Proposals of Evaluation Method and Control Selection Policy for Plug-in Hybrid Vehicles Based on the Distance Traveled Dependence of Carbon-Reducing Effect
Authors:   Waseda Univ., JAPAN, Pei Shuai , Yang Wei-hsiang , Kamiya Yushi , Daisho Yasuhiro 
Published: April 2022

As a countermeasure for the global environment and energy problems, vehicles are being electrified. This paper is focusing on plug-in hybrid vehicles (PHVs), which is a type of electric vehicles. PHVs have both two energy sources: externally charged power and fuel. PHVs initially operate in the charge-depleting mode (CD mode), where the vehicle is driven primarily by the battery power until a preset minimum level of state of charge (SOC) is reached. Then the vehicle switches into the charge-sustaining mode (CS mode), where the vehicle travels by consuming fuel only. In CD mode, there are two control policies known as all-electric control (AE control), which is that vehicles are driven by electric power only, and blended control (BLD control), which is that vehicles are driven using not only electric power but also fuel in the time an assistant is given by engine. Therefore, there exist multiple driving modes and control policies, and the combinations of them are also various. Furthermore, since the environmental performance of PHVs varies greatly between two different driving modes, the average performance from the start point to the end point also varies greatly depending on the distance between the start point and the end point. As a conclusion, it is extremely complicated to evaluate the environmental performance of PHVs accurately. In the previous paper of our research group, we were focusing on low-carbon effect of PHVs within considering both energy sources. Furthermore, it was reported that the low-carbon effect of PHVs depending on traveled distance was described by mathematical equations within seven PHVs evaluation indices released by the government of Japan in 2009. Moreover, based on the mathematization of the distance traveled dependence of carbon-reducing potential of PHVs, several control policies and evaluation indices for PHVs are proposed. In this paper, a series type and a parallel type plug-in hybrid vehicle simulator are established to validate the propositions made in the previous paper. First, the characteristics of the distance traveled dependence of PHVs are confirmed. One of the characteristics is the performance reversal cross-point between AE to CS mode and BLD to CS mode, which means by using engine high-efficiency operation BLD control, there is a moment that the quantity of CO2 emission is reversed comparing to the AE to CS control. And the other one is when the driving mode is switched into CS mode from CD mode where AE or BLD control is adopted, the difference of the CO2 emission quantity between each other presents a constant value, which is defined as ∆CO2. Secondly, the appropriateness of the proposed control selection policy of AE and BLD control based on the performance reversal cross-point is confirmed. Thirdly, the proposed optimal BLD control whose CD range is equal to planned travel distance is confirmed by the equations established and simulation results. Finally, the usefulness of the indicator BCPI (blended control performance indicator) we proposed, which can evaluate the carbon-reducing effect of BLD control simply, is also verified.