Closed-loop Elimination of Low-order Sideband Harmonics in Parallel-Connected Low-Pulse Ratio VSIs

This paper proposes a closed-loop pulse width modulation (PWM) carrier phase shifting method for eliminating the low-order sideband harmonics in parallel-connected low-pulse ratio VSIs. A current sensor is added to measure the THD of total current to adjust the PWM carrier phase of inverters with closed-loop control. First, the low-order sideband harmonics caused by the multiple modulation references are analyzed. Then, the basic idea and the realization of the closed-loop PWM carrier phase shifting method are discussed. Finally, simulations and experimental results verified the proposed method.