Wind power plant frequency support method and system based on complex vector feedforward decoupling control

Abstract

The invention relates to a complex vector feedforward decoupling control wind power plant frequency support method and system, and the method is characterized in that the method comprises the steps: obtaining a wind speed and a pitch angle, and constructing a wind turbine model; according to the direct-axis current, the quadrature-axis current and the electromagnetic torque, constructing a permanent magnet direct-driven generator model; constructing a converter model according to the direct-current side capacitor voltage, the capacitor current, the inductive current, the direct-axis current and the quadrature-axis current; by controlling the pitch angle, the wind energy utilization coefficient is changed, and maximum power tracking control on the fan side is achieved; the inertia synchronous control of the converter of the wind turbine generator is realized through the linkage of the per unit value of the frequency of the power grid and the direct-current capacitor voltage of the converter; and designing voltage feed-forward decoupling control and improving the voltage feed-forward decoupling control to obtain a current loop decoupling control strategy of a complex vector. Compared with the prior art, the inertia synchronous control mode of the wind turbine generator is improved, so that the wind turbine generator has higher frequency supporting capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wind power generation systems, in particular to a wind farm frequency support method and system based on complex vector feedforward decoupling control. BACKGROUND

[0002] With the increasing proportion of new energy installed capacity and power generation, the overall inertia of the system decreases, which easily causes frequency fluctuations. The sudden increase in the proportion of new energy will lead to the continuous decline of the strength of the power grid, bringing challenges to the stable operation of the grid-connected wind turbine. The rotor speed of the grid-connected wind turbine is decoupled from the grid and cannot respond to the change in grid frequency in time. It needs to rely on the phase angle of the frequency of the phase-locked loop to follow the AC grid voltage to realize synchronization with the grid, which is difficult to operate stably in a weak grid and does not have the ability to support the grid. The control of the grid-connected wind turbine helps to improve the interaction stability of the converter and the weak grid, and has good application prospects in the high-proportion wind power grid-connected scene. Among them, the inertia synchronous control using the DC capacitor energy to simulate the rotor characteristics of the synchronous machine is a relatively novel grid-connected control strategy. This method can realize the self-synchronization function of the converter only by using the DC capacitor voltage signal. Compared with the traditional grid-connected converter, the control structure is changed less and the modification cost is low.

[0003] However, the traditional inertia synchronous control has insufficient active frequency support capability. The patent with publication number CN120433303B discloses a wind-wave complementary grid-connected optimization method based on VSG technology and feedforward control. A laser wind measuring radar and a laser wave measuring radar are installed on the floating wind turbine platform of the floating wind-wave coupled cooperative power generation system. A nonlinear mathematical model of the power generation of the floating wind turbine and the wave energy generator is constructed. A virtual synchronous control strategy of the inverter is designed, virtual inertia and virtual damping coefficient are introduced, and the inverter is used to realize primary frequency regulation, voltage / frequency regulation and damping oscillation suppression function. However, the feedforward control technology used is the traditional voltage feedforward decoupling control method, which has poor robustness and precision for converter control, and slow feedback speed. SUMMARY

[0004] To solve the problems in the prior art, the present application provides a wind farm active frequency support capability improvement method and system based on complex vector feedforward decoupling control. While being able to realize grid operation, the traditional inertia synchronous control structure is improved. The original traditional current loop decoupling link is replaced by a new type of complex vector current decoupling control, which improves the stability of the current controller and makes the active frequency support capability of the wind turbine stronger, providing assistance for the safety protection of the system frequency.

[0005] The present application adopts the following technical solutions: A wind farm frequency support method based on complex vector feedforward decoupling control, the method comprising the steps of: Step one: obtaining wind speed and pitch angle, to calculate wind energy utilization coefficient, tip speed ratio and build wind turbine model; according to the direct axis current and the quadrature axis current, electromagnetic torque to build permanent magnet direct drive generator model; according to the DC side capacitor voltage, capacitor current and inductance current and the direct axis current and the quadrature axis current to build converter model; Step two: according to the wind turbine model and the wind speed, pitch angle obtained by the control of pitch angle, change wind energy utilization coefficient and realize the maximum power tracking control of fan side, and get the DC current value; obtain the DC side capacitor voltage, through the linkage of grid frequency standard value and the DC side capacitor voltage, calculate the correction value of DC current and combine with the DC current value, get the real-time direct axis current; Step three: according to the permanent magnet direct drive generator model and converter model to establish the controlled object model, through eliminating current coupling term in the controlled object model, design voltage feedforward decoupling controller model; through the improvement of the voltage feedforward decoupling controller model, get the current loop decoupling controller model of complex vector; the current loop decoupling controller model of complex vector receives the real-time direct axis current, outputs voltage instruction and drives the converter to support the grid power, realizes the inertia synchronous control to the grid.

[0006] Further, the process of building wind turbine model specifically includes: The airflow power is obtained from the fluid mechanics formula: In the formula, The value of air density is 1.293 kg / m3 under the condition of atmospheric temperature of 20°C. The swept area of fan blade is The wind speed is The airflow power is converted into mechanical power by wind turbine, and the expression of power conversion process is: In the formula, The wind energy utilization coefficient is The tip speed ratio is The tip speed ratio is defined as the ratio of tip speed to wind speed, which is expressed as: In the formula, The angular velocity of blade is The radius of blade is For the wind turbine that can adjust the pitch angle, Approximately expressed as: In the formula, ​For the blade pitch angle, For the intermediate variable is expressed as: .

[0007] Further, the process of building a permanent magnet direct drive generator model specifically includes: The voltage equation of the permanent magnet synchronous generator in the d-q coordinate system is: The flux linkage equation in the d-q coordinate system is: The electromagnetic torque equation is: In the formula: For the stator resistance, For the direct-axis and quadrature-axis flux linkage, For the direct-axis current and quadrature-axis current, For the electromagnetic torque, For the electrical angular velocity, For the pole pair number of the motor.

[0008] Further, the process of building a permanent magnet direct drive converter model specifically includes: the converter is composed of a PWM rectifier and a PWM inverter; according to the DC side capacitor voltage and capacitor current, inductance current and the direct-axis current and quadrature-axis current, the mathematical model of the PWM rectifier in the dq coordinate system is built: The power output by the PWM rectifier is defined as: The power absorbed by the PWM inverter is defined as: In the formula, Indicates the load current on the DC side, Indicates the filter inductance on the AC side of the rectifier, Indicates the component of the switching function of the rectifier bridge arm on the d-axis, Indicates the component of the switching function of the rectifier bridge arm on the q-axis.

[0009] Further, the implementation of the maximum power tracking control of the fan side specifically includes: when the pitch angle changes, the maximum value of the wind energy utilization coefficient also changes; when the pitch angle is 0, the maximum value of the wind energy utilization coefficient is the maximum value of the wind energy utilization coefficient under the fan; when the current wind speed does not exceed the rated wind speed of the fan, the pitch angle can be 0, so that the fan can capture the maximum available power under the current wind speed; when the wind speed exceeds the rated wind speed of the fan, the pitch angle is adjusted by the pitch mechanism to change the pitch angle to reduce the wind power converted by the fan, so that the wind turbine generator can still operate within its rated power range; in the actual application scene, the wind energy utilization coefficient of the fan is between 0.2-0.5.

[0010] Further, the relationship between the grid frequency per unit and the DC side capacitor voltage per unit is: The DC bus voltage equation of the permanent magnet direct drive wind turbine generator is established: In the formula, is the inertia time constant of the DC side capacitor; is the per unit value of the DC side capacitor voltage; is the per unit value of the DC voltage in the steady state; is the per unit value of the machine side converter output power; is the per unit value of the grid side converter output power; which can be expressed as: In the formula, is the capacitance value; is the reference value of the DC voltage; is the rated power of the wind turbine generator. The grid side output power of the permanent magnet direct drive wind turbine generator is expressed as: The rotor equation of the PMSG is: In the formula, is the per unit value of the PMSG mechanical power; is the per unit value of the electromagnetic power; is the per unit value of the speed of the motor rotor; is the rotor inertia time constant; The electromagnetic power of the PMSG is expressed as: The relationship between the grid frequency per unit and the DC side capacitor voltage per unit is: wherein, is the unit of the grid-side converter modulation voltage amplitude; is the unit of the grid voltage amplitude; is the unit of the grid-side converter reactance to the grid point; is the phase angle of the grid-side output voltage leading the grid voltage, represents the public angle sine value, represents the stator flux amplitude.

[0011] Further, the construction process of the voltage feedforward decoupling controller model specifically includes: The current loop adopts the traditional structure, and the model of the controlled object part is as follows: wherein, and are the voltage and current in the form of complex vectors respectively. is the rotor flux; is the electromagnetic speed; The model of the controller part is as follows: The above formula is obtained by eliminating the back electromotive force term from the minus: When , the above formula can be transformed into: wherein, is the synchronous inductance of the surface-mounted permanent magnet synchronous motor, is the stator resistance.

[0012] Further, the construction process of the current loop decoupling controller model of the complex vector specifically includes: The model of the controlled object part is as follows: wherein, and are the voltage and current in the form of complex vectors respectively. is the rotor flux; is the electromagnetic speed; The model of the controller part is as follows: The above formula is obtained by eliminating the back electromotive force term from the minus: When , the above formula can be transformed into: The position of the zero point varies with the speed, when The above formula can be converted into: In the formula is a proportional gain, is an integral gain, is a voltage feedback gain, and are voltage and current reference values in the form of complex vectors respectively, is an additional feedback gain, and are the actual and reference values of the voltage of the d-axis and q-axis respectively.

[0013] Further, the method further comprises: The complex vector current loop decoupling control strategy is verified by using a simulink simulation, a frequency change curve under disturbance of an alternating current system is obtained, and the feasibility of the complex vector current loop decoupling control strategy is analyzed and verified by using the change curve.

[0014] The application also provides a wind farm frequency support system adopting the complex vector feedforward decoupling control method. The system architecture building module is used to establish a wind power generation system based on a direct-drive wind turbine generator; The basic control strategy configuration module is used to realize maximum power tracking control on the wind turbine side and inertia synchronous control of the wind turbine converter; The control strategy optimization design module is used to establish a complex vector current loop decoupling control strategy; The strategy verification and performance improvement module is used to verify the complex vector current loop decoupling control strategy, obtain a frequency change curve under disturbance of an alternating current system, and analyze and verify the feasibility of the complex vector current loop decoupling control strategy by using the change curve.

[0015] Compared with the prior art, the application has the following advantages: (1) The application obtains a current loop decoupling control strategy based on a complex vector by improving the traditional voltage feedforward decoupling control method; compared with the traditional voltage feedforward decoupling control method, the system effectively and independently controls the active power and the reactive power output by the converter by using the strategy, realizes complete cancellation of zero-pole by introducing a virtual axis zero point that changes with the speed, essentially improves the dynamic coupling phenomenon of the current, effectively eliminates the coupling interference in the system, such as electromagnetic coupling and parameter disturbance, etc., enables the converter to respond more quickly and accurately to the change of the grid frequency, enhances the dynamic synchronization ability of the wind turbine and the grid, and reduces the frequency fluctuation in the transient process.

[0016] (2) The application verifies the complex vector current loop decoupling control strategy by using the simulink simulation, obtains the frequency change curve under the disturbance of the AC system, and verifies the feasibility of the complex vector current loop decoupling control strategy: when the AC system is disturbed, such as load mutation, fault, etc., the optimized control strategy can make the wind turbine actively provide inertia support to the grid by improving the “lowest frequency point” and reducing the “maximum frequency change rate”, delay the frequency drop speed, and raise the frequency stability threshold, thereby solving the problem of grid frequency stability caused by the lack of inertia of the traditional wind turbine.

[0017] (3) The application retains the maximum power tracking control function on the wind turbine side to ensure efficient use of wind energy, and realizes the coordination of “efficient power generation” and “active support of grid frequency” by using the hierarchical optimization control logic: basic control first, then decoupling optimization control, thereby breaking through the trade-off problem between economy and grid friendliness of the traditional wind turbine, and improving the comprehensive performance of the overall system.

[0018] (4) The application introduces a DC capacitor in the system, simulates the rotor characteristics of a synchronous machine by using the energy of the DC capacitor, realizes the self-synchronization function of the converter only by the DC capacitor voltage signal, and has smaller control structure changes and lower modification cost compared with the traditional grid-connected converter. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 a flow chart of a complex vector feedforward decoupling control wind farm frequency support method provided in the embodiment of the application; Figure 2 a permanent magnet direct drive wind turbine structure diagram used in a simulation experiment provided in the embodiment of the application; Figure 3 a frequency change curve diagram after inertia synchronization control based on complex vector feedforward decoupling provided in the embodiment of the application; Figure 4 a frequency change comparison curve diagram before and after inertia synchronization control based on complex vector feedforward decoupling provided in the embodiment of the application; Figure 5 A structural principle block diagram of a complex vector feedforward decoupling control wind farm frequency support system provided in Embodiment 2 of the present application. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0022] Embodiment 1 As shown in Figure 1 , the embodiments of the present application provide a complex vector feedforward decoupling control wind farm frequency support method, comprising the following steps: S1: obtaining wind speed and pitch angle, to calculate wind energy utilization coefficient, tip speed ratio and build wind turbine model; building permanent magnet direct drive generator model according to direct axis current and quadrature axis current, electromagnetic torque; building converter model according to DC side capacitor voltage, capacitor current and inductance current and the direct axis current and the quadrature axis current; In the embodiments, specifically: Building a wind power generation system based on direct drive wind turbine generator; The structure of wind power generation, transmission and grid connection of the permanent magnet direct drive wind turbine generator is as shown in Figure 2 , which is composed of devices from left to right, such as wind turbine, machine side converter, DC capacitor, permanent magnet synchronous generator and grid side converter.

[0023] Wind turbine model: The airflow power is obtained from the fluid mechanics formula: In the formula, is air density, under the condition that the atmospheric temperature is 20°C, its value =1.293kg / m3; is the swept area of the fan blade, is the wind speed.

[0024] The power conversion process from wind energy to mechanical power is expressed as: where, is the wind energy utilization coefficient.

[0025] The tip speed ratio is defined as the ratio of the tip speed to the wind speed and is expressed as: where, is the angular velocity of the blade, is the radius of the blade.

[0026] For wind turbines with adjustable pitch angle, is approximately expressed as: where, is the pitch angle of the blade, is an intermediate variable expressed as: Permanent magnet direct drive generator model: The voltage equation of the permanent magnet synchronous generator in the d-q coordinate system is: The flux linkage equation in the d-q coordinate system is: The electromagnetic torque equation is: where, is the stator resistance, is the direct-axis and quadrature-axis flux linkage, is the direct-axis and quadrature-axis current, is the electromagnetic torque, is the electrical angular velocity, is the number of pole pairs of the motor.

[0027] Converter model: The mathematical model of the PWM rectifier in the dq coordinate system is: where, represents the load current on the DC side, represents the filter inductance on the AC side of the rectifier, represents the component of the switching function of the rectifier bridge arm on the d-axis, represents the component of the switching function of the rectifier bridge arm on the q-axis. ​

[0028] The back-to-back converter is composed of two identical two-level voltage source PWM converters, and the rectifier and the inverter have the same structure, only the positive direction is different.

[0029] The power output from the machine side is: The power absorbed by the grid side is: S2: According to the wind turbine model and the obtained wind speed and pitch angle, the wind energy utilization coefficient is changed and the maximum power tracking control of the wind turbine side is realized by controlling the pitch angle, and the direct current value is obtained; the direct current capacitor voltage is obtained, the direct current correction value is calculated through the linkage of the grid frequency reference value and the direct current capacitor voltage, and the real-time direct-axis current is obtained by combining the direct current value; In this embodiment, specifically: The maximum power tracking control is adopted on the wind turbine side, and the inertia synchronous control strategy is adopted for the generator converter. In a preferred but non-limiting embodiment, the control strategy of the wind turbine generator system adopts maximum power tracking control and inertia synchronous control.

[0030] The established wind turbine maximum power tracking control has the following method: Because is the tip speed ratio and the pitch angle , when is different, the function relationship curve between the three variables can be drawn, when the pitch angle of the wind turbine changes, the maximum value of the wind energy utilization coefficient also changes. When =0, the maximum value of the wind energy utilization coefficient is the maximum value of the wind energy utilization coefficient of the wind turbine. In actual application scenarios, the wind energy utilization coefficient of the wind turbine is between 0.2-0.5. When the current wind speed does not exceed the maximum operating wind speed of the wind turbine, the pitch angle β=0 can be set, so that the wind turbine can capture the maximum available power at the current wind speed; when the current wind speed exceeds the rated wind speed, the pitch angle needs to be adjusted by the pitch mechanism to change the pitch angle value to reduce the wind power converted by the wind turbine, so that the wind turbine generator system can still operate within its rated range.

[0031] The linkage between the grid frequency reference value and the converter direct current capacitor voltage in the established inertia synchronous control of the wind turbine generator converter has the following method: The direct current bus voltage equation of the permanent magnet direct drive wind turbine generator is: In the formula, is the inertia time constant of the DC side capacitor; is the nominal value of the DC side capacitor voltage; is the nominal value of the DC voltage in steady state; is the nominal value of the machine side converter output power; is the nominal value of the grid side converter output power.

[0032] may be expressed as: where, is the capacitance value; is the reference value of the DC side voltage; is the rated power of the wind turbine. The grid side output power of the permanent magnet direct drive wind turbine may be expressed as: where, is the nominal value of the grid side converter modulation voltage amplitude; is the nominal value of the grid voltage amplitude; is the nominal value of the grid side converter to grid point reactance; is the grid side output voltage leading grid voltage phase angle.

[0033] The rotor equation of the PMSG is: where, is the nominal value of the PMSG mechanical power; is the nominal value of the electromagnetic power; is the nominal value of the rotor speed; is the rotor inertia time constant.

[0034] The electromagnetic power Pe of the PMSG is expressed as: where represents the cosine of the public angle, represents the amplitude of the stator flux linkage.

[0035] It is found by comparing the above formula that the mathematical expression of the DC bus voltage has a certain similarity with the dynamic equation of the synchronous generator speed The grid side converter output voltage angular frequency and the DC side capacitor voltage nominal value may be expressed as the following relationship: S3: A controlled object model is established according to the permanent magnet direct drive generator model and the converter model, a voltage feedforward decoupling controller model is designed by eliminating the current coupling term in the controlled object model, and a complex vector current loop decoupling controller model is obtained by improving the voltage feedforward decoupling controller model; the complex vector current loop decoupling controller model receives the real-time direct-axis current, outputs a voltage instruction, and drives the converter to support the grid power, thereby realizing inertia synchronous control of the grid.

[0036] Specifically, in the embodiment, the following is performed: A direct-drive permanent magnet wind turbine generator side converter inertia synchronous control strategy based on complex vector feedforward decoupling is established: The construction process of the voltage feedforward decoupling controller model is as follows: The current loop adopts a traditional structure, and the model of the controlled object part is as follows: In the formula, and are the voltage and current in the form of complex vectors, respectively. is the rotor flux, is the electromagnetic speed, is the synchronous inductance of the surface-mounted permanent magnet synchronous motor, is the stator resistance.

[0037] The model of the controller part is as follows: In the formula, is the proportional gain, is the integral gain, is the voltage feedback gain, and are the voltage and current reference values in the form of complex vectors, respectively, is an additional feedback gain.

[0038] The above formula is obtained by eliminating the back electromotive force term: In the formula, and are the actual values and reference values of the d-axis and q-axis voltages, respectively When is taken, the above formula can be changed to: When the voltage feedforward decoupling control is adopted, the controller has only one zero point, but as the output speed increases, the zero and pole points can no longer be cancelled, and the stability of the current controller will also decrease.

[0039] The construction process of the current loop decoupling controller model of the complex vector is as follows: The model of the controlled object part is as follows: In the formula: and are the voltage and current in the form of complex vector respectively. is the rotor flux; is the electromagnetic speed.

[0040] The model of the controller part is as follows: The above formula is obtained by eliminating the back electromotive force term: Taking , the above formula can be changed into: The position of the zero point changes with the speed, and when , the above formula can be changed into: In this control mode, complete cancellation of the zero pole can be achieved at any time.

[0041] Specifically, in the embodiment, the control strategy is verified by using the simulink simulation, the frequency change curve under the disturbance of the alternating current system is obtained, the lowest point of the frequency and the maximum change rate of the frequency are improved, and thus the active frequency support capability of the wind turbine generator is improved.

[0042] In a preferred but non-limiting embodiment, the effectiveness of the control strategy is verified by using the simulink simulation tool in step S4.

[0043] The effectiveness of the wind farm active frequency support capability improvement method based on the complex vector feedforward decoupling control provided by the present application is verified by specific implementation data.

[0044] The frequency fluctuation of the wind turbine generator under the disturbance by using the method is simulated, the influence of the present application on the lowest point of the frequency and the frequency change rate relative to the traditional method is observed, the active frequency support capability of the wind turbine generator is improved, and the data of the embodiment are as follows: A permanent magnet direct drive wind turbine system is built based on the Matlab / Simulink simulation platform to verify the effectiveness of the wind farm active frequency support capability improvement method based on the complex vector feedforward decoupling control provided by the present application. As Figure 3As shown, the system load surge 0.3MW disturbance, the system frequency first in a short time has a small amplitude of 0.35Hz drop, and then faster to 50Hz, the whole process, the frequency is always in the safe range of 49.5Hz~50.2Hz. As the most important part of the whole control link, improving the dynamic performance of the current loop can make the control effect better, compared with the voltage feedforward decoupling current loop controller, the complex vector decoupling current loop controller can improve the speed of current tracking, and reduce the delay of current tracking. Compared with the control effect of traditional voltage feedforward control and inertia synchronous control under the control of complex vector-based current decoupling, as shown in Figure 4 In this paper, by improving the current loop, the original frequency minimum point is increased from 49.53Hz to 49.62Hz, and the frequency maximum change rate is reduced from 1.501Hz / s to 1.226Hz / s compared with the traditional control, which effectively improves the frequency support ability of inertia synchronous control, so that the wind turbine can better participate in the system frequency regulation.

[0045] The beneficial effects of the present application are that, compared with the prior art: The present application optimizes the inertia synchronous control strategy of the machine side converter by the "complex vector feedforward decoupling" technology, effectively eliminates the internal coupling interference of the system (such as electromagnetic coupling, parameter disturbance, etc.), so that the converter can respond to the grid frequency change more quickly and accurately, enhance the dynamic synchronization ability of the wind turbine and the grid, and reduce the frequency fluctuation in the transient process.

[0046] 2、The present application optimizes the control strategy by improving the "frequency minimum point" and reducing the "frequency maximum change rate", so that the wind turbine can actively provide inertia support to the grid, delay the frequency drop speed and lift the frequency stability threshold, solve the problem of grid frequency stability caused by the lack of inertia of traditional wind turbine.

[0047] 3、The present application retains "maximum power tracking control" on the fan side to ensure efficient use of wind energy, and realizes the coordination of "efficient power generation" and "active support of grid frequency" through the hierarchical optimization control logic (basic control→decoupling optimization control), breaks through the trade-off problem between economy and grid friendliness of traditional wind turbine, and improves the comprehensive performance of the whole system.

[0048] 4, The application verifies the proposed control strategy by using simulink simulation, obtains the frequency change curve under the disturbance of the alternating current system, improves the minimum point of the frequency and the maximum change rate of the frequency, and thus improves the active frequency support capability of the wind turbine generator set. The application can realize the network type control, and also improves the frequency response characteristic of the wind turbine generator set under the inertia synchronous control mode, improves the minimum point of the frequency when the same disturbance occurs, and reduces the maximum change rate of the frequency under the disturbance, so that the wind turbine generator set has stronger active frequency support capability.

[0049] The embodiment of the application provides a direct-drive permanent magnet wind turbine generator set converter inertia synchronous control strategy based on complex vector feedforward decoupling.

[0050] Embodiment two: As Figure 5 shown, the embodiment of the application provides a wind farm active frequency support capability improvement system based on complex vector feedforward decoupling control, which is used to realize the steps of the method in the above embodiment one, and specifically includes: A system architecture building module is used to build a wind power generation system based on a direct-drive wind turbine generator set. A basic control strategy configuration module is used to realize wind turbine maximum power tracking control and generator converter inertia synchronous control strategy. A control strategy optimization design module is used to establish a direct-drive permanent magnet wind turbine generator set side converter inertia synchronous control strategy based on complex vector feedforward decoupling. A strategy verification and performance improvement module is used to verify the proposed control strategy, obtain the frequency change curve under the disturbance of the alternating current system, improve the minimum point of the frequency and the maximum change rate of the frequency, and thus improve the active frequency support capability of the wind turbine generator set.

[0051] The established modules include maximum power tracking control, inertia synchronous control, and complex vector-based current loop decoupling control.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the application and not to limit it, although the application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the application can be modified or replaced, without departing from the spirit and scope of the application, any modification or equivalent replacement, which should be covered in the protection scope of the claims of the application.

Claims

1. A wind farm frequency support method for complex vector feedforward decoupled control, characterized in that, include: Step 1: Obtain wind speed and blade pitch angle to calculate wind energy utilization coefficient, tip speed ratio and build wind turbine model; A permanent magnet direct-drive generator model is constructed based on the direct-axis current, quadrature-axis current, and electromagnetic torque; a converter model is constructed based on the DC-side capacitor voltage, capacitor current, inductor current, and the aforementioned direct-axis current and quadrature-axis current. Step 2: Based on the wind turbine model and the obtained wind speed and pitch angle, the wind energy utilization coefficient is changed by controlling the pitch angle, and the maximum power point tracking control on the wind turbine side is achieved, and the DC current value is obtained; the DC side capacitor voltage is obtained, and the correction value of the DC current is calculated by linking the grid frequency per unit value with the DC side capacitor voltage, and combined with the DC current value to obtain the real-time direct-axis current. Step 3: Based on the permanent magnet direct-drive generator model and the converter model, establish the controlled object model. By eliminating current coupling terms in the controlled object model, design a voltage feedforward decoupling controller model. By improving the voltage feedforward decoupling controller model, obtain a complex vector current loop decoupling controller model. The complex vector current loop decoupling controller model receives the real-time direct-axis current, outputs voltage commands, and drives the converter to support the grid power, thereby achieving inertial synchronous control of the grid.

2. The wind farm frequency support method for complex vector feedforward decoupling control according to claim 1, characterized in that, The process of constructing the wind turbine model specifically includes: The airflow power is obtained from the fluid dynamics formula: In the formula, The density of air, at an atmospheric temperature of 20°C, is... =1.293kg / m3; The swept area of ​​the wind turbine blades; Wind speed; The wind turbine converts airflow power into mechanical power; the expression for this power conversion process is: In the formula, Wind energy utilization coefficient; When the wind turbine blades rotate, the tip speed ratio Defined as the ratio of blade tip rotation speed to wind speed, expressed as: In the formula, The blade angular velocity, Where is the blade radius; For wind turbines with adjustable pitch angle, Approximately expressed as: In the formula, The blade pitch angle, The intermediate variable is represented as: 。 3. The wind farm frequency support method for complex vector feedforward decoupling control according to claim 1, characterized in that, The process of constructing the permanent magnet direct-drive generator model specifically includes: The voltage equation of a permanent magnet synchronous generator in the dq coordinate system is: The flux linkage equation in the dq coordinate system is: The electromagnetic torque equation is: In the formula: For stator resistance, For direct-axis and quadrature-axis magnetic flux linkages, These are the direct-axis current and the quadrature-axis current. For electromagnetic torque, Electric angular velocity, This represents the number of pole pairs of the motor.

4. The wind farm frequency support method for complex vector feedforward decoupling control according to claim 1, characterized in that, The process of constructing the permanent magnet direct-drive converter model specifically includes: the converter consists of a PWM rectifier and a PWM inverter; based on the DC-side capacitor voltage and current, inductor current, direct-axis current, and quadrature-axis current, a mathematical model of the PWM rectifier in the dq coordinate system is constructed: Define the output power of the PWM rectifier as: Define the power absorbed by the PWM inverter as: In the formula, This represents the load current on the DC side. This represents the filter inductance on the AC side of the rectifier. This represents the d-axis component of the switching function of the rectifier bridge arm. This represents the q-axis component of the switching function of the rectifier bridge arm.

5. The wind farm frequency support method for complex vector feedforward decoupling control according to claim 1, characterized in that, The implementation of maximum power point tracking control on the wind turbine side specifically includes: when the pitch angle changes, the maximum value of the wind energy utilization coefficient also changes accordingly; when the pitch angle is 0, the maximum value of the wind energy utilization coefficient is the maximum value of the wind energy utilization coefficient under that wind turbine; when the current wind speed does not exceed the rated wind speed of the wind turbine, the pitch angle can be set to 0, so that the wind turbine can capture the maximum usable power under the current wind speed; when the wind speed exceeds the rated wind speed of the wind turbine, the pitch angle is adjusted by the pitch mechanism to change the pitch angle and reduce the wind power converted by the wind turbine, so that the wind turbine can still operate within its rated power range; in actual application scenarios, the wind energy utilization coefficient of the wind turbine is between 0.2 and 0.

5.

6. The wind farm frequency support method for complex vector feedforward decoupling control according to claim 1, characterized in that, The linkage between the per-unit value of the power grid frequency and the DC-side capacitor voltage specifically includes: Establish the DC bus voltage equation for a permanent magnet direct-drive wind turbine: In the formula, The inertial time constant of the DC-side capacitor; This represents the per-unit value of the DC-side capacitor voltage; This represents the per-unit value of the DC voltage in steady state. This refers to the per-unit value of the output power of the machine-side converter; This represents the per-unit value of the grid-side converter's output power; It can be represented as: In the formula, This is the capacitance value; This is the reference value for the DC-side voltage; This refers to the rated power of the wind turbine. The grid-side output power of the permanent magnet direct-drive wind turbine. Represented as: The rotor equation for PMSG is: In the formula, This represents the per-unit value of the PMSG mechanical power. This represents the per-unit value of electromagnetic power. This represents the per-unit value of the motor rotor speed; The rotor's inertia time constant; The electromagnetic power of PMSG is expressed as: The per-unit value of the grid frequency is obtained from the DC bus voltage equation and the rotor equation of the PMSG. per-unit value of DC-side capacitor voltage The relationship is: In the formula, This is the per-unit value of the modulation voltage amplitude of the grid-side converter; This is the per-unit value of the grid voltage amplitude; This refers to the per-unit value of the reactance from the grid-side converter to the grid connection point; The grid-side output voltage leads the grid voltage by a phase angle. Represents the sine of the common angle. This indicates the magnitude of the stator flux linkage.

7. The wind farm frequency support method for complex vector feedforward decoupling control according to claim 1, characterized in that, The construction process of the voltage feedforward decoupling controller model specifically includes: The current loop adopts a traditional When structuring, the model of the controlled object is as follows: In the formula: and These are voltage and current in complex vector form, respectively. It is rotor flux linkage; It is the electromagnetic rotation speed; The controller model is as follows: Subtracting the back electromotive force term from the above equation yields: Pick Then, the above formula can be simplified to: In the formula, The synchronous inductor for a surface-mounted permanent magnet synchronous motor. This is the stator resistance.

8. The wind farm frequency support method for complex vector feedforward decoupling control according to claim 1, characterized in that, The construction process of the complex vector current loop decoupling controller model specifically includes: The model for the controlled object is as follows: In the formula: and These are voltage and current in complex vector form, respectively. It is rotor flux linkage; It is the electromagnetic rotation speed; The controller model is as follows: Subtracting the back electromotive force term from the above equation yields: Pick The above equation can be simplified to: The position of zero point changes with velocity, when Then, the above formula can be simplified to: In the formula For proportional gain, For integral gain, For voltage feedback gain, and These are the voltage and current reference values ​​in complex vector form, respectively. For an additional feedback gain, and These are the actual and reference voltage values ​​for the d-axis and q-axis, respectively.

9. The wind farm frequency support method for complex vector feedforward decoupling control according to claim 1, characterized in that, The method further includes: The complex vector current loop decoupling control strategy was verified using Simulink simulation. The frequency change curve under disturbance in the AC system was obtained, and the feasibility of the complex vector current loop decoupling control strategy was analyzed and verified using the change curve.

10. A wind farm frequency support system with complex vector feedforward decoupled control, characterized in that, The system is constructed using a wind farm frequency support method for complex vector feedforward decoupling control as described in any one of claims 1-9, and the system includes: The system architecture building module is used to establish a wind power generation system based on direct-drive wind turbine units; The basic control strategy configuration module is used to realize maximum power point tracking control on the wind turbine side and inertial synchronization control of the wind turbine converter; The control strategy optimization design module is used to establish a complex vector current loop decoupling control strategy; The strategy verification and performance improvement module is used to verify the complex vector current loop decoupling control strategy, obtain the frequency change curve under the disturbance of the AC system, and use the change curve to analyze and verify the feasibility of the complex vector current loop decoupling control strategy.

Images