Seamless Fault-Tolerant Control for Cascaded H-bridge Converters Based Battery Energy Storage System

This article presents a phase-shifted pulsewidth-modulation-based fault-tolerant approach for the cascaded H-bridge-based battery energy storage system to ride through the single switch fault. When the fault occurs, the faulty cell is bypassed first. Afterwards, the missing voltage levels of the faulty cell are compensated by the remaining healthy cells to maintain the line-to-line voltages balanced. The compensation of the missing voltage levels presented is achieved by simple logic operation without modifying three-phase voltage references and phase-shifted angles of carriers, which enables seamless operation and enhances the system stability. In addition, the detailed active power control strategy used for state-of-charge balancing of the battery units is proposed and discussed. The validity and effectiveness of the proposed method are verified by simulation and experimental results.