Analysis and Minimization of Neutral Current of Three-level PWM Inverter

A new approach to analysis and minimization of neutral current of three-level PWM inverter is proposed in this paper. At first, expression for inverter neutral current as a function of PWM reference signal is derived. Based on the derived expression, the PWM reference signal that results in minimum neutral current is determined. For unity power-factor operation, it is found that the optimum reference signal is a sinusoidal signal plus twenty-five percent third harmonic. Several experimental results are included to show the validity of the proposed approach.