A Novel Hardware Protection Scheme for a Modular Multilevel Converter Half-Bridge Submodule

The Modular Multilevel Converter (MMC) has become progressively an attractive solution for the medium-power and the high-power applications, due to its modularity, flexibility of redundancy or scalability, high efficiency and low production of harmonic contents. However, in order to have a reliable and robust MMC system, different concerns should be observed in terms of the converter control complexity and the required effective protection system. In this context, this paper presents a novel hardware protection topology for the MMC half-bridge submodule. The introduced scheme is based on new sensors technology that can be assembled near the power hardware, resulting in less perturbation and a very low signal delay. This allows the protection system to respond quickly to fault situations. The proposed protection scheme of half-bridge MMC submodules is a new contribution given the steadily increasing popularity of the MMC and that just a few scientific publications treat in detail the protection mechanisms of half-bridge submodules for MMC. The experimental results confirm the effectiveness of the proposed scheme after creating the fault overvoltage and overcurrent conditions on one MMC half-bridge submodule.