Hierarchical Control and Full-Range Dynamic Performance Optimization of the Supercapacitor Energy Storage System in Urban Railway

The installation of a stationary supercapacitor energy storage system in urban railway systems effectively improves the energy saving rate by means of recycling the train's regenerative braking energy. In this paper, a hierarchical control strategy, which consists of an energy management layer and a converter control layer, is proposed. In the energy management layer, the energy management state machine is introduced. In the converter control layer, based on the double closed-loop proportional-integral (PI) control strategy, a multiobjective optimization algorithm for the outer voltage loop is proposed, which optimizes the control parameters at each operating point, comprehensively considering undershoot suppression, rapidity, and anti-disturbance performance of the system. The proposed control strategy is validated through simulation and laboratory experiment, and finally, applied in the Megawatt-level energy storage device of Beijing Batong Line.