Reduction of Common-Mode Voltage in Cascaded H-Bridge Inverter Under Faulty Conditions

This paper proposes a new fault-tolerant method for cascaded H-bridge multilevel inverters (CHB-MLIs) to reduce the common-mode voltage (CMV) and improve its performance under faulty conditions. As injected CMV can affect the proper operation of the inverter, especially in AC motor drives, it should be decreased as much as possible. So, after balancing the line-to-line voltages in post-fault conditions, one of the significant challenges is reducing CMV. In the presented method, it has been proven that the average of the down-boundary of CMV is negative, while the average of its up-boundary is positive. Using this fact, the CMV reference is generated to take the minimum fundamental component compared to the existing fault-tolerant methods. The effectiveness of the proposed method is verified in MATLAB/SIMULINK on II-level CHB-MLIs, and a comparative analysis is provided with the current methods.