Adaptive control of a hybrid power system in electric vehicles

The external characteristics of the bi-directional power converter were designed for an electric vehicle's hybrid power system in which an ultra-capacitor group is connected to a power battery group via the converter. Based on the measurement of the discharging current of the battery group, both of the working mode and the current of the ultra-capacitor were adaptively controlled. The model of the external characteristics of the bi-directional power converter was founded, revealing the quantitative relation between the battery current and the ultra-capacitor current. Then, the control circuit of the bi-directional power converter was developed. The results of the experiments showed that the peak current of the battery in this hybrid power system was 60% lower than that of the system current, which is advantageous to enhancing the battery life time.