Adaptive carrier based PDPWM control for modular multilevel converter with fault-tolerant capability

Modular multilevel converters (MMCs) are considered very promising converters due to their modularity structure and high reliability from fault-tolerant. A fault within a submodule (SM) is one of the main issues in half-bridge MMCs with substantial switching devices. In this paper, an adaptive carrier based phase disposition pulse width modulation (PDPWM) technique for MMCs, which uses only one carrier having flexibility with fault-tolerant capability, is presented. The energy-based control is also used in this study to regulate the balancing of SMs during and after a fault. In order to investigate the performance of the proposed method, a laboratory single-phase MMC prototype has been built by using four SMs to generate nine-level. The single-phase MMC prototype is tested by assuming one of the SMs in the failure condition. The result revealed that the proposed method had been successfully applied to the MMC prototype to control the upper and lower arm during the failure. In addition, the reference command will correct the fault according to the adaptive carrier and the computational burden is lesser since it only uses one single carrier.