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.