CN112130025A - Differential-to-single-ended sampling device for platform area topology identification - Google Patents
Differential-to-single-ended sampling device for platform area topology identification Download PDFInfo
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- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract
The invention discloses a differential-to-single-ended sampling device for district topology identification, and belongs to the technical field of district topology identification of electric low-voltage distribution networks. The device of the invention comprises: the device comprises a current front-end alternating current circuit, a voltage front-end alternating current circuit, a sampling resistor, a metering chip and a first-order filter circuit, wherein the first-order filter circuit performs first-order filtering on a topological differential signal, performs reverse amplification and direct-current forward-bias voltage signal processing on the topological differential signal after the first-order filtering, performs lifting and secondary reverse amplification processing after the processing is completed, and outputs a single-ended signal with a positive and unchangeable waveform; the operational amplifier reference power supply is used for adding a direct current positive bias voltage signal to the topological differential signal; and the MCU access interface is used for accessing the single-ended signal through an AD sampling pin of the MCU access interface, outputting the single-ended signal and outputting the single-ended signal to a target unit. The operational amplifier does not need negative power supply support.
Description
Technical Field
The invention relates to the technical field of power low-voltage distribution network district topology identification, in particular to a differential-to-single-ended sampling device for district topology identification.
Background
With the increasingly strict requirements of the national power grid company on the fine management of the panoramic perception of the low-voltage power distribution network and the requirements of the power grid company on the comprehensive improvement of the low-voltage distribution network management, a device with topology recognition and transmission is additionally arranged in the existing distribution network, the real-time and accurate report of a topology structure is realized, the full recognition and full communication of the topological relation of variable-line-branch-meter box is realized, and the method is a key development direction of the low-voltage power distribution network at the present stage and in a period of the future.
At present, node equipment installed in different areas such as a transformer side-branch side-surface box side of a three-level structure in an existing transformer area has a common characteristic; the method has the advantages of having both the alternate mining function and the topology identification function. This requires that the hardware must support both functions. The design of the existing hardware for the part is mainly realized by adopting a mode of sharing front-end sampling and separating rear-end signal processing, namely sharing a front-end mutual inductor, and dividing the signals into an alternate acquisition signal circuit and a topology identification circuit for processing after entering a device. The main chip of the alternate signal circuit and the main chip of the topology identification circuit have different emphasis points on functions and can be selected differently, so that the signal processing circuits of the alternate signal circuit and the topology identification circuit are inconsistent, and auxiliary power supplies and operational amplifier processing parts can be added. Creating redundancy in circuit design. Because the requirements of the existing platform area equipment on volume and cost are more and more strict, the existing circuit needs to be improved, the product cost is reduced, the product volume is reduced, and the competitiveness is improved while the product functionality is realized.
The current stage of platform area products such as a line monitoring terminal, a small shunt intersection acquisition unit, a meter box monitoring terminal, a modular terminal, an intelligent fusion terminal and the like are all provided with a metering sampling function and a topology identification function. The realization of the two functions is realized by two functional modules, namely a metering sampling circuit and an MCU sampling circuit at present; after secondary sampling signals of external voltage and current are converted into standard positive and negative differential signals, the signals are divided into two signals, 1 path of signals are input to sampling of the MCU to realize a topology identification function, and 1 path of signals are input to sampling of a metering chip to realize a metering data monitoring function. Because most AD input pins of the existing MCU are single-ended input and do not support differential input, a high-performance MCU with differential input must be selected to realize the functions, otherwise, the differential signal of the path needs to be converted into a single-ended signal and then enters the AD, the conversion from the differential signal to the single-ended signal is realized by dual-power operational amplifier and must be realized by two-stage operational amplifier, otherwise, the voltage of the signal input end changes, which causes the error of the metering signal of the other path, the common processing method is that the first-stage operational amplifier is used for realizing the reverse amplification of the differential signal, and the second-stage amplifier is used for realizing the lifting and re-amplification of the signal, and the high impedance function of the first-stage and the second-stage amplifier is adopted. So that the first stage input signal is not affected. The circuit is more complicated when the design is limited, and the circuit complexity is increased if the circuit is used for sampling multiple paths of voltage and current (under a branch monitoring environment).
Disclosure of Invention
In view of the above problem, the present invention provides a differential-to-single-ended sampling apparatus for a station area identification apparatus, including:
the current front-end alternating current acquisition circuit acquires a secondary sampling signal of current;
the voltage front-end alternating current acquisition circuit acquires a secondary sampling signal of the voltage;
the sampling resistor collects positive and negative differential signals and performs difference on the positive and negative differential signals to obtain two paths of differential signals;
the metering chip meters the metering differential signal;
the first-order filter circuit performs first-order filtering on the topological differential signal, performs reverse amplification and direct-current forward bias voltage signal processing on the topological differential signal subjected to the first-order filtering, performs lifting and secondary reverse amplification processing after the processing is completed, and outputs a single-ended signal with a positive and unchangeable waveform;
the operational amplifier reference power supply is used for adding a direct current positive bias voltage signal to the topological differential signal;
and the MCU access interface is used for accessing the single-ended signal through an AD sampling pin of the MCU access interface, outputting the single-ended signal and outputting the single-ended signal to a target unit.
Optionally, the metering differential signal and the topology differential signal respectively include: voltage and current metering differential signals, and voltage and current topological differential signals.
Optionally, the metering chip is internally integrated with 7 paths of 19-bit a/D converters, the voltage value range is ± 700mV, and the effective value of the current channel is in the range of 0.1mV to 500 mV.
Optionally, the secondary sampling signal for collecting the voltage/current is collected by adopting a voltage transformer PT isolation mode.
Optionally, the output end of the MCU access interface is connected in series with 1 resistor with a resistance of at least 10 ohms, and the output impedance is not greater than 10 ohms.
Optionally, the output range of the single-ended signal is 0-3.3V.
According to the invention, the differential signal is used for lifting at the output end, and the signal entering the operational amplifier is positive, so that the operational amplifier does not need the support of a negative power supply, devices of the negative power supply are correspondingly reduced by the circuit, and the dual functions of alternate mining metering and topology identification are respectively realized by the same circuit.
Drawings
Fig. 1 is a structural diagram of a differential-to-single-ended sampling apparatus for identifying a distribution room topology according to the present invention.
FIG. 2 is a schematic diagram of a current front-end interleaved sampling circuit according to an embodiment of a differential-to-single-ended sampling apparatus for station area topology identification according to the present invention;
FIG. 3 is a schematic diagram of a sampling resistor of a current front-end interleaved sampling circuit according to an embodiment of the differential-to-single-ended sampling apparatus for platform topology identification of the present invention;
FIG. 4 is a schematic diagram of an operational amplifier circuit of a current front-end interleaved sampling circuit according to an embodiment of the differential-to-single-ended sampling apparatus for station area topology identification of the present invention;
FIG. 5 is a schematic diagram of a voltage front-end interleaved sampling circuit according to an embodiment of the differential-to-single-ended sampling apparatus for platform topology identification of the present invention;
FIG. 6 is a schematic diagram of a sampling resistor of a voltage front-end interleaved circuit according to an embodiment of the differential-to-single-ended sampling apparatus for platform topology identification of the present invention;
fig. 7 is a schematic diagram of an operational amplifier circuit of a voltage front-end interleaved sampling circuit according to an embodiment of the differential-to-single-ended sampling apparatus for station area topology identification of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
The invention provides a differential-to-single-ended sampling device for station area topology identification, as shown in fig. 1, comprising:
the current front-end alternating current acquisition circuit acquires a secondary sampling signal of current;
the voltage front-end alternating current acquisition circuit acquires a secondary sampling signal of the voltage;
the sampling resistor collects positive and negative differential signals and performs difference on the positive and negative differential signals to obtain two paths of differential signals;
the metering chip meters the metering differential signal;
the first-order filter circuit performs first-order filtering on the topological differential signal, performs reverse amplification and direct-current forward bias voltage signal processing on the topological differential signal subjected to the first-order filtering, performs lifting and secondary reverse amplification processing after the processing is completed, and outputs a single-ended signal with a positive and unchangeable waveform;
the operational amplifier reference power supply is used for adding a direct current positive bias voltage signal to the topological differential signal;
and the MCU access interface is used for accessing the single-ended signal through an AD sampling pin of the MCU access interface, outputting the single-ended signal and outputting the single-ended signal to a target unit.
A metering differential signal and a topological differential signal, each comprising: voltage and current metering differential signals, and voltage and current topological differential signals.
The metering chip is internally integrated with 7 paths of 19-bit A/D converters, the voltage value range is +/-700 mV, and the effective value of a current channel is in the range of 0.1mV to 500 mV.
And acquiring secondary sampling signals of voltage/current by adopting a voltage transformer PT isolation mode.
The MCU access interface output end is connected with 1 resistor with the resistance value of at least 10 ohms in series, and the output impedance is not more than 10 ohms.
The output range of the single-ended signal is 0-3.3V.
According to the invention, the differential signal is used for lifting at the output end, and the signal entering the operational amplifier is positive, so that the operational amplifier does not need the support of a negative power supply, devices of the negative power supply are correspondingly reduced by the circuit, and the dual functions of alternate mining metering and topology identification are respectively realized by the same circuit.
The invention is further illustrated by the following examples:
a current front-end alternating current circuit is shown in the principle of fig. 2, 3 and 4, IA and IA-are secondary side sampling differential signals of an external current transformer, R122 and R125 are sampling resistors, R121+ C52 and R130+ C58 are first-order low-pass filter circuits, and V28 and V29 are bidirectional sequential-change suppressors.
The principle of the voltage front-end alternating current circuit is shown in fig. 5, 6 and 7, VA1+ and VA 1-are secondary side sampling differential signals of a voltage current transformer, R31 and R36 are sampling resistors, R30+ C16 and R39+ C19 are first-order low-pass filter circuits, and V4 and V5 are bidirectional sequential suppressor.
The operational amplifier reference power supply comprises: the single channel D40D and the voltage dividing resistors R825 and R820 of the operational amplifier SGM8270 form a voltage follower circuit, and the current output capacity of the direct-current bias voltage Vref _ U1 is improved. The single channel D41D of the operational amplifier SGM8270 and the voltage dividing resistors R827 and R826 form a voltage follower circuit, and the current output capacity of the direct current bias voltage Vref _ U2 is improved.
An access interface of the MCU, comprising: the output impedance of the topology identification operational amplifier circuit of current and voltage can be approximate to 0, and the output end is connected with 1 resistor with 10 ohms in series, so the output impedance can be approximate to 10 ohms, and the input impedance of the 12-bit ADC input port of the MCU is required to be not more than dozens of ohms and meets the requirement.
And (3) determining the value of the alternating current input sampling resistor:
the amplitude of the differential alternating current signal converted into the differential voltage signal by the sampling resistor must be within the input range of the metering chip, a 7-path 19-bit A/D converter is integrated in the general metering chip, the voltage value range is +/-700 mV, and the linear error of the effective value of a current channel is less than 0.1% within the range of 0.1mV to 500 mV;
the linear error of the effective value of the voltage channel is less than 0.1% in the range of 0.2mV to 500 mV; the effective value of the voltage is 0.2V to 0.5V (the amplified voltage value is that a voltage sampling signal is 0.1V, and the amplification factor of a voltage channel is selected to be 2 times), the value of the current is 0.2mV to 500mV, and the linear error of the electric energy is less than 0.1%;
the terminal requires that the rated secondary side current of the external current transformer is 100mA, and the rated primary side current of the external current transformer is 125A, 160A, 250A, 400A and 600A, so that the maximum rated transformation ratio is 6000:1, 1.2 times of the rated current is considered, the maximum current detection value is 700A, and the corresponding rated secondary current is 120 mA;
therefore, the maximum value of the rated current of the secondary side of the current transformer CT is 120/0.707 to 169.7mA, and the maximum sampling peak value of the voltage of the measuring chip is 700mV, so that the maximum value of the sampling resistance is 700/120 × 0.707 to 4.124 Ω, and considering the differential input sampling, the maximum value of a single resistance is 2.062 Ω, and a high-precision columnar resistance of 2 Ω is taken.
And (3) determining the value of the alternating voltage input sampling resistor:
the voltage transformer PT isolation mode is adopted in the alternating-current mining voltage sampling, 2mA/2mA 0.1-level 10mA is selected for the voltage transformer specification, the metering program is basically not changed, the alternating-current mining voltage front-end sampling circuit adopts a mature circuit used by the existing terminal sensing terminal, and circuit parameters are calculated as follows:
PT primary sampling current I is 380V/265k is 1.44mA (considering 1.732 times of overvoltage), the sampling resistor is 30 Ω, and the differential sampling voltage is: ± 43.2 × 2 ═ 86.4 mV.
On the basis of not weakening the function, the invention improves the circuit design of the common topology identification and alternative acquisition operational amplifier, does not need to adopt an MCU with a differential output function, simultaneously reduces the usage amount of an operational amplifier chip and an accessory circuit by 50 percent, simultaneously removes the design of a negative power supply, realizes the conversion of a differential signal into a single-ended double sampling signal by using a single operational amplifier, realizes the defect-free amplification of the differential signal by using the single operational amplifier of a single power supply, simultaneously does not change the amplitude characteristic of a front-end signal, and can realize the functions of metering sampling and topology identification double sampling by using one operational amplifier and the single power supply.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The scheme in the embodiment of the application can be implemented by adopting various computer languages, such as object-oriented programming language Java and transliterated scripting language JavaScript.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.
Claims (6)
1. A differential to single-ended sampling apparatus for use in site topology identification, the apparatus comprising:
the current front-end alternating current acquisition circuit acquires a secondary sampling signal of current;
the voltage front-end alternating current acquisition circuit acquires a secondary sampling signal of the voltage;
the sampling resistor collects positive and negative differential signals and performs difference on the positive and negative differential signals to obtain two paths of differential signals;
the metering chip meters the metering differential signal;
the first-order filter circuit performs first-order filtering on the topological differential signal, performs reverse amplification and direct-current forward bias voltage signal processing on the topological differential signal subjected to the first-order filtering, performs lifting and secondary reverse amplification processing after the processing is completed, and outputs a single-ended signal with a positive and unchangeable waveform;
the operational amplifier reference power supply is used for adding a direct current positive bias voltage signal to the topological differential signal;
and the MCU access interface is used for accessing the single-ended signal through an AD sampling pin of the MCU access interface, outputting the single-ended signal and outputting the single-ended signal to a target unit.
2. The apparatus of claim 1, the metering differential signal and the topological differential signal each comprising: voltage and current metering differential signals, and voltage and current topological differential signals.
3. The device of claim 1, wherein the metering chip is integrated with a 7-way 19-bit a/D converter, the voltage range is ± 700mV, and the effective value of the current channel is in the range of 0.1mV to 500 mV.
4. The device according to claim 1, wherein the voltage/current sampling signal is acquired in a voltage transformer PT isolation manner.
5. The device of claim 1, wherein the MCU access interface output terminal is connected in series with 1 resistor having a resistance of at least 10 ohms, and the output impedance is no greater than 10 ohms.
6. The apparatus of claim 1, wherein the single-ended signal has an output range of 0-3.3V.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113406414A (en) * | 2021-06-07 | 2021-09-17 | 云南电网有限责任公司 | Low-voltage transformer area shunt monitoring device and wave recording and fault studying and judging method thereof |
| CN113726329A (en) * | 2021-09-23 | 2021-11-30 | 合肥埃科光电科技有限公司 | Self-adaptive single-ended and differential signal input interface circuit |
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| CN109217478A (en) * | 2018-11-19 | 2019-01-15 | 深圳市均方根科技有限公司 | Low-voltage platform area topological relation recognition methods, concentrator and storage medium |
| CN210037958U (en) * | 2019-01-31 | 2020-02-07 | 洛阳隆盛科技有限责任公司 | Voltage isolation sampling circuit |
| CN111157783A (en) * | 2019-12-28 | 2020-05-15 | 杭州拓深科技有限公司 | Control system for common acquisition of differential signal and waveform data |
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