Effects of Initial SOC of 270-Volt Battery on Operating Performance of Gasoline Engine and Electric motor in a Parallel Hybrid Vehicle under IM240 Driving Cycle Mode

Abstract

Next-generation vehicles are under energy and environmental pressure to increase fuel economy and reduce emissions of green-house-gases (GHG) such as carbon dioxide, which is the main cause of global warming, while maintaining the performance and drivability characteristics of conventional internal combustion engine (ICE) automobiles. So, hybridization of both conventional ICE and electric motor powertrain systems hold great promise for environmentally friendly vehicles (EFV) to meet stringent CO2 regulation and fuel economy requirements. This paper presents the effects of the initial state of charge (SOC) stored in the vehicle’s battery on tractive propulsion characteristics as vehicle drivability performance that is obtained from both ICE and an electric motor simultaneously. Especially, the battery management system (BMS) plays a key role in a hybridized system based on an electric device. And a regenerative braking system recovers kinetic energy from braking and uses it to recharge the battery. In this study, in order to investigate the effects of various initial SOCs in a parallel hybrid gasoline-electric vehicle (HEV), an experiment was carried out on a vehicle chassis dynamometer with IM240 vehicle driving mode and a CAN protocol analyzer to collect data from a full HEV. A unique hybrid electric signal processor was designed to monitor the operational state of the ICE including fuel injection duration, hybrid starter-generator (HSG) and propulsion motor which depend on the initial SOC. The amount of energy recovered through the regenerative braking system was measured to investigate the collect rates of currents. The results show that the initial SOC stored in the battery causes big differences in the electric current balance in hybrid operating mode, and that careful coordination of ICE and motor is necessary to achieve vehicle propulsion capacity as well as to maintain the battery SOC at a reasonable level.