Speed Sensorless Vector Control Strategy for Permanent Magnet Synchronous Motor with Fan and Pump Load

Operating efficiency and high cost performance are challenging the application of the permanent magnet synchronous motors, and furthermore, characteristics of fan-pump load are becoming even more important. To achieve foresaid aims for permanent magnet synchronous motors providing energy to fan-pump load, this paper proposes a starting strategy of speed open-loop-current closed-loop control with current-frequency ratio in low speed section. Firstly, the rotor position is estimated by Lumberg observer in middle and high speed section, and the vector control method of speed-current double closed-loop is switched. Secondly, the starting process of current-frequency ratio speed open-loop and current closed-loop is studied, and the conditions of stable starting and acceleration are given. Thirdly, a state switching strategy of open-loop algorithm and closed-loop algorithm is proposed to ensure that the torque does not change abruptly during the switching process. Furthermore, a method of rotor stalling detection based on back EMF calibration is proposed, which detects the stalling state of rotor during buffeting. Moreover, the design rule of the PI parameter of the current loop in vector control is derived. Eventually, the experiment results verify the proposed method performance.