Investigation of a high-power three-level quasi-resonant DC-link voltage-source inverter

This paper investigates the feasibility of a quasi-resonant DC-link soft-switching principle for voltage-source inverters (VSIs) in the megawatt power range. An evaluation of a three-level quasi-resonant DC-link VSI (3L-QRDCWSI) featuring integrated gate-commutated thyristors (IGCTs) and a comparison-to a commercially available three-level IGCT-VSI is presented. Extensive loss measurements of IGCTs under hard- and soft-switching conditions are the basis for the design and the comparison of the inverters. Aside from converter losses, other important aspects such as control, protection, and reliability are addressed.