It is well known that non-linear semiconductor circuit applications such as rectifier circuits have been widely used, so that various harmonics are generated in the power system. As a result the large capacity of the conventional thyristor rectifier circuit will be controlled to use. Consequently, the PWM converter using self-turned off switching devices will be put into wide applications.
In this paper, we propose the novel strategy of PWM wave control to minimize the surge voltage at the turned off of switching devices. For the first method, the saw-tooth carrier wave is compared with the input power phase voltage wave for sine reference, in which the polarity of the saw-tooth carrier waveform is reversed alternately at every 60° interval of the fundamental frequency. For the second method, the line voltage waveform is used for sine reference, in which the saw-tooth carrier wave is reversed at every 30° interval of the fundamental frequency. The input current PWM waveforms using the novel strategy are analyzed by means of the proposed switching function.
