Method for detecting speed of permanent-magnetic synchronous motor

Abstract

The invention discloses a method for detecting the speed of a permanent-magnetic synchronous motor. The method includes dividing voltage of a triple-phase wire connected with the motor to acquire triple-phase stator voltage signals U1, V1 and W1 with certain voltage magnitude values by resistors at first, and constructing corresponding isolation voltage signals U2, V2 and W2; comparing the isolation voltage signals pairwise to acquire three circuit voltage signals VW, UV and UW; acquiring three voltage signals UA, UB and UC which have phase angles with mutual phase differences of 120 degrees and contain current running frequency information; realizing exclusive-or for optional two of the voltage signals UA, UB and UC and then realizing exclusive-or for the third voltage signal and a result of the previous exclusive-or to acquire a triple-frequency-multiplication voltage signal UT; and inputting the triple-frequency-multiplication voltage signal UT into a DSP (digital signal processor) acquisition channel, detecting interval counting values of pairwise pulse edges to obtain the time interval of each two pulse edges, and finally computing the rotation speed of the motor. By the aid of the method, problems that an existing method for detecting rotation speed on the basis of a back electromotive force method is low in instantaneity, is easy to generate erroneous detection values and cannot be used for precisely detecting the rotation speed when the rotation speed is low are solved.

Description

technical field [0001] The invention belongs to the technical field of motor speed detection, and in particular relates to a speed detection method of a permanent magnet synchronous motor. Background technique [0002] In the permanent magnet synchronous motor control system, it is generally necessary to install a mechanical sensor on the rotating shaft to measure the speed of the motor, but the introduction of the mechanical sensor will increase the size of the motor, increase the system cost and reduce the scope of application of the system. Therefore, the application of sensorless control technology in the permanent magnet synchronous motor control system is of great significance. [0003] At present, the sensorless control strategy mainly measures the stator voltage and current of the motor, and estimates the speed through a specific algorithm, mainly including direct calculation method, observer method, high-frequency signal injection method, back electromotive force me...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a permanent magnet synchronous motor speed detection method to solve the problems that the existing speed detection method based on the back electromotive force method has low real-time performance, easy to generate wrong detection values, and cannot accurately detect the speed at low speeds. Ensure the correct implementation of the speed sensorless vector control strategy

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