Fuel Economy Optimization for Parallel Hybrid Vehicles with CVT

A new fuel economy optimization method for parallel hybrid electric vehicles with continuously variable transmission( CVT) is proposed in this paper. The method maximizes overall system efficiency while meeting desired performances. Firstly, effective specific fuel consumption (ESFC) is defined as effectively consumed fuel per output power-hour from a hybrid propulsion system, in which battery output power is transformed into an equivalent amount of fuel. Hence, hybrid optimal operation line(HOOL) is derived based on ESFC as optimal operation line(OOL) is found based on specific fuel consumption( SFC) in a conventional internal combustion engine(ICE) vehicle with CVT. From HOOL, optimal combinations of control variables, CVT gear ratio, motor torque and engine throttle, are obtained versus vehicle velocity, battery state of charge and required power. A simulation study with the proposed optimization method is performed to prove its validity.