Design and Modelling of Ultra-Capacitor Based Hybrid Energy Storage System in Electric Two-Wheeler for Indian Driving Cycle

Abstract

EV batteries often suffer from the incapability to deliver quick transient currents keeping temperature in its permissible level. The characteristic feature of low power density of battery can be overcome by increasing its rating, however that ends up in increasing the weight of the vehicle which ultimately diminishes its performance. At the same time EDLC (Electrical Double Layer Capacitor) commonly known as ultra-capacitors, possess higher power density despite of having energy storage limitations. Hence transient high power demand during acceleration and hill climbing can be met by hybridizing the battery with ultra-capacitors. This paper elucidates the design and modelling of ultra-capacitor-based Hybrid Energy Storage System (HESS) in electric two-wheeler under Indian driving condition. The HESS which is modelled in this paper consists of a lithium-ion battery, taken as main energy source, and an ultra-capacitor, taken as auxiliary energy source. The proposed HESS is designed with a peak power rating of 2 kW. Both the energy sources are interfaced through a Bi-Directional DC-DC Converter (BDC). The load is represented by a 48 V DC bus which constantly charges and discharges according to the power command. A well-defined control algorithm is proposed to manage the power delivery from the source to the load. Energy hybridization enhances battery life as it can be operated within the permissible limits of temperature. Simulations are performed in MATLAB Simulink environment to analyse the operation of HESS.