Improved power regenerative controls by using thyristor rectifier bridge of voltage source inverter and a switching transistor

A few improved techniques of regenerative control for the voltage source inverter are described. In the proposed equipment, the thyristor rectifier bridge can be also utilized for regeneration through a DC reactor or capacitor. For the first converter mentioned, a novel pulse-width-modulated (PWM) strategy is proposed in which the polarity of the sawtooth carrier waveforms is reversed alternately at every 60° interval of the fundamental frequency to reduce the harmonics in quantity. For the next proposed type, a modified Cuk converter method is described for regeneration, whose output current becomes a perfectly zero ripple. The third purpose is to propose a novel frequency analysis method using the switching function. The validity of its theory is confirmed experimentally