Document Type

Technical Report

Date of this Version

2-2014

Comments

@TECHREPORT{TR-2014-ESE01, AUTHOR = {Yash V. Pant and Truong X. Nghiem and Rahul Mangharam}, TITLE = {Peak Power Control of Battery and Super-capacitor Energy Systems in Electric Vehicles}, INSTITUTION = {Department of Electrical and Systems Engineering, University of Pennsylvania}, MONTH = {February}, YEAR = {2014}, }

Abstract

Hybrid energy systems consist of a load powered by a source and a form of energy storage. Systems with mixed energy supply find applications in the electric grid with renewable and non-renewable sources, in mission critical systems such as Mars rovers with rechargeable and non-rechargeable batteries and low-power monitoring systems with energy harvesting. A general problem for hybrid energy systems is the reduction of peak power consumption to ensure cost-efficient operation as peak power draws require additional resources, adversely affect the system reliability and storage lifetime. Furthermore, in some cases such as electric vehicles, the load dynamics are fast, not perfectly known a priori and the computation power available is often limited, making the implementation of traditional optimal control difficult. This paper aims to develop a control scheme to reduce the peak power drawn from the source for hybrid energy systems with limited computation power and limited load forecasts. We propose a scheme with two control levels and provide a sufficient condition for control of the different energy storage/generation components to meet the instantaneous load while satisfying a peak power threshold. The scheme provides performance comparable to Model Predictive Control, while requiring less computation power and only coarse-grained load predictions. As a case study we implement the scheme for a battery-supercapacitor system in an electric vehicle with real world drive cycles to demonstrate the low execution time and effective reduction of the battery power (hence temperature), which is crucial to the lifetime of the battery.

Keywords

Peak power reduction, hybrid energy storage systems, electric vehicles

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Date Posted: 21 March 2014