A Passive System for Optimising Battery Charging using a Permanent Magnet, Variable Speed Generator

Abstract

The performance of a permanent magnet, variable speed generator charging a battery via a PWM converter or rectifier is considered. It is found that in neither case can the system be configured to generate electricity at low wind speeds while maintaining optimum efficiency at rated wind speed. Accordingly, an alternative system which permits operation at close to optimum efficiency over the full range of wind speeds below rated is proposed. This uses two separate generator windings, one of which begins to charge the battery at a much lower wind speed than the other. Experimental results are presented which confirm the theoretical analysis.