A time-frequency electromagnetic hybrid excitation high-power transmitting method and system

Abstract

The application provides a time-frequency electromagnetic hybrid excitation high-power emission method and system, which comprises the following steps: using pseudo-random coding technology to spread spectrum and recombine a frequency domain multi-frequency waveform and a time domain bipolar square wave generated in parallel to obtain a composite excitation sequence, so as to output a time-frequency hybrid voltage waveform with high power; synchronously collecting transient voltage signals and transient current signals at both ends of a current emission loop, calculating a compensation capacitance value, and connecting a capacitor group matched with the compensation capacitance value; using a Kalman filtering algorithm to dynamically and optimally estimate an electrode contact state in a closed loop, so as to obtain a pushing force estimation value to dynamically adjust a pushing execution mechanism to make an electrode array closely adhere to a well wall; controlling the on-off and polarity of a specific azimuth electrode, generating a focused electromagnetic field in a stratum, and performing three-dimensional scanning; when it is detected that current attenuation is greater than an attenuation threshold or contact force is suddenly changed, returning to re-perform capacitor switching or starting force position control until scanning is completed. The application can realize deep high-frequency signal emission and improve deep hole detection efficiency.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic exploration technology, and in particular to a high-power transmission method and system for time-frequency electromagnetic hybrid excitation. Background Technology

[0002] With the increasing depletion of shallow mineral resources, global mineral resource exploration has fully entered the "deep earth" era. Deep mineral deposits, due to their extremely deep spatial locations (typically exceeding 1000 meters or even 3000 meters) and highly complex geological structures, present exceptionally difficult challenges for electromagnetic excitation, resulting in extremely weak target anomaly responses. In such extreme deep environments, extremely high technical thresholds are imposed on geophysical exploration equipment. Electromagnetic methods, as a core technology for exploring deep metal mines, groundwater, and oil and gas resources, rely on the electromagnetic wave transmitting system's output power, signal spectrum richness, and ability to couple large currents into complex strata for their detection depth, resolution, and accuracy.

[0003] In traditional deep mineral exploration, time-domain electromagnetic (TDEM) and frequency-domain electromagnetic (FTEM) methods are generally considered two distinct technical approaches. TDEM measures the secondary field attenuation curve of strata by emitting high-power step pulse signals, making it particularly sensitive to highly conductive ore bodies. FTEM, on the other hand, measures amplitude and phase parameters by emitting multiple consecutive harmonic signals of different frequencies, offering advantages in fine strata layering and high-resistivity target detection. However, existing equipment typically only supports a single operating mode, requiring explorers to use different instruments or perform scans in stages. This not only results in extremely cumbersome field procedures and low exploration efficiency, but the time difference between measurements also makes accurate joint constraint interpretation of the data during inversion.

[0004] Even more challenging is the fact that when conducting electromagnetic exploration at depths of up to 3000 meters, the instrument faces stringent physical limitations. The surface control system is connected to the downhole transmitter via a 3000-meter-long armored logging cable, which possesses a massive parasitic distributed inductance in the tens of millihenries. When transmitting time-frequency signals containing mid-to-high frequency components (e.g., ≤300Hz), this extreme parasitic inductance causes a sharp increase in system impedance, resulting in severe distortion and attenuation of the high-frequency signal. Traditional transmitters simply cannot maintain a high current output under these conditions; the transmission current often drops to tens of amperes or even lower, making it difficult to achieve the design specifications of a transmission current ≥100A and a comprehensive transmission power ≥160W to effectively excite the formation. Furthermore, downhole temperatures are often ≥85℃, ambient pressure ≥50MPa, and the drilling mud is viscous. Traditional mechanical pushing results in extremely high contact resistance between the electrodes and the formation, causing omnidirectional scattering of electromagnetic energy and extremely low energy utilization, making it difficult to achieve directional focusing detection of concealed ore bodies. Therefore, a completely new system and method are urgently needed to overcome these numerous physical and engineering bottlenecks. Summary of the Invention

[0005] Therefore, it is necessary to provide a time-frequency electromagnetic hybrid excitation high-power transmission method and system to address the above-mentioned technical problems.

[0006] A high-power transmission method using time-frequency electromagnetic hybrid excitation includes the following steps: S1: Generating frequency-domain multi-frequency waveforms and time-domain bipolar square waves in parallel using digital frequency synthesis technology, and using pseudo-random coding technology for spread spectrum recombination to generate a composite excitation sequence, and outputting a high-power time-frequency hybrid voltage waveform according to the composite excitation sequence; S2: Using an adaptive impedance matching algorithm to extract the phase difference between voltage and current, dynamically calculating the theoretical compensation capacitive reactance value, matching the corresponding capacitor bank to achieve series resonance; S3: Using a Kalman filter algorithm to perform closed-loop dynamic optimal estimation of the electrode contact state, obtaining the push force estimate, and dynamically adjusting the push actuator according to the push force estimate to achieve a preset optimal stable coupling between the electrode array and the wellbore; S4: Controlling the on / off state and polarity of electrodes in a specific orientation to generate a focused electromagnetic field in the formation and perform three-dimensional scanning; S5: Real-time monitoring of the data transmission status between the surface and the wellbore, when the current attenuation is detected to be greater than the attenuation threshold, returning to step S2 to re-switch the capacitors, and when a sudden change in contact force is detected, returning to step S3 to restart force-position control until the scanning is completed.

[0007] In one embodiment, step S1 includes: acquiring the three-dimensional spatial characteristics of the deep ore body to be measured, the electrical characteristics of the surrounding rock, and the target detection depth parameters; calculating the time-domain excitation parameters and the frequency-domain excitation parameters; setting the time-domain signal characteristics according to the time-domain excitation parameters to obtain a time-domain bipolar square wave with a specific duty cycle; setting the frequency-domain signal characteristics according to the frequency-domain excitation parameters to obtain a multi-frequency superimposed waveform containing the fundamental frequency and its harmonic components at a frequency less than or equal to the set frequency, i.e., a frequency-domain multi-frequency waveform. S f ( t ),for: ; In the formula, A n For amplitude, f n For frequency and f n ≤300Hz φ n The initial phase is defined as follows: Based on pseudo-random coding technology, the time-domain bipolar square wave and the frequency-domain multi-frequency waveform are modulated and synthesized to generate a composite excitation sequence, which is: ; In the formula, S t (t) represents a time-domain bipolar square wave. P(t) is a pseudo-random sequence, and α and β are the power allocation weighting coefficients of the time-domain and frequency-domain signals, respectively; the composite excitation sequence is used as the driving signal and is inverted by a high voltage to output a high-power time-frequency hybrid voltage waveform.

[0008] In one embodiment, step S2 includes: synchronously acquiring transient voltage and transient current signals at both ends of the current transmitting circuit in real time; extracting the fundamental and main harmonic components of the transient voltage and transient current signals using fast Fourier transform, and calculating the phase difference between them at each characteristic frequency point; and dynamically calculating the equivalent parasitic reactance value based on the phase difference. L eq (f) ,for: ; In the formula, V rms For effective voltage, I rms For the effective current, Δ θ ( f ) is at the characteristic frequency f The phase difference is calculated; with a power factor of approximately 1 as the target, the theoretical compensation capacitive reactance is calculated. ,for: ; The LC resonant array switch board is driven to operate according to the compensation capacitive reactance value, and the matched capacitor group is connected in series to the main circuit to realize the long cable series resonance, so that the excitation current emitted into the deep strata is greater than or equal to the excitation current threshold.

[0009] In one embodiment, step S3 includes: setting the system state vector as X. k = [x k , v k , F k ] T , where x k For displacement, v k For velocity, F k For the pushing force; based on the system state vector, a discretized state prediction equation and a covariance prediction equation are constructed as follows: ; ; In the formula, represents the current state result predicted at time k-1, A is the state transition matrix, represents the optimal value at time k-1, B is the control input matrix, and U... k-1 W is the control vector at time k-1. k Let A be the process noise, let be the system covariance matrix at time k, and let be the system covariance matrix at time k-1. TLet A be the transpose of A, and Q be the process noise covariance; the observation vector Z is obtained through sensors. k = [z x ,k, zF,k] T Calculate the Kalman gain: ; In the formula, K k H is the Kalman gain, and H is the prediction matrix of the object. T Let H be the transpose of H, and R be the covariance matrix of the object measurement noise; execute the state update equation and the covariance update equation to obtain the optimal push force estimate: ; ; In the formula, is the optimal estimate of the state variable at time k, and Z is... k Let be the measured value of the object, be the covariance matrix at time k, and I be the identity matrix; the input control of the pushing actuator is dynamically adjusted according to the estimated pushing force value so that the electrode array and the well wall achieve a preset optimal stable coupling.

[0010] In one embodiment, step S4 includes: controlling a specific azimuth electrode group in a multi-layer array electrode as the positive and negative electrodes for emission according to the ground scanning sequence, generating a focused electromagnetic field in the stratum, and performing electron switching scans at different azimuth angles to simultaneously inject transient step and multi-frequency steady-state energy into the surrounding rock.

[0011] A time-frequency electromagnetic hybrid excitation high-power transmission system is disclosed to implement the time-frequency electromagnetic hybrid excitation high-power transmission method described above. The system includes: a ground control and power supply system, a deep-well long-conductor transmission subsystem, an adaptive impedance matching subsystem, and a downhole high-power transmission subsystem. The ground control and power supply system is configured on the ground and includes a high-power power supply module, a main control computer, and a synchronous clock module. The high-power power supply module provides a DC high-voltage power supply. The main control computer issues encoding instructions for the time-frequency hybrid signal, transmission frequency parameters, and duty cycle parameters, and monitors the downhole operating status in real time. The synchronous clock module... A dual-mode synchronization mechanism using BeiDou / GPS and a temperature-controlled crystal oscillator (OCXO) is employed to synchronize the time between the transmitter and receiver. The deep-well long-wire transmission subsystem connects the ground control and power supply system to the downhole high-power transmission subsystem for data transmission between the ground and the downhole. The adaptive impedance matching subsystem is connected in series between the deep-well long-wire transmission subsystem and the downhole high-power transmission subsystem, or integrated within the downhole high-power transmission subsystem. It includes a phase detection circuit, an LC resonant array switch board, and a microprocessor control core. The microprocessor control core dynamically calculates the phase difference data fed back from the voltage and current phase detection circuit. The current inductive reactance of the deep well long wire transmission subsystem is calculated, and the matching capacitor array is automatically switched via a solid-state relay array to ensure that the capacitive reactance of the matching capacitor and the inductive reactance of the long wire form a series resonance, satisfying the resonance condition. The downhole high-power transmission subsystem is located at the bottom of the deep well or in the target detection layer, and includes a high-voltage inverter drive module, an FPGA time-frequency mixed signal generation module, a Kalman force-potential mixed control module, and a multi-layer array-type push electrode group. The high-voltage inverter drive module adopts a full-bridge inverter topology based on GaN gallium nitride switching transistors, receives digital control signals from the FPGA time-frequency mixed signal generation module, and inverts the DC high voltage into a time-frequency mixed signal. The system employs a high-power electromagnetic excitation signal; the multi-layer array-type push electrode group is arranged around the outer wall of the launch probe and includes multiple independently controlled azimuth electrode plates; the Kalman force-position hybrid control module includes a hydraulic or motor push actuator, a pressure sensor, and a displacement sensor. The pressure sensor and displacement sensor collect the contact state between the electrode and the well wall in real time, and the Kalman filter algorithm is used to estimate the optimal state of the contact pressure. The output control signal drives the push actuator, so that the multi-layer array-type push electrode group is tightly attached to the well wall with a set contact force. By controlling the current on / off and polarity combination of different azimuth electrode plates, focused power transmission is achieved.

[0012] In one embodiment, the deep well long conductor transmission subsystem includes a high-voltage power core for power transmission and a communication twisted pair for data transmission.

[0013] In one embodiment, the LC resonant array switch board integrates a high-voltage thin-film capacitor matrix arranged with binary weights, and a corresponding high-power contactless solid-state relay or bidirectional thyristor array.

[0014] In one embodiment, the FPGA time-frequency mixed signal generation module integrates multiple DDSs, which generate multi-frequency superimposed waveforms of the fundamental frequency and its multiple harmonic components in parallel, and spread and time-reassemble them through a pseudo-random sequence. The pseudo-random sequence adopts the maximum length sequence so that the energy of the mixed signal is evenly distributed within a set wide frequency band.

[0015] In one embodiment, the multi-layer array push electrode group adopts at least three layers, each layer containing four independent electrode plates evenly distributed on the circumference, for a total of 12 independent electrodes. Each independent electrode plate is connected to the output terminal of the high-voltage inverter drive module through a built-in withstand voltage relay matrix. Under the control of FPGA instructions, it can perform 360-degree electronic scanning switching to generate a focused electromagnetic field in the formation.

[0016] Compared with existing technologies, the advantages and beneficial effects of this invention are as follows: It improves data acquisition efficiency and accuracy by generating frequency-domain multi-frequency waveforms and time-domain bipolar square waves in parallel using digital frequency synthesis technology; it generates composite excitation sequences through spread spectrum recombination using pseudo-random coding technology, and outputs high-power time-frequency hybrid voltage waveforms to ensure absolute time synchronization and spatial homogeneity of geophysical response data in both time and frequency domains; it synchronously acquires transient voltage and current signals at both ends of the current transmitting circuit, calculates the compensation capacitive reactance value, and connects a matching capacitor bank based on the compensation capacitive reactance value to achieve long cable series resonance, solving the problem of high-frequency attenuation of long conductors in deep wells, widening the physical transmission bandwidth of long cables, and greatly reducing waveform nonlinear distortion; it also employs a card... The Mann filter algorithm performs closed-loop dynamic optimal estimation of the contact state between the electrode and the wellbore, obtains the estimated pushing force, and dynamically adjusts the pushing actuator based on the estimated pushing force, so that the electrode array and the wellbore achieve a preset optimal stable coupling, which greatly improves the electromagnetic energy coupling efficiency in complex heterogeneous rock interfaces. It controls the on / off state and polarity of electrodes in specific orientations to generate a focused electromagnetic field in the formation and perform three-dimensional scanning, improving the three-dimensional scanning accuracy of various orientations in deep wells. It monitors the data transmission status between the surface and the well in real time. When the current attenuation is detected to be greater than the attenuation threshold, it returns to re-switching the capacitor. When a sudden change in contact force is detected, it returns to restart the force-position control until the scanning is completed, ensuring the reliability and stability of deep geological exploration. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a high-power transmission method using time-frequency electromagnetic hybrid excitation in one embodiment.

[0018] Figure 2 This is a schematic diagram of the structure of a high-power transmission system with time-frequency electromagnetic hybrid excitation in one embodiment. Detailed Implementation

[0019] Having introduced the overall concept of the present invention, to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0020] In one embodiment, such as Figure 1 As shown, a high-power transmission method using time-frequency electromagnetic hybrid excitation is provided, comprising the following steps: Step S110: A frequency-domain multi-frequency waveform and a time-domain bipolar square wave are generated in parallel using digital frequency synthesis technology, and a composite excitation sequence is generated by spreading and recombination using pseudo-random coding technology. A high-power time-frequency hybrid voltage waveform is output based on the composite excitation sequence.

[0021] Specifically, digital frequency synthesis technology is used to generate frequency domain multi-frequency waveforms and time domain bipolar square waves. The time domain bipolar square wave signal can excite secondary attenuation in the time domain deep underground, and detect geological anomalies such as highly conductive massive sulfide ore bodies. The frequency domain multi-frequency waveform signal can utilize discrete multi-frequency harmonics distributed in different frequency bands to achieve fine resistivity sounding and high-resistivity target body resolution in the strata by measuring amplitude and phase response.

[0022] Because random fluctuations occur during the synthesis of frequency-domain multi-frequency waveforms and time-domain bipolar square waves, the peak factor and peak-to-average power ratio of the signal increase significantly. Therefore, pseudo-random coding technology is used to generate a spread-spectrum pseudo-random sequence. This pseudo-random sequence is used to perform phase flipping and spectrum shifting on the composite waveform after the superposition of the frequency-domain multi-frequency waveform and the time-domain bipolar square wave, so that the peak energy can be evenly distributed. This broadband digital sequence is smoothly converted into an analog reference control signal by a digital-to-analog converter with extremely low delay and ultra-high sampling rate, and then directly sent to the gate drive circuit of the high-voltage inverter drive module, thereby guiding the ultra-high voltage DC power supply to achieve high-current hybrid power amplification and output.

[0023] Step S110 includes: acquiring the three-dimensional spatial characteristics of the deep ore body to be measured, the electrical characteristics of the surrounding rock, and the target detection depth parameters; calculating the time-domain excitation parameters and the frequency-domain excitation parameters; setting the time-domain signal characteristics according to the time-domain excitation parameters to obtain a time-domain bipolar square wave with a specific duty cycle; setting the frequency-domain signal characteristics according to the frequency-domain excitation parameters to obtain a multi-frequency superimposed waveform containing the fundamental frequency and its harmonic components at frequencies less than or equal to the set frequencies, i.e., a frequency-domain multi-frequency waveform. S f (t ),for: ; In the formula, A n For amplitude, f n For frequency and f n ≤300Hz φ n The initial phase is defined as follows: Based on pseudo-random coding technology, the time-domain bipolar square wave and the frequency-domain multi-frequency waveform are modulated and synthesized to generate a composite excitation sequence, which is: ; In the formula, S t (t) represents a time-domain bipolar square wave. P (t) is a pseudo-random sequence, and α and β are the power allocation weighting coefficients of the time-domain and frequency-domain signals, respectively; the composite excitation sequence is used as the driving signal and is inverted by a high voltage to output a high-power time-frequency hybrid voltage waveform.

[0024] Specifically, based on the three-dimensional spatial characteristics of the deep ore body to be measured, the electrical characteristics of the surrounding rock, and the target detection depth parameters, the time-domain and frequency-domain excitation parameters required for the current detection task are calculated and set. The time-domain signal characteristics are set as a bipolar square wave with a specific duty cycle, and the frequency-domain signal characteristics are set as a multi-frequency superimposed waveform of ≤300Hz containing the fundamental frequency and its harmonic components. Based on pseudo-random coding technology, the time-domain square wave signal and the frequency-domain multi-frequency waveform are modulated and synthesized to generate a composite excitation sequence. This avoids the direct superposition of time-domain and frequency-domain signals, which would lead to spike waveforms and ensure the safety of power devices. The generated composite excitation sequence is used as a driving signal and input to the high-voltage inverter drive module for high-voltage inversion, outputting a high-power time-frequency hybrid voltage waveform, which improves the efficiency of subsequent exploration.

[0025] Step S120: Synchronously acquire transient voltage and transient current signals at both ends of the current transmitting circuit, calculate the compensation capacitive reactance value, and connect a matching capacitor bank according to the compensation capacitive reactance value to achieve long cable series resonance.

[0026] Specifically, since deep well electromagnetic detection requires very long logging cables, impedance characteristics are generated when transmitting high-power signals, making it difficult for the transmitted current to effectively penetrate the well wall and inject into the deep formation at high frequencies. Therefore, the transient voltage and transient current signals at both ends of the current transmission circuit are synchronously acquired, and the required compensation capacitive reactance value under the current frequency and inductance is calculated based on the series resonance principle, so as to achieve the ideal pure resistive operation goal of making the system power factor infinitely close to 1.

[0027] Based on the obtained compensation capacitive reactance value, a binary coding addressing approximation algorithm is used to calculate the optimal discrete capacitor physical combination with the minimum cumulative error. The corresponding solid-state relay group is then triggered synchronously and connected in series to the main transmitting circuit to achieve long cable series resonance. This reduces the impedance to the theoretical limit of pure distributed resistance, allowing the system's current output capability to increase several times instantaneously, even in the high-frequency band of several hundred hertz. In a 3000-meter extreme deep hole, the transmission current can stably exceed 100A across the entire frequency band.

[0028] Step S120 includes: real-time synchronous acquisition of transient voltage and transient current signals at both ends of the current transmission circuit; extraction of the fundamental and main harmonic components of the transient voltage and transient current signals using fast Fourier transform, and calculation of the phase difference between the two at each characteristic frequency point; and dynamic calculation of the equivalent parasitic reactance value based on the phase difference. L eq (f) ,for: ; In the formula, V rms For effective voltage, I rms For the effective current, Δ θ ( f ) is at the characteristic frequency f The phase difference is calculated; with a power factor of approximately 1 as the target, the theoretical compensation capacitive reactance is calculated. ,for: ; The LC resonant array switch is driven by the compensation capacitive reactance value, and the matched capacitor group is connected in series to the main circuit to realize the long cable series resonance, so that the excitation current emitted into the deep strata is greater than or equal to the excitation current threshold.

[0029] Specifically, the adaptive impedance matching unit synchronously acquires the transient voltage and current signals at both ends of the current transmitting circuit in real time; it uses Fast Fourier Transform (FFT) to extract the fundamental and main harmonic components and calculates the phase difference between them at various characteristic frequency points; based on the phase difference, the microprocessor dynamically calculates the equivalent parasitic inductive reactance of the current long conductor system using a formula. The control core calculates the theoretical compensation capacitive reactance value based on the goal of making the power factor approximately 1; it drives the LC resonant array switch board to connect the matching capacitor bank in series to the main circuit, realizing series resonance of the long cable, completely canceling the inductive load of the conductor, and ensuring that the excitation current transmitted to the deep strata is ≥100A.

[0030] The fundamental frequency (FFM) represents the lowest frequency sine wave component with the same period as the original signal, determining the basic energy transmission characteristics of the signal. The major harmonic components represent sine wave components whose frequencies are integer multiples of the fundamental frequency (n > 1). Those with larger amplitudes and significant impacts on waveform distortion are considered major harmonics, such as the 3rd, 5th, and 7th odd harmonics.

[0031] In step S120, the LC resonant array switch board integrates a high-voltage thin-film capacitor matrix arranged with binary weights, and a corresponding high-power contactless solid-state relay (SSR) or bidirectional thyristor array; the microprocessor uses binary encoding addressing technology to seamlessly integrate the physical combination of discrete capacitors corresponding to the calculated Ctarget into the main transmitting circuit within a response time of a few milliseconds, achieving a wide range and high-precision dynamic compensation from tens of microfarads to thousands of microfarads.

[0032] Step S130: The Kalman filter algorithm is used to perform closed-loop dynamic optimal estimation of the electrode contact state to obtain the estimated value of the pushing force. The pushing actuator is dynamically adjusted according to the estimated value of the pushing force so that the electrode array and the well wall achieve the preset optimal stable coupling.

[0033] Specifically, to avoid the generation of nonlinear electrode polarization interference noise that cannot be filtered out due to poor contact between the electrode and the wellbore, which would render the exploration data invalid, a Kalman filter algorithm is used to perform closed-loop dynamic optimal estimation of the contact state between the electrode and the wellbore. Combined with measured displacement and pressure data of noise, state prediction of the previous millisecond, and system inference constraints, the corresponding push force estimate is obtained to eliminate noise. Based on the obtained push force estimate, the push actuator is dynamically adjusted to tightly attach the electrode array to the wellbore rock layer, so that it can achieve the minimum electrical contact resistance requirement while penetrating the mud cake.

[0034] Step S130 includes: setting the system state vector as X k = [x k , v k , F k ] T , where x k For displacement, v k For velocity, F k To provide the pushing force; based on the system state vector, a discretized state prediction equation and a covariance prediction equation are constructed as follows: ; ; In the formula, represents the current state result predicted at time k-1, A is the state transition matrix, represents the optimal value at time k-1, B is the control input matrix, and U... k-1 W is the control vector at time k-1. kLet A be the process noise, let be the system covariance matrix at time k, and let be the system covariance matrix at time k-1. T Let A be the transpose of A, and Q be the process noise covariance; the observation vector Z is obtained through sensors. k = [z x ,k, zF,k] T Calculate the Kalman gain: ; In the formula, K k H is the Kalman gain, and H is the prediction matrix of the object. T Let H be the transpose of H, and R be the covariance matrix of the object measurement noise; execute the state update equation and the covariance update equation to obtain the optimal push force estimate: ; ; In the formula, is the optimal estimate of the state variable at time k, and Z is... k Let be the measured value of the object, be the covariance matrix at time k, and I be the identity matrix; the input control of the pushing actuator is dynamically adjusted according to the estimated pushing force value so that the electrode array and the well wall achieve the preset optimal stable coupling.

[0035] Specifically, a Kalman filter algorithm is introduced to perform closed-loop dynamic optimal estimation of the electrode plate contact state. When the system detects high-frequency and violent fluctuations in the sensor signal (determined to be the rupture of mud bubbles or sudden mechanical impact), the algorithm automatically reduces the trust weight of the sensor and instead places more emphasis on the smooth deduction of the internal physical theoretical model of the system. Conversely, when the sensor data tends to be stable over a long period of time, the algorithm increases the sensor weight and adopts the measured data, thereby achieving efficient and real-time estimation of the dynamic system state under noise interference.

[0036] The system state vector is set, and discretized state prediction equations and covariance prediction equations are constructed. The Kalman gain is calculated by acquiring the observation vector through the sensor. The state update equation and covariance update equation are executed. Environmental and mechanical noise are filtered out by Kalman filtering to obtain the true optimal contact pushing force estimate. This estimate is then used to dynamically adjust the input control of the pushing actuator to ensure that the electrode plate is stably attached to the well wall.

[0037] In step S130, the process noise covariance matrix and measurement noise covariance matrix in the Kalman filter model are not fixed constants, but are dynamically updated in real time according to the downhole drilling mud flow rate, mechanical vibration frequency and temperature drift coefficient through an online adaptive estimation algorithm, thereby ensuring that the push force state estimation always maintains global convergence and optimality under the complex and ever-changing physical disturbances at depth.

[0038] Step S140: Control the on / off state and polarity of electrodes in a specific orientation to generate a focused electromagnetic field in the formation and perform a three-dimensional scan.

[0039] Specifically, by precisely controlling the internal vacuum switch matrix through a high-speed program, a specific three-dimensional geological orientation (e.g., two electrode plates in the upper and lower layers, strictly defined as due north) can be forcibly set as the transmitting current pole (positive pole), while the electrode plates on its opposite side (due south) or the return electrode on the surface at a greater distance can be set as the forced current return pole (negative pole). Therefore, in the heterogeneous underground rock strata, within the geological space due north of the instrument, a high-power focused electromagnetic energy beam with extremely high energy density and strong spatial directivity is formed.

[0040] After collecting transient and steady-state response data at a specific azimuth at a high-precision ground receiver, the topological combination state of the internal electronic switches is rapidly switched within a few milliseconds to transmit energy and rotate it sequentially to panoramic azimuths such as northeast, east, and southeast. This ultimately completes an extremely precise slice-and-layer scan of the surrounding three-dimensional space underground, enabling scanning of complex deep areas and improving detection accuracy.

[0041] Step S140 includes: controlling a specific azimuth electrode group in a multi-layer array electrode as the positive and negative electrodes according to the ground scanning sequence, generating a focused electromagnetic field in the stratum, and performing electron switching scanning at different azimuth angles to simultaneously inject transient step and multi-frequency steady-state energy into the surrounding rock.

[0042] Specifically, each layer of the multi-layer array electrode contains multiple electrodes, and each electrode can be controlled independently. The FPGA controller generates control signals to precisely control the activation state, current magnitude, and duration of each electrode.

[0043] At the precise alignment moment, the FPGA dynamically controls the specific azimuth electrode group in the multi-layer array electrode as the positive and negative electrodes based on the ground scanning sequence, generating a highly directional focused electromagnetic field in the stratum, and performing electron switching scanning at different azimuth angles to simultaneously inject transient step and multi-frequency steady-state energy into the surrounding rock.

[0044] In step S140, a low-noise receiving system with a resolution better than 0.01μV is used at the receiving end. The receiver uses a pre-shared pseudo-random sequence copy to perform cross-correlation despreading on the received mixed response signal containing environmental noise, and perfectly separates and extracts the independent high signal-to-noise ratio time-domain response features and multi-frequency domain amplitude and phase features in the mathematical domain.

[0045] Step S150: Monitor the data transmission status between the ground and the well in real time. When the current attenuation is detected to be greater than the attenuation threshold, return to step S120 to re-switch the capacitor. When a sudden change in contact force is detected, return to step S130 to restart the force-position control until the scan is completed.

[0046] Specifically, since unknown environmental changes may occur 3,000 meters underground, such as encountering extremely fractured strata collapse causing the electrodes to slip instantly and the pressure sensor readings to drop sharply; or the underground high-mineralization aquifer causing a sudden change in environmental conductivity, resulting in uncontrolled abnormal jumps and fluctuations in the emission current, a fault-tolerant self-healing algorithm is set up.

[0047] The surface and downhole systems interact in real time at a rate of ≥10Mbps based on the IEEE 802.3cg standard. The system monitors the data transmission status between the surface and the downhole in real time, including the transmission current, pressure, and capacitance status. If an abnormal attenuation of more than 5% in the transmission current is detected, the system automatically returns to step S120 to re-switch the capacitor. If an abnormal drop in pressure is detected, the system automatically returns to step S130 to restart the force-position control. After all physical and electrical high-standard indicators have completely returned to normal and stable, the system will automatically and seamlessly continue the subsequent three-dimensional time-frequency scanning process from the point of interruption until the scan is completed, ensuring long-term reliable operation in extreme deep environments.

[0048] In this embodiment, digital frequency synthesis technology is used to generate frequency-domain multi-frequency waveforms and time-domain bipolar square waves in parallel, improving data acquisition efficiency and accuracy. Pseudo-random coding technology is employed for spread spectrum recombination to generate a composite excitation sequence, which is input to the high-voltage inverter drive module to output a high-power time-frequency hybrid voltage waveform, ensuring absolute time synchronization and spatial homogeneity of the geophysical response data in both time and frequency domains. Transient voltage and current signals at both ends of the current transmitting circuit are simultaneously acquired, and the compensation capacitive reactance value is calculated. Based on the compensation capacitive reactance value, a matching capacitor bank is connected to achieve series resonance of the long cable, solving the problem of high-frequency attenuation in long conductors in deep wells, widening the physical transmission bandwidth of the long cable, and greatly reducing waveform nonlinear distortion. Kalman filtering is used... The wave algorithm performs closed-loop dynamic optimal estimation of the contact state between the electrode and the wellbore, obtains the estimated pushing force value, and dynamically adjusts the pushing actuator based on the estimated pushing force value, so that the electrode array and the wellbore achieve a preset optimal stable coupling, which greatly improves the electromagnetic energy coupling efficiency in complex heterogeneous rock interfaces. It controls the on / off state and polarity of electrodes in specific orientations to generate a focused electromagnetic field in the formation and perform three-dimensional scanning, improving the three-dimensional scanning accuracy of various orientations in deep wells. It monitors the data transmission status between the surface and the well in real time. When the current attenuation is detected to be greater than the attenuation threshold, it returns to re-switching the capacitor. When a sudden change in contact force is detected, it returns to restart the force-position control until the scanning is completed, ensuring the reliability and stability of deep geological exploration.

[0049] like Figure 2 As shown, a time-frequency electromagnetic hybrid excitation high-power transmission system is provided to realize the time-frequency electromagnetic hybrid excitation high-power transmission method as described above, including: a ground control and power supply system 10, a deep well long wire transmission subsystem 20, an adaptive impedance matching subsystem 30, and a downhole high-power transmission subsystem 40; The ground control and power supply system 10 is configured on the ground and includes a high-power power supply module 11, a main control computer 12, and a synchronous clock timing module 13. The high-power power supply module 11 is used to provide DC high-voltage power. The main control computer 12 is used to issue encoding instructions for time-frequency domain mixed signals, transmission frequency parameters, and duty cycle parameters, and to monitor the downhole working status in real time. The synchronous clock timing module 13 adopts a dual-mode synchronization mechanism of Beidou / GPS and a temperature-controlled crystal oscillator OCXO to synchronize the time of the transmitter and receiver. The deep well long wire transmission subsystem 20 connects the surface control and power supply system 10 with the downhole high-power transmission subsystem 40 for data transmission between the surface and the downhole. An adaptive impedance matching subsystem 30 is connected in series between the deep well long wire transmission subsystem 20 and the downhole high-power transmission subsystem 40, or integrated inside the downhole high-power transmission subsystem 40. It includes a phase detection circuit 31, an LC resonant array switch board 32, and a microprocessor control core 33. The microprocessor control core 33 is used to dynamically calculate the current inductive reactance value of the deep well long wire transmission subsystem 20 based on the phase difference data fed back by the voltage and current phase detection circuit, and automatically switch the matching capacitor array through a solid-state relay array so that the capacitive reactance of the matching capacitor and the inductive reactance of the long wire form a series resonance to meet the resonance condition. The downhole high-power transmission subsystem 40 is installed at the bottom of the deep well or in the target detection layer, including a high-voltage inverter drive module 41, an FPGA time-frequency mixed signal generation module 42, a Kalman force-potential mixed control module 43, and a multi-layer array push electrode group 44. The high-voltage inverter drive module 41 adopts a full-bridge inverter topology based on GaN (gallium nitride) switching transistors. It receives digital control signals from the FPGA time-frequency mixed signal generation module 42 and converts the DC high voltage into a time-frequency mixed high-power electromagnetic excitation signal. The multi-layer array-type push electrode group 44 is arranged around the outer wall of the transmitting probe and includes multiple independently controlled azimuth electrode plates. The Kalman force-position hybrid control module 43 includes a hydraulic or motor push actuator, a pressure sensor, and a displacement sensor. The pressure sensor and displacement sensor collect the contact state between the electrode and the well wall in real time. The Kalman filter algorithm is used to estimate the optimal state of the contact pressure and output a control signal to drive the push actuator, so that the multi-layer array-type push electrode group 44 is tightly attached to the well wall with a set contact force. By controlling the current on / off and polarity combination of different azimuth electrode plates, focused power transmission is achieved.

[0050] In one embodiment, the deep well long conductor transmission subsystem 20 includes a high-voltage power conductor for power transmission and a communication twisted pair for data transmission.

[0051] Specifically, the deep well long wire transmission subsystem 20 connects the surface control and power supply system 10 with the downhole high-power transmission subsystem 40. Its length is designed to be suitable for deep well exploration at depths of ≥3000m. It contains a high-voltage power core for power transmission and a communication twisted pair for data transmission. This transmission subsystem is equivalent to a complex RLC network model containing distributed resistance, distributed capacitance and a large parasitic inductance.

[0052] In one embodiment, the LC resonant array switch board 32 integrates a high-voltage thin-film capacitor matrix arranged with binary weights, and a corresponding high-power contactless solid-state relay or bidirectional thyristor array.

[0053] Specifically, the LC resonant array switch board 32 integrates a high-voltage thin-film capacitor matrix arranged with binary weights, and a corresponding high-power contactless solid-state relay (SSR) or bidirectional thyristor array; the microprocessor control core 33 uses binary encoding addressing technology to seamlessly integrate the physical combination of discrete capacitors corresponding to the calculated Ctarget into the main transmitting circuit within a few milliseconds of response time, achieving a wide range and high-precision dynamic compensation from tens of microfarads to thousands of microfarads.

[0054] Among them, the high-voltage inverter drive module 41 is a full-bridge inverter topology based on GaN switching transistors. It is constructed using high-speed, high-voltage GaN devices with on-resistance as low as milliohms. The module as a whole can withstand high-temperature environments up to 150℃ and supports nanosecond-level switching speed, thereby ensuring that the square wave edge of the time-frequency domain mixed excitation signal is steep and distortion-free in the high-frequency state. The system's comprehensive electromagnetic emission power is ≥160W. The full-bridge drive can ensure that the waveform rising and falling edges of the time-frequency mixed signal are extremely steep and without any sticking distortion in the high-current output state.

[0055] In one embodiment, the FPGA time-frequency mixed signal generation module 42 integrates multiple DDSs. The multiple DDSs generate a multi-frequency superimposed waveform of the fundamental frequency and its multiple harmonic components in parallel, and spread and reassemble it through a pseudo-random sequence. The pseudo-random sequence adopts the maximum length sequence so that the energy of the mixed signal is evenly distributed within the set wide frequency band.

[0056] Specifically, the FPGA time-frequency mixed signal generation module 42 integrates multiple high-precision direct digital frequency synthesizers (DDS). The DDS generates a multi-frequency superimposed waveform of the fundamental frequency and its multiple harmonic components in parallel, and spreads and reassembles it using a pseudo-random sequence. The pseudo-random sequence uses a maximum length sequence m sequence or a Gold sequence to reduce the peak-to-average power ratio (PAPR) of the mixed signal, so that the energy of the mixed signal is evenly distributed within the set wide frequency band, thus preventing the high-voltage inverter drive module from entering the nonlinear saturation region.

[0057] In one embodiment, the multi-layer array push electrode group 44 adopts at least three layers, each layer containing four independent electrode plates evenly distributed on the circumference, for a total of 12 independent electrodes. Each independent electrode plate is connected to the output terminal of the high-voltage inverter drive module 41 through a built-in withstand voltage relay matrix. Under the control of FPGA instructions, it can perform 360-degree electronic scanning switching to generate a focused electromagnetic field in the formation.

[0058] Specifically, the multi-layer array-type push electrode group 44 is arranged around the outside of the long cylindrical probe tube. It adopts a three-layer independent structure design. Each layer contains four independent fan-shaped metal electrode plates evenly distributed in the four quadrants of the circumference. The entire probe tube has a total of 12 completely insulated independent electrode units. The tail end of each electrode is independently connected to the high-voltage output terminal of the high-voltage inverter drive module 41 through a complex electronic switch matrix composed of a high-voltage, high-power vacuum withstand voltage relay group integrated inside the probe tube. The polarity and on / off state of each electrode are controlled by the switch matrix, thereby realizing the scanning of specific geological orientations, improving the scanning accuracy of deep mines and blind areas, and the spatial fineness of the three-dimensional scanning results.

[0059] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0060] It is obvious to those skilled in the art that the modules or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a computer storage medium (ROM / RAM, magnetic disk, optical disk) for execution by the computing device. In some cases, the steps shown or described can be performed in a different order than those described herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Therefore, the present invention is not limited to any particular hardware and software combination.

[0061] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered within the scope of protection of the present invention.

Claims

1. A high-power transmission method using time-frequency electromagnetic hybrid excitation, characterized in that, Includes the following steps: S1: A frequency-domain multi-frequency waveform and a time-domain bipolar square wave are generated in parallel using digital frequency synthesis technology, and a composite excitation sequence is generated by spreading and recombination using pseudo-random coding technology. A high-power time-frequency hybrid voltage waveform is output according to the composite excitation sequence. S2: Synchronously acquire the transient voltage and transient current signals at both ends of the current transmitting circuit, calculate the compensation capacitive reactance value, and connect a matching capacitor bank according to the compensation capacitive reactance value to realize the series resonance of the long cable; S3: The Kalman filter algorithm is used to perform closed-loop dynamic optimal estimation of the electrode contact state to obtain the estimated value of the pushing force, and the pushing actuator is dynamically adjusted according to the estimated value of the pushing force to make the electrode array and the well wall achieve a preset optimal stable coupling. S4: Controls the on / off state and polarity of electrodes in a specific orientation to generate a focused electromagnetic field in the formation and perform three-dimensional scanning; S5: Monitor the data transmission status between the ground and the well in real time. When the current attenuation is detected to be greater than the attenuation threshold, return to step S2 to re-switch the capacitor. When a sudden change in contact force is detected, return to step S3 to restart the force position control until the scan is completed.

2. The high-power transmission method using time-frequency electromagnetic hybrid excitation according to claim 1, characterized in that, Step S1 includes: The three-dimensional spatial characteristics of the deep ore body to be tested, the electrical characteristics of the surrounding rock, and the target detection depth parameters are obtained, and the time-domain excitation parameters and frequency-domain excitation parameters are calculated. The time-domain signal characteristics are set according to the time-domain excitation parameters to obtain a time-domain bipolar square wave with a specific duty cycle; Based on the frequency domain excitation parameters, the frequency domain signal characteristics are set to obtain a multi-frequency superimposed waveform containing the fundamental frequency and its harmonic components at frequencies less than or equal to the set frequency, i.e., a frequency domain multi-frequency waveform. S f ( t ),for: ； In the formula, A n For amplitude, f n For frequency and f n ≤300Hz φ n This is the initial phase; Based on pseudo-random coding technology, the time-domain bipolar square wave and the frequency-domain multi-frequency waveform are modulated and synthesized to generate a composite excitation sequence, as follows: ； In the formula, S t (t) represents a time-domain bipolar square wave. P (t) is a pseudo-random sequence, and α and β are the power allocation weighting coefficients of the time-domain and frequency-domain signals, respectively; The composite excitation sequence is used as a driving signal and is then inverted by a high voltage converter to output a high-power time-frequency hybrid voltage waveform.

3. The high-power transmission method using time-frequency electromagnetic hybrid excitation according to claim 1, characterized in that, Step S2 includes: Real-time synchronous acquisition of transient voltage and current signals at both ends of the current transmission circuit; The fundamental and main harmonic components of the transient voltage and current signals are extracted using Fast Fourier Transform, and the phase difference between them at each characteristic frequency point is calculated. Based on the phase difference, the equivalent parasitic impedance value is dynamically calculated. L eq (f) ,for: ； In the formula, V rms For effective voltage, I rms For the effective current, Δ θ ( f ) is at the characteristic frequency f Phase difference below; Calculate the theoretical compensation capacitive reactance with a power factor of approximately 1 as the objective. ,for: ； The LC resonant array switch board is driven to operate according to the compensation capacitive reactance value, and the matched capacitor group is connected in series to the main circuit to realize the long cable series resonance, so that the excitation current emitted into the deep strata is greater than or equal to the excitation current threshold.

4. The high-power transmission method using time-frequency electromagnetic hybrid excitation according to claim 1, characterized in that, Step S3 includes: Let the system state vector be X k = [x k , v k , F k ] T , where x k For displacement, v k For velocity, F k For pushing force; Based on the system state vector, a discretized state prediction equation and a covariance prediction equation are constructed as follows: ； In the formula, represents the current state result predicted at time k-1, A is the state transition matrix, represents the optimal value at time k-1, B is the control input matrix, and U... k-1 W is the control vector at time k-1. k Let A be the process noise, let be the system covariance matrix at time k, and let be the system covariance matrix at time k-1. T Let A be the transpose of A, and Q be the process noise covariance; The observation vector Z is obtained through the sensor. k = [z x ,k, zF,k] T Calculate the Kalman gain: ； In the formula, K k H is the Kalman gain, and H is the prediction matrix of the object. T Let H be the transpose of H, and R be the covariance matrix of the object measurement noise; By executing the state update equation and the covariance update equation, the optimal push force estimate is obtained: ； ； In the formula, is the optimal estimate of the state variable at time k, and Z is... k Let be the measured value of the object, be the covariance matrix at time k, and I be the identity matrix; The input control of the pushing actuator is dynamically adjusted based on the estimated pushing force value, so that the electrode array and the well wall achieve a preset optimal stable coupling.

5. The high-power transmission method using time-frequency electromagnetic hybrid excitation according to claim 1, characterized in that, Step S4 includes: Based on the ground scanning sequence, the electrode group in a specific orientation of the multi-layer array electrode is controlled as the positive and negative electrodes to generate a focused electromagnetic field in the stratum. Electron switching scanning is performed at different azimuth angles to simultaneously inject transient step and multi-frequency steady-state energy into the surrounding rock.

6. A high-power transmission system with time-frequency electromagnetic hybrid excitation, characterized in that, A method for implementing a time-frequency electromagnetic hybrid excitation high-power transmission method as described in any one of claims 1-5 includes: Surface control and power supply system, deep well long wire transmission subsystem, adaptive impedance matching subsystem, and downhole high-power transmission subsystem; The ground control and power supply system is configured on the ground and includes a high-power power supply module, a main control computer, and a synchronous clock timing module. The high-power power supply module provides DC high-voltage power. The main control computer issues encoding instructions for time-frequency domain mixed signals, transmission frequency parameters, and duty cycle parameters, and monitors the downhole working status in real time. The synchronous clock timing module adopts a dual-mode synchronization mechanism of BeiDou / GPS and a temperature-controlled crystal oscillator OCXO to synchronize the time between the transmitter and receiver. The deep well long wire transmission subsystem connects the surface control and power supply system with the downhole high-power transmission subsystem for data transmission between the surface and the downhole. The adaptive impedance matching subsystem is connected in series between the deep well long wire transmission subsystem and the downhole high-power transmission subsystem, or integrated inside the downhole high-power transmission subsystem. It includes a phase detection circuit, an LC resonant array switch board, and a microprocessor control core. The microprocessor control core is used to dynamically calculate the current inductive reactance of the deep well long wire transmission subsystem based on the phase difference data fed back by the voltage and current phase detection circuit, and automatically switch the matching capacitor array through a solid-state relay array so that the capacitive reactance of the matching capacitor and the inductive reactance of the long wire form a series resonance, satisfying the resonance condition. The downhole high-power transmission subsystem is located at the bottom of the deep well or in the target detection layer, and includes a high-voltage inverter drive module, an FPGA time-frequency mixed signal generation module, a Kalman force-potential mixed control module, and a multi-layer array push electrode group. The high-voltage inverter drive module adopts a full-bridge inverter topology based on GaN (gallium nitride) switching transistors. It receives digital control signals from the FPGA time-frequency mixed signal generation module and converts the DC high voltage into a time-frequency mixed high-power electromagnetic excitation signal. The multi-layer array-type push electrode group is arranged around the outer wall of the transmitting probe and includes multiple independently controlled azimuth electrode plates. The Kalman force-position hybrid control module includes a hydraulic or motor push actuator, a pressure sensor, and a displacement sensor. The pressure sensor and displacement sensor collect the contact state between the electrode and the well wall in real time. The Kalman filter algorithm is used to estimate the optimal state of the contact pressure and output a control signal to drive the push actuator, so that the multi-layer array-type push electrode group is tightly attached to the well wall with a set contact force. By controlling the current on / off and polarity combination of different azimuth electrode plates, focused power transmission is achieved.

7. A high-power transmission system with time-frequency electromagnetic hybrid excitation according to claim 6, characterized in that, The deep well long conductor transmission subsystem includes a high-voltage power core for power transmission and a communication twisted pair for data transmission.

8. A high-power transmission system with time-frequency electromagnetic hybrid excitation according to claim 6, characterized in that, The LC resonant array switch board integrates a high-voltage thin-film capacitor matrix arranged with binary weights, and a corresponding high-power contactless solid-state relay or bidirectional thyristor array.

9. A high-power transmission system with time-frequency electromagnetic hybrid excitation according to claim 6, characterized in that, The FPGA time-frequency mixed signal generation module integrates multiple DDSs, which generate multi-frequency superimposed waveforms of the fundamental frequency and its multiple harmonic components in parallel. The waveforms are then spread and time-reassembled using a pseudo-random sequence. The pseudo-random sequence uses the maximum length sequence to ensure that the energy of the mixed signal is evenly distributed within a set wide frequency band.

10. A high-power transmission system with time-frequency electromagnetic hybrid excitation according to claim 6, characterized in that, The multi-layer array push electrode group adopts at least three layers. Each layer contains four independent electrode plates evenly distributed on the circumference, for a total of 12 independent electrodes. Each independent electrode plate is connected to the output terminal of the high-voltage inverter drive module through a built-in withstand voltage relay matrix. Under the control of FPGA instructions, it can perform 360-degree electronic scanning switching to generate a focused electromagnetic field in the formation.

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