Energy management optimization for hybrid electric vehicles using modular range extenders: a case study on linear engine generator

Modular power systems are improving hybrid vehicle performance, which is an emerging trend in the automotive industry. This research proposes a novel energy management strategy for the hybrid vehicles applying modular range extenders. This research uses free-piston linear generator (FPLG) as range extender to illustrate the feasibility of the proposed control strategy. Considering control complexity simplification and system energy optimization, the operating points of individual units are determined using efficiency and power as metrics, thereby constructing a modular FPLG set. In the formulation of the energy management strategy, the startup losses of the FPLG set are primary considered. Combined with fuel consumption and battery SOC control costs, a nonlinear integer optimization problem is constructed. By analyzing and optimizing the effect of FPLG startup losses control weight on power system, better control performance is obtained. Finally, compare the efficiency and fuel economy of the FPLG set with a conventional range extender, and verify the effectiveness of the proposed strategy under several typical operating conditions. The results show that: compared with the conventional range extender, the FPLG set can save more than 8 % of fuel consumption under the whole cycles; Compared with the baseline strategy, the integer optimization-based control strategy can significantly reduce the number of startup operations of the FPLG set by more than 60 %, realizing a reduction of fuel consumption by about 15 %.