Efficiency maximizing and charge sustaining supervisory control for series hybrid electric vehicles

A supervisory control system (SCS) that maximizes the overall powertrain efficiency of a series hybrid electric vehicle (HEV) is developed. A novel approach of formulating the overall power efficiency which considers the idling losses of the engine and also characterizes separately the charging and discharging efficiencies of the battery, is proposed. These features allow the mode of direct power transfer from engine to battery to be included in the optimization. In turn, this enables the formulation of an optimization problem with a charge-sustaining scheme for improved control. A dynamic model of a series HEV is used in the development and testing of the SCS. Simulations with standard driving cycles demonstrate the significant improvement in fuel economy and battery charge sustaining of the designed Efficiency Maximizing and Charge Sustaining Map (EMCSM) over a Thermostat control scheme.