Harmonic Analysis of Microprocessor based Three-Phase Improved Power Quality AC/AC Voltage Controller using Power MOSFETs

A three-phase pulse width modulated AC/AC voltage converter using power MOSFETs that operate in a high-frequency chopping mode is proposed. The symmetrical multipulse modulation strategy (SMM), wherein several equidistant pulses per half cycle (M), are used, is adopted. The resulting harmonic output voltages are analyzed and compared with those of phase control. The analysis reveals that substantial decrease in lower order harmonics and their selective elimination takes place with increase in M. The magnitude of the harmonic voltages is computed in terms of M and duty cycle. From the power quality perspective, it is theoretically established and experimentally confirmed that, with resistive load, for the same per unit output voltage, the supply power factor in the SMM and phase control techniques is the same