Minimum Switching Frequency and Maximum Power Factor

This paper presents a unique PWM switching pattern and a novel power factor control scheme for high power GTO ac/dc converters. This switching pattern has a switching frequency of 360Hz, which is the lowest possible frequency to achieve 5th and 7th harmonic elimination and an adjustable dc output current simultaneously. Using both feedback and feedforward control techniques, the proposed power factor control scheme can keep the converter input power factor at unity or a maximum achievable value. Simulation and experimental results are given to confirm the proposed PWM pattern and power factor control scheme.