A Partial-Power Converter for Battery Energy Storage System With DC Fault Blocking Capability

The battery energy storage system (BESS) based on Lithium batteries is seriously challenged by inner battery voltage variation due to the change of state of charge (SOC), and outer high short-circuit current incurred by dc bus fault. To overcome these issues, this article proposes a partial-power converter for BESS. It stacks voltage-tuning bridge and reversal-blocking chopper on battery pack with their dc-links crossly connected through a three-port dc–dc circuit. The dc–dc circuit provides isolated low-impedance channels for automatically clamping dc-link voltages. This ensures the linear voltage regulation in normal state and immediate short-circuit-current blocking under fault condition. As compared to the prior arts, the proposal achieves: 1) linear voltage regulations in wide range through step-up and step-down operations guided by pulse width modulation without any dead zones; 2) immediate dc fault blocking by deenergizing short circuit loop rather than by interrupting the current, thereby avoiding spike and stickiness issues; and 3) around 0.5% enhancement in power efficiency due to the fully resonant dc–dc unit with low switching losses, and the substitution of the two anti-series switch in dc breaker by the one in reversal-blocking unit. The entire system achieves the maximal power efficiency of 98.93%. The feasibility of the proposal is fully confirmed by the experiments rated at 350-V 3.5-kW.