Dynamic Analysis, Voltage Control and Experiments on a Self Excited Induction Generator for Wind Power Application

Abstract

Windy areas, waterfalls, reservoirs, high tide locations are extremely helpful for generating clean and economical electrical energy by proper harnessing mechanism. Throughout the globe in last three to four decades generation of electricity out of these renewable sources has created wide interest. Induction generators are widely preferable in wind farms because of its brushless construction, robustness, low maintenance requirements and self protection against short circuits. However poor voltage and frequency regulation and low power factor are its weaknesses. The magnitude of terminal voltage and frequency is completely governed by the rotor speed, excitation and load. The mutual inductance plays a vital role in building up of the terminal voltage. Apart from modeling a self excited induction generator, this thesis carried out a detailed dynamic analysis of self excited induction generator to analyze the effect of speed, excitation capacitance, and mutual inductance on dynamic power variations and frequency of power exchange and on torque variations. A V/f scalar voltage control scheme utilizing an IGBT based sinusoidal pulse width modulated inverter is simulated without load and with load to know the effect of proportional gain of PI controller on the shape of ac side current and on its frequency, simultaneously extracting the information on dynamic active power and reactive power variations for a fixed prime mover speed. As wind speed is continuously varying, the V/f scalar control scheme is simulated for a continuously varying wide range of prime mover speed. The generated constant ac voltage source is useful to frequency insensitive loads like lighting, heating. The available dc voltage across the DC link capacitor could be used to charge batteries and for further extension to a fixed frequency load, after being converted to ac source of same frequency using another converter.