CN202748407U - Low-cost single-phase harmonic electric energy meter - Google Patents
Low-cost single-phase harmonic electric energy meter Download PDFInfo
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- CN202748407U CN202748407U CN 201220320437 CN201220320437U CN202748407U CN 202748407 U CN202748407 U CN 202748407U CN 201220320437 CN201220320437 CN 201220320437 CN 201220320437 U CN201220320437 U CN 201220320437U CN 202748407 U CN202748407 U CN 202748407U
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Abstract
The utility model discloses a low-cost single-phase harmonic electric energy meter, which comprises a sampling and metering part, a storage part, a main control unit MCU, a power supply part, a communication part and a display part, and which is characterized in that: current and voltage signals are sampled by the sampling and metering part at front end, one path of the current signal is delivered into a metering chip via a low-pass filter while the other path of the current signal enters the metering chip directly, the voltage sampling signal enters the metering chip directly, and a fundamental current signal, a total current signal, a voltage signal, fundamental electric energy and total electric energy are obtained by metering of the metering chip. The low-cost single-phase harmonic electric energy meter disclosed by the utility model is rational in structure and solves the problem that harmonic metering cannot be accomplished by a common electric energy meter with no specific harmonic metering chip used therein.
Description
Technical field
The utility model relates to a kind of single-phase harmonic electric energy meter.
Background technology
Along with the development of science and technology, the raising of commercial production and living standards of the people, non-linear electrical equipment puts into operation in electrical network in a large number, and the proportion that has caused the harmonic component of electrical network to account for is increasing.It has not only increased the current supply loss of electrical network, and disturbs the protective device of electrical network and the normal operation of automation equipment, has caused malfunction and the tripping of these devices, directly threatens the safe operation of electrical network.The quality of the quality of power supply directly has influence on the quality of industrial products, so we must administer the harmonic wave that non-linear electrical equipment produces, and this just requires us at first will finish the metering of harmonic wave.
At present, most electric energy meters on the market do not possess the harmonic wave function of measuring, CN101382588A discloses a kind of patent of harmonic electric energy meter, the harmonic electric energy metering module of this harmonic electric energy meter comprises voltage, current transformation unit and DSP computing module, and the DSP computing module comprises the compensating module of amplitude and the phase place of FFT conversion module and harmonic parameters.Namely this harmonic electric energy meter metering harmonic wave needs special-purpose metering units, needs high-speed sampling and adopts complicated digital signal processing just can obtain the information such as harmonic electric energy in inside.This is to the design of harmonic electric energy meter, and the selection of sampling A/D chip is limited to very much, and cost is very high, is unfavorable for promoting the use of of harmonic electric energy meter.
The utility model content
It is a kind of rational in infrastructure that the purpose of this utility model is to provide, and has the low-cost single-phase harmonic electric energy meter of the function of accurate-metering harmonic wave.
Technical solution of the present utility model is:
The single-phase harmonic electric energy meter of a kind of low cost, comprise sampling metering section, storage area, main control unit MCU, power unit, communications portion, display part, it is characterized in that: sampling metering section front-end sampling obtains current and voltage signals, one road current signal is sent into computation chip after by low-pass filter, another road current signal directly enters computation chip, voltage sampling signal directly enters computation chip, measure by computation chip and to obtain fundamental current signal and total current signal, voltage signal, fundamental energy, total electric energy.
The 4 rank wave filters that described low-pass filter is comprised of two two rank Low-pass Elliptic Filter cascades, each two rank elliptic filter cooperates some resistance capacitances to form by three single operational amplifiers, two operational amplifiers wherein cooperate corresponding resistor electric capacity to realize the function of the oval filtering in two rank, the voltage gain of another single operational amplifier is 1, its input resistance levels off to infinite, output resistance levels off to zero, in the middle of circuit, as voltage follower, realize the isolation of two rank elliptic filters and output.
First two rank elliptic filter in two two rank Low-pass Elliptic Filters is by operational amplifier U1, U2, U3, resistance R 1, R2, R3, R4, R5, R6, capacitor C 1, C2 form, the positive input terminal ground connection of operational amplifier, negative input termination signal, signal are from the input of R1 end, and the other end of R1 and C1 series connection cooperate U1 to form the single order low-pass filtering, R2 and C2 series connection form again first-order filtering with U2, and wherein R1, C1 equate with the value of R2, C2 respectively; The resistance R 4 of U2 two terminations is negative feedback resistors, makes system works stable; R5, R6 and U3 as voltage follower, realize the isolation of two rank elliptic filters and output in the middle of circuit, the end of R3 is connected in the output of U3, and the other end is connected to the negative input end of U1, back end signal is fed back to the input end of front.Second step low-pass elliptic filter in two two rank Low-pass Elliptic Filters is by U4, U5, U6, R7, R8, R9, R10, R11, R12, R13, R14, C3, C4 forms, R7 connects with C3 and U4 consists of the single order low-pass filtering, the first-order filtering that R10 and C4 series connection and U5 form again, and the end of R9 is connected to the negative input end of U5, the other end is connected to the output terminal of U3, and wherein R7, C3 equate with the value of R10, C4 respectively; The resistance R 12 of U5 two terminations is negative feedback resistors, and effect is exactly stable operating point; R13, R14 and U6 as voltage follower, realize the isolation of two rank elliptic filters and output in the middle of circuit; The end of R11 is connected in the output of U6, and the other end is connected to the negative input end of U4, back end signal is fed back to the input end of front.
The utility model is at a kind of cheaply low-pass filter circuit of current sample link design, then utilize common computation chip also to have the characteristics of two-way current sampling circuit, measure simultaneously fundamental current and total current, thereby can deduct fundamental current by total current and obtain harmonic current, the data such as active energy that also can be by calculating first-harmonic and harmonic wave and percent harmonic distortion have solved the problem that the common electric energy meter that do not use special-purpose harmonic wave computation chip can not measure harmonic wave.
Filtering circuit of the present utility model uses the oval low-pass active filter in 4 rank, extracts fundamental current from total current, thereby realizes the metering of harmonic electric energy and fundamental energy, and then realizes the metering of harmonic electric energy.
The designed filter cutoff frequency of the utility model is 60Hz, and the ripple factor in the passband has good filtering characteristic less than 0.05dB.The design leaves surplus to cutoff frequency, also can not cause very important decay to fundamental signal when the power network current frequency slightly changes; The cut-off characteristics of stopband is good, the 100Hz signal had decay greater than 18dB, have the above decay of 56dB for the larger harmonic signal of content in the practical application (150Hz), for other high-frequency signals decay about 40dB is arranged also, satisfy our needs fully.
By above-mentioned fundamental current signal and total current signal and voltage signal, can calculate harmonic current, fundamental active power and total active power are just subtracted each other and can in the hope of the total active power of harmonic wave, can also be calculated the electrical network parameters such as current distortion rate by both again.
Low-cost harmonic electric energy meter energy accurate-metering harmonic electric energy of the present utility model, its filtering circuit has solved the problem that common electric energy meter computation chip can not measure harmonic electric energy, harmonic wave computation chip compared to special use, highly versatile of the present utility model, electric energy meter does not need to use special-purpose computation chip, just can the accurate-metering harmonic electric energy.The advantage that the utlity model has the low-cost and easy-to maintenance can drop into a large amount of uses very easily.Come the harmonic wave metering in most of electric energy meters that filtering circuit in the utility model can be applied to exist at present.
Description of drawings
The utility model is described in further detail below in conjunction with embodiment.
Fig. 1 is the structured flowchart of harmonic electric energy meter of the present utility model;
Fig. 2 is the structured flowchart of harmonic electric energy meter sampling metering section of the present utility model;
Fig. 3 is the schematic diagram of low-pass filter circuit.
Embodiment
The single-phase harmonic electric energy meter of a kind of low cost, comprise sampling metering section (metering module), storage area (memory module), main control unit MCU, power unit (power module), communications portion (communication module), the display part, sampling metering section front-end sampling obtains current and voltage signals, one road current signal is sent into computation chip after by low-pass filter, another road current signal directly enters computation chip, voltage sampling signal directly enters computation chip, measure by computation chip and to obtain fundamental current signal and total current signal, voltage signal, fundamental energy, total electric energy.
The 4 rank wave filters that described low-pass filter is comprised of two two rank Low-pass Elliptic Filter cascades, each two rank elliptic filter cooperates some resistance capacitances to form by three single operational amplifiers, two operational amplifiers wherein cooperate corresponding resistor electric capacity to realize the function of the oval filtering in two rank, the voltage gain of another single operational amplifier is 1, its input resistance levels off to infinite, output resistance levels off to zero, in the middle of circuit, as voltage follower, realize the isolation of two rank elliptic filters and output.
First two rank elliptic filter in two two rank Low-pass Elliptic Filters is by operational amplifier U1, U2, U3, resistance R 1, R2, R3, R4, R5, R6, capacitor C 1, C2 form, the positive input terminal ground connection of operational amplifier, negative input termination signal, signal are from the input of R1 end, and the other end of R1 and C1 series connection cooperate U1 to form the single order low-pass filtering, R2 and C2 series connection form again first-order filtering with U2, and wherein R1, C1 equate with the value of R2, C2 respectively; The resistance R 4 of U2 two terminations is negative feedback resistors, makes system works stable; R5, R6 and U3 as voltage follower, realize the isolation of two rank elliptic filters and output in the middle of circuit, the end of R3 is connected in the output of U3, and the other end is connected to the negative input end of U1, back end signal is fed back to the input end of front.Second step low-pass elliptic filter in two two rank Low-pass Elliptic Filters is by U4, U5, U6, R7, R8, R9, R10, R11, R12, R13, R14, C3, C4 forms, R7 connects with C3 and U4 consists of the single order low-pass filtering, the first-order filtering that R10 and C4 series connection and U5 form again, and the end of R9 is connected to the negative input end of U5, the other end is connected to the output terminal of U3, and wherein R7, C3 equate with the value of R10, C4 respectively; The resistance R 12 of U5 two terminations is negative feedback resistors, and effect is exactly stable operating point; R13, R14 and U6 as voltage follower, realize the isolation of two rank elliptic filters and output in the middle of circuit; The end of R11 is connected in the output of U6, and the other end is connected to the negative input end of U4, back end signal is fed back to the input end of front.
Metering section adds a filtering circuit, in conjunction with common computation chip, isolate accurately fundamental current, thereby obtain total electric energy and fundamental energy, then deduct fundamental energy with total electric energy and just can obtain our needed harmonic electric energy, this just makes common electric energy meter also can accurately measure harmonic wave, and its structured flowchart as shown in Figure 2.
(1) after being sampled, electric current obtains total current signal I(t);
(2) the total current signal obtains fundamental current signal I through the low-pass filter of the utility model design
Base(t), the decay of the low-pass filter of design about signal frequency 50Hz is very little, and amplitude versus frequency characte is comparatively smooth, and ripple is less than 0.05dB;
(3) according to above-mentioned fundamental current signal, total current signal and voltage signal, calculate the fundamental power of electrical network, fundamental current effective value, total current effective value, and general power.
(4) main control MCU deducts fundamental energy with total electric energy and just can obtain our needed total harmonic electric energy according to the sampling fundamental current signal that obtains of metering section and total current signal, fundamental power, general power and fundamental energy, total electric energy; Total current deducts the fundamental current signal can obtain the harmonic current signal, just can obtain the harmonic current aberration rate with harmonic current divided by fundamental current.
Such as Fig. 2, contain first-harmonic and harmonic signal in the current signal of input, the utility model is sent one tunnel total current signal into computation chip, sends into computation chip after another road current signal is sent into the low pass filter filters out harmonic component.The purpose of low-pass filter is exactly that filtering other harmonic signals except first-harmonic guarantee that less ripple is especially arranged between the 45-55Hz in passband, we adopt the elliptic filter on 4 rank to realize low-pass filtering, its ripple between 45-55Hz is less than 0.05dB, and its cut-off characteristics is good, the 100Hz signal had decay greater than 18dB, has the above decay of 56dB for need filtering main signal (150Hz), for other high-frequency signals decay about 40dB is arranged also, satisfy our needs fully.
The oval active filter on 4 rank has guaranteed that not only wave filter has preferably cut-off characteristics, and the ripple in the passband also is controlled in the less scope, and near the decay the 50Hz only has 0.01714dB.
The transport function of the oval low-pass active filter in 4 rank; When the distance of the limit of transport function and the imaginary axis was distant, its rise time was shorter, and this illustrative system response speed is than very fast, but ripple is larger, the response speed of illustrative system is relatively good, but the dynamic property of system is poor generally, illustrates that its steady-state behaviour is poor; When the distance of the limit of transport function and the imaginary axis was closer, its rise time was long, and this illustrative system response speed is slow, but ripple is less, and the dynamic of system is relatively good generally, and its steady-state behaviour is relatively good; Considering response speed is 4 designed rank Low-pass Elliptic Filters of cut-off characteristics and ripple the utility model, ripple between 45-55Hz is less than 0.05dB, and its cut-off characteristics is good, the 100Hz signal had decay greater than 18dB, have the above decay of 56dB for need filtering main signal (150Hz), for other high-frequency signals decay about 40dB is arranged also.
According to above-mentioned fundamental current signal and total current signal, calculate the fundamental power of electrical network, fundamental current effective value, total current effective value, and general power and total harmonic power.
Claims (3)
1. single-phase harmonic electric energy meter of low cost, comprise sampling metering section, storage area, main control unit MCU, power unit, communications portion, display part, it is characterized in that: the current and voltage signals that sampling metering section front-end sampling obtains, one road current signal is sent into computation chip after by low-pass filter, another road current signal directly enters computation chip, and voltage sampling signal directly enters computation chip.
2. the single-phase harmonic electric energy meter of a kind of low cost according to claim 1, it is characterized in that: the 4 rank wave filters that described low-pass filter is comprised of two two rank Low-pass Elliptic Filter cascades, each two rank elliptic filter cooperates some resistance capacitances to form by three single operational amplifiers, two operational amplifiers wherein cooperate corresponding resistor electric capacity to realize the function of the oval filtering in two rank, the voltage gain of another single operational amplifier is 1, its input resistance levels off to infinite, output resistance levels off to zero, is used as voltage follower in the middle of circuit.
3. the single-phase harmonic electric energy meter of a kind of low cost according to claim 2, it is characterized in that: first the two rank elliptic filter in two two rank Low-pass Elliptic Filters is by operational amplifier U1, U2, U3, resistance R 1, R2, R3, R4, R5, R6, capacitor C 1, C2 form, the positive input terminal ground connection of operational amplifier, negative input termination signal, signal is from the input of R1 end, the other end of R1 and C1 series connection cooperate U1 to form the single order low-pass filtering, R2 and C2 series connection 2, wherein R1, C1 equate with the value of R2, C2 respectively; The resistance R 4 of U2 two terminations is negative feedback resistors; As voltage follower, the end of R3 is connected in the output of U3 in the middle of circuit for R5, R6 and U3, and the other end is connected to the negative input end of U1, back end signal is fed back to the input end of front.Second step low-pass elliptic filter in two two rank Low-pass Elliptic Filters is by U4, U5, U6, R7, R8, R9, R10, R11, R12, R13, R14, C3, C4 forms, R7 connects with C3 and U4 consists of the single order low-pass filtering, the first-order filtering that R10 and C4 series connection and U5 form again, and the end of R9 is connected to the negative input end of U5, the other end is connected to the output terminal of U3, and wherein R7, C3 equate with the value of R10, C4 respectively; The resistance R 12 of U5 two terminations is negative feedback resistors; R13, R14 and U6 are used as voltage follower in the middle of circuit; The end of R11 is connected in the output of U6, and the other end is connected to the negative input end of U4, back end signal is fed back to the input end of front.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220320437 CN202748407U (en) | 2012-07-04 | 2012-07-04 | Low-cost single-phase harmonic electric energy meter |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220320437 CN202748407U (en) | 2012-07-04 | 2012-07-04 | Low-cost single-phase harmonic electric energy meter |
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| Publication Number | Publication Date |
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| CN202748407U true CN202748407U (en) | 2013-02-20 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN 201220320437 Expired - Fee Related CN202748407U (en) | 2012-07-04 | 2012-07-04 | Low-cost single-phase harmonic electric energy meter |
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| CN (1) | CN202748407U (en) |
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- 2012-07-04 CN CN 201220320437 patent/CN202748407U/en not_active Expired - Fee Related
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20130220 Termination date: 20150704 |
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| EXPY | Termination of patent right or utility model |