Analysis of zero-sequence circulating current in parallel PWM inverter system with difference of carrier wave phases

Abstract

Disaccord of inverter instantaneous output voltages is the ultimate factor that causes circulating current between inverters in parallel inverter system. As a familiar control method of inverter, sinusoidal Pulse Width Modulation is widely used to control output voltage of inverter to realize energy transformation. In this paper, the circulating current characteristics in parallel PWM inverter system with same sinusoidal modulating waves and different phase triangular carrier waves are analyzed. By using Fourier Transform of circulating current, the principle of zero-sequence circulating current changing with carrier wave phase difference is obtained. Simulation results are presented to verify the proposed analytical method. © 2011 Springer-Verlag.