Reduction of DC-link current harmonics for three-phase VSI over wide power factor range using single-carrier-comparison discontinuous PWM

This paper proposes a novel discontinuous PWM (DPWM) in order to reduce dc-link current harmonics of a voltage source inverter (VSI) over wide load-power-factor range. This modulation method, which requires only one carrier, contributes to a lifetime extension of smoothing capacitors in a motor drive system. Furthermore, by realizing this modulation method with only one carrier, a high cost hardware such as a field-programmable gate array (FPGA) is not necessary. By adding an offset to voltage references of conventional DPWM, and shifting two unclamped voltage references in every half control period, the dc-link current harmonics are reduced even when load power factor changes. It is clarified by experiments that the proposed DPWM reduces the dc-link current harmonics by 18.4% at most at modulation index of 0.705 and load power factor of 0.819.