Reliability-Enhanced PWM for NPC Inverter Focusing on Lifetimes of DC-Link Capacitors and Power Devices

Power devices and dc-link capacitors are generally considered the most reliability-critical components in power converters. Thermal stress caused by power loss leads to wear-out failures of dc-link capacitors and power devices. Previous studies have proposed various pulsewidth modulation (PWM) methods for improving the lifetime of dc-link capacitors and power devices by reducing their thermal loadings. However, the previous research only focused on each component separately. They did not consider the reduction in thermal loadings of dc-link capacitors and power devices simultaneously. This article proposes the PWM method for improving the reliability of the neutral-point-clamped (NPC) inverter by decreasing the thermal loadings of dc-link capacitors and power devices concurrently. The feasibility and effectiveness of the proposed PWM method are verified through the simulations and experiments.