Phase characteristic control strategy for the front powertrain of series mild HEV considering dynamic response of engine-generator set

Abstract

The front powertrain of series mild hybrid electric vehicles (HEVs) often struggles to meet the vehicle’s instantaneous power demand due to insufficient dynamic response of the engine-generator set (EGS) and battery power limitations, leading to poor dynamic characteristics and fuel economy. To address this issue, a phase characteristic control strategy for the front powertrain is proposed. It establishes a four-quadrant working plane for fuel-electric dual-source power output and divides it into twelve phase domains based on power flow, encompassing all possible operating modes of series mild HEVs. Considering the lag effect of the turbocharged engine, phase domain switching strategies are proposed for transient operating conditions, and the phase trajectory laws of the front powertrain are derived. Simulations conducted to validate the strategies show that, compared to the baseline, the proposed strategies reduce acceleration time by 8.9 % and 42.6 % during acceleration from 0 to 32 km/h, and decrease equivalent fuel consumption by 5.4 % and 7.0 %, respectively. Under braking condition from 40 to 20 km/h, the phase domain switching strategy improves braking energy recovery by 41 % compared to the baseline, with the EGS exhibiting improved dynamic response after braking.