Method for monitoring torsional resonance of high-voltage frequency converter driving load shaft system

Abstract

The invention discloses a high-voltage frequency converter driving load shaft system torsional resonance monitoring method. The method comprises the following steps: arranging an encoder on a shaft system to collect shaft system rotating speed information in real time; inputting the encoder signal into a rotating speed acquisition and processing module in a frequency converter master control system so as to process the encoder signal into a signal format which can be identified by a storage and calculation chip of the frequency converter master control system; inputting the processed encoder signal into a torsion angle calculation and analysis module in a storage calculation chip so as to carry out shaft system torsion angle calculation and torsion angle harmonic analysis; and according to the calculated torsion angle amplitude condition, a torsional vibration alarm module in the storage calculation chip gives an alarm. As a further scheme of the invention, the encoder is an electromagnetic pulse encoder. The method can be used as an online monitoring and alarming means for torsional vibration of a high-capacity fan and water pump load variable-frequency driving shaft system, the problems of system shutdown and the like caused by irreversible fatigue damage of the shaft system due to hidden torsional vibration of the shaft system are solved, and the implementation cost is low.

Description

Technical Field

[0001] The invention relates to the technical field of shaft system vibration measurement, and in particular to a method for monitoring torsional resonance of a load shaft system driven by a high-voltage frequency converter. Background Art

[0002] As the country attaches great importance to energy conservation and emission reduction, energy conservation and consumption reduction of rotating motor equipment has been mentioned in an important position. Energy conservation of motors is generally achieved through speed regulation by frequency converters. Since fan and water pump loads have the characteristic that power and speed are in a cubic relationship, frequency conversion speed regulation of fan and water pump loads can greatly reduce energy consumption.

[0003] In recent years, with the increasing application of high-voltage inverters in large-capacity fan systems, many domestic and foreign brand manufacturers have encountered many cases of mechanical parts on the shaft system being damaged after the large-capacity fan system was transformed into variable frequency speed regulation. According to investigations, damage to the motor shaft, fan shaft and coupling diaphragm has been found. Since large-capacity fans play an important role in the system and are of high value, once they are damaged, the unit will be shut down unplanned, which will cause great economic losses to users. In addition, once the damage is caused by the transformation of variable frequency speed regulation, users will not invest in inverters before analyzing the exact cause. At the same time, users who have not transformed the variable frequency speed regulation will also question the transformation, which will be detrimental to the promotion and application of high-voltage inverters.

[0004] The cause of the above shaft damage phenomenon has been confirmed to be metal fatigue damage caused by the cross force caused by long-term torsional resonance of the shaft. At present, the shaft damage caused by the above shaft torsional vibration problem often occurs in a long-term hidden manner, generally causing damage to different mechanical parts on the shaft after a few days to a few months, and eventually triggering a severe mechanical resonance alarm or other alarms to cause load tripping. There is a lack of long-term and effective monitoring methods for variable frequency drives of large-capacity fans and water pumps. Summary of the invention

[0005] The purpose of the present invention is to provide a method for monitoring the torsional resonance of the load shaft system driven by a high-voltage frequency converter, in view of the lack of online monitoring and alarm means for the torsional vibration of the variable frequency drive shaft system of large-capacity fans and water pumps, and the serious problems such as system shutdown caused by the hidden occurrence of torsional vibration of the shaft system causing irreversible fatigue damage to the shaft system. The method collects the speed pulse signal of the load shaft system during operation through an encoder, and uses analysis software to perform signal recognition to obtain the characteristics of the torsional vibration natural frequency and torsion angle of the shaft system. If the torsion angle of the shaft system is found to be too large, an alarm will be issued to the frequency converter.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for monitoring torsional resonance of a load shaft system driven by a high-voltage inverter, comprising:

[0008] By setting an encoder on the shaft system, the shaft system speed information can be collected in real time;

[0009] Input the encoder signal into the speed acquisition processing module in the inverter main control system to process the encoder signal into a signal format that can be recognized by the storage and computing chip of the inverter main control system;

[0010] The processed encoder signal is input into the torsion angle calculation and analysis module in the storage and calculation chip to perform shaft system torsion angle calculation and torsion angle harmonic analysis;

[0011] According to the calculated torsion angle amplitude, an alarm is issued through the torsional vibration alarm module in the storage calculation chip.

[0012] As a further solution of the present invention, the encoder is an electromagnetic pulse encoder.

[0013] As a further solution of the present invention, the speed acquisition processing module includes an input protection circuit, a filter circuit and a signal level conversion circuit; the input protection circuit uses a diode clamp circuit and a current limiting resistor to limit the input voltage to -0.7V to U max+ 0.7V; the filter circuit uses an RC low-pass filter circuit to filter out high-frequency noise; the signal level conversion circuit converts the voltage amplitude to U max The signal is converted into a safe voltage signal recognizable by the storage computing chip and input into the chip analog channel.

[0014] As a further solution of the present invention, the specific process of calculating the shaft system torsion angle includes:

[0015] Take the number of encoder gear teeth as Z, and the period of each pulse in the signal as T i , then the average angular velocity of the gear during one revolution is:

[0016]

[0017] The instantaneous angular velocity of each gear tooth when it passes the sensor is:

[0018]

[0019] The difference between the instantaneous angular velocity and the average angular velocity is defined as the speed fluctuation caused by torsional vibration:

[0020]

[0021] The torsional vibration amplitude angle can be obtained by integrating the speed fluctuation value over time:

[0022]

[0023] The calculation formula for the instantaneous speed and torsional vibration angle obtained by averaging n gear teeth is as follows:

[0024]

[0025] As a further solution of the present invention, the specific process of calculating the torsion angle harmonics includes:

[0026] The calculated torsional vibration angle signal is stored in the memory. After storing N torsional angle signals, it enters the DFT calculation module. The calculation module expression is as follows:

[0027]

[0028] In the above formula, X(k) represents the result after DFT transformation, x(n) is the sampling signal, and the sampling frequency of the sampling process is f s , then the sampling period T s =1 / f s , N is the number of sampling points of the signal, and the Euler formula is used to replace it:

[0029]

[0030] Real part:

[0031] Imaginary part: According to the properties of DFT, the amplitude and phase of the actual signal at each frequency point are:

[0032]

[0033] In the above two equations, Amp(k*Δf) and φ(k*Δf) are the amplitude and phase at the frequency k*Δf, respectively. Δf is the frequency resolution of DFT analysis, and its value is related to the sampling process. s / N.

[0034] As a further solution of the present invention, the specific process of torsional vibration alarm includes:

[0035] The storage and calculation chip of the inverter main control system calculates the torsional angle amplitude of all frequency points through the DFT algorithm, and calculates the torsional vibration frequency f according to the set torsional vibration frequency f. vib , search for f vib The maximum value of the torsion angle amplitude within ±5Hz range Amp vib ;

[0036] When Amp is detected 100 times in a row vib Higher than the torsion angle alarm threshold Amp th After that, the torsional vibration amplitude exceeds the limit alarm flag is set. After the inverter main control system detects that the flag is set, it sets the system minor fault flag and uploads the fault information to the display screen and DCS system.

[0037] As a further solution of the present invention, when the torsional vibration amplitude exceeds the limit alarm flag is set, the Amp vib Below the torsion angle alarm threshold Amp th After the torsional vibration amplitude exceeds 50%, the alarm mark of excessive torsional vibration amplitude is cleared.

[0038] As a further solution of the present invention, the torsion angle alarm threshold Amp th According to the reverse deduction of torsional stress under the condition of 50% allowable shear stress, the following formula is obtained:

[0039]

[0040] In the above formula, τ -1 is the torsional fatigue limit of the rotor material at the encoder location, G is the shear modulus of the rotor material, L is the axial distance from the torsional node to the encoder location, and ρ is the shaft radius at that location.

[0041] In the second aspect, the present invention provides a high-voltage inverter-driven load shaft system torsional resonance monitoring system, including an encoder installed on the shaft system and a speed acquisition and processing module, a torsion angle calculation and analysis module and a torsional vibration alarm module arranged in the inverter main control system; the encoder is used to collect shaft system speed information in real time; the speed acquisition and processing module is used to process the encoder signal into a signal format that can be recognized by the storage and computing chip of the inverter main control system; the torsion angle calculation and analysis module is used to perform shaft system torsion angle calculation and torsion angle harmonic calculation on the processed encoder signal; the torsional vibration alarm module is used to issue an alarm prompt based on the calculated and analyzed torsion angle amplitude.

[0042] As a further solution of the present invention, a 485 communication interface, a 4-20mA channel and a minor fault output channel are also provided in the inverter main control system, wherein the 485 communication interface is connected to the display screen, and the 4-20mA channel and the minor fault output channel are connected to the DCS system.

[0043] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0044] 1. The present invention arranges an encoder on the shaft system to collect shaft system speed information in real time, and inputs the encoder signal into the speed collection and processing module in the inverter main control system for processing, and then inputs the processed encoder signal into the torsion angle calculation and analysis module in the storage and calculation chip to calculate the shaft system torsion angle and torsion angle harmonic analysis, and issues an alarm through the torsion vibration alarm module in the storage and calculation chip according to the calculated torsion angle amplitude; this method can be used as a technical means for online monitoring and alarm of torsional vibration of the shaft system of variable frequency drive of large-capacity fans and water pumps, so as to avoid the problems such as system shutdown caused by the hidden occurrence of shaft system torsional vibration and irreversible fatigue damage of the shaft system;

[0045] 2. Based on the existing main control system of the high-voltage frequency converter, the present invention adopts a scheme of installing an electromagnetic encoder at the motor shaft extension end, and implements a scheme of torsion angle calculation and analysis and alarm system on the existing storage and computing chip of the main control system. At the same time, the existing display screen, analog output and digital output channels of the frequency converter are used to form a set of inexpensive shaft torsional vibration online monitoring and alarm system, without the need to add expensive signal acquisition and torsional vibration online monitoring instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0047] Figure 1 It is a schematic diagram of the shaft system of the dual-mass transmission system;

[0048] Figure 2 It is the first-order equivalent block diagram of the elastic shaft system;

[0049] Figure 3 is the shaft torsional resonance amplitude spectrum;

[0050] Figure 4 It is a diagram of the torsional resonance monitoring scheme of the load shaft system driven by the high-voltage frequency converter in the present invention;

[0051] Figure 5 It is the waveform diagram of the encoder pulse signal in the present invention;

[0052] Figure 6 This is a schematic diagram of the torsion angle calculation and analysis principle in the present invention;

[0053] Figures 7 to 11 The simulation calculation results of the torsion angle and harmonic analysis scheme in the present invention;

[0054] Figure 12 to Figure 14 The monitoring results of shaft torsional resonance were obtained for frequency conversion transformation of static draft control in a thermal power plant. DETAILED DESCRIPTION

[0055] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0057] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0058] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0059] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0060] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0061] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces), unless otherwise clearly and specifically defined.

[0062] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0063] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0064] At present, after the frequency conversion speed regulation transformation of large-capacity fan and water pump loads, the mechanical parts on the shaft system are often damaged. It has been confirmed that the cause is the metal fatigue damage caused by the cross force caused by the long-term torsional resonance of the shaft system. In the general concept, the mechanical shaft between the motor and the load is a rigid body, and the speed and angle of rotation at both ends of the shaft are the same. In fact, the shaft is elastic, and it must be twisted at a certain angle to transmit torque. The speed and angle of rotation at both ends of the shaft are different. If the shaft is short and thick, its elastic deformation can be ignored and it can be regarded as a rigid body. If the shaft is slender, the elastic deformation cannot be ignored, and the shaft system becomes an oscillation link. If no measures are taken, shaft torsional oscillation (referred to as shaft torsional vibration) may occur, leading to accidents. In the transmission system, the motor M drives the load through a mechanical shaft. Figure 1 shown.

[0065] The shaft is elastic and needs to be twisted at a certain angle Δθ to transmit torque. The speed and angle of rotation of the motor and the load are not exactly the same, which is called a two-mass system. The first-order equivalent block diagram of the elastic shaft system is as follows Figure 2 shown.

[0066] The torque between the motor and the load is the shaft torque T s The shaft torque is calculated as follows:

[0067] T s =K s (θ m -θ f )+D s (ω m -ωf )

[0068] =K s Δθ+D s Δω

[0069] Where: K s is the elastic coefficient of the shaft, and Δθ is the torsion angle of the shaft. The motion equation of the two-mass system is as follows:

[0070]

[0071] Where: T m is the electromagnetic torque of the motor, T f is the load torque, J m and J f are the motor and load moments of inertia, D m , D f and D s are the mechanical damping coefficients of the motor, load and mechanical axis respectively.

[0072] The transfer function between shaft torque, motor electromagnetic torque and load torque is a second-order oscillation link. The amplitude spectrum of the transfer function is as follows: Figure 3 As shown. When T m or T f When there are excitation components near the torsional vibration frequency components (steady-state harmonic torque, rapid acceleration and deceleration, sudden load increase and decrease, and large torque impact faults, etc.), the shaft torque T s Hundreds or even thousands of times the natural frequency will be generated, that is, the shaft will experience torsional vibration.

[0073] At present, the shaft damage caused by the above-mentioned shaft torsional vibration problem often occurs in a long-term hidden manner, generally causing damage to different mechanical components on the shaft after several days to several months, and eventually triggering a severe mechanical resonance alarm or other alarm causing the load to trip. There is a lack of long-term and effective monitoring methods for variable frequency drives of large-capacity fans and water pumps.

[0074] In view of this, the applicant, after in-depth research, invented a technical means that can add online detection of load shaft torsional resonance on large-capacity load variable frequency drives. Specifically, a speed encoder or gear plate is installed on the rotating shaft, which can generate a pulse timing signal to the acquisition system or the induction probe during rotation. The signal is identified by analysis software to obtain the characteristics of the shaft torsional vibration natural frequency and torsion angle. After the torsional resonance of the shaft is detected, a minor fault alarm is issued on the local inverter and the remote control system respectively.

[0075] Example 1

[0076] like Figure 4The figure shows a shaft torsional resonance monitoring scheme diagram. A method for monitoring shaft torsional resonance of a load driven by a high-voltage inverter is provided in an embodiment of the present application, comprising:

[0077] By setting an encoder on the shaft system, the shaft system speed information can be collected in real time;

[0078] Input the encoder signal into the speed acquisition processing module in the inverter main control system to process the encoder signal into a signal format that can be recognized by the storage and computing chip of the inverter main control system;

[0079] The processed encoder signal is input into the torsion angle calculation and analysis module in the storage and calculation chip to perform shaft system torsion angle calculation and torsion angle harmonic analysis;

[0080] According to the calculated torsion angle amplitude, an alarm is issued through the torsional vibration alarm module in the storage calculation chip.

[0081] Usually, there is no speed encoder device in industrial high-power motor load drive application scenarios, and the high-voltage inverter cannot directly measure the rotational speed. The detection of shaft torsional vibration requires the detection of shaft speed information. Therefore, the embodiment of the present application adopts the solution of installing a large-diameter encoder at the motor shaft extension end.

[0082] At present, large-diameter encoders are mainly divided into photoelectric and electromagnetic types. Since the on-site unit environment is outdoors and a large amount of dust is generated when starting or stopping the machine, dust attached to the surface of the grating or photosensitive element or a large amount of particulate matter in the air will affect the signal. Therefore, an electromagnetic pulse encoder is used in the embodiment of the present application. As long as there is no large amount of magnetic sensitive material in the use environment, the electromagnetic induction is relatively stable. The output signal of the electromagnetic pulse encoder is a pulse signal with a minimum voltage of 0V and a maximum voltage of U max (usually 5V or 24V), the pulse signal waveform is as follows Figure 5 shown.

[0083] The function of the speed acquisition and processing module is to convert the encoder signal into a signal format that can be recognized by the storage and computing chip. It mainly includes three parts: input protection circuit, filter circuit and signal level conversion circuit.

[0084] In order to prevent the overvoltage and overcurrent on the input pulse signal line from damaging the subsequent circuit, the input protection circuit uses a diode clamp circuit and a current limiting resistor at the signal input end to limit the input voltage to -0.7V to U max+ 0.7V range. Since the encoder output signal may be subject to certain noise interference, the filter circuit uses an RC low-pass filter circuit to filter out high-frequency noise. Usually, the encoder output pulse frequency is ≤10kHz, and the RC low-pass filter circuit cutoff frequency can be set to 15kHz. The signal level conversion circuit converts the voltage amplitude to U maxThe signal is converted into a safe voltage signal recognizable by the storage computing chip and input into the chip analog channel.

[0085] The torsion angle calculation and analysis part in the embodiment of the present application is executed in the storage calculation chip of the inverter main control system. The calculation principle is as follows: Figure 6 shown.

[0086] The specific process of calculating the shaft system torsion angle in this embodiment is as follows:

[0087] Take the number of encoder gear teeth as Z, and the period of each pulse in the signal as T i , then the average angular velocity of the gear during one revolution is:

[0088]

[0089] The instantaneous angular velocity of each gear tooth when it passes the sensor is:

[0090]

[0091] The difference between the instantaneous angular velocity and the average angular velocity is defined as the speed fluctuation caused by torsional vibration:

[0092]

[0093] The torsional vibration amplitude angle can be obtained by integrating the speed fluctuation value over time:

[0094]

[0095] Random errors may be introduced into the measurement results due to factors such as vibration of the sensor mounting bracket and gear tooth processing errors. Generally, the true value can be approximated by averaging a limited number of connected data with random errors. The instantaneous speed and torsional vibration angle can be calculated by averaging n (n is generally 5 to 10, too few averages will not eliminate the error, and too many averages will weaken the vibration signal component) gear teeth as follows:

[0096]

[0097] The specific process of calculating the torsion angle harmonics in this embodiment is as follows:

[0098] The calculated torsional vibration angle signal is stored in the memory. After storing N torsional angle signals, it enters the DFT calculation module. The calculation module expression is as follows:

[0099]

[0100] In the above formula, X(k) represents the result after DFT transformation, x(n) is the sampling signal, and the sampling frequency of the sampling process is assumed to be f s , then the sampling period T s =1 / fs , N is the number of sampling points of the signal, and the Euler formula is used to replace it:

[0101]

[0102] Real part:

[0103] Imaginary part:

[0104] According to the properties of DFT, the amplitude and phase of the actual signal at each frequency point are:

[0105]

[0106] In the above two equations, Amp(k*Δf) and φ(k*Δf) are the amplitude and phase at the frequency k*Δf, respectively. Δf is the frequency resolution of DFT analysis, and its value is related to the sampling process. s / N.

[0107] The specific process of torsional vibration alarm in this embodiment is as follows:

[0108] The storage and calculation chip of the inverter main control system calculates the torsional angle amplitude of all frequency points through the DFT algorithm, and calculates the torsional vibration frequency f according to the set torsional vibration frequency f. vib , search for f vib The maximum value of the torsion angle amplitude within ±5Hz range Amp vib ;

[0109] When Amp is detected 100 times in a row vib Higher than the torsion angle alarm threshold Amp th After that, the torsional vibration amplitude exceeds the limit alarm flag is set. After the inverter main control system detects that the flag is set, it sets the system minor fault flag and uploads the fault information to the display screen and DCS system.

[0110] When the torsional vibration amplitude exceeds the limit alarm flag, the Amp vib Below the torsion angle alarm threshold Amp th After the torsional vibration amplitude exceeds 50%, the alarm mark of excessive torsional vibration amplitude is cleared.

[0111] The torsion angle alarm threshold Amp in this embodiment th According to the reverse deduction of torsional stress under the condition of 50% allowable shear stress, the following formula is obtained:

[0112]

[0113] In the above formula, τ -1is the torsional fatigue limit of the rotor material at the encoder location, G is the shear modulus of the rotor material, L is the axial distance from the torsional node to the encoder location, and ρ is the shaft radius at that location.

[0114] The inverter main control system transmits the k*Δf and Amp(k*Δf) values ​​to the display screen through the 485 communication interface, and displays Amp vib Upload to the DCS system via the 4-20mA signal channel for long-term recording.

[0115] Example 2

[0116] A high-voltage inverter-driven load shaft torsional resonance monitoring system provided in an embodiment of the present application includes an encoder installed on the shaft system and a speed acquisition and processing module, a torsion angle calculation and analysis module, and a torsional vibration alarm module arranged in the inverter main control system; the encoder is used to collect shaft system speed information in real time; the speed acquisition and processing module is used to process the encoder signal into a signal format that can be recognized by the storage and computing chip of the inverter main control system; the torsion angle calculation and analysis module is used to perform shaft system torsion angle calculation and torsion angle harmonic calculation on the processed encoder signal; the torsional vibration alarm module is used to issue an alarm prompt based on the calculated and analyzed torsion angle amplitude.

[0117] According to some embodiments of the present application, a 485 communication interface, a 4-20mA channel and a minor fault output channel are also provided in the inverter main control system, wherein the 485 communication interface is connected to the display screen, and the 4-20mA channel and the minor fault output channel are connected to the DCS system. After the torsional resonance of the shaft system is detected, a minor fault alarm can be respectively issued on the inverter local and remote control system (DCS system).

[0118] The simulation results obtained by the torsion angle and harmonic analysis scheme in this application are as follows Figures 7 to 11 As shown. Figure 7 Calculate the actual speed, instantaneous speed and average speed. Figure 8 is the waveform and amplitude of the shaft torque fluctuation component, Fig. 9 is the torsion angle waveform and Fourier analysis result, Fig.10 is the torsion angle waveform and Fourier analysis result, Fig.11 is the per-unit value of torsional vibration frequency torque and torsion angle. According to the above simulation results, it can be seen that the torsional vibration frequency torsion angle and torsional vibration frequency shaft torque are linearly related, so they can directly characterize the severity of shaft torsional vibration.

[0119] like Figure 12 to Figure 14 As shown in the figure, the torsion angle and harmonic analysis calculation results of different torsion resonance conditions after the static adjustment induced draft of a thermal power plant was implemented with frequency conversion and the shaft torsion resonance monitoring system in this application was added, where the 1.5th order is the torsion angle amplitude Amp of the shaft torsional vibration frequencyvib .in Fig.12 The torsion angle online monitoring result (severe torsional resonance) is Fig.13 The torsion angle online monitoring result (mild torsion resonance) is Fig.14 This is the result of online monitoring of the torsion angle (without torsional resonance).

[0120] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for monitoring torsional resonance of a load shaft driven by a high-voltage inverter, characterized in that: include: By setting an encoder on the shaft system, the shaft system speed information can be collected in real time; Input the encoder signal into the speed acquisition processing module in the inverter main control system to process the encoder signal into a signal format that can be recognized by the storage and computing chip of the inverter main control system; The processed encoder signal is input into the torsion angle calculation and analysis module in the storage and calculation chip to perform shaft system torsion angle calculation and torsion angle harmonic analysis; According to the calculated torsion angle amplitude, an alarm is issued through the torsional vibration alarm module in the storage and calculation chip.

2. The method for monitoring torsional resonance of a load shaft driven by a high-voltage inverter according to claim 1 is characterized in that: The encoder is an electromagnetic pulse encoder.

3. The method for monitoring torsional resonance of a load shaft driven by a high-voltage inverter according to claim 1, characterized in that: The speed acquisition processing module includes an input protection circuit, a filter circuit and a signal level conversion circuit; the input protection circuit uses a diode clamp circuit and a current limiting resistor to limit the input voltage to -0.7V to U max+ 0.7V; the filter circuit uses an RC low-pass filter circuit to filter out high-frequency noise; the signal level conversion circuit converts the voltage amplitude to U max The signal is converted into a safe voltage signal recognizable by the storage computing chip and input into the chip analog channel.

4. The method for monitoring torsional resonance of a load shaft driven by a high-voltage inverter according to claim 1, characterized in that: The specific process of calculating the shaft torsion angle includes: Take the number of encoder gear teeth as Z, and the period of each pulse in the signal as T i , then the average angular velocity of the gear during one revolution is: The instantaneous angular velocity of each gear tooth when it passes the sensor is: The difference between the instantaneous angular velocity and the average angular velocity is defined as the speed fluctuation caused by torsional vibration: The torsional vibration amplitude angle can be obtained by integrating the speed fluctuation value over time: The calculation formula for the instantaneous speed and torsional vibration angle obtained by averaging n gear teeth is as follows:

5. The method for monitoring torsional resonance of a load shaft driven by a high-voltage inverter according to claim 4 is characterized in that: The specific process of torsion angle harmonic calculation includes: The calculated torsional vibration angle signal is stored in the memory. After storing N torsional angle signals, it enters the DFT calculation module. The calculation module expression is as follows: In the above formula, X(k) represents the result after DFT transformation, x(n) is the sampling signal, and the sampling frequency of the sampling process is f s , then the sampling period T s =1 / f s , N is the number of sampling points of the signal, and the Euler formula is used to replace it: Real part: Imaginary part: According to the properties of DFT, the amplitude and phase of the actual signal at each frequency point are: In the above two equations, Amp(k*Δf) and φ(k*Δf) are the amplitude and phase at the frequency k*Δf, respectively. Δf is the frequency resolution of DFT analysis, and its value is related to the sampling process. s / N.

6. The method for monitoring torsional resonance of a load shaft driven by a high-voltage inverter according to claim 1, characterized in that: The specific process of torsional vibration alarm includes: The storage and calculation chip of the inverter main control system calculates the torsional angle amplitude of all frequency points through the DFT algorithm, and calculates the torsional vibration frequency f according to the set torsional vibration frequency f. vib , search for f vib The maximum value of the torsion angle amplitude within ±5Hz range Amp vib ; When Amp is detected 100 times in a row vib Higher than the torsion angle alarm threshold Amp th After that, the torsional vibration amplitude exceeds the limit alarm flag is set. After the inverter main control system detects that the flag is set, it sets the system minor fault flag and uploads the fault information to the display screen and DCS system.

7. The method for monitoring torsional resonance of a load shaft driven by a high-voltage inverter according to claim 6, characterized in that: When the torsional vibration amplitude exceeds the limit alarm flag, the Amp vib Below the torsion angle alarm threshold Amp th After the torsional vibration amplitude exceeds 50%, the alarm mark of excessive torsional vibration amplitude is cleared.

8. The method for monitoring torsional resonance of a load shaft driven by a high-voltage inverter according to claim 6, characterized in that: Torsion angle alarm threshold Amp th According to the reverse deduction of torsional stress under the condition of 50% allowable shear stress, the following formula is obtained: In the above formula, τ -1 is the torsional fatigue limit of the rotor material at the encoder location, G is the shear modulus of the rotor material, L is the axial distance from the torsional node to the encoder location, and ρ is the shaft radius at that location.

9. A high voltage inverter driven load shaft torsional resonance monitoring system, characterized in that: It includes an encoder installed on the shaft system and a speed collection and processing module, a torsion angle calculation and analysis module and a torsional vibration alarm module arranged in the inverter main control system; the encoder is used to collect shaft system speed information in real time; the speed collection and processing module is used to process the encoder signal into a signal format that can be recognized by the storage and calculation chip of the inverter main control system; the torsion angle calculation and analysis module is used to calculate the shaft system torsion angle and torsion angle harmonics of the processed encoder signal; the torsional vibration alarm module is used to issue an alarm prompt based on the calculated and analyzed torsion angle amplitude.

10. The high voltage inverter driven load shaft torsional resonance monitoring system according to claim 9, characterized in that: The inverter main control system is also equipped with a 485 communication interface, a 4-20mA channel and a minor fault output channel. The 485 communication interface is connected to the display screen, and the 4-20mA channel and the minor fault output channel are connected to the DCS system.

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