A carrier-based adjustable discontinuous PWM for three-phase voltage source inverter

PWM strategy is classified into a Continuous PWM (CPWM) and a Discontinuous PWM (DPWM). Because the conventional DPWM has constant non-switching period which is 120° of fundamental period, DPWM could bring about the high Total Harmonic Distortion (THD) compared to CPWM and the lower switching loss than CPWM. This paper presents a carrier-based Adjustable Discontinuous Pulse Width Modulation (ADPWM) for 3-phase Voltage Source Inverter (VSI). The non-switching period can be controlled from 0° to 120° of fundamental period using the proposed PWM strategy. Thus, it can be noted that the ADPWM offers tradeoff between THD and switching loss. This paper also proposes a seamless transfer method from CPWM to DPWM with the proposed PWM strategy. With the proposed method, the non-switching period is variable according to Modulation Index (MI). The validity of the proposed strategies is verified by the experimental results with 3.7 kW induction machine drive.