A high-frequency common-mode voltage-based inter-turn fault diagnosis method for permanent magnet synchronous motor

Abstract

The application discloses a turn-to-turn fault diagnosis method for a permanent magnet synchronous motor based on a high-frequency common-mode voltage and belongs to the technical field of motor control. The turn-to-turn fault diagnosis method for the permanent magnet synchronous motor based on the high-frequency common-mode voltage comprises the following steps: injecting a three-phase symmetrical high-frequency voltage into a control system; collecting three-phase currents and calculating dq-axis voltages according to a voltage formula of the permanent magnet synchronous motor; converting the dq-axis voltages into three-phase voltages through inverse Park transformation; calculating the three-phase bridge arm midpoint voltage of an inverter to the ground through a driving signal of a power tube and obtaining three-phase common-mode voltages by combining the three-phase voltages; extracting high-frequency components at an injection frequency in the three-phase common-mode voltages and judging the turn-to-turn fault according to the standard deviation of the three-phase high-frequency common-mode voltages; the motor turn-to-turn fault diagnosis is realized through the method of the high-frequency common-mode voltage without adding a voltage sensor, and the fault characteristics of the high-frequency voltage are more prominent compared with a high-frequency current fault diagnosis method.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of motor control, and particularly relates to a turn-to-turn fault diagnosis method for a permanent magnet synchronous motor based on a high-frequency common-mode voltage. BACKGROUND

[0002] High temperature, high voltage current stress, corrosion and other reasons may cause the insulation of the motor stator winding to be damaged, which is easy to cause a turn-to-turn short circuit fault of the motor stator winding. The permanent magnet synchronous motor uses a permanent magnet as an excitation source, and once a turn-to-turn short circuit fault occurs, a large short circuit current will be caused, which further damages the insulation of the stator winding. In addition, the excessive short circuit current will cause local high temperature, which may cause demagnetization failure of the permanent magnet. In order to improve the reliability of the permanent magnet synchronous motor driving system, online detection of the fault during operation of the motor is required to prevent further deterioration of the fault.

[0003] At present, the diagnosis methods for turn-to-turn short circuit faults of permanent magnet synchronous motors can be mainly divided into low-frequency-based fault detection methods and high-frequency-based fault detection methods. The low-frequency-based fault diagnosis method generally realizes turn-to-turn fault diagnosis by observing the voltage and current at the fundamental frequency of the motor. This method is relatively simple, but the fault characteristics are not obvious when the motor is at low speed and light load, and it is difficult to judge the fault. The high-frequency-based fault detection method generally injects a high-frequency voltage into the system, and realizes turn-to-turn fault detection by observing the high-frequency component in the current; but the high-frequency current signal is relatively weak, and the fault characteristics are still not ideal. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a turn-to-turn fault diagnosis method for a permanent magnet synchronous motor based on a high-frequency common-mode voltage, which solves the technical problems in the prior art.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] A turn-to-turn fault diagnosis method for a permanent magnet synchronous motor based on a high-frequency common-mode voltage, comprising the following steps:

[0007] injecting a three-phase symmetrical high-frequency voltage into the control system;

[0008] collecting three-phase currents and calculating dq-axis voltages according to the voltage formula of the permanent magnet synchronous motor;

[0009] converting the dq-axis voltages into three-phase voltages through inverse Park transformation;

[0010] calculating the three-phase common-mode voltage by combining the three-phase voltages with the three-phase common-mode voltage calculated by using the drive signal of the power tube and the three-phase common-mode voltage calculated by using the drive signal of the power tube;

[0011] The high-frequency component at the injected frequency in the three-phase common-mode voltage is extracted, and the turn-to-turn fault is judged according to the standard deviation of the three-phase high-frequency common-mode voltage amplitude.

[0012] Further, the calculation formula of the high-frequency voltage is:

[0013]

[0014] Wherein, u ah , u bh , u ch are the injected three-phase high-frequency voltage, u h is the amplitude of the injected high-frequency voltage, θ h is the phase angle of the injected high-frequency voltage.

[0015] Further, the calculation formula of the dq-axis voltage is:

[0016]

[0017] Wherein, u d , u q are the dq-axis voltage, R s is the phase resistance, i d , i q are the dq-axis current, L d , L q are the dq-axis inductance, w e is the angular velocity of the motor, λ m is the permanent magnet flux linkage.

[0018] Further, the conversion expression of the dq-axis voltage converted to the three-phase coordinate system is:

[0019]

[0020] Wherein, θ e is the electrical angle of the motor, u a , u b , u c are the three-phase voltage.

[0021] Further, the calculation formula of the midpoint voltage of the three-phase bridge arm of the inverter to ground is:

[0022]

[0023] Wherein, u ag , u bg , u cg are the midpoint voltage of the three-phase bridge arm of the inverter to ground, s1, s3, s5 are the driving signals of the three power tubes of the upper bridge arm of the inverter, u dc is the bus voltage.

[0024] Further, when the motor is in normal operation, the three-phase common-mode voltage can be expressed as:

[0025]

[0026] wherein, is the three-phase common-mode voltage.

[0027] Further, when the motor is in inter-turn short-circuit state, the three-phase common-mode voltage can be expressed as:

[0028]

[0029] wherein, R is the phase resistance, L a , L b , L c are the three-phase self-inductance, M ab , M ac are the AB-phase and AC-phase mutual inductance, μ is the ratio of short-circuit turns to total turns, i f is the short-circuit current, and L σ is the leakage inductance.

[0030] Further, the extraction process of the high-frequency component is: comparing the common-mode voltage equations before and after the fault, and ignoring the effect of resistance at high frequency, the above equation can be written as:

[0031]

[0032] wherein, are the high-frequency components of the three-phase common-mode voltage at the injection frequency, respectively.

[0033] Further, the judgment process of the inter-turn fault is: the inter-turn fault is judged by the standard deviation of the three-phase common-mode voltage, and the specific steps are:

[0034] The average value of the three-phase common-mode voltage can be expressed as:

[0035]

[0036] Define the fault diagnosis variable FI as:

[0037]

[0038] When the fault diagnosis variable is less than the threshold value, it is judged that the motor is in normal operation; when the fault diagnosis variable is greater than the threshold value, it is judged that the motor has an inter-turn fault.

[0039] A permanent magnet synchronous motor inter-turn fault diagnosis system based on high-frequency common-mode voltage, comprising:

[0040] a voltage input module: injecting three-phase symmetrical high-frequency voltage into the control system;

[0041] dq axis voltage calculation module: collect three-phase current, and calculate dq axis voltage according to the voltage formula of permanent magnet synchronous motor;

[0042] Three-phase voltage conversion module: convert dq axis voltage into three-phase voltage through inverse Park transformation;

[0043] Common-mode voltage calculation module: calculate the voltage of the three-phase bridge arm midpoint of the inverter to the ground by using the driving signal of the power tube, and calculate the three-phase common-mode voltage by combining the three-phase voltage;

[0044] Fault judgment module: extract the high-frequency component at the injection frequency in the three-phase common-mode voltage, and judge the inter-turn fault according to the standard deviation of the three-phase high-frequency common-mode voltage.

[0045] The beneficial effects of the present application are:

[0046] 1. Without adding voltage sensors, the motor inter-turn fault diagnosis is realized by the method of high-frequency common-mode voltage.

[0047] 2. Compared with the fault diagnosis method of high-frequency current, the fault characteristics of high-frequency voltage are more prominent. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0049] Figure 1 is the flow chart of the fault diagnosis method of the present application;

[0050] Figure 2 is the schematic diagram of the cross section of the permanent magnet synchronous motor of the present application;

[0051] Figure 3 is the circuit diagram of the three-phase inverter of the present application;

[0052] Figure 4 is the control block diagram of the permanent magnet synchronous motor under high-frequency voltage injection of the present application. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0054] The permanent magnet synchronous motor to which the present application is directed has a cross-sectional view as shown in Figure 2 The three-phase inverter circuit is as shown in Figure 3 The control block diagram of the permanent magnet synchronous motor under high-frequency voltage injection is as shown in Figure 4

[0055] As shown in Figure 1 and Figure 4 A permanent magnet synchronous motor inter-turn fault diagnosis method based on high-frequency common-mode voltage includes the following steps:

[0056] S1, injecting a three-phase symmetrical high-frequency voltage into the motor control system, as shown in the following formula:

[0057]

[0058] Wherein, u ah , u bh , u ch are the injected three-phase high-frequency voltage, u h is the amplitude of the injected high-frequency voltage, θ h is the phase angle of the injected high-frequency voltage.

[0059] S2, collecting the three-phase currents i a , i b , i c of the motor stator winding, and calculating the dq-axis voltages u d , u q according to the voltage formula of the permanent magnet synchronous motor;

[0060]

[0061] Wherein, u d , u q are the dq-axis voltages, R s is the phase resistance, i d , i q are the dq-axis currents, L d , L q are the dq-axis inductances, w e is the angular velocity of the motor, and λ m is the permanent magnet flux linkage.

[0062] S3, converting the dq-axis voltages u d , u q to the three-phase coordinate system u an , u bn , u cn through inverse Park transformation; the conversion expression is:

[0063] ​

[0064] Where, θ e Let u be the electrical angle of the motor. an u bn u cn These are the three-phase voltages.

[0065] S4, such as Figure 3 As shown, the voltage u at the midpoint of the three-phase bridge arm of the inverter is calculated using the drive signal of the power transistor. ag u bg u cg And through the three-phase voltage u an u bn u cn The difference is used to calculate the three-phase common-mode voltage.

[0066] The specific steps include:

[0067] S41 calculates the inverter's three-phase bridge arm midpoint-to-ground voltage u using the three-phase voltage and the power transistor's drive signal. ag u bg u cg The calculation formula is:

[0068]

[0069] Where s1, s3, and s5 are the drive signals for the three power transistors on the upper arm of the inverter, respectively. dc This refers to the bus voltage.

[0070] S42, based on the inverter three-phase bridge arm midpoint to ground voltage u ag u bg u cg The three-phase common-mode voltage was calculated.

[0071] The formula for calculating the three-phase common-mode voltage is:

[0072]

[0073] Because the inverter circuit has the following relationship:

[0074]

[0075] When the motor is running normally, the following exists:

[0076] u an +u bn +u cn =0

[0077] We can obtain:

[0078]

[0079] Therefore, the common-mode voltage can be expressed as:

[0080]

[0081] When the motor is running normally, since the three-phase high-frequency voltage has equal amplitude and a phase difference of 120°, the high-frequency component at the injection frequency is cancelled out, so there is no high-frequency component at the injection frequency in the common-mode voltage.

[0082] When the motor is in an inter-turn short-circuit state, the three-phase voltage equation becomes:

[0083]

[0084] where R is the phase resistance, L a , L b , L c are the three-phase self-inductances, M ab , M ac , M bc are the mutual inductances of the AB, AC, and BC phases, e a , e b , e c are the three-phase counter-electromotive forces, μ is the ratio of the number of short-circuit turns to the total number of turns, and i f is the short-circuit current.

[0085] At this time, the sum of the three-phase voltages can be expressed as:

[0086]

[0087] where L σ is the leakage inductance.

[0088] It can be obtained that:

[0089]

[0090] Therefore, the common-mode voltage under the inter-turn fault condition can be expressed as:

[0091]

[0092] S5, extracts the high-frequency component at the injection frequency in the three-phase common-mode voltage and judges the inter-turn fault according to the amplitude difference of the three-phase high-frequency common-mode voltage;

[0093] where the extraction process of the high-frequency component is as follows: compare the common-mode voltage equations before and after the fault, and consider that the resistance can be ignored at high frequencies, so the above equation can be written as: ​

[0094]

[0095] It can be seen that when the motor occurs inter-turn short circuit fault, high frequency components at the injection frequency appear in the common-mode voltage and the three-phase high frequency common-mode voltage amplitudes are not equal; therefore, the inter-turn short circuit fault of the permanent magnet synchronous motor can be diagnosed according to the amplitude difference of the three-phase high frequency common-mode voltage;

[0096] The judgment process is that the inter-turn fault is judged by the standard deviation of the three-phase common-mode voltage:

[0097] The average value of the three-phase common-mode voltage It can be expressed as:

[0098]

[0099] The fault diagnosis variable FI is defined as:

[0100]

[0101] When the fault diagnosis variable is less than the threshold value, it is judged that the motor is in a normal operating state; when the fault diagnosis variable is greater than the threshold value, it is judged that the motor occurs inter-turn fault.

[0102] When the permanent magnet synchronous motor is in normal operation, due to the symmetry of the three-phase winding, the injection of high frequency signal will not cause high frequency components to appear in the common-mode voltage; when the permanent magnet synchronous motor occurs inter-turn short circuit fault, the three-phase winding is no longer symmetrical, and after the injection of high frequency signal, high frequency components will appear in the common-mode voltage. Therefore, the inter-turn fault of the permanent magnet synchronous motor can be quickly diagnosed by observing the high frequency components in the common-mode voltage. The fault diagnosis method only needs to calculate the high frequency components in the common-mode voltage in real time, without the need of additional hardware devices.

[0103] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0104] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A high-frequency common-mode voltage-based inter-turn fault diagnosis method for a permanent magnet synchronous motor, characterized in that, The method comprises the following steps: injecting a three-phase symmetrical high-frequency voltage into a control system; The three-phase currents are collected and calculated according to the voltage formula of the permanent magnet synchronous motor Shaft voltage; by an inverse Park transformation axis voltage into a three-phase voltage; calculating the three-phase bridge arm midpoint-to-ground voltage of the inverter by using the driving signal of the power tube, and calculating the three-phase common-mode voltage by combining the three-phase voltage; extracting a high-frequency component at the injection frequency in the three-phase common-mode voltage, and judging the inter-turn fault according to the standard deviation of the three-phase high-frequency common-mode voltage amplitude; the calculation formula of the three-phase bridge arm midpoint-to-ground voltage of the inverter is: wherein, , , , , are the driving signals of the three power tubes of the upper bridge arm of the inverter, respectively, is the bus voltage; when the motor is in normal operation, the three-phase common-mode voltage can be represented as: wherein , , is a three-phase common-mode voltage; when the motor is in an inter-turn short circuit state, the three-phase common-mode voltage can be represented as: wherein, is the phase resistance, , , are the three-phase self-inductances, , are the AB and AC mutual inductances, is the ratio of short-circuit turns to total turns, is the short-circuit current, is the leakage inductance; the extraction process of the high-frequency component is: comparing the common-mode voltage equations before and after the fault, and ignoring the effect of the resistance at high frequency, the above formula can be written as: wherein , , are the high frequency components at the injected frequency in the three-phase common-mode voltage, respectively. the judgment process of the inter-turn fault is: the inter-turn fault is judged by the standard deviation of the three-phase common-mode voltage, and the specific steps are: Average value of three-phase common-mode voltage may be expressed as: define the fault diagnosis variable FI as: when the fault diagnosis variable is less than the threshold value, it is judged that the motor is in a normal operation state; when the fault diagnosis variable is greater than the threshold value, it is judged that the motor has an inter-turn fault.

2. The method according to claim 1, wherein the calculation formula of the high-frequency voltage is: wherein, , , are the injected three-phase high-frequency voltages, is the amplitude of the injected high-frequency voltage, is the phase angle of the injected high-frequency voltage.

3. The method according to claim 1, wherein The The formula for calculating the shaft voltage is: wherein , are respectively shaft voltages, is a phase resistance, , are respectively shaft currents, , are respectively shaft inductances, is an angular speed of the electric machine, is a permanent magnet flux linkage.

4. The method according to claim 1, wherein The The conversion expression of the shaft voltage into the three-phase coordinate system is: wherein is the electrical angle of the motor, , , are the three phase voltages, respectively.

5. A high-frequency common-mode voltage based inter-turn fault diagnosis system for permanent magnet synchronous machines, performing the method of any one of claims 1-4, characterized in that, comprise: a voltage input module: injecting a three-phase symmetrical high-frequency voltage into a control system; Shaft voltage calculation module: collect three-phase current, and calculate according to the voltage formula of permanent magnet synchronous motor Shaft voltage; Three-phase voltage conversion module: converting the shaft voltage into a three-phase voltage by inverse Park transformation three-phase voltage a common-mode voltage calculation module: calculating the three-phase bridge arm midpoint-to-ground voltage of the inverter by using the driving signal of the power tube, and calculating the three-phase common-mode voltage by combining the three-phase voltage; a fault judgment module: extracting a high-frequency component at the injection frequency in the three-phase common-mode voltage, and judging the inter-turn fault according to the standard deviation of the three-phase high-frequency common-mode voltage.

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