Speed sensor-less maximum power point tracking and constant output power operation of wind-driven wound rotor induction generators

A simple control strategy has been proposed for maximum power point tracking (MPPT) mode and constant output power mode operation of variable speed wind turbine system employing wound rotor induction generators (WRIGs). The control strategy proposed in this paper has been implemented using TMS320LF2407A real time digital signal processor (DSP) and detailed procedure for such implementation is given. The salient feature of the proposed controller is that it employs only a single switch, which is an IGBT chopper and does not require any mechanical sensors or machine parameters. This makes the overall controller simple, flexible and robust. Further, space heating and battery loads are connected at rotor side of the machine through a diode bridge rectifier and the IGBT chopper. A method has been developed for the analysis of such grid connected WRIGs with variable external resistance at the chopper circuit. The successful working of the proposed controller has been amply demonstrated through extensive simulation and experimental results on the WRIG system for MPPT and constant output power operation.