Operation of inverter-assisted wind-driven slip-ring induction generator for stand-alone power supplies

The operation of wind-driven single inverter-battery-assisted slip-ring induction generator (SRIG) for stand-alone power supplies has been proposed. For effective utilisation of wind energy, the proposed system will function as doubly fed induction generator (DFIG) or shorted stator induction generator (SSIG) depending upon the ac load requirement and available wind power, operating in four different modes. A method has been developed for the performance predetermination of such system. A supervisory control algorithm has been devised and implemented using TMS320LF2407A real time digital signal processor for the closed-loop control of the proposed system. In this control algorithm, reliable and unambiguous feedback signals such as stator voltage, stator current and user command are used for decision making and for closed-loop operation. The entire closed-loop system with supervisory control algorithm has been tested in the laboratory with a 3.7 kW SRIG. The successful working of the proposed system with smooth changeover between the operating modes has been demonstrated with extensive experimental and simulation results. The advantage of the proposed wind energy system has also been brought out in comparison with classical back to back converter DFIG system for stand-alone power supplies.