An I-F Speed Control Method for Seamless Forward-Reverse Operation of Permanent Magnet Synchronous Motors

Rotor position information is crucial for controlling permanent magnet synchronous motors. Although rotor position is typically obtained using sensors, these devices have drawbacks, such as high cost and bulky structures, prompting active research into sensorless control methods. However, sensorless control remains challenging at low speeds and stationary conditions due to inaccurate rotor position estimation. One commonly used approach for addressing this issue is I-F speed control. However, applying the I-F speed after q-axis alignment can lead to a step-out during reverse operations due to abrupt changes in the rotating direction. Aiming to overcome this limitation, this paper introduces an enhanced I-F speed control method that enables initial angle alignment and ensures stable operation without step-out, even during PMSM directional reversals. Overall, the proposed method provides stable transitions and robust bidirectional operation.