Microprocessor Control of Phase-Controlled Converters and Cycloconverters

Abstract

Phase-controlled thyristor converters [1, 2] provide AC/DC controlled power conversion. Depending on the circuit arrangement power can flow in either direction, the converters thereby acting respectively as controlled rectifiers or synchronous inverters. Apart from low-power systems the AC supply used is normally three-phase, or multi-phase as derived from suitable transformer connections or otherwise. The thyrisors in the converter are sequentially triggered into conduction and in the normal process of switching, the device(s) previously conducting will experience a reverse bias, presented by the supply voltage, and turn off after a short period of time. This mechanism is known as “natural commutation”, because no additional or external means is utilised for device turn-off or commutation purposes.