Novel Field-Weakening Control Scheme for Permanent-Magnet Synchronous Machines Based on Voltage Angle Control

This paper presents a novel voltage-angle-based field-weakening control scheme appropriate for the operation of permanent-magnet synchronous machines over a wide range of speed. At high rotational speed, the stator voltage is limited by the inverter dc bus voltage. To control the machine torque above the base speed, the proposed method controls the angle of the limited stator voltage by the integration of gain-scheduled q-axis current error. The stability of the drive is increased by a feedback loop, which compensates dynamic disturbances and smoothes the transition into field weakening. The proposed method can fully utilize the available dc bus voltage. Due to its simplicity, it is robust to the variation of machine parameters. Excellent performance of the proposed method is demonstrated through the experiments performed with and without speed and position sensors.