Controllable source electromagnetic exploration system composite impedance matching network and design method

Abstract

The present application belongs to the technical field of electromagnetic detection, and relates to a composite impedance matching network of a controllable source electromagnetic exploration system and a design method. The composite impedance matching network comprises a topology structure of a CIMN composed of a fixed capacitor CF and an ICLC part in series, and is integrated in a transmitting system of the controllable source electromagnetic exploration system. The CIMN adopts a new combined matching method and related optimization design, improves the wideband current transmission performance in terms of compensation range and power loss, proposes a new combined matching topology structure, and illustrates the corresponding wideband matching function through mathematical derivation and analysis. In combination with the wideband transmission requirement of the controllable source electromagnetic method and the limited power supply condition, a parameter optimization scheme and a control strategy of the composite impedance matching network are designed. The CIMN can better adapt to the wide working frequency range of the CSEM transmitter, improve the matching bandwidth, and reduce the power loss.

Description

A composite impedance matching network and design method for a controllable source electromagnetic exploration system Technical Field

[0001] This invention belongs to the field of electromagnetic detection technology, specifically relating to a composite impedance matching network and design method for a controllable source electromagnetic exploration system. Background Technology

[0002] Controlled source electromagnetic method ( Geophysical exploration is an important method that is now widely used in mineral mining, hydrological surveys, and urban underground space exploration. The method utilizes a high-power transmission system integrated with an electromagnetic transducer as an artificial field source, while simultaneously incorporating signal processing techniques based on the Earth's electromagnetic response to reflect geological structural information. The transmission system serves as... The core of the technology consists of a power supply, a power inverter, a matching device, and an electromagnetic transducer. The transmitting system injects bipolar current into a long grounded wire to form an electromagnetic transducer and radiates a frequency-controllable alternating electromagnetic field into space. Since the skin depth is closely related to the frequency of electromagnetic waves, it is usually necessary to transmit current signals over a wide frequency range to achieve effective coverage of the target detection area.

[0003] Transmission performance is a crucial factor for the success of the experiment, because the strength of the transmitted signal directly affects the signal-to-noise ratio (SNR). The measurement accuracy is crucial, determining the confidence level of the experimental results. In field environments, due to limitations in transmitter power capacity and power supply conditions, efficient transfer of active power from the power source to the transducer load is essential. However, The exploration characteristics also cause the following two problems: 1. Low power capacity utilization. As a typical inductive load, the electromagnetic transducer will cause serious reactive power occupation, resulting in the power capacity of the power supply not being fully and effectively used for current transmission; 2. Weak transmitted signal energy. The intensity of the transmitted current is severely suppressed by the load reactance, especially for high frequency components.

[0004] To address these issues, researchers employed various techniques to enhance the excitation signal strength through three aspects: source voltage boosting, multi-source configuration, and auxiliary clamping circuit design. In comparison, impedance matching methods exhibit lower system complexity and cost, and can improve transmitter power utilization without increasing the supply voltage. Currently, this type of method has gradually attracted widespread attention from researchers and has been incorporated into various transducer applications, especially in broadband transmission scenarios.

[0005] Existing impedance matching methods can be divided into two types: uncontrollable and controllable. In uncontrollable matching, the energy storage characteristics of capacitors and inductors make them suitable for reactive power compensation. These components are typically designed with a natural frequency to handle matching applications with specific operating frequency standards, such as power distribution networks and wireless power transfer. At power system frequencies, fixed capacitor banks can be used to match the inductive reactive power of transmission cables. In wireless power transfer (… ) and underwater acoustic detection ( In this application, an additional layer is added between the transmitter and the inductive load. A multi-frequency resonant circuit is used to ensure high gain at multiple discrete frequencies. However, This type of circuit has strong frequency sensitivity, meaning that efficient power transmission can only be achieved when the inherent resonant frequency is strictly consistent with the power supply frequency; and this characteristic becomes more and more significant as the matching level increases, thus limiting its frequency expansion capability.

[0006] As a controllable impedance matching scheme, switched-control capacitors have been directly used to increase the number of matching frequencies, but their matching accuracy and transient performance are poor. To broaden the gain bandwidth, researchers have designed radio frequency (RF)... Parametric design and calibration methods for power amplifiers. With the development of power electronics technology, existing technologies have also introduced thyristors or insulated-gate bipolar transistors (IGBTs). This improves matching speed and accuracy, and demonstrates the advantage of continuous controllability over a wide frequency band. Existing technology proposes a thyristor-based control method... A broadband impedance matching method for circuits from 400Hz to 700Hz is used to improve underwater acoustic detection. The power capacity utilization rate of the power amplifier in this application. The impedance function of this technique is derived from the fundamental period, and the matching accuracy is relatively limited. Subsequently, existing technologies have also proposed a method using... of While the active impedance matching method for bridge converters improves matching accuracy by approximately 0.5%, it also introduces an additional 800V DC power supply and increases power loss by 4%. Existing technologies also propose using... Passive matching methods using control capacitors eliminate the need for an additional DC power supply, but their compensation frequency range is still limited to within 1kHz. In contrast, shallow-sea electromagnetic detection (… This requires power inverters to operate over a wider frequency range to achieve effective coverage of shallow sea exploration areas, which poses a greater challenge to impedance matching technology. However, existing... The applicable bandwidth of controllable impedance matching is still limited, and the power loss optimization problem is not considered. Summary of the Invention

[0007] The purpose of this invention is to provide a composite impedance matching network and design method for a controllable source electromagnetic exploration system, so as to solve the problem of inductive reactive power occupation and its adverse effect on the transmission current intensity.

[0008] This invention is achieved through the following technical solution:

[0009] A composite impedance matching network for a controlled-source electromagnetic exploration system, wherein the transmitting system of the controlled-source electromagnetic exploration system integrates the composite impedance matching network. ;

[0010] The launching system is powered by a generator and equipped with a rectifier bridge diode. , , , , The power inverter of the transmitting system is connected in series between the power inverter and the load. Bridge structure, made of Switching transistor , Switching transistor , Switching transistor , Switching transistor and parallel DC capacitor composition;

[0011] The topology consists of fixed capacitors and series Partial composition, among which, Partially controlled by insulated-gate bipolar transistors Includes matching capacitors ,inductance and two connected in reverse series Composed of switches and switch ; The equivalent impedance is determined by the fixed capacitance. The impedance and controllability Impedance composition.

[0012] A design method for a composite impedance matching network in a controllable source electromagnetic exploration system includes the following steps:

[0013] A. Constructing a system that combines a fixed capacitor and an insulated-gate bipolar transistor for control. of Topological structure, and integrated into the launch system of a controlled-source electromagnetic exploration system;

[0014] B. Proceed Equivalent impedance analysis, The equivalent impedance is determined by the fixed capacitance. The impedance and controllability Impedance composition, including fixed capacitance With a fixed impedance in part, it can provide constant impedance and reactive power compensation to achieve fundamental frequency matching; Some parts provide controllable impedance and reactive power compensation, which are controllable. Impedance can be adjusted by configuring the duty cycle control law, thereby achieving full impedance matching over a wide bandwidth;

[0015] C. Parameter optimization of controlled-source electromagnetic exploration system: Analyze load impedance and determine the maximum matching impedance and minimum matching capacitance. and minimum matching impedance and maximum matching inductance The optimal parameter combination is obtained by minimizing power loss as the optimization objective.

[0016] D、 The overall matching control optimization is designed, in which... The overall matching control includes power frequency identification, instantaneous power calculation, impedance determination, duty cycle control reference calculation, and matching function execution; by comparing and determining the identified frequency... The error between the impedance and the load impedance is calculated and corrected. The synthesized control quantity serves as the modulation reference, and is transmitted through a unipolar circuit. The method is Generate the final control signal.

[0017] Further, in step A, the transmitting system is powered by a generator and equipped with a rectifier bridge diode. , , , , Connected in series between the power inverter and the load, the power inverter of the transmitting system adopts a traditional H-bridge structure, consisting of... Switching transistor , Switching transistor , Switching transistor IGBT switching transistor and parallel DC capacitor composition.

[0018] Further, step A, The topology consists of fixed capacitors and series Partial composition, among which, Partially controlled by insulated-gate bipolar transistors Includes matching capacitors ,inductance and two connected in reverse series Composed of switches and switch ; The equivalent impedance is determined by the fixed capacitance. The impedance and controllability Impedance composition.

[0019] Furthermore, step B, controllable Impedance analysis specifically includes the following steps:

[0020] B1. Through control Operating in four modes, the equivalent impedance of the matching network is adjusted:

[0021] B2. Through coordinated control switch and switch The duty cycle of the pulse width modulation control signal controls each During the cycle, inductor L flows M The current ratio is used to indirectly control the parallel inductor branch and the entire circuit. Partial equivalent impedance value;

[0022] B3. Regulation by configuring duty cycle control law The equivalent impedance is thus achieved, thereby realizing full impedance matching over a wide frequency band.

[0023] Furthermore, in step B1, in Part, switch and switch The controllable state determines different impedance functions, and one operating cycle The internal working mode is as follows:

[0024] Mode 1: Switch and switch All are turned off in this mode. Some only match capacitors It works, and its impedance function is:

[0025] (7)

[0026] In the formula, The imaginary unit, Angular frequency;

[0027] Mode 2: Switch S1 is on, switch S2 is off. At this time, the inductor... With capacitor in parallel, The impedance function of part of the impedance can be expressed as:

[0028] (8)

[0029] Mode 3: Switch Off, switch During conduction, the inductor is excluded from matching, and its current is supplied by... The current continues and is approximately constant. The external impedance function is the same as formula (7) in mode 1;

[0030] Mode 4: Switch and switch All are conducting; at this time, The available impedance remains the same as in formula (7).

[0031] Furthermore, in step B2, it is assumed that the inductor The investment phase and the follow-up phase are respectively and Duty cycle is defined as Then, the total current increment of the equivalent inductance branch during the nth switching cycle is... This can be deduced as:

[0032] (9)

[0033] In the formula, For capacitor The voltage across the two ends;

[0034] The cumulative current flowing through the equivalent inductance can be expressed as:

[0035] (10)

[0036] Furthermore, when switches S1 and S2 operate at high frequencies, the equivalent impedance of the inductor branch... for:

[0037] (11)

[0038] therefore, equivalent impedance Represented as:

[0039] (12).

[0040] Furthermore, in step B3, impedance The function expression is further derived as follows:

[0041] (13)

[0042] In the formula, For fixed capacitor impedance, for The equivalent impedance, To match the capacitor, It is an inductor;

[0043] The introduction of switches makes It possesses a variable impedance function, thereby transforming the traditional natural frequency into a continuously adjustable resonant frequency;

[0044] According to the impedance function in formula (13), It can be characterized as a controllable reactor, integrated Total impedance of the transmitting system The function is shown in formula (14):

[0045] (14)

[0046] In the formula, For equivalent inductance, The impedance of the load;

[0047] thus, It can provide a controllable negative imaginary part of impedance to cancel the positive imaginary part of the load impedance; when the transmitting system circuit is in a resonant state with zero imaginary part impedance, impedance matching is achieved, and the inherent matching frequency of the fixed capacitor section is a fixed value. ; The addition of parts The overall resonant frequency can be controlled by the duty cycle, as shown in the following formula:

[0048] (15)

[0049] In the middle, the fixed capacitor part and The components can provide fixed reactive power compensation and controllable reactive power compensation respectively, and the two components together constitute... The total reactive power compensation is used to offset the reactive power introduced by the imaginary part of the impedance expression of formula (16) under wideband operation;

[0050] (16)

[0051] In the formula, for reactive power, For fixed capacitor reactive power, for The reactive power.

[0052] Furthermore, in step C, in conjunction with formula (12) The impedance function can be used to determine the maximum matching impedance and the minimum matching capacitance. As shown in the following formula:

[0053] (17)

[0054] Minimum matching impedance and maximum matching inductance L M As shown in the following formula:

[0055] (18)

[0056] definition and The impedance matching is shown in Equation (19), used to evaluate the fixed capacitor. Partial and Controllable Matching weights between parts ;

[0057] (19)

[0058] In the formula, To match capacitors The impedance.

[0059] Furthermore, step D specifically includes the following steps:

[0060] D1, Integration The controllable source electromagnetic exploration system performs frequency calculations on the power signal and measures the output voltage of the power inverter. Sample and transmit to Controller;

[0061] D2. The delay module, combined with the set threshold, completes... During the zero-crossing identification process, the controller's built-in timer continuously counts, and the durations of the on and off states within the m-th working cycle are recorded as follows: and The power supply frequency can be identified using the following expression:

[0062] (20)

[0063] D3, Based on the sampled load voltage With load current The active power of the load is calculated using instantaneous power theory. L and reactive power :

[0064] (twenty one)

[0065] In the formula, , The sampled load voltages are respectively With load current Delay The signal obtained later To calculate the active power of the load L and reactive power intermediate variables;

[0066] The delay expression is as follows:

[0067] (twenty two)

[0068] Load active power L and reactive power The calculation is as follows:

[0069] (twenty three)

[0070] (twenty four)

[0071] In the formula, for The average value, for The average value;

[0072] D4. Based on the matching principle analysis and the relationship between power and impedance in formula (3), the desired impedance is identified. The impedance is as follows:

[0073] (3)

[0074] (25)

[0075] Combining the load impedance expression identified in formula (25) with that in formula (12) The impedance function, the fixed impedance in formula (26) is used for fundamental matching, while the impedance in formula (12) is used for fundamental matching. The impedance is used for impedance matching of the remaining portion; therefore, the duty cycle reference can be determined as follows:

[0076] (26)

[0077] D5. Determine the identified [items] through comparison. The error between the impedance and the load impedance, and the calibration value Theoretical calculation results added to formula (26) superior;

[0078] D6. The synthesized control quantity is used as the modulation reference, through unipolar... The method is as proposed Generate the final control signal.

[0079] Compared with the prior art, the beneficial effects of the present invention are:

[0080] 1. The invention proposed A novel combined matching method and related optimization design were adopted to improve the broadband current transmission performance in terms of both compensation range and power loss.

[0081] 2. This invention proposes a novel combined matching topology and clarifies its corresponding broadband matching function through mathematical derivation and analysis;

[0082] 3. Combining controlled-source electromagnetic method ( To meet the requirements of broadband transmission and limited power supply conditions, a composite impedance matching network was designed. Parameter optimization schemes and control strategies;

[0083] 4. Compared with existing methods, the present invention provides... Better fit The transmitter's wide operating frequency band increases the matching bandwidth and reduces power loss. Attached Figure Description

[0084] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0085] Figure 1 shows the integration proposed. The circuit structure of the transmission system;

[0086] Figure 2 shows the actual measured equivalent load parameters of the electromagnetic transducer;

[0087] Figure 3 shows the calculated transmission current under different frequencies and DC supply voltages. ;

[0088] Figure 4 shows the switch. and switch All are in the off state Work mode;

[0089] Figure 5 shows the switch. It is in the on state and the switch is on. Closed Work mode;

[0090] Figure 6 shows the switch. The switch is in the off state. It is in the on state Work mode;

[0091] Figure 7 shows the switch. and switch All are in the on state Work mode;

[0092] Figure 8 shows the impedance. Matching performance;

[0093] Figure 9 shows reactive power. Matching performance;

[0094] Figure 10 is a schematic diagram of the proposed combined reactive power compensation.

[0095] Figure 11 shows the power loss of the matching system under different matching ratios;

[0096] Figure 12 shows the comparative simulation results of the transmission current intensity;

[0097] Figure 13 is The overall control block diagram. Detailed Implementation

[0098] The present invention will be further described below with reference to embodiments:

[0099] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention and not the entire structure.

[0100] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0101] This invention proposes a novel composite impedance matching network ( ), to provide greater The reactive power compensation range for transmitted current signals. First, a method combining fixed capacitors and insulated-gate bipolar transistor control is proposed. ( A novel matching topology is proposed, and a collaborative optimization design is put forward based on it, including parameter optimization methods and compensation control strategies, to adaptively track dynamic impedance and reduce power loss in the required frequency range.

[0102] Specifically, the proposed combined impedance matching network ( The topology and matching performance of the ) were analyzed.

[0103] Shallow sea electromagnetic detection ( The electromagnetic transducer of the transmitting system consists of a transmitting antenna and ground, as shown in Figure 1. The transmitting antenna includes a long conductor and a grounding electrode, which, together with the ground, form a closed loop. To approximate a uniform line source, the length of the grounding cable is typically in the hundreds or even thousands of meters, exhibiting external characteristics of an inductive-resistive load. Considering the distributed parameters of the grounding electrode and the inherent electrical and polarization characteristics of the ground, the ground can be modeled as an inductive-resistive load. Within the experimental frequency band, the equivalent capacitance is extremely small and can usually be ignored. Overall, the transducer's equivalent impedance... It can be modeled as a resistor With inductance The series configuration is shown in Figure 1 and formula (1):

[0104] (1)

[0105] In the formula, and These are the equivalent resistance and equivalent inductance of the load, R. W and L W These are the equivalent resistance and equivalent inductance of the transmitting antenna, respectively. , and These are the grounding resistance, the equivalent resistance of the earth, and the equivalent capacitance, respectively. The imaginary unit, ω is the angular frequency.

[0106] Figure 2 shows the actual impedance measurement results of the electromagnetic transducer. The results show that the transmitting transducer is a typical inductive load: its resistance remains basically constant, while its inductive reactance increases significantly with the increase of the transmission frequency. This characteristic is basically consistent with the equivalent model defined in formula (1).

[0107] Combining formula (1), when the DC power supply voltage is Under these circumstances, the intensity of the emitted current It can be calculated by formula (2). The presence of the imaginary part of the impedance will significantly suppress the intensity of the emission current, and this characteristic is particularly obvious under high-frequency operating conditions.

[0108] (2)

[0109] Without an impedance matching device, the power inverter’s transmit voltage is directly applied to the load terminals. The active power of the transducer used for energy conversion, as shown in formula (3), and the reactive power, as shown in formula (4), are both provided by the power inverter, which will occupy the total power capacity of the transmitter system.

[0110] (3)

[0111] (4)

[0112] In the formula, This refers to the active power of the electromagnetic transducer. This refers to the reactive power of the electromagnetic transducer.

[0113] To quantitatively assess reactive power occupancy, power utilization rate ( The definition is as follows:

[0114] (5)

[0115] Figure 3 shows the different frequencies and power supply voltages. Under the given conditions, the calculated transmit current and power utilization rate ( The results show that the transmit current intensity and power utilization rate ( The emission performance indicators, such as [specific parameters], continue to deteriorate with increasing frequency. Improving [the system / mechanism] is crucial. While it can increase active power, it also increases reactive power accordingly, and cannot fundamentally solve the problem of transmitter power capacity occupancy.

[0116] Integrated The circuit structure of the transmitting system is shown in Figure 1. The power inverter adopts a traditional... Bridge structure, made of Switching transistor , Switching transistor , Switching transistor , Switching transistor and parallel DC capacitor Composition. The transmitter system is powered by a generator and equipped with a rectifier bridge diode. , , , The mentioned It is connected in series between the power inverter and the load. The topology consists of fixed capacitors and series Partial composition. Among them, Some include matching capacitors ,inductance and two connected in reverse series Composed of switches and switch In this embodiment, using , , , and These represent DC capacitors. Power inverter, fixed capacitor ,capacitance And the voltage across the load. , , and These represent the current flowing through the power inverter section and the capacitor, respectively. ,inductance and the current of the load.

[0117] As shown in Figure 1, The equivalent impedance is determined by the fixed capacitance. impedance and controllable Impedance composition. For a fixed capacitor. Part of it has a fixed impedance and provides fundamental reactive power compensation.

[0118] (6)

[0119] In the formula, The imaginary unit, ω is the angular frequency.

[0120] exist Part, switch and switch The controllable state determines the different impedance functions. The operating modes within one operating cycle Ts are shown in Figures 4-7, and are explained in detail below:

[0121] As shown in Figure 4, Mode 1: Switch and switch All are turned off. In this mode... Some only match capacitors It works, and its impedance function is:

[0122] (7)

[0123] As shown in Figure 5, Mode 2: Switch On, switch When switched off, the inductor... With capacitor In parallel connection, the impedance function of the ICLC section can be expressed as:

[0124] (8)

[0125] As shown in Figure 6, Mode 3: Switch Off, switch During the conduction phase, the inductor is excluded from the matching process, and its current is supplied by the switch. The freewheeling current is approximately constant. The external impedance function of the ICLC is the same as that in formula (7) in mode 1.

[0126] As shown in Figure 7, Mode 4: Switch and switch All are conducting; at this time, The available impedance remains the same as in formula (7).

[0127] Therefore, by controlling When operating in the above mode, the equivalent impedance of the matching network can be adjusted.

[0128] Assuming the inductor The investment phase and the follow-up phase are respectively and Duty cycle is defined as Then, the total current increment of the equivalent inductance branch during the nth switching cycle is... This can be deduced as:

[0129] (9)

[0130] In the formula, For capacitor The voltage across the two ends;

[0131] The cumulative current flowing through the equivalent inductance can be expressed as:

[0132] (10)

[0133] In addition, when the switch and switch When operating at high frequencies, the equivalent impedance of the inductor branch for:

[0134] (11)

[0135] therefore, equivalent impedance It can be represented as:

[0136] (12)

[0137] Therefore, by coordinating the control of the switching on / off switch and freewheeling switch Pulse width modulation (PWM) The duty cycle of the control signal can control each During the cycle, inductor L flows M The current ratio is used to indirectly control the parallel inductor branch and the entire circuit. The equivalent impedance value of part.

[0138] The proposed impedance The function expression can be further derived as follows:

[0139] (13)

[0140] In the formula, For fixed capacitor impedance, for The equivalent impedance, To match the capacitor, It is an inductor.

[0141] Therefore, the introduction of the switch makes It possesses a variable impedance function, thereby transforming the traditional natural frequency into a continuously adjustable resonant frequency.

[0142] According to the impedance function in formula (13), the proposed This can be characterized as a controllable reactor. At this point, the integrated... Total impedance of the transmitting system The function is shown in formula (14).

[0143] (14)

[0144] In the formula, For equivalent inductance, The impedance is the load impedance.

[0145] As can be seen from formula (14), the proposed It can provide a controllable negative imaginary part of impedance to cancel out the positive imaginary part of the load impedance. Impedance matching is achieved when the transmitting system loop is in a resonant state with zero imaginary part impedance. Under this condition, the total impedance is minimized. The inherent matching frequency of the fixed capacitor section is a fixed value. . The addition of parts The overall resonant frequency can be controlled by the duty cycle, as shown in the following formula:

[0146] (15)

[0147] Figures 8 and 9 illustrate the variation of the matching frequency with the duty cycle, further demonstrating that it can be adjusted by configuring the duty cycle control law. The equivalent impedance is thus achieved, thereby realizing full impedance matching over a wide frequency band.

[0148] In the mentioned In the middle, the fixed capacitor part and Some components can provide fixed reactive power compensation and controllable reactive power compensation, respectively. These two components together constitute... The total reactive power compensation is used to offset the reactive power introduced by the imaginary part of the impedance expression of formula (16) under wideband operation.

[0149] (16)

[0150] In the formula, for reactive power, For fixed capacitor C F reactive power, for The reactive power.

[0151] Figure 10 presents... Fixed capacitor section and controllable The impedance and reactive power compensation characteristics of the section are shown. It can be seen that the fixed capacitor section provides constant impedance and reactive power compensation to achieve fundamental frequency matching; while... Partially, it provides controllable impedance and reactive power compensation to complete the matching of the remaining parts.

[0152] Next, the system parameters were optimized in this invention.

[0153] According to the suggestion The topology and matching principle are explained, and the required frequency range and power loss reduction must be considered when designing and optimizing system parameters. The overall parameter design is summarized in the algorithm. Then, the proposed impedance matching method is compared with existing methods to demonstrate its performance advantages.

[0154] The load impedance is shown by the red dashed line and shaded area in Figure 12. Within the desired frequency range [ , Within this range, the inductive impedance of the load increases with increasing frequency. The proposed... Combining fixed capacitive impedance and controllable Impedance constitutes a wideband impedance matching function suitable for electromagnetic transducer loads.

[0155] Fixed capacitor The provided fixed capacitive impedance, shown by the green dashed line and shaded area in the figure, is used to achieve fundamental frequency matching. The characteristic of this capacitive impedance is that it continuously decreases as the frequency increases.

[0156] Subsequently, the impedance matching of the remaining portion of the load is controlled by Partial responsibility. To ensure full matching within the desired frequency band, It needs to have both capacitive and inductive reactive power compensation capabilities, as shown by the blue dashed line and shaded area in the figure.

[0157] The highest frequency in the desired frequency band At this point, to compensate for the maximum inductive impedance The maximum capacitive impedance must be provided. This is in conjunction with formula (12). The impedance function can be used to determine the maximum matching impedance and the minimum matching capacitance. As shown in the following formula:

[0158] (17)

[0159] Subsequently, It is also necessary to be at the lowest frequency of the desired frequency band. Sufficient capacitive impedance is provided to offset the entire inductive impedance of the load. Therefore, the minimum matching impedance and the maximum matching inductance can be derived. As shown in the following formula:

[0160] (18)

[0161] Based on the above parameterization process, in determining After the design scheme is completed, the corresponding [design] can be determined. and Parameter design should aim to minimize power loss to obtain the optimal parameter combination. For ease of analysis, define... and The impedance matching is shown in Equation (19), used to evaluate the fixed capacitor. Partial and Controllable Matching weights between parts .

[0162] (19)

[0163] In the formula, To match capacitors The impedance.

[0164] Figure 11 shows the calculated power loss of the matching system under different impedance ratios; the specific calculation method for power loss is given in the appendix. The power loss varies with the matching ratio, reaching a minimum around η=28%, indicating that this optimized design can guide the reduction of overall loss. Furthermore, Figure 11 also presents the calculated power loss results of existing broadband matching methods. In contrast, existing methods do not involve fixed impedance matching and related parameter design; therefore, traditional methods can be considered as broadband matching after removing the fixed impedance portion. As shown in Figure 11, under different matching ratios, the power loss of existing methods is higher than that of the proposed method. The method, which indicates the proposed It has inherent advantages over traditional broadband matching in terms of power loss.

[0165] Based on the above The proposed method differs significantly from existing matching methods in the following ways:

[0166] Compared to traditional fixed impedance matching, the proposed... By adding This part can provide a controllable matching impedance, thereby adaptively matching the changing load impedance within the desired frequency range.

[0167] Compared to existing broadband impedance matching methods, the proposed method introduces fixed impedance matching to provide a controllable matching section, thereby reducing bandwidth usage. Part of the impedance matching range that needs to be covered.

[0168] To provide a more intuitive comparison of performance, Figure 12 shows the proposed... Simulation results comparing the proposed method with existing broadband matching methods are shown in Figure 12. As can be seen, the fixed capacitor can only achieve impedance matching at a single frequency point of 512Hz; the matching bandwidth of existing broadband matching methods is 512Hz~1024Hz; in contrast, the proposed method… It can achieve a wider matching frequency range of 512Hz to 2048Hz. Compared with existing wideband matching methods, the proposed method... Lower power loss can be guaranteed at different frequencies. In summary, based on the proposed combined matching topology and corresponding parameter optimization design, the present invention... The method has the advantages of wider matching frequency range and lower power loss in transmission performance.

[0169] Subsequently, the present invention provides for the proposed Design an overall matching control strategy. The proposed... The overall matching control strategy is summarized in Figure 13 and the algorithm, including power frequency identification, instantaneous power calculation, impedance determination, duty cycle control reference calculation, and matching function execution. The specific process is described below:

[0170] first, The system calculates the frequency of the power signal to provide a basis for subsequent actions. This includes the output voltage of the power inverter. Sample and transmit to Controller. Subsequently, the delay module, combined with the set threshold, completes... The zero-crossing identification process is performed. Simultaneously, the controller's built-in timer continuously counts. The durations of the "on" and "off" states within the m-th working cycle are recorded as follows: and Therefore, the power supply frequency can be identified using the following expression:

[0171] (20)

[0172] Subsequently, based on the sampled load voltage With load current The active power of the load can be calculated using instantaneous power theory. L and reactive power :

[0173] (twenty one)

[0174] In the formula, , The sampled load voltages are respectively With load current Delay The signal obtained later To calculate the active power of the load L and reactive power Intermediate variables.

[0175] The delay expression is as follows:

[0176] (twenty two)

[0177] Therefore, the active power P of the load L and reactive power The following can be calculated:

[0178] (twenty three)

[0179] (twenty four)

[0180] for The average value, for The average value.

[0181] Next, based on the matching principle analysis and the relationship between power and impedance in formula (3), the desired impedance can be identified. The impedance is as follows:

[0182] (25)

[0183] Combining the load impedance expression identified in formula (25) with that in formula (12) The impedance function, the fixed impedance in formula (26) is used for fundamental matching, while the impedance in formula (12) is used for fundamental matching. The impedance is used for impedance matching of the remaining portion. Therefore, the duty cycle reference can be determined as:

[0184] (26)

[0185] Furthermore, due to parameter deviations and the influence of line parasitic parameters, an integrated system was developed. The module uses a calibrated duty cycle reference signal to improve matching accuracy. The identified signal is determined through comparison. The error between the impedance and the load impedance, and the calibration value Theoretical calculation results added to formula (26) Finally, the synthesized control quantity is used as a modulation reference, through unipolar... The method is as proposed Generate the final control signal.

[0186] This invention relates to the controllable source electromagnetic method ( A novel composite impedance matching network is proposed between the transmitter and the electromagnetic transducer. This invention addresses the problem of inductive reactive power occupancy and its adverse impact on transmission current intensity. Compared with existing impedance matching techniques, the proposed method... A novel combined matching method and related optimization design were adopted to improve broadband current transmission performance in terms of both compensation range and power loss. The proposed novel combined matching topology was explained through mathematical derivation and analysis, clarifying its corresponding broadband matching function. More importantly, it was combined with the controllable source electromagnetic method (…). To meet the requirements of broadband transmission and limited power supply conditions, a composite impedance matching network was designed. The proposed parameter optimization scheme and control strategy are compared with existing methods. Better fit The transmitter's wide operating frequency band increases the matching bandwidth and reduces power loss.

[0187] It will be understood by those skilled in the art that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A design method for a composite impedance matching network in a controlled-source electromagnetic exploration system, wherein the transmitting system of the controlled-source electromagnetic exploration system integrates the composite impedance matching network. The launching system is powered by a generator and equipped with a rectifier bridge diode. 、 、 、 ， The power inverter of the transmitting system is connected in series between the power inverter and the load. Bridge structure, made of Switching transistor 、 Switching transistor 、 Switching transistor 、 Switching transistor and parallel DC capacitor composition; The topology consists of fixed capacitors and series Partial composition, among which, Partially controlled by insulated-gate bipolar transistors Includes matching capacitors ,inductance and two connected in reverse series Composed of switches and switch ； The equivalent impedance is determined by the fixed capacitance. The impedance and controllability Impedance composition, characterized in that the design method includes the following steps: A. Constructing a system combining a fixed capacitor and an insulated-gate bipolar transistor for control. of Topological structure, and integrated into the launch system of the controlled-source electromagnetic exploration system; B, to carry out Equivalent impedance analysis, The equivalent impedance is determined by the fixed capacitance. The impedance and controllability Impedance composition, including fixed capacitance With a fixed impedance in part, it can provide constant impedance and reactive power compensation to achieve fundamental frequency matching; Some parts provide controllable impedance and reactive power compensation, which are controllable. Impedance can be adjusted by configuring the duty cycle control law, thereby achieving full impedance matching over a wide bandwidth; C. Optimization of parameters for controlled-source electromagnetic exploration system: Analyze the load impedance and determine the maximum matching impedance and minimum matching capacitance. and minimum matching impedance and maximum matching inductance The optimal parameter combination is obtained by minimizing power loss; D. The overall matching control optimization is designed, in which... The overall matching control includes power frequency identification, instantaneous power calculation, impedance determination, duty cycle control reference calculation, and matching function execution; by comparing and determining the identified frequency... The error between the impedance and the load impedance is calculated and corrected. The synthesized control quantity serves as the modulation reference, and is transmitted through a unipolar circuit. The method is Generate the final control signal; Step A, the transmitting system is powered by a generator and equipped with a rectifier bridge diode. 、 、 、 ， Connected in series between the power inverter and the load, the power inverter of the transmitting system adopts a traditional H-bridge structure, consisting of... Switching transistor 、 Switching transistor 、 Switching transistor 、 Switching transistor and parallel DC capacitor composition; The topology consists of fixed capacitors and series Partial composition, among which, Partially controlled by insulated-gate bipolar transistors Includes matching capacitors ,inductance and two connected in reverse series Composed of switches and switch ； The equivalent impedance is determined by the fixed capacitance. The impedance and controllability Impedance composition; Step B, controllable Impedance analysis specifically includes the following steps: B1, by controlling It operates in four modes, adjusting the equivalent impedance of the matching network: B2, via coordinated control switch. and switch The duty cycle of the pulse width modulation control signal controls each During the cycle, inductor L flows M The current ratio is used to indirectly control the parallel inductor branch and the entire circuit. Partial equivalent impedance value; B3, controlled by configuring the duty cycle control law. The equivalent impedance, thereby achieving full impedance matching over a wide bandwidth; in step B1, in Part, switch and switch The controllable state determines different impedance functions, and one operating cycle The internal operating modes are as follows: Mode 1: Switch and switch All are turned off in this mode. Some only match capacitors It works, and its impedance function is: In equation (7), The imaginary unit, Angular frequency; Mode 2: Switch On, switch When switched off, the inductor... With capacitor in parallel, The impedance function of part of the impedance can be expressed as: (8) Mode 3: Switch Off, switch During conduction, the inductor is excluded from matching, and its current is supplied by... The current continues and is approximately constant. The external impedance function is the same as formula (7) in mode 1; Mode 4: switch and switch All are conducting; at this time, The available impedance remains the same as in formula (7).

2. The design method of a composite impedance matching network for a controllable source electromagnetic exploration system according to claim 1, characterized in that, In step B2, it is assumed that the inductor The investment phase and the follow-up phase are respectively and Duty cycle is defined as Then, the total current increment of the equivalent inductance branch during the nth switching cycle is... This can be deduced as: In equation (9), For capacitor The voltage across the terminals; the cumulative current flowing through the equivalent inductance can be expressed as: (10) In addition, when the switch and switch When operating at high frequencies, the equivalent impedance of the inductor branch for: (11) Therefore, equivalent impedance Represented as: （12） 。 3. The design method of a composite impedance matching network for a controllable source electromagnetic exploration system according to claim 2, characterized in that, In step B3, impedance The function expression is further derived as follows: In equation (13), For fixed capacitor impedance, for The equivalent impedance, To match the capacitor, For inductance; the introduction of a switch makes It possesses a variable impedance function, thus transforming the traditional natural frequency into a continuously adjustable resonant frequency; according to the impedance function in formula (13), It can be characterized as a controllable reactor, integrated Total impedance of the transmitting system The function is shown in formula (14): In equation (14), For equivalent inductance, Let be the impedance of the load; therefore, It can provide a controllable negative imaginary part of impedance to cancel the positive imaginary part of the load impedance; when the transmitting system circuit is in a resonant state with zero imaginary part impedance, impedance matching is achieved, and the inherent matching frequency of the fixed capacitor section is a fixed value. ； The addition of parts The overall resonant frequency is controlled by the duty cycle, as shown in the following formula: （15） In the middle, the fixed capacitor part and The components can provide fixed reactive power compensation and controllable reactive power compensation respectively, and the two components together constitute... The total reactive power compensation is used to offset the reactive power introduced by the imaginary part of the impedance expression of formula (16) under wideband operation; In equation (16), for reactive power, For fixed capacitor reactive power, for The reactive power.

4. The design method of a composite impedance matching network for a controllable source electromagnetic exploration system according to claim 3, characterized in that, In step C, combining formula (12) The impedance function can be used to determine the maximum matching impedance and the minimum matching capacitance. As shown in the following formula: （17） Minimum matching impedance and maximum matching inductance As shown in the following formula: （18） ;definition and The impedance matching is shown in Equation (19), used to evaluate the fixed capacitor. Partial and Controllable Matching weights between parts ； In equation (19), To match capacitors The impedance.

5. The design method of a composite impedance matching network for a controllable source electromagnetic exploration system according to claim 4, characterized in that, Step D specifically includes the following steps: D1, Integration The controllable source electromagnetic exploration system performs frequency calculations on the power signal and measures the output voltage of the power inverter. Sample and transmit to The controller; D2 and the delay module, combined with the set threshold, complete the task. During the zero-crossing identification process, the controller's built-in timer continuously counts, and the durations of the on and off states within the m-th working cycle are recorded as follows: and The power supply frequency can be identified using the following expression: (20) D3, based on the load voltage obtained by sampling With load current The active power of the load is calculated using instantaneous power theory. L and reactive power ： In equation (21), 、 The sampled load voltages are respectively With load current Delay The signal obtained later To calculate the active power of the load L and reactive power The intermediate variable; the delay expression is as follows: (22) Active power of load L and reactive power The calculation is as follows: （23） In equation (24), for The average value, for The average value; D4, based on the matching principle analysis and the relationship between power and impedance in formula (3), the desired value is identified. The impedance is as follows: （3） (25) Combining the load impedance expression identified in formula (25) with that in formula (12) The impedance function, the fixed impedance in formula (26) is used for fundamental matching, while the impedance in formula (12) is used for fundamental matching. The impedance is used for impedance matching of the remaining portion; therefore, the duty cycle reference is determined as follows: (26) D5. Determine the identified by comparison The error between the impedance and the load impedance, and the calibration value Theoretical calculation results added to formula (26) Above; D6, the synthesized control quantity is used as the modulation reference, through unipolar The method is as proposed Generate the final control signal.

Images