Study Of The Control Strategy For The Doubly Fed Wind Energy Generation System During Network Unbalanced

With the accelerated development of the society, the consumption of energy is also growing everyday. The rapid consumption of fossil energy makes more crises, and the development of clean energy is necessary in crunch time. Wind-generated electricity is concerned because of its abundance and cleaning, so it obtained development fast. The doubly fed generator is widely used in wind power generation systems because its low manufacturing cost, stable operation and simple control. In this paper, the converter of the doubly fed wind power generation system is studied.Firstly, the implementation methods of the traditional vector control(VC) and direct power control based on sliding mode control(SMC-DPC) are introduced in grid side converter(GSC) under grid voltage balanced and unbalanced. The essential difference between them is given by comparing. The traditional power feedback is replaced by the fundamental frequency component of the directly output to reduce the unstability of the DC voltage, so the model of the GSC is imporved. With the improving of the model the GSC is controled more accurated.The model of the rotor side converter(RSC) is also introduced with different grid conditions. The VC and SMC-DPC of the RSC are described and designed detailed. The impact of doubly fed induction generator to the control under unbalanced grid conditions is studied. When the grid voltage mutated instantaneously, the motor will make a series of response. The SMC-DPC and the transient control are combined to improve the problems of the power fuctuation and electrical torque oscillating in a long time. The method proposed is analysed theoretically and verificated by simulation, the rapidity and stability of the transition are realized.Finally, the control mothods used in this paper are verified by MATLAB/Simulink. Through the experimental platform built, a part of control strategy are verified by experiment. The conclusion of the simulaiton and experiment results verify the control methods in this paper is effective and feasible.