Permanent magnet synchronous motor demagnetization fault diagnosis method and device based on stator tooth magnetic flux

Abstract

The invention discloses a stator tooth magnetic flux-based permanent magnet synchronous motor demagnetization fault diagnosis method and device, and the method comprises the steps: firstly, building a stator tooth magnetic flux mathematical model based on a magnetic circuit Ohm law on the premise of assuming the steady-state operation of a motor and neglecting the influence of a fault on the saturation of an iron core; secondly, a detection coil composed of two sub detection coils which are reversely connected in series is adopted to measure stator tooth magnetic flux, and the stator tooth magnetic flux is converted into a voltage signal; finally, through finite element analysis software, under the rated operation condition of the motor, the usc of each detection coil in the health state and the demagnetization fault state is analyzed. When the detection coil is located in the range of the demagnetizing permanent magnet, the detection coil can generate two groups of voltages in opposite directions; when the detection coil is located in the range of the healthy permanent magnet, the usc is approximate to 0V; and when the demagnetization of the permanent magnet is more serious, the usc is larger. And moreover, the generation of the usc is related to time, so that the severity of the demagnetization fault and the position of the fault permanent magnet are judged.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motor fault diagnosis, and in particular to a permanent magnet synchronous motor demagnetization fault diagnosis method and device based on stator tooth magnetic flux. Background Art

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in new energy vehicles, industrial servo systems, and wind power generation due to their high power density and efficiency. However, in actual operation, these motors often face the interaction of complex electromagnetic environments and extreme operating conditions, resulting in a significantly increased failure rate. Demagnetization faults (DMFs), a typical permanent magnet failure mode, are particularly harmful. Local demagnetization not only causes air gap magnetic field distortion and increased torque pulsation, but can also trigger cascading failures through electromagnetic-mechanical coupling, ultimately resulting in significant economic losses and safety hazards.

[0003] Currently, a variety of diagnostic methods for permanent magnet synchronous motor (PMSM) demagnetization faults exist. Some methods measure physical quantities such as motor current, voltage, and torque for fault diagnosis. However, these methods are susceptible to variations in motor operating conditions and load, and diagnostic accuracy needs to be improved. Other methods use specialized sensors to measure the motor's magnetic field. While these sensors can obtain magnetic field information, they are complex to install and expensive. Therefore, developing an accurate, reliable, and cost-effective method for diagnosing demagnetization faults in PMSMs is of great practical significance. Summary of the Invention

[0004] The present invention aims to overcome the above-mentioned shortcomings of the prior art and provides a method and device for diagnosing demagnetization faults of a permanent magnet synchronous motor based on stator tooth magnetic flux.

[0005] The present invention aims to solve the problems of low accuracy, high cost, and complex installation in existing diagnostic methods, and to achieve efficient and accurate diagnosis of demagnetization faults in permanent magnet synchronous motors.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows: First, based on Ohm's law of magnetic circuit, assuming that the motor is in steady state operation and ignoring the effect of faults on core saturation, a mathematical model of the stator tooth flux STF is established: Where φ is the stator tooth flux, n is the number of stator teeth, t is time, ω is the electrical angular velocity, and F s 、 are the equivalent magnetomotive force amplitude and initial phase angle of the tooth flux generated by the stator current, F r 、 are the equivalent magnetomotive force amplitude and initial phase angle of the tooth flux generated by the permanent magnet, R s 、R g are the magnetic resistance of the stator core (including permanent magnets) and the air gap of the nth tooth equivalent magnetic circuit. When a demagnetization fault occurs, the equivalent magnetomotive force F generated by the permanent magnet r changes, which in turn causes the stator tooth flux to change.

[0007] Secondly, a detection coil consisting of two reverse-connected sub-detection coils is used to measure the stator tooth magnetic flux and convert it into a voltage signal. The distance between the two sub-detection coils is twice the pole pitch, and the induced voltage of the sub-detection coils is where u sbc and N sbc are the induced voltage and number of turns of the sub-detection coil, φ sbc is the magnetic flux in the sub-detection coil. Since the motor magnetic field is mainly concentrated in the air gap and the core, the magnetic flux in the sub-detection coil is approximately equal to the stator tooth flux, that is, φ sbc ≈φ st The induced voltage of the detection coil In subsequent studies, u sc represents the stator tooth flux. To more comprehensively detect demagnetization faults, multiple sets of detection coils are arranged at different phases and spatial positions of the motor. Finally, using finite element analysis software (such as Ansys Maxwell), under rated motor operating conditions (rated current and rated speed), the u of each detection coil in the healthy state and demagnetization fault state is analyzed. sc The results show that when the detection coil is within the range of the demagnetized permanent magnet, the detection coil will generate two sets of voltages with opposite directions; when the detection coil is within the range of the healthy permanent magnet, u sc Approximately 0V; when the permanent magnet demagnetization is more serious, u sc The larger the value, the larger the u sc The generation of is related to time, based on which the severity of the demagnetization fault and the location of the faulty permanent magnet can be determined.

[0008] The first aspect of the present invention is to provide a method for diagnosing demagnetization faults of a permanent magnet synchronous motor based on stator tooth magnetic flux, which specifically includes the following steps:

[0009] S1. Build a permanent magnet synchronous motor model in finite element analysis software, clarify its parameters, and arrange multiple sets of detection coils at different phases and spatial positions of the motor. Set the BH curve of the faulty permanent magnet to simulate demagnetization failure.

[0010] S2. When the motor is in a healthy state, the detection coil is used to collect the voltage signal after the stator tooth flux conversion through finite element software analysis. Then, demagnetization fault simulation is performed one by one for different permanent magnets, and the voltage signal after the stator tooth flux conversion is collected.

[0011] S3. Select the same permanent magnet to set different BH curves to simulate the severity of the fault, and collect the voltage signal after the stator tooth flux conversion.

[0012] S4. Based on the experimental results, analyze the change pattern of the detection coil voltage signal under different demagnetization fault degrees of the same permanent magnet and the detection coil voltage signal when demagnetization faults occur in different permanent magnets to verify the sensitivity and accuracy of demagnetization faults.

[0013] Among them, a permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth flux is characterized in that the multiple groups of detection coils are arranged in different phases and spatial positions of the motor as described in step S1, specifically including: for a 36-slot 12-pole permanent magnet synchronous motor, a total of 9 groups of detection coils are configured, each group contains 2 sub-detection coils, and a total of 18 sub-detection coils. These sub-detection coils are evenly distributed and installed in the manner of "every other stator tooth", that is, one sub-detection coil is installed every other tooth from the 36 stator teeth, and finally 18 stator tooth positions are covered. For specific installation positions, please refer to the attached. Figure 1 .

[0014] Among them, a permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth flux is characterized in that a BH curve of a faulty permanent magnet is set in step S3 to simulate the demagnetization degree of the permanent magnet and analyze the influence of different demagnetization degrees of the permanent magnet on the detection coil voltage signal.

[0015] Among them, a permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth magnetic flux is characterized in that the detection coil in step S2 collects the stator tooth magnetic flux, including: based on Ohm's law of the magnetic circuit, assuming that the motor is operating in a steady state and ignoring the impact of the fault on the core saturation, establishing a mathematical model of the stator tooth magnetic flux STF:

[0016]

[0017] Where, φ is the stator tooth flux, n is the number of stator teeth, t is time, ω is the electrical angular velocity, F s 、 are the equivalent magnetomotive force amplitude and initial phase angle of the tooth flux generated by the stator current, F r 、 are the equivalent magnetomotive force amplitude and initial phase angle of the tooth flux generated by the permanent magnet, R s 、R gare the magnetic resistance of the stator core (including permanent magnets) and the air gap of the nth tooth equivalent magnetic circuit. When a demagnetization fault occurs, the equivalent magnetomotive force F generated by the permanent magnet r changes, which in turn causes the stator tooth magnetic flux to change. Figure 2 .

[0018] The detection coil in step S2 collects the stator tooth magnetic flux and converts it into a voltage signal, which includes: using a detection coil composed of two reverse-connected sub-detection coils to measure the stator tooth magnetic flux and convert it into a voltage signal. The distance between the two sub-detection coils is twice the pole pitch, and the induced voltage of the sub-detection coils is:

[0019]

[0020] where u sbc and N sbc are the induced voltage and number of turns of the sub-detection coil, φ sbc is the magnetic flux in the sub-detection coil. Since the motor magnetic field is mainly concentrated in the air gap and the core, the magnetic flux in the sub-detection coil is approximately equal to the stator tooth flux, that is, φ sbc ≈φ st The induced voltage of the detection coil is:

[0021]

[0022] The second aspect of the present invention relates to a permanent magnet synchronous motor demagnetization fault diagnosis device based on stator tooth flux, comprising a memory and one or more processors, wherein the memory stores executable code, and when the one or more processors execute the executable code, they are used to implement the permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth flux of the present invention.

[0023] A third aspect of the present invention relates to a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the stator tooth flux-based permanent magnet synchronous motor demagnetization fault diagnosis method of the present invention.

[0024] This invention accurately diagnoses demagnetization faults in permanent magnet synchronous motors by analyzing, measuring, and converting stator tooth magnetic flux, as well as analyzing fault characteristics. During a fault condition, the stator tooth magnetic flux exhibits distinct variations. Monitoring and analyzing this variation effectively improves the accuracy of demagnetization fault diagnosis. Furthermore, the use of multiple detection coils allows for more comprehensive detection of motor demagnetization faults.

[0025] The advantages of the present invention are that it can comprehensively and accurately reflect the degree and location of the demagnetization fault of the motor, and provide a reference basis for the demagnetization fault diagnosis of the permanent magnet synchronous motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the original model of the permanent magnet synchronous motor and the installation position of the detection coil applied to the present invention.

[0027] Figure 2 It is the magnetic circuit diagram of permanent magnet synchronous motor. Specific implementation methods

[0028] The present invention is further described in detail below with reference to the accompanying drawings and through implementation cases. The implementation cases provided below for permanent magnet synchronous motors are explanations of the application of the present invention, and the present invention is not limited to the following cases.

[0029] Example 1

[0030] This embodiment relates to a permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth magnetic flux, which specifically includes the following steps:

[0031] S1. Build a permanent magnet synchronous motor model in finite element analysis software, clarify its main parameters, and arrange multiple sets of detection coils at different phases and spatial positions of the motor. Set the BH curve of the faulty permanent magnet to simulate demagnetization failure.

[0032] S2. When the motor is in a healthy state, the detection coil is used to collect the voltage signal after the stator tooth flux conversion through finite element software analysis. Then, demagnetization fault simulation is performed one by one for different permanent magnets, and the voltage signal after the stator tooth flux conversion is collected.

[0033] S3. Select the same permanent magnet to set different BH curves to simulate the severity of the fault, and collect the voltage signal after the stator tooth flux conversion.

[0034] S4. Based on the experimental results, analyze the change pattern of the detection coil voltage signal under different demagnetization fault degrees of the same permanent magnet and the detection coil voltage signal when demagnetization faults occur in different permanent magnets, verify the sensitivity and accuracy of the method of the present invention to demagnetization faults, and further optimize the diagnostic method.

[0035] An example of diagnosing a permanent magnet synchronous motor demagnetization fault is as follows:

[0036] (1) Refer to the attached Figure 1 , a permanent magnet synchronous motor model was built in the finite element analysis software. Its main parameters are as follows: stator outer diameter 290mm, inner diameter 180mm, axial length 88mm, rated speed 900rpm, rated current 4.3A, number of phases 3, number of coils 72, number of turns 36, number of parallel branches per phase 1, and slot-pole combination 36-12;

[0037] (2) Refer to the attached Figure 1, build detection coils on the stator teeth. Each set of detection coils is composed of two sub-detection coils connected in series in opposite directions. The distance between the two sub-detection coils is twice the pole pitch. (A total of 9 sets of detection coils, namely SC1, SC2, SC3, SC7, SC8, SC9, SC13, SC14, SC15)

[0038] (3) According to the calculation of the permanent magnet synchronous motor parameters, it takes about 66.67ms for the motor rotor to rotate one circle. We set the subsequent finite element simulation experiment time to 77.78ms to ensure that the voltage signal graph can show a complete cycle of the motor operation;

[0039] (4) The finite element experiment simulation of the healthy permanent magnet motor can be performed to obtain the voltage signal diagram of the detection coil. It can be seen that u sc It is -43mV---43mV, which can be approximated to 0V, which is consistent with the above theoretical analysis.

[0040] (5) Set the BH curves of permanent magnets N1-N6 and S1-S6, simulate 50% demagnetization, and perform finite element simulation to obtain the voltage signal of the detection coil. The results show that when a permanent magnet has a 50% demagnetization fault, as the motor runs, all detection coils will have voltage fluctuations with an amplitude of about 16.5V, and when a sub-detection coil is within the range of the demagnetized permanent magnet, its u sc The change is obvious, so we can see that u sc The generation of is related to time, based on which the position of the demagnetization fault permanent magnet can be determined;

[0041] (6) Set the BH curve of permanent magnet N1, simulate demagnetization of 10%, 30%, 50%, 70%, and 90% respectively, and perform finite element simulation to obtain the voltage signal of the detection coil. The results show that when a permanent magnet has a 10%, 30%, 50%, 70%, and 90% demagnetization failure, the detection coil will have a voltage fluctuation with an amplitude of approximately 3.25V, 10V, 16.5V, 23V, and 30V respectively. It can be seen that u sc The size of u is positively correlated with the degree of permanent magnet demagnetization. The more serious the permanent magnet demagnetization, the larger the sc The larger it is, the more serious the demagnetization failure of the permanent magnet can be judged.

[0042] (7) Combined with the results of the finite element simulation experiment, the change rules of the detection coil voltage signal under different demagnetization fault degrees and the detection coil voltage signal when demagnetization faults occur in different permanent magnets can verify the sensitivity and accuracy of the method of the present invention to demagnetization faults.

[0043] Example 2

[0044] This embodiment relates to a permanent magnet synchronous motor demagnetization fault diagnosis device based on stator tooth flux, including a memory and one or more processors. The memory stores executable code. When the one or more processors execute the executable code, they are used to implement the permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth flux of Example 1.

[0045] Example 3

[0046] This embodiment relates to a computer-readable storage medium, characterized in that a program is stored thereon, and when the program is executed by a processor, the permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth flux of embodiment 1 is implemented.

[0047] The above implementation methods are only exemplary descriptions of this patent and do not limit its scope of protection. Those skilled in the art may also make partial changes thereto. As long as they do not exceed the spirit of this patent, they are within the scope of protection of this patent.

Claims

1. A permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth flux, characterized in that: The stator tooth magnetic flux obtained based on Ohm's law of magnetic circuit is converted into voltage signal output by the detection coil to monitor the demagnetization degree of the permanent magnet and the location of the demagnetization fault; The specific steps include: S1. Build a permanent magnet synchronous motor model in finite element analysis software, clarify its parameters, and arrange multiple sets of detection coils at different phases and spatial positions of the motor. Set the BH curve of the faulty permanent magnet to simulate demagnetization failure. S2. When the motor is in a healthy state, the detection coil is analyzed using finite element software to obtain the voltage signal after the stator tooth magnetic flux conversion. Then, demagnetization fault simulation is performed on different permanent magnets one by one, and the voltage signal after the stator tooth magnetic flux conversion is collected; S3. Select the same permanent magnet and set different BH curves to simulate the severity of the fault, and collect the voltage signal after the stator tooth flux conversion; S4. Based on the experimental results, analyze the change pattern of the detection coil voltage signal under different demagnetization fault degrees of the same permanent magnet and the detection coil voltage signal when demagnetization faults occur in different permanent magnets to verify the sensitivity and accuracy of demagnetization faults.

2. A permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth flux according to claim 1, characterized in that: The arrangement of multiple groups of detection coils at different phases and spatial positions of the motor described in step S1 specifically includes: for a 36-slot, 12-pole permanent magnet synchronous motor, a total of 9 groups of detection coils are configured, each group contains 2 sub-detection coils, and a total of 18 sub-detection coils; these sub-detection coils are evenly distributed and installed in a "every other stator tooth" manner, that is, one sub-detection coil is installed for every other stator tooth among the 36 stator teeth, ultimately covering 18 stator tooth positions.

3. The method for diagnosing demagnetization fault of a permanent magnet synchronous motor based on stator tooth flux according to claim 1, characterized in that: In step S3, a BH curve of the faulty permanent magnet is set to simulate the demagnetization degree of the permanent magnet, and the influence of different demagnetization degrees of the permanent magnet on the voltage signal of the detection coil is analyzed.

4. The method for diagnosing demagnetization fault of a permanent magnet synchronous motor based on stator tooth flux according to claim 1, characterized in that: The detection coils in step S2 collect stator tooth magnetic flux, which includes: establishing a mathematical model of stator tooth magnetic flux STF based on Ohm's law of magnetic circuit, assuming that the motor is in steady state operation and ignoring the effect of faults on core saturation: Where, φ is the stator tooth flux, n is the number of stator teeth, t is time, ω is the electrical angular velocity, F s 、 are the equivalent magnetomotive force amplitude and initial phase angle of the tooth flux generated by the stator current, F r 、 are the equivalent magnetomotive force amplitude and initial phase angle of the tooth flux generated by the permanent magnet, R s 、R g are the magnetic resistance of the stator core (including permanent magnets) and the air gap of the nth tooth equivalent magnetic circuit; when a demagnetization fault occurs, the equivalent magnetomotive force F generated by the permanent magnet r changes, which in turn causes the stator tooth flux to change.

5. The method for diagnosing demagnetization fault of a permanent magnet synchronous motor based on stator tooth flux according to claim 1, characterized in that: The detection coil in step S2 collects the stator tooth magnetic flux and converts it into a voltage signal, which includes: using a detection coil composed of two sub-detection coils connected in series in opposite directions to measure the stator tooth magnetic flux and convert it into a voltage signal; the distance between the two sub-detection coils is twice the pole pitch, and the induced voltage of the sub-detection coils is: where u sbc and N sbc are the induced voltage and number of turns of the sub-detection coil, φ sbc is the magnetic flux in the sub-detection coil; since the motor magnetic field is mainly concentrated in the air gap and the core, the magnetic flux in the sub-detection coil is approximately equal to the stator tooth flux, that is, φ sbc ≈φ st ; The induced voltage of the detection coil:

6. A permanent magnet synchronous motor demagnetization fault diagnosis device based on stator tooth flux, characterized in that: It includes a memory and one or more processors, wherein the memory stores executable code, and when the one or more processors execute the executable code, they are used to implement the permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth flux as described in any one of claims 1 to 5.

7. A computer-readable storage medium, characterized in that A program is stored thereon, and when the program is executed by a processor, the permanent magnet synchronous motor demagnetization fault diagnosis method based on stator tooth flux according to any one of claims 1 to 5 is implemented.

Images