Short circuit and overcurrent protection of IGCT-based three-level NPC inverters

In this paper, a new method for protection of IGCT based three-level NPC inverters is introduced and compared with other protection methods already presented in the technical literature. A system for fast overcurrent detection and inverter tripping is also presented as well as a complete discussion of the inverter design issues involved in the proposed protection scheme. Simulation results are included to support a comparative analysis of the considered inverter protection schemes. Experimental results from a lab scale prototype illustrate the performance of the proposed short-circuit and overcurrent detection circuitry. Although the discussion in this paper is aimed at three-level NPC inverters, it can be extended to two level inverters.