Research on Low Speed Magnetic Field Tracking of Induction Motor Using Low Frequency Injection

In order to solve the problem that the rotor speed estimation of induction motor is inaccurate when the speed is very low, a method of low frequency signal injection is proposed. The method is based on the fundamental model of the induction motor. If there is a certain angular error between the actual direction of the rotor flux and the estimated direction, a low-frequency current signal is injected in the estimated direction, and a series of responses caused by the signal are used to construct the magnetic field deviation angle, and then adjusted by PI controller, the rotation speed of the air gap magnetic field is obtained, and then the motor speed is estimated. The simulation results prove the correctness and feasibility of the low-frequency signal injection estimation method in the low-speed operation of the asynchronous motor. It also verifies that the method has strong applicability under different conditions.