A thyristor phase-controlled voltage-source converter with bidirectional power flow capability

A new line-commutated thyristor phase-controlled voltage-source power converter (VSC) with bidirectional power flow capability is proposed and studied. The proposed power converter has the same structure as the pulsewidth modulation (PWM) VSC, however, the switching devices are not self-commutated devices but line-commutated thyristors, and the converter is operated not with PWM but with six-pulse phase control. As in the case of the PWM VSC, the proposed converter provides a bidirectional DC-side current capability and, hence, the DC-side voltage can be regulated at its desired value. The harmonics are much smaller than those in the conventional thyristor phase-controlled current-source power converter. The proposed converter can be useful as a utility interface power converter, especially in high-power voltage-source inverter motor drive systems with regenerative braking.