Power and Energy Management of a Dual-Energy Source Electric Vehicle - Policy Implementation Issues

This paper offers a new design-oriented approach to address implementation issues associated with a power and energy management policy for an electric vehicle (EV) powered by a dual-sourced system. A special sequential decision process, which determines the power split ratio and reference energy levels of the dual battery-ultracapacitor sources, has been formulated as a state transition mechanism. Experimental results from a test vehicle were used to validate simulation models of tractive power demands and battery behavior

I. Introduction

Continuous and pulsed power requirements are common for electric vehicle applications. These requirements, when met by a single sourced system, are closely related with one another. To meet both usually results in an over-sized power storage system. With a dual-source, it is possible to decouple the requirements leading to both performance and weight advantages. The success of implanting a dual-source system, however, depends on how the power and energy flow between the two sources is managed during the drive cycle. Here, we use a battery-ultracapacitor system to create an energy storage system with the high energy density attributes of batteries and the high power density of ultracapacitors. In essence power and energy management policies for such dual energy storage systems in Electric Vehicles (EV) involve determining the proportional power split between two sources as well as the optimal State of Charge (SoC) throughout the drive cycle. In effect, it represents a sequential decision process over the mission profile. Figure 1: Power split between two energy sources in an EV