Fault-tolerant control of energy storage systems based on single-IGBT open-circuit faults

Abstract

Cascaded energy storage systems are well-suited for medium- and low-voltage power grids, offering an effective solution to power quality issues caused by the integration of renewable energy sources. However, the reliability of cascaded H-bridge converters is critically challenged by the pervasive integration of power switching devices. As the number of submodules increases, maintaining reliable operation becomes increasingly challenging. To enhance the faulttolerant capability of such systems, this paper investigates the operational behavior of CHB-based energy storage converters under single-switch open-circuit faults in power submodules. A fault-tolerant control strategy is proposed that operates without requiring hardware redundancy. By analyzing the output characteristics of the H-bridge submodule under fault conditions, a modulation reconstruction method is developed, enabling the failed module to continue operating at 50% of its nominal AC voltage.By maximizing power injection from the compromised module, this method significantly boosts system robustness under fault conditions.