Comparison of Dynamic Programming-based Energy Management Strategies Including Battery Life Optimization

This paper presents two optimal energy management strategies for a parallel hybrid electric vehicle (HEV) equipped with a continuously variable transmission (CVT). The goal for both strategies is to try to minimize fuel consumption while maintaining the state of charge (SOC) of the battery within prescribed limits, as well as to minimize the battery capacity loss and extend its life. The first strategy, which is referred to as sequential optimization, operates the CVT along the engine optimal operating line (OOL) and then uses dynamic programming to determine the optimal torque split between engine and electric machine based on the CVT ratio. The second strategy, which is referred to as system optimization, solves the optimal CVT ratio and torque split simultaneously by dynamic programming. Comparison analysis is conducted and simulation based results show that significant improvements can be achieved on both fuel economy and battery aging by the system optimization.