Method for identifying initial position of rotor of permanent magnet synchronous motor

Abstract

The invention relates to a method for identifying the initial position of a rotor of a permanent magnet synchronous motor. The method comprises the following steps of: applying a cosine voltage excitation signal A.cos (2. Pi. F.t) with the frequency of f and the amplitude of A on a d * axis of a hypothetical synchronous rotating coordinate system through a variable-frequency speed regulator; voltage excitation applied to a q * axis is kept to be 0; acquiring instantaneous three-phase currents ia, ib and ic output to the permanent magnet synchronous motor; the instantaneous three-phase currents ia, ib and ic are converted into a hypothetical synchronous rotating coordinate system through coordinate conversion, the extracted harmonic component with the frequency f in # imgabs0 # passes through a PI regulator, and the rotation angular velocity w of the hypothetical synchronous rotating coordinate system is output; a d * axis position angle theta * of the synchronous rotating coordinate system is obtained after the rotation angular velocity w is subjected to an integration link; the process is repeated until the d * axis position angle theta * of the synchronous rotating coordinate system tends to be stable, and the stable value is recorded as theta; the total execution time of the first n maximum value # imgabs2 # and minimum value # imgabs3 # of the d * axis current # imgabs1 # is an integral multiple of the excitation signal period # imgabs4 #, and summation judgment is carried out after the process is executed.

Description

Technical Field

[0001] The present invention relates to a permanent magnet synchronous motor control system, and more specifically, to a permanent magnet synchronous motor rotor initial position identification method. Background Art

[0002] (1) Permanent magnet synchronous motors have been widely used in electric vehicles, air conditioners, water pumps, blowers and other industrial fields due to their advantages such as high power density and low vibration. In order to give full play to its high performance advantages, closed-loop variable frequency speed control is generally adopted. There are two types of permanent magnet synchronous motor control: with speed sensor and without speed sensor.

[0003] (2) In some special occasions, such as special working fluid environment, low-cost application and other conditions, speed sensorless becomes an inevitable choice.

[0004] (3) One difficulty of the speed sensorless control technology is to identify the initial position of the permanent magnet synchronous motor rotor. In the existing technology, the "vector pulse injection method" requires multiple injections of pulse voltage, has high requirements for the current detection link, and has limited recognition accuracy; the "high-frequency signal injection method" can only determine the position of the rotor axis, and the magnetic pole polarity judgment still requires the addition of a pulse injection link. Summary of the invention

[0005] The problem to be solved by the present invention is that, in view of the above situation, in order to improve the recognition accuracy and implementation convenience, a novel method for identifying the initial position of the rotor of a permanent magnet synchronous motor is proposed. The method is easy to be integrated into the variable frequency speed regulator of the permanent magnet synchronous motor without adding additional hardware and basic software configuration overhead.

[0006] To solve the above problems, the technical solution adopted by the present invention is: a method for identifying the initial position of a permanent magnet synchronous motor rotor, comprising the following steps:

[0007] (1) The frequency converter is used to adjust the speed of the imaginary synchronous rotating coordinate system. * The axis applies a cosine voltage excitation signal A·cos(2·π·f·t) with a frequency of f and an amplitude of A; q * The voltage excitation applied to the axis is kept at 0;

[0008] (2) Collect the instantaneous three-phase current i output to the permanent magnet synchronous motor a 、i b 、i c ; Through coordinate transformation, the instantaneous three-phase current i a 、i b 、i c Transform to the imaginary synchronous rotating coordinate system, where d * The shaft current is recorded as q * The shaft current is recorded as q* Shaft current Multiply it by the sine value B·sin(2·π·f·t) with frequency f and amplitude B, and extract it by low-pass filter H(f) The harmonic component with intermediate frequency f is denoted as Extracted The harmonic component with the intermediate frequency f is output by the PI regulator, and the output is the rotation angular velocity w of the imaginary synchronous rotating coordinate system; the rotation angular velocity w of the imaginary synchronous rotating coordinate system is obtained after the integral link. * Axis position angle θ * ; The initial value of the integral part is 0;

[0009] (3) Repeat the above process until the d of the synchronously rotating coordinate system is * Axis position angle θ * tends to be stable, and the stable value is recorded as θ;

[0010] (4) Start collecting and comparing to obtain d * Shaft current The first n largest values ​​of and minimum value The total execution time of the collection and comparison process should be the stimulus signal period After the process is completed, the sum

[0011]

[0012] If M>0, the actual d-axis position identification result of the rotor is θ; otherwise, the actual d-axis position identification result of the rotor is θ+π.

[0013] Furthermore, the value of A satisfies: The value of f satisfies:

[0014] Among them, V n is the rated voltage of the permanent magnet synchronous motor; f n is the rated frequency of the permanent magnet synchronous motor; f s is the switching frequency of the permanent magnet synchronous motor variable frequency speed regulator.

[0015] Furthermore, the cutoff frequency fc of H(f) is set to satisfy:

[0016] The beneficial effects of the present invention are:

[0017] The method for identifying the initial position of the permanent magnet synchronous motor rotor provided by the present invention is easy to be integrated into the existing variable frequency speed regulator or other permanent magnet synchronous motor drive control unit. It only needs to inject a sine (cosine) voltage excitation signal into the motor stator winding in a certain way, collect the current response signal and perform simple signal processing, without changing the hardware platform and software infrastructure of the original controller, to achieve a relatively accurate identification of the initial position of the permanent magnet synchronous motor rotor, and can be applied to both embedded permanent magnet synchronous motors and surface-mounted permanent magnet synchronous motors with certain saturation salient polarity. The technology of the above invention overcomes the problems of the prior art in that the controller has high requirements, implementation is inconvenient, and the identification accuracy is low, and has positive significance for improving the overall performance of the speed sensorless control algorithm of the existing variable frequency speed regulator or other permanent magnet synchronous motor drive control unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the principle of the permanent magnet synchronous motor rotor initial position identification method of the present invention. Specific implementation plan

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly presented, the following is a more detailed description through embodiments and drawings. It should be pointed out that the following embodiments are only provided to explain the present invention more clearly, but not to limit the present invention.

[0020] like Figure 1 As shown, a method for identifying the initial position of a permanent magnet synchronous motor rotor proposed in an embodiment of the present invention comprises the following steps:

[0021] (1) The frequency converter is used to adjust the speed of the imaginary synchronous rotating coordinate system. * The axis applies a cosine voltage excitation signal A·cos(2·π·f·t) with a frequency of f and an amplitude of A; q * The voltage excitation applied to the axis is kept at 0;

[0022] In general, the value of A satisfies: The value of f satisfies:

[0023] Among them, V n is the rated voltage of the permanent magnet synchronous motor; f n is the rated frequency of the permanent magnet synchronous motor; f s is the switching frequency of the permanent magnet synchronous motor variable frequency speed regulator;

[0024] The rotation angular velocity of the imaginary synchronous rotating coordinate system is recorded as w, with an initial value of 0; the position angle is recorded as θ * , the initial value is 0;

[0025] (2) Collect the instantaneous three-phase current i output to the permanent magnet synchronous motora 、i b 、i c ;

[0026] Through coordinate transformation, the instantaneous three-phase current i a 、i b 、i c Transform to the imaginary synchronous rotating coordinate system, where d * The shaft current is recorded as q * The shaft current is recorded as

[0027] The q * Shaft current Multiply it by the sine value B·sin(2·π·f·t) with frequency f and amplitude B, and extract it by low-pass filter H(f) The harmonic component with intermediate frequency f is denoted as

[0028] Where: The cutoff frequency fc setting value of H(f) satisfies:

[0029] The extracted The harmonic component with the intermediate frequency f is outputted by the PI regulator, which is the rotation angular velocity w of the imaginary synchronous rotating coordinate system; wherein the integral initial value of the PI regulator is 0;

[0030] The rotation angular velocity w of the imaginary synchronous rotating coordinate system is obtained after the integration link as d * Axis position angle θ * ; The initial value of the integral part is 0;

[0031] (3) Repeat the above process until the d of the synchronously rotating coordinate system is * Axis position angle θ * tends to be stable, and the stable value is recorded as θ;

[0032] At this point, we start collecting and comparing to obtain d * Shaft current The first n largest values ​​of and minimum value The value range of n is: N is the number of sampling points per cycle of the variable frequency speed regulator relative to the excitation signal (frequency f);

[0033] In particular, the total execution time of the collection and comparison process should be the excitation signal period An integer multiple of, for example, 2·T; after the process is completed, the sum

[0034]

[0035] If M>0, the actual d-axis position identification result of the rotor is θ; otherwise, the actual d-axis position identification result of the rotor is θ+π;

[0036] The above identification process ends.

[0037] The above is only a preferred specific implementation of the present invention, but the protection scope of the invention is not limited thereto. Any improvement without substantial change made by a person skilled in the art within the scope of the technical solution disclosed by the present invention without changing the principle shall also be regarded as the protection scope of the present invention.

Claims

1. A method for identifying the initial position of a permanent magnet synchronous motor rotor, characterized in that: The following steps are involved: (1) The frequency converter is used to adjust the speed of the imaginary synchronous rotating coordinate system. * The axis applies a cosine voltage excitation signal A·cos(2·π·f·t) with a frequency of f and an amplitude of A; q * The voltage excitation applied to the axis is kept at 0; (2) Collect the instantaneous three-phase current i output to the permanent magnet synchronous motor a 、i b 、i c ; Through coordinate transformation, the instantaneous three-phase current i a 、i b 、i c Transform to the imaginary synchronous rotating coordinate system, where d * The shaft current is recorded as q * The shaft current is recorded as q * Shaft current Multiply it by the sine value B·sin(2·π·f·t) with frequency f and amplitude B, and extract it by low-pass filter H(f) The harmonic component with intermediate frequency f is denoted as Extracted The harmonic component with the intermediate frequency f is output by the PI regulator, and the output is the rotation angular velocity w of the imaginary synchronous rotating coordinate system; the rotation angular velocity w of the imaginary synchronous rotating coordinate system is obtained after the integral link. * Axis position angle θ * ; The initial value of the integral part is 0; (3) Repeat the above process until the d of the synchronously rotating coordinate system is * Axis position angle θ * tends to be stable, and the stable value is recorded as θ; (4) Start collecting and comparing to obtain d * Shaft current The first n largest values ​​of and minimum value The total execution time of the collection and comparison process should be the stimulus signal period After the process is completed, the sum If M>0, the actual d-axis position identification result of the rotor is θ; otherwise, the actual d-axis position identification result of the rotor is θ+π.

2. The method for identifying the initial position of a permanent magnet synchronous motor rotor according to claim 1, characterized in that: The value of A satisfies: The value of f satisfies: Among them, V n is the rated voltage of the permanent magnet synchronous motor; f n is the rated frequency of the permanent magnet synchronous motor; f s is the switching frequency of the permanent magnet synchronous motor variable frequency speed regulator.

3. The method for identifying the initial position of a permanent magnet synchronous motor rotor according to claim 1, characterized in that: The cutoff frequency f of H(f) c Set the value to satisfy:

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