A Fast and Generalized Space-Vector Modulation Scheme for Cascaded H-bridge Multilevel Converters Under Faulty Conditions

Space vector modulation (SVM) is widely used for voltage source inverters, but it is too complicated when extended to the cascaded H-bridge multilevel converter (CHMC) under faulty conditions. In this article, a fast and universal SVM strategy is proposed to realize POSTFAULT operation for CHMC. Different fault types can be reflected by the reduction of phase voltage so the proposed scheme first calculates all the available redundant switching states based on available output voltage in three phases. Final-selected switching state is within the selectable range based on the reduced common-mode voltage principle. To generate the switching sequence, discontinuous pulse-width modulation (DPWM) is used, which improves efficiency of the system. The proposed SVM scheme is independent of the number of levels and can be applied in different fault conditions. The performance and effectiveness of the proposed strategy are verified by simulation results.