Hybrid Energy Storage System for Regenerative Braking Utilization and Peak Power Decrease in 3 kV DC Railway Electrification System

This paper proposes the sizing optimization method and energy management strategy for stationary hybrid energy storage system dedicated to DC power supply system. The hybrid energy storage consists of two modules – supercapacitor, mainly dedicated to regenerative energy utilization and electrochemical battery, aimed to peak power reduction. It is shown that the parameters of both modules could be sized independently. The supercapacitor module parameters are sized, based on the results of simulation determining the regenerative power, resulting limited catenary receptivity. The simulation model of DC electrification system is validated by comparing the results of simulation with the measurements of 15-min average power in 24-hour cycle as an average values of one year. The battery module is sized based on the statistical data of 15-min substation power values occurrences. The battery energy capacity, its maximum discharge C-rate and the conditions determining its operation are optimized to achieve the maximum ratio of annual income resulting from peak power reduction to annual operating cost resulting from battery aging process and total life cycle. The case study prepared for typical 3 kV DC substation with mixed railway traffic shows that peak power could be reduced by ~ 1 MW, giving ~ 10 years of payback period of battery module installation, while the energy consumption could be decreased by 1.9 MWh/24 h, giving the payback period of supercapacitor module installation ~ 7.5 years. The payback period of the whole energy storage system (ESS) is ~ 8.4 years.