Energy flow analysis of an electric city bus based on wavelet transform with Mallet prolongation

In this paper, we propose a Haar wavelet with Mallet prolongation energy management strategy, a pure electric city bus produced by CENS Energy Tech Co, Ltd with a hybrid energy storage system that combines a lithium battery with an ultracapacitor is tested and modeled under a MATLAB-CRUISE joint simulation environment based on the experiments. In verifying its validity, the proposed method is compared with the common rule-based control strategy from the charging and discharging characteristics of the battery, the feedback efficiency of the ultracapacitor, and the overall system efficiency during China City Road Cycle. The results show in the proposed method that state of charge of the battery is more stable avoiding from the peak current shock, the battery life has been protected effectively, the ultracapacitor has been utilized more fully, and the vehicle performance is better for the tracking performance and control flexibility than the rule-based control strategy.