A Hybrid Si/GaN 5-Level Flying Capacitor Single-phase Inverter and its Current Ripple Analysis

The GaN flying capacitor multilevel converter (FCMC) offers a better harmonic spectrum and attains higher voltages with a limited maximum device rating but suffers from high components quantity and cost. In this paper, a Si/GaN hybrid single-phase 5-level flying capacitor multilevel inverter (FCMI) is proposed with a much-reduced component quantity and cost. The proposed hybrid FCMI consists of only two pairs of GaN devices and a pair of line-frequency Si devices, compared with four-pairs eight high-frequency GaN devices in a conventional five-level FCMI. Furthermore, the proposed FCMI has a twice effective voltage. The operation principle and modulated strategy are detailed discussed. Meanwhile, a new current ripple model is introduced to investigate the output performance. A 600V, 5-level hybrid Si/GaN converter prototype is designed and built. The experimental results confirm the validity and effectiveness of the presented converter and current ripple model.