The investigation on a novel IGCT-based cascade high voltage large capacity converter

Large capacity converter is widely used in various national economic fields. The novel topology and new emerging device with high voltage and current are the ways to get large capacity converter. In media and high voltage large capacity AC-DC-AC converter systems, the Integrated Gate Commutated Thyristor (IGCT) takes the place of gate turn off thyristor (GTO) duo to its excellent performance. In this paper, the investigation on a novel IGCT-based cascade high voltage large capacity converter is presented. The base unit of the converter is IGCT-based three-level neutral point clamped (NPC) H-bridge converter. Its output voltage has five levels. One phase circuit of the converter this paper presented consists of two base units and its output phase voltage has nine levels. The converter adopts phase shift input transformer to reduce the harmonics in grid side. The output line root-mean-square (RMS) voltage can reach 10kV ant its power capacity can reach 30MW. Three types of carrier-based PWM strategy based on cascaded carriers and phase shift consideration are proposed. The comparison analysis among three types of strategy by simulation result is implemented.