An Online Supercapacitor Capacitance Labeling Method Based on Tram Field Data

Supercapacitors are widely adopted in rail transit due to their high power density and long cycle life. To estimate the state of health and predict the remaining useful life of the onboard supercapacitors in transportation systems, this paper proposes an online capacitance labeling method for supercapacitors used in trams based on the field data. This method screens the supercapacitor discharging process for appropriate discharging fragments and identifies the capacitances associated with these applicable fragments by applying the gradient descent method to an equivalent circuit model of the supercapacitor. The supercapacitor capacitance is labeled on a monthly basis by averaging all the identified fragment capacitances within the month. A case study is conducted with the field data of a tram for the period of December 2018 to December 2023.