Real-time Volt/Var optimization through bidirectional chargers in battery swapping stations: A hierarchical scheduling strategy

•Modeling for BSS providing voltage regulation with four-quadrant chargers.•A hierarchical scheduling strategy for BSS supporting VVO with low solving complexity.•Triangle-trapezium linearization approach for apparent power and PF angle constraint. The battery swapping station (BSS) can play an essential role in maintaining the voltage stability of distribution networks. However, the implementation faces two major problems: 1) participating mechanism of BSS in voltage regulation, and 2) the computational burden brought by controlling massive batteries in multiple BSSs. To address the above issues, this study proposes a hierarchical scheduling strategy, using the four-quadrant chargers to participate in real-time Volt/Var optimization. The strategy is the first-of-its-kind solution that harnesses the reactive power compensation potential of BSSs. Specifically, in the upper layer of the strategy, each BSS is equivalent to an electrochemical energy storage system to reduce the variable dimension. The independent system operator (ISO) conducts centralized scheduling to obtain the required active and reactive power of BSSs. The BSS operation model is established in the lower layer to respond to the required power while satisfying the BSS operational constraints. Additionally, a new triangle-trapezium linearization approach is developed to reduce computational complexity. Simulation results based on the IEEE 33-bus system validate the effectiveness of the proposed strategy in voltage regulation and power factor enhancement; moreover, the solving time is reduced by 92.29 % compared to the benchmark.