Enhanced Battery State‐of‐Charge Balancing Strategy for Electric Vehicles and Grid‐Storage Systems With Fault‐Tolerant Capability

ABSTRACT Uneven state‐of‐charge (SOC) levels in multilevel converter (MLC) based battery storage systems (BSS) might yield to undesired efficiency drops on battery performance. Adding possible faults on semiconductors to the existing SOC imbalances increases the risk of system failure and leads to distorted output voltage and current waveforms. The main objective of this study is to critically examine SOC imbalances between different battery packs for semiconductor fault conditions on three‐phase MLC based BSS. This paper proposes a modified level‐shifted pulse‐width modulation (LS‐PWM) based fault‐tolerant (FT) SOC balancing control scheme to manage SOC imbalances and improve post‐fault operation. With the help of the proposed method, SOC balancing operation is maintained even under multiple fault conditions. Furthermore, ripples on active and reactive power values and imbalances on line currents during fault conditions are mitigated successfully. The overall control architecture features a bidirectional power control strategy as the main controller along with FT SOC balancing controller based on the proposed LS‐PWM scheme. Effective performance of the proposed control architecture is validated through different tests including scenarios like SOC imbalances, faults and dynamic load changes and detailed comparions are made to traditional methods. Results reveal that ripples on active and reactive power profiles are reduced, unity power factor is maintained throughout the operation while charging and discharging the batteries. Furthermore, SOC balancing operation is maintained regardless of the operating condition, and balanced line currents are obtained during fault conditions.