Optimal reactive power controller for wind-driven stand-alone doubly fed induction generators

A control strategy has been proposed for minimising the machine loss by optimally sharing the reactive power at the stator and rotor terminals of stand-alone doubly fed induction generator. For achieving this, fixed capacitor along with static synchronous compensator at the stator terminals has been employed apart from battery inverter system at the rotor terminals. A TMS320LF2407A digital signal processor–based controller has been developed for maintaining the stator voltage magnitude and frequency. A method has been developed for calculating the optimal reactive power at the stator terminals using the steady-state equivalent circuit of the proposed system. An analogue circuit–based optimal reactive power controller has been designed and fabricated in the laboratory for supplying this optimal reactive power at the stator terminals for all operating conditions. The salient feature of the proposed optimal reactive power controller is that it needs to monitor only the reference value of reactive power at the stator terminals for any operating conditions. The successful working of the proposed controller has been amply demonstrated through extensive analytical and experimental results obtained on a three-phase, four-pole, 415 V, 50 Hz, 5 kVA doubly fed induction generator.