CN104375003A - Method for lifting sampling points in zero voltage reduction device - Google Patents

Abstract

The invention relates to the technical field of power metering, in particular to a method for lifting sampling points in a zero voltage reduction device. It is judged which position of a sine wave a current sampling point is located at and the largest variation of the position according to the current sampling point and the variation of the current sampling point relative to a previous sampling point, and the found largest variation serves as limiting amplitude to reduce the distortion degree of a wave shape when a harmonic wave exists is reduced. The method mainly comprises the following steps: firstly establishing a dynamic data receiving table at the data receiving end; then waiting to receive data, judging phases after receiving the data and sending signals into the data receiving table; finally, selecting 220 sampling points in one sampling period, and calculating the largest variations of 219 segments according to a theoretical value. A 'variation limiting' method is adopted in the method for lifting the sampling point in the zero voltage reduction device, harmonic waves can be inhibited effectively, and the distortion degree of the wave shape caused by existence of the harmonic waves is reduced.

Description

The method of sampled point is promoted in zero pressure drop equipment

Technical field

The present invention relates to electric-power metering technical field, particularly relating to one can effective harmonic inhabitation, can solve the method promoting sampled point in the zero pressure drop equipment of the waveform serious distortion problem brought because of harmonic wave.

Background technology

Regulation according to " electric power meter technical management code " DL/T448-2000: " Voltage Transformer Secondary Circuit Voltage Drop, to I class charging measuring apparatus, should be not more than 0.25% of rated secondary voltage; Other measuring apparatus, should be not more than 0.5% of rated secondary voltage ".

The error of electric power meter, the error in dipping caused by the resultant error of voltage transformer (VT) (PT) summation current transformer (CT), the error of electric energy meter, PT secondary circuit voltage drop formed.Wherein, the error in dipping that PT secondary circuit voltage drop (abbreviation secondary voltage drop) causes is maximum often, so eliminate or reduce secondary voltage drop, ensures that the precision of measuring apparatus is the problem of not allowing to despise.In electric system, can there are some errors in electric energy metrical.According to the result of many places electrical network generaI investigation test, the error in dipping that the pressure drop of voltage transformer (VT) (PT) secondary wiring causes is maximum.Because PT secondary singal needs longer cable transmission to receive electric energy meter to pulpit, long range propagation can produce very large pressure drop, also just creates very large error.This error is negative error, can cause very large economic loss for Utilities Electric Co..

Existing several solution and Problems existing are respectively:

1, the impedance of PT secondary circuit is reduced.Shortening loop length and increasing sectional area of wire is all feasible solution, but practical operation is difficult.

2, PT secondary loop current is reduced.Use independent measure winding, independent transfer wire, can loop current be reduced, but the quantity of cable will increase much thereupon.

3, electronic installation compensates.Need according to field condition adjustment offset.But its poor reliability, does not have confidence level.

Use digital form (high-precision optical fiber digital switching system) signal transmission instead and ensure that Signal transmissions does not lose.Digital transmission needs original simulating signal to carry out digitizing, and the reliability of digitized accuracy and equipment is directly related with the error of the signal after recovery.At data receiver, as a rule, the method using software to promote sampled point is---use interpolation, but if adopt interpolation method in zero pressure drop system, the process of phase place will be very complicated, so, usually adopt the method for extrapolation to improve sampled point.Adopt this method of extrapolation, time in three-phase electricity containing harmonic wave, the waveform modification that recovers can be made serious.

Summary of the invention

The object of the invention is to solve the operating difficulties existing for method promoting sampled point in existing zero pressure drop equipment, process is complicated, poor reliability, the waveform recovered because of containing harmonic wave, be out of shape seriously, the problem that distortion level is high, and a kind of method promoting sampled point in zero pressure drop equipment is provided.

The technical solution adopted in the present invention is:

The method of sampled point is promoted in a kind of zero pressure drop equipment, according to current sampling point and the variable quantity relative to previous sampled point, judge current be in sinusoidal wave where, and the maximum variable quantity of this position, amplitude limit is done with the maximum variable quantity found, reduce the distortion level containing waveform during harmonic wave, specifically comprise the steps:

Step 1), data receiver set up dynamic data receive form, regulation table content with the corresponding relation of A phase, B phase, C phase in three-phase electricity is,

A→DAC1

B→DAC2

C→DAC3；

Step 2), wait-receiving mode data, after receiving data, judgement is A phase, B phase or C phase, and A phase, B phase and C phase signals are sent into DAC1, DAC2 and DAC3 respectively;

Step 3), within a sampling period, choose 220 sampled points, calculate the maximum variable quantity of 219 segmentations according to theoretical value:

I). calculate interpolation according to extrapolation algorithm:

A: x _i x _i+ x _i+ x _i+1...... ( =x _i-x _i-1)

B: y _i y _i+ y _i+ y _i+1...... ( =y _i-y _i-1)

C: z _i z _i+ z _i+ z _i+1...... ( =z _i-z _i-1)；

Ii). according to x _i-1and x _ivalue, at x _iinsert two numerical value below, make sampled point quantity be increased to 220*3=660:

I-th moment: x _iz _i-1+ y _i-2+

I-th+1 moment: y _i+1x _i+ z _i-1+

I-th+2 moment: z _i+2y _i+1+ x _i+ ;

Iii). according to the difference data calculated above, obtain any time reception data x _i, y _i, z _irestriction variable quantity:

1. search and receive data x _i, y _i, z _isection belonging to sampled value: multilevel iudge belongs to sinusoidal wave epimere lower semisection also, judgement is increasing trend or decline trend, specifically determines in which segmentation;

By the variable quantity of the variable quantity of affiliated segmentation and actual sample value ( =x _i-x _i-1, =y _i-y _i-1, =z _i-z _i-1) compare, choose in both less, as the restriction variable quantity of each segmentation, restriction interpolation scope, harmonic inhabitation.

Beneficial effect of the present invention is: the method that have employed " restriction variable quantity ", effective harmonic inhabitation, reduce because of containing harmonic wave cause the distortion of waveform.

Accompanying drawing explanation

Fig. 1 is the general flow chart promoting the embodiment of the method for sampled point in zero pressure drop equipment provided by the invention;

Fig. 2 is the control flow chart promoting Abort Timer in the embodiment of the method for sampled point in zero pressure drop equipment provided by the invention.

Embodiment

Core of the present invention is to provide a kind of method promoting sampled point in zero pressure drop equipment.

For making the object, technical solutions and advantages of the present invention clearly, below in conjunction with Figure of description, the method promoting sampled point in zero pressure drop equipment provided by the present invention is further described.

Harmonic wave shows as in waveform to occur larger sawtooth, and the variable quantity between segmentation is larger, and sawtooth is larger, and harmonic wave is more serious, therefore will reach the object of harmonic inhabitation, just need constantly revising variable quantity.The present invention adopts this method of extrapolation for solving, time in three-phase electricity containing harmonic wave, the problem that the waveform modification that recovers is serious can be made, and a kind of method promoting sampled point in zero pressure drop equipment is provided: according to current sampling point and the variable quantity relative to previous sampled point, judge current be in sinusoidal wave where, and the maximum variable quantity of this position, do amplitude limit with the maximum variable quantity found, reduce the distortion level containing waveform during harmonic wave.As shown in Figure 1, 2, it specifically comprises the steps:

Step 1), data receiver set up dynamic data receive form, regulation table content with the corresponding relation of A phase, B phase, C phase in three-phase electricity is,

A→DAC1

B→DAC2

C→DAC3；

Step 2), wait-receiving mode data, the interruption of the adc data that wait-receiving mode arrives, is specially, the stand-by period of setting timer is 1016ms, after receiving data, judgement is A phase, B phase or C phase, and A phase, B phase and C phase signals are sent into DAC1, DAC2 and DAC3 respectively;

Step 3), within a sampling period, choose 220 sampled points, calculate the maximum variable quantity of 219 segmentations according to theoretical value:

I). calculate interpolation according to extrapolation algorithm:

A: x _i x _i+ x _i+ x _i+1...... ( =x _i-x _i-1)

B: y _i y _i+ y _i+ y _i+1...... ( =y _i-y _i-1)

C: z _i z _i+ z _i+ z _i+1...... ( =z _i-z _i-1)；

Ii). according to x _i-1and x _ivalue, at x _iinsert two numerical value below, make sampled point quantity be increased to 220*3=660:

I-th moment: x _iz _i-1+ y _i-2+

I-th+1 moment: y _i+1x _i+ z _i-1+

I-th+2 moment: z _i+2y _i+1+ x _i+ ;

Iii). according to the difference data calculated above, obtain any time reception data x _i, y _i, z _irestriction variable quantity:

2. search and receive data x _i, y _i, z _isection belonging to sampled value: upgrade sinusoidal wave crest, trough, zero-bit, peak value according to instantaneous crest, trough value, multilevel iudge belongs to sinusoidal wave epimere lower semisection also, and judgement is increasing trend or decline trend, specifically determines in which segmentation;

By the variable quantity of the variable quantity of affiliated segmentation and actual sample value ( =x _i-x _i-1, =y _i-y _i-1, =z _i-z _i-1) compare, choose in both less, as the restriction variable quantity of each segmentation, obtain the maximum variable quantity form of 219 segmentations, restriction interpolation scope, harmonic inhabitation.

The foregoing is only checking embodiment of the present invention, not in order to limit the present invention, all do under the technology of the present invention thought any amendment, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (1)

1. in a zero pressure drop equipment, promote the method for sampled point, it is characterized in that, according to current sampling point and the variable quantity relative to previous sampled point, judge current be in sinusoidal wave where, and the maximum variable quantity of this position, do amplitude limit with the maximum variable quantity found, reduce the distortion level containing waveform during harmonic wave, specifically comprise the steps:

Step 1), data receiver set up dynamic data receive form, regulation table content with the corresponding relation of A phase, B phase, C phase in three-phase electricity is,

A→DAC1

B→DAC2

C→DAC3；

Step 2), wait-receiving mode data, after receiving data, judgement is A phase, B phase or C phase, and A phase, B phase and C phase signals are sent into DAC1, DAC2 and DAC3 respectively;

Step 3), within a sampling period, choose 220 sampled points, calculate the maximum variable quantity of 219 segmentations according to theoretical value:

I). calculate interpolation according to extrapolation algorithm:

A: x _i x _i+ x _i+ x _i+1...... ( =x _i-x _i-1)

B: y _i y _i+ y _i+ y _i+1...... ( =y _i-y _i-1)

C: z _i z _i+ z _i+ z _i+1...... ( =z _i-z _i-1)；

Ii). according to x _i-1and x _ivalue, at x _iinsert two numerical value below, make sampled point quantity be increased to 220*3=660:

I-th moment: x _iz _i-1+ y _i-2+

I-th+1 moment: y _i+1x _i+ z _i-1+

I-th+2 moment: z _i+2y _i+1+ x _i+ ;

Iii). according to the difference data calculated above, obtain any time reception data x _i, y _i, z _irestriction variable quantity:

Search and receive data x _i, y _i, z _isection belonging to sampled value: multilevel iudge belongs to sinusoidal wave epimere lower semisection also, judgement is increasing trend or decline trend, specifically determines in which segmentation;

By the variable quantity of the variable quantity of affiliated segmentation and actual sample value ( =x _i-x _i-1, =y _i-y _i-1, =z _i-z _i-1) compare, choose in both less, as the restriction variable quantity of each segmentation, restriction interpolation scope, harmonic inhabitation.