The Effect of Tuning PMSM Torque to Track Engine Torque on Speed Fluctuation of Range Extender 2021-01-0784

REEV (Range-Extended Electric Vehicle) can avoid the mileage anxiety of BEV (Battery Electric Vehicle). Nevertheless, RE (Range Extender) for passenger cars prefers to use ICE (Internal Combustion Engine) with smaller displacement and lower cylinder number, which is usually with a worse vibration performance at low speeds. As RE only outputs electricity, it provides the possibility to optimize NVH (Noise, Vibration, and Harshness) of the engine by PMSM (Permanent Magnet Synchronous Motor). By real-time control, the electromagnetic torque of PMSM can track the shaft torque fluctuation during engine strokes, especially the combustion stroke. When the instability and rolling torque of RE could be suppressed, NVH performance of RE can be improved.

This paper presents simulation research on speed fluctuation suppression for RE engine based on dynamic torque compensation by controlling a PMSM. First, the simulation models of a three-cylinder ICE, a PMSM, and their control strategies were built and verified by GT-Power and Simulink. Second, a joint simulation was carried out to compare the effects of different PMSM torque patterns on the speed fluctuation of the RE. Then an FFT (Fast Fourier Transformation) analysis of the shaft speed was conducted to analyze the inhibitory effect in the frequency domain. Under 2000r/min and 0.7MPa BMEP (Brake Mean Effective Pressure) condition, the speed fluctuation value (the difference between the maximum and minimum speed in a cycle) of optimized torque patterns is decreased by 25.4% ~ 49.0%, and the speed variance is decreased by 54.2% ~ 79.2% when control frequency of the system is multiple frequency of engine speed fundamental frequency.