Study On Grid-Connected Operation Control Of Double Fed Induction Generator

With the rapid development of modern industry, the demand for energy increases significantly, and the useful conventional energy on the earth scarces increasingly. How to realize the sustainable development of energy and ensure the sustainable development of the economy and society has already become a big problem, namely energy strategy, which the various country governments have to solve. Now, electric energy production of all countries mainly relys on thermal power generation. Compared with the thermal power based on coal and oil which consist mainly of carbohydrate, the wind power has the characteristics of no pollution, safety, regeneration, large storage and statistical law. Therefore, all the countries in the world are developing wind power to realize the sustainable development of energy.This paper analyzes the current wind power development condition in the world, espcailly in our country, researches the wind power generation system consisted of doubly-fed induction generator, and studies how to improve the utilization rate of wind power by controlling VSCF and how to improve the power system stablity by adjusting active power and reactive power seperately.In this paper, the operation principle characteristics, mathematical model and the control strategy of VSCF DFIG are analyzed. The main research contents include the control of wind generator under the rated wind speed, keeping the best ratio tip in order to get the maximum wind power, maintaining constant frequency, constant voltage and unit power factor of the output voltage, the control stretagy based on stator flux oriented vector. The vector control system of DFIG is established. The PI regulators of current loop and speed loop are designed. The decoupling relationship between rotor excitation current and voltage and power is realized.This principle algorithm and mathematical model of SVPWM are studied. The control strategies of grid side converter and rotor side converter based on oriented voltage vector control are designed, which can realize the power factor adjustion of grid side converter and rator converter and the control of DC bus voltage.The doubly-fed induction power system simulation model based on the platform of MATLAB/Simulink is built, which includes wind machine, doubly-fed generators (including grid side and rotor side converters), and controllers (including grid side and rotor side converter controllers). The simulation results and theoretical analyses verify the validity of method and the good control performance of the presented doubly-fed generators control system.