Embedded electric power system with fuzzy-logic supervision for vehicular applications

Hybrid electric vehicles and full electric vehicles are becoming a viable alternative to gasoline or diesel powered vehicles. Four main factors are contributing to this evolution: oil price, pollution, greenhouse effect and advances in electrochemical energy storage. All major car manufacturers are developing projects in this area. Until now, the full electric vehicles available on the market have autonomy of about 100 to 150 km, limited by the energy stored in the electrochemical battery. The battery is the most expensive part of the electric vehicle, and has also a limited lifetime. This paper presents a solution to enhance the battery lifetime, by blocking the short charging energy pulses (usually, submitted to the battery) retrieved from the electric machine, mainly when the vehicle is braking. This is obtained with the help of supercapacitor energy storage device. The solution developed is a fuzzy-logic supervisor that imposes the battery and supercapacitor powers in order to limit the number of charge/discharge cycles of the electrochemical battery. Experimental tests and results validate the proposed supervision technique.