Convex modeling for optimal battery sizing and control of an electric variable transmission powertrain

Journal article, 2019

Hybrid Electric Vehicles are being considered a convenient intermediate product in the conversion process from conventional to pure electric vehicles, due to their compromise on cost, fuel consumption, and driving range. Convex modeling steps for the problem of optimal battery sizing and energy management of a plug-in hybrid electric vehicle with an electric variable transmission are presented. Optimal energy management was achieved by a switched model control, with driving modes identified by the engine on/off state. In pure electric mode, convex optimization was employed to find the optimal torque split between two electric machines, to maximize powertrain efficiency. In hybrid mode, optimization was carried out in a bilevel program. One level optimizes speed of a compound unit that includes the engine and electric machines. Another level optimizes the power split between the compound unit and the battery. The proposed method is used to minimize the total cost of ownership of a passenger vehicle for a daily commuter, including costs for battery, fossil fuel and electricity.