A Novel Five-Level Hybrid NPC-ANPC H-Bridge Single-Phase Inverter With Fractional Frequency Half-Cycle Modulation Strategy

This article proposes a novel five-level hybrid neutral point clamped (NPC)-active NPC (ANPC) H-bridge single-phase inverter. This inverter integrates an NPC arm equipped with silicon (Si) devices and an ANPC arm using silicon carbide (SiC) devices with the objective of controlling the cost of SiC devices. A fractional frequency half cycle (FFHC) space vector pulsewidth modulation (SVPWM) strategy is proposed as the means of enhancing efficiency, power density, and thermal stability. The FFHC-SVPWM strategy facilitates the switching devices of the NPC arm to operate at the fundamental frequency, whereas the switching devices of the ANPC arm switch at a high frequency for only half a cycle. This article explicates the operational principle of the proposed hybrid NPC-ANPC H-bridge inverter in detail. Subsequently, a loss model and thermal model are developed to analyze the loss distribution, temperature distribution, and the maximum junction temperature of the power devices. A prototype of the hybrid NPC-ANPC H-bridge inverter is constructed to validate the increase in efficiency, power density, and thermal stability.