High-voltage high-power towed transient electromagnetic detection device and detection method

Abstract

This application belongs to the field of geophysical electromagnetic detection technology, specifically relating to a high-voltage, high-power towed transient electromagnetic detection device and method. The device includes a main control module, N H-bridge transmitting modules, and N independent power supply units, each connected to the DC bus input of the N H-bridge transmitting modules; N high-voltage clamping units, each connected in parallel to both ends of the DC bus of the N H-bridge transmitting modules; a mode switching switch group, positioned between each high-voltage clamping unit and its corresponding H-bridge transmitting module; a topology switching switch, used to selectively configure the output of each H-bridge transmitting module as a series superposition combination; and a transmitting coil connected to the output of the H-bridge transmitting module or the series combination combination. This application achieves multi-magnetic-moment emission within a single cycle, i.e., emitting currents of different amplitudes, enabling simultaneous multi-level detection and solving the problems of low power and inability to cover both shallow and deep areas in traditional transient electromagnetic detection.

Description

Technical Field

[0001] This application belongs to the field of geophysical electromagnetic detection technology, specifically, it relates to a high-voltage, high-power towed transient electromagnetic detection device and detection method. Background Technology

[0002] With rapid economic development and continuous iteration of intelligent technologies, the application scenarios of mobile platforms such as drones, autonomous vehicles, and intelligent ships are constantly expanding. Conducting efficient detection based on these platforms has become an important development direction in fields such as resource exploration and environmental monitoring. Against this backdrop, detection technologies that are adaptable to mobile platforms and possess both flexibility and accuracy are particularly important. Electromagnetic methods, as one of the mainstream geophysical detection technologies, especially the towed transient electromagnetic detection method, have demonstrated significant application value in various mobile platform-based detection scenarios due to their advantages such as large detection depth, wide coverage, convenient operation, and flexible adaptability to drones, autonomous vehicles, and intelligent ships.

[0003] However, traditional transient electromagnetic (TEM) systems still face numerous technical bottlenecks in practical applications: First, current TEM systems, limited by circuit design and the impedance characteristics of the transmitting coil, can mostly only output single-moment waveforms with relatively small peak currents. This results in insufficient excitation energy for deep geological bodies, leading to weak electromagnetic response signals and ultimately making it difficult to simultaneously meet the detection needs of both shallow and deep areas. Second, traditional TEM systems are limited by the voltage withstand capability and structure of components, preventing high-voltage, high-power output. This results in weak depth penetration and stability. Furthermore, traditional series-type TEM systems suffer from uneven voltage distribution among components, making them prone to breakdown and causing instability. Third, existing TEM devices often have limited functionality. To complete geological exploration tasks at different depths, frequent equipment replacements are usually necessary, significantly reducing overall detection efficiency. In addition, the system is prone to overheating and component damage during operation, leading to malfunctions that affect equipment stability and limit the ability to operate continuously for extended periods.

[0004] These issues collectively make it difficult for existing towed transient electromagnetic systems to achieve comprehensive detection at multiple depths, with high voltage and power output and high precision in complex detection environments. They fail to meet the higher demands placed on detection technology by combining complex detection environments with intelligent detection. Therefore, it is urgent to overcome the limitations of existing technologies through innovative circuit structures and system designs, and to develop a towed transient electromagnetic system that can handle both deep and shallow subsurface detection, and possesses higher efficiency and better stability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides both a high-voltage, high-power towed transient electromagnetic detection device and a high-voltage, high-power towed transient electromagnetic detection method. This transient electromagnetic detection device and method utilize an innovative multi-H-bridge series technology to emit multiple magnetic moment waveforms with a transmission current reaching hundreds of amperes, effectively meeting the needs of geological exploration at multiple depths and significantly improving detection efficiency and system stability.

[0006] The objective of this application is achieved through the following technical solution: The first aspect of this application provides a high-voltage, high-power towed transient electromagnetic detection device, comprising: The main control module is used to generate variable frequency and variable duty cycle PWM control signals and coordinate the timing logic of the entire device; N H-bridge transmitter modules, each with an independent DC bus input terminal and a bipolar AC output terminal. The AC output terminals of each H-bridge transmitter module can be configured to be connected in series and drive the same transmitter coil together through a mode switching switch group. N independent power supply units are connected to the DC bus input terminals of the N H-bridge transmitter modules respectively. Each power supply unit includes a DC-DC boost module and its corresponding protection diode, which are used to provide an independently adjustable bus voltage to the corresponding H-bridge transmitter module. N high-voltage clamping units are connected in parallel to both ends of the DC bus of the N H-bridge transmitting modules. Each high-voltage clamping unit includes a clamping capacitor bank and an IGBT switch connected in series. The IGBT switch has an anti-parallel body diode, which is used to guide the coil freewheeling current to the clamping capacitor bank through the body diode to achieve voltage clamping during the current turn-off phase. The mode switching switch group includes: IGBT switching transistors, which are located between each high-voltage clamping unit and the corresponding H-bridge transmitter module; A topology switching switch is installed between the AC output terminals of adjacent H-bridge transmitter modules to selectively configure the outputs of each H-bridge transmitter module as a series superposition combination. The transmitting coil is connected to the output terminal of the H-bridge transmitting module or a series combination, and is used to generate an excitation magnetic field based on the combined bipolar transmitting current.

[0007] Furthermore, the mode switching switch group, under the control of the main control module, switches between any one or a combination of the following operating states among the N H-bridge transmitting modules: Independent operating mode: Only a single H-bridge transmitter module is in operation, corresponding to a single DC-DC boost module for power supply; Series superposition mode: The AC output terminals of K H-bridge transmitting modules are connected in series, and the bus voltages of each module are superimposed for output.

[0008] Furthermore, it also includes a damping circuit, comprising a damping resistor connected in series and a control switch, wherein the damping circuit is connected in parallel across the transmitting coil.

[0009] Furthermore, the bus voltage of each DC-DC boost module is independently adjustable. Under different magnetic moment modes, the main control module can achieve continuous or graded fine adjustment of the transmitting magnetic moment by adjusting the number of DC-DC boost modules in operation and the voltage setting value of each DC-DC boost module, combined with the series topology configuration of the H-bridge transmitting module.

[0010] Furthermore, each H-bridge transmitter module includes a first half-bridge branch and a second half-bridge branch. The first half-bridge branch includes transistors Q1 and Q2 connected in series, and the second half-bridge branch includes transistors Q3 and Q4 connected in series. The series connection node of transistors Q1 and Q2 of the first H-bridge transmitter module is connected to one end of the transmitter coil via a first connection line. A topology control switch is provided on the first connection line. The series connection node of transistors Q3 and Q4 is connected to the first half-bridge branch of the next connected H-bridge transmitter module. The series connection node of transistors Q3 and Q4 of the Nth H-bridge transmitter module is connected to the other end of the transmitter coil. A topology control switch is provided between the series connection node of transistors Q3 and Q4 of the remaining H-bridge transmitter modules and the first connection line.

[0011] A second aspect of this application provides a high-voltage, high-power towed transient electromagnetic detection method, comprising the following steps: The host computer inputs the voltage parameters, number of transmission cycles, and transmission frequency of each DC-DC boost module and transmits them to the main control module. The main control module adjusts the output voltage of each DC-DC boost module according to the input voltage parameters and adjusts the frequency and duty cycle of the transmission waveform according to the input transmission frequency f. The main control module initiates the current detection process by continuously collecting the current magnitude of the transmitting coil through a current sensor installed in the transmitting circuit. Within one excitation pulse period T, according to the preset multi-magnetic moment mode sequence, a magnetic moment pulse waveform containing K different peak currents is emitted, where K is a positive integer and 2≤K≤N, N is the total number of H-bridge transmitting modules, and the peak current of each mode increases sequentially or changes according to the preset sequence. Determine whether all preset magnetic moment pulse waveforms have been transmitted. If so, the operation ends; otherwise, repeat the multi-mode sequence transmission.

[0012] Furthermore, in the multi-magnetic moment mode sequence transmission, the transmission mode switches between each magnetic moment pulse transmission mode sequentially in the following manner: Mode 1: Only one H-bridge transmitter module is in operation, corresponding to a power supply from one DC-DC boost module; Mode 2: Two H-bridge transmitter modules are in operation, corresponding to two DC-DC boost modules for power supply; Similarly, in the Nth mode: K H-bridge transmitter modules are put into operation, corresponding to K DC-DC boost modules for power supply.

[0013] Furthermore, the transmission time for each magnetic moment pulse emission mode is T / (2k), and the process includes: According to the current mode number, the main control module controls the corresponding IGBT switch and topology control switch to close, connects k DC-DC boost modules and k high-voltage clamping modules into the circuit at the same time, and configures k H-bridge transmitter modules as series output, where k is a positive integer and 1≤k≤K; The PWM drive module emits a PWM-A signal to drive the corresponding H-bridge transmitter module, causing the first diagonal switch in each H-bridge transmitter module to close and enter the rapid current rise phase. Determine whether the transmission current has risen to the preset peak value. If not, repeat the determination. If yes, proceed to the next step. The determination is based on whether the real-time current parameters collected by the current sensor have reached the preset peak value of the current mode. The main control module controls the corresponding clamping switch to open, and the k DC-DC boost modules currently in operation jointly maintain the transmit current to enter the flat-top phase; Determine whether the control signal PWM-A has ended. If not, repeat the determination. If yes, proceed to the next step. The determination is based on whether the real-time current parameter collected by the current sensor has started to decrease. When the control signal PWM-A ends, the circuit current flows through the body diode of the corresponding clamping switch IGBT switching transistor into the corresponding k clamping capacitor groups. Each clamping capacitor group applies a reverse clamping voltage across the transmitting coil, causing the transmitting coil current to drop rapidly. The main control module controls the damping switch to close, so that the damping resistor is connected to the transmitting coil to suppress current overshoot and tail oscillation.

[0014] The advantages of this application compared to the prior art, based on the above design scheme, are as follows: This application achieves high-voltage, high-power output by using multiple H-bridge transmitting module logic switch control series technology. The transmitting current can reach hundreds of amperes, and it realizes the multi-magnetic moment transmission effect within a single cycle, that is, transmitting currents of different amplitudes to achieve the effect of multi-level simultaneous detection. This solves the pain points of traditional transient electromagnetic transmission power being small and unable to cover both shallow and deep areas. This application utilizes a multi-H-bridge transmitter module series connection technology to achieve high withstand voltage and cascaded voltage equalization, enabling rapid turn-off under higher power excitation conditions. Due to the large parasitic parameters of the dragged multi-turn small-size transmitter coil, a high voltage is generated instantaneously during turn-off, which can easily lead to device breakdown. Furthermore, the external clamping voltage is limited by the withstand voltage of the switching transistor. This invention can increase the withstand voltage by n times, where n is the number of series-connected H-bridge transmitter modules, significantly improving stability and reducing turn-off time. This application utilizes a multi-H-bridge transmitter module cascade technology, which allows each H-bridge transmitter module to operate independently without interfering with others, thus significantly improving the overall system stability. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate this application and form part of this application. The illustrative embodiments and descriptions thereof are used to understand this application and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a circuit diagram of the high-voltage, high-power towed transient electromagnetic detection device in Embodiment 1 of this application; Figure 2 This is a schematic block diagram of the high-voltage, high-power towed transient electromagnetic detection device in the embodiments of this application; Figure 3 This is a schematic flowchart illustrating the system operation of the high-voltage, high-power towed transient electromagnetic detection method in the embodiments of this application. Figure 4 This is a transmission timing diagram of the high-voltage, high-power towed transient electromagnetic detection method in the embodiments of this application; Figure 5 This is a circuit diagram of the high-voltage, high-power towed transient electromagnetic detection device in Embodiment 2 of this application. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0017] Example 1, see Figure 1 and Figure 2This application provides a towed transient electromagnetic detection device based on multi-magnetic moment emission. The transient electromagnetic detection device includes a main control module 1; a first host computer 2; a first power supply 3; a first A / D acquisition module 4; a first preamplifier 5; a first receiving coil 6; a first PWM driver 7; a first H-bridge transmitting module 8; a first switch 9; a first current sensor 10; a first protection diode 11; a first DC-DC boost module 12; a first clamping capacitor bank 13; a first DC-DC high-voltage clamping module 14; a second switch 15; a third switch 16; a second host computer 17; a second power supply 18; a second A / D acquisition module 19; a second preamplifier 20; a second receiving coil 21; a second PWM driver 22; a second H-bridge transmitting module 23; a fourth switch 24; a second current sensor 25; a second protection diode 26; a second clamping capacitor bank 27; a second DC-DC high-voltage clamping module 28; a damping resistor 29; a transmitting coil 30; a fifth switch 31; a mobile platform 32; and an equipment carrier 33.

[0018] In this embodiment, there are two H-bridge transmitting modules. Each H-bridge transmitting module has an independent DC bus input terminal and a bipolar AC output terminal. The AC output terminals of each H-bridge transmitting module can be configured to be connected in series and drive the same transmitting coil 30 together through a mode switching switch group. The main control module 1 is used to generate a variable frequency and variable duty cycle PWM control signal and coordinate the timing logic of the entire device. The main control module 1 is communicatively connected to the first host computer 2 and the second host computer 17. The first receiving coil 6 is sequentially connected to the first preamplifier 5 and the first A / D acquisition module 4, and then connected to the main control module 1. Under the control of the main control module 1, the first power supply 3 provides power to the first DC-DC boost module 12, the first host computer 2, and the first current sensor 10; The first H-bridge transmitting module 8 and the second H-bridge transmitting module 23 have the same structure, including: a first half-bridge branch and a second half-bridge branch. The first half-bridge branch includes transistors Q1 and Q2 connected in series, and the second half-bridge branch includes transistors Q3 and Q4 connected in series. The series connection of transistors Q1 and Q2 is connected to one end of the transmitting coil, and the series connection of transistors Q3 and Q4 is connected to the first half-bridge branch of the second H-bridge transmitting module. The common terminal of transistors Q1 and Q3 is connected to the first protection diode. The common terminal of transistors Q2 and Q4 is grounded. The second H-bridge transmitting module 8 is completely identical to the first H-bridge transmitting module 23, except that the first half-bridge branch in the second H-bridge transmitting module 23 is connected to the second half-bridge branch of the first H-bridge transmitting module 8, and the second half-bridge branch in the second H-bridge transmitting module is connected to the first half-bridge branch of the first H-bridge transmitting module after being connected to the second switch 15 through the transmitting coil.

[0019] The first H-bridge transmitter module 8 has two DC bus input terminals. One DC bus input terminal is connected to the first PWM driver 7, and the other DC bus input terminal is grounded. The first protection diode 11 is connected in series with the first DC-DC boost module 12 and then in parallel with the two DC bus input terminals of the first H-bridge transmitter module 8. The first switch 9 is a transistor. The gate of the transistor is connected to the main controller 1. The drain of the first switch 9 is connected to the node between transistors Q1 and Q3. The first switch 9 is connected in series with the DC bus input terminal of the first H-bridge transmitter module 8 and then connected to the first clamping capacitor group 13. The other end of the first clamping capacitor group 13 is grounded. The first DC-DC high voltage clamping module 14 is connected in parallel with the first clamping capacitor group 13.

[0020] The second H-bridge transmitter module 23 has the same structure as the first H-bridge transmitter module 8. The second H-bridge transmitter module 23 has two DC bus input terminals. One DC bus input terminal is connected to the second PWM driver 22, and the other DC bus input terminal is grounded. The second protection diode 26 is connected in series with the second DC-DC boost module 27 and then in parallel with the two DC bus input terminals of the second H-bridge transmitter module 23. The fourth switch 24 is a transistor. The gate of the transistor is connected to the main controller 1. The drain of the fourth switch 24 is connected to the node between transistors Q1 and Q3. The fourth switch 24 is connected in series with the DC bus input terminal of the second H-bridge transmitter module 23 and then connected to the second clamping capacitor group 28. The other end of the second clamping capacitor group 28 is grounded. The second DC-DC high voltage clamping module 29 is connected in parallel with the second clamping capacitor group 28.

[0021] One end of the third switch 16 is located between the second half-bridge branch of the first H-bridge transmitter module 8 and the first half-bridge branch of the second H-bridge transmitter module 23. The other end of the third switch 16 is connected between the second switch 15 and the transmitter coil 31. When the third switch 16 is closed and the second switch 15 is open, only the second H-bridge transmitter module 23 is connected to the circuit.

[0022] A damping resistor 30 is connected in parallel across the two ends of the transmitting coil 31. The damping resistor 30 is connected in series with the fifth switch 32.

[0023] All switches are controlled by the main control module 1. The first current sensor 10 collects the output current of the first half-bridge branch of the first H-bridge transmitting module 8, and the second current sensor 25 collects the output current of the first half-bridge branch of the second H-bridge transmitting module 23. Similarly, the second H-bridge transmitting module 23 is equipped with a second host computer 17, and the second receiving coil 21 is connected in sequence to the second preamplifier 20 and the second A / D acquisition module 19, and then connected to the main control module 1. Under the control of the main control module 1, the second power supply 18 provides power to the second DC-DC boost module 27, the second host computer 17, and the second current sensor 25.

[0024] The device proposed in this application organically integrates and consolidates the above-mentioned devices or modules into a whole. It should be emphasized that, as a single unit, the specific structure for each device or module to achieve its intended function already exists in the prior art, and the protocols, software or programs involved in the operation of each device and / or module also already exist in the prior art, which are well known to those skilled in the art.

[0025] The transient electromagnetic detection device based on high-voltage, high-power towed circuit proposed in this application uses a main control module 1 as its core. The main control module 1 employs an STM32 series microcontroller and is responsible for the timing control, PWM signal generation, current waveform monitoring, and data acquisition of the entire transient electromagnetic detection device. The transient electromagnetic detection device is powered by power supplies 3 and 18, and the required voltage is provided in stages through a first DC-DC boost module 12 and a second DC-DC boost module 27. The protection circuit in this application includes a first protection diode 11 and a second protection diode 26 connected in parallel in the corresponding power supply branches. The first protection diode 11 is used to prevent damage from excessive voltage when the first DC-DC boost module 12 is connected to the circuit, thus protecting the circuit. The second protection diode 26 is used to prevent damage from excessive voltage when the second DC-DC boost module 27 is connected to the circuit, thus protecting the circuit. The main control module 1 generates PWM signals with adjustable frequency and duty cycle, which drive the first H-bridge transmitting module 8 and the second H-bridge transmitting module 17 to operate via the first PWM driver 7 and the second PWM driver 22, respectively, generating corresponding bipolar transmitting currents, which in turn generate an excitation magnetic field through the transmitting coil 19. The main control module 1 monitors the current waveform of the transmitting coil 31 via the first current sensor 10 and the second current sensor 15, respectively. The main control module 1 amplifies and acquires the signals sensed by the first receiving coil 6 and the second receiving coil 21 by controlling the first preamplifier 5, the second preamplifier 20, the first A / D acquisition module 4, and the second A / D acquisition module 19. The first host computer 2 and the second host computer 17 can respectively realize human-machine interaction functions, transmitting the parameters required for device operation to the main control module 1, and receiving and displaying the data returned from the main control module 1. The first receiving coil 6 and the second receiving coil 21 respectively receive the secondary field signals generated by the transmitting coil 31 through the underground medium, thereby obtaining underground geological information; see [link to relevant documentation]. Figure 2As shown, the mobile platform 32 consists of a non-metallic frame and detachable wheels. It carries the transmitting coil 31, the first receiving coil 6, and the second receiving coil 21 for mobile measurement, avoiding manual coil laying and improving detection efficiency. The equipment carrier 33 can be used in several special environments: underwater detection towed by an experimental vessel, detection by an unmanned vehicle, or detection by a drone. The equipment carrier 33 carries an electromagnetic transmitting and receiving system and is used to connect to the mobile platform 32. The second switch 15, the third switch 16, and the fifth switch 32 are ordinary switch triggers; the first switch 9 and the fourth switch 24 use transistors with anti-parallel diodes (IGBT switching transistors, also known as insulated gate bipolar transistors). When the first switch 9 and the fourth switch 24 are open, current flows through the internal body diode into the first clamping capacitor group 13 and the second clamping capacitor group 28. The specific structures of the first switch 9, the second switch 15, the third switch 16, the fourth switch 24, and the fifth switch 32 are all existing technologies and will not be described in detail here.

[0026] The control process of the transmit current of two H-bridge transmitter modules is as follows: First magnetic moment pulse transmission mode: Under the control of the main control module 1, the third switch 16 is closed, connecting the second DC-DC boost module 27 to the circuit; simultaneously, the fourth switch 24 is closed, activating the second high-voltage clamping module 29 and guiding the transmission current to rise rapidly. After entering the flat-top maintenance phase, the third switch 16 remains closed, and the second DC-DC boost module 27 maintains a stable current. During this phase, the first switch 9 and the second switch 15 remain open, and the fifth switch 32 is connected to the circuit when the damping circuit is working. Only... Figure 1 The second bridge launch module 23 is in operation.

[0027] Second magnetic moment pulse transmission mode: The second switch 15 is closed, connecting the two H-bridge transmitter modules to work together. During this process, the second DC-DC boost module 27 and the first DC-DC boost module 12 operate simultaneously. Simultaneously, the first switch 9 is closed to connect the first high-voltage clamping module 14, enabling a rapid current rise. During the flat-top phase, the second switch 15 remains closed, and the current is maintained by the simultaneous operation of the second DC-DC boost module 27 and the first DC-DC boost module 12. During this phase, the third switch 16 and the fourth switch 24 remain open, while the fifth switch 32 is connected to the circuit when the damping circuit is active. Both H-bridge transmitter modules operate together in the circuit.

[0028] The peak currents of the first magnetic moment pulse and the second magnetic moment pulse increase sequentially.

[0029] Turn-off Phase and Protection Mechanism: In the current turn-off phase, under the first magnetic moment pulse emission mode, the main control module 1 controls the fourth switch 24 to open. At this time, the first switch 9, the second switch 15, the third switch 16, and the fifth switch 32 are all open. When the fourth switch 24 is open, the current flows into the second clamping capacitor group 28 through the internal body diode, connecting the second clamping capacitor group 28 to the circuit to achieve voltage clamping and force the current to drop rapidly. At the same time, by closing the fifth switch 32 and connecting the damping resistor 30, the first switch 9, the second switch 15, the third switch 16, and the fourth switch 24 are all open, suppressing current overshoot and tail oscillation during the turn-off process. Under the second magnetic moment pulse emission mode, the main control module 1 controls the first switch 9 to open. When the first switch 9 is open, the second switch 15, the third switch 16, and the fourth switch 24 are all open. The current flows into the first clamping capacitor group 13 through the internal body diode, connecting the first clamping capacitor group 13 to the circuit to achieve voltage clamping and force the current to drop rapidly. At the same time, by closing the fifth switch 32 and connecting the damping resistor 30, the first switch 9, the second switch 15, the third switch 16 and the fourth switch 24 are all disconnected, suppressing the current overshoot and tail oscillation during the turn-off process. Auxiliary function implementation: The main control module 1 generates a PWM signal with adjustable frequency and duty cycle to drive the first H-bridge transmitting module 8 and the second H-bridge transmitting module 23 to generate bipolar transmitting current. In two different operating modes, the current waveform of the transmitting coil 31 is monitored in real time by the first current sensor 10 and the second current sensor 25 to ensure the quality of the transmitted waveform. The received signal is conditioned and acquired by the first preamplifier 4 and the first A / D acquisition module 5, and the second preamplifier 19 and the second A / D acquisition module 20, respectively, in the two different operating modes. The mobile platform 32, in conjunction with the equipment carrier 33, enables the mobile deployment and mobile measurement of the transmitting coil 31, the first receiving coil 6, and the second receiving coil 21, effectively improving detection efficiency.

[0030] See Figure 3 As shown, this embodiment provides a method for rapid and high-precision towed array electromagnetic detection using the aforementioned transient electromagnetic detection device. The method includes the following steps: The host computer inputs the voltage parameters, number of transmission cycles, and transmission frequency of the two DC-DC boost modules respectively, and transmits them to the main control module. The main control module 1 adjusts the output voltage of each DC-DC boost module according to the input voltage parameters, and adjusts the frequency and duty cycle of the transmission waveform according to the input transmission frequency f. The current magnitude of the transmitting coil 31 is continuously collected by a current sensor installed in the transmitting circuit, and the main control module 1 starts the current detection process. Within one excitation pulse period T, according to the preset multi-magnetic moment mode sequence, magnetic moment pulse waveforms containing 1-K different peak currents are emitted, where K is a positive integer and 2≤K≤N, N is the total number of H-bridge transmitting modules, and the peak current of each mode increases sequentially or changes according to the preset sequence. Determine whether all preset magnetic moment pulse waveforms have been transmitted. If so, the operation ends; otherwise, repeat the multi-mode sequence transmission.

[0031] Specifically, it includes: After the transient electromagnetic detection device is connected, the voltage parameters of the first DC-DC boost module 12 and the second DC-DC boost module 27, the number of transmission cycles Q, and the transmission frequency f are respectively input through the first host computer 2 and the first host computer 17, and then transmitted to the main control module 1. The main control module 1 adjusts the output voltage of the first DC-DC boost module 12 and the second DC-DC boost module 27 according to the input voltage parameters, and adjusts the frequency and duty cycle of the transient electromagnetic detection device's transmission waveform according to the input transmission frequency f. The current magnitude of the transmitting coil 31 is continuously collected by the first current sensor 10 and the second current sensor 25 respectively. The main control module 1 starts the current detection process by the first current sensor 10 and the second current sensor 25 respectively. The system begins transmitting two magnetic moment pulse waveforms with different peak currents. If the transmission of two magnetic moment pulse waveforms with different peak currents has been completed, the operation ends; otherwise, proceed to step 4.

[0032] See Figure 4 As shown, the specific process of emitting two magnetic moment pulse waveforms with different peak currents is as follows: Within one emission period T, two magnetic moment pulse waveforms with different peak currents are emitted once, where T is the excitation pulse period. The control signals for the first H-bridge emission module 8 and the second H-bridge emission module 23 are Q (PWM-A, PWM-B). The pulse emission steps for a single emission period T are as follows: The main control module 1 closes the third switch 16 and the fourth switch 24, opens the first switch 9, the second switch 15 and the fifth switch 32, closes the third switch, and connects the second DC-DC boost module 27 and the second high-voltage clamping module 29 into the circuit to prepare for the first magnetic moment pulse to be emitted. The first magnetic moment pulse is emitted. The second PWM driver 22 emits the control signal PWM-A to drive the second H-bridge emitter module 23, causing transistors Q1 and Q4 to close. At this time, t=t1, and the process is ready to enter the rapid current rise stage. Determine if the transmitting current has risen to its maximum value I. maxIf yes, proceed to the next step; otherwise, repeat this step.

[0033] The main control module 1 controls the fourth switch 24 to open. At this time, the first switch 9, the second switch 15, the fifth switch 32 are all open, the third switch 16 is closed, and the second DC-DC boost module 27 maintains the transmission current. Determine whether the control signal PWM-A has ended. If yes, proceed to the next step; otherwise, repeat this step. The determination is based on whether the real-time current parameter collected by the current sensor 25 has started to decrease. The main control module 1 continues to control the third switch 16 to close. When the control signal PWM-A ends, the circuit current flows into the second clamping capacitor group 28 through the diode of the fourth switch 24. At this time, the second clamping capacitor group 28 applies a reverse clamping voltage across the transmitting coil 31, causing the current of the transmitting coil 31 to drop rapidly. This process is the stage where the clamping module works to make the transmitting current drop rapidly, preparing to enter the signal acquisition stage. Only the third switch 16 is closed. The main control module 1 controls the fifth switch 32 to close. At this time, the first switch 9, the second switch 15, the fourth switch 24 are all open, and the third switch 16 is closed, so that the damping resistor 30 is connected to the transmitting coil 31 to solve the problem of overshoot of the transmitting current and prevent the transmitting waveform from trailing and oscillating. The main control module 1 controls the third switch 16 and the fifth switch 32 to open. At this time, the first switch 9, the second switch 15, and the fourth switch 24 are all opened, and the damping resistor 30 is disconnected from the transmitting coil 31. Determine whether the signal acquisition is complete. If yes, proceed to the next step; otherwise, repeat this step. The determination is based on whether the transmission time t is equal to T / 4. Main control module 1 maintains the switch drive state unchanged and begins the second magnetic moment pulse transmission; The main control module 1 closes the second switch 15 and the first switch 9 by controlling the third switch 16, the fourth switch 24 and the fifth switch 32 to open, and connects the first DC-DC boost module 12 and the second DC-DC high voltage clamping module 14 into the circuit. At this time, the two H-bridge transmitter modules are in series and ready for the rapid rise of the transmission current. The second magnetic moment pulse is emitted. The first PWM driver 7 and the second PWM driver 22 simultaneously drive the emission control signal PWM-A to drive the first H-bridge emission module 8 and the second H-bridge emission module 23, causing transistors Q1, Q4 and Q1 to close. At this time, t=t5, and the current rapidly rises. Determine if the transmitting current has risen to its maximum value I. max If yes, proceed to the next step; otherwise, repeat this step. The judgment is based on whether the real-time current parameters collected by the first current sensor 10 have reached their peak value. The main control module 1 controls the first switch 9 to open. At this time, the third switch 16, the fourth switch 24, the fifth switch 32 are all open, and the second switch 15 is closed. The first DC-DC boost module 12 and the second DC-DC boost module 27 maintain the transmission current. Determine whether the control signal PWM-A has ended. If yes, proceed to the next step; otherwise, repeat this step. The determination is based on whether the real-time current parameter collected by the first current sensor 10 has started to decrease. The main control module 1 still controls the second switch 15 to close. At this time, the first switch 9, the third switch 16, the fourth switch 24, and the fifth switch 31 are all open. When the control signal PWM-A ends, the circuit current flows into the first clamping capacitor group 13 through the first switch 9. At this time, the first clamping capacitor group 13 applies a reverse clamping voltage across the transmitting coil 31, causing the current in the transmitting coil 31 to drop rapidly. This process is the stage where the clamping module works to make the transmitting current drop rapidly, preparing to enter the signal acquisition stage. The main control module 1 controls the fifth switch 32 to close. At this time, the first, second, third and fourth switches are all open, so that the damping resistor 30 is connected to the transmitting coil 31, which solves the problem of overshoot in the transmitting current and prevents the transmitting waveform from trailing and oscillating. The main control module 1 controls the second switch 15 and the fifth switch 32 to open, and the first switch 9, the third switch 16, and the fourth switch 24 to open, thus disconnecting the damping resistor 30 from the transmitting coil 31. Determine whether the signal acquisition is complete. If yes, proceed to the next step; otherwise, repeat this step. The determination is based on whether the transmission time t is equal to T / 2. The signal acquisition of the receiving coil ends, and the current transmission of the T / 2 cycle ends.

[0034] The negative pulse emission in the last T / 2 cycles is similar to the positive pulse above. The difference is that in the negative pulse current emission stage, the transistors Q2 and Q3 of the first H-bridge transmitter module 8 and the second H-bridge transmitter module 23 are closed, and the control signal is a negative PWM signal, thereby emitting a negative pulse.

[0035] like Figure 4 As shown, PWM-A represents a positive PWM signal and PWM-B represents a negative PWM signal. It should be noted that the "positive" and "negative" of the PWM signal (pulse width modulation) describe the direction of its duty cycle deviation relative to the reference level, that is, whether the effective level is high or low. A positive PWM signal (effective level high) and a negative PWM signal (effective level low) belong to the prior art.

[0036] Example 2, unlike Example 1, includes N H-bridge transmitting modules. See [link / reference]. Figure 5As shown, it specifically includes: a main control module, used to generate variable frequency and variable duty cycle PWM control signals and coordinate the timing logic of the entire device; N H-bridge transmitter modules, each with an independent DC bus input terminal and a bipolar AC output terminal. The AC output terminals of each H-bridge transmitter module can be configured to be connected in series and drive the same transmitter coil together through a mode switching switch group. N independent power supply units are connected to the DC bus input terminals of the N H-bridge transmitter modules respectively. Each power supply unit includes a DC-DC boost module and its corresponding protection diode, which are used to provide an independently adjustable bus voltage to the corresponding H-bridge transmitter module. N high-voltage clamping units are connected in parallel to both ends of the DC bus of the N H-bridge transmitting modules. Each high-voltage clamping unit includes a clamping capacitor bank and an IGBT switch connected in series. The IGBT switch has an anti-parallel body diode, which is used to guide the coil freewheeling current to the clamping capacitor bank through the body diode to achieve voltage clamping during the current turn-off phase. The mode switching switch group includes: IGBT switching transistors, which are located between each high-voltage clamping unit and the corresponding H-bridge transmitter module; A topology switching switch is installed between the AC output terminals of adjacent H-bridge transmitter modules to selectively configure the outputs of each H-bridge transmitter module as a series superposition combination. The transmitting coil is connected to the output terminal of the H-bridge transmitting module or a series combination, and is used to generate an excitation magnetic field based on the combined bipolar transmitting current.

[0037] Unlike the parallel operation of two H-bridge transmitting modules in Embodiment 1, this embodiment provides a transient electromagnetic detection device that can be configured in series with N H-bridge transmitting modules (N≥2). By connecting the AC output terminals of multiple H-bridge transmitting modules in series, higher output voltage and larger magnetic moment can be achieved to meet the high transmission power requirements of ultra-deep geological exploration. N is selected, preferably 2~8.

[0038] The main control module generates PWM control signals with independently adjustable frequency and duty cycle, and coordinates the timing logic of the entire device. Main control module 1 connects to the corresponding PWM drive modules of each H-bridge transmitter module via multiple PWM output ports to achieve independent or synchronous control of each H-bridge transmitter module. Simultaneously, main control module 1 also connects to the gates of each IGBT switch via I / O ports to control the activation and deactivation of each high-voltage clamping unit; and connects to the control terminal of the topology switching switch via another set of I / O ports to control the series connection status between the AC output terminals of each H-bridge transmitter module.

[0039] The main control module 1 is also connected to each current sensor through the ADC sampling channel to collect the current waveform of the transmitting coil 31 in real time and realize closed-loop current monitoring; it is connected to each A / D acquisition module through SPI or parallel interface to collect the secondary field signal induced by the receiving coil; and it is connected to the host computer through communication interface (such as UART, CAN or Ethernet) to receive the operating parameters input by the user and transmit the collected data back.

[0040] Each H-bridge transmitter module has an independent DC bus input and a bipolar AC output. The DC bus input of each H-bridge transmitter module is connected in parallel with its corresponding independent power supply unit; the AC outputs of each H-bridge transmitter module are interconnected through a topology switch.

[0041] Specifically, the i-th H-bridge transmitter module (i=1,2,…,N) contains four transistors, forming a standard H-bridge inverter topology. Each H-bridge transmitter module includes a first half-bridge branch and a second half-bridge branch. The first half-bridge branch includes transistors Q1 and Q2 connected in series, and the second half-bridge branch includes transistors Q3 and Q4 connected in series. The series connection node of transistors Q1 and Q2 in the first H-bridge transmitter module is connected to one end of the transmitter coil via a first connection line. A topology switching switch is provided on the first connection line. The series connection node of transistors Q3 and Q4 is connected to the first half-bridge branch of the next connected H-bridge transmitter module. The series connection node of transistors Q3 and Q4 in the N-th H-bridge transmitter module is connected to the other end of the transmitter coil. A topology switching switch is provided between the series connection node of transistors Q3 and Q4 in the remaining H-bridge transmitter modules and the first connection line.

[0042] When the first diagonal switching transistors of each H-bridge transmitting module are simultaneously turned on under the control signal PWM-A, the transmitting current flows through the transmitting coil 31 in the forward direction; when the second diagonal switching transistors of each H-bridge transmitting module are simultaneously turned on under the control signal PWM-B, the transmitting current flows through the transmitting coil 31 in the reverse direction, thereby realizing bipolar pulse transmission.

[0043] The mode switching switch group includes two types: power supply switching switch and topology switching switch.

[0044] Power supply switching switch: Located between the IGBT switching transistor of each high-voltage clamping unit and the DC bus of the corresponding H-bridge transmitter module. Specifically, the i-th power supply switching switch is the i-th IGBT switching transistor, whose gate is controlled by the main control module 1, and is used to selectively connect or disconnect the i-th clamping capacitor bank. When the i-th IGBT switching transistor is turned on, the i-th high-voltage clamping unit is put into operation; when the i-th IGBT switching transistor is turned off, the i-th high-voltage clamping unit is disconnected from the circuit.

[0045] Topology switching switches are located between the AC output terminals of adjacent H-bridge transmitter modules. When all topology switching switches are closed, the AC output terminals of the N H-bridge transmitter modules are connected in series, with the first end of each series connection connected to one end of the transmitter coil 31 and the last end connected to the other end of the transmitter coil 31. When all topology switching switches are open, the AC output terminals of each H-bridge transmitter module are isolated from each other.

[0046] The mode switching switch group, controlled by the main control module, switches between any one or a combination of the following operating states among the N H-bridge transmitting modules, including: Independent operating mode: Only a single H-bridge transmitter module is in operation, corresponding to a single DC-DC boost module for power supply; Series superposition mode: The AC output terminals of 2-K H-bridge transmitter modules are connected in series, and the bus voltages of the series modules are superimposed for output.

[0047] The series superposition mode refers to connecting the AC output terminals of 2 to K H-bridge transmitting modules in series, so that the bus voltage of each module is superimposed on the transmitting coil 31, thereby obtaining a multiplied driving voltage and transmitting magnetic moment. This mode is the core working method for achieving deep-depth exploration in this embodiment. By controlling the number of modules connected in series, the voltage can be increased stepwise from 2 to K times, and the transmitting magnetic moment can be increased stepwise accordingly, which is suitable for medium-deep to ultra-deep geological exploration.

[0048] In this embodiment, the tandem superposition mode does not exist in isolation, but together with the independent operating mode, it constitutes a complete N-level magnetic moment pulse emission sequence. The main control module 1 can execute the complete sequence from the independent operating mode to the Nth tandem superposition mode in a single excitation pulse period T according to the preset time slice allocation, or it can select any one or any combination of operating modes for emission according to the detection requirements.

[0049] Based on the above-described embodiment of the H-bridge transmitting module, a high-voltage, high-power towed transient electromagnetic detection method is provided, comprising the following steps: The host computer inputs the voltage parameters, number of transmission cycles, and transmission frequency of each DC-DC boost module and transmits them to the main control module. The main control module adjusts the output voltage of each DC-DC boost module according to the input voltage parameters and adjusts the frequency and duty cycle of the transmission waveform according to the input transmission frequency f. The main control module initiates the current detection process by continuously collecting the current magnitude of the transmitting coil through a current sensor installed in the transmitting circuit. Within one excitation pulse period T, according to a preset multi-magnetic moment mode sequence, perform magnetic moment pulse waveform transmission including 1 to K different peak currents, where K is a positive integer and 2≤K≤N, N is the total number of H-bridge transmission modules, and the peak current of each mode increases sequentially or changes according to a preset sequence; Determine whether the transmission of all preset magnetic moment pulse waveforms is completed; if yes, the operation ends, otherwise repeat the multi-mode sequence transmission.

[0050] Within one excitation pulse period T, according to a preset multi-magnetic moment mode sequence, perform magnetic moment pulse waveform transmission including 1 to K different peak currents, where K is a positive integer and 2≤K≤N, N is the total number of H-bridge transmission modules, and the peak current of each mode increases sequentially or changes according to a preset sequence, including: In this embodiment, within one complete excitation pulse period T, the main control module controls part or all of the N H-bridge transmission modules to sequentially perform K types of magnetic moment pulse waveform transmission with different peak currents in a series topology according to the preset multi-magnetic moment mode sequence (2≤K≤N, N is the total number of H-bridge transmission modules). The peak current of each mode increases sequentially, or changes in a preset non-arithmetic sequence according to actual detection requirements, so as to realize gradient detection from shallow to deep layers and from low resolution to high resolution.

[0051] Different from the aforementioned single-mode transmission scheme, this embodiment adopts a time slice rotation control strategy, which evenly divides the entire excitation pulse period T into 2K time slices of equal length, and the length of each time slice is T / (2K). The first K time slices are used for the positive polarity pulse transmission sequence, and the last K time slices are used for the negative polarity pulse transmission sequence. One magnetic moment mode (that is, a specific number of H-bridge transmission modules are put into operation in series) is executed in each time slice, so as to complete the full positive and negative bipolar transmission of all K modes within one period.

[0052] Through this multi-mode sequence transmission method, the main control module can obtain K sets of secondary field attenuation curves at different detection depths within a single excitation pulse period, which greatly improves the detection efficiency and information richness, and is especially suitable for mobile towed rapid survey detection and multi-target identification under complex geological conditions.

[0053] Within the positive polarity half-period (0≤ t<T / 2), the main control module 1 sequentially performs K times of positive polarity magnetic moment pulse transmission in the order from the 1st mode to the Kth mode, and each mode switches according to the preset time slice boundary. In an example, it includes: the 1st mode: only 1 H-bridge transmission module is put into operation, corresponding to 1 DC-DC boost module for power supply; the 2nd mode: 2 H-bridge transmission modules are put into operation, corresponding to 2 DC-DC boost modules for power supply; and so on, the Kth mode: K H-bridge transmission modules are put into operation, corresponding to K DC-DC boost modules for power supply.

[0054] During the time slice of mode k, main control module 1 executes the following control steps: Based on the current mode number k, main control module 1 determines that the H-bridge transmitter modules that need to be put into operation are the 1st to the kth H-bridge transmitter modules, see [link / reference]. Figure 5 As shown, from bottom to top, these are the 1st to kth H-bridge transmitter modules. First, the 1st to kth DC-DC boost modules are started and output a preset voltage, while the (k+1)th to Nth DC-DC boost modules remain in standby mode. Then, the topology switching switches of the 1st to kth H-bridge transmitter modules are closed, connecting their AC output terminals in series. Next, the corresponding IGBT switches (clamping switches) are closed, connecting the corresponding clamping capacitor banks to their respective DC buses. Finally, it is ensured that the last Nk H-bridge transmitter modules are not connected to a series link.

[0055] During the rapid current rise phase: The main control module 1 synchronously sends PWM-A drive signals through the first to the i-th PWM drive modules, causing the first diagonal switching transistors in each H-bridge transmitting module to conduct simultaneously. Since the AC output terminals of each H-bridge transmitting module are connected in series, the output voltages of each H-bridge transmitting module are superimposed across the transmitting coil 31, and the total drive voltage reaches [value missing]. At the same time, the charge stored in each clamping capacitor group is rapidly released, providing additional instantaneous drive current to the transmitting coil 31, guiding the transmitting current to rise rapidly.

[0056] The system checks whether the transmitting current has risen to a preset peak value. If not, the check is repeated; if so, the next step is initiated. The determination is based on whether the real-time current parameter collected by the current sensor has reached the preset peak value of the current mode. The k-th current sensor continuously collects the real-time current value in the transmitting coil 31. The main control module 1 continuously compares the current value of the k-th current sensor with the preset peak value of the current mode as the single-module reference peak current. If the transmitting current has reached its peak value, the main control module 1 immediately controls the first to the k-th IGBT switches to simultaneously disconnect, disconnecting each clamping capacitor group from the corresponding DC bus. Subsequently, the first to the k-th DC-DC boost modules jointly maintain the voltage of each bus, and the current in the transmitting coil 31 stabilizes near the peak value, entering the flat-top maintenance phase.

[0057] During the flat-top maintenance phase, the main control module 1 continues to monitor the transmission current through various current sensors. When the transmission current begins to decrease, it determines that the drive signal PWM-A has ended and the first diagonal switch of each H-bridge transmitter module has been turned off.

[0058] When the control signal PWM-A ends, the circuit current flows through the body diode of the corresponding clamping switch's IGBT switching transistor into the corresponding k clamping capacitor groups. Each clamping capacitor group applies a reverse clamping voltage across the transmitting coil, causing the transmitting coil current to drop rapidly. After the drive signal PWM-A ends, the transmitting coil 31 acts as an inductive load, and its current cannot change abruptly. The freewheeling current flows through the internal anti-parallel body diodes of each IGBT switching transistor into the corresponding clamping capacitor groups. At this time, each clamping capacitor group generates a reverse voltage on its corresponding DC bus. Since the AC output terminals of each H-bridge transmitting module are connected in series, the reverse voltages are superimposed across the transmitting coil 31, forcing the current in the transmitting coil 31 to rapidly return to zero at an extremely high rate of decrease.

[0059] After the clamping shutdown action is completed, the main control module 1 controls the fifth switch 32 to close, connecting the damping resistor 30 to both ends of the transmitting coil 31 to absorb residual energy and suppress possible current overshoot and tail oscillation. After the damping continues for a preset short time, the main control module 1 controls the fifth switch 32 to open.

[0060] The main control module 1 starts the receiving channel (including receiving coil, preamplifier and A / D acquisition module) to acquire secondary field signals, and continuously compares the current timing value t of the internal timer with the preset end time of the current mode. It determines that the signal acquisition is complete, ends the transmission of the k-th mode, and prepares to switch to the next mode.

[0061] If the current mode number k is less than K, then the main control module 1 performs a mode switching operation and begins transmission in mode k+1. All switching actions must be completed within a very short time at the boundary between two adjacent time slices to ensure seamless transitions between modes.

[0062] After completing the transmission of K modes in the positive half-cycle, the main control module 1 executes the negative multi-magnetic moment mode sequence transmission in the second half-cycle (T / 2 ≤ t < T). The negative transmission sequence is completely symmetrical to the positive transmission sequence, the difference being that the second diagonal switch in each H-bridge transmission module is driven to conduct by the control signal PWM-B, and the direction of the current flowing through the transmission coil 31 is opposite to that of the positive polarity.

[0063] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A high-voltage, high-power towed transient electromagnetic detection device, characterized in that, include: The main control module is used to generate variable frequency and variable duty cycle PWM control signals and coordinate the timing logic of the entire device; N H-bridge transmitter modules, each with an independent DC bus input terminal and a bipolar AC output terminal. The AC output terminals of each H-bridge transmitter module can be configured to be connected in series and drive the same transmitter coil together through a mode switching switch group. N independent power supply units are connected to the DC bus input terminals of the N H-bridge transmitter modules respectively. Each power supply unit includes a DC-DC boost module and its corresponding protection diode, which are used to provide an independently adjustable bus voltage to the corresponding H-bridge transmitter module. N high-voltage clamping units are connected in parallel to both ends of the DC bus of the N H-bridge transmitting modules. Each high-voltage clamping unit includes a clamping capacitor bank and an IGBT switch connected in series. The IGBT switch has an anti-parallel body diode, which is used to guide the coil freewheeling current to the clamping capacitor bank through the body diode to achieve voltage clamping during the current turn-off phase. The mode switching switch group includes: IGBT switching transistors, which are located between each high-voltage clamping unit and the corresponding H-bridge transmitter module; A topology switching switch is installed between the AC output terminals of adjacent H-bridge transmitter modules to selectively configure the outputs of each H-bridge transmitter module as a series superposition combination. The transmitting coil is connected to the output terminal of the H-bridge transmitting module or a series combination, and is used to generate an excitation magnetic field based on the combined bipolar transmitting current.

2. The high-voltage, high-power towed transient electromagnetic detection device according to claim 1, characterized in that, The mode switching switch group, controlled by the main control module, switches between any one or a combination of the following operating states among the N H-bridge transmitting modules: Independent operating mode: Only a single H-bridge transmitter module is in operation, corresponding to a single DC-DC boost module for power supply; Series superposition mode: The AC output terminals of 2-K H-bridge transmitter modules are connected in series, and the bus voltages of the series modules are superimposed for output.

3. The high-voltage, high-power towed transient electromagnetic detection device according to claim 1, characterized in that, It also includes a damping circuit, comprising a damping resistor connected in series and a control switch, the damping circuit being connected in parallel across the transmitting coil.

4. The high-voltage, high-power towed transient electromagnetic detection device according to claim 1, characterized in that, The bus voltage of each DC-DC boost module is independently adjustable. Under different magnetic moment modes, the main control module can continuously or finely adjust the transmitting magnetic moment by adjusting the number of DC-DC boost modules in operation and the voltage setting value of each DC-DC boost module, combined with the series topology configuration of the H-bridge transmitting module.

5. A high-voltage, high-power towed transient electromagnetic detection device according to claim 1, characterized in that, Each H-bridge transmitter module includes a first half-bridge branch and a second half-bridge branch. The first half-bridge branch includes transistors Q1 and Q2 connected in series, and the second half-bridge branch includes transistors Q3 and Q4 connected in series. The series connection node of transistors Q1 and Q2 of the first H-bridge transmitter module is connected to one end of the transmitter coil via a first connection line. A topology control switch is provided on the first connection line. The series connection node of transistors Q3 and Q4 is connected to the first half-bridge branch of the next connected H-bridge transmitter module. The series connection node of transistors Q3 and Q4 of the Nth H-bridge transmitter module is connected to the other end of the transmitter coil. A topology control switch is provided between the series connection node of transistors Q3 and Q4 of the remaining H-bridge transmitter modules and the first connection line.

6. A high-voltage, high-power towed transient electromagnetic detection method, characterized in that, Includes the following steps: The host computer inputs the voltage parameters, number of transmission cycles, and transmission frequency of each DC-DC boost module and transmits them to the main control module. The main control module adjusts the output voltage of each DC-DC boost module according to the input voltage parameters and adjusts the frequency and duty cycle of the transmission waveform according to the input transmission frequency f. The main control module initiates the current detection process by continuously collecting the current magnitude of the transmitting coil through a current sensor installed in the transmitting circuit. Within one excitation pulse period T, according to the preset multi-magnetic moment mode sequence, magnetic moment pulse waveforms containing 1-K different peak currents are emitted, where K is a positive integer and 2≤K≤N, N is the total number of H-bridge transmitting modules, and the peak current of each mode increases sequentially or changes according to the preset sequence. Determine whether all preset magnetic moment pulse waveforms have been transmitted. If so, the operation ends; otherwise, repeat the multi-mode sequence transmission.

7. The high-voltage, high-power towed transient electromagnetic detection method according to claim 6, characterized in that, In the multi-magnetic moment mode sequence transmission, the transmission mode is switched sequentially for each magnetic moment pulse transmission mode in the following manner: Mode 1: Only one H-bridge transmitter module is in operation, corresponding to a power supply from one DC-DC boost module; Mode 2: Two H-bridge transmitter modules are in operation, corresponding to two DC-DC boost modules for power supply; Similarly, in the Kth mode: K H-bridge transmitter modules are put into operation, corresponding to K DC-DC boost modules for power supply.

8. The high-voltage, high-power towed transient electromagnetic detection method according to claim 7, characterized in that, The transmission time of the kth magnetic moment pulse emission mode is T / (2k), and the process includes: According to the current mode number, the main control module controls the corresponding IGBT switch and topology control switch to close, connects k DC-DC boost modules and k high-voltage clamping modules into the circuit at the same time, and configures k H-bridge transmitter modules as series output, where k is a positive integer and 1≤k≤K; The PWM drive module emits a PWM-A signal to drive the corresponding H-bridge transmitter module, causing the first diagonal switch in each H-bridge transmitter module to close and enter the rapid current rise phase. Determine whether the transmission current has risen to the preset peak value. If not, repeat the determination. If yes, proceed to the next step. The determination is based on whether the real-time current parameters collected by the current sensor have reached the preset peak value of the current mode. The main control module controls the corresponding clamping switch to open, and the k DC-DC boost modules currently in operation jointly maintain the transmit current to enter the flat-top phase; Determine whether the control signal PWM-A has ended. If not, repeat the determination. If yes, proceed to the next step. The determination is based on whether the real-time current parameter collected by the current sensor has started to decrease. When the control signal PWM-A ends, the circuit current flows through the body diode of the corresponding clamping switch IGBT switching transistor into the corresponding k clamping capacitor groups. Each clamping capacitor group applies a reverse clamping voltage across the transmitting coil, causing the transmitting coil current to drop rapidly. The main control module controls the damping switch to close, so that the damping resistor is connected to the transmitting coil to suppress current overshoot and tail oscillation.

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