Hybrid Si-SiC three-phase voltage source converter based on fractional power conversion

This paper proposes IPOS Si/SiC hybrid inverter and its modulation strategy. The low-frequency unit leverages the strong current-carrying capacity of silicon-based devices for main power conversion. Meanwhile, the high-frequency unit, based on wide-bandgap semiconductor SiC devices, not only eliminates partial harmonics from the low-frequency unit but also enhances the overall system efficiency. Compared to existing "IPOP" Si/SiC hybrid inverters, this topology introduces a coupling step-down transformer on the output side of both low-frequency and high-frequency units, reducing current stress on the SiC devices. This topology combines the strong current carrying capability of Si devices with the low switching loss of SiC devices at high frequency. Based on the harmonic distribution characteristics of the low-frequency and high-frequency units, this paper establishes a mathematical model and designs the control system. Building upon the derivation of the voltage ripple model and the design of hardware parameters, Si IGBT and SiC MOSFET were selected for constructing a 7.5 kW inverter prototype for testing.The experimental results validate the feasibility of this topology and the accuracy of theoretical analysis.