Current Ripple Mitigation in DC-Link Capacitors of Three-Phase NPC Converters Using Mixing Level-Shifted Modulation Schemes

The DC-link capacitor is one of the most frequently failed components in high voltage power converters since the DC-link capacitor usually absorbs large switching-frequency harmonics associated with the DC-link current, leading joule losses in the equivalent series resistor of the capacitor. To extend the lifetime of the whole system, a novel phase-disposition (PD) pulse-width modulation (PWM) technique is proposed in this paper to mitigate those DC-link current ripples of three-phase neutral point clamped (NPC) converters, mixing PD-PWM strategy is proposed to suppress these DC-link current ripples. Comprehensive studies of the proposed mixing PWM scheme under various operating conditions is conducted analytically. To validate the effectiveness of the proposed scheme, both numerical simulations and hardware experiments are conducted. These results can demonstrate the superior performance of the proposed scheme.