The Power Control Of Doubly Fed Induction Generator And Its Research On Power Grid Fault

Today,the development of social economy is rapidly.The demands and requirements of energy have developed into the development of clean and renewable energy from the traditional fossil energy gradually.Because of environmental protection and the richness of its own,the wind energy resources have been developed vigorously.After entering in twenty-first Century,wind power ushered in the development of the trend,its installed capacity is increasing.As a result,people's demand for wind power grid has become more stringent.Because of the high efficiency of the double fed motor and the small capacity of the converter,and its ease of control.The DFIG is generally used as the generator in wind power system.However,the wind turbine is very sensitive to the fault of the power grid.If the system is damaged or even removed from the grid,it will bring great losses to the system itself and the national economy.In this paper,the double fed motor(DFIG)is the research object.Based on the analysis of the relevant model,the power output control of the rotor side converter is discussed,and the control of DFIG is also studied in the case of symmetrical drop fault.First of all,this paper simply introduces the basic operation principle ofdoubly fed wind power system,and deduces the mathematical model of DFIG.The model of three phase static coordinate system is transformed into two phase stationary and two phase synchronous rotating coordinate system.On those basis,the vector control and direct power control strategy based on DFIG rotor side converter are studied respectively.At the same time,the simulation results on the MATLAB simulation platform are analyzed and compared.In this paper,the transient response process of DFIG under the condition of symmetrical voltage drop is discussed.The root cause of the rotor side damage is the stator flux DC component.According to the analysis results,the low voltage fault ride through control technology based on DFIG rotor side converter is studied.On the basis of vector control,through the compensation of the rotor current command,the DC flux attenuation can be effectively accelerated,and the over current of the rotor can be restrained.so that the DFIG can be used to improve the capability of the network.Through the MATLAB simulation platform,the simulation model of the control system is built to verify the correctness of the control algorithm.An experimental platform based on 2.2k W double fed motor is set up.The experimental platform is composed of sampling circuit,processing circuit,DSP control unit,motor drive and so on.The software control program of each part of the system is designed.Based on the combination of software and hardware,some experimental verification of the theoretical analysis is carried out through the experimental platform.Finally,the experimental results are given toprove the correctness of the theory.