Dual three-phase permanent magnet synchronous motor inverter switching tube open-circuit fault diagnosis method

Abstract

The invention discloses a dual three-phase permanent magnet synchronous motor inverter switching tube open-circuit fault diagnosis method, which is specifically implemented according to the following steps: step 1, mapping six-phase current to an alpha-beta sub-plane related to electromechanical energy conversion and a z1-z2 harmonic sub-plane which does not participate in electromechanical energy conversion, a control strategy that z1-axis current given and z2-axis current given are both zero is adopted; 2, six-phase current is collected, a threshold value is set, whether the k phase breaks down or not is judged according to the threshold value, if the k phase is judged to be a fault phase, the step 3 is executed, and if the k phase is judged to be a normal phase, the step 4 is executed; 3, calculating a diagnosis mark corresponding to the fault phase, setting a fault threshold value, judging the fault type of the k phase according to the diagnosis mark and the fault threshold value, and skipping to the step 4; and step 4, outputting a fault diagnosis result. According to the invention, the problem of long diagnosis time of a current signal-based method in the prior art is solved.

Description

Technical Field

[0001] This invention belongs to the technical field of motor control methods, and relates to a method for diagnosing open-circuit faults in the switching transistors of dual three-phase permanent magnet synchronous motor inverters. Background Technology

[0002] In recent years, dual three-phase permanent magnet synchronous motors have shown broad application prospects due to their advantages such as low-voltage high-power output, low torque ripple, and high fault tolerance. Among the classifications of multiphase motors, dual three-phase motors with a 30° phase shift eliminate the 5th and 7th harmonic magnetomotive forces internally, thereby eliminating the 6th harmonic torque ripple. They have a greater advantage in suppressing torque ripple and have therefore been extensively studied.

[0003] With the increasing demands for system safety and operational stability in the industrial sector, research on inverter fault diagnosis for motor drive systems has become increasingly important. When an inverter malfunctions, rapid and accurate fault diagnosis can promptly identify the faulty component. This not only enables early fault handling and prevents the fault from escalating, but also provides a necessary prerequisite for the implementation of subsequent fault-tolerant control strategies.

[0004] Currently, commonly used fault diagnosis methods include analytical model-based, artificial intelligence-based, and signal-based methods. Model-based fault diagnosis methods require additional detection components such as observers; artificial intelligence-based methods require large amounts of data and high computational power. Signal-based fault diagnosis methods detect faults in drive systems by extracting and analyzing fault characteristic signals. Depending on the type of sampled signal, this method is mainly divided into voltage signal-based and current signal-based methods. Voltage signal-based methods typically require additional voltage detection devices, which not only significantly increases costs but also adds structural complexity and introduces more potential risks. To overcome the drawback of increased system complexity associated with voltage signal-based methods, current signal-based methods have been more widely studied. Compared to voltage signal acquisition, current signal acquisition is simpler. Current signal-based methods benefit from simple algorithms, are less affected by motor parameters, and do not require additional hardware circuitry, making them the most widely used fault diagnosis method.

[0005] Most current-signal-based diagnostic methods typically require measuring the average current over one cycle. These methods have inherent limitations, requiring one or more fundamental frequency cycles for diagnosis. This prolonged diagnosis time significantly impacts the response speed of fault diagnosis, potentially posing significant risks in real-world systems. Fast and accurate fault diagnosis is a prerequisite for the timely activation of fault-tolerant control strategies. If a system fault occurs, a long diagnosis time leads to low fault detection efficiency, preventing timely identification of faulty components and hindering the system's timely switch to fault-tolerant control mode. This results in missing the optimal fault-tolerant window and reducing system stability. If the system continues to operate in a faulty state, early localized faults may propagate due to delayed handling, eventually triggering cascading failures and severely compromising system safety and reliability. Diagnosis time significantly impacts the timeliness of fault-tolerant control; therefore, shortening fault diagnosis time is crucial for improving system reliability. Summary of the Invention

[0006] The purpose of this invention is to provide a method for diagnosing open-circuit faults in the switching transistors of dual three-phase permanent magnet synchronous motor inverters, which solves the problem that the existing current signal-based methods have long diagnosis times and seriously affect the response speed of fault diagnosis.

[0007] The technical solution adopted in this invention is a method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter, which is implemented according to the following steps: Step 1: Map the six-phase currents to the electromechanical energy conversion-related parameters. α-β In the z1-z2 harmonic subplane and the z1-z2 harmonic subplane that do not participate in electromechanical energy conversion, the z1-axis current is used as the reference. and z2 axis current given A control strategy where all values ​​are 0; Step 2, collect six-phase current Set a threshold and determine based on the threshold. k Whether a phase malfunction has occurred, if k If the phase is determined to be a faulty phase, proceed to step 3. k The phase is determined to be a normal phase; proceed to step 4. Step 3: Calculate the diagnostic flags corresponding to the fault, set the fault thresholds, and make judgments based on the diagnostic flags and fault thresholds. k Select the type of phase fault, then proceed to step 4; Step 4: Output the fault diagnosis results.

[0008] Preferably, step 1 specifically involves: using a vector space decoupling dual three-phase PMSM model, employing a four-dimensional current vector control method, and utilizing the vector space decoupling static transformation matrix. T 6s Mapping the six-phase currents to electromechanical energy conversionα- β In the z1-z2 harmonic subplane and the z1-z2 harmonic subplane that do not participate in electromechanical energy conversion, the z1-axis current is used as the reference. and z2 axis current given A control strategy where all values ​​are 0; The vector space decoupling static transformation matrix is ​​shown in equation (1): (1) in, α , β z1 and z2 are two mutually orthogonal fundamental wave vectors that together constitute the fundamental wave subplane related to electromechanical energy conversion; z1 and z2 are two mutually orthogonal 5th and 7th harmonic vectors that together constitute the 5th and 7th harmonic subplanes that only participate in losses; o1 and o2 are two mutually orthogonal 3rd harmonic vectors that together constitute the 3rd harmonic subplane. All of the 3rd harmonic vectors are zero-sequence component vectors. The current vector space decoupling process is as follows: (2) In the formula, , In the fundamental subplane α Current corresponding to the axis and β The current corresponding to the axis, , These represent the currents corresponding to the z1 axis and z2 axis of the 5th and 7th harmonic subplanes, respectively. , These represent the currents corresponding to the o1 and o2 axes in the third harmonic subplane, respectively. , , , , , The current of the motor AF is the six-phase current; According to the inverse transformation of equation (2), the phase current during normal operation of the motor is expressed as: (3).

[0009] Preferably, in step 2, six-phase current is collected. Previously, a fault flag for the switching transistor was set. and switch failure flag Given an initial value =0、 =0.

[0010] Preferably, in step 2, six-phase current is collected. back, k =A, B, C, D, E, F, and the six-phase currents of the motor are normalized to obtain... As shown in equation (4): (4) In the formula, The normalized six-phase currents, For unnormalized six-phase currents, and These are the d-axis and q-axis currents, respectively. Then to Calculate the moving average after taking the absolute value. , The calculation is shown in equation (5): (5) In the formula, For calculation Duration of the cycle used t It is a time variable.

[0011] Preferably, in step 2, a threshold is set and the judgment is made based on the threshold. k Whether a phase malfunction has occurred is specifically as follows: Set threshold , ,but: (6) That is, when <| I k ( t )|>∈[0, ε When 1], it is considered k A phase failure has occurred. k The phase is now identified as the faulty phase; When <| I k ( t )|>∈[0, ε When 1], it is considered k No phase failure occurred. k The phase is now determined to be the normal phase.

[0012] Preferably, the calculation of the diagnostic flags corresponding to the fault in step 3 specifically involves: Based on formula (3), since the fault phase current is 0 during the conduction time of the fault switch, then, after the fault... α- β The relationship between the currents in the z1-z2 subplane is shown in equation (7): (7) Based on the phase current after the fault and α-β The characteristics between the fundamental subplane current and the z1-z2 harmonic subplane current are used to construct the initial diagnostic indicators for each phase. The diagnostic indicators are calculated as shown in equation (8): (8) in, D A , D B , D C , D D , D E and D F These are the initial diagnostic flags corresponding to phases A through F of the motor; Then take D k moving average As diagnostic markers, specifically: (9) in, Diagnostic markers D k In the moving average period T The average value obtained within 2, To calculate < D k ( t > Duration of the cycle used.

[0013] Preferably, in step 3, a fault threshold is set, and then the diagnosis is made based on the diagnostic flag and the fault threshold. k The specific types of phase faults are as follows: Set threshold , When satisfied At that time, the diagnosis result was k Phase-on-phase switch open circuit fault; when the following conditions are met At that time, the diagnosis result was k The open circuit fault of the phase-down switching transistor is shown in equation (10): (10).

[0014] Preferably, before outputting the fault diagnosis results in step 4, the fault flag of the upper switching transistor is updated according to the fault situation. and switch failure flag Specifically: If no fault occurs, then the upper switch tube fault flag is displayed. and switch failure flag It remains at 0; When the diagnosis result is k When the phase switching transistor has an open circuit fault, =1; When the diagnosis result is k When the phase-down switching transistor has an open circuit fault, =2; Diagnostic results and , The relationship between them is shown in equation (11); (11).

[0015] Preferably, when outputting the fault diagnosis results in step 4, a fault flag is set. : (12) Will The value is used as a fault flag. k Fault conditions of different types of switching transistors; like k Corresponding fault signs That is to say This indicates k No phase fault; like k Corresponding fault signs That is to say This indicates that the fault diagnosis result is... k Phase-on-phase switch open circuit fault; like k Corresponding fault signs That is to say This indicates that the fault diagnosis result is... k Phase-down switch open circuit fault; like k Corresponding fault signs That is to say This indicates k A fault in which both upper and lower phase switching transistors are open-circuited simultaneously; Output fault flags This will give you the final fault diagnosis result for the corresponding phase.

[0016] Preferably, the present invention is applied to open circuit faults of switch tubes in dual three-phase permanent magnet synchronous motor inverters, mainly including open circuit faults of upper switch tubes, open circuit faults of lower switch tubes, open circuit faults of upper and lower switch tubes in the same bridge arm, and open circuit faults of switch tubes in two bridge arms of different sets of windings.

[0017] The beneficial effects of the present invention are: This invention enables accurate diagnosis of open circuit faults in the upper and lower switches, open circuit faults in the same bridge arm, and open circuit faults in different bridge arms (open circuit faults in the switches of two bridge arms that are not in the same set of windings). Compared with traditional diagnostic methods based on current signals, it can identify faults within one cycle, reducing fault diagnosis time, improving fault diagnosis efficiency, and is relatively simple to implement. Attached Figure Description

[0018] Figure 1 This is the main circuit topology of a dual three-phase permanent magnet synchronous motor system during normal operation; Figure 2 This is a schematic diagram of a fault where the upper switch transistor, the lower switch transistor, and both upper and lower switch transistors are open-circuited simultaneously; Figure 3 This is a block diagram of the vector control for a dual three-phase permanent magnet synchronous motor; Figure 4 This is a flowchart of the method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter according to the present invention; Figure 5(a) shows the theoretical current fault characteristics before and after the upper switch tube fault occurs in phase F in Example 6; Figure 5(b) shows the six-phase current waveforms before and after the open-circuit fault of the upper switch tube in phase F in Example 6; Figure 5(c) shows the situation before and after the open-circuit fault of the upper switch transistor in phase F in Example 6. i F Current waveform; Figure 5(d) shows the diagnostic results before and after the open circuit fault of the upper switch tube in phase F in Example 6; Figure 6(a) shows the theoretical current fault characteristics before and after the lower switch tube fault occurs in phase F in Example 6; Figure 6(b) shows the six-phase current waveforms before and after the open-circuit fault of the lower switch tube in phase F in Example 6; Figure 6(c) shows the situation before and after the open-circuit fault of the lower switch transistor in phase F in Example 6. i F Current waveform; Figure 6(d) shows the diagnostic results before and after the open circuit fault of the lower switch tube in phase F in Example 6; Figure 7(a) shows the theoretical current fault characteristics before and after the upper and lower switch tubes of phase F fail in Example 6; Figure 7(b) shows the six-phase current waveforms before and after the open-circuit fault of the upper and lower switching transistors in phase F in Example 6; Figure 7(c) shows the situation before and after the open-circuit fault of the upper and lower switching transistors in phase F in Example 6. i F Current waveform; Figure 7(d) shows the diagnostic results before and after the open circuit fault of the upper and lower switching transistors in phase F in Example 6; Figure 8(a) shows the six-phase current waveforms before and after the open-circuit fault of the upper switch of phase C and the lower switch of phase F in Example 6; Figure 8(b) shows the situation before and after an open-circuit fault in the upper switch of phase C and the lower switch of phase F in Example 6. i C Current waveform; Figure 8(c) shows the situation before and after an open-circuit fault in the upper switch of phase C and the lower switch of phase F in Example 6. i F Current waveform; Figure 8(d) shows the diagnostic results before and after the open circuit fault of the upper switch tube of phase C and the lower switch tube of phase F in Example 6; Detailed Implementation The following detailed description is provided in conjunction with specific implementation methods.

[0019] Example 1 The present invention provides a method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter. The process is as follows: Figure 4 As shown, the specific steps are as follows: Step 1: Map the six-phase currents to the electromechanical energy conversion-related parameters. α-β In the z1-z2 harmonic subplane and the z1-z2 harmonic subplane that do not participate in electromechanical energy conversion, the z1-axis current is used as the reference. and z2 axis current given A control strategy where all values ​​are 0; Step 2, collect six-phase current Set a threshold and determine based on the threshold. k Whether a phase malfunction has occurred, if k If the phase is determined to be a faulty phase, proceed to step 3. k The phase is determined to be a normal phase; proceed to step 4. Step 3: Calculate the diagnostic flags corresponding to the fault, set the fault thresholds, and make judgments based on the diagnostic flags and fault thresholds. k Select the type of phase fault, then proceed to step 4; Step 4: Output the fault diagnosis results.

[0020] Example 2 Based on step 1, a vector control system for a dual three-phase permanent magnet synchronous motor with a 30° phase shift and isolated neutral point is constructed. The main circuit topology is as follows: Figure 1 As shown, this invention mainly addresses open-circuit faults in the upper and lower switching transistors, open-circuit faults in the upper and lower switching transistors of the same bridge arm, and open-circuit faults in switching transistors of different bridge arms (open-circuit faults in the switching transistors of two bridge arms that are not in the same winding). Figure 2 As shown, step 1 specifically involves: using a two-phase three-phase PMSM model based on vector space decoupling, and employing a four-dimensional current vector control method. The vector control block diagram is shown below. Figure 3 As shown, the static transformation matrix is ​​decoupled using vector space. T 6s Mapping the six-phase currents to electromechanical energy conversion α-β In the z1-z2 harmonic subplane and the z1-z2 harmonic subplane that do not participate in electromechanical energy conversion, the z1-axis current is used as the reference to minimize stator copper losses. and z2 axis current given A control strategy where all values ​​are 0; The vector space decoupling static transformation matrix is ​​shown in equation (1): (1) in, α , β z1 and z2 are two mutually orthogonal fundamental wave vectors that together constitute the fundamental wave subplane related to electromechanical energy conversion; z1 and z2 are two mutually orthogonal 5th and 7th harmonic vectors that together constitute the 5th and 7th harmonic subplanes that only participate in losses; o1 and o2 are two mutually orthogonal 3rd harmonic vectors that together constitute the 3rd harmonic subplane. All of the 3rd harmonic vectors are zero-sequence component vectors. The current vector space decoupling process is as follows: (2) In the formula, , In the fundamental subplane α Current corresponding to the axis and β The current corresponding to the axis, , These represent the currents corresponding to the z1 axis and z2 axis of the 5th and 7th harmonic subplanes, respectively. , These represent the currents corresponding to the o1 and o2 axes in the third harmonic subplane, respectively. , , , , , The current of the motor AF is the six-phase current; According to the inverse transformation of equation (2), the phase current during normal operation of the motor is expressed as: (3).

[0021] Example 3 Based on Example 2, six-phase current is collected in step 2. Previously, a fault flag for the switching transistor was set. and switch failure flag Given an initial value =0、 =0.

[0022] Step 2 involves collecting six-phase current. back, k =A, B, C, D, E, F. To quickly and accurately identify the location of the faulty switch transistor, a fault phase location circuit is introduced, which analyzes the six-phase current of the motor. Normalization process is performed to obtain To improve the reliability and robustness of the fault location circuit, as shown in equation (4): (4) In the formula, The normalized six-phase currents, For unnormalized six-phase currents, and These are the d-axis and q-axis currents, respectively. right To ensure the accuracy and reliability of the fault location process, the following steps are taken. Calculate the moving average after taking the absolute value. , The calculation is shown in equation (5): (5) In the formula, For calculation Duration of the cycle used t It is a time variable, period. T The selection of option 1 requires a trade-off between the speed and accuracy of fault phase localization: T 1. Selecting an excessively large value will reduce the speed of fault phase location; T If the selected cycle is too small, it will affect the accuracy of fault phase location. Therefore, it is necessary to select an appropriate cycle based on the actual situation. T 1.

[0023] In step 2, a threshold is set and a judgment is made based on the threshold. k Whether a phase malfunction has occurred is specifically as follows: Ideally, k When no phase fault occurs, <| I k ( t )|> greater than zero; while k When a phase fault occurs, <| I k ( t )|> equals zero, <| I k ( t The results of |> will inevitably fluctuate due to various internal and external factors, therefore it is necessary to set an appropriate threshold. ε 1. To improve the accuracy of fault phase location; according to <| I k (t The range of values ​​for |> can effectively distinguish between fault phases and normal phases, as shown in equation (6): Set threshold , ,but: (6) That is, when <| I k ( t )|>∈[0, ε When 1], it is considered k A phase failure has occurred. k The phase is now identified as the faulty phase; When <| I k ( t )|>∈[0, ε When 1], it is considered k No phase failure occurred. k The phase is now determined to be the normal phase.

[0024] Example 4 Based on Example 3, step 3 specifically calculates the diagnostic flags corresponding to the fault as follows: Based on formula (3), since the fault phase current is 0 during the conduction time of the fault switch, then, after the fault... α- β The relationship between the currents in the z1-z2 subplane is shown in equation (7): (7) Based on the phase current after the fault and α-β The characteristics between the fundamental subplane current and the z1-z2 harmonic subplane current are used to construct the initial diagnostic indicators for each phase. The diagnostic indicators are calculated as shown in equation (8): (8) in, D A , D B , D C , D D , D E and D F These are the initial diagnostic flags corresponding to phases A through F of the motor; When the fault location circuit diagnoses k After a phase failure occurs, calculate the corresponding diagnostic flags. D k In utilizing Dk When performing fault diagnosis, because there are certain signal deviations and disturbances during current signal acquisition, it is not possible to simply acquire the signal at a single moment. D k The value is used for judgment. In order to reduce the interference of internal and external factors and ensure the accuracy of the data, the value is selected. D k moving average As diagnostic markers, specifically: (9) in, Diagnostic markers D k In the moving average period T The average value obtained within 2, For calculation Duration of the cycle used, cycle T 2. Selecting an excessively large cycle will slow down fault diagnosis, while selecting an excessively small cycle will affect the accuracy of fault diagnosis. Therefore, it is necessary to select an appropriate cycle based on the actual situation. T 2.

[0025] In step 3, a fault threshold is set, and then a judgment is made based on the diagnostic flags and the fault threshold. k The specific types of phase faults are as follows: To eliminate the effects of signal deviations and disturbances during data acquisition, it is necessary to set an appropriate fault threshold. To improve the accuracy of fault diagnosis, a threshold is set. , When satisfied At that time, the diagnosis result was k Phase-on-phase switch open circuit fault; when the following conditions are met At that time, the diagnosis result was k The open circuit fault of the phase-down switching transistor is shown in equation (10): (10).

[0026] Preferably, before outputting the fault diagnosis results in step 4, the fault flag of the upper switching transistor is updated according to the fault situation. and switch failure flag Specifically: If no fault occurs, then the upper switch tube fault flag is displayed. and switch failure flag It remains at 0; When the diagnosis result is k When the phase switching transistor has an open circuit fault, =1; When the diagnosis result is kWhen the phase-down switching transistor has an open circuit fault, =2; Diagnostic results and , The relationship between them is shown in equation (11); (11).

[0027] Example 5 Based on Example 4, when outputting the fault diagnosis results in step 4, a fault flag is set. : (12) Will The value is used as a fault flag. k Fault conditions of different types of switching transistors; like k Corresponding fault signs That is to say This indicates k No phase fault; like k Corresponding fault signs That is to say This indicates that the fault diagnosis result is... k Phase-on-phase switch open circuit fault; like k Corresponding fault signs That is to say This indicates that the fault diagnosis result is... k Phase-down switch open circuit fault; like k Corresponding fault signs That is to say This indicates k A fault in which both upper and lower phase switching transistors are open-circuited simultaneously; Output fault flags This will give you the final fault diagnosis result for the corresponding phase. G k The fault diagnosis results corresponding to different values ​​are shown in Table 1.

[0028] Table 1 Fault Diagnosis Results

[0029] This invention focuses on a dual three-phase PMSM with a 30° phase shift at the isolated neutral point. Based on Kirchhoff's current law, the two sets of windings of the motor respectively satisfy the following current constraint conditions: i A + i B + iC =0 and i D + i E + i F =0. Assuming that two arms of the same winding experience an open-circuit fault, the fault will cause the phase current in both phases to be zero. Under the constraint of Kirchhoff's current law, the current in the normal phase of this winding will also be forced to zero. In this case, the current signal of the normal phase will exhibit the same characteristics as the faulty phase, leading to misdiagnosis. Therefore, the fault diagnosis method studied in this invention is not applicable to the situation where two arms of the same winding experience an open-circuit fault.

[0030] However, the fault diagnosis method of this invention is still applicable to cases where the switching transistors of two bridge arms of different windings are open-circuited. Ignoring the case where the fault occurs in two bridge arms of the same winding, the fault diagnosis of the six phases of the motor is decomposed into six independent processes due to the introduction of the fault phase location step. In this case, the diagnosis of an open-circuit fault in the switching transistors of two bridge arms of different windings can be transformed into the diagnosis of an open-circuit fault in two switching transistors.

[0031] Example 6 Based on Example 5, to verify the effectiveness of the diagnostic method of the present invention, a fault diagnosis model of a dual three-phase PMSM with an isolated neutral point phase shift of 30° was built using MATLAB / Simulink. The simulation parameters were set as follows: stator resistance was... Both the direct and quadrature axis inductances are 2.04. The permanent magnet flux is The number of pole pairs is 4, the DC bus voltage is 200V, the given motor speed is 500r / min, the given load torque is 5Nm, the sampling period is 0.0001s, and the simulation duration is 0.2s. In the simulation, the calculation of <| I k ( t When |>, the moving average period T 1 is set to 3ms; calculation < D k ( t When )>, the moving average period T 2 is set to 1ms. This invention utilizes a fault diagnosis model to diagnose open-circuit faults of the upper switch transistor, open-circuit faults of the lower switch transistor, open-circuit faults of the upper and lower switches transistors of the same bridge arm, and open-circuit faults of switches transistors of different bridge arms (open-circuit faults of switches transistors of two bridge arms that are not in the same set of windings), in order to verify the correctness of this invention.

[0032] First, simulation analysis was conducted for open circuit faults of the upper switch transistor, open circuit faults of the lower switch transistor, and open circuit faults of the upper and lower switches transistors of the same bridge arm. Taking the open circuit faults of the upper switch transistor of phase F, the open circuit faults of the lower switch transistor of phase F, and the open circuit faults of the upper and lower switches transistors of phase F as examples, the effectiveness of the present invention for inverter switch transistor open circuit faults was verified.

[0033] The theoretical current waveforms before and after the open-circuit fault of the upper switch transistor in phase F are shown in Figure 5(a). The fault is set to occur at 0.095s. The six-phase current waveforms before and after the fault are shown in Figure 5(b). The current waveform is shown in Figure 5(c), and the diagnostic results before and after the fault are shown in Figure 5(d). As can be seen from Figure 5(b), the phase current waveform has good sinusoidal properties during normal motor operation, but significant distortion occurs after the fault occurs, as shown in Figure 5(c). The current waveform is consistent with the theoretical waveform in Figure 5(a). At 0.095s, due to the phase current of phase F... During the negative half-cycle, an open-circuit fault in the F-phase switch will not affect motor operation; the motor will continue to operate normally. The current distortion caused by the open-circuit fault in the F-phase switch does not actually occur until 0.103 seconds later, during the positive half-cycle. The value changes to 0. As shown in Figure 5(d), when an open-circuit fault occurs in the switch transistor of phase F, the fault flag of phase F changes to 0 at 0.1084 s. The value changes from 0 to 1, thus diagnosing an open circuit fault in phase F. The diagnosis time is 5.4ms. The fault flags for the other five phases remain at 0, indicating that no faults have occurred in the other five phases.

[0034] The theoretical current waveforms before and after a switching open-circuit fault in phase F are shown in Figure 6(a). The fault is assumed to occur at 0.095s. The six-phase current waveforms before and after the fault are shown in Figure 6(b). The current waveform is shown in Figure 6(c), and the diagnostic results before and after the fault are shown in Figure 6(d). As can be seen from Figure 6(b), the phase current waveform has good sinusoidal properties during normal motor operation, but significant distortion occurs after the fault occurs, as shown in Figure 6(c). The current waveform is consistent with the theoretical waveform in Figure 6(a). At 0.095s, the switch transistor in phase F experiences an open-circuit fault, and the phase current of phase F in the negative half-cycle... The value changes to 0. As shown in Figure 6(d), when a fault occurs in phase F due to an open-circuit fault in the lower switching transistor, the phase F fault flag changes to 0 at 0.0991s. The value changes from 0 to 2, thus diagnosing an open circuit fault in phase F. The diagnosis time is 4.1ms. The fault flags for the other five phases remain at 0, indicating that no faults have occurred in the other five phases.

[0035] The theoretical current waveforms before and after the open-circuit fault of the upper and lower switching transistors in phase F are shown in Figure 7(a). The fault is set to occur at 0.095s. The six-phase current waveforms before and after the fault are shown in Figure 7(b). The current waveform is shown in Figure 7(c), and the diagnostic results before and after the fault are shown in Figure 7(d). As can be seen from Figure 7(b), the phase current waveform has good sinusoidal properties during normal motor operation, but significant distortion occurs after the fault occurs, as shown in Figure 7(c). The current waveform is consistent with the theoretical waveform in Figure 7(a). At 0.095s, a fault occurs where both the upper and lower switches of phase F are simultaneously open-circuited. The phase current of phase F during the positive and negative half-cycles is... All values ​​become 0. After a simultaneous open-circuit fault occurs in phase F, the phase F fault flag changes to 0 at 0.0991s. It changed from 0 to 2, and then at 0.1054s, The value was changed from 2 to 3, thus diagnosing a fault in phase F where the upper and lower switching transistors were simultaneously open. The diagnosis time was 10.4ms. The fault flags for the other five phases remained at 0, indicating that no faults had occurred in the other five phases.

[0036] Next, based on the established fault diagnosis model, simulation analysis will be conducted for open-circuit faults of different bridge arm switches (open-circuit faults of two bridge arm switches not in the same winding). It is assumed that an open-circuit fault occurs at 0.095s for the upper switch of phase C and the lower switch of phase F. The six-phase current waveforms before and after the fault are shown in Figure 8(a). The current waveform is shown in Figure 8(b), before and after the fault. The current waveform is shown in Figure 8(c), and the diagnostic results before and after the fault are shown in Figure 8(d). As can be seen from Figure 8(a), the phase current waveform has good sinusoidal properties during normal motor operation, but significant distortion occurs after the fault. From Figures 8(a) and (b), it can be seen that at 0.095s, due to the C-phase current... During the negative half-cycle, an open-circuit fault in the upper switch of phase C will not affect the motor operation. Simultaneously, an open-circuit fault in the lower switch of phase F will affect the phase current of phase F during the negative half-cycle. The current drops to 0, at which point the motor can be considered to be operating under conditions where only the open-circuit fault of the switch transistor on phase F occurs. The current distortion caused by the open-circuit fault of the switch transistor on phase C doesn't actually occur until 0.1 seconds later, during the positive half-cycle. i C It becomes 0. As can be seen from Figure 8(d), at 0.1057s, the fault indicator of phase C... The indicator changed from 0 to 1, thus diagnosing an open-circuit fault in phase C's upper switching transistor, with a diagnosis time of 5.7 ms; at 0.0991 s, the fault flag in phase F... The value changes from 0 to 2, thus diagnosing an open circuit fault in phase F. The diagnosis time is 4.1ms, while the diagnostic flags for the other four phases remain at 0, indicating that no faults have occurred in the other four phases.

[0037] The simulation results above demonstrate that the fault diagnosis method studied in this invention can quickly and accurately diagnose open circuit faults in the upper switch, lower switch, upper and lower switch on the same bridge arm, and switch on different bridge arms (open circuit faults in two bridge arms of different windings) in a dual three-phase PMSM drive system with a 30° phase shift at the isolated neutral point, without misdiagnosis. This verifies the correctness and effectiveness of the method in diagnosing open circuit faults in the switch of a dual three-phase permanent magnet synchronous motor inverter.

Claims

1. A method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter, characterized in that, The specific steps are as follows: Step 1: Map the six-phase currents to the electromechanical energy conversion-related parameters. α-β In the z1-z2 harmonic subplane and the z1-z2 harmonic subplane that do not participate in electromechanical energy conversion, the z1-axis current is used as the reference. and z2 axis current given A control strategy where all values ​​are 0; Step 2, collect six-phase current Set a threshold and determine based on the threshold. k Whether a phase malfunction has occurred, if k If the phase is determined to be a faulty phase, proceed to step 3. k The phase is determined to be a normal phase; proceed to step 4. Step 3: Calculate the diagnostic flags corresponding to the fault, set the fault thresholds, and make judgments based on the diagnostic flags and fault thresholds. k Select the type of phase fault, then proceed to step 4; Step 4: Output the fault diagnosis results.

2. The method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter according to claim 1, characterized in that, Step 1 specifically involves: using a vector space decoupling dual three-phase PMSM model, employing a four-dimensional current vector control method, and utilizing the vector space decoupling static transformation matrix. T 6s Mapping the six-phase currents to electromechanical energy conversion α-β In the z1-z2 harmonic subplane and the z1-z2 harmonic subplane that do not participate in electromechanical energy conversion, the z1-axis current is used as the reference. and z2 axis current given A control strategy where all values ​​are 0; The vector space decoupling static transformation matrix is ​​shown in equation (1): （1） in, α , β z1 and z2 are two mutually orthogonal fundamental wave vectors that together constitute the fundamental wave subplane related to electromechanical energy conversion; z1 and z2 are two mutually orthogonal 5th and 7th harmonic vectors that together constitute the 5th and 7th harmonic subplanes that only participate in losses; o1 and o2 are two mutually orthogonal 3rd harmonic vectors that together constitute the 3rd harmonic subplane. All of the 3rd harmonic vectors are zero-sequence component vectors. The current vector space decoupling process is as follows: （2） In the formula, , In the fundamental subplane α Current corresponding to the axis and β The current corresponding to the axis, , These represent the currents corresponding to the z1 axis and z2 axis of the 5th and 7th harmonic subplanes, respectively. , These represent the currents corresponding to the o1 and o2 axes in the third harmonic subplane, respectively. , , , , , The current of the motor AF is the six-phase current; According to the inverse transformation of equation (2), the phase current during normal operation of the motor is expressed as: （3）。 3. The method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter according to claim 2, characterized in that, In step 2, six-phase current is collected. Previously, a fault flag for the switching transistor was set. and switch failure flag Given an initial value =0、 =0.

4. The method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter according to claim 3, characterized in that, In step 2, six-phase current is collected. back, k =A, B, C, D, E, F, for the six phases of the motor The phase current is normalized to obtain As shown in equation (4): （4） In the formula, The normalized six-phase currents, For unnormalized six-phase currents, and These are the d-axis and q-axis currents, respectively. Then to Calculate the moving average after taking the absolute value. , The calculation is shown in equation (5): （5） In the formula, For calculation Duration of the cycle used t It is a time variable.

5. The method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter according to claim 4, characterized in that, In step 2, a threshold is set and the judgment is made based on the threshold. k Whether a phase malfunction has occurred is specifically as follows: Set threshold , ,but: （6） That is, when <| I k ( t )|>∈[0, ε When 1], it is considered k A phase failure has occurred. k The phase is now identified as the faulty phase; When <| I k ( t )|>∈[0, ε When 1], it is considered k No phase failure occurred. k The phase is now determined to be the normal phase.

6. The method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter according to claim 5, characterized in that, The specific steps for calculating the diagnostic flags corresponding to the fault in step 3 are as follows: Based on formula (3), since the fault phase current is 0 during the conduction time of the fault switch, then, after the fault... α-β The relationship between the currents in the z1-z2 subplane is shown in equation (7): （7） Based on the phase current after the fault and α-β The characteristics between the fundamental subplane current and the z1-z2 harmonic subplane current are used to construct the initial diagnostic indicators for each phase. The diagnostic indicators are calculated as shown in equation (8): （8） in, D A , D B , D C , D D , D E and D F These are the initial diagnostic flags corresponding to phases A through F of the motor; Then take D k moving average As diagnostic markers, specifically: （9） in, Diagnostic markers D k In the moving average period T The average value obtained within 2, For calculation Duration of the cycle used.

7. The method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter according to claim 6, characterized in that, In step 3, a fault threshold is set, and then a judgment is made based on the diagnostic flag and the fault threshold. k The specific types of phase faults are as follows: Set threshold , When satisfied At that time, the diagnosis result was k Phase-on-phase switch open circuit fault; when the following conditions are met At that time, the diagnosis result was k The open circuit fault of the phase-down switching transistor is shown in equation (10): （10）。 8. The method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter according to claim 7, characterized in that, Before outputting the fault diagnosis results in step 4, the fault flag of the upper switching transistor is updated according to the fault situation. and switch failure flag Specifically: If no fault occurs, then the upper switch tube fault flag is displayed. and switch failure flag It remains at 0; When the diagnosis result is k When the phase switching transistor has an open circuit fault, =1; When the diagnosis result is k When the phase-down switching transistor has an open circuit fault, =2; Diagnostic results and , The relationship between them is shown in equation (11); (11)。 9. The method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter according to claim 8, characterized in that, When outputting the fault diagnosis results in step 4, a fault flag is set. : (12) Will The value is used as a fault flag. k Fault conditions of different types of switching transistors; like k Corresponding fault signs That is to say This indicates k No phase fault; like k Corresponding fault signs That is to say This indicates that the fault diagnosis result is... k Phase-on-phase switch open circuit fault; like k Corresponding fault signs That is to say This indicates that the fault diagnosis result is... k Phase-down switch open circuit fault; like k Corresponding fault signs That is to say This indicates k A fault in which both upper and lower phase switching transistors are open-circuited simultaneously; Output fault flags This will give you the final fault diagnosis result for the corresponding phase.

10. The method for diagnosing open-circuit faults in the switching transistors of a dual three-phase permanent magnet synchronous motor inverter according to claim 9, characterized in that, This is applied to open circuit faults of switching transistors in dual three-phase permanent magnet synchronous motor inverters, mainly including open circuit faults of the upper switching transistor, open circuit faults of the lower switching transistor, open circuit faults of the upper and lower switching transistors of the same bridge arm, and open circuit faults of the switching transistors of the two bridge arms of different windings.

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