The utilization of a supercapacitor energy storage system (ESS) to store regenerative braking energy in urban rail transit can achieve an energy-saving effect. This paper proposes a brake voltage following energy management strategy of ESS to adjust the charging and discharging threshold voltage based on the analysis of train operation states. The energy storage device state of charge is considered to realize the maximum usage of the ESS. First of all, the mathematical model of the dc traction power system, which encompasses the train, ESS, and traction substation, is established. Then, the energy allocation influence factors are analyzed, in particular for the double train structure. Second, under the different conditions, with the real-time monitoring of the traction network voltage and the train status, an energy management state machine is determined. Meanwhile, a set of effective state switching schemes is given to achieve the transformation of the energy management states. In the end, both the simulations using actual line data and main track field experiments prove the rationality and validity of the proposed management strategy.

The installation of stationary super-capacitor energy storage system (ESS) in metro systems can recycle the vehicle braking energy and improve the pantograph voltage profile. This paper aims to optimize the energy management, location, and size of stationary super-capacitor ESSes simultaneously and obtain the best economic efficiency and voltage profile of metro systems. Firstly, the simulation platform of an urban rail power supply system, which includes trains and super-capacitor energy storage systems, is established. Then, two evaluation functions from the perspectives of economic efficiency and voltage drop compensation are put forward. Ultimately, a novel optimization method that combines genetic algorithms and a simulation platform of urban rail power supply system is proposed, which can obtain the best energy management strategy, location, and size for ESSes simultaneously. With actual parameters of a Chinese metro line applied in the simulation comparison, certain optimal scheme of ESSes’ energy management strategy, location, and size obtained by a novel optimization method can achieve much better performance of metro systems from the perspectives of two evaluation functions. The simulation result shows that with the increase of weight coefficient, the optimal energy management strategy, locations and size of ESSes appear certain regularities, and the best compromise between economic efficiency and voltage drop compensation can be obtained by a novel optimization method, which can provide a valuable reference to subway company.

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 antidisturbance 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.