Control of hybrid energy storage for extended battery life in electric vehicles

Abstract

This paper aims at the development of a power split control for energy management of multiple energy sources in a typical Electric Vehicle (EV) drive. A source selecting switching circuit is developed so as to connect either battery, the high energy density source or ultracapacitor (UC), the high power density source to a 48V, 60W traction DC motor drive. Power split control is designed based on the rate of rise of motor drive power demand. This rate of demand, if makes the battery current to exceed its maximum limits, then the power split control will switch the high power source to deliver the load demand instead of the battery. A boost converter receives one of these sources and acts as the drive for the traction motor with a closed loop control to accomplish the speed tracking ability. A typical vehicle drive cycle is used for testing the developed converter, the motor drive system and its associated control in MATLAB simulation. Further, experimental validation is carried out in hardware circuit with Arduino evaluation board used for implementation of both the power split control as well as the speed control algorithms. Various test conditions depicting typical Electric Vehicle drive cycles were formulated to test the hardware system. The ultracapacitor is observed to support the traction motor drive during the high rate of power demand periods in the vehicle drive cycle. The simulation as well as the experimental results for various speed profiles were presented and analyzed.