Power distribution optimization of a fully active hybrid energy storage system configuration for vehicular applications

Abstract

As an effective solution to limitations of vehicle-mounted single-battery energy storage system, the super-capacitor (SC)/battery hybrid energy storage system (HESS) is a research topic that is receiving more and more attention and emphasis from scientific research institutions in various countries. Despite its current widespread recognition in vehicle field, low energy utilization and low work efficiency under the variable working conditions of vehicle particularly limit its practical application and popularity. The power distribution optimization is critical to obtain a HESS with superior performance such as good reliability and high efficiency. This work presents a variable voltage SC/battery HESS configuration based on series-parallel switching technology of SCs, which can realize multiple working modes of the HESS to meet the needs of complex and variable working conditions of vehicle, and increase the power output range of the HESS. Taking the proposed HESS as application object, an energy efficiency model of the HESS is established, as well as an optimization model with energy efficiency maximization as the optimization goal. Power distribution optimization methods based on Genetic Algorithm (GA) and Gray Wolf Algorithm (GWA) respectively are proposed, and compared to fixed rules-based and fuzzy-based control strategies. The optimization algorithms-based methods can almost obtain the highest energy efficiency (from 91% to 87%) within the entire power demand range (from 100 W to 500 W), have obvious advantages in comparison of several other methods. The efficiency in the whole New European Driving Cycle (NEDC) driving condition exceeds 85%, and in the most periods of this driving condition exceeds 90%. The results clearly demonstrate validity and reliability of the power distribution optimization methods proposed in this paper. This work aims to solve the problem concerning the optimal power distribution based on energy efficiency maximization of HESS, and provide solution for improving the power output capacity and energy utilization of HESS. We firmly believe that this work has considerable theoretical significance and engineering application value for the promotion of HESS.