Optimization of Speed Fluctuation of Internal Combustion Engine Range Extender by a Dual Closed-Loop Control Strategy 2021-01-0782

With the increasing concern on environmental pollution and CO₂ emission all over the world, range-extended electrical vehicle (REEV) has gradually got more attention because it could avoid the mileage anxiety of the battery electrical vehicles (BEV) and get high energy efficiency. Nevertheless, NVH performance of internal combustion engine range extender (ICRE) is a critical problem that affects the driving experiences for REEV. In this paper, a two-cylinder PFI gasoline engine and a permanent magnet synchronous motor (PMSM) are coaxially mounted to run as an ICRE. The ICRE control system was established based on Compact RIO hardware and LabVIEW, who has the functions of the intake throttle PID closed-loop control, autonomous ICRE operation control, and speed PID closed-loop control. In this paper, the gasoline engine was first driven to the idle condition by PMSM in speed-control mode. To study the speed fluctuation control of ICRE, the PMSM control mode was then switched from the speed-control mode to the torque-control mode after the steady idle condition. The steady states of a low-power and a high-power working condition were optimized by a new dual closed-loop control strategy to reduce the ICRE speed fluctuations. The switching process between the two steady states was further optimized by the dual closed-loop control strategy. The characteristics of ICRE speed fluctuation and charging process of batteries were also investigated. The results show that the speed fluctuation amplitude could be reduced by 30% at the low-power operating condition and 41.7% at the high-power operating condition with the optimal PI parameters of the dual closed-loop control strategy. During the switching process from low-power condition to high-power condition, the speed response time and overshoot rate can be reduced to 2.1s and 2.7% respectively.