Reliability-Oriented Analysis of PWM Strategies in Three-Level Converters in PV Systems

Power devices and DC-capacitors are key components of power converters, but also the two most failureprone parts. Thermal stress, induced by power losses contributes significantly to the degradation and eventual wear-out of these components. Pulse-width modulation (PWM) method plays a crucial role in the distribution of those losses. Previous PWM studies focused on the power devices and capacitors, respectively. However, the PWM's impact on system level was not considered. This paper investigates the impact of different PWM methods on the reliability of power devices, capacitors and system performance in three-level NPC converter, focusing on their power losses and thermal loadings under a mission profile of PV system, while maintaining comparable current THD. The analysis shows that DPWM1 can ensure an optimal trade-off of between lifetime of power devices and capacitors. Experimental results show the performance of different PWM methods.