Research On Variable Pitch Control And Low Voltage Ride Through Technology Of Doubly-fed Wind Power Generator

Energy,environment is the urgent problems to be solved for the survival and development of mankind today,the development and utilization of renewable energy has become an important part of the sustainable development strategy of all countries in the world.As a kind of clean energy,wind power generation has been paid more and more attention by countries all over the world.In a wind power system,high power variable speed constant frequency doubly-fed wind power generation system has become the mainstream of wind power generation system with low cost,high efficiency and other advantages.In-depth study of doubly-fed wind generation control technology is of great practical significance for wind energy development and wind power industry development.Due to the randomness and suddenness of wind energy,it will have a some influence on the implementation of variable pitch control of wind power generation units.Therefore,the stable output of power and stable operation of wind power generation system are realized through the study of variable pitch controller.When the power grid is unbalanced or voltage drop occurs,the doubly-fed generator will shock,so as to affect the power quality.For the study on variable pitch and low voltage ride through of doubly-fed wind generator,the main work of this paper is as follows:(1)This paper firstly analyzes the basic law of variable pitch from the perspective of wind generator aerodynamics.Due to the characteristics of wind generator such as multivariable and nonlinear,the traditional PID controller is difficult to obtain the ideal control effect in the variable pitch control of wind power generation,so the fuzzy RBF neural network theory and PID are combined to design the variable pitch control.The superiority of the variable pitch control is demonstrated by building the overall model on MATLAB/Simulink and conducting simulation.(2)When the grid voltage is unbalanced,the traditional vector control strategycurrent control loop PI regulation cannot restore the voltage balance quickly and effectively.Firstly,the positive and negative sequence characteristics of doubly-fed wind generator and the influence of voltage imbalance on the network side frequency converter,machine side frequency converter and dc bus of doubly-fed wind generator are analyzed.The model was built on MATLAB/Simulink,and the vector control strategy of adding the trap wave was verified by simulation to effectively suppress the dc bus voltage and rotor current harmonics.(3)When voltage sags occur through the grid,the transient analysis of doubly-fed wind generator is based on an ac-dc multiplexed Crowbar low voltage ride through strategy.Maxwell and Simplorer are used for modeling and simulation,and the feasibility of the scheme is verified by simulation.