A high switching-frequency MOSFET-based three-level voltage-source converter

This paper describes a new commutation-strategy and modulation-strategy for Three-Level Voltage-Source-Converter (TL-VSC) based on MOSFET switches. The objectives are to (i) reach to a high switching-frequency, e.g., above 40kHz, in order to reduce the weight of passive components of the three-level converter, i.e., dc-link capacitors, and (ii) proposing a new commutation strategy to keep the efficiency of the converter as high as possible. The modulation strategy allows direct control of the input-currents and output injected common mode voltages while guaranteeing a sinusoidal output-current even at unbalanced operation. The commutation strategy is a single-step commutation strategy using integrated snubber-circuit with an adaptive delay turn-on which minimizes the period of switching device transitions. A potential application of the proposed three-level converter is micro-converter for multi-phase application. This paper demonstrates a TL-VSC operating at 43.4kHz, with small distributed capacitors. The modulation strategy provides the opportunity of balancing the dc-link capacitors without any output harmonic injection and limitation on the output real power. The guidelines to extend the formulation of the proposed modulation strategy to Multi-Level Voltage-Source-Converters, i.e., ML-VSCs, are also provided.