Engine power smoothing energy management strategy for a series hybrid electric vehicle

Hybrid electric vehicles exploit energy production and energy storage systems to achieve improved fuel economy with respect to conventional powertrains. In order to maximize such improvements, advanced control strategies are needed for deciding the amount of energy to be produced and stored. In this paper we propose an approach for energy management of a series hybrid electric vehicle (SHEV). This approach focuses on maximizing the pointwise powertrain efficiency, rather than the overall fuel consumption. For a given power request the steady state engine operating point is chosen to maximize the efficiency. A control algorithm regulates the transitions between different operating points, by using the battery to smoothen the engine transients. Due to the constrained nature of the transient smoothing problem, we implement the control algorithm by model predictive control. Experimental testing on the UDDS cycle shows improved fuel economy with respect to two baseline strategies.