Failure Mode Analysis and Protection of Non-Regenerative Three-level Boost Rectifier

This paper identifies a new fault type of non-regenerative three-level boost rectifiers (Vienna-type rectifiers), namely the dc-link voltage-doubling fault. Under this failure mode, the voltage across the dc-link capacitors is doubled when any of the ac switches in the neutral path of the converter is shorted, a unique behavior of three-level neutral-point clamped topologies. Addressing this, two types of protection methods are proposed, discussed and analyzed in this paper, the voltage clamping and the current breaking protection schemes. The impact of the ac inductors on the voltage-doubling phenomenon is studied carefully, and a guideline for the protection scheme selection is provided. This failure mode and the current breaking protection scheme are fully analyzed and verified by simulation and experimental results.