Turn-to-turn short-circuit fault diagnosis method for dual three-phase permanent magnet synchronous motor

Abstract

The invention discloses a method for diagnosing a short-circuit fault between turns of a dual three-phase permanent magnet synchronous motor, which belongs to the technical field of motor fault diagnosis and is specifically implemented according to the following steps: S1, establishing a mathematical model of a short-circuit fault between turns of a dual three-phase permanent magnet synchronous motor in a rotating coordinate system; S2, extracting fault features according to the mathematical model obtained in S1; S3, performing coordinate transformation on the fault features extracted in S2, and extracting a DC quantity representing the fault information from the fault features after coordinate transformation through a filter to obtain a fault feature value; S4, comparing the fault feature value obtained in S3 with a set threshold value to determine whether the motor has a fault. The invention sets a mathematical model of a short-circuit fault between turns of a dual three-phase permanent magnet synchronous motor in a rotating coordinate system, and after comparing it with a normal motor model, can analyze the fault features, thereby solving the technical problem that a short-circuit fault between turns of a dual three-phase permanent magnet synchronous motor cannot be accurately detected.

Description

Technical Field

[0001] The invention belongs to the technical field of motor fault diagnosis, and in particular relates to a method for diagnosing inter-turn short-circuit faults of dual three-phase permanent magnet synchronous motors. Background Art

[0002] Due to its small output torque pulsation, high reliability and simple control, dual three-phase permanent magnet synchronous motors are gradually being used in new energy vehicles, rail transit, ships and other fields. During the working process, dual three-phase permanent magnet synchronous motors are prone to various faults due to the small working environment, high temperature, high humidity, poor heat dissipation conditions, and mechanical and electrical factors. Among them, turn-to-turn short circuit fault is the most common fault, which is highly destructive and easily causes other faults. If the fault is not discovered in time and corresponding measures are not taken during the fault, it will eventually lead to more serious consequences. In order to improve the safety and reliability of permanent magnet synchronous motors, the diagnosis of turn-to-turn short circuit faults of permanent magnet synchronous motors is very important. Summary of the invention

[0003] The purpose of the present invention is to provide a method for diagnosing a turn-to-turn short-circuit fault of a dual three-phase permanent magnet synchronous motor, which solves the technical problem that a turn-to-turn short-circuit fault of a dual three-phase permanent magnet synchronous motor cannot be accurately detected.

[0004] The technical solution adopted by the present invention is a method for diagnosing a short-circuit fault between turns of a dual three-phase permanent magnet synchronous motor, which is specifically implemented according to the following steps:

[0005] S1, establish a mathematical model of inter-turn short circuit fault of dual three-phase permanent magnet synchronous motor in rotating coordinate system;

[0006] S2, extracting fault features based on the mathematical model obtained in S1;

[0007] S3, coordinate transformation is performed on the fault features extracted by S2, and a DC quantity representing the fault information is extracted from the fault features after coordinate transformation through a filter to obtain a fault feature value;

[0008] S4, comparing the fault characteristic value obtained in S3 with the set threshold value to determine whether the motor fails.

[0009] The present invention is also characterized in that:

[0010] Step 1 is as follows:

[0011] The short-circuit turns ratio μ of the dual three-phase permanent magnet synchronous motor is defined as:

[0012]

[0013] In formula (1), N fis the number of short-circuit turns of a certain phase stator winding, and N is the total number of turns of a certain phase stator winding;

[0014] The motor mathematical model is established based on the fault voltage equation of the dual three-phase permanent magnet synchronous motor:

[0015]

[0016] ψ s =L s i s +γ s ψ fd (3)

[0017] In formula (2) and formula (3): u s is the phase voltage matrix of the stator winding; i s is the current matrix; Ψ S is the six-phase stator flux and short-circuit winding flux; ψ fd is the flux amplitude generated by the permanent magnet in each phase winding; γ s is the flux linkage coefficient matrix; u n is the neutral point voltage; R S is the resistor matrix; L S is the inductance matrix;

[0018] The transformation matrix of the fault voltage equation from the stationary coordinate system to the rotating coordinate system is:

[0019]

[0020] Both ends of formula (2) are multiplied by the transformation matrix T 62 ,get:

[0021]

[0022] In formula (5):

[0023] T 62 u s =[u d u q u z1 u z2 u o1 u o2 0] T , T 62 i s =[i d i q i z1 i z2 i o1 i o2 i f ] T ,

[0024] T 62 ψ s =[ψ d ψ q ψ z1 ψ z2 ψ o1 ψ o2 ψ f ] T ;

[0025] The voltage equation and flux equation under turn-to-turn short circuit fault are obtained:

[0026]

[0027]

[0028] Equation (6) is the voltage equation, and equation (7) is the flux equation.

[0029] Step 2 is as follows:

[0030] The fault equation of the faulty motor in the dq plane is:

[0031]

[0032] Fault harmonic term e in the state equation of the motor with inter-turn short circuit fault df and e qf As shown in formula (9):

[0033]

[0034] The magnitude of the fault current is:

[0035]

[0036] In formula (10), I f is the magnitude of the fault current;

[0037] Combining equation (9) and equation (10), we get:

[0038]

[0039] Formula (11) is the fault harmonic term e df and e qf The analytical expression of .

[0040] Step 3 is as follows:

[0041] The second harmonic component in the harmonic term of the inter-turn short-circuit fault rotates at an angular velocity of 2ω. In the fault extraction algorithm part, a new rotating coordinate system is set to rotate at an angular velocity of 2ω to convert the second harmonic into a DC quantity. The coordinate transformation matrix T is:

[0042]

[0043] When a turn-to-turn short circuit occurs in the motor, the voltage command value is transformed into:

[0044]

[0045] Among them, the fault characteristics are:

[0046]

[0047] Formula (14) is passed through a first-order low-pass filter to extract the DC quantity representing the fault information, and finally processed by formula (15) to obtain the required fault characteristic value:

[0048] Index=|e ddc | 2 +|e qdc | 2 (15)

[0049] In formula (15), Index is the required fault characteristic value.

[0050] Step 4 is specifically as follows: setting a threshold value Th to determine whether a fault occurs. When the Index exceeds Th, it is determined that a fault occurs; when the Index is less than Th, it is determined that the motor is normal.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The present invention discloses a method for diagnosing a short-circuit fault of a dual three-phase permanent magnet synchronous motor. By setting a mathematical model of a short-circuit fault of a dual three-phase permanent magnet synchronous motor in a rotating coordinate system, the fault feature can be analyzed after comparison with a normal motor model. Since the fault feature is an AC quantity and is difficult to extract and analyze, the fault feature is converted into a DC quantity that is easy to detect and analyze after coordinate transformation. The DC quantity is then compared with a set threshold value to determine whether the motor has failed. Based on the fault model, this analysis method utilizes the change in back electromotive force after a short-circuit fault occurs in a dual three-phase motor to diagnose the fault condition of the motor. No additional detection equipment is added, and no large amount of calculation is required. The hardware requirements are low, and the motor can be easily and quickly diagnosed to determine whether the motor has failed. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is an equivalent circuit diagram of the inter-turn short-circuit fault adopted in the inter-turn short-circuit fault diagnosis method of the dual three-phase permanent magnet synchronous motor of the present invention;

[0054] Figure 2 It is a fault feature extraction flow chart of the inter-turn short-circuit fault adopted in the inter-turn short-circuit fault diagnosis method of the dual three-phase permanent magnet synchronous motor of the present invention;

[0055] Figure 3 It is a structural diagram of a dual three-phase permanent magnet synchronous motor control system with a diagnostic module used in the dual three-phase permanent magnet synchronous motor turn-to-turn short-circuit fault diagnosis method of the present invention;

[0056] Figure 4 It is a voltage waveform when a turn-to-turn short circuit occurs in the dual three-phase permanent magnet synchronous motor in the dual three-phase permanent magnet synchronous motor turn-to-turn short circuit fault diagnosis method of the present invention;

[0057] Figure 5 It is a fault characteristic value waveform used to diagnose whether a fault occurs when a turn-to-turn short circuit occurs in a dual three-phase permanent magnet synchronous motor in the dual three-phase permanent magnet synchronous motor turn-to-turn short circuit fault diagnosis method of the present invention. DETAILED DESCRIPTION

[0058] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0059] The present invention provides a method for diagnosing a turn-to-turn short-circuit fault of a dual three-phase permanent magnet synchronous motor. First, a mathematical model of the turn-to-turn short-circuit fault of the dual three-phase permanent magnet synchronous motor in a stationary coordinate system is established, and the mathematical model is transformed into a mathematical model in a rotating coordinate system. After comparing the mathematical model with a normal motor model, the fault characteristics are analyzed. When a turn-to-turn short-circuit fault occurs, a second harmonic caused by the turn-to-turn short-circuit fault will appear in the dq axis voltage. The second harmonic contains the fault information of the motor. By establishing a new coordinate system rotating at an angular velocity of 2ω, the second harmonic component can be converted into a DC value, and then extracted by low-pass filtering. The DC value is compared with a set threshold value to determine whether the motor fails. The method is implemented in the following steps:

[0060] Step 1: Establish a mathematical model for the inter-turn short-circuit fault of a dual three-phase permanent magnet synchronous motor. Specifically, when an inter-turn short-circuit fault occurs in phase A of the motor, Figure 1 It can be seen that the motor A phase winding will add a short circuit loop. At this time, the resistance R f Phase A is divided into a healthy part and a faulty part, and the short-circuit turns ratio μ is defined as:

[0061]

[0062] In formula (1), N f is the number of short-circuit turns of a certain phase stator winding, and N is the total number of turns of a certain phase stator winding;

[0063] The motor mathematical model is established based on the fault motor voltage equation of the dual three-phase permanent magnet synchronous motor:

[0064]

[0065] ψ s =L s is +γ s ψ fd (3)

[0066] In formula (2) and Japanese formula (3):

[0067] U s =[u A u B u C u X u Y u Z 0] T ;

[0068] i s =[i A i B i C i X i Y i Z i f ] T ;

[0069] ψ s =[ψ A ψ B ψ C ψ X ψ Y ψ Z ψ f t ] T ;

[0070]

[0071] u n =[u n u n u n u n u n u n 0] T ;

[0072] Among them, U s =[u A u B u C u X u Y u Z 0] T Correct child construction compatible power square, u A , u B , u C , u X , u Y , u ZThey are A, B, C, X, Y, and Z phase voltages respectively; i s =[i A i B i C i X i Y i Z i f ] T is the current matrix, which includes six-phase stator current and short-circuit current; ψ s =[ψ A ψ B ψ C ψ X ψ Y ψ Z ψ f t ] T are the six-phase stator flux and the short-circuit winding flux respectively; ψ fd is the flux amplitude generated by the permanent magnet in each phase winding; γ s is the flux linkage coefficient matrix; u n is the neutral point voltage.

[0073] Example 1

[0074] In step 1 of the method for diagnosing interturn short circuit fault of a dual three-phase permanent magnet synchronous motor of the present invention:

[0075]

[0076] Formula (4) is the resistance matrix, where R is the stator resistance; R f The fault winding A f The resistance of

[0077]

[0078] Formula (5) is the inductance matrix, where L AA , L BB , L CC , L XX , L YY , L ZZ They are the self-inductance of the six-phase stator winding, M j-k is the mutual inductance between stator windings j and k (j∈{A,B,C,X,Y,Z},k∈{A,B,C,X,Y,Z}).

[0079] The transformation matrix of the fault voltage equation from the stationary coordinate system to the rotating coordinate system is:

[0080]

[0081] The inverse matrix of formula (6) is:

[0082]

[0083] Both ends of formula (2) are multiplied by the transformation matrix T 62 , we can get:

[0084]

[0085] In formula (8):

[0086] T 62 u s =[u d u q u z1 u z2 u o1 u o2 0] T ;

[0087] T 62 i s =[i d i q i z1 i z2 i o1 i o2 i f ] T ;

[0088] T 62 ψ s =[ψ d ψ q ψ z1 ψ z2 ψ o1 ψ o2 ψ f ] T ;

[0089] After calculation and simplification, the voltage and flux equations under turn-to-turn short-circuit fault are:

[0090]

[0091] Example 2

[0092] On the basis of Example 1, step 2 of the method for diagnosing inter-turn short circuit fault of a dual three-phase permanent magnet synchronous motor of the present invention is: the fault equation of the dq plane of the faulty motor is:

[0093]

[0094] Compared with normal motors, the state equation of the motor with inter-turn short circuit fault has an additional set of fault harmonic terms e df and e qf .

[0095]

[0096] To obtain the fault harmonic term e df and e qf The specific expression of i f For the convenience of analysis, we can directly use the following formula:

[0097]

[0098] In formula (13), I f is the magnitude of the fault current.

[0099] Substituting the fault current expression, equation (13), into equation (12), we can obtain the fault harmonic term e df and e qf Analytical formula:

[0100]

[0101] Example 3

[0102] On the basis of Example 2, step 3 of the method for diagnosing inter-turn short-circuit fault of a dual three-phase permanent magnet synchronous motor of the present invention is: the second harmonic component in the harmonic term of the inter-turn short-circuit fault rotates at an angular velocity of 2ω, so a new rotating coordinate system is set in the fault extraction algorithm part, which rotates at an angular velocity of 2ω, and the second harmonic can be converted into a DC quantity, and its coordinate transformation matrix T is:

[0103]

[0104] When the motor is normal, the voltage equation is transformed into:

[0105]

[0106] When a turn-to-turn short circuit occurs in the motor, the voltage command value is transformed into:

[0107]

[0108] Among them, the fault characteristics are:

[0109]

[0110] It can be seen that when a turn-to-turn short circuit occurs in the motor, the coordinate transformation u df and u qf The second harmonic component is converted into a DC value, and the voltage value after coordinate transformation when the motor is normal is eliminated. Then the obtained value is passed through a first-order low-pass filter to extract the DC value representing the fault information. Finally, the required fault characteristic value is obtained by processing formula (19)

[0111] Index=|e ddc | 2 +|e qdc | 2 (19)

[0112] Example 4

[0113] On the basis of Example 3, due to manufacturing process defects and other reasons, even if the motor is fault-free, the electrical signal of the motor still contains harmonics, which becomes an interference factor for fault diagnosis. In order to eliminate this interference, a threshold Th needs to be set to determine whether a fault occurs. When Index exceeds Th, it is determined that a fault occurs. When Index is less than Th, it is determined that the motor is normal and the motor is kept running.

[0114] In order to verify the correctness and effectiveness of the method of the present invention, a system simulation model is built in the Matlab2021b / Simulink environment. The model consists of speed setting, current loop PI controller, speed loop PI controller, coordinate transformation, voltage type inverter module, fault detection module, and dual three-phase permanent magnet synchronous motor. The fault detection module is implemented by Matlab-Function module programming, and the input is the motor dq axis voltage u d 、u q , the output is the fault characteristic value Index of the motor.

[0115] Depend on Figure 4 It can be seen that the dq-axis voltage waveform when the dual three-phase permanent magnet synchronous motor has a turn-to-turn short circuit fault shows that the short circuit of 5% of the turns of the A-phase winding is 0.6s, and the voltage fluctuates greatly, which includes the second harmonic caused by the fault, indicating that the dq-axis voltage is affected by the motor fault.

[0116] Depend on Figure 5 It can be seen that the fault characteristic value of the dual three-phase permanent magnet synchronous motor when a turn-to-turn short circuit occurs is 5% of the number of turns of the A-phase winding at 0.6s. Before the motor fails, the fault characteristic value is 0. After the failure, it can be seen that the fault characteristic value increases and the response is sensitive. The threshold can be set to 1. When the fault characteristic value is greater than the threshold, it can be determined that the motor has failed.

Claims

1. A method for diagnosing interturn short circuit faults of dual three-phase permanent magnet synchronous motors, characterized in that: Follow the steps below to implement it: S1, establish a mathematical model of inter-turn short circuit fault of dual three-phase permanent magnet synchronous motor in rotating coordinate system; S2, extracting fault features based on the mathematical model obtained in S1; S3, coordinate transformation is performed on the fault features extracted by S2, and a DC quantity representing the fault information is extracted from the fault features after coordinate transformation through a filter to obtain a fault feature value; The step 3 is specifically as follows: The second harmonic component in the harmonic term of the inter-turn short-circuit fault is A new rotating coordinate system is set in the fault extraction algorithm part to The angular velocity of the oscillator is rotated to convert the second harmonic into a DC quantity. The coordinate transformation matrix T is: （12） When a turn-to-turn short circuit occurs in the motor, the voltage command value is transformed into: （13） Among them, the fault characteristics are: （14） Formula (14) is passed through a first-order low-pass filter to extract the DC quantity representing the fault information, and finally processed by formula (15) to obtain the required fault characteristic value: （15） In formula (15), Index is the required fault characteristic value; S4, comparing the fault characteristic value obtained in S3 with the set threshold value to determine whether the motor has a fault; The step 4 is specifically as follows: setting a threshold Th Determine whether a fault has occurred. Index Exceed Th , it is determined that a fault has occurred; when Index Less than Th , then it is determined that the motor is normal.

2. The method for diagnosing turn-to-turn short-circuit faults of dual three-phase permanent magnet synchronous motors according to claim 1, characterized in that: The step 1 is specifically as follows: Definition of short-circuit turns ratio of dual three-phase permanent magnet synchronous motor for: （1） In formula (1), is the number of short-circuit turns of a certain phase stator winding, N is the total number of turns of the stator winding of a certain phase; The motor mathematical model is established based on the fault voltage equation of the dual three-phase permanent magnet synchronous motor: （2） （3） In formula (2) and formula (3): u s is the phase voltage matrix of the stator winding; i s is the current matrix; Ψ S It is the six-phase stator flux and short-circuit winding flux; is the flux amplitude generated by the permanent magnet in each phase winding; γ s is the flux linkage coefficient matrix; u n is the neutral point voltage; R S is the resistor matrix; L S is the inductance matrix; The transformation matrix of the fault voltage equation from the stationary coordinate system to the rotating coordinate system is: （4） Both ends of formula (2) are multiplied by the transformation matrix ,get: （5） In formula (5): ， ， ； The voltage equation and flux equation under turn-to-turn short circuit fault are obtained: （6） （7） Equation (6) is the voltage equation, and equation (7) is the flux equation.

3. The method for diagnosing turn-to-turn short-circuit fault of a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that: The step 2 is specifically as follows: The fault equation of the faulty motor in the dq plane is: （8） Fault harmonic terms in the state equation of a motor with turn-to-turn short-circuit fault and As shown in formula (9): （9） The magnitude of the fault current is: （10） In formula (10), is the magnitude of the fault current; Combining equation (9) and equation (10), we get: （11） Formula (11) is the fault harmonic term and The analytical expression of .

Images