CN104506103B - A kind of initial position detection method for permanent magnet synchronous electric motor rotor - Google Patents

Abstract

The invention provides a method for detecting the initial position of the rotor of a permanent magnet synchronous motor. According to the law that the amplitude of the high-frequency current response of the three-phase winding varies with the position angle of the rotor, the method injects the three-phase winding of the stator of the permanent magnet synchronous motor Symmetrical high-frequency voltage signal, high-frequency current response signal is detected, using the three-phase high-frequency current response amplitude relationship, the rotor position is locked within the range of 30°, and then the stator three-phase winding current is directly responded to by a linear approximation method The amplitude of the signal is mathematically analyzed and calculated to obtain the position information of the d-axis of the rotor, and then pulse injection is performed at both ends of the detected d-axis to detect the magnitude of the response current, and the N and S poles are distinguished according to the principle of d-axis magnetic circuit saturation. This method not only The invention can accurately, reliably and quickly detect the initial position information of the rotor of the permanent magnet synchronous motor, and has a simple algorithm and a small amount of computation.

Description

A method for detecting the initial position of the permanent magnet synchronous motor rotor

technical field

The invention relates to a method for detecting the initial position of a rotor of a permanent magnet synchronous motor, in particular to the control field of the permanent magnet synchronous motor which has an incremental photoelectric encoder and requires the stability of motor starting.

Background technique

At present, there are many domestic researches on the initial position detection methods of permanent magnet synchronous motors, but all of them have their shortcomings. The position detection method based on the back EMF of the motor is simple in calculation and reliable in operation, but its disadvantage is that the back EMF of the motor is very small or zero at low speed or zero speed, which is not conducive to position detection or can not detect the initial position of the motor at all. The ordinary high-frequency signal injection method solves the position detection problem of the back-emf method at low speed or zero speed. The high-frequency response signal contains the position information of the rotor, but the demodulation algorithm for the high-frequency response signal is very complicated, and the amount of calculation Large and theoretical, but there are often many problems in practical application. The pulse signal injection method is simple to detect the initial position of the rotor, but the detection time is long, and the rotor is easily affected by the injected pulse signal to rotate during the detection process.

Contents of the invention

The technical problem to be solved in the present invention is: in order to solve the problem of detecting the initial position of the permanent magnet synchronous motor and meet the requirements of the starting stability of the permanent magnet synchronous motor, this solution provides a method for detecting the initial position of the permanent magnet synchronous motor rotor. This method can not only accurately, reliably and quickly detect the initial position information of the permanent magnet synchronous motor rotor, but also has a simple algorithm and a small amount of calculation.

The technical solution adopted by the present invention to solve the technical problem is as follows: first step, inject high-frequency voltage signals corresponding to the phase sequence symmetry into the three-phase (take three-phase as an example) windings of the stator A, B, and C of the permanent magnet synchronous motor. The second step is to detect the current response signals of the three-phase windings, and record the response current amplitudes of the A, B, and C three-phase windings respectively. In the third step, the d-axis position of the rotor can be calculated according to the rule that the magnitude of the three-phase response current varies with the rotor position. The fourth step is to inject pulses into the two poles of the d-axis according to the principle of d-axis saturation. According to the difference in the magnitude of the pulse response current, the N and S poles can be distinguished, and the initial position information of the motor rotor can be calculated.

The beneficial effect of the present invention is: the initial position of the rotor of the permanent magnet synchronous motor is detected by using the high-frequency signal injection method. The signal is analyzed mathematically, and the d-axis position information of the rotor is obtained through simple mathematical calculation and linear approximation, and the N and S poles are distinguished by the d-axis saturation principle. The processing of the high-frequency response current signal by this method saves the process of coordinate transformation and complex signal processing, shortens the detection time, and has a small error in calculating the initial position of the rotor.

Description of drawings

Figure 1. When the motor rotor is at a certain position (21° electrical angle), the high-frequency current response when the high-frequency voltage signal is passed into the three-phase winding of the stator.

Fig. 2 The law that the magnitude of the high-frequency current response of the stator A, B, and C three-phase windings varies with the rotor position angle (electrical angle).

Fig. 3 is the calculation error estimate brought by the approximate linearization calculation method used in the calculation of the rotor position angle.

Detailed ways

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

Three-phase symmetrical high-frequency voltage signals are injected into the three-phase windings of the permanent magnet synchronous motor stator, and corresponding current response signals will be generated in the three-phase windings, as shown in Figure 1. It can be seen that the current response amplitudes generated in the three-phase windings A, B, and C of the motor stator are different at this time, corresponding to the current rotor position, Ia>Ic>Ib. According to the theoretical analysis, it can be known that the inductance value of the three-phase winding of the motor will change with the position of the rotor, and the difference in the inductance value will lead to the difference in the amplitude of the high-frequency current response. Through experiments and simulations, it can be concluded that with different rotor position angles (electrical angles), the changing law of the current response amplitudes of the stator A, B, and C three-phase windings is shown in Figure 2. It can be seen that within the range of 360° (electrical angle), the current response amplitude of the stator three-phase winding changes with the rotor position angle in a regular way: (1) Ia>Ic>Ib within the range of 0°-30°; (2 ) Ic>Ia>Ib in the range of 30°-60°; (3) Ic>Ib>Ia in the range of 60°-90°; (4) Ib>Ic>Ia in the range of 90°-120°; ( 5) Ib>Ia>Ic in the range of 120°-150°; (6) Ia>Ib>Ic in the range of 150°-180°; (7) same as 0°-180° at 180°-360° .

In this way, the rotor position angle can be determined within two ranges of 30° before or after 180° (electrical angle) according to the magnitude of the three-phase current responses of Ia, Ib, and Ic. Among them, the difference between before and after 180° is that the judged angle corresponds to the N pole or the S pole. Assuming that the N pole and the S pole are not distinguished first, it is considered that the rotor N pole is within a certain 30° before 180°. Calculate the rotor position angle according to the following formula (mathematical linear approximation method) (1) θ=(Ic-Ib)/(Ia-Ib)*30° at 0°-30°; (2) at 30°-60° θ=(Ic-Ia)/(Ic-Ib)*30°+30° at °; (3) θ=(Ib-Ia)/(Ic-Ia)*30°+60 at 60°-90° °; (4) θ=(Ib-Ic)/(Ib-Ia)*30°+90° at 90°-120°; (5) θ=(Ia-Ic)/ at 120°-150° (Ib-Ic)*30°+120°; (6) θ=(Ia-Ib)/(Ia-Ic)*30°+150° at 150°-180°. Using the above formula for calculation, the error (regarding the change of the three-phase current amplitude with the rotor position in Figure 2 as a sinusoidal change law) is approximately Δθ=θ-(Ic-Ib)/(Ia-Ib)*30° (Taking the case of 0°-30° as an example, other situations are similar, and the calculation error is the same), as shown in Figure 3. It can be calculated that the error does not exceed 0.56° (electrical angle), which shows that this mathematical linear approximation method itself will not bring large calculation errors. The error brought by the calculation has negligible influence on the starting control of the permanent magnet synchronous motor.

The method is described by taking Fig. 1 as an example. As shown in Figure 1, at this time Ia=4.583A; Ib=2.719A; Ic=3.939A, Ia>Ic>Ib, when the N and S poles are not distinguished, the motor rotor is in the range of 0°-30°, through θ =(Ic-Ib)/(Ia-Ib)*30° can calculate θ≈19.64°, and the actual rotation angle of the motor is 21° at this time, and the total error is 1.36° (including the linear approximation calculation error and the position detection method own error).

Finally, the N and S poles of the rotor are distinguished, and the d-axis magnetic circuit saturation method is used. Pulse injection is performed on the two directions of the detected d-axis respectively, and the magnitude of the response current value is detected. The end with a larger response current value is the N pole, and the end with a smaller response current value is the S pole. The principle is that when the current vector of the three-phase winding of the stator is in the direction of the d-axis and points to the N pole, the armature reaction acts as a magnetizer, and the saturation of the main magnetic circuit of the d-axis deepens, resulting in a decrease in the inductance of the d-axis, so the pulse response current value becomes larger; when the three-phase windings of the stator combine to form a current vector in the direction of the d-axis and point to the S pole, the armature reaction acts as a demagnetization effect, and the saturation degree of the main magnetic circuit of the d-axis decreases, resulting in an increase in the inductance of the d-axis, so the pulse response current value changes Small.

Claims (1)

1. A method for detecting the initial position of the rotor of a permanent magnet synchronous motor. By injecting three-phase symmetrical high-frequency sinusoidal voltage signals into the stator three-phase windings, the magnitude of the high-frequency current response of the stator three-phase windings varies with the rotor position angle First, determine the 30° range of the rotor position angle, and use Ia, Ib, and Ic to represent the high-frequency current response amplitudes of the A, B, and C three-phase windings respectively. The basis for determining the range is: (1 ) when Ia>Ic>Ib, in the range of 0°-30°, (2) when Ic>Ia>Ib, in the range of 30°-60°, (3) when Ic>Ib>Ia, in the In the range of 60°-90°, (4) when Ib>Ic>Ia, in the range of 90°-120°, (5) when Ib>Ia>Ic, in the range of 120°-150°, (6 ) When Ia>Ib>Ic, in the range of 150°-180°, (7) The situation at 180°-360° is the same as that at 0°-180°; according to the size of Ia, Ib, and Ic, the rotor can be The position angle is determined within two 30° ranges before or after the 180° electrical angle, where the difference between before and after 180° is that the judged angle corresponds to the N pole or the S pole; the precise rotor position angle θ within the 30° interval The specific judgment method is: (1) θ=(Ic-Ib)/(Ia-Ib)*30° at 0°-30°; (2) θ=(Ic-Ia)/ (Ic-Ib)*30°+30°; (3) θ=(Ib-Ia)/(Ic-Ia)*30°+60° at 60°-90°; (4) at 90°-120° θ=(Ib-Ic)/(Ib-Ia)*30°+90° at °; (5) θ=(Ia-Ic)/(Ib-Ic)*30°+120 at 120°-150° °; (6) θ=(Ia-Ib)/(Ia-Ic)*30°+150° at 150°-180°; finally, N and S polarities are distinguished according to the magnetic circuit saturation principle.