阅读说明：本技术 一种电性源时变接地负载的测量和参数提取方法 (Method for measuring and extracting parameters of time-varying grounding load of electrical source ) 是由 嵇艳鞠 邱仕林 王世鹏 于一兵 吴琼 王远 李刚 于 2020-12-16 设计创作，主要内容包括：本发明涉及一种电性源时变接地负载的测量和参数提取方法,根据实际电性源工作方式和负载构成,建立电性源时变接地负载等效电路模型；分别采用1次恒压直流供电和多次不同频率的正弦交流供电激励,测量输出的电压和电流的幅值、相位；将电性源等效电路模型转换为相量模型,根据多次测量的数据建立目标函数并设定约束范围；采用粒子群归一算法实现参数提取,迭代过程中成比例调整最优解粒子的各维度位置,使各维度的约束范围在同一数量级；发射系统控制时序实现动态负载实时匹配。本发明的目的在于考虑了实际电性源负载的时变特性和复杂构成,能够保证正常工作时发射电流波形的线性度,提取结果有利于剔除数据中一次场和实现目标地下介质的反演。(The invention relates to a method for measuring and extracting parameters of a time-varying grounding load of an electrical source, which comprises the steps of establishing an equivalent circuit model of the time-varying grounding load of the electrical source according to the actual working mode of the electrical source and the composition of the load; respectively adopting 1 time of constant voltage direct current power supply and a plurality of times of sine alternating current power supply excitation with different frequencies to measure the amplitude and the phase of the output voltage and current; converting the equivalent circuit model of the electrical source into a phasor model, establishing a target function according to data measured for multiple times and setting a constraint range; parameter extraction is realized by adopting a particle swarm normalization algorithm, and the position of each dimension of the optimal solution particle is proportionally adjusted in an iterative process, so that the constraint range of each dimension is in the same order of magnitude; the transmitting system controls the time sequence to realize the real-time matching of the dynamic load. The invention aims to consider the time-varying characteristic and the complex composition of the actual electrical source load, ensure the linearity of the emission current waveform in normal work, and extract the result to be beneficial to eliminating the primary field in the data and realizing the inversion of the target underground medium.)

1. A method for measuring and parameter extracting of a time-varying grounding load of an electrical source is characterized by comprising the following steps:

1) laying long wires and measuring long wire inductance L and long wire resistance R_LTwo ends of the long lead are connected with the ground through electrode pits paved with tinfoil and poured with saline water, and are connected with the long lead through an electric source emission system through a generator;

2) establishing an electrical source load equivalent circuit model according to the composition of the electrical source load;

3) controlling the electric source emission system to provide constant voltage direct current to the electric source load, and measuring the direct current voltage value U through the voltage current sensor_dAnd the current value I through the long wire_d；

4) Controlling the electrical source emission system to provide n different frequencies omega to the electrical source load respectively₁，ω₂，……，ω_nN is more than or equal to 6, and the voltage amplitude of the alternating current corresponding to n frequencies is respectively measured by a voltage current sensorA value and a current amplitude through the long wire, and a voltage phase and a current phase;

5) converting the electric source load equivalent circuit model into a phasor model, setting an equation set under constant voltage direct current and n frequency sine alternating current excitation as a target function, setting an initial constraint range of each parameter according to the measurement results of the step 1), the step 3) and the step 4), and extracting 7 unknown parameters based on a particle swarm normalization algorithm;

6) repeating the steps 3) to 5) before work and at a working interval of every 1 hour, recording the time-varying grounding load parameters of the electrical source, and adjusting the control time sequence of the transmitting system to realize dynamic load matching, so that the transmitting current waveform keeps better linearity.

2. The method of claim 1, wherein the electrical source load equivalent circuit model in step 2) comprises a long lead inductance L and a long lead resistance R which can be directly measured_LAnd an unknown inter-electrode ground resistance R_eeAnd the contact impedances of the two grounding electrodes with the ground respectively, wherein the polarization characteristic of each contact impedance is represented by 3 parameters of a Debye model respectively, namely the polarization characteristic is represented by soil resistance R respectively_e1And a polarization capacitor C_p1And a polarization loop resistance R_p1First contact resistance formed and soil resistance R_e2And a polarization capacitor C_p2And a polarization loop resistance R_p2And the impedance phasor expression of the equivalent circuit model electrical source load equivalent circuit model is as follows:

in the formula, ω is a frequency.

3. The method as claimed in claim 2, wherein the step 3) of controlling the power source emission system to provide constant voltage direct current to the power source load, the measured voltage U of the power source load equivalent circuit model is in a steady state_dCurrent I_dThe relationship to the load is:

4. the method according to claim 2, wherein the alternating voltage amplitude U corresponding to n frequencies in the electrical source load equivalent circuit model in the step 4) is in a sine steady state_cnAnd the amplitude I of the current through the long conductor_cnAnd a phase corresponding to the voltagePhase corresponding to currentThe phasor relationship with the load is:

5. the method according to claim 1, wherein the group-of-particles normalization algorithm in step 5) comprises the steps of:

step I, constructing an equation set obtained in the step 3 and the step 4 in a simultaneous mode into an objective function, initializing the number, the position and the speed of population individuals, calculating the fitness of each particle, and initializing the optimal solution p of the individual_ijSetting an initial constraint range of position and speed by using the overall optimal solution pg, wherein the spatial dimension is 7 dimensions;

in the iterative process of the step II, calculating the fitness of each particle, and updating the speed and the position of the particle according to the following formula:

in the formula, c₁＝c₂2, is a learning factor; w is 0.6, which is the fitness; r is₁And r₂Is [0,1 ]]A uniform random number within a range;

in the iterative process of the step III, when the speed or the position of the particle exceeds the constraint range, the speed or the position is reassigned according to the upper limit or the lower limit of the constraint range, and simultaneously the individual optimal solution p is updated_ijAnd an overall optimal solution pg;

in the iteration process of the step IV, every time m iterations are carried out, the magnitude of each dimension value of 1 integral optimal solution pg is compared, and if 7 dimensions of the particle position exist, the maximum value is 10 of the minimum valueⁿN is more than or equal to 1 time, respectively in proportion of 10ⁿAdjusting the position and speed of the particle by more than or equal to 1 time to ensure that the constraint range of each dimension is in the same order of magnitude, and simultaneously adjusting the proportion corresponding to the dimension in the objective function;

step V, judging whether the maximum iteration times are reached or the fitness is smaller than a target value, if so, obtaining an overall optimal solution pg, and outputting an extracted parameter value; otherwise, returning to the step II to continue the execution.

Technical Field

The invention relates to the field of geophysical exploration, in particular to a method for measuring and extracting parameters of a time-varying grounding load of an electrical source.

Background

In the field of geophysical exploration, when an electrical source exploration method is adopted (particularly in a controlled source audio frequency magnetotelluric method (CSAMT), a Transient Electromagnetic Method (TEM) and a frequency domain induced polarization method (SIP)), a high-power transmitting system is generally adopted for supplying power, and large current is transmitted to the ground through a long lead to realize the excitation of an underground medium. In actual field work, the magnitude of the emission current and the turn-off time depend mainly on the load resistance, wherein the load resistance generally consists of the impedance of the power supply cable, the contact impedance of the ground electrode with the soil and the impedance of the underground geologic body. To increase the transmitted energy, the load resistance needs to be reduced, and the distance between the electrodes is determined by the detection scheme, so that only the contact impedance is the part that can be adjusted manually. In actual construction, a large-area grounding electrode and saline water are added to reduce contact resistance. In the past, it was generally thought that the resistance of the electrical source load resistor was constant. However, during operation, the current will cause the charged particles in the electrode pits to move, resulting in a polarization effect, so that the contact impedance will exhibit a capacitive behavior in addition to a resistive behavior. As the current level and time accumulate, heating of the ground electrode and loss of saline water both cause the contact resistance of the ground electrode to the soil to change. The electrical source load impedance which changes along with time not only affects the amplitude of the emission current, but also changes the turn-off time of the emission current and the waveforms of the rising edge and the falling edge, thereby affecting and interfering the processing of the subsequent measured data and being incapable of accurately rejecting the primary magnetic field. Therefore, it is necessary to establish an equivalent circuit model of the electrical source load impedance and accurately realize the measurement of the electrical source load and the extraction of the impedance parameter based on the hardware condition of the existing transmitting system.

Currently, in methods for measuring and extracting parameters of actual electrical source exploration loads, the most extensive method is to collect the amplitude of emission voltage and emission current in the exploration process and calculate load impedance according to ohm's law. The Liujun peak analyzes the arrangement method of the grounding resistance of the transmitting end of the electrical source, but the aim is to research how to reduce the contact resistance value, and neglect the treatment method of a large-area grounding electrode and adding saline water, the grounding resistance can be changed along with time. The law of change of soil resistivity under alternating current is widely researched in old literature, and although the method is only suitable for analysis of a transformer substation grounding network, the contact impedance of a grounding electrode and soil is related to the emission current density to a certain extent, so that the method has a polarization effect and is not constant.

CN106950432A discloses a method and a circuit for measuring multi-frequency inductance of a long earth surface conductor, in which a known voltage signal source is used to supply power to a series circuit of the long conductor and a standard resistor with known resistance, and the inductance and the resistance of the long conductor with two ends grounded are obtained by dc and ac power supply. However, the method is simple, the reactance of the long wire grounded at two ends is only formed by resistance and inductance, the parameter calculation method is too simple, and the complexity of the polarization effect of the contact impedance of the grounding electrode and the soil is ignored. For the electrical source load impedance, in addition to the influence of the impedance of the power supply long lead, the contact impedance of the ground electrode and the soil and the resistance of the underground geologic body are also considered.

CN111398686A discloses a ground resistance measuring system, which directly measures the ground resistance of a grounding device through a resistance measuring instrument, and compares the measured resistance value with the historical resistance measurement data in a database to determine the accuracy of the current measured resistance value. However, the method mainly solves the problem of storing and comparing the measurement data of the same measuring point, obviously, for the field of geophysical exploration, the exploration is performed in different regions in most cases, the load of an electrical source is different each time because of the difference of underground media and the rearrangement of a grounding electrode, so that the measured impedance is also stored and compared, and more importantly, the measurement method is improved and the impedance parameters of each structure are extracted.

Disclosure of Invention

The invention aims to establish an electrical source load equivalent circuit model aiming at the problems that the load measuring method of the existing electrical source transmitting system is too simple, the actual electrical source load is complex in structure, has a polarization effect and changes along with time, and provides a measuring and parameter extracting method of an electrical source time-varying grounding load based on the hardware condition of the existing transmitting system.

The present invention is achieved in such a way that,

a method for measuring and extracting parameters of a time-varying ground load of an electrical source, the method comprising:

1) laying long wires and measuring long wire inductance L and long wire resistance R_LTwo ends of the long lead are connected with the ground through electrode pits paved with tinfoil and poured with saline water, and are connected with the long lead through an electric source emission system through a generator;

2) establishing an electrical source load equivalent circuit model according to the composition of the electrical source load;

3) controlling the electric source emission system to provide constant voltage direct current to the electric source load, and measuring the direct current voltage value U through the voltage current sensor_dAnd the current value I through the long wire_d

4) Controlling the electrical source emission system to provide n different frequencies omega to the electrical source load respectively₁，ω₂，……，ω_nThe sine alternating current of (1), wherein n is more than or equal to 6, and alternating voltage amplitudes corresponding to n frequencies and current amplitudes passing through the long lead, as well as voltage phases and current phases are respectively measured through the voltage current sensor;

5) converting the electric source load equivalent circuit model into a phasor model, setting an equation set under constant voltage direct current and n frequency sine alternating current excitation as a target function, setting an initial constraint range of each parameter according to the measurement results of the step 1), the step 3) and the step 4), and extracting 7 unknown parameters based on a particle swarm normalization algorithm;

6) repeating the steps 3) to 5) before work and at a working interval of every 1 hour, recording the time-varying grounding load parameters of the electrical source, and adjusting the control time sequence of the transmitting system to realize dynamic load matching, so that the transmitting current waveform keeps better linearity.

Further, the equivalent circuit model of the electrical source load in the step 2) comprises the inductance L and the resistance R of the long lead wire, which can be directly measured_LAnd an unknown inter-electrode ground resistance R_eeAnd the contact impedances of the two grounding electrodes with the ground respectively, wherein the polarization characteristic of each contact impedance is represented by 3 parameters of a Debye model respectively, namely the polarization characteristic is represented by soil resistance R respectively_e1And a polarization capacitor C_p1And a polarization loop resistance R_p1First contact resistance formed and soil resistance R_e2And a polarization capacitor C_p2And a polarization loop resistance R_p2And the impedance phasor expression of the equivalent circuit model electrical source load equivalent circuit model is as follows:

in the formula, ω is a frequency.

Further, the electric source emission system is controlled to provide constant voltage direct current for the electric source load in the step 3), and the measured voltage U is obtained when the electric source load equivalent circuit model is in a stable state_dCurrent I_dThe relationship to the load is:

further, in the step 4), the alternating voltage amplitude U corresponding to n frequencies is obtained when the electrical source load equivalent circuit model is in the sine steady state_cnAnd the amplitude I of the current through the long conductor_cnAnd a phase corresponding to the voltagePhase corresponding to currentThe phasor relationship with the load is:

further, the particle group normalization algorithm in step 5) specifically includes the following steps:

step I, constructing an equation set obtained in the step 3 and the step 4 in a simultaneous mode into an objective function, initializing the number, the position and the speed of population individuals, calculating the fitness of each particle, and initializing the optimal solution p of the individual_ijSetting an initial constraint range of position and speed by using the overall optimal solution pg, wherein the spatial dimension is 7 dimensions;

in the iterative process of the step II, calculating the fitness of each particle, and updating the speed and the position of the particle according to the following formula:

in the formula, c₁＝c₂2, is a learning factor; w is 0.6, which is the fitness; r is₁And r₂Is [0,1 ]]A uniform random number within a range;

in the iterative process of the step III, when the speed or the position of the particle exceeds the constraint range, the speed or the position is reassigned according to the upper limit or the lower limit of the constraint range, and simultaneously the individual optimal solution p is updated_ijAnd an overall optimal solution pg;

in the iteration process of the step IV, every time m iterations are carried out, the magnitude of each dimension value of 1 integral optimal solution pg is compared, and if 7 dimensions of the particle position exist, the maximum value is 10 of the minimum valueⁿN is more than or equal to 1 time, respectively in proportion of 10ⁿAdjusting the position and speed of the particle by more than or equal to 1 time to ensure that the constraint range of each dimension is in the same order of magnitude, and simultaneously adjusting the proportion corresponding to the dimension in the objective function;

step V, judging whether the maximum iteration times are reached or the fitness is smaller than a target value, if so, obtaining an overall optimal solution pg, and outputting an extracted parameter value; otherwise, returning to the step II to continue the execution.

Compared with the prior art, the invention has the beneficial effects that:

compared with the traditional electrical source load measuring method, the measurement and parameter extraction method of the electrical source time-varying grounding load provided by the invention is more in line with the actual load composition and time-varying characteristics, provides an electrical source load equivalent circuit model, realizes the measurement of the electrical source time-varying grounding load and the extraction of model parameters based on various excitation modes and a particle swarm normalization algorithm, ensures the linearity and consistency of a transmitting current waveform through the dynamic matching of the electrical source transmitting system load, and is beneficial to eliminating a primary field in data and realizing the inversion of a target underground medium.

Drawings

FIG. 1 is a flow chart of a method for measuring and extracting parameters of a time varying grounding load of an electrical source;

FIG. 2 is a schematic diagram of an electrical source load equivalent circuit model;

FIG. 3 is a phasor diagram of an electrical source load equivalent circuit;

FIG. 4 is a flow chart of a particle swarm normalization algorithm;

FIG. 5 is a fitness curve of the parameter extraction results;

FIG. 6 is a comparison graph of current waveforms of the parameter extraction result of FIG. 5 and the original parameter under the same bipolar square wave voltage;

fig. 7 is a relative error of the two current waveforms of fig. 6.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

According to the invention, an electrical source load equivalent circuit model is established according to the structure of an actual electrical source load, voltage and current data under different conditions are obtained through measurement through direct current power supply and multi-frequency sine alternating current power supply excitation, the extraction of unknown parameters in the model is realized based on a particle swarm normalization algorithm, the accuracy of an extraction result is verified through comparison of a simulation current waveform of an electrical source emission system calculated based on the extraction result and an actual current waveform, and a flow chart is shown in figure 1.

The invention is realized in such a way that a method for measuring and extracting parameters of a time-varying grounding load of an electrical source comprises the following steps:

1) laying long wires and measuring long wire inductance L and long wire resistance R_LTwo ends of the long lead are connected with the ground through electrode pits paved with tinfoil and poured with saline water, and are connected with the long lead through an electric source emission system through a generator;

2) according to the composition of the electrical source load, an electrical source load equivalent circuit model is established, as shown in fig. 2. The model includes not only the inductance L of the long wire, which can be directly measured, but also the resistance R of the long wire_LAnd also comprises an unknown inter-electrode ground resistance R_eeAnd contact resistances of the two ground electrodes with the earth ground, respectively. The polarization characteristics of the contact impedance are respectively represented by 3 parameters of the Debye model, namely, respectively by the soil resistance R_e1And a polarization capacitor C_p1And a polarization loop resistance R_p1Contact resistance 1 and resistance of soil R_e2And a polarization capacitor C_p2And a polarization loop resistance R_p2The contact resistance 2 is formed. The impedance phasor of the equivalent circuit model is shown in fig. 3, and the phasor expression is:

in the formula, ω is a frequency.

According to the model principle, the ground resistance R between the electrodes_eeAnd the inductance L and the resistance R of the long lead_LThe parameters during steady operation are time invariant; ground electrode-to-ground contact resistance R_eThe effect of heating of the electrodes and loss of saline water can vary over time. For an electrical source emission system, there are two earth electrodes connected to earth, so the contact impedance of each electrode to earth is represented by the Debye model, respectively, in relation to frequency and time. Therefore, the long wire inductance L and the long wire resistance R are measured by the step 1_LExtracting 7 unknown parameters of the equivalent circuit model of the electrical source load through the steps 3-5, wherein the unknown parameters comprise the inter-electrode ground resistance R_eeSoil resistance R_e1And a polarization capacitor C_p1And a polarization loop resistance R_p1Soil resistance R_e2And a polarization capacitor C_p2And a polarization loop resistance R_p2。

3) Controlling the electric source emission system to provide constant voltage direct current to the electric source load, and measuring the direct current voltage value U through the voltage current sensor_dAnd the current value I through the long wire_dAt this time, the measured voltage U of the electric power source load equivalent circuit model is in a stable state_dCurrent I_dThe relationship to the load is:

4) controlling the electrical source emission system to provide n kinds (n is more than or equal to 6) of different frequencies (omega) to the electrical source load respectively₁，ω₂，……，ω_n) Respectively measuring the amplitude (U) of the AC voltage corresponding to n frequencies by a voltage current sensor_c1，U_c2，……，U_cn) And the magnitude of the current (I) through the long conductor_c1，I_c2，……，I_cn) And phase corresponding to voltagePhase corresponding to current At this time, under the sine steady state of the electrical source load equivalent circuit model, the phasor relationship between the measured data corresponding to the n frequencies and the load is as follows:

5) converting the equivalent circuit model of the electrical source load into a phasor modelConstant voltage DC and n different frequencies (omega)₁，ω₂，……，ω_n) Taking an equation set obtained under the excitation of sine alternating current as a target function, setting constraint ranges of all parameters according to the measurement results of the steps 1, 3 and 4, and extracting 7 unknown parameters based on a particle swarm normalization algorithm;

a flow chart of the particle swarm normalization algorithm is shown in fig. 4, and specifically includes the following steps:

i, constructing an equation set obtained in the step 3 and the step 4 in a simultaneous mode into an objective function, initializing the number, the position and the speed of population individuals, calculating the fitness of each particle, and initializing the optimal solution p of the individual_ijSetting an initial constraint range of position and speed by using the overall optimal solution pg, wherein the spatial dimension is 7 dimensions;

in the iteration process II, calculating the fitness of each particle, and updating the speed and the position of the particle according to the following formula:

in the formula, c₁＝c₂2, is a learning factor; w is 0.6, which is the fitness; r is₁And r₂Is [0,1 ]]A uniform random number within the range.

In the III iteration process, when the speed or the position of the particle exceeds the constraint range, the speed or the position is reassigned according to the upper limit or the lower limit of the constraint range, and simultaneously the individual optimal solution p is updated_ijAnd an overall optimal solution pg;

in the iv iteration process, every m iterations (generally, m is 50), the magnitude of each dimension value of 1 overall optimal solution pg is compared, and if the maximum value is 10 of the minimum value in 7 dimensions of the particle position, the maximum value is 10 of the minimum valueⁿ(n is more than or equal to 1) times, then the ratio is respectively 10ⁿ(n is more than or equal to 1) times, adjusting the position and the speed of the particles to ensure that the constraint range of each dimension is in the same order of magnitude, and simultaneously adjusting the proportion corresponding to the dimension in the objective function;

judging whether the maximum iteration times are reached or the fitness is smaller than a target value, if so, obtaining an overall optimal solution pg, and outputting an extracted parameter value; otherwise, returning to the step II to continue the execution.

6) Repeating the steps 3 to 5 before working and at a working interval of every 1 hour, recording the time-varying grounding load parameters of the electrical source, and adjusting the control time sequence of the transmitting system to realize dynamic load matching, so that the transmitting current waveform keeps better linearity, a guarantee is provided for the subsequent processing of electromagnetic detection data, and the inversion of underground media is facilitated.

The parameters of the electrical source load equivalent circuit model are as follows: l1 × 10^-3H，R_L＝10Ω，R_ee＝5Ω，R_e1＝10Ω，C_p1＝1×10^-4F，R_p1＝10Ω，R_e2＝5Ω，C_p2＝1×10^-3F，R_p25 Ω. Based on the above method, the electrical source load is measured and parameters are extracted, and the fitness curve is shown in fig. 5. And the comparison of the extracted result and the current waveform of the original parameter under the same bipolar square wave voltage is compared, as shown in fig. 6. Fig. 7 is the relative error of the two.