This paper presents a performance investigation and design optimization of a high efficiency three-level Active Neutral Point Clamped (ANPC) inverter topology using hybrid Si/SiC switches. It uses a modulation strategy that produces a cluster of low frequency switches commutating at fundamental line frequency (realized with Si IGBTs) and high frequency switches commutating at carrier frequency (realized with hybrid Si/SiC switches) to facilitate a tradeoff between the inverter efficiency and cost. A generalized Si/SiC current rating ratio optimization algorithm is presented for the hybrid Si/SiC switches based on the power loss profile of ANPC inverter. This algorithm determines the optimal current rating ratio between the Si IGBT and SiC MOSFET for the hybrid Si/SiC switches based on the inverter operating specification and Si/SiC gate control technique to achieve the best tradeoff between cost, loss and reliability. The performance of the proposed ANPC inverter system is investigated and compared with other similar ANPC inverter systems. The proposed ANPC inverter system achieves higher efficiency compared to an all Si IGBT based ANPC inverter system, all SiC MOSFET based ANPC inverter system, and other ANPC inverter systems consisting mixed Si IGBT and SiC MOSFET devices. On the other hand, the semiconductor device cost of the proposed ANPC inverter system is much lower than an all SiC MOSFET based ANPC inverter system and the mixed Si IGBT and SiC MOSFET based ANPC inverter systems while it is on par with an all Si IGBT based ANPC inverter system.

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Hybrid Si/SiC switches constituting a parallel connection of a lower current rated SiC MOSFET and a higher current rated Si IGBT are becoming very attractive solution for designing high frequency and high-power density power electronic converters.Due to the complementary nature of Si IGBT devices (smaller inverter cost and smaller conduction loss) and SiC devices (smaller switching loss and higher junction temperature capability), these novel switch device configurations enable a good tradeoff between cost and efficiency for high power converter applications. One such recent application of hybrid Si/SiC switches for efficiency-cost optimization is an Si/SiC hybrid switch based ANPC inverter proposed in Ref. [30]. In Ref. [30] the topology structure, modulation strategy and the efficiency-cost benefits of the proposed ANPC inverter is presented. In this paper a precise electro-thermal power loss model for this ANPC inverter topology will be presented based on the modulation strategy of the inverter and the operating characteristics of the Si/SiC hybrid switches. The power loss model development takes into account how the current sharing between the two internal devices of the Si/SiC hybrid switches and their corresponding gate control method affects their power loss. A brief introduction to the topology structure and operation principle of the Si/SiC based ANPC inverter is first highlighted to provide context for readers and then a detailed description of the proposed electro-thermal power loss model is presented. The precision of the electro-thermal power loss model introduced in this paper is then validated using experimentally measured energy loss, device temperature and inverter efficiency data.