Research On Low Voltage Ride Through Control Strategy Of Doubly-Fed Wind Power Generator

Wind energy resource is everywhere and the reserves of amazing energy,and wind energy in the use of human life is also more and more widely,especially in the field of wind power is more prominent.In recent years,with the installed capacity of wind turbine is constantly increasing,especially the research on the low voltage ride through the performance of double fed wind generator.It plays a vital role in the development of China's wind power,and it is urgent to solve the problem of low voltage ride through.In this thesis,the doubly-fed wind power generator based on double PWM is taken as the research object,and the method of improving the performance of low voltage ride through is analyzed.Firstly,on the basis of the mathematical model of the doubly fed motor,the grid side PWM and the rotor side PWM are studied.The grid side PWM ensures the constant output voltage of the DC side and input current of the AC side is nearly sinusoidal,and it has good dynamic performance.The rotor side PWM ensures the effective control of the speed and active power,and the output of reactive power guarantee the stable operation of the grid.Secondly,the rotor side PWM of the traditional PI control is improved,and the fuzzy controller is used to replace the speed PI regulator,which constitutes the rotor side PWM of the active power fuzzy control.By building the simulation model in MATLAB/Simulink environment,the fuzzy control method and PI control method are compared.Finally,two kinds of Crowbar protection circuit in active and passive analysis,selection of active Crowbar protection circuit is composed of diode bridge rectifier and thyristor,and optimize its resistance and switching time.In reactive power compensation,static synchronous compensator using direct parallel DC battery(STATCOM/BESS),and it is based on the reactive power compensator with energy storage technology.A composite control strategy is proposed,which combines the active Crowbar protection circuit with STATCOM/BESS compensation on the basis of fuzzy control doubly fed wind power generator to improve the low voltage crossing ability.In the case of three-phase symmetrical fault,Simulation results of the unprotected simulation results with the composite control strategy are presented.The influence of the method on the low voltage ride through capability can be defined,which provides a theoretical basis and support for the correctness of the method.