Research And Application On Vector Control Systems In Variable Speed And Constant Frequency Wind Power Generation Systems

Wind power generation has become the research focus of all countries along with the great development of the project of wind power generation. Most of double fed wind power generation systems used to adopt the vector control method which oriented along the stator magnetic field direction or stator voltage direction with position sensor, but the installation of position sensors will bring some defects to the system and at the same time decrease the reliability of the system, in order to resolve this problem, this thesis proposed a strategy to control the double fed electric machine based on speed sensorless method.At first, several kinds of variable speed and constant frequency wind power generation systems have been compared, each characteristic of which has been analyzed respectively. And because the aerodynamic property of wind turbines determines the control index of generations and the design of the control loop. Thereat the wind power coefficient and the relationship between pitch angle and tip speed ratio have been analyzed and the approximate formula of the wind power coefficient has been deduced. The control strategies under different wind speed have been analyzed and obtained the optimal tip speed ratio using the simplex algorithm.In addition, to begin analyzing from the steady-state model of the double-fed motor, then analyzed the transient state model, 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 countthe 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 not only realizes the control method but also enhances the interference rejection of the system, it can also filter the deviation produced by inaccuracies of the rotor leakage inductance during the orientation process while enhance system robust performance.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.