Online turn-to-turn short circuit fault detection method for dual three-phase permanent magnet motor

Abstract

The invention discloses an online double three-phase permanent magnet motor turn-to-turn short circuit fault detection method, which comprises the following steps: describing motor behaviors in a fault state through a voltage equation and a current equation, when a turn-to-turn short circuit fault occurs, decomposing the voltage equation of a double three-phase permanent magnet motor into a healthy part and an extra voltage Ur, ur comprises a direct-current component and a second harmonic component related to a position angle theta, through Clark-Park transformation and matrix T2-0 demodulation, the second harmonic component in the Ur can be filtered out, only the direct-current component is reserved, so that a fault signal Fi is obtained, the fault signal Fi is related to an impedance parameter and fault severity of the motor, and the fault severity of the motor is improved. And the fault severity can be diagnosed through quantitative calculation. According to the method, efficient utilization of the dual three-phase permanent magnet motor can be met, the running state of the dual three-phase permanent magnet motor is monitored in real time, the fault position is found in time, and targeted remedial measures are taken for the position where the turn-to-turn short circuit fault occurs.

Description

Technical Field

[0001] The present invention relates to an online detection method for an inter-turn short circuit fault, and in particular to an online detection method for an inter-turn short circuit fault of an online dual three-phase permanent magnet motor. Background Art

[0002] During motor operation, short circuits, open circuits, and ground faults may occur. Among these faults, interturn short circuits are the most common and dangerous. While the initial symptoms of an interturn short circuit are subtle, they become more severe as the motor continues to operate, causing severe heating and even burnout, resulting in irreparable damage.

[0003] When a permanent magnet motor experiences an inter-turn short circuit fault, electrical signals such as voltage and current, as well as physical quantities such as magnetic field and vibration, will be affected, presenting a phenomenon that is completely different from that in a healthy state. Therefore, existing inter-turn short circuit fault diagnosis methods are all derived by summarizing and analyzing the differences between physical quantities such as voltage, current, and magnetic field in a faulty state and a healthy state.

[0004] This is mainly because when a motor has a short-circuit fault, the motor impedance characteristics will change, and the original balance state of the motor will be affected, causing the zero-sequence current, voltage, and voltage and current in the AC and DC axis coordinate systems to be distorted. Based on the above characteristics, a fault diagnosis method based on AC and DC axis current harmonics, high-frequency signal injection, and zero-sequence voltage monitoring is proposed.

[0005] Among the more common methods, fast Fourier transform, Hilbert-Huang transform, and wavelet analysis are used to extract the current characteristics caused by inter-turn short-circuit faults and detect them. However, when the motor uses current control methods such as field-oriented control, the current is affected by both the given signal and the motor's operating state. Therefore, the monitored fault current characteristics are subject to significant interference, making it difficult to accurately diagnose inter-turn short-circuit faults. In addition to using current characteristics to detect motor short-circuit faults, many researchers have also used electromagnetic signals such as back-electromotive force, voltage, and changes in stator winding impedance as characteristic signals to monitor inter-turn short-circuit faults.

[0006] However, the above fault monitoring methods usually require signal injection or the addition of additional sensors, which not only greatly increases the cost of the system, but also targets traditional three-phase motors and is not suitable for dual three-phase permanent magnet motors, and cannot achieve online fault detection and accurate quantitative detection. Summary of the Invention

[0007] To expand the application scope of dual three-phase permanent magnet motors, this paper proposes an accurate, real-time online method for detecting inter-turn short-circuit faults in dual three-phase permanent magnet motors. This method monitors the motor's operating status in real time and promptly warns of inter-turn short-circuit locations, ensuring safe operation of the equipment.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] An online dual-three-phase permanent magnet motor turn-to-turn short-circuit fault detection method is proposed. The motor behavior under fault conditions is described using voltage and current equations. When a turn-to-turn short-circuit fault occurs, the voltage equation of the dual-three-phase permanent magnet motor can be decomposed into a healthy portion and an additional voltage Ur. Ur contains a DC component and a second harmonic component related to the position angle θ. Through Clark-Park transformation and matrix T2-0 demodulation, the second harmonic component in Ur can be filtered out, retaining only the DC component, thereby obtaining a fault signal Fi. The fault signal Fi is related to the motor's impedance parameters and fault severity. Quantitative calculation can be used to diagnose the fault severity. The method specifically includes the following steps:

[0010] Step 1: Assume that the inter-turn short circuit fault occurs in phase a1, and the proportion of the fault part in phase a1 is k. At this time, the voltage equation of the dual three-phase permanent magnet motor is shown in formula (1):

[0011]

[0012] Where U a1 is the terminal voltage of phase a1, U0 is the neutral point voltage, U a1f is the fault voltage of phase a1, U a1h is the voltage of the healthy part of phase a1, i a1f is the current of the fault part of phase a1, i a1h is the current of the healthy part of phase a1, E a1 is the back electromotive force of phase a1, M5 is the mutual inductance matrix between the five healthy phases other than phase a1 and phase a1, I5 is the phase current matrix of the five healthy phases other than phase a1, R s is the phase resistance, L s is the phase self-inductance, ω is the electrical angular frequency, and j is the imaginary unit;

[0013] The a1 phase exists in the relationship shown in formula (2):

[0014]

[0015] Where i f is the short-circuit current, R f is the resistance of the short circuit path;

[0016] Combining formula (1) and formula (2), we can obtain the voltage formula (3) and current formula (4) of phase a1 when a turn-to-turn short circuit fault occurs:

[0017] U a1 -U0=i a1h (R s +L s ωj)+E a1 +M5I5ωj-k if (R s +L s ωj) (3);

[0018]

[0019] Where U a1-healthy is the voltage of the healthy part of phase a1;

[0020] Step 2: Considering the other five healthy motor phase windings, the voltage equation of the dual three-phase permanent magnet motor is shown in formula (5):

[0021]

[0022] Where M 6-6 is the mutual inductance matrix of the dual three-phase permanent magnet motor;

[0023] The voltage equation when a turn-to-turn short circuit fault occurs in a dual three-phase permanent magnet motor is very similar to the voltage equation when no turn-to-turn short circuit fault occurs, except that there is an additional voltage U r :

[0024]

[0025] The voltage equation (5) when a turn-to-turn short circuit fault occurs is divided into two parts: the healthy part without a turn-to-turn short circuit fault and the excess voltage U r ;

[0026] Step 3: When a dual three-phase balanced sinusoidal current is applied to the dual three-phase permanent magnet motor, the phase voltage is transformed to the d-axis and q-axis, wherein the healthy part is converted into a conventional DC component, U r Converted to formula (7):

[0027]

[0028] Where, T sr is the Clark-Park transformation matrix of dual three-phase permanent magnet motor;

[0029] i f It is defined as the form of sinusoidal quadrature current shown in formula (8):

[0030]

[0031] Where, for i f The phase angle, I f for i f The amplitude of θ is the electrical angle, and according to formula (4) we can get I f The expression (9):

[0032]

[0033] Combining formulas (7), (8) and (9), we can further analyze U r The transformation is shown in formula (10):

[0034]

[0035] Where Z1 is the impedance, is the impedance angle, M1 is the mutual inductance between adjacent phase sequences, and M2 is the mutual inductance between two phase sequences separated by one phase;

[0036] Step 4: Use the matrix T shown in formula (11) 2-0 Demodulate the signal shown in formula (10):

[0037]

[0038] T 2-0 The matrix converts the quadratic component into a DC signal and the DC signal into a negative quadratic component;

[0039] Step 5: Use a low-pass filter to filter the signal to the secondary component, retaining only the DC component. The signal shown in formula (10) is converted to the signal U shown in formula (12) DC-keep :

[0040]

[0041] Step 5: Find signal U DC-keep The square sum of , and then perform square root calculation to obtain the fault signal F shown in formula (13) i :

[0042]

[0043] Step 6: The severity of the inter-turn short-circuit fault is obtained according to formula (14):

[0044]

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] The method of the present invention can meet the requirements of efficient utilization of dual three-phase permanent magnet motors, monitor the operating status of dual three-phase permanent magnet motors in real time, promptly discover the fault location, and take targeted remedial measures for the location where the inter-turn short circuit fault occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is the structural diagram of the dual three-phase permanent magnet motor;

[0048] Figure 2 Phase arrangement and mutual inductance of a dual three-phase permanent magnet motor, (a) original phase arrangement of a dual three-phase permanent magnet motor, (b) schematic diagram of phase arrangement with negative phase and mutual inductor;

[0049] Figure 3 This is a schematic diagram of the dual three-phase permanent magnet motor circuit when a turn-to-turn short circuit fault occurs in phase a1;

[0050] Figure 4 This is the principle diagram of the inter-turn short circuit fault proposed by the present invention;

[0051] Figure 5 Finite element model and circuit, (a) finite element model, (b) finite element circuit, (c) schematic diagram of the winding of a dual three-phase permanent magnet motor with inter-turn short circuit fault;

[0052] Figure 6 Electromagnetic performance of different inter-turn short-circuit fault severity, (a) phase voltage in healthy state, k = 0.05, (b) phase voltage in healthy state, k = 0.2, (c) d-axis and q-axis voltage, (d) F i1 value;

[0053] Figure 7 This is a schematic diagram of the principle of the three-phase permanent magnet motor turn-to-turn short circuit fault diagnosis method proposed by the present invention. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0055] The structure of dual three-phase permanent magnet motor is as follows Figure 1 As shown, the phase distribution and mutual inductance of the dual three-phase permanent magnet motor are as follows Figure 2 As shown. Figure 2 In the phase arrangement diagram shown in (b), the mutual inductance between adjacent phase sequences (such as phases a1 and a2) is defined as M1, the mutual inductance between two phase sequences separated by one phase (such as phases a1 and c1) is defined as M2, and the mutual inductance between two phase sequences with a 90° electrical angle difference (such as phases a1 and b2) is 0.

[0056] Assume that the inter-turn short circuit fault occurs in phase a1, and the proportion of the fault part in phase a1 is k. At this time, the schematic diagram of the dual three-phase permanent magnet motor is as follows: Figure 3 As shown. Figure 3 The voltage equation that can be obtained is shown in equation (15).

[0057]

[0058] Where U a1 is the terminal voltage of phase a1, U0 is the neutral point voltage, U a1f is the fault voltage of phase a1, U a1h is the voltage of the healthy part of phase a1, i a1f is the current of the fault part of phase a1, i a1h is the current of the healthy part of phase a1, E a1 is the back electromotive force of phase a1, R s is the phase resistance, L s is the phase self-inductance, ω is the electrical angular frequency, and j is the imaginary unit (indicating that the voltage on the inductor leads the current by π / 2). M5 is the mutual inductance matrix between the five healthy phases other than phase a1 and phase a1, and I5 is the phase current matrix of the five healthy phases other than phase a1, as shown in formula (16):

[0059]

[0060] Where M a1-b1 is the mutual inductance between phase a1 and phase b1, M a1-c1 is the mutual inductance between phase a1 and phase c1, M a1-a2 is the mutual inductance between phase a1 and phase a2, M a1-b2 is the mutual inductance between phase a1 and phase b2, M a1-c2 is the mutual inductance between phase a1 and phase c2, i b1 、i c1 、i a2 、i b2 、i c2 They are the currents of phases b1, c1, a2, b2, and c2 respectively.

[0061] The a1 phase exists in the relationship shown in formula (17):

[0062]

[0063] Where i f is the short-circuit current, R f is the resistance of the short circuit, such as Figure 3 shown.

[0064] Combining formula (15) and formula (17), we can obtain the voltage formula (18) and current formula (19) of phase a1 when a turn-to-turn short circuit fault occurs.

[0065] U a1 -U0=i a1h (R s +L s ωj)+E a1 +M5I5ωj-k if (R s +L s ωj) (18)

[0066]

[0067] Where U a1-healthy is the voltage of the healthy part of phase a1.

[0068] Considering the other five healthy motor phase windings, the voltage equation of the dual three-phase permanent magnet motor is shown in formula (20):

[0069]

[0070] Where M 6-6 is the mutual inductance matrix of the dual three-phase permanent magnet motor, as shown in formula (21):

[0071]

[0072] It can be seen from formula (20) that the voltage equation when a turn-to-turn short circuit fault occurs in a dual three-phase permanent magnet motor is very similar to the voltage equation when no turn-to-turn short circuit fault occurs, with only an additional voltage U r :

[0073]

[0074] The voltage equation (20) when a turn-to-turn short circuit fault occurs can be divided into two parts: the healthy part where no turn-to-turn short circuit fault occurs and the excess voltage U r When a dual three-phase balanced sinusoidal current is applied to a dual three-phase permanent magnet motor, the phase voltage can be transformed to the d-axis and q-axis. Among them, the healthy part will be converted into a conventional DC component, U r Converted to formula (23):

[0075]

[0076] Where, T sr is the Clark-Park transformation matrix of the dual three-phase permanent magnet motor, which can be expressed as formula (24):

[0077]

[0078] i f It can be defined as the form of sinusoidal quadrature current shown in formula (25):

[0079]

[0080] Where, for i f The phase angle, I f for i f The amplitude of θ is the electrical angle, and according to formula (19) we can get I f The expression (26):

[0081]

[0082] Combining formulas (23), (25) and (26), we can further analyze U r The transformation is shown in formula (27):

[0083]

[0084] From (27) we can see that the transformed U r It consists of two parts: one is the DC component that is independent of the position angle θ, and the other is the second harmonic component that is related to the position angle θ. is the impedance angle, as shown in formula (28):

[0085]

[0086] Through the above analysis, it can be found that the inter-turn short circuit fault will cause the phase voltage to have an excess voltage U r , which leads to the appearance of second harmonic components of the d-axis and q-axis voltages.

[0087] Using the matrix T shown in formula (29) 2-0 Demodulate the signal shown in formula (27). 2-0 The matrix can convert the quadratic component into a DC signal and the DC signal into a negative quadratic component. Then, the signal can be filtered to the quadratic component by using a low-pass filter, leaving only the DC component. Therefore, the signal shown in formula (27) is converted to the signal U shown in formula (30) DC-keep .

[0088]

[0089] Find signal U DC-keep The square sum of , and then perform square root calculation to obtain the fault signal F shown in formula (31) i :

[0090]

[0091] From formula (31), we can see that the fault signal Fi With θ, It is not related to the impedance parameter and the fault severity k, so the fault signal is manifested as a DC component, which is easy to measure and observe. i Quantitative diagnosis of k is possible. i1 For example, the severity k of the inter-turn short-circuit fault can be obtained according to formula (32):

[0092]

[0093] According to the above description, the present invention proposes a schematic diagram of a method for diagnosing inter-turn short circuit faults of dual three-phase permanent magnet motors based on AC-DC voltage decoupling, as shown in FIG. Figure 4 As shown. Figure 4 It can be seen that the turn-to-turn short-circuit fault diagnosis method proposed in the present invention does not require harmonic injection and does not require the addition of hardware equipment such as sensors. It can conveniently and intuitively monitor the turn-to-turn short-circuit fault of the dual three-phase permanent magnet motor in real time, locate the three-phase winding where the fault occurs, and calculate the severity k of the fault.

[0094] The turn-to-turn short circuit fault detection method proposed in the present invention is not limited to the motor type, but is also applicable to other types of motors, such as three-phase motors (the turn-to-turn short circuit fault diagnosis method of three-phase permanent magnet motor based on AC-DC voltage decoupling is as follows Figure 7 As shown in the figure, multiphase motors such as five-phase motors and five-phase motors are also included. Any interturn short-circuit fault in a motor generates secondary components of the d-axis and q-axis voltages. By analyzing and processing these secondary components, interturn short-circuit faults can be diagnosed regardless of motor type.

[0095] Example:

[0096] A 22-pole, 24-slot dual three-phase permanent magnet motor is used as an example to verify the turn-to-turn short-circuit fault detection method proposed in this invention. The electromagnetic performance of the dual three-phase permanent magnet motor under the turn-to-turn short-circuit fault condition is simulated using the field-circuit coupling method based on finite element analysis. The motor finite element model is shown in Figure 1. Figure 5 When winding the motor, you should also follow Figure 5 (c) shown.

[0097] Assuming that the inter-turn short circuit fault occurs in phase a1, the winding wound on a stator tooth of phase a1 can be divided into two parts, such as Figure 5 As shown in the figure, a portion of the circuit can be considered as a faulty part. In this way, the k value (0.05 or 0.2) can be adjusted by adjusting the number of faulty turns (4 turns or 16 turns). Figure 5 (b) shows the circuit fault implementation in the finite element model. Figure 3 Set up and apply sinusoidal phase current excitation to calculate the electromagnetic performance of the dual three-phase permanent magnet motor. Figure 6 The phase voltage, d-axis and q-axis voltage and F under rated working condition are compared and analyzed for different fault degrees k. i1 .

[0098] Will Figure 6 The k calculated by finite element analysis shown in (d) is compared with the k calculated using formula (18). As can be seen from Table 1, the finite element analysis results are in good agreement with the analytical calculation results, indicating the correctness of the inter-turn short circuit fault diagnosis method proposed in this invention.

[0099] Table 1 Comparison of finite element calculation results and analytical calculation results

[0100] k <![CDATA[F i1 (Analytical calculation)]]> <![CDATA[F i1 (Finite Element Analysis)]]> Healthy state (k=0) 0 0 Turn-to-turn short circuit fault (k=0.05) 1.655 1.613 Turn-to-turn short circuit fault (k=0.2) 4.992 4.831

Claims

1. An online dual three-phase permanent magnet motor turn-to-turn short circuit fault detection method, characterized in that The method comprises the following steps: Step 1: Assume that the inter-turn short circuit fault occurs in phase a1, and the proportion of the fault part in phase a1 is k. At this time, the voltage equation of the dual three-phase permanent magnet motor is shown in formula (1): Where U a1 is the terminal voltage of phase a1, U0 is the neutral point voltage, U a1f is the fault voltage of phase a1, U a1h is the voltage of the healthy part of phase a1, i a1f is the current of the fault part of phase a1, i a1h is the current of the healthy part of phase a1, E a1 is the back electromotive force of phase a1, M5 is the mutual inductance matrix between the five healthy phases other than phase a1 and phase a1, I5 is the phase current matrix of the five healthy phases other than phase a1, R s is the phase resistance, L s is the phase self-inductance, ω is the electrical angular frequency, and j is the imaginary unit; The a1 phase exists in the relationship shown in formula (2): Where i f is the short-circuit current, R f is the resistance of the short circuit path; Combining formula (1) and formula (2), we can obtain the voltage formula (3) and current formula (4) of phase a1 when a turn-to-turn short circuit fault occurs: U a1 -U0=i a1h (R s +L s ωj)+E a1 +M5I5ωj-k if (R s +L s ωj) (3); Where U a1-healthy is the voltage of the healthy part of phase a1; Step 2: Considering the other five healthy motor phase windings, the voltage equation of the dual three-phase permanent magnet motor is shown in formula (5): Where M 6-6 is the mutual inductance matrix of the dual three-phase permanent magnet motor; The voltage equation when a turn-to-turn short circuit fault occurs in a dual three-phase permanent magnet motor is very similar to the voltage equation when no turn-to-turn short circuit fault occurs, except that there is an additional voltage U r : The voltage equation (5) when a turn-to-turn short circuit fault occurs is divided into two parts: the healthy part without a turn-to-turn short circuit fault and the excess voltage U r ; Step 3: When a dual three-phase balanced sinusoidal current is applied to the dual three-phase permanent magnet motor, the phase voltage is transformed to the d-axis and q-axis, wherein the healthy part is converted into a conventional DC component, U r Converted to formula (7): Where, T sr is the Clark-Park transformation matrix of dual three-phase permanent magnet motor; i f It is defined as the form of sinusoidal quadrature current shown in formula (8): Where, for i f The phase angle, I f for i f The amplitude of θ is the electrical angle, and according to formula (4) we can get I f The expression (9): Combining formulas (7), (8) and (9), we can further analyze U r The transformation is shown in formula (10): Where Z1 is the impedance, is the impedance angle, M1 is the mutual inductance between adjacent phase sequences, and M2 is the mutual inductance between two phase sequences separated by one phase; Step 4: Use the matrix T shown in formula (11) 2-0 Demodulate the signal shown in formula (10): T 2-0 The matrix converts the quadratic component into a DC signal and the DC signal into a negative quadratic component; Step 5: Use a low-pass filter to filter the signal to the secondary component, retaining only the DC component. The signal shown in formula (10) is converted to the signal U shown in formula (12) DC-keep : Step 5: Find signal U DC-keep The square sum of , and then perform square root calculation to obtain the fault signal F shown in formula (13) i : Step 6: The severity of the inter-turn short-circuit fault is obtained according to formula (14):

2. The online dual three-phase permanent magnet motor turn-to-turn short circuit fault detection method according to claim 1 is characterized in that The formulas for M5 and I5 are: Where M a1-b1 is the mutual inductance between phase a1 and phase b1, M a1-c1 is the mutual inductance between phase a1 and phase c1, M a1-a2 is the mutual inductance between phase a1 and phase a2, M a1-b2 is the mutual inductance between phase a1 and phase b2, M a1-c2 is the mutual inductance between phase a1 and phase c2, i b1 、i c1 、i a2 、i b2 、i c2 They are the currents of phases b1, c1, a2, b2, and c2 respectively.

3. The online dual three-phase permanent magnet motor turn-to-turn short circuit fault detection method according to claim 1 is characterized in that The M 6-6 The formula is:

4. The online dual three-phase permanent magnet motor turn-to-turn short circuit fault detection method according to claim 1 is characterized in that The T sr The formula is:

5. The online dual three-phase permanent magnet motor turn-to-turn short circuit fault detection method according to claim 1 is characterized in that The Z1, The formula is:

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