Sensorless Control of Starter and Generator Based on High-Frequency Signal Coupling Injection

Addressing the challenge of detecting the back-EMF signal at zero and low speeds in traditional sensorless brushless DC motors, this paper proposes a method based on high-frequency signal coupling injection. An external high-frequency sine wave generator is used to inject signals into the motor windings through a coupling capacitor, extracting rotor position information and commutation signals from the high-frequency line voltage response. The line voltage sampling strategy is optimized to eliminate false triggering of the line voltage comparator. To address the phase lag caused by the filter, the commutation timing is advanced and corrected, optimizing the position detection accuracy under low-speed and high-load conditions.