Time-domain electromagnetic electrical source emission system

Abstract

The invention relates to the field of geophysical exploration electromagnetic method detection, in particular to a time domain electromagnetic electrical source emission system. The objective of the invention is to realize impedance matching of an electrical source equivalent load and effective suppression of power supply ripples generated by a direct-current power supply bus. Comprising a high-power direct-current power supply, a transmitting host and a fractional order ripple suppression circuit, and the high-power direct-current power supply provides three-phase alternating current; the transmitting host comprises an H-bridge inverter circuit, the H-bridge inverter circuit is connected with a transmitting cable and is alternately conducted under the control of a group of complementary pulse width modulation signals, and transmitting current is generated in a loop formed by the transmitting cable and the ground; the fractional-order ripple suppression circuit comprises a matching capacitor and a first fractional-order device which are connected in series, and the matching capacitor and the first fractional-order device are connected to the two ends of the H-bridge inverter circuit in parallel. And the performance of the time-domain electromagnetic electrical source emission system can be improved.

Description

Technical Field

[0001] This application relates to the field of electromagnetic method detection in geophysical exploration, and particularly 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. Among them, the electrical source emission method can provide a larger emission power, can perform area signal acquisition at multiple points on both sides of the field source, and has the characteristics of large detection depth and high working efficiency, and has been widely used. However, since the electrical source emission load is an equivalent model of a grounded long wire in series with the earth, its parameters are uncertain and difficult to measure, resulting in difficulty in accurately calibrating and impedance matching. At the same time, since the DC side of the power supply of the electrical source transmitter is obtained by rectifying three-phase alternating current through AC-DC rectification and has a large power, there is serious ripple oscillation, which has a great impact on the waveform quality of the flat top section of the emission current. Summary of the Invention

[0003] Aiming at the problems in the existing technology that it is impossible to achieve impedance matching of the electrical source transmitter and ripple suppression of the emission waveform, this application provides a time-domain electromagnetic electrical source emission system.

[0004] The implementation manner of the embodiment of this application is as follows: A time-domain electromagnetic electrical source emission system, the system includes: A high-power DC power supply, a transmitting host, and a fractional-order ripple suppression circuit. Among them, the high-power DC power supply provides three-phase alternating current; The transmitting host includes an H-bridge inverter circuit, and the H-bridge inverter circuit is connected to the transmitting cable and alternately conducts under the control of a group of complementary pulse width modulation signals, generating an emission current in the loop formed by the transmitting cable and the earth; The fractional-order ripple suppression circuit includes a matching capacitor and a first fractional-order device connected in series, and is connected in parallel across the H-bridge inverter circuit.

[0005] Further, a fractional-order impedance matching circuit is connected in parallel to the loop formed by the transmitting cable and the earth, and the fractional-order impedance matching circuit includes a second fractional-order device.

[0006] Further, the first fractional-order device includes: a first MOSFET switching device, a second MOSFET switching device, a fractional-order forming inductor, and a fractional-order forming capacitor. Among them, the S pole of the first MOSFET switching device is connected to the D pole of the second MOSFET switching device to form a MOSFET switching device group. Both ends of the MOSFET switching device group are connected to both 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 forming capacitor. The second end of the fractional-order forming capacitor is connected to the first end of the fractional-order forming inductor. The second end of the fractional-order forming inductor is connected to the S pole of the first MOSFET switching device.

[0007] Further, the second fractional-order device includes: a power supply, a first MOSFET switching device, a second MOSFET switching device, a fractional-order forming inductor, a voltage-dividing protection resistor, and a fractional-order forming capacitor. Among them, the S pole of the first MOSFET switching device is connected to the D pole of the second MOSFET switching device to form a MOSFET switching device group. The power supply is connected to both ends of the MOSFET switching device group through the voltage-dividing protection resistor. The S pole of the first MOSFET switching device is connected to the first end of the fractional-order forming capacitor. The second end of the fractional-order forming capacitor is connected to the first end of the fractional-order forming inductor. The second end of the fractional-order forming inductor is connected to the S pole of the first MOSFET switching device.

[0008] Further, the transmitting host also includes a logic control circuit, an isolation driving circuit, and a constant-voltage clamping circuit. The logic control circuit generates a pulse-width modulation signal with a fixed frequency and duty cycle according to an instruction to the isolation driving circuit; The isolation driving circuit outputs the pulse-width modulation signal to the four IGBT bridge arms of the H-bridge inverter circuit to complete the driving control of the IGBT bridge arms; The constant-voltage clamping circuit is multiple groups of series-connected TVS diodes connected in parallel on one side of the H-bridge inverter circuit.

[0009] Further, the logic control circuit is also used to generate a signal to the isolation driving circuit according to an instruction; the isolation driving 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 forming capacitor in the fractional-order ripple suppression circuit.

[0010] Further, the logic control circuit is also used to generate a signal to the isolation driving circuit according to an instruction; the isolation driving circuit outputs a pulse-width modulation signal to the control end of the fractional-order impedance matching circuit to adjust the order α of the fractional-order forming capacitor in the fractional-order impedance matching circuit, so that the fractional-order forming capacitor presents a negative capacitance value, and the difference between the absolute value of the negative capacitance value and the parasitic capacitance of the equivalent load is minimized.

[0011] The embodiments of the present application at least have the following beneficial effects: The embodiments of the present application improve the performance of the electrical source emission system and the quality of the emission waveform. A fractional-order ripple suppression circuit is used to suppress the ripple generated by the high-power DC emission power supply; a fractional-order impedance matching circuit is used to achieve accurate and controllable impedance matching for the complex situation of the emission cable and the ground load, fundamentally controlling the waveform quality of the emission current. The present application is beneficial to improving the detection performance of the time-domain electromagnetic emission system and further enhancing the accuracy and reliability of subsequent data interpretation. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural block diagram of a time-domain electromagnetic electrical source emission system provided by an embodiment of the present application; Figure 2 It is a circuit schematic diagram of a fractional-order ripple suppression circuit and an H-bridge inverter circuit provided by an embodiment of the present application; Figure 3 It is a structural relationship diagram of a fractional-order impedance matching circuit and a load provided by an embodiment of the present application; Figure 4 It is a circuit schematic diagram of a fractional-order impedance matching circuit provided by an embodiment of the present application; Figure 5 It is a waveform quality comparison diagram of the traditional electrical source emission current waveform (a) and the emission waveform (b) of the system of the present application provided by an embodiment of the present application; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0014] See Figure 1 Combined with Figure 2 As shown, a time-domain electromagnetic electrical source emission system includes a high-power DC power supply, an emission host and a fractional-order ripple suppression circuit; Among them, the high-power DC power supply provides three-phase alternating current; the emission host includes an H-bridge inverter circuit, and the H-bridge inverter circuit is connected to the emission cable and alternately conducts under the control of a set of complementary pulse width modulation signals, generating an emission current in the loop formed by the emission cable and the ground; The fractional-order ripple suppression circuit includes a matching capacitor and a first fractional-order device connected in series, and is connected in parallel across the H-bridge inverter circuit.

[0015] The high-power DC power supply uses an industrial frequency generator to provide 380V three-phase alternating current to the system. First, 510V direct current is obtained through three-phase rectification, inverted into high-frequency alternating current through a switching device, and then adjustable high-power direct current up to 2000V is achieved through a transformer, rectification and filtering; The transmitting host is the core component of the transmitting system and is responsible for generating the required current pulses. Its main parameters include the maximum output voltage, the maximum output current, the transmission frequency, the transmission waveform, etc.

[0016] In the embodiment of the present application, the transmitting host includes an H-bridge inverter circuit, a logic control circuit, and an isolation drive circuit. Among them, the H-bridge inverter circuit is the main transmitting circuit, integrating four IGBT bridge arms (Q1~Q4), which are alternately turned on under the control of a group of complementary pulse width modulation signals, and generating a transmitting current in the loop formed by the transmitting cable and the ground; 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 then outputs the pulse width modulation signal to the four IGBTs of the H-bridge inverter circuit to complete the drive control of the four IGBTs. And a constant voltage clamping circuit is connected in parallel on one side of the H-bridge inverter circuit, and the constant voltage clamping circuit is a series of multiple groups of TVS diodes in series.

[0017] The four IGBT bridge arms are respectively: IGBT tube Q1, IGBT tube Q2, IGBT tube Q3, and IGBT tube Q4. IGBT tube Q1 and IGBT tube Q3 are in series, IGBT tube Q2 and IGBT tube Q4 are in series, and the common end between IGBT tube Q1 and IGBT tube Q3 is connected to the common end between IGBT tube Q2 and IGBT tube Q4, and the load is the loop formed by the transmitting cable and the ground.

[0018] In one embodiment, the fractional-order ripple suppression circuit is connected in parallel at both ends of the H-bridge inverter circuit, including a series-connected first matching capacitor C1 and a first fractional-order device. The first fractional-order device includes: a first MOSFET switching device and a second MOSFET switching device , a fractional-order formed inductor and a fractional-order formed capacitor . Among them, the S pole of the first MOSFET switching device is connected to the D pole of the second MOSFET switching device to form a MOSFET switching device group. Both ends of the MOSFET switching device group are connected to both 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 connected fractional-order formed capacitor . The second end of the fractional-order formed capacitor is connected to the first end of the fractional-order formed inductor . The second end of the fractional-order formed inductor is connected to the S pole of the first MOSFET switching device .

[0019] The first MOSFET switching device , the second MOSFET switching device , the fractional-order formed capacitor and the fractional-order formed inductor . The on / off of the MOSFET switching device is controlled by the control signal applied to the G pole of the MOSFET switching device. Among them, α is called the order of the fractional-order formed capacitor, and the port characteristics of the fractional-order formed capacitor, that is, the phase difference between the port voltage and the flowing current, are directly related to the order α, that is, the circuit properties can be changed by adjusting the order.

[0020] In one embodiment, a fractional-order impedance matching circuit is connected in parallel with the loop formed by the transmitting cable and the ground, and the fractional-order impedance matching circuit includes a second fractional-order device.

[0021] See Figure 3 in combination with Figure 4 shown, the fractional-order impedance matching circuit is also implemented using a fractional-order capacitor and includes a second fractional-order device ( Figure 3 the device represented by FOC in . The difference from the structure of the second fractional-order device is: the power supply, the first MOSFET switching device , the second MOSFET switching device , the voltage-dividing protection resistor , the fractional-order formed inductor and the fractional-order formed capacitor . The S pole of the first MOSFET switching device is connected to the D pole of the second MOSFET switching device to form a MOSFET switching device group. The power supply is connected to both ends of the MOSFET switching device group through the voltage-dividing protection resistor . The S pole of the second MOSFET switching device is connected to the first end of the connected fractional-order formed capacitor . The second end of the fractional-order formed capacitor is connected to the first end of the fractional-order formed inductor . The second end of the fractional-order formed inductor is connected to the S pole of the first MOSFET switching device .

[0022] The difference from the first fractional-order device is that the second fractional-order device requires an independent power supply and a voltage-dividing protection resistor .

[0023] The actual load of the electrical source transmitting host is jointly constituted by the transmitting cable and the ground. The equivalent circuit can be regarded as a circuit structure in which the resistance , inductance of the transmitting cable and the equivalent impedance of the ground are connected in series. Among them, the equivalent circuit structure of the ground includes an equivalent resistance Equivalent resistance and equivalent capacitance . Therefore, the characteristics of the fractional-order device can be utilized to connect the second fractional-order device in parallel with the load as a whole. By controlling the order α and the load, an accurately adjustable impedance matching can be achieved. By matching, the inductance and capacitance of the load as a whole can be reduced, thereby further achieving the control of the quality of the transmitted waveform.

[0024] The voltage-current relationship of the fractional-order capacitance is as follows: , where is the order of the fractional-order capacitance. is the current passing through the fractional-order capacitance, is the voltage across the fractional-order capacitance, is the capacitance value of the fractional-order capacitance. The fractional-order capacitance and the port characteristics, that is, the phase difference between the port voltage and the flowing current, are directly related to the order α of the fractional-order capacitance, that is, the circuit properties can be changed by adjusting the order.

[0025] Based on this characteristic, each link in the fractional-order device can be accurately constructed and finely adjusted according to the actual working needs of the transmitting system.

[0026] The fractional-order negative capacitance (when , the fractional-order capacitance is called negative capacitance, abbreviated as NOC) used in the fractional-order ripple suppression circuit, is the equivalent capacitance value of the negative capacitance. Since the negative capacitance exhibits characteristics similar to those of an inductor in alternating current, its equivalent capacitance value is numerically opposite to that of a traditional capacitance. According to the equivalent formula for capacitance in series, NOC is connected in series with a matching capacitance with a capacitance value of , and the equivalent capacitance value after their series connection is: , In a traditional electrical source transmitting system, a capacitor is connected in parallel between the DC power supply and the H-bridge inverter circuit to suppress ripple oscillation, but the absorption is not complete, and the capacitance value of the capacitor cannot be accurately controlled. The fractional-order capacitance has the advantage of controllable properties. By changing the control logic of two MOSFET switching tubes, the adjustment of the order α can be achieved. The order α can be adjusted according to the requirements in the actual circuit to achieve the best suppression effect. Specifically, the logic control circuit generates 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 ripple suppression circuit to adjust the order α of the fractional-order capacitance in the fractional-order ripple suppression circuit.

[0027] The fractional - order impedance - matching circuit also utilizes the characteristics of fractional - order devices. When selecting the fractional - order negative capacitance with α = - 1, it is connected in parallel across the entire equivalent load formed by the transmitting cable and the ground (i.e., at the output port of the H - bridge inverter circuit). According to the capacitance parallel - connection formula: , When the equivalent capacitance value of the negative capacitance is close to the parasitic capacitance of the equivalent load formed by the transmitting cable and the ground , impedance matching of the load can be achieved, thereby achieving the purpose of suppressing early oscillations and optimizing the quality of the transmitted waveform. In actual operation, the difference between the absolute value of the negative - capacitance value and the parasitic capacitance of the equivalent load is minimized to achieve the purpose of their closeness. Specifically, the logic control circuit generates a signal according to the instruction to the isolation drive circuit; 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, makes the fractional - order constituent capacitor exhibit a negative - capacitance value, and minimizes the difference between the absolute value of the negative - capacitance value and the parasitic capacitance of the equivalent load.

[0028] To further verify the effect of the time - domain electromagnetic electrical - source transmitting system provided by the embodiments of the present application, the transmitted current is measured in actuality, and the comparison diagram of the transmitted - current waveforms is as shown in Figure 5 (a) and Figure 5 (b) in. Among them, referring to Figure 5 (a), the ripple oscillation in the flat - top section of the waveform of the traditional transmitting system is obvious, and there is a large - amplitude oscillation at the moment of turn - off. In contrast, referring to Figure 5 (b) shown, the waveform of the system of the embodiments of the present application tends to be stable, the degree of oscillation mitigation and suppression is obvious, and the quality of the current waveform is significantly improved.

[0029] The above - mentioned are only the preferred embodiments of the present application and are not used to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A time-domain electromagnetic electrical 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. Among them, the high-power DC power supply provides three-phase alternating current; The transmitting host includes an H-bridge inverter circuit, which is connected to a transmitting cable and conducts alternately under the control of a group of complementary pulse-width modulation signals, generating 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 connected in series, and is connected in parallel across the H-bridge inverter circuit.

2. The time-domain electromagnetic electrical source emission system according to claim 1, characterized in that, A fractional-order impedance matching circuit is connected in parallel to the loop formed by the transmitting cable and the ground. The fractional-order impedance matching circuit includes a second fractional-order device.

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

4. A time-domain electromagnetic electrical source emission system according to claim 2, 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 formed inductor, a voltage-dividing protection resistor, and a fractional-order formed capacitor. Among them, the S pole of the first MOSFET switching device is connected to the D pole of the second MOSFET switching device to form a MOSFET switching device group. The power supply is connected across both ends of the MOSFET switching device group through the voltage-dividing protection resistor. The S pole of the first MOSFET switching device is connected to the first end of the fractional-order formed capacitor. The second end of the fractional-order formed capacitor is connected to the first end of the fractional-order formed inductor. The second end of the fractional-order formed inductor is connected to the S pole of the first MOSFET switching device.

5. A time-domain electromagnetic electrical source emission system according to claim 3 or 4, characterized in that The transmitting host further includes a logic control circuit, an isolation drive circuit, and a constant voltage clamping circuit. The logic control circuit generates a pulse-width modulation signal with a fixed frequency and duty cycle according to an instruction to the isolation drive circuit; The isolation drive circuit outputs the pulse-width modulation signal 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 clamping circuit is a multi-group of series-connected TVS diodes connected in parallel to one side of the H-bridge inverter circuit.

6. The time-domain electromagnetic electrical source emission system according to claim 5, wherein The logic control circuit is also used to generate a signal to the isolation drive circuit according to an instruction; 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 formed capacitor in the fractional-order ripple suppression circuit.

7. An electromagnetic electrical source emission system in the time domain according to claim 5, characterized in that, The logic control circuit is further configured to generate a signal to the isolation drive circuit according to an instruction; the isolation drive circuit outputs a pulse width modulation signal to the control end of the fractional-order impedance matching circuit to adjust 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 value, and the difference between the absolute value of the negative capacitance value and the parasitic capacitance of the equivalent load is minimized.

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