Chopper-controlled wind-driven self-excited induction generators

Two chopper circuit configurations, one with voltage commutation, are shown to be useful for obtaining a controllable DC voltage from wind-driven self-excited pole-changing induction generators. For the case of a resistive load, expressions for the average load voltage and power are derived, and a set of normalized curves relating the voltage ratio and time ratio is drawn. Experimental results on a self-excited induction generator with a 4/6-pole combination using these choppers fully demonstrate the utility of the setup as a whole. Test results on an induction generator controlled by DC choppers demonstrate that any desired load voltage up to a maximum of input voltage can be maintained easily by varying the time period in the case of a load-commutated chopper and the on-off-time ratio in the case of a voltage-commutated chopper