A method for improving HEV motor system efficiency considering battery voltage variation

Interior Permanent-magnet Synchronous Motors (IPMSMs) are suitable for Hybrid Electric Vehicle (HEV) due to their high efficiency and torque/power density. Since the torque of a PMSM is determined by the stator currents, stator current control is essential to the torque control. Also, the available torque of a PMSM is dependent on rotational speed and battery voltage (dc-link voltage of the inverter). In this paper, a new current reference generation method is proposed, which can improve the system efficiency with high control accuracy even when the battery voltage varies. The performance of the proposed method is verified by experimental results.