Plug-in Hybrid Electric Vehicle Control Strategy: Comparison between EV and Charge-Depleting Options

The U.S. Department of Energy (DOE) has invested considerable research and development (R&D) effort into Plug-in Hybrid Electric Vehicle (PHEV) technology because of the potential fuel displacement offered by the technology. DOE’s PHEV R&D Plan [1], which is driven by the desire to reduce dependence on foreign oil by diversifying the fuel sources of automobiles, describes the various activities required to achieve the goals. The U.S. DOE will use Argonne’s Powertrain Systems Analysis Toolkit (PSAT) to guide its analysis activities, stating, “Argonne’s Powertrain Systems Analysis Toolkit (PSAT) will be used to design and evaluate a series of PHEVs with various 'primary electric' ranges, considering all-electric and charge-depleting strategies.” PSAT was used to simulate three possible chargedepleting (CD) PHEV control strategies for a power split hybrid. Trip distance was factored into the CD strategies before the cycle was started. The results are examined in this paper to determine if any of the three strategies could reduce the power split configuration’s fuel consumption beyond what a simple all-electrical strategy followed by a charge-sustaining (CS) strategy could afford. The results show that the improvements for this configuration are small and depend on the ratio of the engine efficiency when operating in CS mode to the engine efficiency when operating in CD mode.