CN110988471B - Wind driven generator variable pitch drive belt fault diagnosis method based on current signals - Google Patents
Wind driven generator variable pitch drive belt fault diagnosis method based on current signals Download PDFInfo
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Abstract
The invention relates to a wind driven generator variable pitch drive belt fault diagnosis method based on current signals, which comprises the following steps of: acquiring a current signal of a driving shaft motor stator of a variable pitch belt transmission system; preprocessing the motor stator current signal to enable the motor stator current signal to meet the requirements of a monitoring system; obtaining a frequency spectrum diagram of the preprocessed motor stator current signal by using a data analysis method; and if the fault side frequency peak occurs in the set range of the fundamental frequency in the frequency spectrum, determining that the belt of the variable pitch belt transmission system has a fault. Slip faults caused by belt aging can be identified using the method of the present invention without adding sensors.
Description
Technical Field
The invention relates to the technical field of fault diagnosis, in particular to a fault diagnosis method for a variable pitch drive belt of a wind driven generator based on current signals.
Background
In recent years, the problem of global warming has been increasingly emphasized. Clean energy is a core issue for meeting global climate change and realizing sustainable energy supply. Wind power generation is an important clean energy source. Wind power generators have been rapidly developed for decades, especially in recent years, the key point of wind power construction is changed from land to sea, the grid-connected scale of wind power is larger and larger, and the single-machine capacity and the size of blades of a fan are increased day by day. The wind generating set is rapidly developed after decades, the life cycle of the wind generating set is generally 20 to 30 years, part of units of the existing wind field enter the middle and later stages of operation and maintenance, and the early-stage fan technology is relatively immature, so that the failure rate of the wind generating set is high in recent years, the operation and maintenance cost is increased due to failure, new energy power generation represented by wind power generation is difficult to compete with the traditional fossil energy power generation, and the safe and stable operation of the whole power grid can be threatened even by large-scale fan failure and grid disconnection accidents.
In order to capture wind energy as much as possible, realize braking and pitch retracting under emergency conditions and ensure the safety of a wind driven generator, the existing wind generating set is provided with a pitch control system. The variable pitch system is a blade angle adjusting device of the wind driven generator, when the wind power is large, the pitch angle is increased through the variable pitch system, and the wind energy absorbed by the blades is reduced; when wind power is small, the pitch angle is reduced through the variable pitch system, so that the wind energy obtained by the blades is increased, and the power of the wind driven generator is maintained to operate near the rated power. The variable pitch system of the fan comprises a variable pitch motor, a variable pitch bearing, a transmission belt and the like, the variable pitch transmission system is a component with high damage probability in the variable pitch system, blades of the variable pitch system need to be disassembled in the maintenance process, so that the maintenance cost is high, how to timely know the working condition of the variable pitch system, and the problem of solving faults in an early stage is the core problem of state monitoring and fault diagnosis of the variable pitch system of the wind driven generator.
Fig. 1 shows a transmission belt fault diagnosis device based on an electrostatic sensor. Wherein 11 is an intelligent electrostatic sensor, 12 is a belt, 13 is a transmission belt pulley, and 14 is an idler pulley. The static sensor 11 is used for collecting position signals of the transmission belt 12 in the vertical direction, the change of the fine position of the belt 12 in the vertical direction can also generate an induction phenomenon in a classical field of the static sensor 11, a built-in circuit in the static sensor 11 is converted into an electric signal to obtain the output of a voltage signal, and the position change corresponding to the voltage change can be obtained by calculating corresponding parameters.
Fig. 2 is a graph showing the results of experiments performed by the apparatus shown in fig. 1, i.e., a positional deviation at different rotational speeds, with the abscissa representing the reference speed and the ordinate representing the amplitude.
For the common fault detection technology of the wind power generation system, the current research at home and abroad mainly focuses on the fault detection technology based on the mechanical vibration signal. The vibration signal needs to be provided with an additional vibration signal sensor, needs to be connected with a collecting system through a connecting wire, is not suitable for a hub engine room of a wind driven generator which rotates at any time, and therefore cannot be used in a variable pitch system of the wind driven generator.
The prior technical scheme has the following technical defects: a fault diagnosis method for a variable-pitch transmission belt of a wind driven generator is not available; the existing fault diagnosis method for the transmission belt mainly depends on an additional position signal sensor, so that the operation and maintenance cost of a wind power plant is increased; the data-driven fault diagnosis method is difficult to reasonably explain in principle, and different results can be obtained by replacing different data sets.
Disclosure of Invention
In order to solve the problems, the invention provides a fault diagnosis method for a variable-pitch transmission belt of a wind driven generator based on a current signal, and the fault diagnosis method based on the current signal realizes the establishment of a transmission belt health management system which is non-invasive and does not need to adopt an additional sensor.
The invention is realized by the following technical scheme:
the invention provides a wind driven generator variable pitch drive belt fault diagnosis method based on current signals, which comprises the following steps:
acquiring a current signal of a driving shaft motor stator of a variable pitch belt transmission system;
preprocessing the motor stator current signal;
obtaining a frequency spectrum diagram of the preprocessed motor stator current signal by using a data analysis method;
and if the fault side frequency peak appears in the set range of the distance fundamental frequency in the frequency spectrum, the belt of the variable pitch belt transmission system is judged to have a fault.
Further, a motor stator current signal is led out by a control system of a variable pitch belt transmission system.
Further, the preprocessing comprises filtering the ultrahigh frequency harmonic by using a filter and normalizing the acquired data.
Further, the data analysis method in step (3) includes fast fourier transform or wavelet transform.
Further, the fault side frequency peak appears within several Hz from the fundamental frequency.
Further, the fault side frequency peak appears at f1±feNear frequency; f. of1Is the fundamental frequency, f, of the motor stator current signaleIs the fault signature frequency.
Further, the fault characteristic frequency is calculated by the following formula:
wherein f iseFor the fault characteristic frequency, Δ T is the torque of the difference between the static friction and the sliding friction, JzTo translate to the equivalent moment of inertia at the rotor output of the motor.
Furthermore, the fault characteristic frequency changes along with the change of the fundamental frequency and always appears on two sides of the fundamental frequency.
Further, the failure of the belt is a periodic slip.
Further, the method also comprises the steps of early warning and overhauling after the belt breaks down.
Compared with the prior art, the invention has the following advantages:
(1) the invention provides a fault diagnosis method for a variable-pitch transmission belt of a wind driven generator based on current signals, provides a brand-new transition working condition in a belt aging process, realizes non-invasive online monitoring of a variable-pitch system of the wind driven generator, analyzes the expression form of the periodic slipping transition working condition of the transmission belt in the current signals, gives fault characteristic frequency, estimates the fault characteristic frequency under different working conditions, masters the running state of the variable-pitch system in real time, reduces the fault occurrence rate, and realizes intelligent sensing and intelligent operation and maintenance of a wind power plant.
(2) Because the current signal can be directly obtained from the control system, the method does not need to install an additional sensor like a vibration signal, the sensorless wind driven generator fault diagnosis is realized, the space in the hub of the wind driven generator is saved, the cost is reduced, and the risk of failure of the sensor is avoided.
(3) The invention can find the fault in time and process the fault in advance when the transmission belt periodically slips in the transient working condition.
Drawings
FIG. 1 is a diagram of a prior art electrostatic sensor based drive belt fault diagnostic device;
FIG. 2 is a graph of the position deviation of the device of FIG. 1 at various rotational speeds;
FIG. 3 is a schematic view of a variable pitch drive belt of the wind turbine;
FIG. 4(a) is a diagram showing the relationship between the forces of the driving belt, the driving shaft and the driven shaft under normal operating conditions;
FIG. 4(b) is a graph showing an analysis of the relationship of forces between the driving belt, the driving shaft and the driven shaft under complete slip;
FIG. 4(c) is a graph showing the relationship between the forces of the driving belt, the driving shaft and the driven shaft under the condition of the periodic slip;
FIG. 4(d) is a graph of speed information for a periodic slip condition;
FIG. 5 is a graph of remaining useful life of a variable pitch drive belt of a wind turbine;
FIG. 6(a) is a normal motor stator current signal diagram, FIG. 6(b) is a belt periodic fault modulation current signal diagram, and FIG. 6(c) is a fault modulated motor stator current diagram;
FIG. 7(a) is the current waveform of the stator of the belt-driven motor under normal operating conditions;
FIG. 7(b) is a motor stator current waveform for a fully slipping down belt drive;
FIG. 7(c) is a waveform of motor stator current for a periodic slipping under-belt drive;
FIG. 8 is a frequency spectrum of a motor stator current for a belt drive;
FIG. 9 is a driven wheel torsional vibration signal under a belt periodic slip fault;
FIG. 10 is a frequency spectrum analysis of a driven wheel frequency-converted signal under a periodic belt slip fault;
FIG. 11 is a schematic illustration of a moment of inertia calculation;
FIG. 12 is a graph of drive belt failure signature frequencies for different fundamental frequencies;
FIG. 13 is a diagram showing the relationship between fundamental frequency and fault signature frequency;
FIG. 14 is a flow chart for fault diagnosis based on spectral analysis of a current signal.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
Characteristic analysis of variable-pitch transmission belt of wind driven generator
Fig. 3 is a physical diagram of a pitch drive belt of a wind turbine generator, and firstly, a periodic slip transition working condition which can be used for fault diagnosis of the pitch drive belt of the wind turbine generator is provided. In the belt transmission, the friction force plays a role in transmitting force between the two rolling wheels, so that the driving wheel drags the driven wheel to rotate. The friction force can be calculated by equation (1):
fmassage device＝μF (1)
From the formula (1), the friction force fMassage deviceThe magnitude of (d) depends on two variables, the coefficient of friction mu and the surface tension F. The coefficient of friction refers to the ratio between the friction between contacting surfaces and the perpendicular force on the surfaces. The contact surface can be divided into a dynamic friction coefficient and a static friction coefficient according to whether the contact surface is displaced relatively. In general, the static friction coefficient is slightly larger than the dynamic friction coefficient, the static friction force refers to the acting force between two objects which are in contact with each other but do not slide relative to each other, and the sliding friction force refers to the acting force between two objects which are in contact with each other but slide relative to each other.Belt tension depends on the elasticity degree of belt, and along with belt transmission in the ageing of belt, some contact particles are worn smoothly, and the frictional force of belt can progressively reduce, after reducing to a certain degree, can appear trouble operating modes such as skidding.
In the working process of the variable-pitch belt of the wind driven generator, due to the influence of fatigue and the humidity, the temperature and the like of a working environment, after the belt runs for a long time, the rubber is aged due to the change of the contact condition between the belt and the supporting shaft, so that the rubber viscosity of the belt is poor. During the reduction of the friction, there may be a phenomenon that the belt slips. The position transmission is inaccurate due to the slippage of a belt of a transmission system, a driven wheel part is not pushed forcefully, the pitch angle of the blade cannot reach a designated position, and the unbalance of the stress of the blade of the wind driven generator can be caused by the deviation of the pitch angles of the three blades.
The relationship of the forces between the three components of the drive belt, the drive shaft and the driven shaft is analyzed. Fig. 4 establishes a mechanical analysis theory of the gear transmission slip fault, and the abscissa in fig. 4(a) - (c) is time, the ordinate is force applied and friction force applied to the belt, wherein fig. 4(a) is a relationship analysis diagram of forces among the transmission belt, the driving shaft and the driven shaft under normal working conditions, and the three curves coincide under normal working conditions; FIG. 4(b) is a diagram of force relationship analysis between the driving belt, the driving shaft and the driven shaft under complete slip, and the curves of the friction force and the electromagnetic force are superposed; fig. 4(c) is a graph showing the relationship of the force between the drive belt, the drive shaft, and the driven shaft under the cyclic slip. The driving wheel is subjected to electromagnetic force, and the driven wheel is subjected to magnetic powder braking force. And analyzing the mechanical conditions of three working conditions, namely a normal working condition, a periodic slipping working condition and a complete slipping working condition respectively. Under normal operating conditions, the force borne by the belt is smaller than the static friction force, relative displacement does not exist between the belt and the transmission shaft, and the variable pitch motor can well drive the blades to rotate to the specified position. The belt brake has the advantages that the belt brake has relative displacement at any time under the working condition of severe fault, namely complete slipping, the force provided by the magnetic powder brake exceeds the static friction force, and the sliding friction force is formed between the belt and the transmission shaft at the moment.
There is a transition condition of periodic slippage between the normal condition and full slippage. When the given force of the magnetic-particle brake is exactly equal to the static friction force, t is one period as shown in fig. 4(c)1～t2Time: sliding friction between the driving wheel and the belt, relative displacement (slip condition) between the belt and the driving wheel, t2～t3Time: static friction between the driving wheel and the belt, rotation of the driven wheel, and no relative displacement (normal working condition) between the belt and the driving wheel exist. The braking force provided by the magnetic powder brake is a determining condition for maintaining the transition working condition, the friction force presents periodic square wave fluctuation between static friction force and sliding friction force, the electromagnetic force is attracted by the friction force, and the friction force follows the sine fluctuation, so that the periodic slip transition working condition existing under a force signal, a current signal and a position signal is successfully disclosed, and the belt aging slip fault diagnosis under the sensorless condition can be realized by utilizing the fault characteristic component in the current under the special working condition of periodic slip.
Fig. 4(d) shows the speed information of the driving shaft, the driven shaft, and the belt under the condition of the periodic slip, and it can be seen from the figure that although the speed trends of the driving shaft and the driven shaft are opposite, the expressed periodicity is consistent.
The model of the residual effective service life of the variable-pitch transmission belt of the wind driven generator is established according to the mechanical analysis and is shown in figure 5.
And analyzing the influence of the periodic fluctuation on the force on the stator current signal of the variable pitch drive motor, and realizing fault diagnosis under the condition of no sensor. The effect of torque vibration on the rotor magnetomotive force was first analyzed. Failure of the drive belt can cause the motor to add a frequency fault component f to the original load torquebug. Therefore, the load torque T at the time of the motor belt slip failureL(t) may be represented as.
TL(t)＝T0+Tbugcos(ωbugt) (2)
Wherein, T0A constant component of torque under normal load, TbugFor additional torque signaling under fault loading,ωbugthe angular frequency of the additional torque signal under fault loading.
According to the kinetic equation of the motor drive system.
Wherein T is the torque amount, TeIs the electromagnetic torque of the machine, TLIs the load torque of the motor, J is the load moment of inertia of the motor, omegarThe angular frequency of the motor.
The influence of the additional fault torque on the parameters is analyzed, and the angle influence equation of the fault can be obtained.
Wherein, thetarAnd (t) is the motion angle error of the motor rotor, and the equation (5) shows that the vibration component generated by the fault adds a cosine component to the rotation position of the rotor.
When the motor normally operates, the rotor magnetomotive force under the rotor reference system is
Wherein,
is the rotor magnetomotive force in the rotor coordinate system, FrIs the rotor magnetomotive force under a static coordinate system, S is the motor slip, theta' is the mechanical angle of the magnetomotive force relative to the rotor in a rotor reference system, npIs the electromagnetic speed, omega, of the motorsIs the electromagnetic angular frequency of the motor.
Through the change of the stator and rotor reference coordinate system theta ═ theta' + thetarIs obtained by
θ'＝θ-ωr0-Abugcos(ωbugt) (7)
Wherein, ω isr0Is the initial angular frequency of the rotor of the motor,
is the magnitude of the fault component in the rotational position angle. The equation of the magnetomotive force obtained in the formula (6) in the stator coordinate system is
Fr(θ,t)＝Frcos(npθ-ωst-npAbugcos(ωbugt)) (8)
As can be seen from the equation (8), the fault component of the torque ripple generated by the fault induced in the air gap magnetomotive force is-npAbugcos(ωbugt)。
From which a magnetic flux of
Φ(θ,t)＝FrΛ0cos(npθ-ωst-npAbugcos(ωbugt)) (9)
Where Φ is the flux of the machine and Λ0Is the magnetic conductance of the motor, and the current equation obtained by the analysis is
Wherein, I1Is the fundamental current amplitude, I, of the motor2The amplitude of the fault current caused by the periodic slip fault of the belt is obtained by derivation of the phase position in the current
Where f (t) is the frequency of the motor at which a belt failure occurs, since
Smaller, so f (t) may be regarded as ≈ fs±fbug(12)
Graphically representing the derivation of the above equations as shown in fig. 6, fig. 6(a) is a normal motor stator current signal plot, fig. 6(b) is a belt periodic fault modulation current signal plot, and fig. 6(c) is a post-fault modulation motor stator current plot; i.e. the frequency to which the periodic fault corresponds. From fig. 6, it can be found that, in the case of a slip fault of the transmission belt, because the fault has strong attenuation in the frequency spectrum diagram, the fault side band in the gear fault is not exhibited in the stator current of the driving motor, but two fault characteristic component peaks appear near the fundamental frequency similar to the motor body rotor broken bar fault, and the fault characteristic frequency is determined by the material property of the transmission belt and the surface tension received by the transmission belt.
Fault diagnosis method for variable-pitch transmission belt of wind driven generator
Based on the above principle analysis, the invention provides a wind driven generator variable pitch drive belt fault diagnosis method based on current signals, which is combined with a flow chart 14 and comprises the following steps:
s100, obtaining a motor stator current signal I of a driving shaft of a variable pitch belt transmission system, wherein the motor stator current signal I can be led out by a control system of the variable pitch belt transmission system without adding a new current sensor;
s200, preprocessing the motor stator current signal I to enable the motor stator current signal I to meet the requirements of a monitoring system; the preprocessing comprises the steps of filtering ultrahigh frequency harmonic components in the original signals by using a filter, and normalizing and unifying the acquired data to obtain discrete motor stator current signals.
S300, obtaining a spectrogram by using a data analysis method; for example, fast fourier transform or wavelet transform, data processing is performed on the preprocessed current signal, and the current signal is transformed into a frequency domain; s400, fault diagnosis is carried out, namely whether fault side frequency peaks occur in the current signal frequency spectrum under the frequency domain is analyzed and judged, and if the fault side frequency peaks occur, the belt of the variable pitch belt transmission system is determined to have faults.
Third, experimental verification of fault diagnosis method
Because research literature of transmission belt fault diagnosis based on current signals is relatively few, the periodic slip transition working condition of the belt transmission is proved by experiments according to mechanical analysis, and relevant experimental waveforms are shown in fig. 7(a) - (c).
From the comparison of the current waveforms in the three conditions in fig. 7, it can be seen that there is periodic fluctuation in the current waveform in the periodic slip condition, as shown in fig. 7(c), compared with the normal condition and the full slip condition.
Fast fourier transform is performed on the spectrum to obtain a corresponding spectrogram as shown in fig. 8. It can be seen from fig. 8 that due to the presence of the periodic slip fault, there are 3Hz spaced spikes on either side of the fundamental frequency of the spectrogram, in keeping with the theory presented earlier. Since the periodic slip fault is intermediate between the normal and slip faults of the belt, it is possible to monitor the slip fault caused by the aging of the drive belt. In order to further analyze the special transient state condition, the position information is closer to the fault source, so that the reliability is higher, and auxiliary analysis is carried out by means of the position signal of the encoder arranged on the driven wheel. The obtained position pulse signal is converted into a torsional vibration signal of the driven gear as shown in fig. 9.
It can be seen from figure 9 that the driven wheel rotation frequency also takes the form of a sum of approximately constant speed + sinusoidal fluctuations, another observed phenomenon being the presence of rapid jitter at the peaks.
The acquired frequency-converted signal is fast fourier transformed into the spectrum waveform of fig. 10. It can be seen from fig. 10 that there is also a peak at 3Hz of the position signal spectrum, which is highly consistent with the current signal spectrum. The periodic slip transition working condition provided by the method is verified from two angles of the current signal and the position signal, and the slip fault diagnosis of the transmission belt without the position sensor can be realized by utilizing the transition working condition.
Fourthly, determining fault characteristic frequency
The biggest problem with pitch drive belts, unlike pitch drive gears, is that there is not a computationally accurate fault signature frequency for which only a rough estimate can be made. When the fault characteristic frequency is low, the fault period is long, the belt is in a slipping working condition for a long time, and the belt is difficult to return to a normal working condition; when the fault characteristic frequency is high, the fault period is short, the electromagnetic force is difficult to reflect the rapid change of the friction force, and the transition working condition of periodical slipping can not occur. According to the previous experiment, it can be analyzed that the fault characteristic frequency should fluctuate within a range of several Hz from the fundamental frequency, and it is neither possible to be too small nor too large, which would result in too short a cycle, and the corresponding fault characteristic peak value is not sufficient, which would result in too long a cycle, and the belt is directly stationary. The difference between the static friction and the sliding friction is the root cause of the generation of the characteristic frequency of the fault, and the difference between the two divided by the moment of inertia is equal to the angular acceleration, and the integral thereof can be used to obtain the characteristic frequency of the fault, as shown in fig. 11.
J＝∫∫∫vr2dm＝∫∫∫vr2ρdv (13)
Where J is the moment of inertia of the object, r is the perpendicular distance from the cell to the axis of rotation, and ρ is the density at that location. By using the formulas (13) and (14), the equivalent moment of inertia J converted to the output end of the motor rotor can be calculatedzIs 0.0039kg · m2The load moment corresponding to the periodic slip transition condition at the 20Hz fundamental frequency is about 3.17N m, the moment of the difference between the frictional forces is approximately in direct proportion to the static frictional force and approximately in direct proportion to the load moment, and the torque delta T of the difference between the estimated static frictional force and the estimated slip frictional force is 0.19N m. Substituting the following equation.
Wherein alpha is the rotor rotation angle, feTo driveThe result obtained by the fault characteristic frequency under the periodic slip working condition is not greatly different from the fault characteristic frequency of 3Hz appearing under the fundamental frequency of 20Hz in the previous experiment. This enables an estimation of the characteristic frequency of the periodic slip fault in a belt drive.
The relation between the fault characteristic frequency and the fundamental frequency is studied whether the fault characteristic frequency shows linear increase along with the increase of the fundamental frequency like a transmission gear. The formula is derived as follows.
From the equation (18), it can be derived that the fault characteristic frequency is in direct proportion to the fundamental frequency, and the experimental results of the fault characteristic frequencies for different fundamental frequencies are shown in fig. 12.
As can be seen from fig. 12, the corresponding fault characteristic frequencies appear at the fundamental frequencies of 20Hz, 30Hz, 40Hz and 50Hz, consistent with the theoretical analysis presented previously. But the corresponding fault characteristic frequency can not appear under the working condition of 10Hz fundamental frequency. The corresponding explanation is as follows: because the transmission belt is manually replaced in a laboratory, the tension of the belt is insufficient, under the condition of low frequency, the friction force is small, the sine-form fluctuation of the electromagnetic force is difficult to maintain due to the difference between the static friction force and the sliding friction force, and the transmission belt is directly changed from a normal working condition to a sliding working condition. The correspondence between the fundamental frequency and the characteristic frequency of the fault is shown in fig. 13.
As can be seen from fig. 13, the fundamental frequency is approximately linear with the failure characteristic frequency, and as the fundamental frequency increases, the rotational angular velocity of the propeller shaft increases, resulting in a decrease in the failure period, and thus an increase in the failure characteristic frequency. The peak frequency of the failure signature depends primarily on the material of the drive train belt and the surface tension at installation. The magnetic powder braking forces at the corresponding different fundamental frequencies are shown in table 1.
TABLE 1 magnetic powder brake force for maintaining periodic slip transition condition under different fundamental frequencies
As can be seen from table 1, as the fundamental frequency increases, the magnetic powder braking force for maintaining the periodic slip transition condition increases slightly, the fundamental frequency increases, which results in an increase in the speed of the belt, the tension applied to the opposite belt increases slightly, and the corresponding magnetic powder braking force required to maintain the periodic slip transition condition increases slightly, which is mutually verified with the method proposed before.
It is noted that the fault signature frequency is not fixed, but varies with the change in fundamental frequency.
The fault side frequency peak of the current signal exists at the fault characteristic frequency, namely, the frequency domain curve of the current signal has the amplitude which is lower than the fundamental frequency but is obviously outstanding at the fault characteristic frequency. As shown in fig. 13, the fault signature peaks fluctuate in a range of less than 10Hz on either side of the fundamental frequency. Further, from the above analysis, it can be seen that the step S400 of determining whether the fault side peak occurs in the spectrum includes:
the fault side frequency peak appears in the range of several Hz from the base frequency and fluctuates at f1±feSymmetrically existing near the position, so that f can be as follows1±feThere is a fault spike near the location.
The fault characteristic frequency is calculated by the following formula:
wherein f iseFor the fault characteristic frequency, Δ T is the torque of the difference between the static friction and the sliding friction, JzTo translate to the equivalent moment of inertia at the rotor output of the motor.
In one embodiment, the comparison with the current spectrum of the normal operation mode can be adopted to judge whether the fault side frequency peak exists.
Further, if the current signal in the frequency domain has fault side frequency peaks, the periodic slippage of the belt of the variable pitch belt transmission system is determined. At this time, proper early warning and timely maintenance are required.
In summary, the invention provides a fault diagnosis method for a variable pitch drive belt of a wind driven generator based on a current signal, which specifically comprises the following steps:
the periodic slip transition working condition is provided for the fault diagnosis of the transmission belt. It is believed that there is a periodic slip transient condition between the normal condition and the slip condition during belt aging. Mechanical analysis is carried out, and the scientificity of theories proposed by self is verified from multiple angles;
aiming at the topic of failure diagnosis of a variable-pitch transmission belt of a wind driven generator which has never been researched, a failure diagnosis method based on a current signal is provided, and the establishment of a non-invasive and sensorless transmission belt health management system is realized;
aiming at the proposed periodic slip transition working condition, the complete formula derivation from mechanics to torque to current signals is realized, the expression form of the periodic slip transition working condition in a current frequency spectrum is given, and the fault characteristic peak value of the periodic slip transition working condition is carefully analyzed.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.
Claims (9)
1. A fault diagnosis method for a variable pitch drive belt of a wind driven generator based on a current signal is characterized by comprising the following steps:
acquiring a current signal of a driving shaft motor stator of a variable pitch belt transmission system;
preprocessing the motor stator current signal;
obtaining a frequency spectrum diagram of the preprocessed motor stator current signal by using a data analysis method;
if the fault side frequency peak occurs in the frequency spectrum within the set range from the fundamental frequency, the belt of the variable pitch belt transmission system is determined to have a fault;
the fault signature frequency is calculated by the following formula:
wherein f iseFor the fault characteristic frequency, Δ T is the torque of the difference between the static friction and the sliding friction, JzAnd converting the equivalent rotational inertia of the output end of the motor rotor for the transmission belt.
2. The method for diagnosing the fault of the variable pitch drive belt of the wind driven generator based on the current signal as set forth in claim 1, wherein: and the motor stator current signal is obtained by a control system of a variable pitch belt transmission system.
3. The method for diagnosing a fault of a pitch drive belt of a wind turbine generator based on a current signal according to claim 1 or 2, wherein: the preprocessing comprises filtering ultrahigh frequency harmonic waves by a filter and normalizing the acquired data.
4. The method for diagnosing a fault of a pitch drive belt of a wind turbine generator based on a current signal according to claim 1 or 2, wherein: the data analysis method comprises fast Fourier transform or wavelet transform.
5. The method for diagnosing a fault of a pitch drive belt of a wind turbine generator based on a current signal according to claim 1 or 2, wherein: the fault side frequency peak appears within 10Hz from the fundamental frequency.
6. The method for diagnosing a fault of a pitch drive belt of a wind turbine generator based on a current signal according to claim 1 or 2, wherein: the fault side frequency peak appears at f1±feFrequency; f. of1Is the fundamental frequency, f, of the motor stator current signaleIs the fault signature frequency.
7. The method for diagnosing a fault of a pitch drive belt of a wind turbine generator based on a current signal according to claim 1 or 2, wherein: the fault characteristic frequency changes along with the change of the fundamental frequency and always appears on two sides of the fundamental frequency.
8. The method for diagnosing a fault of a pitch drive belt of a wind turbine generator based on a current signal according to claim 1 or 2, wherein: the failure of the belt is a periodic slip.
9. The method for diagnosing a fault of a pitch drive belt of a wind turbine generator based on a current signal according to claim 1 or 2, wherein: the method also comprises the steps of early warning and overhauling after the belt breaks down.
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| CN114252261B (en) * | 2021-12-21 | 2024-03-08 | 沈阳顺义科技股份有限公司 | Fault diagnosis method and system for steering system of comprehensive transmission device |
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