CN203249967U - Nonlinear load electric energy metering device - Google Patents

Nonlinear load electric energy metering device Download PDF

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Publication number
CN203249967U
CN203249967U CN 201320371854 CN201320371854U CN203249967U CN 203249967 U CN203249967 U CN 203249967U CN 201320371854 CN201320371854 CN 201320371854 CN 201320371854 U CN201320371854 U CN 201320371854U CN 203249967 U CN203249967 U CN 203249967U
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resistance
current
voltage
capacitor
circuit
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黄葆文
魏钰
杨春光
乔立凤
高敬更
赵言涛
王磊
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State Grid Corp of China SGCC
State Grid Gansu Electric Power Co Ltd
Electric Power Research Institute of State Grid Gansu Electric Power Co Ltd
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State Grid Corp of China SGCC
State Grid Gansu Electric Power Co Ltd
Electric Power Research Institute of State Grid Gansu Electric Power Co Ltd
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Abstract

The utility model discloses a nonlinear load electric energy metering device. The nonlinear load electric energy metering device comprises a voltage sensing and regulating unit, a voltage RC filtering circuit, a current sensing and regulating circuit, a current RC filtering circuit, an ADC analog-digital converter and a data processing and managing unit, wherein voltage signals are transmitted to the ADC analog-digital converter through the voltage sensing and regulating unit and the voltage RC filtering circuit, current signals are transmitted to the ADC analog-digital converter through the current sensing and regulating circuit and the current RC filtering circuit, and the ADC analog-digital converter converts the received voltage signals and the current signals and then transmits the signals to the data processing and managing unit. The nonlinear load electric energy metering device has the advantages that the metered signals are distortionless when transmitted and the work is stable and reliable under the conditions of wide impact load frequency band and large dynamic range.

Description

The nonlinear load electric power meter
Technical field
The utility model relates to the electric power meter field, particularly, relates to a kind of nonlinear load electric power meter.
Background technology
Along with the develop rapidly of Power Electronic Technique, the shared ratio of nonlinear-load increases gradually, and nonlinear problem highlights in electrical network day by day.This type load has obvious impact characteristics, can take the power of quick change in production or operational process from power supply network, and the instantaneous peak value of power may be several times even the decades of times of its mean value, and unitedly calling this type load is impact load.Impact load user's electric energy metrical does not adopt special means at present, still uses ordinary electric meter, does like this electric energy that is difficult to reflect the impact load actual consumption, and the pollution of Load on Electric Power Grid also lacks monitoring and estimates.
Present electric power meter is mostly based on the sinusoidal Power Theory of tradition, and take linear load as main, in the distortion of line waveform and the less situation that fluctuates, traditional electric power meter can be realized accurate-metering at network load.
Also can use harmonic electric energy meter, it can measure respectively the energy consumption of each time (such as 0 ~ 63 time) harmonic wave and energy flow to, but harmonic electric energy meter also has limitation, harmonic meter is more effective for the stable state frequency analysis, and reflect when moving for impact load dynamically, transient state process lacks effective detection means.
The utility model content
The purpose of this utility model is, for the problems referred to above, proposes a kind of nonlinear load electric power meter, realizing under the large condition of impact load bandwidth, dynamic range, and the advantage of the reliability of the undistorted and work of metering signal transmission.
For achieving the above object, the technical solution adopted in the utility model is:
A kind of nonlinear load electric power meter, comprise voltage sensor and conditioning unit, voltage RC filtering circuit, current sense and modulate circuit, electric current RC filtering circuit, ADC analog to digital converter and data processing and administrative unit, voltage signal is transferred to the ADC analog to digital converter through voltage sensor and conditioning unit and voltage RC filtering circuit, current signal is transferred to the ADC analog to digital converter through current sense and modulate circuit and electric current RC filtering circuit, and described ADC analog to digital converter is transferred to data after with the voltage signal that receives and current signal conversion and processes and administrative unit.
Further, described data are processed and administrative unit employing DSP.
Further, described ADC analog to digital converter adopts the wide-range circuit of the high-precision adc of stepless level and smooth amplification and 24bit.
Further, the current sense in described current sense and the modulate circuit adopts zero magnetic flux current sensor.
Further, described zero magnetic flux current sensor comprises main iron core, auxiliary iron core, secondary coil and ancillary coil, and described secondary coil is wound on main iron core and the auxiliary iron core simultaneously, and described ancillary coil is wound on the auxiliary iron core.
Further, described voltage RC filtering circuit comprises protection magnet ring L1, protection magnet ring L2, voltage dependent resistor (VDR) Rv, power filtering capacitor C, resistance R, resistance r, resistance And electric capacity
Figure DEST_PATH_IMAGE004
, described protection magnet ring L1, protection magnet ring L2, resistance R, resistance
Figure DEST_PATH_IMAGE002A
And electric capacity
Figure DEST_PATH_IMAGE004A
Be cascaded successively, described voltage dependent resistor (VDR) Rv and power filtering capacitor C one end are connected electrically on the node of protecting between magnet ring L1 and protection magnet ring L2, and its other end is connected electrically in electric capacity
Figure DEST_PATH_IMAGE004AA
On, described resistance r one end is connected electrically in resistance R and resistance
Figure DEST_PATH_IMAGE002AA
Between node on, its other end is connected electrically in electric capacity
Figure DEST_PATH_IMAGE004AAA
On, described resistance R and resistance r consist of bleeder circuit jointly, described resistance
Figure DEST_PATH_IMAGE002AAA
And electric capacity In the RC filtering circuit, play the anti-aliasing filter effect.
Further, described electric current RC filtering circuit comprises zero magnetic flux current sensor L, sample resistance , resistance
Figure DEST_PATH_IMAGE009
And electric capacity
Figure DEST_PATH_IMAGE011
, described resistance
Figure DEST_PATH_IMAGE009A
And electric capacity Be connected on the side winding of zero magnetic flux current sensor L described sample resistance And resistance
Figure DEST_PATH_IMAGE009AA
, electric capacity
Figure DEST_PATH_IMAGE011AA
Parallel connection, resistance
Figure DEST_PATH_IMAGE009AAA
And electric capacity
Figure DEST_PATH_IMAGE011AAA
In electric current RC filtering circuit, play the anti-aliasing filter effect.
Further, described resistance =resistance
Figure DEST_PATH_IMAGE009AAAA
=100 Ω, described electric capacity
Figure DEST_PATH_IMAGE004AAAAA
=electric capacity
Figure DEST_PATH_IMAGE011AAAA
=1000pF.
Further, described electric capacity =100pF.
The technical solution of the utility model has following beneficial effect:
The technical solution of the utility model, after voltage signal and circuit signal are carried out digital-to-analog conversion, after data processing and administrative unit processing, nonlinear-load is prepared metering, realized under the large condition of impact load bandwidth, dynamic range, metering signal transmits the purpose of the reliability of undistorted and work, wherein adopts zero flux current sensing, the wide-range circuit design of high-precision adc, and by high-speed dsp, improve the accuracy of harmonic wave metering.Restriction to resistance and electric capacity in voltage RC filtering circuit and the electric current RC filtering circuit has reduced the displacement error between voltage and circuit, so that continuous data is more accurate.
Below by drawings and Examples, the technical solution of the utility model is described in further detail.
Description of drawings
Fig. 1 is the described nonlinear load electric power meter of the utility model embodiment theory diagram;
Fig. 2 is the described zero magnetic flux current sensor electrical schematic diagram of the utility model embodiment;
Fig. 3 is the electronic circuitry of the described voltage RC of the utility model embodiment filtering circuit;
Fig. 4 is the electronic circuitry of the described electric current RC of the utility model embodiment filtering circuit;
Fig. 5 a to Fig. 5 d is the described voltage RC of the utility model embodiment filtering circuit phase-frequency characteristic figure;
Fig. 6 a is the oscillogram that contains the original signal of jump signal;
Fig. 6 b is that the original signal shown in Fig. 6 a is by incorrect amplifying signal oscillogram;
Oscillogram after the smoothed amplification of original signal shown in Fig. 7 Fig. 6 a;
Fig. 8 is current amplitude modulation waveform figure;
Fig. 9 is short-time current amplitude impulsive model figure;
Figure 10 is the transient Model current waveform figure.
Embodiment
Below in conjunction with accompanying drawing preferred embodiment of the present utility model is described, should be appreciated that preferred embodiment described herein only is used for description and interpretation the utility model, and be not used in restriction the utility model.
As shown in Figure 1, a kind of nonlinear load electric power meter, comprise voltage sensor and conditioning unit, voltage RC filtering circuit, current sense and modulate circuit, electric current RC filtering circuit, ADC analog to digital converter and data are processed and administrative unit, voltage signal is transferred to the ADC analog to digital converter through voltage sensor and conditioning unit and voltage RC filtering circuit, current signal is transferred to the ADC analog to digital converter through current sense and modulate circuit and electric current RC filtering circuit, and the ADC analog to digital converter is transferred to data after with the voltage signal that receives and current signal conversion and processes and administrative unit.
Wherein, data are processed and administrative unit employing DSP.The ADC analog to digital converter adopts the wide-range circuit of the high-precision adc of stepless level and smooth amplification and 24bit.Current sense in current sense and the modulate circuit adopts zero magnetic flux current sensor.Zero magnetic flux current sensor comprises main iron core, auxiliary iron core, secondary coil and ancillary coil as shown in Figure 2, and described secondary coil is wound on main iron core and the auxiliary iron core simultaneously, and described ancillary coil is wound on the auxiliary iron core.
Voltage RC filtering circuit comprises protection magnet ring L1, protection magnet ring L2, voltage dependent resistor (VDR) Rv, power filtering capacitor C, resistance R, resistance r, resistance as shown in Figure 3
Figure DEST_PATH_IMAGE002AAAAA
And electric capacity
Figure DEST_PATH_IMAGE004AAAAAAA
, described protection magnet ring L1, protection magnet ring L2, resistance R, resistance
Figure DEST_PATH_IMAGE002AAAAAA
And electric capacity
Figure DEST_PATH_IMAGE004AAAAAAAA
Be cascaded successively, described voltage dependent resistor (VDR) Rv and power filtering capacitor C one end are connected electrically on the node of protecting between magnet ring L1 and protection magnet ring L2, and its other end is connected electrically in electric capacity On, described resistance r one end is connected electrically in resistance R and resistance
Figure DEST_PATH_IMAGE002AAAAAAA
Between node on, its other end is connected electrically in electric capacity
Figure DEST_PATH_IMAGE004AAAAAAAAAA
On, described resistance R and resistance r consist of bleeder circuit jointly, described resistance
Figure DEST_PATH_IMAGE002AAAAAAAA
And electric capacity
Figure DEST_PATH_IMAGE004AAAAAAAAAAA
In the RC filtering circuit, play the anti-aliasing filter effect.
Electric current RC filtering circuit comprises zero magnetic flux current sensor L, sample resistance as shown in Figure 4
Figure DEST_PATH_IMAGE007AA
, resistance And electric capacity
Figure DEST_PATH_IMAGE011AAAAA
, described resistance
Figure DEST_PATH_IMAGE009AAAAAA
And electric capacity
Figure DEST_PATH_IMAGE011AAAAAA
Be connected on the side winding of zero magnetic flux current sensor L described sample resistance
Figure DEST_PATH_IMAGE007AAA
And resistance
Figure DEST_PATH_IMAGE009AAAAAAA
, electric capacity
Figure DEST_PATH_IMAGE011AAAAAAA
Parallel connection, resistance
Figure DEST_PATH_IMAGE009AAAAAAAA
And electric capacity
Figure DEST_PATH_IMAGE011AAAAAAAA
In electric current RC filtering circuit, play the anti-aliasing filter effect.
Resistance =resistance
Figure DEST_PATH_IMAGE009AAAAAAAAA
=100 Ω, described electric capacity
Figure DEST_PATH_IMAGE004AAAAAAAAAAAA
=electric capacity
Figure DEST_PATH_IMAGE011AAAAAAAAA
=1000pF.
Electric capacity
Figure DEST_PATH_IMAGE004AAAAAAAAAAAAA
During=100pF, additional phase error is less.
The ADC analog to digital converter is used for simulating small voltage, current signal is converted to digital signal; Data are processed and are used for accepting above-mentioned digitized input voltage and input current signal with administrative unit and calculate voltage, electric current, harmonic voltage, harmonic current effective value and electric flux equivalence.
Voltage, current signal generally can enter the AD unit through after the conditioning of preposing signal process circuit, are converted to the laggard line correlation computing of digital signal through ADC.Voltage, current signal are through producing different phase shifts behind the different preposing signal process circuits
Figure DEST_PATH_IMAGE015
, , cause entering between the signal of AD unit and the original signal and have additional phase differential, that is:
Figure DEST_PATH_IMAGE019
(1)
In order to ensure metering result's accuracy, usually need to be to additional phase differential
Figure DEST_PATH_IMAGE021
Revise, the most frequently used modification method is the software displacement method, namely obtains first the phase place modified value
Figure DEST_PATH_IMAGE021A
, voltage waveform moved forward as required or after move
Figure DEST_PATH_IMAGE023
Practice confirms that the method can obtain well to calibrate effect under sine condition, if but contain harmonic component in the load waveform, displacement method can produce the linear phase shift effect, namely the integral shift of waveform for
Figure DEST_PATH_IMAGE025
Subharmonic is actually and has occured
Figure DEST_PATH_IMAGE027
Phase shift, and the phase-frequency characteristic of front end circuit and non-linear itself, this phase correction method can produce larger error for the harmonic wave metering.
Utilize the Matlab emulation tool that the signal conditioning circuit of reality is imported, obtain the higher hamonic wave error in dipping that above-mentioned linear phase shift effect causes.Can find out, along with the increase of overtone order, the Harmonic Metering Error that the angular difference correction causes can increase; And initial correction value
Figure DEST_PATH_IMAGE021AA
Larger, the error in dipping that causes with subharmonic is also larger.Therefore, in order to reduce the higher hamonic wave error in dipping as far as possible, make it in an acceptable scope, to reduce by circuit design
Figure DEST_PATH_IMAGE021AAA
One of feasible method, the new technology that phase-matching technique is used in order to realize this target just.
Voltage RC filtering circuit as shown in Figure 3.
Wherein inductance L 1 and inductance L 2 are the protection magnet ring, and resistance R v is voltage dependent resistor (VDR), and capacitor C is power filtering capacitor, and resistance R and resistance r consist of bleeder circuit jointly, resistance
Figure DEST_PATH_IMAGE002AAAAAAAAAA
And electric capacity
Figure DEST_PATH_IMAGE004AAAAAAAAAAAAAA
Play the anti-aliasing filter effect at the RC filtering circuit,
Figure DEST_PATH_IMAGE029
Input impedance for ADC.Circuit is decomposed into as shown in Figure 3 H1, H2, H3 three parts, and then the biography letter of every part is as follows:
Figure DEST_PATH_IMAGE031
(2)
Figure DEST_PATH_IMAGE033
(3)
Figure DEST_PATH_IMAGE035
(4)
With Common Parameters substitution formula (2)-(4) of each element, obtain the phase-frequency characteristic of each several part shown in Fig. 5 a to 5d.
From the above analysis, affect the filtering circuit that is mainly the H3 part of voltage front end circuit phase-frequency characteristic.
Electric current RC filtering circuit generally comprises current sensing unit and anti-aliasing filter unit, as shown in Figure 4.
Wherein resistance R s is current sampling resistor, resistance
Figure DEST_PATH_IMAGE009AAAAAAAAAA
And electric capacity Consist of the RC filtering circuit and play the anti-aliasing filter effect.Circuit is divided into S1, S2 two parts, and then the phase-frequency characteristic of S1 depends on the phase-frequency characteristic of used sensing CT, and the phase-frequency characteristic of S2 and aforementioned H3 circuit are similar.
The key of phase-matching technique is by the Circuit tuning parameter, so that the additional phase error that the preposition unit in voltage, two loops of electric current produces is identical as far as possible, that is:
Figure DEST_PATH_IMAGE037
(4)
Because in a single day current sensing unit has determined the CT model, its phase-shift characterisitc can not be adjusted, the ratio of the secondary and primary current of zero-flux current transformer equals rated transformation ratio, phase phasic difference 180 degree, secondary current can accurately reflect size and the phase place of primary current, thereby obtains high precision current transformer.And the H1 in the voltage front end circuit, H2 circuit are very little on the phase-shift characterisitc impact of integrated circuit, only have by adjusting H3 and S2 circuit parameter, i.e. adjusting resistance
Figure DEST_PATH_IMAGE002AAAAAAAAAAA
, electric capacity
Figure DEST_PATH_IMAGE004AAAAAAAAAAAAAAA
, resistance , electric capacity
Figure DEST_PATH_IMAGE011AAAAAAAAAAA
Come the phase matching requirement of realization formula (4).
When
Figure DEST_PATH_IMAGE002AAAAAAAAAAAA
= =100 Ω,
Figure DEST_PATH_IMAGE004AAAAAAAAAAAAAAAA
=
Figure DEST_PATH_IMAGE011AAAAAAAAAAAA
In the time of=1000pF, the additional phase error of actual measurement voltage, current return is about-0.23 °, and the Circuit tuning parameter makes
Figure DEST_PATH_IMAGE004AAAAAAAAAAAAAAAAA
During=100pF, additional phase error
Figure DEST_PATH_IMAGE021AAAA
Be reduced to-0.04 °, laid good hardware foundation for improving the harmonic wave accuracy of measuring.
The wide-range design is the core of sensing and filtering circuit, in order to tackle the rush of current situation of impact load existence in service.The current specification of design is 1 (25) A (or 0.3 (6) A), the all occasions that to can be used for CT rated secondary current be 1 ~ 5A, even use under the 5A rated current, this design still can be born the rush of current that surpasses 5 times (secondary device safety coefficient [63]).
Zero flux current sensing is as follows:
In order to guarantee the accuracy of measuring in the wide region, the accurate sensing of electric current is the basis.Existing current sense adopts the iron core type CT based on the law of electromagnetic induction mostly, in general metrology applications, this CT can obtain the good linearity, anti-interference and degree of stability, and because with low cost, has obtained the favor of most of ammeter production firm.But as the impact load metrology applications, reach 1%In ~ Imax is the interior accuracy designing requirement of 2500:1 wide region, and common CT is difficult to competent, needs to use advanced person's sensor technology replace common CT.The error of CT comes from the existence of exciting curent I0 to a great extent.Since the existence of excitatory magnetic potential, first and second electric current
Figure DEST_PATH_IMAGE039
,
Figure DEST_PATH_IMAGE041
Between no longer follow strict proportionate relationship, the angular difference between the two neither be strict 180 °.Work as electric current
Figure DEST_PATH_IMAGE039A
When larger, exciting curent
Figure DEST_PATH_IMAGE043
Impact can ignore,
Figure DEST_PATH_IMAGE039AA
,
Figure DEST_PATH_IMAGE041A
Between angular difference also less; And work as
Figure DEST_PATH_IMAGE039AAA
Hour,
Figure DEST_PATH_IMAGE043A
Effect remarkable, cause mutual inductor to reduce in the linearity of little electric current section, angular difference increases.
In order to remedy this deficiency of CT on sensing principle, adopted a kind of brand-new current sense technology here, i.e. zero flux current sensing.So-called " zero magnetic flux " is the method by external compensation, the magnetic flux in the iron core dropped to the extremely low zero state that is approximately, thereby make current sensor reach very high precision.The mode that realizes zero magnetic flux mainly contains two kinds, and a kind of is active mode, utilizes external circuit that back electromotive force is provided, and needs complicated circuit could obtain accurately same-phase electromotive force; Another kind is passive mode, the pressure drop that utilizes an auxiliary mutual inductor that is superimposed upon on the main mutual inductor to provide back electromotive force to come compensating impedance to produce, thus do not need the magnetic flux of main mutual inductor to provide electromotive force just can realize zero magnetic flux.Comparatively speaking, passive mode need not the external complex circuit, and it is more convenient to realize.
The principle of passive zero flux formula CT as shown in Figure 2.
Zero magnetic flux CT is by main iron core I, auxiliary iron core II, secondary coil
Figure DEST_PATH_IMAGE045
And ancillary coil
Figure DEST_PATH_IMAGE047
Form.
Figure DEST_PATH_IMAGE045A
Simultaneously coiling on two iron cores, but auxiliary iron core few around
Figure DEST_PATH_IMAGE049
Circle.
The ratio of the secondary and primary current of zero-flux current transformer equals rated transformation ratio, phase phasic difference 180 degree, and secondary current can accurately reflect size and the phase place of primary current, thereby obtains high precision current transformer.
Current range is designed to 1 (25) A, ammeter is meaned the dynamic range of 2500:1.In rated current be
Figure DEST_PATH_IMAGE051
In the situation of=1A, the transducing signal of designed sensing circuit conversion is 25mV; When electric current is reduced to 1%
Figure DEST_PATH_IMAGE051A
During=10mA, corresponding transducing signal only has 250uV, if still adopt common 16-bit ADC and not auxiliary other means this moment, the electric energy metering error that is only caused by sampling can reach-3.6% through simulation analysis.
Process for wide dynamic range signals, two kinds of design proposals are arranged usually.The first is based on cost consideration, the scheme that adopts common 16-bitADC+ range to switch, another kind be direct use high precision wide range 24-bitADC without the range handover scheme.
No matter be that sampling point value is judged, or judge according to the waveform effective value, range switches inevitably to be needed to introduce the FEEDBACK CONTROL link, has the time lag effect.The load that has the frequent changes characteristic for impact load most probably because the feedback sluggishness causes the mistake control of range switching, thereby causes error in dipping.
The original signal that contains mutagenic components shown in Fig. 6 a, the signal in front 3 cycles is less, the 4th cycle produced jump signal, if adopt the effective value judging rules, through the 1st all after dates, controlling unit switches to large gain A range with amplifying circuit, 2nd, the signal in 3,4 cycles all is exaggerated A doubly, the 5th periodic Control link switches to little gain a range because detecting effective value information bigger than normal with amplifying circuit, the 5th periodic signal is exaggerated a doubly, the 6th cycle amplifying circuit is because detecting the effective value A range that again switches to less than normal, and the 6th periodic signal is exaggerated A doubly.Be realized that from this process, because the existence of jump signal, the signal that range switched the 4th, 5 cycles has carried out inappropriate amplification, make large-signal excessive, surpass the ADC sample range, small-signal is too small, depart from the optimum sampling scope of ADC, finally can cause electric energy metering error.
If abandon the range handover mechanism, directly adopt the 24-bit high-precision adc, sampling precision and dynamic range all significantly improve, through simulation analysis, 1%
Figure DEST_PATH_IMAGE051AA
The electric energy metering error that causes because of sampling of current point is reduced to-0.015%, is applicable to the pin-point accuracy metering occasion of 0.2S or 0.5S.Put the suitable gain amplifier B of selection before this, realize the level and smooth amplification of gamut, as shown in Figure 7.The use of Technique of Smoothing Amplification so that metering module can accurately catch the shorter transient impact of quick variation, particularly duration of load waveform, has the range switch mode advantage that is beyond one's reach.
For sampled signal, adopt common 16 ADC, the frequency response curve decay is very fast, be that the higher hamonic wave decay is large, when containing the higher hamonic wave of high containing ratio in the signal, cause the signal effective value that calculates to reduce, active power reduces, namely owing to the impact of harmonic wave, reduced the accuracy of measuring of signal active power.And 24 ADC that the utility model (utility model) adopts have the broadband response, and are very little with interior decay at 63 subharmonic, very little on the accuracy of measuring impact of active power, improved the accuracy of measuring under the harmonic effects.
Impact load power changes often very violent, the power flow direction also can often change, if the time interval that forward and reverse meritorious energy is judged is obtained long, then within the period that the power flow direction changes, can cause the problem that positive negative energy is cancelled out each other, thereby have influence on the metering result of forward and reverse energy.The common multifunctional three-phase meter aligns the judgement time of backward energy and generally gets 1s, and the impact load electric energy table is 200ms(even a cycle 20ms with the judgement time shorten of forward and reverse energy), differentiation to the power flow direction is stricter, even guaranteed the occasion in power flow direction frequent variations, also higher precision can be arranged.
Existing current sense adopts the iron core type CT based on the law of electromagnetic induction mostly, and the error of CT comes from the existence of exciting curent I0 to a great extent, and the range of linearity is not wide.Zero magnetic flux CT, the pressure drop that utilizes an auxiliary mutual inductor that is superimposed upon on the main mutual inductor to provide back electromotive force to come compensating impedance to produce, thus do not need the magnetic flux of main mutual inductor to provide electromotive force just can realize zero magnetic flux.Thereby zero linearity and the angular difference characteristic of magnetic flux CT in wide region all is better than common single iron core CT, more is applicable to the electric energy metrical occasion of impact load.
Current range is designed to 1 (25) A, ammeter is meaned the dynamic range of 2500:1.In rated current be In the situation of=1A, the transducing signal of designed sensing circuit conversion is 25mV; When electric current is reduced to 1%
Figure DEST_PATH_IMAGE051AAAA
During=10mA, corresponding transducing signal only has 250uV, if still adopt common 16-bit ADC and not auxiliary other means this moment, the electric energy metering error that is only caused by sampling can reach-3.6% through simulation analysis.
Process for wide dynamic range signals, two kinds of design proposals are arranged usually.The first is based on cost consideration, the scheme that adopts common 16-bitADC+ range to switch, another kind be direct use high precision wide range 24-bitADC without the range handover scheme.
No matter be that sampling point value is judged, or judge according to the waveform effective value, range switches inevitably to be needed to introduce the FEEDBACK CONTROL link, has the time lag effect.The load that has the frequent changes characteristic for impact load most probably because the feedback sluggishness causes the mistake control of range switching, thereby causes error in dipping.
The original signal that contains mutagenic components shown in Fig. 6 a, the signal in front 3 cycles is less, the 4th cycle produced jump signal, if adopt the effective value judging rules, through the 1st all after dates, controlling unit switches to large gain A range with amplifying circuit, 2nd, the signal in 3,4 cycles all is exaggerated A doubly, the 5th periodic Control link switches to little gain a range because detecting effective value information bigger than normal with amplifying circuit, the 5th periodic signal is exaggerated a doubly, the 6th cycle amplifying circuit is because detecting the effective value A range that again switches to less than normal, and the 6th periodic signal is exaggerated A doubly.Be realized that from this process, because the existence of jump signal, the signal that range switched the 4th, 5 cycles has carried out inappropriate amplification, make large-signal excessive, surpass the ADC sample range, small-signal is too small, depart from the optimum sampling scope of ADC, finally can cause electric energy metering error.
If abandon the range handover mechanism, directly adopt the 24-bit high-precision adc, sampling precision and dynamic range all significantly improve, through simulation analysis, 1%
Figure DEST_PATH_IMAGE051AAAAA
The electric energy metering error that causes because of sampling of current point is reduced to-0.015%, is applicable to the pin-point accuracy metering occasion of 0.2S or 0.5S.Put the suitable gain amplifier B of selection before this, realize the level and smooth amplification of gamut, as shown in Figure 7.The use of Technique of Smoothing Amplification so that metering module can accurately catch the shorter transient impact of quick variation, particularly duration of load waveform, has the range switch mode advantage that is beyond one's reach.
In general metrology applications, this CT can obtain the good linearity, anti-interference and degree of stability, and because with low cost, has obtained the favor of most of ammeter production firm.But as the impact load metrology applications, reach 1%In ~ Imax is the interior accuracy designing requirement of 2500:1 wide region, and common CT is difficult to competent, needs to use advanced person's sensor technology replace common CT.
Designed the wide-range circuit design based on zero flux current sensing, stepless level and smooth amplification and 24-bit high-precision adc on the hardware; By high-speed dsp, realized meritorious algorithm that rapid tidal current is differentiated and based on the idle algorithm of instantaneous reactive power.In order to improve the accuracy of harmonic wave metering, phase-matching technique and wide frequency ranges analog to digital conversion on a kind of hardware have been proposed, cooperate real-time FFT algorithm, accurate synchronized sampling linear interpolation algorithm and non-linear amplitude compensation algorithm on the software, greatly improved the accuracy of harmonic wave metering.
Hardware circuit is matched with software algorithm, with the amplitude that adapts to load impact, nonlinear characteristic, and the quick transient change of responding power realizes the functions such as real-time online Detecting Power Harmonics, harmonic energy metering.
In view of nonlinear problem is more outstanding in impact load, so the performance of test chart meter under nonlinear condition is also extremely important.Having made up take 6100A standard harmonic source at this is basic harmonic performance test platform, the contrastive test that the impact load electric energy table developed and the representational electric energy meter of a few money have been carried out harmonic performance, voltage harmonic content: 20%, current harmonic content: 20%, harmonic wave adds one by one.
In addition, the table meter has been finished the harmonic wave calibration test in China metering institute, obtained the harmonic wave Calibration Report, the result of Calibration Report shows, designed impact load electric energy table is in 2-50 wide frequency ranges, change Harmonic Metering Error in the 47.5-52.5 scope in fundamental frequency, maximum is no more than 1%, and performance is better than the level of like product.
Set up three class dynamic models, simulated respectively the continuous variation of load current waveforms amplitude, impact and the transient state process of short-time current amplitude.
The expression formula of current amplitude modulation is:
Figure DEST_PATH_IMAGE053
(4.1)
Short-time current amplitude impulsive model waveform as shown in Figure 9.
Current continuity occurs, and the repetition period is the primitive period
Figure DEST_PATH_IMAGE055
Doubly, per cycle produces one-shot, and dash current is maximum current, and non-dash current is rated current.
Figure DEST_PATH_IMAGE055A
Be rush of current multiple, i.e. maximum current
Figure DEST_PATH_IMAGE057
With rated current Between multiple.
The current temporary state current model is:
(4.2)
Wherein:
Figure DEST_PATH_IMAGE051AAAAAAA
Be specified reference electric current;
Figure DEST_PATH_IMAGE063
Be angular frequency,
Figure DEST_PATH_IMAGE065
,
Figure DEST_PATH_IMAGE067
Be fundamental frequency
Figure DEST_PATH_IMAGE069
Be the attenuation coefficient of gradual DC component in the transient current, numerical value is determined by following formula:
Figure DEST_PATH_IMAGE071
(4.3)
Figure DEST_PATH_IMAGE055AA
Be the rush of current multiple of impact load table,
Figure DEST_PATH_IMAGE074
Be the primitive period.
During test, the above-mentioned model of electric current foundation, with
Figure DEST_PATH_IMAGE076
For the cycle repeats, be illustrated in fig. 10 shown below.
The mode input set up in tested table meter, is obtained contrast test result such as table one,
Table one: the dynamic property contrast test of various tables is contrast table as a result:
Figure DEST_PATH_IMAGE078
The table meter that participates in contrast test is 0.2S level table meter, and the test error under Stable State of Sine is no more than relatively ± and 0.1%.Under front two kinds of models, the difference of impact load table and two import table is very little, can ignore; Difference under the transient current model is slightly large, reaches-0.3% ~-0.6%.Under three kinds of models, differing greatly of the metering result of impact load table and other two domestic table has 0.2% at least, and maximum difference reaches 36%, as seen dynamic performance testing has reflected some table meters concealed performance difference under steady state conditions, has certain reference value.
It should be noted that at last: the above only is preferred embodiment of the present utility model, be not limited to the utility model, although with reference to previous embodiment the utility model is had been described in detail, for a person skilled in the art, it still can be made amendment to the technical scheme that aforementioned each embodiment puts down in writing, and perhaps part technical characterictic wherein is equal to replacement.All within spirit of the present utility model and principle, any modification of doing, be equal to replacement, improvement etc., all should be included within the protection domain of the present utility model.

Claims (8)

1. nonlinear load electric power meter, comprise voltage sensor and conditioning unit, voltage RC filtering circuit, current sense and modulate circuit, electric current RC filtering circuit, ADC analog to digital converter and data are processed and administrative unit, voltage signal is transferred to the ADC analog to digital converter through voltage sensor and conditioning unit and voltage RC filtering circuit, current signal is transferred to the ADC analog to digital converter through current sense and modulate circuit and electric current RC filtering circuit, described ADC analog to digital converter is transferred to data after with the voltage signal that receives and current signal conversion and processes and administrative unit, it is characterized in that, described data are processed and administrative unit adopts DSP.
2. nonlinear load electric power meter according to claim 1 is characterized in that, described ADC analog to digital converter adopts the wide-range circuit of the high-precision adc of stepless level and smooth amplification and 24bit.
3. nonlinear load electric power meter according to claim 1 is characterized in that, the current sense in described current sense and the modulate circuit adopts zero magnetic flux current sensor.
4. nonlinear load electric power meter according to claim 3, it is characterized in that, described zero magnetic flux current sensor, comprise main iron core, auxiliary iron core, secondary coil and ancillary coil, described secondary coil is wound on main iron core and the auxiliary iron core simultaneously, and described ancillary coil is wound on the auxiliary iron core.
5. according to claim 1 to 4 arbitrary described nonlinear load electric power meters, it is characterized in that, described voltage RC filtering circuit comprises protection magnet ring L1, protection magnet ring L2, voltage dependent resistor (VDR) Rv, power filtering capacitor C, resistance R, resistance r, resistance R 0uAnd capacitor C 0u, described protection magnet ring L1, protection magnet ring L2, resistance R, resistance R 0uAnd capacitor C 0uBe cascaded successively, described voltage dependent resistor (VDR) Rv and power filtering capacitor C one end are connected electrically on the node of protecting between magnet ring L1 and protection magnet ring L2, and its other end is connected electrically in capacitor C 0uOn, described resistance r one end is connected electrically in resistance R and resistance R 0uBetween node on, its other end is connected electrically in capacitor C 0uOn, described resistance R and resistance r consist of bleeder circuit jointly.
6. nonlinear load electric power meter according to claim 5 is characterized in that, described electric current RC filtering circuit comprises zero magnetic flux current sensor L, sample resistance R s, resistance R 0iAnd capacitor C 0i, described resistance R 0iAnd capacitor C 0iBe connected on the side winding of zero magnetic flux current sensor L described sample resistance R sAnd resistance R 0i, capacitor C 0iIn parallel.
7. nonlinear load electric power meter according to claim 6 is characterized in that, described resistance R 0u=resistance R 0i=100 Ω, described capacitor C 0u=capacitor C 0i=1000pF.
8. nonlinear load electric power meter according to claim 6 is characterized in that, described capacitor C 0u=100pF.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103344826A (en) * 2013-06-26 2013-10-09 国家电网公司 Nonlinear load electric energy metering device
CN109085425A (en) * 2018-07-20 2018-12-25 国网湖南省电力有限公司 A kind of impact load calculation method
CN111896907A (en) * 2020-08-06 2020-11-06 云南电网有限责任公司电力科学研究院 Current rapid amplification system and method based on power amplifier
CN113533846A (en) * 2021-07-13 2021-10-22 国网江苏省电力有限公司营销服务中心 High-speed synchronous acquisition and calculation method and device for electrical load data

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103344826A (en) * 2013-06-26 2013-10-09 国家电网公司 Nonlinear load electric energy metering device
CN109085425A (en) * 2018-07-20 2018-12-25 国网湖南省电力有限公司 A kind of impact load calculation method
CN109085425B (en) * 2018-07-20 2020-10-20 国网湖南省电力有限公司 Impact load calculation method
CN111896907A (en) * 2020-08-06 2020-11-06 云南电网有限责任公司电力科学研究院 Current rapid amplification system and method based on power amplifier
CN113533846A (en) * 2021-07-13 2021-10-22 国网江苏省电力有限公司营销服务中心 High-speed synchronous acquisition and calculation method and device for electrical load data

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