Method for diagnosing faults in a motor stator winding based on the second harmonic component of the quadrature axis current

Abstract

Motor stator winding fault diagnosis method based on quadrature axis current second harmonic component belongs to the field of motor, and aims to solve the problems of slow fault diagnosis speed and low accuracy rate of partial conductor open circuit fault diagnosis of five-phase permanent magnet synchronous motor.The method comprises the following steps: step 1, collecting five-phase current signals of the motor, and separating the direct-axis and quadrature-axis currents of the fundamental wave space and the third harmonic wave space through Clark transformation and Park transformation; step 2, performing Fourier decomposition on the quadrature-axis current of the fundamental wave space to extract the second harmonic component, and performing Fourier decomposition on the five-phase current to obtain the fundamental wave component; step 3, calculating the change rate Δ of the second harmonic component, and determining the fault strand number according to the preset segmentation threshold; and step 4, positioning the fault phase through the amplitude drop of the five-phase current fundamental wave.

Description

TECHNICAL FIELD

[0001] The application relates to a motor stator winding fault diagnosis method based on a quadrature-axis current second harmonic component and belongs to the field of aerospace servo motors. BACKGROUND

[0002] At present, with the gradual development of rare earth permanent magnet materials, the overall performance of the permanent magnet synchronous motor is further improved, and the permanent magnet synchronous motor is widely applied. If the motor fails, it will affect the operation of the whole system. Therefore, the reliability of the motor system has attracted widespread attention. Compared with the traditional three-phase permanent magnet synchronous motor system, the multi-phase permanent magnet synchronous motor system not only inherits the advantages of high power density and high efficiency of the traditional three-phase permanent magnet synchronous motor system, but also has the characteristics of multiple control degrees of freedom, high reliability and strong fault tolerance, and is more suitable for occasions that require strong fault tolerance.

[0003] Due to space constraints, most motors are in a small working space, have high power density and poor heat dissipation conditions, which causes the motor to heat up too quickly and easily causes the motor stator winding to fail, affecting the normal operation of the motor system. Among the motor stator winding faults, the common fault types include open circuit fault, turn-to-turn short circuit fault and phase-to-phase short circuit fault. These faults may cause system shutdown and other problems, causing property loss, and in severe cases, even threaten personal safety. Therefore, it is particularly important to quickly and accurately diagnose the stator winding faults in the motor.

[0004] In the prior art, three-phase motor fault diagnosis methods are mostly based on current symmetrical component analysis or harmonic monitoring, but they cannot be directly applied to five-phase motors. SUMMARY

[0005] In order to solve the problems of slow fault diagnosis speed and low accuracy of the partial conductor open circuit fault of the five-phase permanent magnet synchronous motor, the application provides a motor stator winding fault diagnosis method based on a quadrature-axis current second harmonic component.

[0006] The motor stator winding fault diagnosis method based on the quadrature-axis current second harmonic component provided by the application is as follows:

[0007] Step 1, collect five-phase current signals of the motor, separate the direct-axis and quadrature-axis currents in the fundamental wave space and the third harmonic wave space through Clark transformation and Park transformation;

[0008] Step 2, perform Fourier decomposition on the quadrature-axis current in the fundamental wave space to extract the second harmonic component, and perform Fourier decomposition on the five-phase current to obtain the fundamental wave component;

[0009] Step 3, calculate the second harmonic component change rate Δ, and determine the fault strand number according to a preset segmentation threshold;

[0010] Step 4, locate the fault phase by the amplitude reduction of the fundamental component of the five-phase current.

[0011] Preferably, the process of step 1 comprises:

[0012] Step 11, collect the five-phase current of the five-phase permanent magnet synchronous motor , ;

[0013] Step 12, Clark transform and Park transform the five-phase current to separate the quadrature axis current in the fundamental space , the direct axis current in the fundamental space , the quadrature axis current in the third harmonic space and the direct axis current in the third harmonic space .

[0014] Preferably, the process of step 2 comprises:

[0015] Step 21, Fourier decomposition is performed on the five-phase current of the five-phase permanent magnet synchronous motor to extract the fundamental component of the five-phase current ;

[0016] Step 22, Fourier decomposition is performed on the quadrature axis current in the fundamental space to extract the second harmonic component of the quadrature axis current .

[0017] Preferably, the process of step 3 is:

[0018] Step 31, the change rate Δ of the second harmonic component is calculated according to the following formula:

[0019]

[0020] In the formula, is the second harmonic component of the quadrature axis current in the open circuit fault state, is the second harmonic component of the quadrature axis current in the healthy state;

[0021] Step 32, determine whether is true, if true, it indicates that the motor stator winding is healthy and there is no open circuit fault; otherwise, the motor stator winding has an open circuit fault, and step 33 is executed;

[0022] Step 33, determine the number of fault strands according to the segmented threshold of the change rate Δ of the second harmonic component:

[0023] 20%≤Δ<60%, the number of fault strands , is the number of strands of the motor whole-phase conductor, indicates rounding down;

[0024] 60%≤Δ<170%, number of faulty strands ;

[0025] 170%≤Δ<270%, number of faulty strands ;

[0026] 270%≤Δ<400%, number of faulty strands ;

[0027] 400%≤Δ<650%, number of faulty strands ;

[0028] 650%≤Δ<800%, number of faulty strands ;

[0029] 800%≤Δ<1550%, number of faulty strands .

[0030] Preferably, the fault phase identification criterion in step 4 is that the fundamental current amplitudes of the four healthy phases have no change before and after the fault, and the fundamental current amplitude of the fault phase decreases by more than 30%.

[0031] The present application has the beneficial effects that the present application provides a fault diagnosis strategy based on the second harmonic component of the quadrature-axis current for diagnosing partial conductor open circuit fault of a five-phase permanent magnet synchronous motor. The fault diagnosis strategy can quickly and accurately identify the fault phase and the number of faulty strands under different operating conditions of the motor. When the five-phase permanent magnet synchronous motor has a partial conductor open circuit fault, the hardware structure does not need to be changed, and after diagnosis by the diagnosis strategy, only the fault tolerant operation of the five-phase permanent magnet synchronous motor after the fault can be realized by using a fault tolerant control algorithm.

[0032] The second harmonic component of the quadrature-axis current is extracted by Clark transformation, Park transformation and Fourier decomposition, and the second harmonic component of the quadrature-axis current and the fundamental component of the five-phase current are used as fault features for diagnosing partial conductor open circuit fault of the five-phase permanent magnet synchronous motor. The change rate amplification technology and the segmented threshold logic are combined to realize quantitative identification of the number of faulty strands, and the difference in the fundamental current amplitude of the five-phase current is used to locate the fault phase. The fault diagnosis strategy of the present application can quickly and effectively distinguish the number of faulty strands and identify the fault phase under different torque and speed conditions.

[0033] The method has the characteristics of fast response, high precision and strong adaptability, and is suitable for industrial and aerospace fields with high reliability requirements. Specifically, the present application has the following outstanding performances:

[0034] Speed: through the amplification processing of the second harmonic component, the fault response time is shortened to milliseconds;

[0035] High precision: quantitative discrimination of fault strands is realized based on segmented threshold, and the accuracy is greater than or equal to 95%;

[0036] Strong adaptability: compatible with different rotating speed and torque conditions, suitable for high dynamic scenes such as aerospace servo system. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is the principle block diagram of the motor stator winding fault diagnosis method based on the quadrature axis current second harmonic component. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described 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. 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.

[0039] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0040] The present application will be further described below in combination with the drawings and specific embodiments, but not as a limitation of the present application.

[0041] Specific implementation method one: the present embodiment will be described below Figure 1 The motor stator winding fault diagnosis method based on the quadrature axis current second harmonic component is described in the present embodiment. Under the given torque command and speed command, the fault diagnosis strategy based on the quadrature axis current second harmonic component is used to obtain the fault characteristics from the five-phase current, and the partial conductor open circuit fault diagnosis of the five-phase permanent magnet synchronous motor is completed.

[0042] The fault diagnosis strategy based on the quadrature axis current second harmonic component includes a fault feature acquisition step and a fault discrimination step,

[0043] The fault feature acquisition step acquires the five-phase current of the motor, acquires the quadrature axis current of the five-phase permanent magnet synchronous motor fundamental space through Park transformation and Clark transformation, performs Fourier decomposition on the acquired five-phase current and quadrature axis current, obtains the five-phase current fundamental component and the quadrature axis current second harmonic component, and takes the two as fault characteristics.

[0044] The fault discrimination step uses the five-phase current fundamental component to discriminate the fault phase of the motor, and uses the quadrature axis current second harmonic component to discriminate the open circuit fault strand number of the motor.

[0045] The specific steps of the method of the present application include:

[0046] Step 1, collect the five-phase current signals of the motor, separate the direct-axis and quadrature-axis currents in the fundamental wave space and the third harmonic wave space through Clark transformation and Park transformation;

[0047] Step 2, Fourier decompose the quadrature-axis current in the fundamental wave space to extract the second harmonic component, and Fourier decompose the five-phase current to obtain the fundamental wave component;

[0048] Step 3, calculate the change rate Δ of the second harmonic component, and determine the number of fault strands according to the preset segmentation threshold;

[0049] Step 4, locate the fault phase through the amplitude drop of the fundamental wave amplitude of the five-phase current.

[0050] Among them, the fault feature acquisition step includes step 1 and step 2:

[0051] Step 1 includes:

[0052] Step 11, collect the five-phase current of the five-phase permanent magnet synchronous motor , ;

[0053] Step 12, perform Clark transformation and Park transformation on the five-phase current to separate the quadrature-axis current in the fundamental wave space, the direct-axis current in the fundamental wave space, the quadrature-axis current in the third harmonic wave space, and the direct-axis current in the third harmonic wave space.

[0054] Step 2 includes:

[0055] Step 21, Fourier decompose the five-phase current of the five-phase permanent magnet synchronous motor to extract the fundamental wave component of the five-phase current ;

[0056] Step 22, Fourier decompose the quadrature-axis current in the fundamental wave space to extract the second harmonic component of the quadrature-axis current .

[0057] The fundamental wave component of the five-phase current and the second harmonic component of the quadrature-axis current are taken as fault features.

[0058] Among them, the fault discrimination step includes step 3 and step 4:

[0059] The process of step 3 is:

[0060] Step 31, the change rate Δ of the second harmonic component is calculated as follows:

[0061]

[0062] In the formula, is the second harmonic component of the quadrature axis current in the open circuit fault state, is the second harmonic component of the quadrature axis current in the healthy state;

[0063] In the healthy state of the motor, the value of the second harmonic component of the quadrature axis current is close to 0A, and when a partial conductor open circuit fault occurs, the value of the second harmonic component of the quadrature axis current increases with the increase of the fault strand number, and when it rises to a certain degree and stabilizes, the fault strand number of the fault can be distinguished, and the change degree of the fault feature is prevented from being too small when the fault strand number increases, which is difficult to distinguish. The change rate of the fault feature of the fault diagnosis strategy used in the present application increases obviously with the increase of the fault strand number, which can effectively distinguish the fault strand number. In this step, Δ is calculated, and the amplification processing of the second harmonic component of the quadrature axis current is performed, so that the accuracy and sensitivity of fault discrimination are greatly improved.

[0064] Step 32, judging whether it is true, if it is true, it indicates that the motor stator winding is healthy and has no open circuit fault; otherwise, the motor stator winding has an open circuit fault, and step 33 is performed;

[0065] Step 33, judging the fault strand number according to the segmented threshold of the second harmonic component change rate Δ:

[0066] 20%≤Δ<60%, the fault strand number , is the number of the whole phase conductor of the motor, indicates the floor function;

[0067] 60%≤Δ<170%, the fault strand number ;

[0068] 170%≤Δ<270%, the fault strand number ;

[0069] 270%≤Δ<400%, the fault strand number ;

[0070] 400%≤Δ<650%, the fault strand number ;

[0071] 650%≤Δ<800%, the fault strand number ;

[0072] 800%≤Δ<1550%, the fault strand number .

[0073] When it is judged that there is an open circuit fault, step 4 is performed to judge what the fault phase is, if the detection result is healthy, step 4 does not need to be performed again, the logic algorithm is simplified, and the operation efficiency is improved.

[0074] The fault phase judgment standard in step 4 is that the current fundamental wave amplitudes of the four healthy phases have no change before and after the fault, and the current fundamental wave amplitude of the fault phase is reduced by more than 30%.

[0075] Under the healthy state of the motor, the five-phase current fundamental wave components are similar, and after the partial conductor open circuit fault occurs, the current fundamental wave component of the fault phase is more severely reduced than the remaining four phases.

[0076] Figure 1 For the example of applying the strategy of the application to a surface-mounted motor, for the given torque of the motor, for the fundamental wave space direct axis current calculated by the control strategy of = 0, for the fundamental wave space cross axis current calculated by the control strategy of = 0, for the third harmonic wave space direct axis current calculated by the control strategy of = 0, for the third harmonic wave space cross axis current calculated by the control strategy of = 0. for the fundamental wave space direct axis current, for the fundamental wave space cross axis current, for the third harmonic wave space direct axis current, for the third harmonic wave space cross axis current. for the fundamental wave space direct axis current fed back by the feedback link, for the fundamental wave space cross axis current fed back by the feedback link, for the third harmonic wave space direct axis current fed back by the feedback link, for the third harmonic wave space cross axis current fed back by the feedback link. for the fundamental wave space direct axis voltage calculated by the PI link, for the fundamental wave space cross axis voltage calculated by the PI link, for the third harmonic wave space direct axis voltage calculated by the PI link, for the third harmonic wave space cross axis voltage calculated by the PI link. for the fundamental wave space axis voltage after the Clark link, for the fundamental wave space axis voltage after the Clark link, for the third harmonic wave space axis voltage after the Clark link, For the third harmonic space after the Clark stage Shaft voltage.

[0077] use =0 control strategy. This control strategy is based on a given electromagnetic torque. Afterwards, =0 control strategy, through PI, to obtain the d-axis and quadrature-axis voltages of the fundamental and third harmonic spaces, and then through Clark transformation to obtain the fundamental and third harmonic spaces. , The shaft voltage is then fed into the motor via Park transform, SVPWM stage, and inverter. Five-phase current is obtained from the motor, and fed back to the front end through Park inverse transform and Clark inverse transform to complete closed-loop control. Based on this, the quadrature-axis current and five-phase current in the motor's fundamental frequency space are obtained, and Fourier decomposition is performed to obtain fault characteristics, perform fault identification, and complete the diagnosis of open circuit faults in some conductors of the motor.

[0078] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method for diagnosing a fault in a stator winding of an electrical machine based on a quadrature-axis current second harmonic component, characterized in that, The method is: Step 1, collect the five-phase current signal of the motor, separate the direct-axis and quadrature-axis currents of the fundamental wave space and the third harmonic wave space through Clark transformation and Park transformation; Step 2, Fourier decomposition is performed on the quadrature-axis current of the fundamental wave space to extract the second harmonic component, and Fourier decomposition is performed on the five-phase current to obtain the fundamental wave component; Step 3, calculate the change rate Δ of the second harmonic component, and determine the number of fault strands according to the preset segmentation threshold; the process is: Step 31, the change rate Δ of the second harmonic component is calculated according to the following formula: wherein is the second harmonic component of the quadrature axis current in open circuit fault condition, is the second harmonic component of the quadrature axis current in healthy condition; Step 32, judging whether it is true, if true, indicating that the motor stator winding is healthy and no open circuit fault; otherwise, the motor stator winding has an open circuit fault, and step 33 is executed; Step 33, the number of fault strands is determined according to the segmentation threshold of the change rate Δ of the second harmonic component: 20% < Δ < 60%, number of faulty strands , is the number of motor phase conductors, denotes the floor function; 60% < Δ < 170%, number of broken strands ; 170% < Δ < 270%, number of failed strands ; 270% < Δ < 400%, number of failed strands ; 400% < Δ < 650%, number of broken strands ; 650% < Δ < 800%, number of faulty strands ; 800% < Δ < 1550%, number of broken strands ; Step 4, locate the fault phase through the amplitude reduction of the fundamental wave of the five-phase current, and the fault phase determination standard is that the current fundamental wave amplitude of the four healthy phases has no change before and after the fault, and the current fundamental wave amplitude of the fault phase is reduced by more than 30%.

2. The method for diagnosing a fault of a stator winding of an electric machine based on a quadrature-axis current second harmonic component according to claim 1, characterized by, The process of step 1 includes: Step 11, acquiring five-phase currents of the five-phase permanent magnet synchronous motor , ; Step 12, Clark and Park transformation of the five-phase currents to separate the fundamental space quadrature axis current , the fundamental space direct axis current , the third harmonic space quadrature axis current and the third harmonic space direct axis current .

3. The method for diagnosing a fault of a stator winding of an electric machine based on a quadrature-axis current second harmonic component according to claim 2, characterized by, The process of step 2 includes: Step 21, Fourier decomposition of the five-phase current of the five-phase permanent magnet synchronous motor extracting the fundamental component of the five-phase current ; Step 22, quadrature axis current of the fundamental space Performing Fourier decomposition to extract the quadrature axis current second harmonic component .

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