Design and performance analysis of a novel powertrain scheme for plug-in hybrid electric vehicles

This paper proposes a novel P2 hybrid transmission scheme integrating a converging-differential hydro-mechanical torque converter. This transmission enables continuous speed and torque regulation, allowing the hybrid system to achieve various operating modes with a single electric machine. A prototype was fabricated and the speed relationships among the sun gear, carrier, and ring gear in the hydro-mechanical torque transmission mode were experimentally validated. A system-level simulation model was established based on the transmission scheme. The simulation results show that, compared with a conventional dual-motor hybrid system, the proposed single-motor scheme achieves most of the required functions while delivering superior low-speed dynamic performance: the 0–50 km/h acceleration time is improved by 67.7%, the 0–100 km/h acceleration time is improved by 31.79%, and the maximum climbing gradient is increased from 0.10 to 0.35. These improvements are accompanied by a slightly higher fuel consumption under the WLTC cycle, while the electric machine count is reduced.