under any operating condition, the total current instruction generated can not only meet the power generation demand, but also intelligently and proportionally execute the imbalance compensation, while always respecting the physical current limit of the converter, thereby optimizing the control target and ensuring the safety of equipment operation.

[0033] Among them, the active power reference value is usually given by the highest-level controller of the wind turbine (such as the maximum power point tracking MPPT algorithm), which represents the expected active power output under current wind conditions.

[0034] The S3, in specific implementation, first, based on the active power reference value, the reactive power reference value, the positive sequence voltage d-q component, the reference positive sequence current instruction is generated based on the LVRT strategy and the power instruction to obtain the positive sequence d-q axis current reference value. In this process, first, the reactive power reference value is dynamically adjusted according to the LVRT strategy. The calculation logic is: first, calculate the amplitude of the current positive sequence voltage, that is, square and square root of the d-axis and q-axis components of the positive sequence voltage; then, subtract the calculated current voltage amplitude from the system nominal voltage to obtain the depth of voltage drop; then, multiply the maximum of the voltage drop depth and 0 by a reactive power support coefficient specified by the grid code; finally, add the product to the initial reactive power reference value to obtain the final dynamic reactive power reference value. This process strictly follows the requirements of low voltage ride through: when the grid voltage is detected to drop, the reactive power output instruction can be automatically and proportionally increased, thereby actively injecting reactive current to the grid to support the recovery of the grid voltage. Specifically, the active power reference value, the reactive power reference value and the positive sequence voltage d-q component are processed based on the LVRT strategy to obtain the dynamic reactive power reference value as follows: ; Among them, for the dynamic reactive power reference value, for the reactive power reference value, for the reactive power support factor specified by grid codes, for the positive-sequence d-axis voltage, for the positive-sequence q-axis voltage, for the system nominal voltage; Then, after obtaining the dynamic reactive power reference value, the reference positive-sequence current can be calculated. The calculation logic is derived from the instantaneous power theory in the synchronous rotating coordinate system. For the positive-sequence d-axis current reference value, the numerator part is composed of the product of the active power reference value and the positive-sequence d-axis voltage, plus the product of the dynamic reactive power reference value and the positive-sequence q-axis voltage; for the positive-sequence q-axis current reference value, the numerator part is composed of the product of the active power reference value and the positive-sequence q-axis voltage, minus the product of the dynamic reactive power reference value and the positive-sequence d-axis voltage. The two numerators are divided by the same denominator, which is the square of the amplitude of the positive-sequence voltage (the sum of the square of the d-axis component and the square of the q-axis component). Finally, the obtained quotient is multiplied by a proportional coefficient of three-sixths. The proportional coefficient of three-sixths is to match the power-invariant coordinate transformation. Specifically, based on the dynamic reactive power reference value and the active power reference value, the positive-sequence voltage d-q components are calculated for the reference positive-sequence current to obtain the positive-sequence d-q axis current reference value according to the following formula: ; ; wherein, for the active power reference value, for the positive-sequence d-axis current reference value, for the positive-sequence q-axis current reference value.

[0035] Next, based on the negative-sequence compensation admittance, S3 generates two opposing negative-sequence current commands for the negative-sequence voltage dq component to obtain a negative-sequence dq-axis current reference value aimed at supporting the power grid and a negative-sequence dq-axis current reference value aimed at suppressing torque ripple. The negative-sequence dq-axis current reference value aimed at supporting the power grid is one such reference command, whose core objective is to improve the power quality at the grid connection point. That is, the converter behaves as a controllable negative-sequence admittance, actively injecting a negative-sequence current proportional to the magnitude of the grid's negative-sequence voltage and opposite in phase (or at a specific angle), thereby offsetting or weakening the grid's negative-sequence voltage and helping the grid restore balance. The negative-sequence dq-axis current reference value aimed at suppressing torque ripple is the other reference command, whose core objective is to ensure the stable operation of the wind turbine itself. Since the interaction between negative-sequence current and the positive-sequence magnetic field inside the motor is the root cause of second-harmonic torque pulsation, the most direct and effective way to completely eliminate this pulsation is to ensure that the converter does not generate any negative-sequence current, even if it means sacrificing support for the power grid. Negative-sequence compensation admittance is a complex number, where the real part (negative-sequence conductance) determines the negative-sequence active power exchanged to compensate for negative-sequence voltage, and the imaginary part (negative-sequence susceptance) determines the negative-sequence reactive power exchanged. By setting different values ​​for the real and imaginary parts, the specific methods of supporting the power grid can be flexibly defined.

[0036] In this process, firstly, the reference value of the negative-sequence dq-axis current aimed at supporting the power grid is calculated. The core basis of this calculation is the generalized form of Ohm's law in AC systems, namely, current equals voltage multiplied by admittance. The controller uses the previously precisely decomposed negative-sequence voltage dq component and preset negative-sequence compensation admittance parameters to calculate the ideal compensation current. In the synchronously rotating dq coordinate system, the multiplication operation of complex admittance can be expanded into the following real matrix operation: ; ; in, and These are the negative sequence current dq-axis reference values ​​for supporting the power grid. The conductance is the negative-sequence equivalent admittance. The susceptance is the negative-order equivalent admittance. The negative sequence voltage d-axis component The negative sequence voltage q-axis component is used for calculation. The converter is then instructed to inject a precise negative sequence current, the magnitude of which and the phase angle are determined by the negative sequence voltage state of the grid and the set compensation strategy. Then, negative sequence d-q axis current reference values aimed at suppressing torque pulsation are calculated. In order to fundamentally eliminate the influence of negative sequence current on motor torque, the control strategy must ensure that the inverter does not generate any negative sequence current component. Therefore, the ideal current instruction of this target is zero in any case. Its mathematical expression is: ; ; wherein, is a negative sequence d-axis current reference value aimed at suppressing torque pulsation, is a negative sequence q-axis current reference value aimed at suppressing torque pulsation. The controller only needs to set these two reference values directly to zero. That is, regardless of the state of the external power grid, only the protection of the device itself is the only target. After completing these two parallel calculation tasks, two reference negative sequence current instruction vectors are obtained, which provide the necessary input for the subsequent adaptive weight fusion step.

[0037] Further, the S3 performs adaptive weight fusion on the negative sequence d-q axis current reference values aimed at supporting the power grid and the negative sequence d-q axis current reference values aimed at suppressing torque pulsation based on the adaptive cooperative weight to obtain the final negative sequence d-q axis current reference values. The previous steps have provided two clear options: complete support for the power grid and complete suppression of torque pulsation. However, in most actual working conditions, choosing either extreme is not the optimal solution. For example, when the power grid imbalance is serious but the inverter has insufficient margin, if the instruction to completely support the power grid is forcibly executed, it may cause the inverter to overcurrent; conversely, if the power grid demand is completely ignored, it will weaken the grid-connected performance of the wind turbine as a friendly power source. Therefore, in the technical solution of the present application, the adaptive weight fusion is performed on the negative sequence d-q axis current reference values aimed at supporting the power grid and the negative sequence d-q axis current reference values aimed at suppressing torque pulsation, and a dynamic and smooth transition is performed on the two. This enables the control system to accurately proportionally allocate its negative sequence current output capability according to the size of the adaptive cooperative weight, neither ignoring the plight of the power grid nor sacrificing its own safety, thereby achieving the best balance between control benefits and operating risks.

[0038] Specifically, the adaptive weight fusion is performed on the negative sequence d-q axis current reference values aimed at supporting the power grid and the negative sequence d-q axis current reference values aimed at suppressing torque pulsation based on the adaptive cooperative weight according to the following formula: ; wherein, and are the negative sequence d-q axis current reference values aimed at supporting the power grid and the negative sequence d-q axis current reference values aimed at suppressing torque pulsation, respectively, for adaptive cooperation weight, for final negative sequence d-q axis current reference value. The final output negative sequence current instruction is a linear combination of the two reference instructions. The adaptive cooperation weight determines the weight of the grid reference instruction; while the remaining weight determines the reference instruction for suppressing torque ripple. When tends to 1 (indicating that the grid urgently needs support and the converter has sufficient capacity), the final instruction tends to the instruction for fully supporting the grid; while when tends to 0 (indicating that the grid is in good condition or the converter has no margin), the final instruction tends to zero, prioritizing self-protection; when between 0 and 1, the final instruction is a smooth, proportional compromise between the two extreme strategies.

[0039] In particular, the S4 performs double-loop current control on the positive sequence d-q axis current reference value and the negative sequence d-q axis current reference value to obtain the d-q components of the final voltage modulation signal. It should be understood that the grid is a dynamic and complex system with many uncertain factors such as voltage fluctuations and impedance changes, which will interfere with the current output of the converter. If open-loop control is used, i.e. the voltage instruction is calculated directly according to a simplified model, the actual output current will deviate greatly from the expected value, and effective power control and power quality compensation cannot be achieved. Therefore, in the technical solution of the present application, a double-loop structure is used to control the positive and negative sequence components simultaneously. Specifically, by establishing two independent control channels, the positive and negative sequence current instructions are tracked respectively, decoupling and parallel processing of conventional power transmission and unbalanced compensation tasks are realized, and mutual interference is avoided. Control is performed in the synchronous rotating d-q coordinate system, which can convert the control problem of alternating current into that of direct current, so that a PI (proportional-integral) controller with excellent performance can be used to realize zero-error tracking of the current, which is the key to ensuring control accuracy and system stability.

[0040] The S4 can be decomposed into three core sub-steps in specific implementation: positive sequence current loop control, negative sequence current loop control, and synthesis of the final modulation signal.

[0041] First, the positive sequence current loop control, the target of this positive sequence current loop is to make the actual positive sequence current accurately track its reference value. First, the positive sequence current error of d-axis and the positive sequence current error of q-axis are calculated: then, the two error signals are sent to two independent PI controllers respectively, and the outputs of the PI controllers are subjected to decoupling control and grid voltage feedforward compensation to generate the voltage instruction of the positive sequence component. This process is represented by the formula: ; ; wherein, and are the proportional and integral gains of the positive sequence PI controller, respectively; is the synchronous angular frequency of the grid; is the grid-side equivalent inductance; and are the q-axis and d-axis positive decoupling terms, respectively, used to counteract the cross-coupling between d-q axes; and are the measured positive sequence d-axis grid voltage and positive sequence q-axis grid voltage, respectively, as feedforward terms to compensate for grid voltage disturbances; and are the voltage command of the positive sequence d-component and the voltage command of the positive sequence q-component, respectively.

[0042] Secondly, the negative sequence current loop control. This loop is similar to the positive sequence loop structure, but its goal is to make the actual negative sequence current accurately track its reference value. Similarly, the error is calculated and fed into an independent PI controller. Since the negative sequence component rotates at an angular frequency of in the synchronous reference frame, but the control is usually carried out in the respective rotating reference frame, here, the control in the positive sequence synchronous reference frame is considered, the negative sequence component rotates at an angular frequency of . Therefore, the sign of its decoupling term is opposite to that of the positive sequence loop. This process is expressed in the formula as: ; ; wherein, and are the proportional gain and integral gain of the negative sequence PI controller, respectively; and are the d-axis negative sequence current error and q-axis negative sequence current error, respectively; and are the negative sequence d-axis grid voltage and negative sequence q-axis grid voltage, respectively; and are the q-axis and d-axis negative decoupling terms, respectively; and are the voltage command of the negative sequence d-component and the voltage command of the negative sequence q-component, respectively.

[0043] Further, since the positive and negative sequence components are linearly superimposed in the grid, the total voltage that the converter needs to generate should also be a linear superposition of the positive and negative sequence voltage commands. Therefore, in the technical solution of the present application, the positive and negative sequence voltage commands calculated in the first two sub-steps are further vector added to obtain the final voltage modulation signal d-q component. This process is expressed in the formula as: ; ; wherein, and are the d-axis component and q-axis component of the final voltage modulation signal, respectively.

[0044] In particular, the S5, the d-q components of the final voltage modulation signal are subjected to space vector pulse width modulation to obtain three-phase PWM gate drive signals. It should be understood that the power devices of the converter are essentially high-speed switches, which can only be in two states of complete conduction (ON) or complete turn-off (OFF), and cannot directly generate an analog sinusoidal voltage of any amplitude and phase. Therefore, in the technical solution of the present application, pulse width modulation (PWM) technology is adopted, and by combining these switching states with different time widths (pulse widths) in a very short period, the average effect of the output voltage in a period is equivalent to the expected voltage. Among the many PWM technologies, space vector pulse width modulation (SVPWM) is selected because it has significant technical advantages: first, compared with traditional sinusoidal pulse width modulation (SPWM), SVPWM has higher utilization rate of DC bus voltage and can output higher amplitude AC voltage, thereby improving the power output capability of the system; second, SVPWM has lower harmonic content, which improves the waveform quality of the output current and reduces the harmonic pollution to the power grid. It is worth mentioning that space vector pulse width modulation regards the eight basic switching states (six effective vectors and two zero vectors) of the three-phase inverter as eight basic voltage vectors in space. The core idea is to synthesize any desired reference voltage vector by acting on two adjacent effective vectors and a zero vector in a specific time ratio in each PWM period. The three-phase PWM gate drive signal obtained is a set of (usually six) digital logic signals of high and low levels, which is used to directly control the gate of the six power switch tubes in the three-phase inverter bridge to determine the conduction and turn-off states of the six power switch tubes.

[0045] The S5 can be decomposed into four core sub-steps in specific implementation: coordinate transformation, sector judgment, vector action time calculation, and PWM waveform generation.

[0046] First of all, coordinate transformation. It should be understood that the SVPWM algorithm itself is defined in a fixed two-dimensional coordinate system (d-q coordinate system), while the upstream controller works in a coordinate system (d-q coordinate system) that rotates synchronously with the power grid. Therefore, before the voltage instruction is given to the SVPWM module, it needs to be subjected to inverse Park transformation. That is, the input voltage reference value in the d-q coordinate system is transformed back to the static coordinate system. Specifically, ​​The calculation method of the component is to multiply the d-axis voltage reference value by the cosine value of the real-time phase angle of the power grid, and then subtract the q-axis voltage reference value multiplied by the sine value of the phase angle. The calculation method of the component is to multiply the d-axis voltage reference value by the cosine value of the real-time phase angle of the power grid, and then subtract the q-axis voltage reference value multiplied by the sine value of the phase angle.

[0047] Secondly, sector judgment. Specifically, since The plane is divided into six 60-degree sector regions by six basic effective vectors, and any vector within each sector can be linearly combined by two effective vector on its boundary. Therefore, by performing a specific linear combination on and the components, three intermediate variables are generated, and then the sector number where the reference vector is located is uniquely determined according to the signs (positive or negative) of the three intermediate variables.

[0048] Then, the calculation of vector action time. In one specific example of the present application, according to the volt-second balance principle, the time that the two adjacent effective vectors and a zero vector determined in the last step need to act respectively within a PWM period is calculated. For a given sector, the calculation formula is fixed, which is usually to perform a specific linear combination on and the voltage components, and then multiply by a proportional coefficient determined by the PWM period and the DC bus voltage, so as to obtain the action time of the two effective vectors. The action time of the zero vector is obtained by subtracting the action time of the two effective vectors from the total PWM period. This ensures that in an average sense, discrete switching actions can be equivalently synthesized into continuous target voltage.

[0049] Finally, PWM waveform generation. That is, the three action times calculated in the last step are allocated as the on-time of the upper bridge arm of each phase. Specifically, according to the sector, the on-time of each phase is determined by a specific combination of action times. For example, using a seven-segment modulation method, the zero vector action time is usually divided equally and placed at the beginning and end of the period. Then, according to the sector rule, the action time of the two effective vectors is inserted into it, thereby obtaining the total on-time of the upper bridge arm of each phase within a period. This process converts the abstract concept of action time into specific numerical values that can be directly loaded into the PWM hardware module of the digital controller. These numerical values are compared with the counters inside the PWM module, and when the conditions are met, the hardware automatically generates the switching of high and low levels to form the gate signal that finally drives the power switch tube, completing the last step of conversion from digital instructions to physical driving.

[0050] In summary, the grid-connected power quality compensation control method for wind turbine converters according to embodiments of the present invention is explained. It dynamically generates an adaptive cooperative weight that reflects the grid support requirements and the current capacity of the converter by real-time decomposition and evaluation of the grid connection point voltage state. Furthermore, based on this adaptive cooperative weight, positive and negative sequence current commands are generated in a coordinated manner, enabling the control system to make continuous and smooth dynamic trade-offs between the two opposing objectives, thereby achieving optimal allocation of converter capacity. Ultimately, while effectively supporting the grid and improving power quality, it also takes into account the safe and stable operation of the wind turbine itself, and improves the grid-connected adaptability of the wind turbine under asymmetrical faults.

[0051] This invention also provides a grid-connected power quality compensation control system for wind turbine converters.

[0052] Figure 3 This is a block diagram of a wind turbine converter grid-connected power quality compensation control system according to an embodiment of the present invention. Figure 3 As shown, the wind turbine converter grid-connected power quality compensation control system 300 according to an embodiment of the present invention includes: a grid-connected point grid state real-time decomposition and evaluation module 310, used to perform real-time decomposition and evaluation of the grid state at the three-phase grid-connected point to obtain the positive-sequence voltage dq component, the negative-sequence voltage dq component, and the voltage imbalance; an adaptive cooperative weight dynamic generation module 320, used to perform adaptive cooperative weight dynamic generation based on the voltage imbalance to obtain adaptive cooperative weights; and a positive and negative sequence current command cooperative generation module 330, used for... Based on adaptive collaborative weighting, positive and negative sequence current commands are collaboratively generated from the active power reference value and the positive sequence voltage dq component to obtain the positive sequence dq axis current reference value and the negative sequence dq axis current reference value; a dual-loop current control module 340 is used to perform dual-loop current control on the positive sequence dq axis current reference value and the negative sequence dq axis current reference value to obtain the dq component of the final voltage modulation signal; a space vector pulse width modulation module 350 is used to perform space vector pulse width modulation on the dq component of the final voltage modulation signal to obtain the three-phase PWM gate drive signal.

[0053] The specific implementation method of the wind turbine converter grid-connected power quality compensation control system of the present invention can be found in the wind turbine converter grid-connected power quality compensation control method of the present invention, and will not be repeated here.

[0054] The wind turbine converter grid-connected power quality compensation control system 300 according to embodiments of the present invention can be implemented in various wireless terminals, such as servers with wind turbine converter grid-connected power quality compensation control algorithms. In one possible implementation, the wind turbine converter grid-connected power quality compensation control system 300 according to embodiments of the present invention can be integrated into the wireless terminal as a software module and / or a hardware module. For example, the wind turbine converter grid-connected power quality compensation control system 300 can be a software module in the operating system of the wireless terminal, or it can be an application developed for the wireless terminal; of course, the wind turbine converter grid-connected power quality compensation control system 300 can also be one of many hardware modules of the wireless terminal.

[0055] Alternatively, in another example, the wind turbine converter grid-connected power quality compensation control system 300 and the wireless terminal can also be separate devices, and the wind turbine converter grid-connected power quality compensation control system 300 can be connected to the wireless terminal via wired and / or wireless networks, and transmit interactive information in accordance with an agreed data format.

[0056] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A wind turbine generator converter grid-connection power quality compensation control method, characterized in that, The wind turbine converter grid-connected power quality compensation control method comprises: The three-phase grid-connected point instantaneous voltage is decomposed and evaluated in real time to obtain positive sequence voltage d-q components, negative sequence voltage d-q components and voltage unbalance degree; Based on the voltage unbalance degree, adaptive collaborative weight is dynamically generated to obtain the adaptive collaborative weight; Based on the adaptive collaborative weight, the active power reference value and the positive sequence voltage d-q component are cooperatively generated to obtain the positive sequence d-q axis current reference value and the negative sequence d-q axis current reference value; The positive sequence d-q axis current reference value and the negative sequence d-q axis current reference value are subjected to double-loop current control to obtain the d-q components of the final voltage modulation signal; The d-q components of the final voltage modulation signal are subjected to space vector pulse width modulation to obtain three-phase PWM gate drive signals.

2. The wind turbine generator variable frequency converter grid- tie power quality compensation control method of claim 1, wherein, The three-phase grid-connected point instantaneous voltage is decomposed and evaluated in real time to obtain positive sequence voltage d-q components, negative sequence voltage d-q components and voltage unbalance degree, comprising: The three-phase grid-connected point instantaneous voltage is Clarke-transformed to obtain voltage components in the Clarke coordinate system; On The positive and negative sequence component separation and phase locking of the voltage component in the coordinate system based on the double second-order generalized integrator are carried out to obtain The positive sequence voltage component in the coordinate system, The negative sequence voltage component in the coordinate system and the grid voltage phase angle; Based on the phase angle of the grid voltage, the positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are calculated. The positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are rotated to the rotating coordinate system to obtain the positive-sequence voltage d-q component and the negative-sequence voltage d-q component. The positive-sequence voltage d-q component and the negative-sequence voltage d-q component are calculated by rotating the positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system to the rotating coordinate system and calculating the unbalance degree.

3. The wind turbine generator variable frequency converter grid- tie power quality compensation control method of claim 2, wherein, Based on the phase angle of the grid voltage, the positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are calculated. The positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are rotated and projected to obtain the positive-sequence voltage d-q component, the negative-sequence voltage d-q component, and the voltage unbalance degree, including: The positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are rotated and projected to obtain the positive-sequence voltage d-q component, the negative-sequence voltage d-q component, and the voltage unbalance degree, including: Based on the grid voltage phase angle, the positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are projected to the rotating coordinate system to obtain the positive-sequence voltage d-q component and the negative-sequence voltage d-q component according to the following formula: The positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are projected to the rotating coordinate system to obtain the positive-sequence voltage d-q component and the negative-sequence voltage d-q component according to the following formula: The positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are projected to the rotating coordinate system to obtain the ； ； wherein, is a negative sequence d-axis voltage, is a negative sequence d-axis voltage, is a negative sequence q-axis voltage, is a positive sequence d-axis voltage, is a positive sequence d-axis voltage, is a positive sequence q-axis voltage, is a grid voltage phase angle at time t, is a grid voltage phase angle at time t, is a positive sequence voltage component in the d-q coordinate system, is a positive sequence voltage component in the d-q coordinate system, is a positive sequence voltage component in the d-q coordinate system, is a positive sequence voltage component in the d-q coordinate system, is a positive sequence voltage component in the d-q coordinate system, is a positive sequence voltage component in the d-q coordinate system, is a positive sequence voltage component in the d-q coordinate system, is a negative sequence voltage component in the d-q coordinate system, is a negative sequence voltage component in the d-q coordinate system, is a negative sequence voltage component in the d-q coordinate system, is a negative sequence voltage component in the d-q coordinate system, is a negative sequence voltage component in the d-q coordinate system, is a negative sequence voltage component in the d-q coordinate system, is a negative sequence voltage component in the d-q coordinate system, is a negative sequence voltage component in the d-q coordinate system.

4. The wind turbine generator variable frequency converter grid- tie power quality compensation control method of claim 3, wherein, Based on the phase angle of the grid voltage, the positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are calculated. The positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are rotated and projected to obtain the positive-sequence voltage d-q component, the negative-sequence voltage d-q component, and the voltage unbalance degree. The positive-sequence voltage component and the negative-sequence voltage component in the stationary coordinate system are rotated and projected to obtain the positive-sequence voltage d-q component, the negative-sequence voltage d-q component, and the voltage unbalance degree. Based on the positive sequence voltage d-q components and the negative sequence voltage d-q components, the voltage unbalance degree is calculated according to the following formula: ； wherein is the voltage unbalance degree.

5. The wind turbine generator variable frequency converter grid- tie power quality compensation control method of claim 1, wherein, Based on the voltage unbalance degree, adaptive collaborative weight is dynamically generated to obtain the adaptive collaborative weight, comprising: Based on the maximum current of the converter and the current amplitude of the grid-side converter, the current margin is calculated; The current margin and the voltage unbalance degree are normalized to obtain the normalized grid support demand factor and the normalized current capacity factor; The normalized grid support demand factor and the normalized current capacity factor are subjected to multi-factor fusion and collaborative weight generation to obtain the adaptive collaborative weight.

6. The wind turbine generator variable frequency converter grid- tie power quality compensation control method of claim 5, wherein, The normalized grid support demand factor and the normalized current capacity factor are subjected to multi-factor fusion and collaborative weight generation to obtain the adaptive collaborative weight, comprising: The normalized grid support demand factor and the normalized current capacity factor are subjected to multi-factor fusion and collaborative weight generation according to the following formula: ； ； wherein, and are base strategy weight coefficients, and are normalized grid support demand factor and normalized current capability factor, respectively, is an adaptive synergy initial weight, is an adaptive synergy weight.

7. The wind turbine generator variable frequency converter grid- tie power quality compensation control method of claim 1, wherein, Based on the adaptive collaborative weight, the active power reference value and the positive sequence voltage d-q component are cooperatively generated to obtain the positive sequence d-q axis current reference value and the negative sequence d-q axis current reference value, comprising: Based on the active power reference value and the reactive power reference value, the positive sequence voltage d-q component is subjected to reference positive sequence current instruction generation based on LVRT strategy and power instruction to obtain the positive sequence d-q axis current reference value; Based on the negative sequence compensation admittance, the negative sequence voltage d-q component is subjected to reference negative sequence current instruction generation of two opposite targets to obtain the negative sequence d-q axis current reference value for supporting the grid and the negative sequence d-q axis current reference value for suppressing torque ripple; Based on the adaptive collaborative weight, the negative sequence d-q axis current reference value for supporting the grid and the negative sequence d-q axis current reference value for suppressing torque ripple are subjected to adaptive weight fusion to obtain the final negative sequence d-q axis current reference value.

8. The wind turbine generator variable frequency converter grid- tie power quality compensation control method of claim 7, wherein, Based on the active power reference value and the reactive power reference value, the positive sequence voltage d-q component is subjected to reference positive sequence current instruction generation based on LVRT strategy and power instruction to obtain the positive sequence d-q axis current reference value, comprising: Based on the LVRT strategy, the active power reference value, the reactive power reference value and the positive sequence voltage d-q component are processed by the following formula to obtain the dynamic reactive power reference value: ； wherein, is a dynamic reactive power reference value, is a reactive power reference value, is a reactive power support factor as specified by grid codes, is a positive sequence d-axis voltage, is a positive sequence q-axis voltage, is a system nominal voltage; Based on the dynamic reactive power reference value and the active power reference value, the positive sequence voltage d-q component is calculated by the following formula to obtain the positive sequence d-q axis current reference value: ； ； wherein, is the active power reference value, is the positive sequence d-axis current reference value, is the positive sequence q-axis current reference value.

9. The wind turbine generator variable frequency converter grid- tie power quality compensation control method of claim 7, wherein, Based on the adaptive cooperative weight, the negative sequence d-q axis current reference value for supporting the power grid and the negative sequence d-q axis current reference value for suppressing torque ripple are adaptively weighted and fused to obtain the final negative sequence d-q axis current reference value, including: Based on the adaptive cooperative weight, the negative sequence d-q axis current reference value for supporting the power grid and the negative sequence d-q axis current reference value for suppressing torque ripple are adaptively weighted and fused by the following formula: ； wherein, and are a negative sequence d-q axis current reference value targeting the support of the power grid and a negative sequence d-q axis current reference value targeting the suppression of torque pulsation, respectively, is an adaptive coordination weight, is the final negative sequence d-q axis current reference value.

10. A wind turbine generator converter grid-tie power quality compensation control system characterized by, The wind turbine converter grid-connected power quality compensation control system comprises: A grid point power grid state real-time decomposition and evaluation module is configured to perform grid point power grid state real-time decomposition and evaluation on the three-phase grid point instantaneous voltage to obtain the positive sequence voltage d-q component, the negative sequence voltage d-q component and the voltage unbalance degree; An adaptive cooperative weight dynamic generation module is configured to perform adaptive cooperative weight dynamic generation based on the voltage unbalance degree to obtain the adaptive cooperative weight; A positive and negative sequence current instruction cooperative generation module is configured to perform positive and negative sequence current instruction cooperative generation on the active power reference value and the positive sequence voltage d-q component based on the adaptive cooperative weight to obtain the positive sequence d-q axis current reference value and the negative sequence d-q axis current reference value; A double-loop current control module is configured to perform double-loop current control on the positive sequence d-q axis current reference value and the negative sequence d-q axis current reference value to obtain the d-q component of the final voltage modulation signal; A space vector pulse width modulation module is configured to perform space vector pulse width modulation on the d-q component of the final voltage modulation signal to obtain the three-phase PWM gate drive signal.

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