Low Speed Sensorless Control of BLDCM Based on High Frequency Signal Coupling Injection

Aiming at the problems of low detection accuracy, poor load capacity and large noise in the existing position sensorless control method when the brushless DC motor is running at low speed, this paper proposes a method of brushless DC motor low-speed sensorless control based on Buck-Boost converter and high-frequency signal coupling injection. This method uses an external high-frequency signal source to send out low-voltage and high-frequency detection signals, which are injected into the motor windings through the coupling circuit and the drive voltage output by the inverter at the same time, and the rotor position is determined by collecting the high-frequency voltage information fed back from the motor windings. The method proposed in this paper is simple and can improve the position detection accuracy and load capacity of the motor at low speed, and reduce the motor noise caused by the detection pulse. The simulation results verify the correctness of the theory and the feasibility of the method.