Performance of wound rotor induction generators with the combination of input voltage and slip power control

Input voltage control had been used for the improvement of power factor in grid-connected wind power based induction generators. However, efficiency in this case is very poor and the control range is also limited. The conventional rotor resistance control had also been used for wind power generation but in this case too, the input power factor becomes very poor. In this paper, a new control method is being proposed where both input voltage and slip power control are combined to achieve better performance of wound rotor induction generators (WRIG) for wind power generation. For each operating point, an optimum input voltage is set and the slip power is controlled by rotor impedance such that the maximum efficiency is achieved. Both power factor and efficiency improve for a wide range of speed variation. Moreover, the reactive power demand remains nearly constant which is compensated by a fixed value capacitor whose optimum value is found through the simulation. Moreover, the capacitors being placed at the rotor side, the efficiency of the proposed controller improves further. This scheme is useful for low power wind energy conversion system (WECS) where the wind speed varies over wide range. The performance of the proposed system under various wind conditions is experimentally verified.