Hybrid Si/SiC NPL.H Three-Level Inverter for Cost-Effective Electric Propulsion System

Neutral-point-less H-type (NPL.H) three-level inverter has been recently proposed, eliminating the need for split dc-link capacitors and offering improved power density and overall performance. These characteristics makes the NPL.H a strong candidate for heavy-duty electric vehicle (EV) applications. However, like other multilevel topologies, the NPL.H inverter requires more switching devices than a conventional two-level (2L) inverter, making a full silicon carbide (SiC) implementation costly. To address this, this paper proposes a hybrid Si/SiC NPL.H inverter that combines the performance benefits of multilevel topologies at reduced cost. The proposed hybrid approach replaces the inner switches with SiC devices while retaining silicon (Si) IGBTs on the vertical switches. This reduces the number of required SiC devices by two-thirds and enables operation in a 2L inverter mode at very high-speed ranges if needed. Simulation results show that the proposed hybrid NPL.H inverter achieves the lowest total harmonic distortion (THD) and overall high efficiency. It also reduces switching device cost by 35 % compared to a SiC-based 2L inverter, and cuts dc-link capacitor size by 49 % compared to 2L inverter, making it an optimal choice for heavy-duty EV applications.