Harmonic sub-plane current-based six-phase permanent magnet synchronous motor winding open-circuit fault diagnosis method

Abstract

The invention discloses a six-phase permanent magnet synchronous motor winding open-circuit fault diagnosis method based on harmonic sub-plane current, belongs to the technical field of multi-phase motor winding fault diagnosis, and aims to solve the problem of high probability of misdiagnosis in existing six-phase motor open-circuit fault detection. The method comprises the following steps: firstly, carrying out vector transformation on collected six-phase current to obtain corresponding harmonic current under three sub-planes; then, characteristic parameters capable of reflecting the health state of the winding are obtained through harmonic sub-plane current calculation, the parameters are improved and optimized, the three stages of filtering processing, partial period averaging and threshold value comparison are included, and the fault characteristic quantity of each phase of winding of the motor is further obtained. And finally, judging whether an open-circuit fault occurs or not and positioning a fault phase according to the value of the fault characteristic quantity. The method is suitable for diagnosing all fault types of one-phase and two-phase open circuits of the six-phase motor.

Description

Technical Field

[0001] The invention relates to a method for diagnosing an open-circuit fault of a six-phase permanent magnet synchronous motor winding based on harmonic sub-plane current, and belongs to the technical field of multi-phase motor winding fault diagnosis. Background Art

[0002] With the continuous development of aviation and aerospace, the motor drive system, as one of the core elements that determine the performance of aircraft, has been widely studied. Since aircraft operate in a low-temperature and low-pressure high-altitude environment for a long time, their operating environment is more demanding than ground conditions. In order to ensure the smooth completion of flight missions, higher requirements are placed on the stability, reliability, and fault tolerance of the motor drive system. At present, multi-phase motors are increasingly used in aircraft motor drive systems due to their high fault tolerance, high power density, and wide speed regulation range.

[0003] Due to the long-term complex and harsh working environment, the probability of permanent magnet synchronous motor failure is greatly increased. Among them, when the winding open circuit fault occurs, the motor winding current is no longer balanced, and the motor will be accompanied by a certain degree of vibration and abnormal noise when running. In severe cases, the motor may even be damaged and shut down, causing damage to the entire system. Fault diagnosis is one of the key links in the fault-tolerant control of permanent magnet synchronous motors. The result of fault diagnosis is a necessary condition for determining whether to adopt fault-tolerant control and what fault-tolerant control strategy to adopt. Therefore, the accuracy and real-time performance of fault diagnosis are particularly important.

[0004] The fault characteristic quantity used in the open-circuit fault diagnosis method based on harmonic sub-plane current is mainly composed of the corresponding currents in the fundamental sub-plane α-β and the harmonic sub-plane z1-z2, ignoring the zero-sequence current in the zero-sequence space sub-plane o1-o2. After an open-circuit fault occurs in the motor, the zero-sequence current will also change due to the destruction of balance, which will increase the probability of misdiagnosis due to sudden changes in speed and load. At the same time, due to the particularity of the winding structure of the positive six-phase motor, the fault characteristic quantity of the traditional method cannot correctly reflect the open-circuit fault of the two-phase winding of the six-phase motor separated by 180°. Summary of the invention

[0005] In view of the problem that the existing six-phase motor open circuit fault detection has a high probability of misdiagnosis, the present invention provides a six-phase permanent magnet synchronous motor winding open circuit fault diagnosis method based on harmonic sub-plane current.

[0006] The present invention discloses a method for diagnosing an open-circuit fault of a six-phase permanent magnet synchronous motor winding based on harmonic sub-plane current. The winding structure of the motor is a six-phase winding symmetrically distributed and connected through a neutral point. The method comprises the following steps:

[0007] Step 1: Information collection: The collected currents of each phase of the six-phase permanent magnet synchronous motor are filtered through a low-pass filter; then the filtered currents of each phase i a 、i b 、i c 、i d 、i e 、i f Perform vector transformation to obtain three mutually orthogonal sub-planes, among which the current corresponding to the fundamental wave sub-plane α-β is i α 、i β ; The current corresponding to the harmonic sub-plane z1-z2 is i z1 、i z2 ; The current corresponding to the zero-sequence space sub-plane o1-o2 is i o1 、i o2 ;

[0008] Step 2: Calculation of fault characteristic quantities:

[0009] First, the characteristic parameter η reflecting the health status of each phase winding is calculated based on the currents of the three sub-planes. n , n=a,b,c,d,e,f:

[0010]

[0011] Where δ is a positive real number and must satisfy the following formula:

[0012]

[0013] In the formula, I m is the phase current amplitude;

[0014] Secondly, the characteristic parameter η n Perform filtering and output the filtered characteristic parameter η n1 ;

[0015] Again, the characteristic parameter η after filtering n1 The average value η is obtained by integrating the following formula n2 :

[0016]

[0017] T v = k * T s (k≤1)

[0018] Where, T s is the electrical cycle value, T v is the integration period, k is the ratio of the integration period to the entire electrical period;

[0019] Finally, the fault characteristic quantity FI of each phase used to diagnose the winding open circuit fault is obtained. n :

[0020]

[0021] In the formula, ε is the set threshold, which is a positive number close to 0. The value range of the set threshold ε is 0.8-1;

[0022] Step 3: Open circuit fault diagnosis and location processing:

[0023] According to the fault feature FI obtained in step 2 n Determine whether an open circuit fault occurs in the nth phase, FI n =1 indicates an open circuit fault occurs in the nth phase, FI n =0 indicates that no open circuit fault occurs in the nth phase, and the process returns to step 1 to continue monitoring.

[0024] Preferably, the current corresponding to the fundamental wave sub-plane α-β is i α 、i β , the current corresponding to the harmonic sub-plane z1-z2 is i z1 、i z2 , the current corresponding to the zero-sequence space sub-plane o1-o2 is i o1 、i o2 Obtained by the following transformation:

[0025]

[0026] Preferably, in step 2, the characteristic parameter η n Perform filtering and output the filtered characteristic parameter η n1 The process is:

[0027]

[0028] In the formula, 2λ is the filter bandwidth, and η n The peak pulse amplitude is limited to no more than η n 1.5 times the theoretical maximum value, which must satisfy: λ≤0.5.

[0029] Preferably, in step 2, δ, λ, k, and ε are associated and set to 1, 0.5, 1 / 12, and 0.85, respectively.

[0030] Preferably, the method is applicable to diagnosing single-phase open circuit and two-phase open circuit faults of a positive six-phase motor, a total of 21 faults, wherein the two-phase open circuit fault includes two-phase windings open circuit at 60°, open circuit at 120° and open circuit at 180°.

[0031] Beneficial effects of the present invention:

[0032] 1. The six-phase permanent magnet synchronous motor winding open circuit fault diagnosis method based on harmonic sub-plane current proposed in the present invention does not require the addition of additional sensors or other hardware equipment, and is simple and easy to implement.

[0033] 2. The six-phase permanent magnet synchronous motor winding open circuit fault diagnosis method based on harmonic sub-plane current proposed in the present invention obtains the fault characteristic quantity through a series of optimizations such as filtering the characteristic parameters, averaging the partial cycles, and comparing the threshold values. The fault characteristic quantity is not easily affected by factors such as motor speed and load mutation, thus reducing the probability of misdiagnosis and having good robustness.

[0034] 3. The six-phase permanent magnet synchronous motor winding open circuit fault diagnosis method based on harmonic sub-plane current proposed in the present invention can realize single-phase open circuit and two-phase open circuit fault detection and positioning, and effectively shorten the diagnosis time and improve the system reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The phasor diagram of the six-phase permanent magnet synchronous motor of the present invention;

[0036] Figure 2 This is a structural block diagram of the vector control system of a six-phase permanent magnet synchronous motor of the present invention;

[0037] Figure 3 It is a schematic diagram of the fault diagnosis process of the present invention;

[0038] Figure 4 A schematic diagram of an optimization process for obtaining fault characteristic quantities according to the present invention;

[0039] Figure 5 A motor current waveform diagram according to an embodiment of the present invention;

[0040] Figure 6 This is a characteristic quantity change diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0043] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0044] Specific implementation method 1: The following is combined Figures 1 to 6 The present embodiment is described. The method for diagnosing an open-circuit fault of a six-phase permanent magnet synchronous motor winding based on harmonic sub-plane current described in the present embodiment includes three steps: information collection, fault characteristic quantity calculation, and open-circuit fault diagnosis and positioning processing.

[0045] like Figure 1 , which is a winding structure diagram of the motor of the present invention, the six-phase windings are symmetrically distributed in space and connected into a Y-type structure through a common neutral point.

[0046] Based on this, Figure 2 As shown in FIG. 1 , it is a structural block diagram of the vector control system of the motor of the present invention. In order to ensure good control effect and easy implementation of the algorithm, the motor is regarded as a system of two sets of three-phase windings, that is, the phases in each set of windings are separated by 120° electrical angle, and the corresponding phases between the two sets of windings are separated by 60° electrical angle. The MPTA vector control strategy is adopted. According to the detected six-phase current and the electrical angle θ rotated by the motor, two sets of fundamental current i in the rotating coordinate system are obtained after coordinate transformation. d1 、i q1 and i d2 、i q2 , respectively with the preset given value I d1_ref ,I q1_ref ,I d2_ref ,I q2_ref Since the two sets of windings are not completely independent, they share a neutral point, which has one less degree of freedom than the traditional dual three-phase system, thus increasing the control of zero-sequence current i o1 、i o2 Constraints can be used to improve system stability and harmonic suppression capabilities. o1 、i o2 With the preset given value I o1_ref ,I o2_ref For comparison. d1 、i q1 、i o1 and d2 、i q2 、i o2 The two sets of differences after comparison are respectively passed through the PI regulator to obtain the given voltage u in the rotating coordinate system. d1 、u d1 and u d2 、u q2 At the same time, according to the electrical angular velocity ω of the motor, feedforward voltage compensation is added to the control system to achieve decoupling control between the dq axes.

[0047] Based on this, Figure 3FIG. 1 is a flow chart of a method for diagnosing an open-circuit fault of a six-phase permanent magnet synchronous motor winding based on harmonic sub-plane current according to the present invention, and the specific implementation steps are as follows:

[0048] Step 1: Information collection: The collected currents of each phase of the six-phase permanent magnet synchronous motor are filtered through a low-pass filter; then the filtered currents of each phase i a 、i b 、i c 、i d 、i e 、i f Perform vector transformation to obtain three mutually orthogonal sub-planes, among which the current corresponding to the fundamental wave sub-plane α-β is i α 、i β ; The current corresponding to the harmonic sub-plane z1-z2 is i z1 、i z2 ; The current corresponding to the zero-sequence space sub-plane o1-o2 is i o1 、i o2 ;

[0049] Among them, by i a 、i b 、i c 、i d 、i e 、i f Get i α 、i β 、i z1 、i z2 、i o1 、i o2 The vector transformation process is:

[0050]

[0051] Step 2: Calculate the fault characteristic quantity: Input the current of the three sub-planes into the fault characteristic quantity calculation module, and first calculate the characteristic parameter η reflecting the health status of the winding n (n=a,b,c,d,e,f), then the characteristic parameter η n After three optimization stages of filtering, partial cycle averaging and threshold comparison, the fault characteristic quantity FI of each phase winding is finally obtained. n (n=a,b,c,d,e,f).

[0052] First calculate the characteristic parameter η n (n=a,b,c,d,e,f), the calculation formula is as follows:

[0053]

[0054] Where δ is a positive real number and must satisfy the following formula:

[0055]

[0056] In the formula, I m is the phase current amplitude, and in this embodiment, the value of δ is 1. The purpose of introducing δ is to prevent the numerator and denominator of the characteristic parameter of the corresponding phase from being simultaneously and continuously 0 when two phases separated by 180° are open-circuited, thereby affecting the diagnosis effect.

[0057] In order to simplify the diagnosis method, η n Optimize the processing, Figure 4 FIG. 1 is a schematic diagram of a series of optimization processes for obtaining fault characteristic quantities according to the present invention.

[0058] When η n When the denominator of is too small and close to 0, η n It is easy to have spike pulses, which may lead to misdiagnosis. Therefore, filtering is used to filter out η n The spike pulse contained in the first optimization process quantity η n1 (n=a,b,c,d,e,f). The processing process is:

[0059]

[0060] The first stage is to transform the characteristic parameter η n Perform filtering: where η n1 (n=a,b,c,d,e,f) is the characteristic parameter η n The first optimization process quantity is 2λ, which is the filter bandwidth. n The peak pulse amplitude is limited to no more than η n 1.5 times the theoretical maximum value, must meet the following requirements:

[0061] λ≤0.5

[0062] In this embodiment, the value of λ is 0.5.

[0063] The second optimization stage is to n1 Integrate and average: To obtain a relatively stable characteristic parameter value, η n1 Integrate and calculate the average value, the integration period is part of the electrical cycle, and the second optimization process quantity η is obtained n2 (n=a,b,c,d,e,f), the processing process is as follows:

[0064]

[0065] T v = k * T s (k≤1)

[0066] Where, T sis the electrical cycle value, T v is the integration period, and k is the ratio of the integration period to the electrical period. In this implementation, k is 1 / 12.

[0067] The third optimization stage is to n2 Perform threshold comparison: η n2 It is a value that does not change much over time and is relatively stable. In order to facilitate diagnosis, η n2 Perform threshold comparison processing to obtain the fault feature value FI n (n=a,b,c,d,e,f). This optimization uniformly marks the result of threshold comparison as two flags, 0 or 1. The result is concise and clear, and the diagnosis rules are simplified.

[0068] The processing process is as follows:

[0069]

[0070] Where ε is the set threshold. n The theoretical value of FI is 1. n If the accuracy is within a certain range, it is considered that a fault has occurred, so ε is numerically equal to FI n The present invention stipulates that the accuracy range is not less than 85%, that is, the value range of ε is 0.8-1. In this embodiment, the value of ε is 0.85.

[0071] The values ​​of δ, λ, k, and ε in step 2 are all related to the diagnostic effect and need to be reasonably selected. They are set to 1, 0.5, 1 / 12, and 0.85 respectively. The purpose of introducing δ is to prevent the numerator and denominator of the characteristic parameters of the corresponding phases from being 0 at the same time when two phases are 180° apart and open circuit, thereby affecting the diagnostic effect; the purpose of setting k is to shorten the diagnostic time.

[0072] Step 3: FI n The data is sent to the open circuit fault diagnosis and location processing module to determine whether the motor winding is faulty and the specific phase where the fault occurs. If no fault occurs, return to step 1 to continue monitoring.

[0073] The specific judgment basis is: determine the value of the fault characteristic quantity of each phase in turn. If the value is 1, it is considered that an open circuit fault has occurred in the phase winding; if it is 0, it is considered that no open circuit fault has occurred in the phase.

[0074] The specific diagnostic results of the embodiment of the six-phase permanent magnet synchronous motor winding open circuit fault diagnosis method based on harmonic sub-plane current of the present invention are shown in the following table, mainly including the winding health state, the single-phase winding open circuit state and the two-phase winding open circuit state. The two-phase winding open circuit state includes the two-phase fault winding open circuit states of 60°, 120° and 180° apart.

[0075] <![CDATA[FI a ]]> <![CDATA[FI b ]]> <![CDATA[FI c ]]> <![CDATA[FI d ]]> <![CDATA[FI e ]]> <![CDATA[FI f ]]> Diagnosis 0 0 0 0 0 0 healthy 1 0 0 0 0 0 A phase winding open circuit 0 1 0 0 0 0 B phase winding open circuit 0 0 1 0 0 0 C phase winding open circuit 0 0 0 1 0 0 D phase winding open circuit 0 0 0 0 1 0 E phase winding open circuit 0 0 0 0 0 1 F phase winding open circuit 1 0 0 0 1 0 A and E phase windings are open circuit 1 0 0 0 0 1 A, F two-phase winding open circuit 0 1 0 1 0 0 B and D phase windings are open circuit 0 1 0 0 0 1 B, F two-phase winding open circuit 0 0 1 1 0 0 C and D phase windings are open circuit 0 0 1 0 1 0 C and E phase windings are open circuit 1 1 0 0 0 0 A and B phase windings are open circuit 1 0 1 0 0 0 A and C phase windings are open circuit 0 1 1 0 0 0 B and C phase windings are open circuit 0 0 0 1 1 0 D and E phase windings are open circuit 0 0 0 1 0 1 D, F two-phase winding open circuit 0 0 0 0 1 1 E and F phase windings are open circuit 1 0 0 1 0 0 A and D phase windings are open circuit 0 1 0 0 1 0 B and E phase windings are open circuit 0 0 1 0 0 1 C and F phase windings are open circuit

[0076] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A method for diagnosing an open-circuit fault of a six-phase permanent magnet synchronous motor winding based on harmonic sub-plane current, wherein the winding structure of the motor is a six-phase winding symmetrically distributed and connected through a neutral point, characterized in that: The method comprises the following steps: Step 1: Information collection: The collected currents of each phase of the six-phase permanent magnet synchronous motor are filtered through a low-pass filter; then the filtered currents of each phase i a 、i b 、i c 、i d 、i e 、i f Perform vector transformation to obtain three mutually orthogonal sub-planes, among which the current corresponding to the fundamental wave sub-plane α-β is i α 、i β ; The current corresponding to the harmonic sub-plane z1-z2 is i z1 、i z2 ; The current corresponding to the zero-sequence space sub-plane o1-o2 is i o1 、i o2 ; Step 2: Calculation of fault characteristic quantities: First, the characteristic parameter η reflecting the health status of each phase winding is calculated based on the currents of the three sub-planes. n , n=a,b,c,d,e,f: Where δ is a positive real number and must satisfy the following formula: In the formula, I m is the phase current amplitude; Secondly, the characteristic parameter η n Perform filtering and output the filtered characteristic parameter η n1 ; Again, the characteristic parameter η after filtering n1 The average value η is obtained by integrating the following formula n2 : T v =k*T s (k≤1) Where, T s is the electrical cycle value, T v is the integration period, k is the ratio of the integration period to the entire electrical period; Finally, the fault characteristic quantity FI of each phase used to diagnose the winding open circuit fault is obtained. n : In the formula, ε is the set threshold, which is a positive number close to 0. The value range of the set threshold ε is 0.8-1; Step 3: Open circuit fault diagnosis and location processing: According to the fault feature FI obtained in step 2 n Determine whether an open circuit fault occurs in the nth phase, FI n =1 indicates an open circuit fault occurs in the nth phase, FI n =0 indicates that no open circuit fault occurs in the nth phase, and the process returns to step 1 to continue monitoring.

2. According to claim 1, the method for diagnosing an open-circuit fault of a six-phase permanent magnet synchronous motor winding based on harmonic sub-plane current is characterized in that: The current corresponding to the fundamental wave sub-plane α-β is i α 、i β , the current corresponding to the harmonic sub-plane z1-z2 is i z1 、i z2 , the current corresponding to the zero-sequence space sub-plane o1-o2 is i o1 、i o2 Obtained by the following transformation:

3. The method for diagnosing an open-circuit fault of a six-phase permanent magnet synchronous motor winding based on harmonic sub-plane current according to claim 1 is characterized in that: In step 2, the characteristic parameter η n Perform filtering and output the filtered characteristic parameter η n1 The process is: In the formula, 2λ is the filter bandwidth, and η n The peak pulse amplitude is limited to no more than η n 1.5 times the theoretical maximum value, which must satisfy: λ≤0.

5.

4. The method for diagnosing an open-circuit fault of a six-phase permanent magnet synchronous motor winding based on harmonic sub-plane current according to claim 1 is characterized in that: In step 2, δ, λ, k, and ε are associated and set to 1, 0.5, 1 / 12, and 0.85, respectively.

5. The method for diagnosing an open-circuit fault of a six-phase permanent magnet synchronous motor winding based on harmonic sub-plane current according to claim 1 is characterized in that: This method is applicable to diagnosing single-phase open circuit and two-phase open circuit faults of positive six-phase motors, a total of 21 faults. Among them, the two-phase open circuit fault includes two-phase windings open circuit at 60°, 120° and 180°.

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