A time domain electromagnetic electric source emission system

Abstract

The present application relates to the field of electromagnetic detection in geophysical exploration, in particular to a time-domain electromagnetic electric source transmitting system. The purpose is to achieve impedance matching of the electric source equivalent load and to effectively suppress the power ripple generated by the DC power bus. It includes a high-power DC power supply, a transmitting host and a fractional-order ripple suppression circuit, wherein the high-power DC power supply provides three-phase AC power; the transmitting host includes an H-bridge inverter circuit, which is connected to the transmitting cable and alternately conducts under the control of a set of complementary pulse width modulation signals to generate a transmitting current in the loop formed by the transmitting cable and the ground; the fractional-order ripple suppression circuit includes a matching capacitor and a first fractional-order device in series, which are connected in parallel at both ends of the H-bridge inverter circuit. It is beneficial to improve the performance of the time-domain electromagnetic electric source transmitting system.

Description

Technical Field

[0001] The present application relates to the field of electromagnetic detection for geophysical exploration, and in particular to a time-domain electromagnetic electrical source emission system. Background Art

[0002] The time-domain electromagnetic method is a geophysical exploration method that uses the principle of electromagnetic induction to detect underground geological structures. The electric source transmission method can provide greater transmission power and can perform multi-point area signal acquisition on both sides of the field source. It has the characteristics of large detection depth and high work efficiency and has been widely used. However, because the electric source transmission load is an equivalent model of a long grounded wire and the earth in series, its parameters are uncertain and difficult to measure, making it difficult to accurately calibrate and impedance match it. At the same time, because the DC side of the power supply of the electric source transmitter is obtained by AC-DC rectification of three-phase AC, and the power is relatively high, it causes severe ripple oscillations, which has a significant impact on the waveform quality of the flat-top section of the transmission current. Summary of the Invention

[0003] In order to solve the problem that the existing technology cannot achieve impedance matching of the electric source transmitter and ripple suppression of the transmission waveform, the present application provides a time-domain electromagnetic electric source transmission system.

[0004] The implementation of the embodiment of this application is as follows:

[0005] A time-domain electromagnetic electrical source emission system, the system comprising:

[0006] A high-power DC power supply, a transmitting host and a fractional-order ripple suppression circuit, wherein the high-power DC power supply provides three-phase AC power;

[0007] The transmitting host includes an H-bridge inverter circuit, which is connected to the transmitting cable and alternately conducts under the control of a set of complementary pulse width modulation signals to generate a transmitting current in a loop formed by the transmitting cable and the ground;

[0008] The fractional-order ripple suppression circuit includes a matching capacitor and a first fractional-order device connected in series, which are connected in parallel at both ends of the H-bridge inverter circuit.

[0009] Furthermore, a fractional-order impedance matching circuit is connected in parallel to the loop formed by the transmitting cable and the ground, and the fractional-order impedance matching circuit includes a second fractional-order device.

[0010] Furthermore, the first fractional-order device includes: a first MOSFET switching device, a second MOSFET switching device, a fractional-order inductor and a fractional-order capacitor, wherein the S pole of the first MOSFET switching device and the D pole of the second MOSFET switching device are connected to form a MOSFET switching device group, the two ends of the MOSFET switching device group are connected to the two ends of a high-power DC power supply, the S pole of the second MOSFET switching device is connected to the first end of the fractional-order capacitor, the second end of the fractional-order capacitor is connected to the first end of the fractional-order inductor, and the second end of the fractional-order inductor is connected to the S pole of the first MOSFET switching device.

[0011] Furthermore, the second fractional-order device includes:

[0012] A power supply, a first MOSFET switching device, a second MOSFET switching device, a fractional-order inductor, a voltage divider protection resistor, and a fractional-order capacitor, wherein the S pole of the first MOSFET switching device and the D pole of the second MOSFET switching device are connected to form a MOSFET switching device group, the power supply is connected to both ends of the MOSFET switching device group through the voltage divider protection resistor, the S pole of the first MOSFET switching device is connected to the first end of the fractional-order capacitor, the second end of the fractional-order capacitor is connected to the first end of the fractional-order inductor, and the second end of the fractional-order inductor is connected to the S pole of the first MOSFET switching device.

[0013] Furthermore, the transmitting host further comprises a logic control circuit, an isolation drive circuit and a constant voltage clamp circuit, wherein the logic control circuit generates a pulse width modulation signal with a fixed frequency and duty cycle to the isolation drive circuit according to instructions;

[0014] The isolation drive circuit outputs pulse width modulation signals to the four IGBT bridge arms of the H-bridge inverter circuit to complete the drive control of the IGBT bridge arms;

[0015] The constant voltage clamp circuit is a plurality of groups of TVS diodes connected in series and connected in parallel on one side of the H-bridge inverter circuit.

[0016] Furthermore, the logic control circuit is also used to generate a signal to the isolation drive circuit according to instructions; the isolation drive circuit outputs a pulse width modulation signal to the control end of the fractional-order ripple suppression circuit to adjust the order α of the fractional-order capacitor in the fractional-order ripple suppression circuit.

[0017] Furthermore, the logic control circuit is also used to generate a signal to the isolation drive circuit according to the instruction; the isolation drive circuit outputs a pulse width modulation signal to the control end of the fractional-order impedance matching circuit, adjusts the order α of the fractional-order constituent capacitor in the fractional-order impedance matching circuit, so that the fractional-order constituent capacitor presents a negative capacitance, and minimizes the difference between the absolute value of the negative capacitance and the parasitic capacitance of the equivalent load.

[0018] The embodiments of this application have at least the following beneficial effects: They improve the performance of the electrical source transmission system and the quality of the transmitted waveform. A fractional-order ripple suppression circuit is used to suppress the ripple generated by the high-power DC transmitter power supply. A fractional-order impedance matching circuit is used to achieve accurate and controllable impedance matching for the complex conditions of the transmitter cable and the ground load, fundamentally controlling the waveform quality of the transmitted current. This application is beneficial for improving the detection performance of the time-domain electromagnetic transmission system and further enhancing the accuracy and reliability of subsequent data interpretation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A structural block diagram of a time-domain electromagnetic electrical source transmission system provided in an embodiment of the present application;

[0020] Figure 2 A circuit schematic diagram of a fractional-order ripple suppression circuit and an H-bridge inverter circuit provided in an embodiment of the present application;

[0021] Figure 3 A structural relationship diagram of a fractional-order impedance matching circuit and a load provided in an embodiment of the present application;

[0022] Figure 4 A circuit schematic diagram of a fractional-order impedance matching circuit provided in an embodiment of the present application;

[0023] Figure 5 A waveform quality comparison diagram of the emission current waveform (a) of a conventional electrical source provided in an embodiment of the present application and the emission waveform (b) of the system of the present application; DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0025] See also Figure 1 Combine Figure 2 As shown, a time-domain electromagnetic electric source transmission system includes a high-power DC power supply, a transmitting host and a fractional-order ripple suppression circuit;

[0026] The high-power DC power supply provides three-phase AC power; the transmitter host includes an H-bridge inverter circuit, which is connected to the transmitter cable and alternately conducts under the control of a set of complementary pulse width modulation signals to generate a transmission current in the loop formed by the transmitter cable and the ground;

[0027] The fractional-order ripple suppression circuit includes a matching capacitor and a first fractional-order device connected in series, which are connected in parallel at both ends of the H-bridge inverter circuit.

[0028] The high-power DC power supply uses an industrial frequency generator to provide 380V three-phase AC power to the system. First, 510V DC power is obtained through three-phase rectification, which is then inverted into high-frequency AC power by switching devices. Then, through transformers, rectification and filtering, an adjustable high-power DC power of up to 2000V is achieved.

[0029] The transmitter host is the core component of the transmitter system, responsible for generating the required current pulses. Its main parameters include maximum output voltage, maximum output current, transmission frequency, and transmission waveform.

[0030] In an embodiment of the present application, the transmitter host includes an H-bridge inverter circuit, a logic control circuit, and an isolation drive circuit. The H-bridge inverter circuit, serving as the primary transmitter circuit, integrates four IGBT bridge arms (Q1-Q4). These arms alternately conduct under the control of a set of complementary pulse-width modulation signals, generating a transmission current in a loop formed between the transmitter cable and the ground. The logic control circuit generates a pulse-width modulation signal with a fixed frequency and duty cycle according to instructions and sends it to the isolation drive circuit. The isolation drive circuit then outputs the pulse-width modulation signal to the four IGBTs in the H-bridge inverter circuit, completing the drive control of the four IGBTs. A constant-voltage clamp circuit is also provided, connected in parallel to one side of the H-bridge inverter circuit. The constant-voltage clamp circuit comprises a series connection of multiple sets of TVS diodes.

[0031] The four IGBT bridge arms are: IGBT tube Q1, IGBT tube Q2, IGBT tube Q3 and IGBT tube Q4. IGBT tube Q1 and IGBT tube Q3 are connected in series, IGBT tube Q2 and IGBT tube Q4 are connected in series, and a load is connected between the common end between IGBT tube Q1 and IGBT tube Q3 and the common end between IGBT tube Q2 and IGBT tube Q4. The load is the loop formed by the transmitting cable and the ground.

[0032] In one embodiment, the fractional-order ripple suppression circuit is connected in parallel at both ends of the H-bridge inverter circuit, including a first matching capacitor C1 and a first fractional-order device connected in series, the first fractional-order device including: a first MOSFET switch device , the second MOSFET switching device , fractional order inductance and fractional order capacitors , wherein the first MOSFET switching device The S-pole of the second MOSFET switching device The D pole of the MOSFET switch device group is connected to the two ends of the high-power DC power supply, and the second MOSFET switch device The S pole of the capacitor is connected to the fractional order The first end of the fractional order capacitor The second end of the fractional step is connected to form an inductor The first end of the fractional order constitutes the inductor The second end is connected to the first MOSFET switch device The S pole.

[0033] First MOSFET switching device , the second MOSFET switching device , fractional order capacitors And fractional order form inductance The on / off switching of the MOSFET is controlled by a control signal applied to its G terminal. α is the order of the fractional capacitor. The port characteristics of the fractional capacitor, namely the phase difference between the port voltage and the current flowing through it, are directly related to the order α. This means that the circuit properties can be changed by adjusting the order.

[0034] In one embodiment, a fractional-order impedance matching circuit is connected in parallel to the loop formed by the transmitting cable and the ground, and the fractional-order impedance matching circuit includes a second fractional-order device.

[0035] See also Figure 3 Combine Figure 4 As shown, the fractional-order impedance matching circuit is also implemented using fractional-order capacitors, including a second fractional-order device ( Figure 3 The difference between the structure of the first fractional-order device and the second fractional-order device is that the power supply, the first MOSFET switch device , the second MOSFET switching device , voltage divider protection resistor , fractional order inductance and fractional order capacitors , wherein the first MOSFET switching device The S-pole of the second MOSFET switching device The D pole is connected to form a MOSFET switch device group, and the power supply is connected through a voltage divider protection resistor. Connected to both ends of the MOSFET switch device group, the second MOSFET switch device The S pole of the capacitor is connected to the fractional order The first end of the fractional order capacitor The second end of the fractional step is connected to form an inductor The first end of the fractional order constitutes the inductor The second end is connected to the first MOSFET switch device The S pole.

[0036] The difference from the first fractional-order device is that the second fractional-order device requires an independent power supply and voltage divider protection resistor. .

[0037] The actual load of the electrical source transmitter is composed of the transmitting cable and the ground. The equivalent circuit can be regarded as the resistance of the transmitting cable. ,inductance The circuit structure connected in series with the equivalent impedance of the earth. The equivalent circuit structure of the earth includes the equivalent resistance , equivalent resistance and equivalent capacitance Therefore, the characteristics of fractional-order devices can be utilized to connect the second fractional-order device in parallel with the entire load. By controlling the order α, accurate and adjustable impedance matching with the load can be achieved. By matching, the overall inductance and capacitance of the load can be reduced, thereby further controlling the quality of the transmitted waveform.

[0038] The relationship between the voltage and current of the fractional-order capacitor is as follows:

[0039] ,

[0040] in is the order of the fractional-order capacitors. is the current through the fractional capacitor, is the voltage across the capacitor that constitutes the fractional order, is the capacitance of the fractional capacitor. The fractional capacitor and port characteristics, that is, the phase difference between the port voltage and the current flowing through it, are directly related to the order α of the fractional capacitor. In other words, the circuit properties can be changed by adjusting the order.

[0041] Based on this characteristic, each link in the fractional-order device can be accurately constructed and fine-tuned according to the actual needs of the transmission system.

[0042] The fractional negative capacitor used in the fractional ripple suppression circuit (when When , the fractional order capacitor is called negative capacitance, referred to as NOC). is the equivalent capacitance of negative capacitance. Since negative capacitance exhibits characteristics similar to inductance in AC, its equivalent capacitance is The value is opposite to the traditional capacitor. According to the equivalent formula of capacitor series, NOC is equivalent to a capacitor with a value of The matching capacitors are connected in series, and the equivalent capacitance of the two in series is for:

[0043] ,

[0044] Traditional electric source transmission systems connect a capacitor in parallel between the DC power supply and the H-bridge inverter circuit to suppress ripple oscillations, but this absorption is incomplete, and the capacitor's value cannot be precisely controlled. Fractional-order capacitors, on the other hand, offer the advantage of controllable properties. By changing the control logic of the two MOSFET switches, the order α can be adjusted. This order α can be adjusted based on actual circuit requirements to achieve optimal suppression. Specifically, a logic control circuit generates a signal to an isolation drive circuit based on instructions; the isolation drive circuit outputs a pulse-width modulated signal to the control terminal of the fractional-order ripple suppression circuit, thereby adjusting the order α of the fractional-order capacitors in the fractional-order ripple suppression circuit.

[0045] The fractional-order impedance matching circuit also utilizes the characteristics of fractional-order devices. It selects a fractional-order negative capacitor when α = -1 and connects it in parallel at both ends of the equivalent load composed of the transmitting cable and the ground (i.e., at the output port of the H-bridge inverter circuit). According to the capacitor parallel formula:

[0046] ,

[0047] When the equivalent capacitance of the negative capacitor Parasitic capacitance of the equivalent load formed by the transmission cable and the ground When close, impedance matching of the load can be achieved, thereby achieving the purpose of suppressing early oscillation and optimizing the quality of the transmitted waveform. In actual operation, the difference between the absolute value of the negative capacitance and the parasitic capacitance of the equivalent load is minimized to achieve the purpose of the two being close. Specifically, a signal is generated to the isolation drive circuit according to an instruction by a logic control circuit; the isolation drive circuit outputs a pulse width modulation signal to the control end of the fractional-order impedance matching circuit, and the order α of the fractional-order constituent capacitor in the fractional-order impedance matching circuit is adjusted so that the fractional-order constituent capacitor presents a negative capacitance, and the difference between the absolute value of the negative capacitance and the parasitic capacitance of the equivalent load is minimized.

[0048] In order to further verify the effect of the time domain electromagnetic power source emission system provided in the embodiment of the present application, the emission current is measured and the emission current waveform comparison diagram is obtained as shown in FIG. Figure 5 (a) and Figure 5 (b) in which see Figure 5 (a) The waveform of the traditional transmitting system has obvious ripple oscillation in the flat-top section, and there is a large amplitude oscillation at the moment of shutdown. In comparison, see Figure 5 As shown in (b), the waveform of the system in the embodiment of the present application tends to be stable, the degree of oscillation relief and suppression is obvious, and the quality of the current waveform is significantly improved.

[0049] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A time domain electromagnetic electric source emission system, characterized in that: The system includes: a high-power DC power supply, a transmitting host and a fractional-order ripple suppression circuit, wherein the high-power DC power supply provides three-phase AC power; The transmitting host includes an H-bridge inverter circuit, which is connected to the transmitting cable and alternately conducts under the control of a set of complementary pulse width modulation signals to generate a transmitting current in a loop formed by the transmitting cable and the ground; The fractional-order ripple suppression circuit includes a matching capacitor and a first fractional-order device connected in series, and connected in parallel at both ends of the H-bridge inverter circuit; A fractional-order impedance matching circuit is connected in parallel to the loop formed by the transmitting cable and the ground, and the fractional-order impedance matching circuit includes a second fractional-order device; The transmitting host further includes a logic control circuit and an isolation drive circuit, wherein the logic control circuit is configured to generate a signal to the isolation drive circuit according to an instruction, and the isolation drive circuit outputs a pulse width modulation signal to the control end of the fractional-order ripple suppression circuit to adjust the order α of the fractional-order capacitor in the fractional-order ripple suppression circuit; The logic control circuit is also used to generate a signal to the isolation drive circuit according to the instruction; the isolation drive circuit outputs a pulse width modulation signal to the control end of the fractional-order impedance matching circuit, adjusts the order α of the fractional-order capacitor in the fractional-order impedance matching circuit, so that the fractional-order capacitor presents a negative capacitance, and minimizes the difference between the absolute value of the negative capacitance and the parasitic capacitance of the equivalent load.

2. A time domain electromagnetic power source emission system according to claim 1, characterized in that: The first fractional-order device includes: a first MOSFET switching device, a second MOSFET switching device, a fractional-order inductor and a fractional-order capacitor, wherein the S pole of the first MOSFET switching device and the D pole of the second MOSFET switching device are connected to form a MOSFET switching device group, the two ends of the MOSFET switching device group are connected to the two ends of a high-power DC power supply, the S pole of the second MOSFET switching device is connected to the first end of the fractional-order capacitor, the second end of the fractional-order capacitor is connected to the first end of the fractional-order inductor, and the second end of the fractional-order inductor is connected to the S pole of the first MOSFET switching device.

3. The time domain electromagnetic electric source emission system according to claim 1, characterized in that: The second fractional-order device includes: A power supply, a first MOSFET switching device, a second MOSFET switching device, a fractional-order inductor, a voltage divider protection resistor, and a fractional-order capacitor, wherein the S pole of the first MOSFET switching device and the D pole of the second MOSFET switching device are connected to form a MOSFET switching device group, the power supply is connected to both ends of the MOSFET switching device group through the voltage divider protection resistor, the S pole of the first MOSFET switching device is connected to the first end of the fractional-order capacitor, the second end of the fractional-order capacitor is connected to the first end of the fractional-order inductor, and the second end of the fractional-order inductor is connected to the S pole of the first MOSFET switching device.

4. A time domain electromagnetic electric source emission system according to claim 2 or 3, characterized in that: The transmitting host also includes a constant voltage clamp circuit, and the logic control circuit generates a pulse width modulation signal with a fixed frequency and duty cycle to the isolation drive circuit according to the instruction; The isolation drive circuit outputs pulse width modulation signals to the four IGBT bridge arms of the H-bridge inverter circuit to complete the drive control of the IGBT bridge arms; The constant voltage clamp circuit is a plurality of groups of TVS diodes connected in series and connected in parallel on one side of the H-bridge inverter circuit.

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