A Novel Single-Phase Dual-Buck Three-Level Flying Capacitor Inverter for Mitigating Shoot-Through Problem

Abstract

This paper presents a novel single-phase dual-buck three-level flying capacitor (FC) inverter. The topology derives from the conventional FC inverter, which is widely studied and applied because of modularity, low voltage stress across the switch, and high efficiency. However, a well-known challenge in the high-power density conventional FC inverter adopting fast-switching wideband gap devices, such as SiC switches, is a shoot-through problem that may occur because of cross-talk effects, switching mismatch, and electronics delays. As an existing solution, the risk of shoot-through in the traditional FC inverter can be suppressed by injecting dead time in the switching signals. However, this technique increases the distortion of the output waveforms. This paper proposes an inverter topology that mitigates the problems mentioned above. The proposed inverter requires one flying capacitor, four active switching devices, two diodes, and two shoot-through protection inductors. Like the conventional FC inverter, the proposed inverter utilizes one-half fewer flying capacitors than the counterpart dual-buck inverter while maintaining the same voltage stress across the switches. Moreover, by mitigating the shoot-through problem, the reliability of the inverter is improved. The detailed operation of the inverter implementing level-shifted PWM is provided. The advantages and performance of the proposed inverter were demonstrated in simulation and validated in experiments. A 98.77% maximum efficiency was achieved by the proposed dual-buck FC inverter at a switching frequency of 40 kHz.