A Modeling Method for Permanent Magnet Synchronous Motor Based on d - Axis Magnetic Network Method

Abstract

The present invention discloses a modeling method for a permanent magnet synchronous motor based on the d-axis magnetic network method, which relates to the technical field of permanent magnet synchronous motor modeling. It solves the technical problems of the small applicable range of the prior art and the inability to accurately diagnose faults and quantitatively evaluate the degree of faults in permanent magnet synchronous motors. By calculating the magnetomotive force of the permanent magnet, the armature magnetomotive force, and each magnetic resistance on the d-axis magnetic circuit through the size parameters and material parameters of the motor body, the present invention provides an accurate analysis method for the demagnetization fault, eccentricity fault, inter-turn short circuit and open circuit fault of the permanent magnet synchronous motor, and can effectively analyze the fault type and the degree of the fault of the motor. The modeling method using the d-axis magnetic circuit effectively avoids the influence of the q-axis current. In the d-axis magnetic network, the torque ripple will not affect the rotation result, which not only reduces the analysis difficulty, but also improves the robustness of the system, and has a wider applicable range.

Description

Technical Field

[0001] The present invention belongs to the field of permanent magnet synchronous motor modeling, and relates to a permanent magnet synchronous motor modeling technology based on the d-axis magnetic network method, specifically a modeling method for a permanent magnet synchronous motor using the d-axis magnetic network method. Background Art

[0002] Due to its outstanding advantages, permanent magnet synchronous motors are widely used in fields such as wind power generation, aerospace, ships, and electric vehicles. During long-term operation, permanent magnet synchronous motors may experience various types of faults for various reasons, such as inter-turn short circuit faults, inter-turn open circuit faults, demagnetization faults, and eccentricity faults. Therefore, the diagnosis and analysis of various faults in permanent magnet synchronous motors are extremely urgent.

[0003] When analyzing the fault types of permanent magnet synchronous motors in the prior art, the fault types of permanent magnet synchronous motors are mainly diagnosed through methods such as signal processing, signal injection, and artificial intelligence; however, the prior art cannot simultaneously perform qualitative and quantitative analysis on motor faults, and has a small scope of application; therefore, there is an urgent need for a modeling method for permanent magnet synchronous motors with a wide scope of application. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art; to this end, the present invention proposes a modeling method for a permanent magnet synchronous motor using the d-axis magnetic network method, which is used to solve the technical problems of the small scope of application of the prior art and the inability to simultaneously perform qualitative and quantitative analysis on faulty motors. The modeling method for a permanent magnet synchronous motor based on the d-axis magnetic network method proposed by the present invention can effectively analyze the changes in the air-gap magnetic density waveform of the motor when various faults occur by modeling the magnetic circuit of the motor body, and can not only qualitatively analyze the fault types of the motor, but also quantitatively solve and analyze the degree of motor faults, and is applicable to permanent magnet synchronous motors with different pole numbers and different sizes.

[0005] To achieve the above object, according to an embodiment of the first aspect of the present invention, a modeling method for a permanent magnet synchronous motor using the d-axis magnetic network method is proposed, including:

[0006] Model the d-axis magnetic circuit in the magnetic circuit of a permanent magnet synchronous motor with any number of pole pairs, and calculate the magnetomotive force of the permanent magnet, the armature magnetomotive force, and each magnetic resistance on the d-axis magnetic circuit through the motor design parameters;

[0007] Establish a d-axis magnetic network model of the permanent magnet synchronous motor according to the principle of establishing a circuit model; wherein, the principle of establishing a circuit model means that there is a power source and a closed loop is formed;

[0008] Simplify the d-axis magnetic network model through the magnetic circuit law; among them, the magnetic circuit principle means that the magnetomotive force of the permanent magnet and the armature magnetomotive force in the magnetic circuit are equivalent to the voltage in the closed loop, the magnetic resistance in the magnetic circuit is equivalent to the resistance in the closed loop, and the magnetic flux in the magnetic circuit is equivalent to the current in the closed loop.

[0009] Preferably, simplify and analyze the d-axis magnetic network model by combining the magnetic circuit law with motor faults; among them, motor faults include inter-turn short circuit, open circuit fault, demagnetization fault and eccentricity fault.

[0010] Preferably, for the inter-turn short circuit and open circuit faults of the permanent magnet synchronous motor, the direct-axis armature magnetomotive force F adi changes, and the equivalent magnetomotive force F 1i of the permanent magnet remains unchanged and equal; where i represents the i-th permanent magnet in the counterclockwise direction, i = 1, 2,..., n;

[0011] Simplify the d-axis magnetic network model through the expressions of the direct-axis armature magnetomotive force F adi , the equivalent magnetomotive force F 1i of the permanent magnet and the sum R 1i of the equivalent magnetic resistances on the i-th branch; among them, the expression of the direct-axis armature magnetomotive force F adi is The expression of the equivalent magnetomotive force F 1i of the permanent magnet is The expression of the sum R 1i of the equivalent magnetic resistances on the i-th branch is

[0012] Preferably, for the demagnetization fault of the permanent magnet synchronous motor, the direct-axis armature magnetomotive force F adi changes, and the equivalent magnetomotive force F 1i of the permanent magnet changes; and in the case of uniform demagnetization, the equivalent magnetomotive force F 1i of the permanent magnet is equal, and in the case of local demagnetization, the equivalent magnetomotive force F 1i of the permanent magnet is not equal;

[0013] The magnetomotive force of the demagnetized permanent magnet is F' pmi = tF pmi ; where t is the demagnetization coefficient, and 0 ≤ t ≤ 1;

[0014] The expression of the equivalent magnetomotive force F 1i of the permanent magnet is

[0015] Preferably, for the eccentricity fault of the permanent magnet synchronous motor, the air-gap magnetic resistance R ai changes, and the expression of the associated magnetic resistance R 2i is Among them, the associated magnetic resistance R2i It is a parameter generated by the combination of magnetic resistance.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. By calculating the magnetomotive force of the permanent magnet, the armature magnetomotive force and each magnetic resistance on the d-axis magnetic circuit through the size parameters and material parameters of the motor body, the present invention provides an accurate analysis method for the demagnetization fault, eccentricity fault, inter-turn short circuit and open circuit fault of the permanent magnet synchronous motor, and can effectively analyze the fault type and fault degree of the motor.

[0018] 2. The modeling method of the d-axis magnetic circuit adopted by the present invention effectively avoids the influence of the q-axis current. In the d-axis magnetic network, the torque ripple will not affect the rotation result, which not only reduces the analysis difficulty, but also improves the robustness of the system, and has a wider application range. Description of the Drawings

[0019] Figure 1 It is a modeling diagram of the permanent magnet synchronous motor based on the d-axis magnetic network method of the present invention;

[0020] Figure 2 It is a simplified model diagram for analyzing the inter-turn short circuit, open circuit fault and demagnetization fault of the permanent magnet synchronous motor in the present invention;

[0021] Figure 3 It is a simplified model diagram for analyzing the eccentricity fault of the permanent magnet synchronous motor in the present invention;

[0022] Figure 4 It is a modeling diagram of the d-axis magnetic network method for a 2-pole permanent magnet synchronous motor in the present invention;

[0023] Figure 5 It is a simplified model diagram for the demagnetization fault of a 2-pole permanent magnet synchronous motor in the present invention. Detailed Embodiments

[0024] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0025] Permanent magnet synchronous motors have the advantages of simple structure, small volume, light weight, low loss, high power density, high efficiency, and large torque-inertia ratio. At present, permanent magnet synchronous motors are widely used in wind power generation, aerospace, ships, and electric vehicles. During long-term operation, due to various reasons, permanent magnet synchronous motors are prone to different types of faults, such as inter-turn short circuit faults, inter-turn open circuit faults, demagnetization faults, and eccentricity faults. The diagnosis and analysis of various faults of permanent magnet synchronous motors are imminent, and the fault diagnosis and fault tolerance of motors are of great significance for the safe and reliable operation of motors.

[0026] At present, the analysis of motor fault types at home and abroad mainly diagnoses the fault types of motors through methods such as signal processing, signal injection, and artificial intelligence algorithms; signal processing mainly performs FFT transformation, Hilbert-Huang transformation, wavelet transformation, and empirical mode decomposition on current signals, voltage signals, and vibration signals to extract characteristic signals; signal injection mainly injects a rotating voltage signal into the control circuit to observe the change of inductance; the artificial intelligence algorithm method mainly identifies the motor fault type by establishing an algorithm model to train the data.

[0027] The modeling method of permanent magnet synchronous motors based on the d-axis magnetic network method proposed in this invention provides a new idea for diagnosing the fault types of motors. By modeling the magnetic circuit of the motor body, the change of the air-gap magnetic density of the motor when various faults occur can be effectively analyzed. It can not only qualitatively analyze the fault types of the motor, but also quantitatively analyze the degree of motor faults through quantitative solution; this modeling method is universal and applicable to motors with different pole pairs and different sizes; for the modeling of motors with different fault types, this modeling scheme is still applicable; the modeling method of permanent magnet synchronous motors based on the d-axis magnetic network method can effectively avoid the influence of the q-axis current, reduce the difficulty of magnetic circuit analysis, and make the modeling scheme simpler for some special control schemes.

[0028] Please refer to Figure 1 , this application provides a modeling method of a permanent magnet synchronous motor based on the d-axis magnetic network method, including:

[0029] Model the d-axis magnetic circuit in the magnetic circuit of a permanent magnet synchronous motor with any number of pole pairs, and calculate the magnetomotive force of the permanent magnet, the armature magnetomotive force, and each magnetic resistance on the d-axis magnetic circuit through the motor design parameters;

[0030] Establish the d-axis magnetic network model of the permanent magnet synchronous motor according to the establishment principle of the circuit model for the d-axis magnetic circuit;

[0031] Simplify the d-axis magnetic network model through the magnetic circuit law.

[0032] Figure 1 Among them, R sti is the magnetic resistance of the stator tooth; R siis the stator-side leakage reluctance; R ai is the air-gap reluctance; R pmi is the permanent-magnet reluctance; R ri is the rotor-side leakage reluctance; R sj is the stator yoke reluctance; R rj is the rotor yoke reluctance; F adi is the direct-axis armature magnetomotive force; F pmi is the permanent-magnet magnetomotive force; n is the number of poles of the permanent magnet of the permanent magnet synchronous motor, n = 2p, and p is the number of pole pairs of the permanent magnet synchronous motor.

[0033] For the analysis of different fault types, the simplification methods of the d-axis magnetic network model of the motor are different; for the inter-turn short-circuit and open-circuit faults of the permanent magnet synchronous motor, the magnitude of the armature magnetomotive force will be affected, and the armature magnetomotive force and the permanent-magnet magnetomotive force cannot be superimposed during the simplification process; for the demagnetization fault of the permanent magnet synchronous motor, the permanent-magnet magnetomotive force will be affected, and the d-axis armature magnetomotive force and the permanent-magnet magnetomotive force cannot be superimposed during the simplification process; for the eccentricity fault of the permanent magnet synchronous motor, the air-gap reluctance will be affected, and the air-gap reluctance and other reluctances cannot be superimposed during the simplification process.

[0034] In this application, the magnetic circuit law is combined with the motor fault to simplify the d-axis magnetic network model; among them, the motor faults include inter-turn short-circuit, open-circuit fault, demagnetization fault and eccentricity fault.

[0035] Please refer to Figure 2 , Figure 2 is the simplified model of the inter-turn short-circuit, open-circuit fault and demagnetization fault of the permanent magnet synchronous motor; for the inter-turn short-circuit and open-circuit faults of the permanent magnet synchronous motor, Figure 2 the direct-axis armature magnetomotive force F adi changes, and the equivalent magnetomotive force F 1i of the permanent magnet remains unchanged and equal;

[0036] The d-axis magnetic network model is simplified and analyzed through the expressions of the direct-axis armature magnetomotive force F adi , the equivalent magnetomotive force F 1i of the permanent magnet and the sum R 1i of the equivalent reluctances on the i-th branch;

[0037] The expression of the direct-axis armature magnetomotive force F adi is Formula 1: Among them, K dp is the winding factor, N is the number of winding turns, K ad is the conversion coefficient of the direct-axis armature magnetomotive force, and I d is the direct-axis current;

[0038] The expression of the equivalent magnetomotive force F 1i of the permanent magnet is Formula 2:

[0039] The sum of the equivalent magnetic reluctances on the i-th branch, R 1i has the expression as Formula 3:

[0040] Regarding the demagnetization fault of the permanent magnet synchronous motor, Figure 2 the armature magnetomotive force F on the direct axis adi varies, and the equivalent magnetomotive force F of the permanent magnet 1i varies; if it is uniform demagnetization, F 1i is equal, if it is partial demagnetization, F 1i is not equal; when the permanent magnet synchronous motor has a demagnetization fault, the magnetomotive force of the demagnetized permanent magnet drops, introducing a demagnetization coefficient t, and the expression of the magnetomotive force of the demagnetized permanent magnet is Formula 4: F′ pmi = tF pmi , then the expression of the equivalent magnetomotive force F of the demagnetized permanent magnet 1i is Formula 5:

[0041] Please refer to Figure 3 , Figure 3 which is a simplified model of the eccentricity fault of the permanent magnet synchronous motor; regarding the eccentricity fault of the permanent magnet synchronous motor, the width of the air gap of the permanent magnet synchronous motor changes with time, then the air gap magnetic reluctance R of the permanent magnet synchronous motor ai varies in magnitude, and when analyzing the eccentricity fault, its magnetic reluctance cannot be superimposed on other magnetic reluctances, Figure 3 the associated magnetic reluctance R in 2u has the expression as Formula 6:

[0042] Please refer to Figures 4 - 5 , taking the analysis of the demagnetization fault of a 2-pole permanent magnet synchronous motor under id = 0 control as an example:

[0043] For a 2-pole permanent magnet synchronous motor under id = 0 control,

[0044] According to Figure 5 , the system of equations 1 is listed based on the KVL circuit law:

[0045]

[0046] If the permanent magnet synchronous motor is in normal condition, the magnetomotive force of each permanent magnet is Formula 7: F 10 = F 20 = F 30 = F 40 = F 1 ;

[0047] If a single permanent magnet of the permanent magnet synchronous motor is demagnetized, the magnetomotive force of each permanent magnet is Formula 8:

[0048]

[0049] Substitute Equation 7 into Equation Set 1, the main air-gap flux of a normal motor is:

[0050] Substitute Equation 8 into Equation Set 1, the main air-gap flux of a demagnetized permanent magnet is:

[0051]

[0052] The main flux corresponding to the demagnetized permanent magnet is Analyze and calculate the demagnetization degree t by assigning values to the midpoints of the main flux waveforms of the permanent magnets adjacent to the demagnetized permanent magnet (through this modeling method, the demagnetization degree of the demagnetized permanent magnet under demagnetization conditions can be accurately calculated), and obtain The main flux in the formula and can be obtained by multiplying the air-gap magnetic density measured by a linear Hall sensor by the area of a single stator tooth.

[0053] Some of the data in the above formula are calculated by taking their numerical values after removing the dimension. The formula is the one closest to the actual situation obtained through software simulation of a large amount of collected data; the preset parameters and preset thresholds in the formula are set by those skilled in the art according to the actual situation or obtained through simulation of a large amount of data.

[0054] The working principle of the present invention:

[0055] Model the d-axis magnetic circuit in the magnetic circuit of a permanent magnet synchronous motor with any number of pole pairs, and calculate the magnetomotive force of the permanent magnet, armature magnetomotive force, and each magnetic resistance on the d-axis magnetic circuit through the motor design parameters.

[0056] Establish the d-axis magnetic network model of the permanent magnet synchronous motor according to the establishment principle of the circuit model for the d-axis magnetic circuit; simplify the d-axis magnetic network model by combining the magnetic circuit law with motor faults.

[0057] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical method of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A modeling method for a permanent magnet synchronous motor using the d-axis magnetic network method, characterized in that, it includes: Model the d-axis magnetic circuit in the magnetic circuit of a permanent magnet synchronous motor with any number of pole pairs, and calculate the magnetomotive force of the permanent magnet, the armature magnetomotive force, and each magnetic resistance on the d-axis magnetic circuit through the motor design parameters; among them, each magnetic resistance includes: stator yoke magnetic resistance, stator tooth magnetic resistance, stator side leakage magnetic resistance, air gap magnetic resistance, permanent magnet magnetic resistance, rotor side leakage magnetic resistance, and rotor yoke magnetic resistance; Establish the d-axis magnetic network model of the permanent magnet synchronous motor according to the establishment principle of the circuit model for the d-axis magnetic circuit; Simplify the d-axis magnetic network model through the magnetic circuit law in combination with motor faults; among them, motor faults include inter-turn short circuit, open circuit fault, demagnetization fault, and eccentricity fault; For the inter-turn short circuit and open circuit faults of a permanent magnet synchronous motor, the direct-axis armature magnetomotive force changes, and the equivalent magnetomotive force of the permanent magnet remains unchanged and equal; where represents the th permanent magnet in the counterclockwise direction = 1, 2, …, n, where n is the number of poles of the permanent magnets of the permanent magnet synchronous motor, and n = 2p, where p is the number of pole pairs of the permanent magnet synchronous motor; Through the direct-axis armature magnetomotive force , the equivalent magnetomotive force of the permanent magnet and the sum of the equivalent magnetic reluctances on the th branch are used to simplify the d-axis magnetic network model; among them, the expression of the direct-axis armature magnetomotive force is , the expression of the equivalent magnetomotive force of the permanent magnet is , and the expression of the sum of the equivalent magnetic reluctances on the th branch is ; among them, , K dp is the winding factor, N is the number of winding turns, K ad is the conversion coefficient of the direct-axis armature magnetomotive force, I d is the direct-axis current, is the magnetomotive force of the permanent magnet, is the leakage magnetic reluctance on the rotor side, is the magnetic reluctance of the permanent magnet, is the magnetic reluctance of the stator tooth, is the air-gap magnetic reluctance; For the demagnetization fault of a permanent magnet synchronous motor, the direct-axis armature magnetomotive force changes, and the equivalent magnetomotive force of the permanent magnet changes; and in the case of uniform demagnetization, the equivalent magnetomotive force of the permanent magnet is equal, while in the case of local demagnetization, the equivalent magnetomotive force of the permanent magnet is not equal; The magnetomotive force of the permanent magnet after demagnetization is ; where is the demagnetization coefficient, and 0 ≤ ≤ 1; Equivalent magnetomotive force of permanent magnet The expression is ; where is the magnetomotive force of the permanent magnet, is the leakage reluctance on the rotor side, is the reluctance of the permanent magnet; For the eccentricity fault of a permanent magnet synchronous motor, the air-gap reluctance changes, and the expression of the associated reluctance is ; where the associated reluctance is a parameter generated by the combination of reluctances, is the leakage reluctance on the rotor side, is the reluctance of the permanent magnet, is the reluctance of the stator teeth.

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