On the characteristics of a PWM AC controller using four switches

A pulse-width modulation (PWM) AC controller using forced commutated devices has important advantages as compared with a line-commutated AC controller with thyristor technology. These advantages include sinusoidal input-output current/voltage waveforms, smaller input/output filter, better input power factor and better transient response. The performance of a three phase PWM AC controller using only four switches is evaluated. The operation as a voltage source of this power converter topology is analyzed. This includes the conversion characteristic, harmonic generation and the snubber capacitor required to minimize overvoltages during the dead-time. A design procedure including the input filter is proposed and the theoretical results are verified experimentally on a 5 kW breadboard unit