A control method and system for an AC motor without a position sensor

Abstract

The invention discloses a control method and system for an AC motor without a position sensor. After the AC motor is started, the initial position of the rotor is first calculated based on the magnetic field saliency algorithm, and then the magnetic field polarity is also considered. If the magnetic pole position is a magnetic field South pole, update the sum of the initial rotor position and π as the initial rotor position, so as to realize the subsequent control of the AC motor according to the initial rotor position, otherwise, directly use the initial rotor position calculated based on the magnetic field saliency algorithm to control the AC motor Take control. It can be seen that the application corrects the initial position of the rotor after determining that the magnetic pole position is the south pole of the magnetic field, and controls the AC motor according to the corrected initial position of the rotor, which improves the performance of the AC motor system at low speeds and ensures the low-speed control. The AC motor system is stable, and the sensorless control of the AC motor in the full speed range is realized.

Description

technical field [0001] The invention relates to the technical field of motor control, in particular to a control method and system for an AC motor without a position sensor. Background technique [0002] At present, the AC motor control technology generally requires a closed-loop rotor position or rotor speed signal. Therefore, in order to control the AC motor, it is necessary to first obtain the rotor position signal or the rotor speed signal of the AC motor. In the prior art, physical sensors are usually used to collect rotor position or speed signals, and corresponding AD circuits need to be planned in the motor control system to match them. In addition, in order to realize the mechanical connection between the AC motor and the physical sensor, it is necessary to add Connect the cable and the bearing length of the AC motor. On the one hand, the above arrangement makes the circuit structure of the control system of the AC motor more complex and costly; on the other hand, ...

AI Technical Summary

Problems solved by technology

But these algorithms can achieve the same effect as the motor control system with physical sensors above a certain speed, but the performance is worse below a certain speed

For this reason, a scheme to estimate the rotor position based on the magnetic field saliency algorithm at low speeds has been proposed in the prior art, but this scheme still often suffers from poor performance at certain speeds

The main reason is that when the rotor is at low speed or zero speed, these algorithms involve the initial position of the rotor when estimating the rotor position, and the initial position of the rotor is related to the polarity of the magnetic field. If the initial position of the rotor estimated by the algorithm is aligned with the south pole position of the magnetic field , then the sign of the torque output by the AC motor control system will change, thus making the AC motor system unstable

Images