Research On Vector Control Systems In Variable Speed And Constant Frequency Wind Turbine

The energy and the environment are the urgent problem which now the human survival and the development must solve. Now various countries have attached important to full use of wind energy. Wind power generation has become the research focus of all countries. This thesis proposed a strategy to control the double fed electric machine based on speed sensorless method.After analyzing several kinds of variable speed and constant frequency wind power generation systems and the aerodynamic property of wind turbines, the relationship of wind power coefficient, pitch angle and tip speed ratio could be worked out. Then the approximate formula of the wind power coefficient has been deduced. According with different control strategy of wind turbines under different wind speeds, the optimal tip speed ratio could be obtained by simplex algorithm.Analyzing the mathematics model of double-fed motor, investigated the decoupling characteristic and deduced the control functions in the coordinates oriented along the stator magnetic field direction. At last, according to fast dynamic response ability of wind turbine is not necessary when wind power generate electricity, a method named rotor induction electric potential orientation method has been proposed .it is a orientation method that orients along the direction of the instantaneous sample of rotor induction electric potential which has passed the low band filter. This method realized the torque control through controlling the instantaneous active power while realized the exciter current control on the stator side through controlling the instantaneous reactive power on the rotor side. Because counting the instantaneous active power need not the integrator to count the magnetic flux, the accumulated error is avoid. At the link of rotor induction electric potential orientation, the FIR digit filter is introduced to filter the induction electric potential signal, not only good amplitude frequency characteristics but also linear phase-frequency characteristic have been obtained. Through analyzing, introduced the filter make the control method have a thick skin to motor parameter. Then the control method could enhance the interference rejection of the system.At last, it has been proved that this method compared with the stable control of the double-fed motor has fast dynamic response, avoids low-frequency concussion, so its control characteristic is intervenient of stator magnetic field orientation method and stable control method, it can also realize the speed-sensorless control method. The reactive power regulation of the double fed electric machine can also be realized through rotor induction electric potential orientation method, of which has simple control structure and great practicability.