Fault-tolerant control for a battery energy storage system based on a cascade PWM converter

This paper focuses on fault-tolerant control for a battery energy storage system based on a three-phase multilevel cascade PWM (pulse-width-modulation) converter with star configuration. It enables continuous operation and maintains SOC (state-of-charge) balancing of operating battery units even during the occurrence of a converter-cell or battery-unit failure. This enhances both system reliability and availability. A 200-V, 10-kW, 3.6-kWh laboratory system combining a three-phase cascade PWM converter with nine NiMH (Nickel-metal-hydride) battery units is designed, constructed, and tested to verify the validity and effectiveness of the proposed fault-tolerant control.