Transient electromagnetic emission system based on fractional order circuit

Abstract

The invention relates to a transient electromagnetic emission system for realizing high-quality emission waveform based on a fractional order control device. Comprising a transmitting host, the transmitting host comprises an H-bridge inverter circuit, a logic control circuit, an isolation driving circuit and a constant voltage clamping circuit, the H-bridge inverter circuit integrates four IGBT bridge arms and is alternately conducted under the control of a group of complementary pulse width modulation signals, and bipolar square waves are generated on a transmitting coil; the logic control circuit generates a pulse width modulation signal with a fixed frequency and a duty ratio to the isolation driving circuit according to the instruction; the isolation driving circuit outputs a pulse width modulation signal to four IGBT bridge arms of the H-bridge inverter circuit to complete driving control of the IGBT bridge arms; the constant-voltage clamping circuit comprises a plurality of groups of TVS diodes which are connected in parallel to one side of the H-bridge inverter circuit; the fractional-order oscillation absorption circuit comprises four groups of fractional-order capacitors which are respectively connected in parallel to each IGBT bridge arm, and the waveform quality of emission current is controlled fundamentally. According to the invention, the performance of the transient electromagnetic emission system can be improved.

Description

Technical Field

[0001] The present application relates to the field of electromagnetic detection for geophysical exploration, and in particular to a transient electromagnetic emission system based on a fractional-order circuit. Background Art

[0002] The transient electromagnetic method is a geophysical exploration method that uses the principle of electromagnetic induction to detect underground geological structures. It has the advantages of a wide detection range and high accuracy. Among them, a multi-turn small loop is usually used as the transmitting loop for the detection of shallow targets. The square wave pulse signal is its most important transmitting signal, and the shutdown characteristics of its transmitting current are one of the most important factors affecting the transient electromagnetic magnetic field response and data interpretation. However, due to the influence of the parasitic parameters of the transmitting system (parasitic parameters include the stray inductance and capacitance of the transmitting circuit, the equivalent inductance and distributed capacitance of the coil load, etc.), the transmitting current is not completely shut off, and there are serious early oscillations, which reduces the effective detection data or even completely distorts some data.

[0003] Currently, conventional transient electromagnetic transmission systems can address the turn-off oscillations of the transmission waveform by adding an absorption circuit to the transmitting H-bridge circuit, including a C-loop or RC-loop, combined with a topology such as multi-stage capacitors in parallel to absorb the oscillations. However, to achieve effective absorption, the components in the loop must meet specific parameters. However, this type of circuit cannot achieve accurate parameter control, has limited oscillation absorption effectiveness, and can lead to late tailing. It also does not fundamentally solve the problem of parasitic parameters. Summary of the Invention

[0004] The embodiment of the present application provides a transient electromagnetic emission system based on a fractional-order circuit, which solves the problem in the related art that it is impossible to effectively eliminate the early oscillation of the emission current shutdown.

[0005] The embodiments of the present application are implemented through the following technical solutions:

[0006] A transient electromagnetic emission system based on a fractional-order circuit includes: a transmitting host, the transmitting host including an H-bridge inverter circuit, a logic control circuit, an isolation drive circuit and a constant voltage clamping circuit, wherein:

[0007] The H-bridge inverter circuit integrates four IGBT bridge arms, which are used to alternately conduct under the control of a set of complementary pulse width modulation signals to generate a bipolar square wave on the transmitting coil;

[0008] A logic control circuit, used for generating a pulse width modulation signal with a fixed frequency and duty cycle to the isolation drive circuit according to instructions;

[0009] The isolated drive circuit is used to output 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;

[0010] The constant voltage clamp circuit is a set of TVS diodes connected in parallel on one side of the H-bridge inverter circuit;

[0011] The fractional-order oscillation absorption circuit includes four groups of fractional-order capacitors, which are respectively connected in parallel to each IGBT bridge arm.

[0012] Furthermore, a fractional-order load matching circuit is connected in parallel to the transmitting coil, and the fractional-order load matching circuit includes a group of fractional-order capacitors.

[0013] Furthermore, the fractional-order capacitor 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 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.

[0014] Furthermore, each of the four groups of fractional-order capacitors in the fractional-order oscillation absorption circuit is connected in series with a matching capacitor.

[0015] 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 modulated signal to the control end of the fractional-order capacitor in the fractional-order load matching circuit, adjusts the order α of the fractional-order capacitor in the fractional-order load matching circuit, so that the fractional-order capacitor has a negative capacitance, and minimizes the difference between the absolute value of the negative capacitance and the equivalent distributed capacitance of the transmitting coil.

[0016] 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 capacitor in the fractional-order oscillation absorption circuit, adjusts the order α of the fractional-order capacitor in the fractional-order oscillation absorption circuit, so that the fractional capacitor presents a negative capacitance, and minimizes the difference between the absolute value of the negative capacitance and the matching capacitance.

[0017] The embodiments of this application have at least the following beneficial effects: a fractional-order oscillation absorption circuit is used instead of a traditional RC absorption circuit, ensuring efficient absorption of early oscillations in the transmit current without compromising transmit performance. A fractional-order load matching device is used to reduce the overall parasitic inductance and distributed capacitance of the transmit coil, which, in conjunction with the fractional-order oscillation absorption circuit, fundamentally controls the waveform quality of the transmit current. This application is beneficial for improving the performance of transient electromagnetic transmission systems and further enhancing the accuracy and reliability of subsequent data interpretation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the overall structure of a transient electromagnetic emission system based on a fractional-order circuit provided in an embodiment of the present application;

[0019] Figure 2 A schematic diagram of the structure of an H-bridge inverter circuit provided in an embodiment of the present application;

[0020] Figure 3 A circuit diagram of a fractional-order capacitor provided in an embodiment of the present application;

[0021] Figure 4 Comparison diagram of the waveform quality of the emission current provided in the embodiments of the present application, including (a) the waveform of the emission current of a traditional transient electromagnetic emission system and (b) the waveform of the emission current of a transient electromagnetic emission system based on a fractional-order circuit. DETAILED DESCRIPTION

[0022] 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.

[0023] A transient electromagnetic transmission system uses a transmitter to generate a bipolar pulse current in a transmitting coil, thereby stimulating a primary pulse magnetic field underground. After the primary pulse magnetic field ceases, the induced electromagnetic field (secondary field) in the underground medium changes over time. During the pauses in the primary magnetic field, the receiving system measures the temporal changes in the secondary field. By studying this secondary field, information about the underground material can be obtained.

[0024] The transmitter unit is the core component of the transmitter system, responsible for generating the required current pulses. Its key parameters include maximum output voltage, maximum output current, transmission frequency, and waveform. For example, the IGGETEM-20 transmitter has a maximum output voltage of 120V, a maximum output current of 20A, a transmission frequency range of 0.1Hz to 250Hz, and a bipolar square wave waveform.

[0025] Transmitter coil: This coil converts the current pulses generated by the transmitter into a primary pulsed magnetic field. Its parameters, including coil shape, size, and number of turns, affect the intensity and distribution of the primary field. Common types of transmitter coils include center-loop and large fixed-source devices.

[0026] The embodiment of the present application adopts a fractional-order oscillation absorption circuit to replace the traditional RC absorption circuit in the transmitting host structure, thereby ensuring efficient absorption of the early oscillations of the transmitting current without affecting the transmitting performance; a fractional-order load matching device is used to reduce the overall parasitic inductance and distributed capacitance of the transmitting coil, and works together with the fractional-order oscillation absorption circuit to fundamentally control the waveform quality of the transmitting current.

[0027] See also Figure 1 A transient electromagnetic emission system based on fractional-order circuit is presented. The system includes a transmitter host, a transmitting coil, a fractional-order oscillation absorption circuit and a fractional-order load matching device.

[0028] The transmitter host comprises an H-bridge inverter circuit, a logic control circuit, an isolation drive circuit, and a constant voltage clamp circuit. The H-bridge inverter circuit, serving as the primary transmitter circuit, integrates four IGBT arms. These arms alternately conduct under the control of a set of complementary pulse-width modulation signals, generating a bipolar square wave at the transmitter coil, representing the transmit current. The H-bridge inverter circuit converts DC power into AC output. Its core concept is to utilize four IGBT arms in an "H"-shaped configuration. By controlling the combined states of these IGBT arms, a sine wave, square wave, or other desired AC waveform can be generated.

[0029] For example Figure 2 As shown, 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 the common end between IGBT tube Q1 and IGBT tube Q3 and the common end between IGBT tube Q2 and IGBT tube Q4 are connected to the transmitting coil.

[0030] Based on the instructions, the logic control circuit generates a pulse-width modulated signal with a fixed frequency and duty cycle to the isolated drive circuit. The isolated drive circuit then outputs the pulse-width modulated signal to the four IGBT bridge arms, completing the drive control of the four IGBT bridge arms. The constant-voltage clamp circuit consists of multiple sets of TVS diodes connected in parallel on one side of the H-bridge inverter circuit to reduce the turn-off time.

[0031] See also Figure 2 Combine Figure 1As shown, in an embodiment of the present application, a fractional-order oscillation absorption circuit is provided on the transmitter host. The fractional-order oscillation absorption circuit includes four groups of fractional-order capacitors, one of which is connected in parallel to each IGBT bridge arm. Each group of fractional-order capacitors can also be connected in series with a matching capacitor, thereby replacing the traditional C-loop or RC-loop circuit by connecting the fractional-order capacitors and the matching capacitors in series. Using the fractional-order oscillation absorption circuit instead of the traditional RC absorption circuit ensures efficient absorption of early oscillations of the transmit current without affecting transmit performance.

[0032] See also Figure 3 The circuit principle diagram of the fractional capacitor is shown in FIG. Each fractional capacitor includes a power supply, a first MOSFET switch device S1, a second MOSFET switch device S2, a fractional inductor L, a voltage divider protection resistor R, and a fractional capacitor C. α , wherein the S-pole (source) of the first MOSFET switch device S1 and the D-pole (drain) of the second MOSFET switch device S2 are connected to form a MOSFET switch device group, the power supply is connected to both ends of the MOSFET switch device group through a voltage divider protection resistor, and the S-pole of the second MOSFET switch device S2 is connected to the fractional-order capacitor C α The first end of the fractional order capacitor C α The second end of the fractional-order inductor L is connected to the first end of the fractional-order inductor L, and the second end of the fractional-order inductor L is connected to the S-pole of the first MOSFET switch device S1. The G-pole (gate) of the two MOSFET switch devices is a control terminal for controlling the conduction state between the D-pole and the S-pole.

[0033] The port characteristics of the fractional-order capacitor, that is, the phase difference between the port voltage and the current flowing through it, are related to the order α of the fractional-order capacitor. The circuit properties can be changed by adjusting the order.

[0034] The relationship between the voltage and current of the fractional-order capacitor is as follows:

[0035]

[0036] Where α is the order of the fractional capacitor. FOC is the current passing through the fractional capacitor, U FOC is the voltage across the capacitor, C α is the capacitance of the fractional order capacitor.

[0037] For example, when -1 < α < 0, the fractional-order capacitor exhibits positive resistance and inductance, while when 0 < α < 1, the fractional-order capacitor exhibits positive resistance and capacitance, and so on. Based on this characteristic, each link in the fractional-order circuit can be accurately constructed and finely adjusted according to the actual detection needs of the transmission system operation process.

[0038] The fractional-order negative capacitor used in the fractional-order oscillation absorption circuit is called the fractional-order negative capacitor. When α = -1, the fractional-order capacitor is called the negative capacitor, abbreviated as NOC, C noc is the equivalent capacitance of negative capacitance. Since negative capacitance exhibits characteristics similar to inductance in AC, its equivalent capacitance C noc The value is opposite to that of traditional capacitors. According to the equivalent formula of capacitor series connection, NOC is connected in series with a matching capacitor with a capacitance of C1. The equivalent capacitance of the two in series is C eq-w for:

[0039]

[0040] When the negative capacitance equivalent capacitance C noc When the sum of the capacitances of the series capacitor C1 is close in value, the equivalent capacitance C eq-w will tend to infinity. Traditional transmitter systems connect an R-circuit or RC-circuit in parallel across each IGBT in the H-bridge transmitter circuit to absorb oscillations, but this often fails to absorb them thoroughly or causes distortion in the transmitted waveform. Oscillation absorption devices constructed with fractional-order capacitors not only enable the construction of larger capacitors but also offer the advantage of controllable properties. The order can be adjusted to meet specific circuit requirements for optimal absorption.

[0041] In one embodiment, 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 capacitor in the fractional-order oscillation absorption circuit, adjusts the order α of the fractional-order capacitor in the fractional-order oscillation absorption circuit, so that the fractional capacitor presents a negative capacitance, and minimizes the difference between the absolute value of the negative capacitance and the matching capacitance.

[0042] In one embodiment, a fractional-order load matching circuit is connected in parallel to the transmitting coil. This fractional-order load matching circuit includes a set of fractional-order capacitors. The fractional-order load matching device is also implemented using fractional-order capacitors. Because the transmitting coil, acting as a load, is not an ideal resistive load, it can be considered a second-order RLC equivalent circuit consisting of the coil's DC internal resistance Rs, equivalent parasitic inductance Ls, and equivalent distributed capacitance Cs. Therefore, the characteristics of fractional-order capacitors can be exploited to connect the fractional-order capacitors in parallel with the transmitting coil, acting as a load. By controlling the order α, parallel resonance is achieved with the load. Matching reduces the overall inductance and capacitance of the load, thereby further controlling the quality of the transmitted waveform.

[0043] The fractional-order load matching device also uses the fractional-order negative capacitance characteristics to connect fractional-order capacitors in parallel at both ends of the transmitting coil. According to the capacitor parallel formula:

[0044] C eq-w =Cs+Cnoc

[0045] When the negative capacitance C noc When it is close to the equivalent distributed capacitance Cs, the equivalent distributed capacitance of the coil load can be eliminated, thereby achieving the purpose of suppressing early oscillation and optimizing the quality of the transmitted waveform.

[0046] 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 capacitor in the fractional-order load matching circuit, and adjusts the order α of the fractional-order capacitor in the fractional-order load matching circuit so that the fractional-order capacitor presents a negative capacitance value, and minimizes the difference between the absolute value of the negative capacitance value and the equivalent distributed capacitance of the transmitting coil, that is, achieving a negative capacitance value C noc It is close to the equivalent distributed capacitance Cs, with one positive and one negative, which can eliminate the equivalent distributed capacitance of the coil load.

[0047] The transmitting system of the embodiment of the present application is used to transmit current. The current waveform measured by the test is compared with the waveform of the traditional transmitting system. Figure 4 As can be seen, the emission current is set to 9A. Figure 4 (b) shows the turn-off oscillation ratio in the waveform of the transient electromagnetic emission system based on the fractional order circuit. Figure 4 The turn-off oscillation in the waveform of the emission current of the conventional transient electromagnetic emission system shown in (a) is reduced by 109.6%, thereby achieving a high-quality emission waveform.

Claims

1. A transient electromagnetic emission system based on fractional-order circuit, characterized in that: include: The transmitting host includes an H-bridge inverter circuit, a logic control circuit, an isolation drive circuit, and a constant voltage clamp circuit, wherein: The H-bridge inverter circuit integrates four IGBT bridge arms, which are used to alternately conduct under the control of a set of complementary pulse width modulation signals to generate a bipolar square wave on the transmitting coil; A logic control circuit, used for generating a pulse width modulation signal with a fixed frequency and duty cycle to the isolation drive circuit according to instructions; The isolated drive circuit is used to output 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 set of TVS diodes connected in parallel on one side of the H-bridge inverter circuit; The fractional-order oscillation absorption circuit includes four groups of fractional-order capacitors, which are respectively connected in parallel to each IGBT bridge arm.

2. The transient electromagnetic emission system based on fractional order circuit according to claim 1, characterized in that: A fractional-order load matching circuit is connected in parallel to the transmitting coil, and the fractional-order load matching circuit includes a group of fractional-order capacitors.

3. The transient electromagnetic emission system based on fractional order circuit according to claim 1 or 2, characterized in that: The fractional-order capacitor includes a power supply, a first MOSFET switch device, a second MOSFET switch device, a fractional-order inductor, a voltage divider protection resistor and a fractional-order capacitor, wherein the S pole of the first MOSFET switch device and the D pole of the second MOSFET switch device are connected to form a MOSFET switch device group, the power supply is connected to both ends of the MOSFET switch device group through the voltage divider protection resistor, the S pole of the second MOSFET switch 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 switch device.

4. The transient electromagnetic emission system based on fractional order circuit according to claim 1, characterized in that: Each of the four groups of fractional-order capacitors in the fractional-order oscillation absorption circuit is connected in series with a matching capacitor.

5. The transient electromagnetic emission system based on fractional order circuit according to claim 3, 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 modulated signal to the control end of the fractional-order capacitor in the fractional-order load matching circuit, adjusts the order α of the fractional-order capacitor in the fractional-order load matching circuit, so that the fractional-order capacitor exhibits a negative capacitance, and minimizes the difference between the absolute value of the negative capacitance and the equivalent distributed capacitance of the transmitting coil.

6. The transient electromagnetic emission system based on fractional order circuit according to claim 4, characterized in that: 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 capacitor in the fractional-order oscillation absorption circuit, adjusts the order α of the fractional-order capacitor in the fractional-order oscillation absorption circuit, so that the fractional capacitor presents a negative capacitance value, and minimizes the difference between the absolute value of the negative capacitance value and the matching capacitance.

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