Traction Power Calculation-based Capacity Allocation Optimization Of Trackside Energy Storage Devices Along Urban Rail Transit Lines

As the operating mileage and train density of urban rail transit continue to increase,the overall energy consumption of the system also increases.The global call for energy conservation and emission reduction,as well as the national policy of the "Carbon peaking and carbon neutrality",have put forward requirements for the energy conservation of urban rail transit systems.In order to achieve the goal of reducing the total energy consumption of the urban rail transit system,this paper considers installing trackside energy storage devices next to the urban rail transit lines to improve the recovery rate of regenerative braking energy,and establishes an optimization model of energy storage device capacity allocation with the goal of minimizing the total output energy consumption of traction substations.Then,based on the actual data of a certain line and from the perspective of planning,the optimization scheme of the capacity allocation of the trackside energy storage devices is obtained to verify the validity of the model.The research content of this paper mainly includes the following three aspects.Firstly,this paper establishes a calculation model for DC traction power supply for urban rail transit,including a circuit physical model equivalently modeled by various parts of the DC traction power supply system,and a mathematical calculation model composed of a train traction calculation module,a DC traction power supply calculation module and an energy storage device charging and discharging calculation module.Specifically,the train traction calculation module obtains the position and power information of trains at each moment.The DC traction power supply calculation module uses the Newton iteration method to calculate the node voltage of each traction substation and each train in the traction power supply system.The last module calculates the charging and discharging current of the energy storage devices at each moment according to the traction network voltage.Using the idea of simulation iteration to solve the mathematical calculation model,the total energy consumption of the urban rail transit traction substation is obtained.Secondly,according to the DC traction power supply calculation model,an optimization model of the energy storage device capacity allocation is constructed.The energy storage device is composed of supercapacitor cells first in series and then in parallel.The optimization model takes the parallel number of the supercapacitor series modules in the energy storage device as the decision variable,and takes the minimum energy consumption of the traction substations as the target.At the same time,the upper limit of the total capacity of all energy storage devices is set,and the tabu search algorithm is used to solve the problem to obtain the optimal solution.Finally,a case study is carried out based on the relevant data of a certain subway line,and a comparative analysis of different energy storage device capacity allocation schemes is carried out.The research shows that the energy storage device capacity allocation optimization scheme can achieve better energy-saving effect with less capacity of energy storage devices.From the perspective of planning and design,it is possible to fully consider various possible operating conditions in the initial,short-term and longterm construction of urban rail transit,and comprehensively select the energy storage device capacity allocation scheme.Through the sensitivity analysis of the upper limit of the total capacity energy storage devices,it is found that the total energy consumption of the traction substations in the power supply system first increases slightly and then gradually decreases until it becomes stable as the upper limit constraint value of the total capacity of energy storage devices increases continuously until there is no upper limit constraint.