Modelling and simulation of repeated charging/discharging cycles for selected nickel-cadmium batteries

The main aim of the paper is to present a developed methodology of simulation of the energy efficiency of a selected energy storage unit. The authors focused their actions on batteries that could be the base for an energy storage system possible to apply in a modernized hybrid-shunting locomotive. Three different nickel-cadmium batteries were selected as representatives for the study. Simulation was focused on repeated cycles of charging and discharging the batteries. The simulation model generally consists of three main components: a specified load cycle, a dynamic model of the DC electrical machine and a model of the Ni-Cd battery. The input data for the battery model is based mostly on the parameters provided by the manufacturer data sheets. However, an internal resistance had to be measured for each battery. Conducted simulations provided information about the electromotive force, state of charge, an average efficiency of the battery, as well as the temperature changes during the cycle. The proposed approach to the battery simulation can be also applied for the loading cycles similar to those that occur during the actual operation of the locomotive. The current study is a part of the project focused on modernization of the diesel-electric shunting locomotive to the hybrid one.