Low-frequency processing method of asynchronous motor speed sensorless vector control system

Abstract

The invention discloses a low-frequency processing method of an asynchronous motor speed sensorless vector control system. The method comprises the following steps: performing certain time delay according to a relation of size between motor real-time given speed corresponding angle frequency and switching frequency, and carrying out switching between a vector control mode and an I / f control mode, wherein the switching frequency comprises a switching frequency relatively large value and a switching frequency relatively small value; if the motor real-time given speed corresponding angle frequency is greater than the switching frequency relatively large value, switching the vector mode into the vector control mode; if the motor real-time given speed corresponding angle frequency is not greater than the switching frequency relatively small value, switching the control mode into the I / f control mode, wherein, in the I / f control mode, the motor real-time given speed corresponding angle frequency is used for replacing estimated speed corresponding angle frequency as system operation synchronous frequency, and meanwhile a current loop adopts closed-loop control. Through the adoption of the method, the operation out-of-control state, caused by speed estimation inaccuracy in a low-frequency stage, of the speed sensorless vector control system can be effectively avoided.

Description

technical field [0001] The invention relates to the field of vector control of asynchronous motors, in particular to a low-frequency processing method for a speed sensorless vector control system of an asynchronous motor. Background technique [0002] Asynchronous motors are widely used in the industrial field due to their simple structure and high reliability. The application of vector control technology has greatly improved the control performance of asynchronous motors. In a high-performance vector control system, a speed sensor is usually required to obtain an accurate rotational speed, and then obtain an accurate flux linkage angle for control. However, the installation of the speed sensor increases the cost of the system on the one hand, and reduces the reliability of the system on the other hand. Some operating occasions with relatively harsh environments are not suitable for installing speed sensors. The sensorless control technology of asynchronous motor has becom...

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Problems solved by technology

Although this effect can be reduced to a certain extent by dead zone compensation, it cannot be completely eliminated

In addition, the speed estimation system is based on the basic model of the motor. The parameters of the motor will have a certain offset with the change of temperature and magnetic field strength during operation, which will also introduce errors into the estimation of the model.

In the low-frequency stage, the non-linearity of the switch tube and the offset of the motor parameters, especially the stator resistance, are particularly obvious, which will reduce the estimation accuracy of the observer, and even affect the stable operation of the system in severe cases.

[0004] For the stable operation problem in the low frequency stage, people have adopted various methods to establish and correct the observation model, such as the direct calculation method of the motor model, the model reference adaptive method (MRAS), the full-order flux linkage observer method, and the improvement of dead zone compensation. Accuracy, or stator resistance online compensation, etc., but at the low frequency stage, there is still the possibility of model detection error or insufficient compensation leading to unstable system operation

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