Effects of voltage unbalance and harmonics on three-phase SPWM AC-to-DC converters with instantaneous power feedback

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 to zero in the instantaneous reactive power theory. The instantaneous reactive power theory, proposed by Akagi, is usually used to design reactive power and harmonic compensators, and it is based on a balanced three-phase voltage source. But, voltage unbalance and harmonics exits in the power distribution system. The effects of the harmonics and voltage unbalance are presented and discussed. Moreover, a low pass filter is proposed to add into the coordinate transformation in the instantaneous reactive power theory for reducing the effects of harmonics and unbalance in the power source. Finally, the theoretical results are verified both by simulated and experimental results in a 3 KW laboratory prototype system.<<ETX>>