CN115718214A - Voltage measurement method and device - Google Patents
Voltage measurement method and device Download PDFInfo
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- CN115718214A CN115718214A CN202211433780.XA CN202211433780A CN115718214A CN 115718214 A CN115718214 A CN 115718214A CN 202211433780 A CN202211433780 A CN 202211433780A CN 115718214 A CN115718214 A CN 115718214A
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Abstract
The application relates to a voltage measurement method and device. The method comprises the following steps: acquiring a single-probe electric field distribution model, and acquiring a single-probe equivalent circuit according to the single-probe electric field distribution model; based on the single-probe equivalent circuit, obtaining a double-probe electric field distribution model for representing the two conditions of the number of the D-dot sensors, and establishing the double-probe equivalent circuit according to the double-probe electric field distribution model; configuring a charge amplification loop based on the double-probe equivalent circuit; a harmonic power supply is introduced into a charge amplification loop to obtain a voltage signal output by an operational amplification unit, and the voltage signal is decomposed by using a frequency spectrum to determine equivalent capacitance parameters between a single-phase line and two D-dot sensors; and (3) processing the equivalent capacitance parameters by adopting a fundamental wave equation at the frequency point of the power frequency power supply to obtain the voltage of the single-phase line to the ground. The method and the device realize effective calibration of the dielectric constant and reduce errors of voltage measurement.
Description
Technical Field
The present application relates to the field of voltage measurement technologies, and in particular, to a voltage measurement method and apparatus.
Background
With the large-scale expansion of the internet engineering of each region and the large-scale grid connection of various distributed power supplies, china forms a countable super-large-scale complex power grid in the world, and needs more electric power system electric quantity monitoring data to ensure the safe operation and scheduling of the power grid. Meanwhile, the rapid development of the 5G (5 Generation) communication technology and artificial intelligence lays a foundation for efficient data transmission and processing, and the key point is to deploy a large amount of electrical data monitoring devices in the system for realizing the construction of a smart power grid with highly transparent electric power data.
At present, a common electrical data monitoring device is a D-dot sensor, however, a conventional D-dot sensor is easily affected by environmental changes, such as weather changes and changes in the distance between a phase line and a probe, which all cause changes in parameters required for measurement, and an effective dielectric constant calibration means is not available, so that a large voltage measurement error is generated.
Disclosure of Invention
In view of the above, it is necessary to provide a voltage measurement method and apparatus capable of dynamically setting a capacitance parameter and improving voltage measurement accuracy.
In a first aspect, the present application provides a voltage measurement method. The method is applied to a voltage measuring device; the voltage measuring device comprises a charge amplifying unit, an operational amplifying unit and a signal processing loop which are connected in sequence; the charge amplification unit is used for being connected with a D-dot sensor, the D-dot sensor is arranged on a grounding tower, and the grounding tower is connected with a single-phase line; the method comprises the following steps:
acquiring a single-probe electric field distribution model, and acquiring a single-probe equivalent circuit according to the single-probe electric field distribution model; the single-probe electric field distribution model is used for representing the distribution conditions of electric fields of the single-phase line, the grounding tower, the D-dot sensors and the power frequency power supply under the condition that the number of the D-dot sensors is one;
based on the single-probe equivalent circuit, obtaining a double-probe electric field distribution model for representing the two conditions of the number of the D-dot sensors, and establishing the double-probe equivalent circuit according to the double-probe electric field distribution model;
configuring a charge amplification circuit based on the double-probe equivalent circuit so as to respectively convert displacement currents between the single-phase line and the two D-dot sensors into conduction currents to flow into the charge amplification circuit;
a harmonic power supply is introduced into a charge amplification loop, a voltage signal output by an operational amplification unit is obtained, the voltage signal is decomposed by using a frequency spectrum, and equivalent capacitance parameters between a single-phase line and two D-dot sensors are determined;
and (3) processing the equivalent capacitance parameters by adopting a fundamental wave equation at the frequency point of the power frequency power supply to obtain the voltage of the single-phase line to the ground.
In one embodiment, the step of configuring the charge amplification circuit based on the dual probe equivalent circuit comprises:
determining a voltage measurement model according to the double-probe equivalent circuit; the voltage measurement model is used for characterizing the configuration condition of the charge amplification unit in the case of a charge amplifier with a differential structure;
according to the voltage measurement model, the number of charge amplifiers is configured to be two, and the non-inverting input terminal of each charge amplifier is configured to be grounded.
In one embodiment, the step of obtaining the output voltage signal of the operational amplifier unit by introducing a harmonic power supply into the charge amplification loop includes:
the non-inverting input of each charge amplifier is configured to be grounded through a harmonic power supply.
In one embodiment, the two D-dot sensors are respectively a first probe and a second probe, and the step of acquiring the voltage signal output by the operational amplifier unit includes:
based on the double-probe equivalent circuit, under the condition that the frequency of the harmonic power supply is omega 1, the following formulas are adopted to obtain a first probe output voltage signal and a second probe output voltage signal:
wherein, VR (j ω 1) is the voltage signal output by the harmonic power supply under the frequency of ω 1; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency; c1 is a capacitor between the single-phase line and the first probe; cs1 is the capacitance of the first probe and the second probe to the ground; u1 (j ω 1) is the first probe output voltage signal at ω 1 frequency; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measurement device; u2 (j ω 1) is the second probe output voltage signal at ω 1 frequency; c2 is the capacitance between the single-phase line and the second probe;
based on the first probe output voltage signal and the second probe output voltage signal, the output voltage signal of the operational amplifier unit is obtained by adopting the following formula:
wherein, U0 (j ω 1) is a voltage signal output by the operational amplifier unit under the frequency of ω 1; a is the amplification gain of the operational amplifier unit; VR (j ω 1) is the voltage signal output by the harmonic power supply at ω 1 frequency; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency; c1 is a capacitor between the single-phase line and the first probe; c2 is a capacitor between the single-phase line and the second probe; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measuring device.
In one embodiment, the step of determining the equivalent capacitance parameter between the single-phase line and the two D-dot sensors by using the frequency spectrum to decompose the voltage signal comprises the following steps:
under the condition that the frequency of the harmonic power supply is omega 1, a voltage signal is decomposed by using a frequency spectrum to obtain a Discrete sampling signal, and a component on the frequency omega 1 of the Discrete sampling signal after DFT (Discrete Fourier Transform) operation is obtained by adopting the following formula:
wherein u0 (n) is a discrete sampling signal; n is an arbitrary constant; Δ t is the sampling interval of the discrete sampled signal;
the method is a component of a discrete sampling signal on a frequency omega 1 after DFT operation;
under the condition that the frequency of the harmonic power supply is omega 1, the harmonic power supply is decomposed by using a frequency spectrum, e1 (n) is set as a unit signal which has the same frequency and phase with the decomposed harmonic power supply, and the component of the unit signal on the frequency omega 1 after DFT operation is obtained by adopting the following formula:
wherein N is an arbitrary constant; Δ t is the sampling interval of the unit signal;
is a component of a unit signal on a frequency omega 1 after DFT operation;
based on the component of the discrete sampling signal on the frequency omega 1 after the DFT operation and the component of the unit signal on the frequency omega 1 after the DFT operation, the voltage signal output by the operational amplifier unit is obtained by adopting the following formula:
wherein, the first and the second end of the pipe are connected with each other,
and U0 (j omega 1) are voltage signals output by the operational amplifier unit, and the difference is that the acquisition modes are different;
the discrete sampling signal is subjected to DFT operation and then is subjected to component on frequency omega 1;
is a component of a unit signal on a frequency omega 1 after DFT operation;
based on two formulas for obtaining voltage signals output by the operational amplifier unit, obtaining equivalent capacitance parameters:
wherein C1 is a capacitor between the single-phase line and the first probe; c2 is the capacitance between the single-phase line and the second probe; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measurement device; a is the amplification gain of the operational amplifier unit; VR (j ω 1) is the voltage signal output by the harmonic power supply at the frequency ω 1; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency;
the method is a component of a discrete sampling signal on a frequency omega 1 after DFT operation;
is the component of the unit signal at the frequency ω 1 after the DFT operation.
In one embodiment, at a frequency point of a power frequency power supply, a fundamental wave equation is adopted to process equivalent capacitance parameters to obtain the voltage of the single-phase line to the ground, and the voltage of the single-phase line to the ground is obtained by adopting the following formula:
wherein the content of the first and second substances,
voltage of single-phase line to ground under frequency omega 0; omega 0 is fundamental frequency; ω 1 is the harmonic frequency; j omega 0 is a fundamental component of the unidirectional line output voltage under omega 0 frequency; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measurement device;
is the frequency component of the discrete sampled signal at frequency ω 0;
the method is a component of a discrete sampling signal on a frequency omega 1 after DFT operation;
is a component of a unit signal on a frequency omega 1 after DFT operation; VR (j ω 1) is the voltage signal output by the harmonic power supply at the frequency ω 1.
In a second aspect, the present application further provides a voltage measurement device. The device comprises a charge amplification unit, an operational amplification unit and a signal processing loop which are connected in sequence; the charge amplification unit is used for being connected with a D-dot sensor, the D-dot sensor is arranged on a grounding tower, and the grounding tower is connected with a single-phase line; the voltage measuring device also comprises a first resistor, a second resistor, a first capacitor and a second capacitor;
the charge amplifying unit includes a first charge amplifier and a second charge amplifier;
the operational amplifier unit comprises a differential operational amplifier; the number of the D-dot sensors is two, and the D-dot sensors are respectively a first probe and a second probe;
the inverting input end of the first charge amplifier is connected with the output end of the first probe and used for receiving the conduction current output by the first probe, the inverting input end of the first charge amplifier is also connected with the inverting input end of the differential operational amplifier through a first resistor and a first capacitor respectively, the non-inverting input end of the first charge amplifier is used for grounding, and the output end of the first charge amplifier is connected with the inverting input end of the differential operational amplifier;
the inverting input end of the second charge amplifier is connected with the output end of the second probe and used for receiving the conduction current output by the second probe, the inverting input end of the second charge amplifier is also connected with the positive phase input end of the differential operational amplifier through a second resistor and a second capacitor respectively, and the positive phase input end of the second charge amplifier is used for being grounded.
In a third aspect, the present application also provides a computer-readable storage medium. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, is adapted to carry out the above-mentioned voltage measurement method.
In a fourth aspect, the present application further provides a computer program product. Computer program product comprising a computer program for implementing the voltage measurement method as described above when executed by a processor.
According to the voltage measuring method and the voltage measuring device, the double-probe equivalent circuit is established from the single-probe equivalent circuit, the measuring principle of the double-probe equivalent circuit is deduced, the harmonic power supply is introduced into the charge amplification circuit, the dynamic setting of the capacitance parameters is realized, the equivalent capacitance parameters obtained by solving are processed by adopting the fundamental wave equation, and the voltage of the single-phase circuit to the ground is obtained.
Drawings
FIG. 1 is a schematic flow chart of a voltage measurement method according to an embodiment;
FIG. 2 is a block diagram of a D-dot sensor probe in accordance with one embodiment;
FIG. 3 is a diagram illustrating the configuration of a single probe electric field distribution model in one embodiment;
FIG. 4a is an electric field distribution diagram of a single probe electric field distribution model in one embodiment;
FIG. 4b is a circuit diagram of a single probe equivalent circuit in one embodiment;
FIG. 5a is a schematic diagram of a measurement of a single probe electric field distribution model in one embodiment;
FIG. 5b is a diagram of an equivalent measurement circuit of a single-probe electric field distribution model in one embodiment;
FIG. 6 is a diagram illustrating the configuration of a model of the electric field distribution of the dual probe apparatus in one embodiment;
FIG. 7 is a diagram of an equivalent measurement circuit of a two-probe electric field distribution model in one embodiment;
FIG. 8 is a diagram of an equivalent measurement circuit of a dual probe electric field distribution model after a harmonic power supply is added in one embodiment;
fig. 9 is an internal structural view of a voltage measuring device in one embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first resistance may be referred to as a second resistance, and similarly, a second resistance may be referred to as a first resistance, without departing from the scope of the present application. The first resistance and the second resistance are both resistances, but they are not the same resistance.
It is to be understood that "connection" in the following embodiments is to be understood as "electrical connection", "communication connection", and the like if the connected circuits, modules, units, and the like have communication of electrical signals or data with each other.
As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," or "having," and the like, specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.
The traditional electromagnetic voltage transformer has the defects of large volume, high manufacturing cost, inconvenient installation and the like, and is difficult to be widely deployed in a power system, so that the research and development of the miniature voltage sensor and the high adaptability to the field environment are very urgent.
In the conventional technology, the field-based non-contact voltage measurement is a voltage measurement technology which is not in direct electrical contact with a power line and equipment, and miniaturization is easy to realize. At present, the research on the technology at home and abroad is divided into three categories, which are respectively as follows: field measurement techniques based on the photoelectric effect, MEMS-based field measurement techniques, and floating body capacitance-based field measurement techniques. The field measurement technology based on the photoelectric effect is difficult to be applied to field voltage measurement due to the difficulties that the crystal is sensitive to temperature change, the discrete elements are difficult to fix and the like; the field measurement technology based on the MEMS is developed rapidly, domestic and foreign teams focus on researching the field measurement technology based on the MEMS, the parameter setting research is rarely carried out, and the dynamic parameter setting is difficult to realize due to the complex transfer function, so that the field measurement technology based on the MEMS brings larger measurement error when being used in the actual environment. The field measurement technology based on the floating body capacitance has the advantages of small volume, simple probe forming, simple transfer function formed with the measured environment and the like, so that the field measurement technology has the potential of being widely deployed in a power grid.
The D-dot sensor is a representative of the application of the floating body capacitance field measurement technology, and has the capacity of measuring high voltage and even impulse voltage by means of the erection mode of the D-dot sensor far away from a live conductor. However, both domestic and foreign research on D-dot has been focused on laboratory environments, where the position between the probe and the live conductor is fixed, the field source voltage is pushed back by the electric field inversion problem, or the high-voltage probe is used to measure the high-voltage bus data during the initial erection of the device, and the data is used to implement parameter setting. In fact, a harsh condition is required for the above two methods to be effective, namely: the influence of environmental changes is ignored. However, the field environment is variable, such as weather changes, distance changes between the phase line and the probe, and the like, all cause the parameters required for measurement to change, and thus large voltage measurement errors are generated.
The voltage measuring device with the differential structure is arranged, and the mechanism for realizing voltage measurement and the environment common-mode interference resisting mechanism are analyzed. On the basis, the dynamic setting of the capacitance parameters is realized by utilizing the harmonic source and the differential structure, the voltage measurement method suitable for the D-dot sensor and capable of dynamically setting the capacitance parameters is provided, and the voltage measurement error can be reduced under the conditions that the weather changes frequently and the phase line and the D-dot probe are displaced relatively.
In one embodiment, as shown in fig. 1, a voltage measurement method is provided, which is applied to a voltage measurement device; the voltage measuring device comprises a charge amplifying unit, an operational amplifying unit and a signal processing loop which are connected in sequence; the charge amplification unit is used for being connected with a D-dot sensor, the D-dot sensor is arranged on a grounding tower, and the grounding tower is connected with a single-phase line; the method comprises the following steps:
s102, acquiring a single-probe electric field distribution model, and acquiring a single-probe equivalent circuit according to the single-probe electric field distribution model; the single-probe electric field distribution model is used for representing the distribution conditions of electric fields of the single-phase line, the grounding tower, the D-dot sensor and the power frequency power supply under the condition that the number of the D-dot sensors is one.
Fig. 2 is a structural diagram of a D-dot sensor probe, and as shown in fig. 2, the probe in the present application may be a circular PCB substrate, the upper surface of which is coated with copper, the lower surface of which is coated with a silica gel layer as an insulating substrate, and the radius of the probe is 4cm. Fig. 3 is an erection diagram of a single-probe electric field distribution model, as shown in fig. 3, a probe is disposed on an iron support of a grounding tower, the iron support of the grounding tower is grounded through a contact net, the probe is perforated and connected with a coaxial wire, an insulating medium is covered on the surface of the coaxial wire, the outgoing wire is connected with a measuring device, and the measuring device is also grounded through the contact net, that is, the measuring device and an electric power system are grounded together.
In addition, as shown in fig. 4a, phase a in the figure may refer to a single-phase line, and as shown in fig. 4b, the single-phase conductor has an electric flux to ground, which may be equivalent to that the single-phase conductor has a coupling capacitance Cd (corresponding to D2 in fig. 4 a) to ground; the single-phase lead has electric flux for coating copper on the upper surface, and can be equivalent to a coupling capacitor C (corresponding to D in 4 a) between the single-phase lead and the D-dot probe; in addition, because the copper-clad part on the upper surface of the probe takes the PCB substrate and the silica gel coating as insulating media and is directly arranged on the iron support of the grounding tower, and a layer of polarized surface charge still exists between the insulating media layers, the electric flux still exists between the copper-clad part on the upper surface of the probe and the iron support (ground), which can be equivalent to an equivalent capacitor Cs (corresponding to D1 in 4 a) between the probe and the ground, UA can represent the voltage of a single-phase line to the ground, and the connection relationship among the capacitors is shown in the figure.
Further, the voltage measurement principle of a single probe can be derived, as shown in fig. 5a, in the figure, phase a may refer to a single-phase line, and assuming that the normal direction of the gaussian surface S is an external normal, the conduction current flowing into the measurement apparatus is obtained by maxwell' S full current law:
wherein the content of the first and second substances,
and i1 is the conduction current flowing into the measurement device;
is the displacement current between the single line pair probes;
the displacement current, which is the probe leakage to ground, can be considered as an error amount. To eliminate this error, the positive terminal of the charge amplifier of the measurement circuit is grounded, so that the probe potential is zero, and thus the displacement current of the probe leakage to ground is zero.
To facilitate quantitative analysis, as shown in fig. 5b, starting from the perspective of the path, a formula for solving the voltage of the single-phase power line is obtained:
i1＝U A ·jω 0 ·C
that is to say that the first and second electrodes,
wherein i1 is the conduction current flowing into the measurement device; u shape A A voltage to ground for the unidirectional line; j omega 0 Outputting fundamental wave components of the voltage under omega 0 frequency for the unidirectional line; c is the capacitance between the single-phase line and the probe; UO (j ω) 0 ) For the voltage signal output by the operational amplifier unit at omega 0 frequency(UO); rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measuring device.
The above derivation shows that: the voltage of the single-phase line to the ground can be estimated by only accurately measuring the equivalent capacitance (C) between the probe and the single-phase line pair and measuring the fundamental component of the output voltage.
In practice the equivalent capacitance (C) between the single phase line and the probe cannot be measured in field situations and this parameter tends to vary with the relative distance between the single phase line and the probe and with the variation of the spatial permittivity; in addition, in order to enable all displacement electricity between the single-phase line and the probe to be converted into conduction current to flow into the measuring device, the positive polarity end of the charge amplifier is directly grounded, so that the bias current can also influence a voltage signal output by the operational amplifier unit, and errors are brought to measurement; finally, common-mode noise and far-field interference often exist in the environment, and measurement accuracy is affected. In summary, a single charge sensor is difficult to realize the functions of parameter dynamic setting and environmental common mode interference resistance, and the measurement precision is difficult to ensure.
S104, based on the single-probe equivalent circuit, obtaining a double-probe electric field distribution model for representing two D-dot sensors, and establishing the double-probe equivalent circuit according to the double-probe electric field distribution model.
Specifically, as shown in fig. 6, the electric field distribution model of the dual probe is similar to that of the single probe, and the only difference is that the equivalent capacitance formed by the single-phase line and the two probes is different due to the inconsistent height of the dual probe deployment, and if the resistance of the outgoing line is neglected, the mutual capacitance between the first probe and the second probe can be equivalent to that of the single-phase line and the two probes.
And S106, configuring a charge amplification loop based on the double-probe equivalent circuit to respectively convert the displacement current between the single-phase line and the two D-dot sensors into conduction currents to flow into the charge amplification loop.
Specifically, the voltage measurement principle of the dual probe is derived based on the dual probe equivalent circuit, as shown in fig. 7, the single-phase wire has an electric flux to the upper surface of the first probe, which is equivalent to a coupling capacitor (C1) existing between the single-phase wire and the first probe; the single-phase lead has electric flux to the upper surface of the second probe, and equivalently, a coupling capacitor (C2) exists between the single-phase lead and the second probe; the single-phase wire has electric flux to the ground, and equivalently, a coupling capacitor (Cd) exists between the single-phase wire and the ground; the upper surface of the first probe has electric flux to the ground, and the electric flux is equivalent to a first equivalent capacitor (Cs 1 below C1) between the first probe and the ground; the upper surface of the second probe has electric flux to the ground, which is equivalent to the fact that a second equivalent capacitor (Cs 1 below C2) exists between the second probe and the ground, UA is the voltage of a single-phase line to the ground, a mutual capacitor (Cm) exists between the first probe and the second probe, A1 and A2 are charge amplifiers, A3 is an operational amplifier unit, A1 and A2 have similar structures, internal Rx and Cx have the same size, so the internal Rx and Cx are represented by the same letter, and Cs1 has the same principle.
In one embodiment, the step of configuring the charge amplification circuit based on the dual probe equivalent circuit comprises:
determining a voltage measurement model according to the double-probe equivalent circuit; the voltage measurement model is used for characterizing the configuration condition of the charge amplification unit in the case of a charge amplifier with a differential structure;
according to the voltage measurement model, the number of charge amplifiers is configured to be two, and the non-inverting input terminal of each charge amplifier is configured to be grounded.
Specifically, as shown in fig. 7, since the non-inverting input terminals of the two charge amplifiers (A1 and A2) are configured to be grounded, displacement currents between the single-phase line and the dual probe can be converted into conduction currents flowing into different charge amplifiers by the two probes, respectively, and the formula for solving the voltage of the single-phase power line based on the above acquisition can be obtained:
wherein, the first and the second end of the pipe are connected with each other,
and
outputting a voltage signal for the first probe at a frequency of ω 0;
and
outputting a voltage signal for the second probe at the frequency ω 0; j omega 0 is a fundamental component of the unidirectional line output voltage under omega 0 frequency; u shape A Voltage to ground for the unidirectional line; a is the amplification gain of the operational amplifier unit; c1 is a capacitor between the single-phase line and the first probe; c2 is a capacitor between the single-phase line and the second probe; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measuring device.
The only problem that exists today is that the capacitance parameters (C1 and C2) between the single phase line and the dual probe are unknown.
And S108, introducing a harmonic power supply into the charge amplification loop, acquiring a voltage signal output by the operational amplification unit, decomposing the voltage signal by using a frequency spectrum, and determining equivalent capacitance parameters between the single-phase line and the two D-dot sensors.
Specifically, in order to set capacitance parameters C2 and C1 formed between a single-phase line and a double probe in real time, the dynamic setting of equivalent capacitance parameters is realized by introducing a harmonic source.
In one embodiment, the step of obtaining the output voltage signal of the operational amplifier unit by introducing a harmonic power supply into the charge amplification loop includes:
the non-inverting input of each charge amplifier is configured to be grounded through a harmonic power supply.
Specifically, as shown in fig. 8, a harmonic power supply (VR) is connected in series to the common non-inverting input of the charge amplifier, and the amplitude and phase angle of the harmonic power supply are controllable and can be regarded as known quantities. From the superposition theorem, the output response of the measuring device can be regarded as a superposition when acted upon by a plurality of excitation sources, respectively. When the harmonic power supply works alone, the potential of the single-phase line is zero, A1 and A2 in FIG. 8 are similar in structure, and Rx and Cx in the single-phase line are the same in size, so the same letters are used for representing the potential, and Cs1 is the same in principle.
In one embodiment, as shown in fig. 8, the step of acquiring the voltage signal output by the operational amplifier unit includes:
based on the double-probe equivalent circuit, under the condition that the frequency of the harmonic power supply is omega 1, the following formulas are adopted to obtain a first probe output voltage signal and a second probe output voltage signal:
wherein, VR (j ω 1) is the voltage signal output by the harmonic power supply under the frequency of ω 1; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency; c1 is a capacitor between the single-phase line and the first probe; cs1 is the capacitance of the first probe and the second probe to the ground; u1 (j ω 1) is the first probe output voltage signal at ω 1 frequency; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measurement device; u2 (j ω 1) is the second probe output voltage signal at ω 1 frequency; c2 is a capacitor between the single-phase line and the second probe;
based on the first probe output voltage signal and the second probe output voltage signal, the output voltage signal of the operational amplifier unit is obtained by adopting the following formula:
wherein, U0 (j ω 1) is a voltage signal output by the operational amplifier unit under the frequency of ω 1; a is the amplification gain of the operational amplifier unit; VR (j ω 1) is the voltage signal output by the harmonic power supply at ω 1 frequency; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency; c1 is a capacitor between the single-phase line and the first probe; c2 is the capacitance between the single-phase line and the second probe; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measuring device.
Specifically, in the present embodiment, as shown in fig. 8, by using the differential structure of the op-amp unit, the variable Cs1 is eliminated.
In one embodiment, as shown in fig. 8, the step of determining the equivalent capacitance parameter between the single-phase line and the two D-dot sensors by using the spectrum decomposition voltage signal comprises:
under the condition that the frequency of the harmonic power supply is omega 1, a voltage signal is decomposed by using a frequency spectrum to obtain a discrete sampling signal, and the component of the discrete sampling signal on the frequency omega 1 after DFT operation is obtained by adopting the following formula:
wherein u0 (n) is a discrete sampling signal; n is an arbitrary constant; Δ t is the sampling interval of the discrete sampled signal;
the discrete sampling signal is subjected to DFT operation and then is subjected to component on frequency omega 1;
under the condition that the frequency of the harmonic power supply is omega 1, the harmonic power supply is decomposed by using a frequency spectrum, e1 (n) is set as a unit signal which has the same frequency and phase with the decomposed harmonic power supply, and the component of the unit signal on the frequency omega 1 after DFT operation is obtained by adopting the following formula:
wherein N is an arbitrary constant; Δ t is the sampling interval of the unit signal;
is a component of a unit signal on a frequency omega 1 after DFT operation;
based on the component of the discrete sampling signal on the frequency omega 1 after the DFT operation and the component of the unit signal on the frequency omega 1 after the DFT operation, the voltage signal output by the operational amplifier unit is obtained by using the following formula:
wherein the content of the first and second substances,
and U0 (j omega 1) are voltage signals output by the operational amplifier unit, and the difference is that the acquisition modes are different;
the discrete sampling signal is subjected to DFT operation and then is subjected to component on frequency omega 1;
is a component on a frequency omega 1 after a unit signal is subjected to DFT operation;
based on two formulas for obtaining voltage signals output by the operational amplifier unit, obtaining equivalent capacitance parameters:
wherein, C1 is the capacitance between the single-phase line and the first probe; c2 is a capacitor between the single-phase line and the second probe; rx is a voltage measuring deviceA centering resistor; cx is the capacitance in the voltage measurement device; a is the amplification gain of the operational amplifier unit; VR (j ω 1) is the voltage signal output by the harmonic power supply at ω 1 frequency; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency;
the discrete sampling signal is subjected to DFT operation and then is subjected to component on frequency omega 1;
is the component of the unit signal at frequency ω 1 after the DFT operation.
Specifically, it is assumed that a discrete sampling signal of the voltage signal output by the operational amplifier unit in a time window T1 — (T1 + N · Δ T) is u0 (N), where a sampling interval is Δ T and a sampling window length is N. Is provided with
The method is a component of a discrete sampling signal u0 (N) on a frequency omega 1 after DFT operation in a time window T1- (T1 + N.DELTA T); let el (N) be a unit signal (amplitude of 1) with same frequency and phase as the harmonic power supply VR in the time window T1- (T1 + N.DELTA T), let el (N) be set
After the discrete sampling signal e1 (N) is subjected to DFT operation in the time window T1 — (T1 + N · Δ T), the equivalent capacitance parameter is obtained by using the component at the frequency ω 1.
And S110, processing equivalent capacitance parameters by adopting a fundamental wave equation at the frequency point of the power frequency power supply to obtain the voltage of the single-phase line to the ground.
Specifically, the power frequency power supply can refer to a mains supply signal with the frequency of 50Hz, the frequency point of the power frequency power supply is obtained through DFT, and frequency spectrum offset is not considered in the application.
In one embodiment, at a frequency point of a power frequency power supply, a fundamental wave equation is adopted to process equivalent capacitance parameters to obtain the voltage of the single-phase line to the ground, and the voltage of the single-phase line to the ground is obtained by adopting the following formula:
wherein, the first and the second end of the pipe are connected with each other,
voltage of single-phase line to ground under frequency omega 0; omega 0 is fundamental frequency; ω 1 is the harmonic frequency; j omega 0 is a fundamental component of the unidirectional line output voltage under omega 0 frequency; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measurement device;
is the frequency component of the discrete sampled signal at frequency ω 0;
the method is a component of a discrete sampling signal on a frequency omega 1 after DFT operation;
is a component of a unit signal on a frequency omega 1 after DFT operation; VR (j ω 1) is the voltage signal output by the harmonic power supply at the frequency ω 1.
Specifically, the formula in this embodiment can also be written as:
wherein the content of the first and second substances,
voltage of single-phase line to ground under frequency omega 0; omega 0 is the fundamental frequency; ω 1 is the harmonic frequency; j omega 0 is a fundamental component of the unidirectional line output voltage under omega 0 frequency; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measurement device;
is the frequency component of the discrete sampled signal at frequency ω 0;
the method is a component of a discrete sampling signal on a frequency omega 1 after DFT operation;
is a component of a unit signal on a frequency omega 1 after DFT operation; VR (j ω 1) is the voltage signal of the harmonic power supply output at the ω 1 frequency.
According to the voltage measurement method, a double-probe equivalent circuit is established from a single-probe equivalent circuit, the measurement principle of the double-probe equivalent circuit is deduced, a harmonic power supply is introduced into a charge amplification loop, the dynamic setting of capacitance parameters is realized, the equivalent capacitance parameters obtained by solving are processed by adopting a fundamental wave equation, the voltage of a single-phase line to the ground is obtained, the effective calibration of the dielectric constant is realized, and the error of voltage measurement is reduced.
In one embodiment, the present application further provides a voltage measurement device. As shown in fig. 9, the apparatus includes a charge amplifying unit, an operational amplifying unit, and a signal processing circuit, which are connected in sequence; the charge amplification unit is used for being connected with a D-dot sensor, the D-dot sensor is arranged on a grounding tower, and the grounding tower is connected with a single-phase line; the voltage measuring device further comprises a first resistor (Rx 1), a second resistor (Rx 2), a first capacitor (Cx 1) and a second capacitor (Cx 2);
the charge amplifying unit includes a first charge amplifier (A1) and a second charge amplifier (A2);
the operational amplifier unit comprises a differential operational amplifier (A3); the number of the D-dot sensors is two, and the D-dot sensors are respectively a first probe and a second probe;
the inverting input end of the first charge amplifier is connected with the output end of the first probe and used for receiving the conduction current output by the first probe, the inverting input end of the first charge amplifier is also connected with the inverting input end of the differential operational amplifier through a first resistor and a first capacitor respectively, the non-inverting input end of the first charge amplifier is used for grounding, and the output end of the first charge amplifier is connected with the inverting input end of the differential operational amplifier;
the inverting input end of the second charge amplifier is connected with the output end of the second probe and used for receiving the conduction current output by the second probe, the inverting input end of the second charge amplifier is also connected with the positive phase input end of the differential operational amplifier through a second resistor and a second capacitor respectively, and the positive phase input end of the second charge amplifier is used for being grounded.
Specifically, as shown in fig. 9, the non-inverting input terminals of the two charge amplifiers are configured to be grounded, that is, a mutual capacitance exists between the first probe and the second probe, the two charge amplifiers can be decoupled and independent from each other, and because the two charge amplifiers have the same parameter and are symmetrical in structure, when common mode interference (voltage offset caused by temperature and far field electric field interference) enters the measurement system through the dual probe, the common mode interference generates the same output signals (equal amplitude and same phase) at the output terminals of the two charge amplifiers, and the output terminal signal of the signal processing circuit after the signal passes through the differential operational amplifier becomes 0, so that the common mode interference signal can be filtered, and the voltage measurement error can be reduced.
It should be understood that, although the steps in the flowcharts related to the embodiments are shown in sequence as indicated by the arrows, the steps are not necessarily executed in sequence as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least a part of the steps in the flowcharts related to the above embodiments may include multiple steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of performing the steps or stages is not necessarily sequential, but may be performed alternately or alternately with other steps or at least a part of the steps or stages in other steps.
In an embodiment, a computer-readable storage medium is provided, on which a computer program is stored, which computer program, when being executed by a processor, is adapted to carry out the above-mentioned voltage measurement method.
In an embodiment, a computer program product is provided, comprising a computer program for implementing the voltage measurement method described above when executed by a processor.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above may be implemented by hardware instructions of a computer program, which may be stored in a non-volatile computer-readable storage medium, and when executed, may include the processes of the embodiments of the methods described above. Any reference to memory, database, or other medium used in the embodiments provided herein may include at least one of non-volatile and volatile memory. The nonvolatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical Memory, high-density embedded nonvolatile Memory, resistive Random Access Memory (ReRAM), magnetic Random Access Memory (MRAM), ferroelectric Random Access Memory (FRAM), phase Change Memory (PCM), graphene Memory, and the like. Volatile Memory can include Random Access Memory (RAM), external cache Memory, and the like. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), among others. The databases referred to in various embodiments provided herein may include at least one of relational and non-relational databases. The non-relational database may include, but is not limited to, a block chain based distributed database, and the like. The processors referred to in the various embodiments provided herein may be, without limitation, general purpose processors, central processing units, graphics processors, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, or the like.
All possible combinations of the technical features in the above embodiments may not be described for the sake of brevity, but should be considered as being within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is specific and detailed, but not construed as limiting the scope of the present application. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.
Claims (10)
1. A voltage measurement method is characterized in that the method is applied to a voltage measurement device; the voltage measuring device comprises a charge amplifying unit, an operational amplifying unit and a signal processing loop which are connected in sequence; the charge amplification unit is used for being connected with a D-dot sensor, the D-dot sensor is arranged on a grounding tower, and the grounding tower is connected with a single-phase line; the method comprises the following steps:
acquiring a single-probe electric field distribution model, and acquiring a single-probe equivalent circuit according to the single-probe electric field distribution model; the single-probe electric field distribution model is used for representing the distribution conditions of the electric fields of the single-phase line, the grounding tower, the D-dot sensors and the power frequency power supply under the condition that the number of the D-dot sensors is one;
based on the single-probe equivalent circuit, obtaining a double-probe electric field distribution model for representing the two D-dot sensors, and establishing a double-probe equivalent circuit according to the double-probe electric field distribution model;
configuring the charge amplification circuit based on the double-probe equivalent circuit so as to respectively convert displacement currents between the single-phase line and the two D-dot sensors into conduction currents to flow into the charge amplification circuit;
a harmonic power supply is introduced into the charge amplification loop to obtain a voltage signal output by the operational amplification unit, the voltage signal is decomposed by using a frequency spectrum, and equivalent capacitance parameters between the single-phase line and the two D-dot sensors are determined;
and processing the equivalent capacitance parameters by adopting a fundamental wave equation at the frequency point of the power frequency power supply to obtain the voltage of the single-phase line to the ground.
2. The method of claim 1, wherein the step of configuring the charge amplification circuit based on the dual probe equivalent circuit comprises:
determining a voltage measurement model according to the double-probe equivalent circuit; the voltage measurement model is used for characterizing the configuration condition of the charge amplification unit in the case of a charge amplifier with a differential structure;
according to the voltage measurement model, the number of the charge amplifiers is configured to be two, and a non-inverting input terminal of each of the charge amplifiers is configured to be grounded.
3. The method of claim 2, wherein the step of obtaining the output voltage signal of the op-amp cell by introducing a harmonic power supply in the charge amplification loop comprises:
the non-inverting input of each of the charge amplifiers is configured to be grounded through the harmonic power supply.
4. The method according to any one of claims 1 to 3, wherein the two D-dot sensors are a first probe and a second probe, respectively, and the step of acquiring the voltage signal output by the operational amplifier unit comprises:
based on the double-probe equivalent circuit, under the condition that the frequency of the harmonic power supply is ω 1, acquiring the first probe output voltage signal and the second probe output voltage signal by adopting the following formulas:
wherein VR (j ω 1) is a voltage signal output by the harmonic power supply at a frequency of ω 1; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency; c1 is the capacitance between the single-phase line and the first probe; cs1 is the capacitance of the first probe and the second probe to the ground; u1 (j ω 1) is the first probe output voltage signal at ω 1 frequency; rx is a resistance in the voltage measuring device; cx is the capacitance in the voltage measurement device; u2 (j ω 1) is the second probe output voltage signal at ω 1 frequency; c2 is the capacitance between the single-phase line and the second probe;
based on the first probe output voltage signal and the second probe output voltage signal, obtaining an output voltage signal of the operational amplifier unit by adopting the following formula:
wherein, U0 (j ω 1) is a voltage signal output by the operational amplifier unit under ω 1 frequency; a is the amplification gain of the operational amplifier unit; VR (j ω 1) is the voltage signal output by the harmonic power supply at ω 1 frequency; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency; c1 is the capacitance between the single-phase line and the first probe; c2 is the capacitance between the single-phase line and the second probe; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measurement device.
5. The method of claim 4, wherein the step of spectrally decomposing the voltage signal to determine an equivalent capacitance parameter between the single-phase line and the two D-dot sensors comprises:
under the condition that the frequency of the harmonic power supply is omega 1, decomposing the voltage signal by using a frequency spectrum to obtain a discrete sampling signal, and obtaining a component on the frequency omega 1 of the discrete sampling signal after DFT operation by adopting the following formula:
wherein u0 (n) is the discrete sampled signal; n is an arbitrary constant; Δ t is the sampling interval of the discrete sampling signal;
performing DFT operation on the discrete sampling signal to obtain a component at a frequency omega 1;
under the condition that the frequency of the harmonic power supply is omega 1, decomposing the harmonic power supply by using a frequency spectrum, setting e1 (n) as a unit signal with the same frequency and phase as the decomposed harmonic power supply, and acquiring a component on the frequency omega 1 of the unit signal after DFT operation by adopting the following formula:
wherein N is an arbitrary constant; Δ t is a sampling interval of the unit signal;
the component of the unit signal on the frequency omega 1 after DFT operation;
based on the component of the discrete sampling signal at the frequency ω 1 after the DFT operation and the component of the unit signal at the frequency ω 1 after the DFT operation, the voltage signal output by the operational amplifier unit is obtained by using the following formula:
wherein, the first and the second end of the pipe are connected with each other,
and U0 (j omega 1) are voltage signals output by the operational amplifier unit, and the difference is that the obtaining mode is different;
performing DFT operation on the discrete sampling signal to obtain a component at a frequency omega 1;
the component of the unit signal on the frequency omega 1 after DFT operation;
based on two formulas for obtaining the voltage signal output by the operational amplifier unit, obtaining the equivalent capacitance parameter:
wherein C1 is the capacitance between the single-phase line and the first probe; c2 is the capacitance between the single-phase line and the second probe; rx is a resistance in the voltage measuring device; cx is the capacitance in the voltage measurement device; a is the amplification gain of the operational amplifier unit; VR (j ω 1) is the voltage signal output by the harmonic power supply at the ω 1 frequency; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency;
the discrete sampling signal is subjected to DFT operation and then is subjected to component at frequency omega 1;
is the unit signal channelAfter the DFT operation, the component at the frequency ω 1.
6. The method according to claim 5, wherein in the step of obtaining the voltage of the single-phase line to the ground by processing the equivalent capacitance parameter with a fundamental wave equation at the frequency point of the power frequency power supply, the voltage of the single-phase line to the ground is obtained with a formula as follows:
wherein, the first and the second end of the pipe are connected with each other,
is the voltage of the single-phase line to ground at frequency ω 0; omega 0 is fundamental frequency; ω 1 is the harmonic frequency; j ω 0 is a fundamental component of the unidirectional line output voltage at ω 0 frequency; j omega 1 is a fundamental component of the unidirectional line output voltage under omega 1 frequency; rx is the resistance in the voltage measuring device; cx is the capacitance in the voltage measurement device;
is a frequency component of the discrete sampled signal at frequency ω 0;
performing DFT operation on the discrete sampling signal to obtain a component at a frequency omega 1;
the component of the unit signal on the frequency omega 1 after DFT operation; VR (j ω 1) is the voltage signal output by the harmonic power supply at the ω 1 frequency.
7. A voltage measuring device characterized in that the device is applied to the voltage measuring method according to any one of claims 1 to 6; the voltage measuring device comprises a charge amplifying unit, an operational amplifying unit and a signal processing loop which are connected in sequence; the charge amplification unit is used for accessing the D-dot sensor; the D-dot sensor is arranged on a grounding tower, and the grounding tower is connected with a single-phase line; the voltage measuring device further comprises a first resistor, a second resistor, a first capacitor and a second capacitor;
the charge amplifying unit includes a first charge amplifier and a second charge amplifier; the operational amplifier unit comprises a differential operational amplifier; the number of the D-dot sensors is two, and the two D-dot sensors are respectively a first probe and a second probe;
the inverting input end of the first charge amplifier is connected with the output end of the first probe and is used for receiving the conduction current output by the first probe, the inverting input end of the first charge amplifier is also connected with the inverting input end of the differential operational amplifier through the first resistor and the first capacitor respectively, the non-inverting input end of the first charge amplifier is used for grounding, and the output end of the first charge amplifier is connected with the inverting input end of the differential operational amplifier;
the inverting input terminal of the second charge amplifier is connected to the output terminal of the second probe and is configured to receive the conduction current output by the second probe, the inverting input terminal of the second charge amplifier is further connected to the positive input terminal of the differential operational amplifier through the second resistor and the second capacitor, respectively, and the positive input terminal of the second charge amplifier is configured to be grounded.
8. The apparatus of claim 7, wherein the first charge amplifier and the second charge amplifier are parametric identical and structurally symmetric charge amplifiers.
9. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 6.
10. A computer program product comprising a computer program, characterized in that the computer program realizes the steps of the method of any one of claims 1 to 6 when executed by a processor.
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