Research On High Voltage Ride Through Control Strategy Of Doubly Fed Induction Generator

The idea of wind power construction in China is to build a large base and send out large-scale wind power,so the problem of large-scale wind power grid connection is particularly important.However,when the high voltage ride through capability of wind turbine is insufficient,the fluctuation of grid voltage may lead to frequent off grid accidents.In view of this,this paper takes doubly fed induction generator as the object,the research is carried out from two aspects: voltage surge detection technology and high voltage ride through technology.The main research contents are as follows:(1)The mathematical model of doubly fed wind turbine is constructed,including wind turbine model,doubly fed generator model in d-q coordinate system and converter model.The established model provides the basis for the subsequent control strategy design.(2)A voltage surge detection method is designed,which consists of a phase-locked loop monitoring module,a fast detection module and a modified detection module.After the PLL monitoring module detects the power grid voltage surge fault,it sends out the detection instruction,and the subsequent two modules detect the voltage surge amplitude.The modified detection module can modify the high voltage ride through instruction in the interference environment.This method can provide the basis for the accurate high voltage ride through instruction.(3)From the point of rotor current control,a high voltage ride through control strategy of doubly fed wind turbine based on rotor current feedback compensation is proposed.Based on the precise expression of rotor current,a rotor current feedback compensation controller is designed,which can effectively restrain the fluctuation of rotor current after voltage surge fault and improve the high voltage ride through ability of doubly fed wind turbine.(4)From the point of reactive power control,a high voltage ride through control strategy of doubly fed wind turbine based on reactive power cooperative control is proposed.This strategy considers the reactive power compensation ability of doubly fed wind turbine,makes the rotor side and grid side converter work together,reasonably adjusts the reference value of reactive current of the two converters,ensures enough inductive reactive power output,and the goal of high voltage ride through is achieved.Finally,the simulation model of doubly fed wind turbine is built under Matlab/Simulink.On this basis,the proposed method and control strategy are verified by simulation,and the results show its effectiveness.