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A vehicle control system basing on instantaneous energy optimization and series regenerative braking strategy was successfully developed for a fuel cell hybrid bus. The control system includes a vehicle control unit and other warning and measure systems. The control algorithm contains several blocks: start/stop, motor mode switch, diagnose and energy management. The movement of vehicle is divided into two parts: A) no braking process and B) braking process. An instantaneous equivalent hydrogen consumption optimization strategy was applied in process A. And in process B the braking energy was recovered partly so that the vehicle longitudinal dynamics would not be greatly affected. As a result, the fuel economy is improved from 9.6kg/100km to 7.9kg/100km in “China typical city bus cycle”.

The lithium-ion battery plays an important role in saving energy and lowering emissions. Many parameters like temperature have an influence on the characteristic of the battery and this phenomenon becomes more serious in an electric vehicle. In this paper, the application of a boost DC/DC converter to the battery system of high power for online AC impedance identification is proposed. The function of the converter is to inject a current excitation signal into the battery at work and the normal output current is drawn by a load. Through analyzing the average state space equations and deriving the small signal model of the converter, the gain function is deduced of the fluctuated current signal against the fluctuated duty cycle which controls the converter. The control algorithm is designed and the system model is verified using Matlab/Simulink with respect to the disturbance current signal generation, the gain function and its variation with frequency range.