Research on multi-points working strategy and multi-objective optimization for the APU system of range-extended electric vehicle

The optimization design of auxiliary power unit (APU) working mode for range-extended electric vehicle (R-EEV) was carried out from a multi-objective perspective to achieve the optimal energy allocation between the APU and battery. Firstly, a multi-points working strategy (MPWS) was proposed, taking the number of APU constant speed operating points and the power range at this speed as the optimized objects. And the unification and regularity of the APU operating mode design was realized. And the effects of APU different operating modes on energy consumption, emissions, and battery life are studied from a multi-objective perspective, which is solved by multi-objective variable weight analysis. Then, the multi-objective optimization analyses are carried out based on weight coefficient matrix. The proposed MPWS showed good performance, and the power allotment between APU and battery can be regulated to enhance APU operation at optimal points, while concurrently minimizing energy loss due to secondary charging and APU dynamic switching times ultimately. APU different operating modes of N csop = 3 and N csop = 4 modes have lower sensitivity to weight coefficients, which is conducive to making engineering decisions for the strategies. Finally, the simulation and experimental results thoroughly indicated that economy improvement, emission reduction, and battery life enhancement of R-EEV were kept in balance effectively under the control of proposed MPWS. The design and the related conclusions obtained from the study lay the research foundation for the implementation of the intelligent mode-switching based energy management strategy for optimal energy allocation.