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Sensorless Field Weakening Strategy With Overmodulation for High-Speed SPMSM Drives

The speed of surface-mounted permanent magnet synchronous motors (SPMSMs) is limited by the DC bus voltage. The fluctuation of voltage circle in field weakening area also has negative effects on motor control. To extend the operating speed, an alternative dual-mode overmodulation (OVM) algorithm with less computation is presented combined with a sensorless field weakening strategy based on the voltage estimation. The error between d-q axes current is introduced to improve the motor operation stability. A sensorless position observer is used to estimate the speed and position in medium and high speed. Simulation results of a high-speed SPMSM during the accelerating and decelerating process show that the fast speed response and high voltage utilization can be guaranteed.