Online Parameter Identification of Ultracapacitor Models Using the Extended Kalman Filter

Lei Zhang,Fengchun Sun,Zhenpo Wang,David Dorrell

doi:10.3390/en7053204

Abstract

Ultracapacitors (UCs) are the focus of increasing attention in electric vehicle and renewable energy system applications due to their excellent performance in terms of power density, efficiency, and lifespan. Modeling and parameterization of UCs play an important role in model-based regulation and management for a reliable and safe operation. In this paper, an equivalent circuit model template composed of a bulk capacitor, a second-order capacitance-resistance network, and a series resistance, is employed to represent the dynamics of UCs. The extended Kalman Filter is then used to recursively estimate the model parameters in the Dynamic Stress Test (DST) on a specially established test rig. The DST loading profile is able to emulate the practical power sinking and sourcing of UCs in electric vehicles. In order to examine the accuracy of the identified model, a Hybrid Pulse Power Characterization test is carried out. The validation result demonstrates that the recursively calibrated model can precisely delineate the dynamic voltage behavior of UCs under the discrepant loading condition, and the online identification approach is thus capable of extracting the model parameters in a credible and robust manner.

Highlights

IntroductionThe performance of electric vehicles is heavily influenced by their energy storage systems (ESSs)
In order to address serious concerns over energy sustainability and environmental impact, governments, the automotive industry, and academia are endeavoring to expedite a paradigm shift to a green transportation system [1]
This paper presents an online model identification method for a UC model based on the well-known

Summary

Introduction

The performance of electric vehicles is heavily influenced by their energy storage systems (ESSs). Ultracapacitors, known as supercapacitors or double-layer capacitors, have high power density, low internal resistance, high efficiency, and exceedingly long cycle life, while possessing the merits of wide operating temperature range and fast charging [9,10]. Their drawbacks, such as low energy density and relative high price, limit the possibility of deploying UCs as the single energy storage for electric vehicles.

Methods

Results

Conclusion