Energy Management System within Electric Vehicles Using Ultracapacitors: An LQG-optimal-control-based Solution

This paper proposes a frequency-separation-based energy management inside of electric vehicles using ultracapacitors as high-energy-density auxiliary power sources. The power sources are enabled to share the stochastically-variable load according to their features: low-frequency variations of the required power are ensured by the main source, the battery, whereas high-frequency variations are provided by the ultracapacitor. An LQG-based optimal control structure is designed and coupled with a gain-scheduling law to cover the entire operating range; it conveniently trades off the load regulation performance and the variations of battery current, in order to improve the battery reliability and lifetime. MATLAB®/Simulink® numerical simulations reveal good results for strongly variable driving cycles.