Effects of Voltage Unbalance and Harmonics on Three-Phase PWM Ac-to-Dc Converters with Instantaneous Power Feedback.

Abstract

A PWM three-phase ac-to-dc converter with unity input power factor can be approached by setting the required active power and setting reactive power zero in the instantaneous reactive power theory. The instantaneous reactive power theory is proposed by Akagi and is usually used to design reactive power and harmonic compensators. In the power distribution system, voltage unbalance and harmonics always exist. The effects of the harmonics and voltage unbalance are presented and discussed in this paper. Moreover, a low pass filter is suggested to add into the coordinate transformation in the instantaneous reactive power theory to reduce the effects of harmonics and unbalance in the power source. Finally, the theoretical results are verified both by simulated and experimental results in a laboratory prototype system.