Space vector modulator for forced commutated cycloconverters

Abstract

A pulse-width modulation (PWM) control technique for forced commutated cycloconverters is presented. The technique is based on the space vector representation of the voltages in the complex plane. It is shown that with the allowable switching combinations, six output voltage space vectors with varying amplitudes can be obtained, in addition to the zero vector. The variation is compensated by adapting the standard modulation technique. The technique permits space vector synthesis of a three-phase, nonsymmetrical, nonsinusoidal output voltage, even under non-steady-state conditions, which is essential for the AC servo drives. A detailed explanation of the modulator principles and the switch control as well as simulation results for the time- and frequency-domain analysis is given. The results are compared with the results obtained using the standard modulation technique. A possible microprocessor implementation of the modulator is also proposed.