Switch cabinet contact temperature rise wireless sensing method and system based on surface acoustic wave resonance

Abstract

The invention provides a switch cabinet contact temperature rise wireless sensing method and system based on surface acoustic wave resonance, and relates to the technical field of power system switch cabinet detection, and the method comprises the steps: calculating the real-time offset of a fundamental frequency and a third harmonic relative to a reference frequency, and obtaining the fundamental frequency offset and the third harmonic offset; in combination with the fundamental frequency offset and the equivalent acoustic impedance variable quantity of the oxide film, surface acoustic wave propagation path deformation caused by thermal expansion of the contact material is compensated by using a thermal-acoustic coupling partial differential equation, and the fundamental frequency net offset after temperature decoupling is obtained; sparse reconstruction is carried out on the temperature field of the contact area of the contact by adopting a compressed sensing algorithm, and three-dimensional temperature gradient distribution of the contact area of the contact is output; and inputting the three-dimensional temperature gradient distribution and historical time sequence data thereof into an intrinsic mode decomposition model for processing, and generating a dynamic self-adaptive early warning threshold value. The system has the advantages that passive, wireless, high-precision and full-space temperature rise monitoring is achieved, and intelligent operation and maintenance decision making of the switch cabinet is directly driven.

Description

Technical Field

[0001] The present invention relates to the technical field of power system switchgear detection. Specifically, it relates to a wireless sensing method and system for the temperature rise of switchgear contacts based on surface acoustic wave resonance. Background Technique

[0002] Currently, the monitoring of the temperature rise of switchgear contacts mainly relies on technologies such as thermocouples, fiber optic sensing, and infrared thermal imaging. Traditional thermocouples need to directly contact the surface of the contacts, which have problems such as complex wiring, susceptibility to electromagnetic interference, and difficulty in real-time online monitoring. Although fiber optic sensing can achieve passive measurement, its spatial resolution is limited (>5 mm), it cannot accurately locate the overheating points in the micro-regions of the contacts, and there are safety risks when deploying as it needs to penetrate the insulation structure of the switchgear. Although infrared thermal imaging technology has the advantage of non-contact, it is limited by the metal shielding effect of the cabinet body, requires window observation, and cannot achieve continuous monitoring.

[0003] Existing technologies mostly adopt single-parameter decoupling methods (such as simplified models based on the temperature-resistance relationship), which are difficult to separate the coupling interference of the thickness of the contact oxidation film and the temperature rise on the sensing signal, resulting in significant measurement errors (typical values above ±5°C), and lack the ability to reconstruct the three-dimensional temperature field of the contacts, making it difficult to provide refined data support for condition-based maintenance. Summary of the Invention

[0004] The purpose of the present invention is to provide a wireless sensing method and system for the temperature rise of switchgear contacts based on surface acoustic wave resonance to improve the above problems. To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0005] In the first aspect, the present application provides a wireless sensing method for the temperature rise of switchgear contacts based on surface acoustic wave resonance, including:

[0006] Collect the radio frequency signals reflected by the multi-modal surface acoustic wave resonator array etched on the surface of the moving / static contacts of the switchgear, separate the I / Q components through quadrature phase-locked loop demodulation technology, and calculate the real-time offsets of the fundamental frequency and the third harmonic relative to the reference frequency to obtain the fundamental frequency offset and the third harmonic offset;

[0007] Input the third harmonic offset into the surface acoustic wave propagation equation to solve the equivalent acoustic impedance change corresponding to the thickness of the contact oxidation film, and obtain the equivalent acoustic impedance change of the oxidation film;

[0008] Combine the fundamental frequency offset and the equivalent acoustic impedance change of the oxidation film, and use the thermo-acoustic coupling partial differential equation to compensate for the deformation of the surface acoustic wave propagation path caused by the thermal expansion of the contact material to obtain the net fundamental frequency offset after temperature decoupling;

[0009] According to the fundamental frequency net offset and the preset resonator spatial coordinate matrix, the compressive sensing algorithm is used to sparsely reconstruct the temperature field of the contact area of the contact, and the three-dimensional temperature gradient distribution of the contact area is output;

[0010] The three-dimensional temperature gradient distribution and its historical time series data are input into the intrinsic mode decomposition model for processing, the intrinsic mode components of the contact material fatigue characteristics are extracted, and a dynamic adaptive warning threshold is generated and the abnormal temperature rise coordinates are located.

[0011] Preferably, the radio frequency signals reflected by the multi-modal surface acoustic wave resonator array etched on the surface of the moving / static contact of the switch cabinet are collected, the I / Q components are separated by the quadrature phase-locked loop demodulation technology, and the real-time offsets of the fundamental frequency and the third harmonic relative to the reference frequency are calculated to obtain the fundamental frequency offset and the third harmonic offset, including:

[0012] The directional radio frequency antenna is arranged inside the insulating sheath of the switch cabinet, a multi-modal surface acoustic wave resonator array is etched on the contact surface of the moving / static contact, a frequency modulated continuous wave signal with a transmission frequency band of 902 - 928 MHz is emitted to excite the resonator to generate the fundamental frequency and the third harmonic surface acoustic waves, and the reflected signals are received;

[0013] The reflected signal is input into the quadrature phase-locked loop and multiplied by the local oscillation signal through a mixer to separate the in-phase and quadrature components;

[0014] Based on the in-phase component and the quadrature component of the fundamental frequency signal, its instantaneous phase angle is calculated through the arctangent function, where the instantaneous phase angle is the change in the propagation speed of the surface acoustic wave caused by the temperature rise of the contact. The in-phase component and the quadrature component of the third harmonic signal are iteratively calculated to obtain the phase angle;

[0015] The time differential of the instantaneous phase angle is taken to obtain the instantaneous frequency deviation, and then the electromagnetic noise of the switch cabinet is suppressed through 10 ms time window integration and averaging, and the smoothed fundamental frequency offset is output. The same differential-integration operation is performed on the phase angle, and then the third harmonic offset is calculated. The amplitude of the third harmonic offset is nonlinearly positively correlated with the thickness of the contact oxide film.

[0016] Preferably, the third harmonic offset is input into the surface acoustic wave propagation equation to solve the equivalent acoustic impedance change corresponding to the thickness of the contact oxide film, and the equivalent acoustic impedance change of the oxide film is obtained, including:

[0017] Extract the third harmonic frequency offset caused by the oxide film on the contact surface to form a frequency offset data matrix;

[0018] Based on the acoustic parameters of the contact material and the oxide film, a surface acoustic wave propagation equation is established;

[0019] Input the frequency offset data matrix into the surface acoustic wave propagation equation, establish the frequency offset - acoustic impedance relationship equation for each resonator at each time point, and use the nonlinear least squares method to solve for the change in the equivalent acoustic impedance of the oxide film.

[0020] Preferably, by combining the fundamental frequency offset and the change in the equivalent acoustic impedance of the oxide film, use the thermo - acoustic coupled partial differential equation to compensate for the deformation of the surface acoustic wave propagation path caused by the thermal expansion of the contact material, and obtain the net fundamental frequency offset after temperature decoupling, including:

[0021] Obtain the fundamental frequency offset of the multi - mode surface acoustic wave resonator array on the contact surface and the change in the equivalent acoustic impedance of the oxide film, and construct a thermo - acoustic - force coupling parameter matrix;

[0022] Based on the thermal expansion effect of the contact and the propagation characteristics of surface acoustic waves, establish a thermo - acoustic coupled partial differential equation to compensate for the interference of path deformation on the fundamental frequency offset;

[0023] Use an adaptive unstructured finite element mesh to numerically solve the thermo - acoustic coupled equation, and output the net fundamental frequency offset after temperature decoupling. The solving process includes generating an unstructured mesh based on the surface roughness of the contact, updating the change in the equivalent acoustic impedance of the oxide film and the fundamental frequency offset every 10 ms, and real - time tracking the growth of the oxide film and the temperature rise to perform error control.

[0024] Preferably, according to the net fundamental frequency offset and the preset resonator spatial coordinate matrix, use the compressive sensing algorithm to sparsely reconstruct the temperature field in the contact area of the contact, and output the three - dimensional temperature gradient distribution in the contact area of the contact, including:

[0025] Combine the net fundamental frequency offset with the resonator spatial coordinate matrix to construct a temperature sensitivity matrix;

[0026] Based on the statistical characteristics of the surface roughness of the contact, construct a discrete cosine transform sparse basis matrix, and combine it with the temperature sensitivity matrix to generate an observation matrix

[0027] Based on the observation matrix and the net fundamental frequency offset, establish an L1 - regularization optimization problem, minimize the weighted sum of the measurement data residual and the temperature field sparsity constraint, and use the iterative shrinkage threshold algorithm to alternately perform gradient descent updates and soft - threshold shrinkage to obtain the optimal sparse solution; then perform an inverse DCT transform on the sparse solution and apply the temperature rise physical constraint to output the three - dimensional temperature gradient distribution in the contact area of the contact.

[0028] In a second aspect, the present application also provides a wireless sensing system for the temperature rise of a switchgear contact with surface acoustic wave resonance, including:

[0029] The first calculation module: It is used to collect the radio frequency signals reflected by the multi-modal surface acoustic wave resonator array etched on the moving / static contacts of the switch cabinet, separate the I / Q components through the quadrature phase-locked loop demodulation technology, calculate the real-time offsets of the fundamental frequency and the third harmonic relative to the reference frequency, and obtain the fundamental frequency offset and the third harmonic offset;

[0030] The solving module: It is used to input the third harmonic offset into the surface acoustic wave propagation equation, solve the equivalent acoustic impedance change corresponding to the thickness of the contact oxidation film, and obtain the equivalent acoustic impedance change of the oxidation film;

[0031] The second calculation module: It is used to combine the fundamental frequency offset and the equivalent acoustic impedance change of the oxidation film, and use the thermo-acoustic coupling partial differential equation to compensate for the deformation of the surface acoustic wave propagation path caused by the thermal expansion of the contact material, and obtain the net fundamental frequency offset after temperature decoupling;

[0032] The reconstruction module: It is used to sparsely reconstruct the temperature field of the contact area of the contact according to the net fundamental frequency offset and the preset resonator spatial coordinate matrix by using the compressive sensing algorithm, and output the three-dimensional temperature gradient distribution of the contact area of the contact;

[0033] The processing module: It is used to input the three-dimensional temperature gradient distribution and its historical time series data into the intrinsic mode decomposition model for processing, extract the intrinsic mode components of the contact material fatigue characteristics, generate a dynamic adaptive warning threshold and locate the abnormal temperature rise coordinates.

[0034] Thirdly, the present application also provides a wireless temperature rise sensing device for the switch cabinet contact with surface acoustic wave resonance, including:

[0035] A memory, which is used to store computer programs;

[0036] A processor, which is used to implement the steps of the wireless temperature rise sensing method for the switch cabinet contact with surface acoustic wave resonance when executing the computer program.

[0037] Fourthly, the present application also provides a readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the steps of the above-mentioned wireless temperature rise sensing method for the switch cabinet contact based on surface acoustic wave resonance.

[0038] The beneficial effects of the present invention are as follows:

[0039] Through the multi-modal surface acoustic wave resonator array and the quadrature phase-locked loop dual-frequency demodulation technology, the present invention realizes the synchronous and independent measurement of the contact temperature rise (±0.8°C) and the oxidation film thickness (±2μm) for the problems of oxidation film thickening and temperature rise caused by long-term arc ablation of the switch cabinet contact, solves the signal coupling problem caused by the failure of traditional single sensors due to electromagnetic shielding, and significantly improves the accuracy of evaluating the contact state of the switch cabinet contact.

[0040] Based on the thermo-acoustic coupled partial differential equations, the present invention can real-time correct the interference of the thermal expansion deformation of the switch cabinet contact material on the propagation path of the surface acoustic wave under the condition of large current, eliminate the frequency deviation error (restoration degree > 95%) falsely increased due to contact expansion, and avoid the risk of misjudgment of the switch cabinet temperature rise caused by ignoring deformation in the traditional method.

[0041] The present invention uses the compressive sensing algorithm to reconstruct the three-dimensional temperature gradient distribution (resolution 0.5mm) of the contact area of the contact from sparse sensor data, breaks through the limitation of the spatial resolution of the traditional interpolation method in the switch cabinet (>5mm), can detect local overheating points with a diameter of 1mm, and supports the early warning of arc reignition and insulation deterioration in the switch cabinet.

[0042] The present invention extracts the fatigue characteristics of the contact material through empirical mode decomposition, combines with the load change of the switch cabinet to generate a dynamic warning threshold. Compared with the fixed threshold method, it adapts to the scenarios of frequent switching and load fluctuation of the switch cabinet, improves the reliability of operation and maintenance decision-making; and avoids the problems of signal distortion and false triggering caused by the failure of electromagnetic shielding of traditional electronic sensors in the switch cabinet.

[0043] Other features and advantages of the present invention will be described in the subsequent specification, and partly become obvious from the specification, or can be understood by implementing the embodiments of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the structures specifically pointed out in the written specification, claims, and drawings. Brief Description of the Drawings

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0045] Figure 1 It is a schematic flow chart of the wireless temperature rise sensing method for the switch cabinet contact with surface acoustic wave resonance described in the embodiments of the present invention;

[0046] Figure 2 It is a schematic structural diagram of the wireless temperature rise sensing system for the switch cabinet contact with surface acoustic wave resonance described in the embodiments of the present invention;

[0047] Figure 3 It is a schematic structural diagram of the wireless temperature rise sensing device for the switch cabinet contact with surface acoustic wave resonance described in the embodiments of the present invention.

[0048] In the figure: 701, the first calculation module; 702, the solution module; 703, the second calculation module; 704, the reconstruction module; 705, the processing module; 800, the wireless temperature rise sensing device for the switch cabinet contacts of surface acoustic wave resonance; 801, the processor; 802, the memory; 803, the multimedia component; 804, the I / O interface; 805, the communication component. Detailed implementation manner

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and illustrated herein generally may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but is merely representative of selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used for differential description and cannot be construed as indicating or implying relative importance.

[0051] Embodiment 1:

[0052] This embodiment provides a wireless temperature rise sensing method for the switch cabinet contacts of surface acoustic wave resonance.

[0053] See Figure 1 , the figure shows that this method includes step S100, step S200, step S300, step S400, and step S500.

[0054] S100. Collect the radio frequency signals reflected by the multi-modal surface acoustic wave resonator array etched on the surface of the moving / static contacts of the switch cabinet, separate the I / Q components through the quadrature phase-locked loop demodulation technology, and calculate the real-time offsets of the fundamental frequency and the third harmonic relative to the reference frequency to obtain the fundamental frequency offset and the third harmonic offset.

[0055] It can be understood that in this step S100, it includes S101, S102, S103, and S104, where:

[0056] S101. Set the directional RF antenna inside the insulating sheath of the switchgear cabinet. Etch a multi-modal surface acoustic wave resonator array on the contact surface of the moving / static contacts. Transmit a frequency-modulated continuous wave signal with a transmission frequency band of 902 - 928 MHz to excite the resonators to generate fundamental frequency and third harmonic surface acoustic waves, and receive the reflected signal. The calculation formula is as follows:

[0057] S r (t) = A0cos(2πf0t + φ0) + A3cos(2πf3t + φ3) + n(t)

[0058] Where A0 and A3 are the amplitudes of the fundamental frequency and third harmonic signals, φ0 and φ3 are the surface acoustic wave phase angles, n(t) is the electromagnetic noise inside the switchgear cabinet, and S r (t) is the reflected signal;

[0059] S102. Input the reflected signal into the quadrature phase-locked loop, multiply it with the local oscillation signal through a mixer, and separate the in-phase and quadrature components. The calculation formula is as follows:

[0060] I(t) = LPF[S r (t)·cos(2πf c t)], Q(t) = LPF[S r (t)·sin(2πf c t)]

[0061] Where f c is the carrier center frequency, LPF is the low-pass filter, S r (t) is the reflected signal, I(t) is the in-phase signal component, Q(t) is the quadrature signal component, cos(2πf c t) and sin(2πf c t) are the quadrature reference signals generated by the local oscillator;

[0062] It should be noted that through quadrature phase-locked loop demodulation and frequency band optimization design, the following are achieved: strong anti-interference: stably extract microvolt-level surface acoustic wave signals in the kV-level electromagnetic field; and high-precision demodulation, that is, the phase resolution reaches 0.1°, corresponding to a temperature rise detection accuracy of 0.1°C; at the same time, parameter synchronous extraction: separate the temperature rise and oxide film information from a single RF signal. The low-pass filter (LPF) filters out the electromagnetic interference inside the switchgear cabinet (such as switching overvoltage, arc noise), and retains the low-frequency signals related to the contact temperature rise and oxide film thickness.

[0063] S103. Based on the in-phase component and quadrature component of the fundamental frequency signal, calculate its instantaneous phase angle through the arctangent function, where the instantaneous phase angle is the change in the surface acoustic wave propagation speed caused by the contact temperature rise. Perform iterative calculations on the in-phase component and quadrature component of the third harmonic signal to obtain the phase angle;

[0064] Among them, the calculation formulas include:

[0065]

[0066] In the formula, T int is the integration time, and I0 / Q0 and I3 / Q3 are the I / Q components corresponding to the fundamental frequency and the third harmonic.

[0067] S104: Differentiate the instantaneous phase angle with respect to time to obtain the instantaneous frequency deviation, then perform integral averaging through a 10 ms time window to suppress the electromagnetic noise of the switchgear, output the smoothed fundamental frequency offset, and perform the same differential-integral operation on the phase angle, and then calculate the third harmonic offset. Among them, the amplitude of the third harmonic offset is nonlinearly positively correlated with the thickness of the contact oxidation film.

[0068] It should be noted that the fundamental frequency (temperature rise) and third harmonic (oxidation film) information are synchronously extracted from a single RF signal, breaking through the limitations of traditional single-parameter detection; for the strong electromagnetic interference environment of the switchgear, a composite filtering strategy of "differentiating to extract the phase change rate + integrating to smooth the noise" is adopted, and the signal-to-noise ratio is increased by > 15 dB; based on the acoustic surface wave propagation characteristics of the CuCr alloy, the Δf0-ΔT and Δf3-film thickness relationship curves are pre-calibrated to realize the direct mapping of physical parameters. Therefore, through phase analysis and frequency-domain-time-domain joint processing, the contact temperature rise and the oxidation film thickness are converted into quantifiable frequency offsets, providing high-precision input for subsequent condition assessment.

[0069] S200: Input the third harmonic offset into the acoustic surface wave propagation equation to solve the equivalent acoustic impedance change corresponding to the contact oxidation film thickness, and obtain the equivalent acoustic impedance change of the oxidation film.

[0070] It can be understood that in this step S200, it includes S201, S202, and S203, where:

[0071] S201: Extract the third harmonic frequency offset caused by the oxidation film on the contact surface to form a frequency offset data matrix;

[0072] S202: Based on the acoustic parameters of the contact material and the oxidation film, establish an acoustic surface wave propagation equation, and its calculation formula is as follows:

[0073]

[0074] In the formula, K is the acoustic impedance coupling coefficient, ΔZ ox is the equivalent acoustic impedance change of the oxidation film, ρ ox , ρ Cu is the density of CuO and CuCr alloy, ρ ox , ρ Cu is the acoustic surface wave propagation velocity of CuO and CuCr alloy;

[0075] S203. Input the frequency offset data matrix into the surface acoustic wave propagation equation, establish the frequency offset - acoustic impedance relationship equation for each resonator at each time point, and use the nonlinear least squares method to solve for the change in the equivalent acoustic impedance of the oxide film.

[0076] It should be noted that substituting the obtained third - harmonic frequency offset data matrix into the surface acoustic wave propagation equation to establish the frequency offset - acoustic impedance relationship equation for each resonator at each time point, the calculation formula is as follows:

[0077] F 3，ij = f 3，ref*

[0078] Then find ΔZ that minimizes the sum of the squares of the residuals of all equations. ox,ij , and use the Levenberg - Marquardt algorithm. Since it can efficiently handle nonlinear least - squares problems and is robust to initial values, and perform iterative steps. First, initialize ΔZ ox,ij , assuming no initial oxide film, then calculate the partial derivative of the objective function with respect to ΔZ ox,ij , construct the Jacobian matrix J, and update the solution value according to the iterative formula , where r is the residual vector and λ is the damping factor. Terminate when the residual change rate < 1e - 6 or the maximum number of iterations (100 times) is reached. In this field, dynamically adjust λ according to the vibration noise level of the switch cabinet contacts to suppress the frequency offset jitter caused by mechanical vibration (typical value λ = 0.01). If at a certain time point F3,ij exceeds the normal operating range of the contacts (|Δf3|>20kHz), it is determined as arc interference data and excluded.

[0079] It can be understood that in this embodiment, coupling the surface acoustic wave propagation equation with the acoustic impedance characteristics of the contact oxide film realizes the physical mapping from frequency offset to film thickness; the Levenberg - Marquardt algorithm dynamically adjusts parameters in combination with the working conditions of the switch cabinet, and the solution error < 3% (traditional linear method > 15%), and directly drives the switch cabinet maintenance decision - making system with the solution result d ox . Converting the frequency offset data into the change in the equivalent acoustic impedance of the oxide film through the nonlinear least - squares method breaks through the accuracy limitation of the traditional linear model and provides highly reliable input for the evaluation of the switch cabinet contact state.

[0080] S300. Combine the fundamental frequency offset and the change in the equivalent acoustic impedance of the oxide film, and use the thermo - acoustic coupling partial differential equation to compensate for the deformation of the surface acoustic wave propagation path caused by the thermal expansion of the contact material to obtain the decoupled fundamental frequency net offset.

[0081] It can be understood that in this step S300, it includes S301, S302, and S303, where:

[0082] S301. Obtain the fundamental frequency offset and the change in the equivalent acoustic impedance of the oxide film of the multimodal surface acoustic wave resonator array on the contact surface, and construct a thermo-acoustic-mechanical coupling parameter matrix. The calculation formula is as follows:

[0083] M i =[Δf 0,i , ΔZ orx，i , L 0,i

[0084] where L 0，i is the initial length of the surface acoustic wave propagation path of the i-th resonator, Δf 0，i is the fundamental frequency offset of the i-th resonator, and ΔZ or，i is the change in the equivalent acoustic impedance of the oxide film corresponding to the i-th resonator;

[0085] S302. Based on the thermal expansion effect of the contact and the propagation characteristics of surface acoustic waves, establish a thermo-acoustic coupled partial differential equation to compensate for the interference of path deformation on the fundamental frequency offset;

[0086] It should be noted that the calculation formula is as follows:

[0087]

[0088] where ΔfT is the net fundamental frequency offset after temperature decoupling (target output, unit: Hz); D is the thermal diffusivity (calibrated value of CuCr alloy: 2.3×10-5 m2 / s); γ is the thermo-acoustic coupling coefficient (experimental calibrated value: 0.15); κ is the oxide film acoustic attenuation suppression factor (calibrated value: 1.2×10-3 Hz / Rayl); v Cu is the surface acoustic wave velocity of the contact material (3500 m / s); is the Laplace operator, representing the spatial gradient of the temperature field.

[0089] Among them, it can be understood that describes the diffusion process of the temperature field on the contact surface; -κΔZ ox is to suppress the additional attenuation effect of the change in the oxide film acoustic impedance on the fundamental frequency.

[0090] S303. Numerically solve the thermo-acoustic coupling equation using an adaptive unstructured finite element mesh, and output the net fundamental frequency offset after temperature decoupling. The solving process includes generating an unstructured mesh based on the surface roughness of the contact, updating the change in the equivalent acoustic impedance of the oxide film and the fundamental frequency offset every 10 ms, and real-time tracking of the oxide film growth and temperature rise conditions, so as to perform error control.

[0091] ​It should be noted that in this embodiment, verification is carried out in a 40.5 kV switchgear cabinet: the input is θf0 = -15.6 kHz, θZ ox = 8.2×10 6 Rayl; the output is θf T = -13.1 kHz (corresponding to a temperature rise of 109.2 °C, with an error of ±0.8 °C); thus, the effect is that the coordinates of the local overheating point on the contact surface of the positioning contact are (x = 12.3 mm, y = 5.7 mm), and the deviation from the actual measurement by the infrared thermal imager is <0.5 mm.

[0092] S400. According to the net fundamental frequency offset and the preset resonator spatial coordinate matrix, use the compressive sensing algorithm to sparsely reconstruct the temperature field in the contact area of the contact, and output the three-dimensional temperature gradient distribution in the contact area of the contact.

[0093] It can be understood that in this step S400, it includes S401, S402, and S403, where:

[0094] S401. Combine the net fundamental frequency offset with the resonator spatial coordinate matrix to construct a temperature sensitivity matrix, and its calculation formula is as follows:

[0095]

[0096] In the formula, N is the number of resonators, M is the number of discretized grid points in the contact area of the contact, p i =(x i , y i , z i ) is the spatial coordinate of the i-th resonator (calibrated by the switchgear contact design drawing), g j =(x j , y j , z j ) is the coordinate of the j-th temperature field grid point (grid resolution 0.5 mm), and λ is the thermal diffusion length;

[0097] S402. Based on the statistical characteristics of the contact surface roughness, construct a discrete cosine transform sparse basis matrix, and combine it with the temperature sensitivity matrix to generate an observation matrix

[0098] S403. Based on the observation matrix and the net fundamental frequency offset, establish an L1-regularized optimization problem, minimize the weighted sum of the measurement data residual and the temperature field sparsity constraint, and use the iterative shrinkage threshold algorithm to alternately perform gradient descent update and soft threshold shrinkage to obtain the optimal sparse solution; thus, perform an inverse DCT transform on the sparse solution and apply the temperature rise physical constraint to output the three-dimensional temperature gradient distribution in the contact area of the contact.

[0099] It should be noted that the dense temperature field of the contact area is accurately reconstructed from sparse sensor data (ΔfT of N resonators), and its calculation formula is as follows:

[0100]

[0101] In the formula, To ensure the consistency between the reconstructed temperature field and the sensor data, λ||T||1 enforces the sparsity of the temperature field in the DCT domain to suppress noise interference. λ is the regularization parameter used to balance data fitting and sparsity.

[0102] The ISTA algorithm is used to solve the optimization problem, which includes initializing the temperature field, solving the number of iterations and the maximum number of iterations, and calculating the step size. Then, the gradient descent update and soft threshold shrinkage are calculated, and the convergence is judged. If |T (k+1) -T (k) ||2 < 10 -6 or k = K, the iteration is terminated; otherwise, the gradient descent update calculation continues.

[0103] Then, the sparse coefficient T is transformed from the frequency domain to the spatial domain, and the outliers are corrected. The morphological opening operation is performed on the local overheating points (Tj > 100 °C) to eliminate the false high-temperature points caused by electromagnetic interference. The surface roughness data of the contact (Ra = 1.6 μm) is used to smooth the temperature field in space, thereby outputting the result and marking the coordinates of the abnormal temperature rise, that is, locating the grid points (xj, yj, zj) that satisfy Tj > Talert. In this step, the L1 regularization optimization is a mathematical tool for stably reconstructing high-dimensional signals from underdetermined measurement data by imposing sparsity constraints. In the temperature monitoring of switchgear contacts, it transforms a small amount of sensor data into a high-resolution temperature field through the compressed sensing theory.

[0104] S500. Input the three-dimensional temperature gradient distribution and its historical time-series data into the intrinsic mode decomposition model for processing, extract the intrinsic mode components of the contact material fatigue characteristics, generate a dynamic adaptive warning threshold, and locate the coordinates of the abnormal temperature rise.

[0105] It is understandable that in this step, by inputting the three-dimensional temperature gradient distribution of the switchgear contact and its historical time-series data into the empirical mode decomposition model, the intrinsic mode functions characterizing the fatigue characteristics of the contact material are extracted by using the Hilbert-Huang transform, separating the long-term trend (material aging) and short-term fluctuations (arc ablation) in the temperature rise signal; and based on the IMF components, dynamic adaptive warning thresholds (such as temperature rise rate threshold, temperature gradient mutation threshold) are constructed, and combined with the contact spatial coordinate data to locate the abnormal temperature rise area (such as arc ablation point, poor contact point), realizing the accurate assessment of the switchgear contact state and fault warning. Compared with the traditional fixed threshold method, this step adapts to different load conditions (light load / heavy load / impact current) of the switchgear through dynamic thresholds, significantly reducing the false alarm rate (>60%), and supporting the sub-millimeter positioning of local overheating points of the contact (error <0.5mm), providing a high-reliability decision basis for the preventive maintenance of the switchgear.

[0106] Embodiment 2:

[0107] As Figure 2 shown, this embodiment provides a wireless temperature rise sensing system for switchgear contacts based on surface acoustic wave resonance. Refer to Figure 2 The system includes:

[0108] The first calculation module 701: used to collect the radio frequency signals reflected by the multi-modal surface acoustic wave resonator array etched on the surface of the moving / static contacts of the switchgear, separate the I / Q components through the quadrature phase-locked loop demodulation technology, and calculate the real-time offsets of the fundamental frequency and the third harmonic relative to the reference frequency to obtain the fundamental frequency offset and the third harmonic offset;

[0109] The solving module 702: used to input the third harmonic offset into the surface acoustic wave propagation equation, solve the equivalent acoustic impedance change corresponding to the thickness of the contact oxide film, and obtain the equivalent acoustic impedance change of the oxide film;

[0110] The second calculation module 703: used to combine the fundamental frequency offset and the equivalent acoustic impedance change of the oxide film, and use the thermo-acoustic coupling partial differential equation to compensate for the deformation of the surface acoustic wave propagation path caused by the thermal expansion of the contact material, and obtain the net fundamental frequency offset after temperature decoupling;

[0111] The reconstruction module 704: used to sparsely reconstruct the temperature field of the contact area according to the net fundamental frequency offset and the preset resonator spatial coordinate matrix by using the compressive sensing algorithm, and output the three-dimensional temperature gradient distribution of the contact area;

[0112] The processing module 705: used to input the three-dimensional temperature gradient distribution and its historical time-series data into the empirical mode decomposition model for processing, extract the intrinsic mode components of the contact material fatigue characteristics, generate dynamic adaptive warning thresholds and locate the abnormal temperature rise coordinates.

[0113] Specifically, the first calculation module 701 includes:

[0114] Incentive receiving unit: It is used to set the directional RF antenna inside the insulating sheath of the switchgear cabinet, etch a multimode surface acoustic wave resonator array on the moving / static contact surface, transmit a frequency-modulated continuous wave signal with a frequency band of 902 - 928 MHz, excite the resonator to generate fundamental frequency and third harmonic surface acoustic waves, and receive the reflected signal. The calculation formula is as follows:

[0115] S r (t) = A0cos(2πf0t + φ0) + A3cos(2πf3t + φ3) + n(t)

[0116] Wherein, A0 and A3 are the amplitudes of the fundamental frequency and third harmonic signals, φ0 and φ3 are the phase angles of the surface acoustic waves, n(t) is the electromagnetic noise inside the switchgear cabinet, and S r (t) is the reflected signal;

[0117] First calculation unit: It is used to input the reflected signal into the quadrature phase-locked loop, multiply it with the local oscillation signal through a mixer, and separate the in-phase and quadrature components. The calculation formula is as follows:

[0118] I(t) = LPF[S r (t)·cos(2πf c t)], Q(t) = PF[S r (t)·sin(2πf c t)]

[0119] Wherein, f c is the carrier center frequency, LPF is the low-pass filter, S r (t) is the reflected signal, I(t) is the in-phase signal component, Q(t) is the quadrature signal component, cos(2πf c t) and sin(2πf c t) are the quadrature reference signals generated by the local oscillator;

[0120] Second calculation unit: It is used to calculate the instantaneous phase angle based on the in-phase component and quadrature component of the fundamental frequency signal through the arctangent function. The instantaneous phase angle is the change in the propagation speed of the surface acoustic wave caused by the contact temperature rise, and perform iterative calculations on the in-phase component and quadrature component of the third harmonic signal to obtain the phase angle;

[0121] The third calculation unit: It is used to perform time differentiation on the instantaneous phase angle to obtain the instantaneous frequency deviation, and then through 10 ms time window integration and averaging to suppress the electromagnetic noise of the switch cabinet, output the smoothed fundamental frequency offset, and perform the same differentiation-integration operation on the phase angle, and then calculate the third harmonic offset. The amplitude of the third harmonic offset is non-linearly and positively correlated with the contact oxidation film thickness.

[0122] Specifically, the solving module 702 includes:

[0123] The extraction unit: It is used to extract the third harmonic frequency offset caused by the oxidation film on the contact surface to form a frequency offset data matrix;

[0124] The first establishment unit: It is used to establish the surface acoustic wave propagation equation based on the acoustic parameters of the contact material and the oxidation film. Its calculation formula is as follows:

[0125]

[0126] In the formula, K is the acoustic impedance coupling coefficient, ΔZ ox is the change in the equivalent acoustic impedance of the oxidation film, ρ ox , ρ Cu is the density of CuO and CuCr alloy, v ox , v Cu is the surface acoustic wave propagation velocity of CuO and CuCr alloy;

[0127] The second establishment unit: It is used to input the frequency offset data matrix into the surface acoustic wave propagation equation, establish the frequency offset - acoustic impedance relationship equation of each resonator at each time point, and solve the change in the equivalent acoustic impedance of the oxidation film by using the non-linear least squares method.

[0128] Specifically, the second calculation module 703 includes:

[0129] The first construction unit: It is used to obtain the fundamental frequency offset of the multimodal surface acoustic wave resonator array on the contact surface and the change in the equivalent acoustic impedance of the oxidation film, and construct the thermo-acoustic-mechanical coupling parameter matrix. Its calculation formula is as follows:

[0130] M i =[Δf 0,i , θZ ox，i , L 0，i

[0131] In the formula, L 0，i is the initial length of the surface acoustic wave propagation path of the i-th resonator, Δf 0，i is the fundamental frequency offset of the i-th resonator, ΔZ ox，i is the change in the equivalent acoustic impedance of the oxidation film corresponding to the i-th resonator;

[0132] ​The third establishment unit: used to establish a thermo-acoustic coupled partial differential equation based on the contact thermal expansion effect and the characteristics of surface acoustic wave propagation, and compensate for the interference of path deformation on the fundamental frequency offset;

[0133] The solving unit: used to numerically solve the thermo-acoustic coupled equation by using an adaptive unstructured finite element mesh, and output the net fundamental frequency offset after temperature decoupling. The solving process includes generating an unstructured mesh based on the surface roughness of the contact, updating the equivalent acoustic impedance change and the fundamental frequency offset of the oxide film every 10 ms, and real-time tracking the growth and temperature rise of the oxide film, so as to perform error control.

[0134] Specifically, the reconstruction module 704 includes:

[0135] The second construction unit: used to combine the net fundamental frequency offset with the resonator spatial coordinate matrix to construct a temperature sensitivity matrix, and its calculation formula is as follows:

[0136]

[0137] In the formula, N is the number of resonators, M is the number of discretized grid points in the contact area of the contact, p i =(x i , y i , z i ) is the spatial coordinate of the i-th resonator (calibrated by the switchgear contact design drawing), g j =(x j , y j , z j ) is the coordinate of the j-th temperature field grid point (grid resolution 0.5 mm), and λ is the thermal diffusion length;

[0138] The generation unit: used to construct a discrete cosine transform sparse basis matrix based on the statistical characteristics of the contact surface roughness, and combine it with the temperature sensitivity matrix to generate an observation matrix

[0139] The sensing unit: used to establish an L1-regularized optimization problem based on the observation matrix and the net fundamental frequency offset, minimize the weighted sum of the measurement data residual and the temperature field sparsity constraint, and use the iterative shrinkage threshold algorithm to alternately perform gradient descent update and soft threshold shrinkage to obtain the optimal sparse solution; thus perform an inverse DCT transform on the sparse solution and apply the temperature rise physical constraint to output the three-dimensional temperature gradient distribution of the contact area of the contact.

[0140] It should be noted that regarding the system in the above embodiments, the specific manners in which each module performs operations have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0141] Embodiment 3:

[0142] Corresponding to the above method embodiments, a wireless sensing device for the temperature rise of switch cabinet contacts with surface acoustic wave resonance is also provided in this embodiment. A wireless sensing device for the temperature rise of switch cabinet contacts with surface acoustic wave resonance described below can be correspondingly referred to with a wireless sensing method for the temperature rise of switch cabinet contacts with surface acoustic wave resonance described above.

[0143] Figure 3 It is a block diagram of a wireless sensing device 800 for the temperature rise of switch cabinet contacts with surface acoustic wave resonance shown according to an exemplary embodiment. As Figure 3 shown, the wireless sensing device 800 for the temperature rise of switch cabinet contacts with surface acoustic wave resonance includes: a processor 801 and a memory 802. The wireless sensing device 800 for the temperature rise of switch cabinet contacts with surface acoustic wave resonance further includes one or more of a multimedia component 803, an I / O interface 804, and a communication component 805.

[0144] Among them, the processor 801 is used to control the overall operation of the wireless sensor device 800 for the temperature rise of the switch cabinet contact with surface acoustic wave resonance, so as to complete all or part of the steps in the above-mentioned method for wirelessly sensing the temperature rise of the switch cabinet contact with surface acoustic wave resonance. The memory 802 is used to store various types of data to support the operation of the wireless sensor device 800 for the temperature rise of the switch cabinet contact with surface acoustic wave resonance. These data may include, for example, instructions for any application or method operating on the wireless sensor device 800 for the temperature rise of the switch cabinet contact with surface acoustic wave resonance, as well as application-related data, such as contact data, sent and received messages, pictures, audio, video, and so on. The memory 802 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read-Only Memory (EPROM), Programmable Read-Only Memory (PROM), Read-Only Memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. The multimedia component 803 may include a screen and an audio component. Among them, the screen can be, for example, a touch screen, and the audio component is used to output and / or input audio signals. For example, the audio component may include a microphone, and the microphone is used to receive external audio signals. The received audio signals can be further stored in the memory 802 or sent through the communication component 805. The audio component also includes at least one speaker for outputting audio signals. The I / O interface 804 provides an interface between the processor 801 and other interface modules, and the above-mentioned other interface modules can be a keyboard, a mouse or buttons, etc. These buttons can be virtual buttons or physical buttons. The communication component 805 is used for wired or wireless communication between the wireless sensor device 800 for the temperature rise of the switch cabinet contact with surface acoustic wave resonance and other devices. Wireless communication, such as Wi-Fi, Bluetooth, Near Field Communication (NFC), 2G, 3G or 4G, or a combination of one or more of them. Therefore, the corresponding communication component 805 may include: a Wi-Fi module, a Bluetooth module or an NFC module.

[0145] In an exemplary embodiment, the wireless temperature rise sensing device 800 for switchgear contacts based on surface acoustic wave resonance can be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), controllers, microcontrollers, microprocessors, or other electronic components, and is used to execute the above-mentioned wireless temperature rise sensing method for switchgear contacts based on surface acoustic wave resonance.

[0146] In another exemplary embodiment, there is also provided a computer-readable storage medium including program instructions, and when the program instructions are executed by a processor, the steps of the above-mentioned wireless temperature rise sensing method for switchgear contacts based on surface acoustic wave resonance are implemented. For example, the computer-readable storage medium can be the above-mentioned memory 802 including program instructions, and the above-mentioned program instructions can be executed by the processor 801 of the wireless temperature rise sensing device 800 for switchgear contacts based on surface acoustic wave resonance to complete the above-mentioned wireless temperature rise sensing method for switchgear contacts based on surface acoustic wave resonance.

[0147] Embodiment 4:

[0148] Corresponding to the above method embodiment, in this embodiment, there is also provided a readable storage medium, and a readable storage medium described below can be correspondingly referred to with a wireless temperature rise sensing method for switchgear contacts based on surface acoustic wave resonance described above.

[0149] A computer program is stored on the readable storage medium, and when the computer program is executed by a processor, the steps of the wireless temperature rise sensing method for switchgear contacts based on surface acoustic wave resonance in the above method embodiment are implemented.

[0150] The readable storage medium can specifically be various readable storage media such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disc that can store program codes.

[0151] The present invention adopts a multi-modal surface acoustic wave resonator array and combines an orthogonal phase-locked loop dual-frequency demodulation technique to synchronously extract the fundamental frequency temperature rise signal and the third harmonic oxide film thickness feature; by constructing a thermo-acoustic coupling partial differential equation to compensate for the interference of the thermal expansion deformation of the contact on the propagation path of the surface acoustic wave, the accurate decoupling of the temperature rise and the oxide film effect is realized; further, the compressive sensing algorithm is used to perform frequency-domain sparse reconstruction on the sparse sensor data, and the three-dimensional temperature gradient distribution (with a resolution of 0.5 mm) of the contact area is output, and the dynamic adaptive warning threshold is generated by combining the empirical mode decomposition, breaking through the limitation of traditional single-point temperature measurement, realizing passive wireless, high-precision (±0.8 °C), full-space temperature rise monitoring in a strong electromagnetic interference environment, directly driving the intelligent operation and maintenance decision-making of the switch cabinet, and solving the core pain points of poor anti-interference performance, multi-parameter coupling and insufficient spatial resolution in the prior art.

[0152] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0153] As mentioned above, this is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present invention, and all of them should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for wirelessly sensing the temperature rise of switch cabinet contacts based on surface acoustic wave resonance, characterized in that: include: Collect the RF signal reflected by the multi-mode surface acoustic wave resonator array etched on the surface of the moving / static contact of the switch cabinet, separate the I / Q components through the orthogonal phase-locked loop demodulation technology, calculate the real-time offset of the fundamental frequency and the third harmonic relative to the reference frequency, and obtain the fundamental frequency offset and the third harmonic offset; The third harmonic offset is input into the surface acoustic wave propagation equation, and the equivalent acoustic impedance change corresponding to the contact oxide film thickness is solved to obtain the equivalent acoustic impedance change of the oxide film; Combining the fundamental frequency offset and the change in the equivalent acoustic impedance of the oxide film, the thermal-acoustic coupling partial differential equation is used to compensate for the deformation of the surface acoustic wave propagation path caused by the thermal expansion of the contact material, and the net fundamental frequency offset after temperature decoupling is obtained. According to the net offset of the fundamental frequency and the preset resonator space coordinate matrix, the temperature field of the contact area is sparsely reconstructed using the compressed sensing algorithm to output the three-dimensional temperature gradient distribution of the contact area. The three-dimensional temperature gradient distribution and its historical time series data are input into the intrinsic mode decomposition model for processing, the intrinsic mode components of the contact material fatigue characteristics are extracted, the dynamic adaptive warning threshold is generated, and the abnormal temperature rise coordinates are located.

2. The method for wirelessly sensing the temperature rise of switch cabinet contacts based on surface acoustic wave resonance according to claim 1 is characterized in that: The method collects the radio frequency signal reflected by the multi-mode surface acoustic wave resonator array etched on the surface of the moving / static contact of the switch cabinet, separates the I / Q components through the orthogonal phase-locked loop demodulation technology, calculates the real-time offset of the fundamental frequency and the third harmonic relative to the reference frequency, and obtains the fundamental frequency offset and the third harmonic offset, which include: The directional RF antenna is set inside the insulating sheath of the switch cabinet, and a multi-mode surface acoustic wave resonator array is etched on the contact surface of the moving / static contact. The frequency modulated continuous wave signal with a frequency range of 902-928MHz is transmitted to excite the resonator to generate the fundamental frequency and third harmonic surface acoustic waves, and receive the reflected signal. The calculation formula is as follows: S r (t)=A0cos(2πf0t+φ0)+A3cos(2πf3t+φ3)+n(t) Where A0 and A3 are the amplitudes of the fundamental frequency and the third harmonic signal, φ0 and φ3 are the phase angles of the surface acoustic wave, n(t) is the electromagnetic noise in the switch cabinet, S r (t) is the reflected signal; The reflected signal is input into the orthogonal phase-locked loop and multiplied by the local oscillation signal through the mixer to separate the in-phase and quadrature components. The calculation formula is as follows: I(t)=LPF[S r (t)·cos(2πf c t)],Q(t)=LPF[S r (t)·sin(2πf c t)] In the formula, f c is the carrier center frequency, LPF is the low-pass filter, S r (t) is the reflected signal, I(t) is the in-phase signal component, Q(t) is the quadrature signal component, cos(2πf c t) and sin(2πf c t) is an orthogonal reference signal generated by a local oscillator; Based on the in-phase component and quadrature component of the fundamental frequency signal, the instantaneous phase angle is calculated by the inverse tangent function, where the instantaneous phase angle is the change in the propagation velocity of the surface acoustic wave caused by the temperature rise of the contact. The in-phase component and quadrature component of the third harmonic signal are iteratively calculated to obtain the phase angle; The instantaneous phase angle is differentiated in time to obtain the instantaneous frequency deviation, which is then integrated and averaged through a 10ms time window to suppress the electromagnetic noise of the switch cabinet, and the smoothed fundamental frequency offset is output. The same differentiation-integration operation is performed on the phase angle to calculate the third harmonic offset, where the amplitude of the third harmonic offset is nonlinearly positively correlated with the thickness of the contact oxide film.

3. The method for wirelessly sensing the temperature rise of switch cabinet contacts based on surface acoustic wave resonance according to claim 1 is characterized in that: The third harmonic offset is input into the surface acoustic wave propagation equation to solve the equivalent acoustic impedance change corresponding to the contact oxide film thickness to obtain the equivalent acoustic impedance change of the oxide film, which includes: Extract the third harmonic frequency offset caused by the oxide film on the contact surface to form a frequency deviation data matrix; Based on the acoustic parameters of the contact material and the oxide film, the surface acoustic wave propagation equation is established, and its calculation formula is as follows: Where K is the acoustic impedance coupling coefficient, ΔZ ox is the change in equivalent acoustic impedance of the oxide film, ρ ox , ρC u is the density of CuO and CuCr alloy, υ ox , Cu is the surface acoustic wave propagation velocity of CuO and CuCr alloy; The frequency deviation data matrix is ​​input into the surface acoustic wave propagation equation, and the frequency deviation-acoustic impedance relationship equation of each resonator at each time point is established. The nonlinear least squares method is used to solve the change of the equivalent acoustic impedance of the oxide film.

4. The method for wirelessly sensing the temperature rise of switch cabinet contacts based on surface acoustic wave resonance according to claim 1 is characterized in that: The fundamental frequency offset and the equivalent acoustic impedance change of the oxide film are combined, and the deformation of the surface acoustic wave propagation path caused by the thermal expansion of the contact material is compensated by the thermal-acoustic coupling partial differential equation to obtain the net fundamental frequency offset after temperature decoupling, which includes: The fundamental frequency offset of the multi-modal surface acoustic wave resonator array on the contact surface and the change in the equivalent acoustic impedance of the oxide film are obtained, and the thermal-acoustic-mechanical coupling parameter matrix is ​​constructed. The calculation formula is as follows: M i =[Δf 0,i ,ΔZ ox，i ,L 0，i ] Where, L 0，i is the initial length of the surface acoustic wave propagation path of the i-th resonator, Δ f0，i is the fundamental frequency offset of the i-th resonator, ΔZ ox，i is the change in equivalent acoustic impedance of the oxide film corresponding to the i-th resonator; Based on the thermal expansion effect of the contact and the propagation characteristics of surface acoustic waves, a thermal-acoustic coupling partial differential equation is established to compensate for the interference of path deformation on the fundamental frequency offset; An adaptive unstructured finite element mesh is used to numerically solve the thermal-acoustic coupling equation, and the net offset of the fundamental frequency after temperature decoupling is output. The solution process includes generating an unstructured mesh based on the contact surface roughness, updating the change in the equivalent acoustic impedance of the oxide film and the fundamental frequency offset every 10 ms, and tracking the oxide film growth and temperature rise in real time to perform error control.

5. The method for wirelessly sensing the temperature rise of switch cabinet contacts based on surface acoustic wave resonance according to claim 1 is characterized in that: According to the net offset of the fundamental frequency and the preset resonator space coordinate matrix, the temperature field of the contact area of ​​the contact is sparsely reconstructed using a compressed sensing algorithm to output a three-dimensional temperature gradient distribution of the contact area, including: The net fundamental frequency offset is combined with the resonator space coordinate matrix to construct the temperature sensitivity matrix, which is calculated as follows: Where N is the number of resonators, M is the number of discretized grid points in the contact area, and pi = (x i ,y i , z i ) is the spatial coordinate of the i-th resonator (calibrated by the switch cabinet contact design drawing), g j =(x j ,y j , z j ) is the coordinate of the jth temperature field grid point (grid resolution 0.5 mm), λ is the heat diffusion length; Based on the statistical characteristics of contact surface roughness, a discrete cosine transform sparse basis matrix is ​​constructed and combined with the temperature sensitivity matrix to generate the observation matrix An L1 regularized optimization problem is established based on the observation matrix and the net offset of the fundamental frequency. The weighted sum of the measurement data residual and the sparsity constraint of the temperature field is minimized. The iterative shrinkage threshold algorithm is used to alternately perform gradient descent update and soft threshold shrinkage to obtain the optimal sparse solution. The sparse solution is then inversely transformed into a DCT and the temperature rise physical constraint is imposed to output the three-dimensional temperature gradient distribution of the contact area.

6. A surface acoustic wave resonance switch cabinet contact temperature rise wireless sensing system, based on the surface acoustic wave resonance switch cabinet contact temperature rise wireless sensing method according to claim 1, characterized in that: include: The first calculation module is used to collect the radio frequency signal reflected by the multi-modal surface acoustic wave resonator array etched on the surface of the moving / static contact of the switch cabinet, separate the I / Q components through the orthogonal phase-locked loop demodulation technology, calculate the real-time offset of the fundamental frequency and the third harmonic relative to the reference frequency, and obtain the fundamental frequency offset and the third harmonic offset; Solving module: used to input the third harmonic offset into the surface acoustic wave propagation equation, solve the equivalent acoustic impedance change corresponding to the thickness of the contact oxide film, and obtain the equivalent acoustic impedance change of the oxide film; The second calculation module is used to combine the fundamental frequency offset and the change in the equivalent acoustic impedance of the oxide film, and use the thermal-acoustic coupling partial differential equation to compensate for the deformation of the surface acoustic wave propagation path caused by the thermal expansion of the contact material to obtain the net fundamental frequency offset after temperature decoupling; Reconstruction module: used to sparsely reconstruct the temperature field of the contact area of ​​the contact using a compressed sensing algorithm according to the net offset of the fundamental frequency and the preset resonator space coordinate matrix, and output the three-dimensional temperature gradient distribution of the contact area; Processing module: used to input the three-dimensional temperature gradient distribution and its historical time series data into the intrinsic mode decomposition model for processing, extract the intrinsic mode components of the contact material fatigue characteristics, generate dynamic adaptive warning thresholds and locate the abnormal temperature rise coordinates.

7. The surface acoustic wave resonance switch cabinet contact temperature rise wireless sensing system according to claim 6, characterized in that: The first computing module includes: Excitation receiving unit: used to set the directional RF antenna inside the insulating sheath of the switch cabinet, etch a multi-mode surface acoustic wave resonator array on the contact surface of the moving / static contact, transmit a frequency modulated continuous wave signal with a frequency range of 902-928MHz, excite the resonator to generate the fundamental frequency and third harmonic surface acoustic waves, and receive the reflected signal. The calculation formula is as follows: S r (t)=A0cos(2πf0t+φ0)+A3cos(2πf3t+φ3)+n(t) Where A0 and A3 are the amplitudes of the fundamental frequency and the third harmonic signal, φ0 and φ3 are the phase angles of the surface acoustic wave, n(t) is the electromagnetic noise in the switch cabinet, S r (t) is the reflected signal; The first calculation unit is used to input the reflected signal into the orthogonal phase-locked loop, multiply it with the local oscillation signal through the mixer, and separate the in-phase and quadrature components. The calculation formula is as follows: I(t)=LPF[S r (t)·cos(2πf c t),Q(t)=LPF[S r (t)·sin(2πf c t)] In the formula, f c is the carrier center frequency, LPF is the low-pass filter, S r (t) is the reflected signal, I(t) is the in-phase signal component, Q(t) is the quadrature signal component, cos(2πf c t) and sin(2πf c t) is an orthogonal reference signal generated by a local oscillator; The second calculation unit is used to calculate the instantaneous phase angle of the in-phase component and the orthogonal component of the fundamental frequency signal through an inverse tangent function, wherein the instantaneous phase angle is the change in the propagation velocity of the surface acoustic wave caused by the temperature rise of the contact, and iteratively calculate the in-phase component and the orthogonal component of the third harmonic signal to obtain the phase angle; The third calculation unit is used to perform time differentiation on the instantaneous phase angle, obtain the instantaneous frequency deviation, and then integrate and average through a 10ms time window to suppress the electromagnetic noise of the switch cabinet, output the smoothed fundamental frequency offset, and perform the same differentiation-integration operation on the phase angle, and then calculate the third harmonic offset, where the amplitude of the third harmonic offset is nonlinearly positively correlated with the thickness of the contact oxide film.

8. The surface acoustic wave resonance switch cabinet contact temperature rise wireless sensing system according to claim 6, characterized in that: The solution module includes: Extraction unit: used to extract the third harmonic frequency offset caused by the oxide film on the contact surface to form a frequency deviation data matrix; The first establishment unit is used to establish the surface acoustic wave propagation equation based on the acoustic parameters of the contact material and the oxide film. The calculation formula is as follows: Where K is the acoustic impedance coupling coefficient, ΔZ ox is the change in equivalent acoustic impedance of the oxide film, ρ ox , ρ Cu is the density of CuO and CuCr alloy, v ox , v Cu is the surface acoustic wave propagation velocity of CuO and CuCr alloy; The second establishment unit is used to input the frequency deviation data matrix into the surface acoustic wave propagation equation, establish the frequency deviation-acoustic impedance relationship equation of each resonator at each time point, and use the nonlinear least squares method to solve the change of the equivalent acoustic impedance of the oxide film.

9. The surface acoustic wave resonance switch cabinet contact temperature rise wireless sensing system according to claim 6, characterized in that: The second computing module includes: The first construction unit is used to obtain the fundamental frequency offset of the multi-modal surface acoustic wave resonator array on the contact surface and the change in the equivalent acoustic impedance of the oxide film, and to construct the thermal-acoustic-mechanical coupling parameter matrix. The calculation formula is as follows: M i =[Δf 0，i ,ΔZ ox，i ,L 0，i ] Where, L 0，i is the initial length of the surface acoustic wave propagation path of the i-th resonator, Δf 0，i is the fundamental frequency offset of the i-th resonator, ΔX ox，i is the change in equivalent acoustic impedance of the oxide film corresponding to the i-th resonator; The third establishment unit is used to establish a thermal-acoustic coupling partial differential equation based on the contact thermal expansion effect and the propagation characteristics of the surface acoustic wave, and compensate for the interference of the path deformation on the fundamental frequency offset; Solving unit: It is used to numerically solve the thermal-acoustic coupling equation using an adaptive unstructured finite element grid and output the net offset of the fundamental frequency after temperature decoupling. The solving process includes generating an unstructured grid based on the surface roughness of the contact, updating the change in the equivalent acoustic impedance of the oxide film and the fundamental frequency offset every 10ms, and tracking the growth and temperature rise of the oxide film in real time to perform error control.

10. The surface acoustic wave resonance switch cabinet contact temperature rise wireless sensing system according to claim 6, characterized in that: The reconstruction module includes: The second construction unit is used to combine the net fundamental frequency offset with the resonator space coordinate matrix to construct a temperature sensitivity matrix, and its calculation formula is as follows: Where N is the number of resonators, M is the number of discretized grid points in the contact area, and p i =(x i ,y i , z i ) is the spatial coordinate of the i-th resonator (calibrated by the switch cabinet contact design drawing), g j =(x j ,y j , z j ) is the coordinate of the jth temperature field grid point (grid resolution 0.5 mm), λ is the heat diffusion length; Generation unit: used to construct a discrete cosine transform sparse basis matrix based on the statistical characteristics of the contact surface roughness, and combine it with the temperature sensitivity matrix to generate the observation matrix Perception unit: used to establish an L1 regularized optimization problem based on the observation matrix and the net offset of the fundamental frequency, minimize the weighted sum of the measurement data residual and the sparsity constraint of the temperature field, and use an iterative shrinkage threshold algorithm to alternately perform gradient descent updates and soft threshold shrinkage to obtain the optimal sparse solution; thereby performing an inverse DCT transform on the sparse solution and applying a temperature rise physical constraint to output the three-dimensional temperature gradient distribution of the contact area.

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