CN104237650A - Electric arc square shoulder area detection method - Google Patents

Abstract

The invention relates to an electric arc square shoulder area detection method. The electric arc square shoulder area detection method mainly comprises the step of A/D conversion, the step of setting a threshold value, the step of comparing a sampling value with the threshold value, the step of median filtering, the step of continuous median filtering, the step of forward difference and the like. First, the sampling value of a current signal in a line is obtained through an A/D conversion device, then, the sampling value is converted into a series of 0-1 binary sequence through the preset threshold value, median filtering (smoothing) is carried out on the binary sequence till an ideal binary sequence is obtained, the frequency of continuously-appearing 1 in the final ideal binary sequence is worked out, and the position, where 1 first appears, in the binary sequence is marked; meanwhile, by comparing the initial binary sequence and the final ideal binary sequence, the frequency of jumps in a square shoulder area can be judged. The square shoulder area in the current signal can be positioned when an electric arc occurs so that processing and analysis such as Fourier transform can be carried out on the square shoulder area.

Description

A kind of electric arc Ping Jian district detection method

Technical field

The invention belongs to arc-detection technical field, be specifically related to a kind of electric arc Ping Jian district detection method.

Background technology

Due in a period of time before and after alternating current zero passage, arc column starts to turn cold and attenuates, arc gap voltage rise is slow, electric arc can not obtain enough institute's energy requirements from power supply, electric arc is reduced gradually by fired state, electric current in electric arc no longer presses AC sine wave change, but according to other particular law in change, namely line current equals the ratio of arc voltage and arc resistance, simultaneously because arc resistance during arc extinction becomes quite large, become the leading factor of restriction line current, cause the electric current in circuit to be limited in by arc resistance and be approximately zero, the time is stopped during this period of time also referred to as zero of electric current.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, a kind of electric arc Ping Jian district detection method is provided, compared with prior art the invention has the beneficial effects as follows: can realize the location of electric arc Shi Duipingjian district in current signal occurs, thus can process Ping Jian district and analyze, as Fourier transform.

Research and experiment find, when producing electric arc in electricity consumption loop, because electric arc exists a process extinguished and restrike before and after current over-zero, current signal waveform can be caused to occur flat shoulder phenomenon, and have certain probability generation high-frequency impulse in Ping Jian district, illustrate that the analysis (as Ping Jian district reference position, width, transition times etc.) to Ping Jian district is with or without the important step that electric arc occurs in decision circuitry.

For achieving the above object, the technical scheme that a kind of electric arc Ping Jian district detection method adopts is: mainly comprise A/D conversion, setting threshold value, sampled value and threshold value carry out adjudicating, medium filtering, continuous medium filtering, the several step of forward difference.First the current signal in circuit is passed through described A/D reforming unit, obtain its sampled value, then a string 0-1 binary sequence is converted into by setting threshold value described in advance, described medium filtering (smoothing processing) is carried out to binary sequence obtained above, until obtain desirable binary sequence, to calculate in final desirable binary sequence the number of times occurring 1 continuously again, and mark position when it occurs 1 first; Simultaneously by comparing initial binary sequence and final desirable binary sequence, the transition times in Ping Jian district can be judged.

The definition of desirable 0-1 binary sequence Y: sequence only has at most two places there will be between saltus step.Represent with mathematical formulae, $\underset{1}{\overset{N}{\mathrm{\Σ}}}|Y_n-Y_{n-1}|=\left\{\mathrm{1,2}\right\},$ Wherein Y ₀=0.

Accompanying drawing explanation

Fig. 1 is the FB(flow block) of electric arc Ping Jian district detection method

Mathematic sign illustrates: f _sfor sample frequency, I _reffor setting threshold value, I _nfor the sampled value of bias voltage, N is the sampling number in the cycle, n ∈ [1, N], i _nfor current signal sampled value, δ is permissible error, and num is the number of times of appearance 1 in desirable 0-1 binary sequence, and d is flat shoulder sector width, and start is the position for occurring 1 in desirable 0-1 binary sequence first, and s is Ping Jian district reference position, f=[f ₁, f ₂... f _n] be to i _ncarry out the 0-1 binary sequence after threshold value judgement, y=[y ₁, y ₂... y _n] for carry out the 0-1 binary sequence after medium filtering to f, Y=[Y ₁, Y ₂... Y _n] for carry out the desirable 0-1 binary sequence after continuous medium filtering to y, u=[u ₁, u ₂... u _n] be to Y forward difference after sequence, k represents sequence f _ntransition times in Ping Jian district d, Σ represents multinomial summation, and A → B represents and replaces B with A, represent and suddenly change to 1 by 0 or suddenly change to 0 by 1, { } represents set.

Embodiment

Below in conjunction with accompanying drawing, specific embodiment of the invention is described, so that those skilled in the art better understands the present invention.

See Fig. 1, be the FB(flow block) of electric arc Ping Jian district detection method, its concrete implementation step is as follows:

Threshold value I _refcalculating: n=128 in this example.

Threshold value setting should be noted that following some:

1., time due to Sample AC signal, after generally the negative half period of AC signal being carried out positive voltage bias, send A/D to sample again, thus threshold value to choose with the hardware sample circuit of actual line electric current biased relevant.2. consider the waveform in the line current cycle and A/D conversion error, threshold value is chosen also to be needed to do certain permissible error process.3. during generation electric arc, its electric current no longer has periodically, and imperfect at some current cycle waveform, the current waveform in the adjacent periods of front and back differs greatly, so the method by being averaging above-mentioned A/D sampled value can not be adopted to obtain threshold value.4. need to do another road A/D sampling to sample to bias voltage, then the value obtained of sampling is averaged.

By sampled value i _nbe converted into sequence f: if | i _n-I _ref| during < δ, replace i with 1 _n, note 1 → i _n; If | i _n-I _ref| > δ, replaces i with 0 _n, note 0 → i _n.So just obtain a string 0-1 binary sequence, the point that should be noted that: 1. the value of permissible error δ is very crucial, if δ get too large, larger error can be introduced, make the flat shoulder sector width measured be greater than developed width; What the while of 2., δ got is too little, there is certain error, likely can examine and not measure Ping Jian district, or make measured value be less than actual value because hardware circuit and A/D transform.

Medium filtering is carried out to sequence f and obtains y: the moving window having odd point with, the Mesophyticum of each point in the value window of window center point is replaced.If an one-dimensional sequence f ₁, f ₂... f _n.Get length of window (counting) for m (m is odd number), medium filtering is carried out to this one-dimensional sequence, from list entries, in succession extracts m number f out exactly _n-v..., f _n-1, f _n, f _n+1..., f _n+v, wherein f _nfor window center point value, again this m point value is sorted by its numerical values recited, get centered by sequence number and put that number as filtering output, be expressed as y with mathematical formulae _n=Med{f _n-v..., f _n-1, f _n, f _n+1..., f _n+v}

The reason of smoothing processing: we want the sequence obtained to meet the following conditions: do not occur the sequence not occurring 1 in 0 or continuous 0 in 1.But consider in sampling have interference, unavoidably there will be the saltus step of 1 or 0, need the smoothing process of above-mentioned binary sequence, what adopt here is medium filtering.

Select the reason of medium filtering: paired pulses disturbs, and particularly rushes density second and is less than (m is medium filtering length of window), narrow punching interference second apart from each other, medium filtering is effectively.

If sequences y obtained above, when not meeting the condition of desirable binary sequence, proceed last action---medium filtering, until obtain desirable binary sequence Y.

Continuous medium filtering is carried out to sequences y and obtains Y: use y _nsubstitute f _n, be designated as y _n→ f _n.Operating process mathematical formulae is expressed as Y _n=Med{y _n-v..., y _n-1, y _n, y _n+1..., y _n+v}

Sequence of calculation u: a forward difference computing is carried out to ideal sequence Y, u _n=| Y _n-Y _n-1|, as n=1, define the Y in this formula ₀=0.

The calculating of flat shoulder sector width d: wherein num is desirable 0-1 binary sequence Y _nin 1 occur number of times.

The determination of Ping Jian district reference position s: wherein start meets the following conditions, and as n=start, has u _start=1; And as n=start+num+1, there is u _start+num+1=1.Note: second condition must not meet in some cases.

The calculating of transition times k in Ping Jian district: the number of times of 0 is there is in Ji Pingjian district.

Claims (3)

1. an electric arc Ping Jian district detection method, mainly comprise A/D conversion, setting threshold value, sampled value and threshold value carry out adjudicating, medium filtering, continuous medium filtering, the several step of forward difference; Be characterised in that: come to occur with or without electric arc in decision circuitry according to analysis reference position, width, transition times, can realize the location of electric arc Shi Duipingjian district in current signal occurs, thus can process Ping Jian district and analyze.

2. a kind of electric arc Ping Jian district according to claim 1 detection method, it is characterized in that: the technical scheme of employing is: first the current signal in circuit is passed through described A/D reforming unit, obtain its sampled value, then a string 0-1 binary sequence is converted into by setting threshold value described in advance, described medium filtering (smoothing processing) is carried out to binary sequence obtained above, until obtain desirable binary sequence, to calculate in final desirable binary sequence the number of times occurring 1 continuously again, and mark position when it occurs 1 first; Simultaneously by comparing initial binary sequence and final desirable binary sequence, the transition times in Ping Jian district can be judged.

3. a kind of electric arc Ping Jian district according to claim 1 detection method, the scheme concrete steps that it is characterized by employing are as follows:

(1) threshold value I _refcalculating: n=128 in this example;

(2) by sampled value i _nbe converted into sequence f: if | i _n-I _ref| during < δ, replace i with 1 _n, note 1 → i _n; If | i _n-I _ref| > δ, replaces i with 0 _n, note 0 → i _n, so just obtain a string 0-1 binary sequence;

(3) medium filtering is carried out to sequence f and obtain y: the moving window having odd point with, the Mesophyticum of each point in the value window of window center point is replaced.If an one-dimensional sequence f ₁, f ₂... f _n.Get length of window (counting) for m (m is odd number), medium filtering is carried out to this one-dimensional sequence, from list entries, in succession extracts m number f out exactly _n-v..., f _n-1, f _n, f _n+1..., f _n+v, wherein f _nfor window center point value, again this m point value is sorted by its numerical values recited, get centered by sequence number and put that number as filtering output, be expressed as y with mathematical formulae _n=Med{f _n-v..., f _n-1, f _n, f _n+1..., f _n+vif sequences y obtained above, when not meeting the condition of desirable binary sequence, proceed last action---medium filtering, until obtain desirable binary sequence Y;

(4) continuous medium filtering is carried out to sequences y and obtain Y: use y _nsubstitute f _n, be designated as y _n→ f _n.Operating process mathematical formulae is expressed as Y _n=Med{y _n-v..., y _n-1, y _n, y _n+1..., y _n+v;

(5) sequence of calculation u: a forward difference computing is carried out to ideal sequence Y, u _n=| Y _n-Y _n-1|, as n=1, define the Y in this formula ₀=0;

(6) calculating of flat shoulder sector width d: wherein num is desirable 0-1 binary sequence Y _nin 1 occur number of times;

(7) determination of Ping Jian district reference position s: wherein start meets the following conditions, and as n=start, has u _start=1; And as n=start+num+1, there is u _start+num+1=1.Note: second condition must not meet in some cases;

(8) calculating of transition times k in Ping Jian district: the number of times of 0 is there is in Ji Pingjian district.