A novel PWM strategy to minimize the surge voltage for current-source converters

This paper presents a novel technique of pulsewidth modulation (PWM) wave control to minimize the surge voltage at the turn-off of switching devices. Two kinds of sawtooth carriers with different hypotenuses are employed to obtain a PWM waveform with minimum surge voltage, where each sawtooth carrier appears alternately at every 60/spl deg/ interval relative to the sinusoidal wave cycle. It is difficult to analyze the output waveforms because they are complicated. In order to obtain the analytical result, a frequency analysis approach using a switching function is proposed the results of which are verified experimentally.