Multi-level converter with auxiliary resonant-commutated pole

The family of multi-level power converters offers advantages for high-power, high-voltage systems. A multi-level nested-cell structure has the attractive feature of static and dynamic voltage sharing among the switches. This is achieved by using clamping capacitors (floating capacitors) rather than clamping diodes. However, an approach to reduce the switching losses may be necessary in case of high-frequency operation. In this paper, soft-switching techniques are applied to nested cells, based on the auxiliary resonant-commutated pole (ARCP) principle. Attention is paid to a simple three-level power converter leg which shows a high degree of PWM control, the floating capacitor being an integral part of the soft-commutation circuitry. Simulation data and experimental results confirm the analysis.