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.

With its large capacity, the total urban rail transit energy consumption is very high; thus, energy saving operations are quite meaningful. The effective use of regenerative braking energy is the mainstream method for improving the efficiency of energy saving. This paper examines the optimization of train dwell time and builds a multiple train operation model for energy conservation of a power supply system. By changing the dwell time, the braking energy can be absorbed and utilized by other traction trains as efficiently as possible. The application of genetic algorithms is proposed for the optimization, based on the current schedule. Next, to validate the correctness and effectiveness of the optimization, a real case is studied. Actual data from the Beijing subway Yizhuang Line are employed to perform the simulation, and the results indicate that the optimization method of the dwell time is effective.

The use of supercapacitors (SCs) to store regenerative braking energy from urban rail trains is able to achieve a good energy saving effect. This paper analyzes the current balance method of stationary energy storage devices (ESDs). At the beginning of the paper, the mathematical model of the DC traction power system, which includes trains, ESDs and traction substations, is established. Next, based on this, the SC state-based control strategy (SCSCS) is proposed, which can adjust the charging voltage of the ESD according to the SC voltage and current, then the charging current of the ESD can be reasonably distributed under the voltage difference of ESDs, and the SC voltage and current stress can be reduced. In order to determine the optimal controlling parameters, the optimization model is proposed and solved by the genetic algorithm. The analysis of the case study also shows the effectiveness of the proposed control strategy and optimization algorithm. Finally, the rationality of the proposed strategy is verified by experiments.