Research On Optimal Allocation Of Capacity And Economic Evaluation Method Of Hybrid Energy Storage System For Electrified Railway

The energy consumption problem of Chinese electrified railways has become increasingly serious with the rapid growvement of the operating mileage.As the largest single load of the power grid,electrified railway’s electricity bill has become the main operating expenditure.With the widespread use of AC-DC-AC electric locomotives and EMUs,the regenerative braking energy(RBE)of Chinese electrified railways returning to the power grid is also increasingly abundant.If the utilization rate of RBE in the traction power supply system can be improved,it can effectively reduce railway power consumption,improve railway operation economy,and help achieve the "dual carbon" goal.The hybrid energy storage system(HESS)combines advantages of various energy storage medias,has bidirectional power throughput capability,can realizes the time-space translation of electric energy,and can effectively realizes the recovery and utilization of RBE.For the above reasons,this paper focuses on the application of the HESS in electrified railways,and the following research work is carried out:(1)The scheme of electrified railway HESS based on railway power conditioner(RPC)and its energy management strategy are studied.Firstly,based on the measured load data,it is analyzed that the load of the electrified railway has the characteristics of daily periodic change,strong fluctuation,rich regenerative braking energy,and unbalanced load of the two power supply arms;On this basis,a HESS scheme with RPC as grid-connected converters,supercapacitors and lithium iron phosphate batteries as energy storage media is studied.The energy management strategy of HESS considering peak shaving and valley filling is established to realize peak shaving and valley filling of electrified railway load.(2)The optimal economic capacity allocation method for the whole life cycle of the HESS of electrified railway is studied.Firstly,according to the current railway electricity tariff policy in China and the technical effect of the HESS,the investment and benefits brought by the HESS are summarized,and then a life cycle economic optimization model of the electrified railway hybrid energy storage system is established;On this basis,taking the HESS’s charging and discharging threshold and energy storage capacity configuration parameters as the optimization variables,and taking the maximum net income in the whole life cycle as the optimization goal,the improved particle swarm algorithm is used to optimize the HESS;Finally,combined with the measured data of the traction substation,the optimization results of the example and the corresponding operation of the HESS are simulated and analyzed.(3)The comprehensive evaluation system and evaluation method of electrified railway energy storage system are studied.First,the application effects of energy storage systems are classified into three categories: economic benefits,social benefits,and technical indicators,and each category of effects is evaluated by one or more secondary indicators;Then,comprehensively considering the subjectivity and objectivity of the evaluation process,a multi-index evaluation method that combines the analytic hierarchy process(AHP)and the technique for order preference by similarity to an ideal solution(TOPSIS)is proposed.Finally,combined with the cases of different electrified railway energy storage systems,the feasibility of the proposed evaluation system and evaluation method is verified.(4)An analysis platform for electrified railway energy storage system is designed.According to the location and capacity requirements of the electrified railway energy storage system in practical application,an electrified railway energy storage system analysis platform is constructed,which includes four modules: data analysis of traction substations,energy storage system capacity configuration,energy storage system effect analysis,and energy storage system scheme evaluation.Then,the design ideas and application methods of the platform are introduced,and the practicability of the platform is verified through the corresponding examples of each module.Finally,the research content and shortcomings of this paper are summarized,and the next research direction is prospected.