CN104811135A - Photovoltaic system fault arc detection method under common-mode signal interference condition - Google Patents
Photovoltaic system fault arc detection method under common-mode signal interference condition Download PDFInfo
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Abstract
The invention discloses a photovoltaic system fault arc detection method under the common-mode signal interference condition. The nonzero differential signal output between adjacent photovoltaic clusters through gain calibration, the situation that input signals of a direct-current fault arc detection device are influenced by differential factors except the fault arc events is excluded, detection signals between any adjacent photovoltaic clusters of a photovoltaic system are processed through differential conversion, the fault arc detection is conducted through the direct-current fault arc detection device by means of the differential signals, fault photovoltaic modules are cut off when fault arcs happen, and the photovoltaic system unceasingly runs till the balance gain exceeds the set range. The method solves the problem that when the direct-current fault arc detection module detects the electricity quantity of a normal line, due to the influences of common-mode signals, maloperation is caused. It is avoided that the full system stops running when local fault arcs happen, and the fault arc positioning and protecting capacity of the system under the interference of the common-mode signals is improved.
Description
Technical field
The invention belongs to the electric fault detection technique field of photovoltaic, be specifically related to a kind of common mode signal components exporting with the non-zero differential signal compensated when not breaking down arc event based on balancing gain correction, comprise based on detection signal elimination photovoltaic system detection signal between differential conversion process arbitrary neighborhood two photovoltaic string, and judge photovoltaic system running status based on the current set value of balancing gain, realize photovoltaic system can localized resection fault photovoltaic module with the method for stable Maximum Power Output.
Background technology
Along with the requirement of the exploitation of global non-renewable energy resources intensive style and sustainable development, be that the photovoltaic generating system of primary energy is able to residential quarter in the world and industry and commerce field is extensively promoted and comes into operation with solar energy.But from last century the nineties, various places photovoltaic generating system takes place frequently fire incident, add that photovoltaic generating system at that time is usually distributed under the inflammable external environment of the shortage supervision such as building roof exterior wall, field, wilderness, thus cause a large amount of economic losses even threat to life safety.Found by research, these fire are almost all caused by fault electric arc.Once occur that aging, the damaged or electric loop of line insulation exists to connect situations such as loosening in photovoltaic system, these positions just can produce fault electric arc.There is not the flat shoulder phenomenon produced because of phase change that AC fault electric arc has in it, the continuous high temperature ionized gas developed by it just can discharge heat up to more than 1000 degrees Celsius till photovoltaic system no longer generates electricity, this hot gas and the metal melt of splash is burnt photovoltaic system assembly or lighted inflammable explosive article around by its deposite metal conductor, finally causes region area to have a power failure and large area fire explosion.Therefore, various countries formulate the design of photovoltaic system DC Line Fault electric arc detecting device and testing standard in succession, urge detection failure electric arc and the research and development isolating the DC Line Fault electric arc detecting device producing fault electric arc device in time in order to instruct.
At present, detect for photovoltaic system fault electric arc, although obtain through studying for a long period of time both at home and abroad for detecting and excising the DC Line Fault electric arc detecting device of fault electric arc, common-mode signal phenomenon prevention ability is detected to the fault electric arc in photovoltaic system also very weak.Such as, crosstalk phenomenon in photovoltaic system just can cause the phenomenon that this kind of common-mode signal produces, namely system is once after the electric arc that breaks down, corresponding faulty line just can produce the only characteristic signal of fault electric arc, the existence of this Signal analysis fault electric arc in the usual analyzing and testing signal of DC Line Fault electric arc detecting device.But, partial fault arc characteristic signal can be conducted by circuit in communication process or electromagnetic induction two approach are coupled to all the other regular links to some extent, this common-mode signal interference regular link signal also makes regular link possess the feature of similar fault electric arc while propagating, make DC Line Fault electric arc detecting device that regular link is mistakenly identified as faulty line, cause and be integrated in the photovoltaic module (direct current measurement that Miniature inverter uses single photovoltaic module to export, therefore the DC Line Fault arc protection device being integrated in Miniature inverter still belongs to this type of), be integrated in the photovoltaic string (direct current measurement that group serial type inverter uses single photovoltaic string to export, therefore the DC Line Fault arc protection device being integrated in group serial type inverter still belongs to this type of) the extensive malfunction of DC Line Fault electric arc detecting device.This has just run counter to use and has been integrated in photovoltaic module in a large number and (is integrated in Miniature inverter, afterwards with), the original intention of the DC Line Fault electric arc detecting device of photovoltaic string (be integrated in group serial type inverter, rear with) the still Maximum Power Output increasing the regular link operating time, under the arcing conditions that ensures to break down.(specially concentrated inverter is referred to for being integrated in inverter, the direct current measurement of its process is through the direct current measurement of the whole photovoltaic system output of header box process, compare the above two and have more globality) DC Line Fault electric arc detecting device, as long as there is fault electric arc, whole photovoltaic system just quits work, thus there is not above-mentioned drawback, but the phenomenon that the interference of common-mode signal makes regular link be similar to fault electric arc obviously makes this intrasystem DC Line Fault electric arc detecting device occurrence positions real to fault electric arc be difficult to determine.
Fault electric arc just can produce crosstalk phenomenon after occurring, make normal light hint road all have some identical fault electric arc characteristic signal, also the interference of these common-mode signals makes DC Line Fault electric arc detecting device think its break down electric arc and misoperation by mistake just.
Summary of the invention
The object of the invention is to solve DC Line Fault arc protection device be subject to the impact of common-mode signal when photovoltaic system breaks down electric arc and cause the problem of malfunction, provide the photovoltaic system fault arc detection method under a kind of common-mode signal disturbed condition.
For achieving the above object, present invention employs following technical scheme:
The first step, elimination photovoltaic system fault electric arc detect common-mode signal interference
In photovoltaic system running, to photovoltaic system arbitrary neighborhood two photovoltaic string synchronized sampling, balancing gain and differential conversion process are carried out successively to the output electric quantity signal that sampling obtains;
Second step, the differential signal utilizing differential conversion process to obtain by DC Line Fault electric arc detecting device carry out fault electric arc detection;
3rd step, according to fault electric arc testing result, when not breaking down arc event, correct according to non-zero Difference signal pair balancing gain, balancing gain after correction makes photovoltaic system continuous service when not exceeding setting range, when breaking down electric arc, excise corresponding photovoltaic string internal fault photovoltaic module, then make photovoltaic system continue to run until balancing gain exceeds setting range, the principle correcting balancing gain ensures when not breaking down arc event that the signal inputing to DC Line Fault electric arc detecting device is zero differential signal.
Photovoltaic system fault arc detection method under described common-mode signal disturbed condition specifically comprises the following steps:
1) starting stage is run, according to the initial condition of the output situation determination balancing gain of photovoltaic system adjacent photovoltaic crosstalk amount at photovoltaic system;
2) during photovoltaic system runs, by sample frequency f
1the output electric quantity signal of photovoltaic system arbitrary neighborhood two photovoltaic string is sampled, obtain two-way detection signal, wherein after balancing gain, will carry out differential conversion process with another road detection signal by a road detection signal, whether DC Line Fault electric arc detecting device exceeds setting range N according to the read in detection signal after balancing gain and differential conversion process
0, judge whether the electric quantity signal read in forms non-zero differential signal, if exceed setting range N
0, then judge that in current sample time photovoltaic system, corresponding adjacent two photovoltaic strings output electric quantity signals form non-zero differential signal after balancing gain and differential conversion process, go to step 3); If do not exceed setting range N
0then judge that corresponding adjacent two photovoltaic strings of current sample time photovoltaic system export electric quantity signal and form zero differential signal after balancing gain and differential conversion process, keep the set point of current balancing gain constant, then carry out reading in through the detection signal of balancing gain and differential conversion process next time;
3) DC Line Fault electric arc detecting device is according to read in non-zero differential signal, fault electric arc detection is carried out by characteristic quantity Threshold Analysis, and judge whether current sample time breaks down arc event, if break down arc event, then counting variable N counts, and then goes to step 4); If do not break down arc event, then reset counting variable N, the output electric quantity signal according to corresponding adjacent two photovoltaic strings of current sample time photovoltaic system corrects balancing gain, then goes to step 5);
4) whether failure judgement arc event recurs: if fault electric arc event recurs N
1secondary, then judge to break down in current sample time photovoltaic system electric arc, excision fault photovoltaic module, keep the still normal work of residue photovoltaic system assembly, reset counting variable N, then return step 2); If fault electric arc event does not recur N
1secondary, then keep the set point of current balancing gain constant, then return step 2);
5) judge whether balancing gain exceeds setting range N
2if exceed setting range N
2, then judge that the corresponding adjacent photovoltaic string of current sample time photovoltaic system exports electric quantity signal and has big difference, take safeguard measure and make photovoltaic system quit work, if do not exceed setting range N
2, then judge that the corresponding adjacent photovoltaic string of current sample time photovoltaic system exports electric quantity signal and is more or less the same, photovoltaic system still can reliably normally run, and returns step 2).
Described sample frequency f
1span be 10kHz ~ 50kHz, setting range N
0span for-B ~ B, B is 10
-3~ 10
-15, N
1span be 3 ~ 5.
When using software simulating to eliminate photovoltaic system fault electric arc detection common-mode signal interference, DC Line Fault electric arc detecting device need be set up photovoltaic module and export electric quantity signal input port, and balancing gain corrects and software simulating in differential conversion processing and utilizing DC Line Fault electric arc detecting device; When using hardware implementing to eliminate photovoltaic system fault electric arc detection common-mode signal interference, need detect the balance correction output device that to arrange between electricity device and DC Line Fault electric arc detecting device and correct for balancing gain and the signal processing apparatus for differential conversion process in photovoltaic system, balancing gain corrects and is realized by the communication between balance correction output device and DC Line Fault electric arc detecting device.
When photovoltaic system of sampling exports electricity, should ensure that the output electricity type of sampling from adjacent two photovoltaic strings is consistent, the output electric quantity signal for the adjacent photovoltaic string being inputed to same DC Line Fault electric arc detecting device by described input port should have consistent electricity type.
The method that described elimination photovoltaic system fault electric arc detects common-mode signal interference is to eliminating crosstalk common mode component that photovoltaic system fault electric arc causes and the circuit common mode noise signal that other extraneous factors produce is all applicable.
Ruo Jin mono-road differential signal presents fault electric arc feature, and so fault electric arc occurs in and formed in the first photovoltaic string of this road differential signal or last photovoltaic string; If adjacent two paths of differential signals all presents fault electric arc feature, so fault electric arc occurs in the common photovoltaic string of this two paths of differential signals of formation.
Step 2) in zero differential signal make DC Line Fault electric arc detecting device port output low level and keep, instruction photovoltaic system be in this state that takes place frequently of normal operating conditions.
The present invention has technique effect useful as follows:
This invention removes the common mode signal components caused by the factors such as crosstalk in photovoltaic system fault electric arc signal to be detected, also can detect accurately and effectively for the fault electric arc betiding photovoltaic system under this kind of common-mode signal interference existent condition, to make under above-mentioned interference environment the DC Line Fault arc protection device still only accurately and reliably in action failure circuit, continue maintenance and be integrated in normal photovoltaic module, DC Line Fault arc protection device on photovoltaic string normally works, the total system protective device chain reaction phenomenon also avoiding local fault electric arc to cause while timely disengagement failure arc suppression disaster hidden-trouble, make photovoltaic system still can utilize all the other normal assembly Maximum Power Outputs of system in these cases, significantly promote the economic benefit of photovoltaic system, the present invention excises fault photovoltaic module in time after discovery fault electric arc, and adjustment balancing gain now, make the still energy normal table work of all the other photovoltaic modulies, substantially prolongs effective generating dutation of photovoltaic system, add the economic benefit of system, the scope restriction corrected by balancing gain guarantees that arbitrary neighborhood photovoltaic string photovoltaic module quantity gap is limited in certain scope, ensures the reliable and stable running status of photovoltaic system, the present invention is owing to eliminating the common mode signal components of arbitrary neighborhood photovoltaic string caused by the factors such as crosstalk based on signal differential conversion, other common-mode signals that electromagnetic environment residing for arbitrary neighborhood photovoltaic string is additional can also be eliminated, realize the filtering of the common mode signal components treated in DC Line Fault arc current checkout gear analytic signal, enhance the reliability and sensitivity that fault electric arc detects.
Further, the method hardware implementing is simple, only in former photovoltaic system, need add balance correction output device and signal processing apparatus between sampled signal device and DC Line Fault electric arc detecting device, the balancing gain for signal corrects and differential conversion process, with low cost; The method also can realize by software whole process, and only need set up detection signal input port at DC Line Fault electric arc detecting device, in DC Line Fault electric arc detecting device software program, only need increase signal processing, Programming Principle is simple, realizes with low cost.
Further, the method is not when breaking down arc event, adjustment balancing gain, and after the arc event that breaks down, keep balancing gain current set value constant, avoid photovoltaic system itself and export difference and the output signal interference that causes, effective guarantee non-zero differential signal is only caused by fault electric arc, and the system that enhances is introduced by factors such as crosstalk the reliability that fault electric arc under common-mode signal disturbed condition detects.
Further, the method can adopt simple signal processing circuit model realization, can comparatively easily realize carrying out type conversion to electric quantity signal while carrying out difference to sampling electric quantity signal, so the sampled signal type of sample circuit has nothing to do with the analytic signal type of DC Line Fault electric arc detecting device, thus having widened the alternative signal collection that photovoltaic system fault electric arc detects signature analysis, having solved the signal type of fault electric arc Algorithm Analysis requirement with detecting the problems such as corresponding signal type difficulty contradicts.
Further, the method can adopt and first judge whether differential signal is the zero sequential processing order of then only the non-zero differential signal that may be caused by fault electric arc being carried out to fault electric arc detection, low level output instruction photovoltaic system is adopted to be in the normal mode running this state that takes place frequently, the significant increase rapidity of photovoltaic system signal transacting, makes whole DC Line Fault electric arc detecting device be in efficiently succinct operating state.
Accompanying drawing explanation
Fig. 1 a is one of photovoltaic system fault arc detection method flow chart under common-mode signal disturbed condition of the present invention;
Fig. 1 b is the photovoltaic system fault arc detection method flow chart two under common-mode signal disturbed condition of the present invention;
Fig. 1 c is the photovoltaic system fault arc detection method flow chart three under common-mode signal disturbed condition of the present invention;
Fig. 2 a is one of application software of the present invention photovoltaic system theory diagram when realizing;
Fig. 2 b is the photovoltaic system theory diagram two of application software of the present invention when realizing;
Fig. 3 a is that the present invention is applied to the specific photovoltaic system principle diagram comprising the DC Line Fault electric arc detecting device being integrated in inverter;
Fig. 3 b is the signal processing apparatus circuit model in Fig. 3 a;
Fig. 4 a is that the present invention is applied to the specific photovoltaic system principle diagram comprising the DC Line Fault electric arc detecting device being integrated in photovoltaic string;
Fig. 4 b is the signal processing apparatus circuit model in Fig. 4 a;
Fig. 5 a is that the present invention is applied to the specific photovoltaic system principle diagram comprising the DC Line Fault electric arc detecting device being integrated in photovoltaic module;
Fig. 5 b is the signal processing apparatus circuit model in Fig. 5 a;
In figure: 1, photovoltaic system; 2, DC Line Fault electric arc detecting device; 3, inverter; 4, order wire; 5, trip gear; 6, circuit breaker; 7, AC network; 8, electricity device is detected; 9, short switch; 10, photovoltaic module; 11, balance correction output device; 12, signal processing apparatus.
Embodiment
Below in conjunction with drawings and Examples, the present invention is described in detail.
See Fig. 1 a, photovoltaic system fault arc detection method under a kind of common-mode signal disturbed condition: when confirming not break down arc event in photovoltaic system, the balancing gain in output device is corrected by adjustment, avoid producing because of the equal factor of the even or contained photovoltaic module quantity of uneven illumination between photovoltaic system arbitrary neighborhood two photovoltaic string the situation that differential signal exports, the differential signal ensureing between photovoltaic system arbitrary neighborhood photovoltaic string exports and is only caused by fault electric arc; Again by carrying out differential conversion process to the detection signal between photovoltaic system arbitrary neighborhood two photovoltaic string, eliminate the common mode signal components caused by factors such as crosstalk that photovoltaic system detection signal comprises, then use DC Line Fault electric arc detecting device to utilize the non-zero differential signal of gained to complete fault electric arc and detect; When breaking down electric arc, excise the fault photovoltaic module after fault location confirms, now the place photovoltaic string of this excision fault photovoltaic module may there are differences with adjacent photovoltaic string U-I output characteristic curve, should re-establish the balancing gain in balance correction output device according to the sampling electricity now reading in adjacent photovoltaic string; Judge that photovoltaic system arbitrary neighborhood two string exports the gap of electricity by the balancing gain current set value in balance correction output device, still ensure that photovoltaic system is with peak power output stable operation when arbitrary neighborhood two photovoltaic string output electricity gap is little, until balancing gain to exceed setting range side out of service, ensure the stable operation of photovoltaic system, extend the time of system maximum power output.The present invention greatly improves the fault electric arc of photovoltaic system under the conditions such as crosstalk and detects prevention ability, avoid the malfunction problem of conventional detection devices under the factors such as crosstalk introduce common-mode signal disturbed condition, enhance the ability that photovoltaic system keeps maximum power output and fault electric arc location.
Composition graphs 1b, is specifically described the step of the photovoltaic system fault arc detection method under common-mode signal disturbed condition of the present invention.
Step one, initialization procedure: in balance correction output device balancing gain G be set as 1 (photovoltaic system complete during initialization is in uniform photoenvironment E, makes whole system work in rated condition (I, U), wherein, I=I
n, U=U
n, I
nfor rated current, U
nfor rated voltage, it is substantially close that each photovoltaic string exports electricity), selected signal processing apparatus (sampling electric quantity signal type decided signal processing apparatus input signal types, DC Line Fault electric arc detecting device analyzes electric quantity signal type decided signal processing apparatus output signal type), DC Line Fault electric arc detecting device port reset, event of failure times N resets and resets and arrange order wire communication mode etc.
Step 2, balance correction output device are every certain sampling time T
1read in the sampling electric quantity signal of adjacent two strings, after reading in, a photovoltaic string sampling electric quantity signal directly exports, and another photovoltaic string sampling electric quantity signal need be exportable through balancing gain rear.Wherein, the principle that balancing gain corrects does not break down in arc event situation to ensure that the differential conversion signal inputing to DC Line Fault electric arc detecting device is zero.Balance correction output device automatically latches and directly exports photovoltaic string sampling electric quantity signal M.
Wherein, sampling time T
1less, sample frequency f
1higher, faster to the speed of sampling electric quantity signal process, produce the differential signal being fed through DC Line Fault electric arc detecting device also faster, so just, more accurate to the detection of fault electric arc event generation time, the sensitivity that DC Line Fault electric arc detecting device in photovoltaic system detects fault electric arc is also higher, maximum fault electric arc requirement break time that combined with hardware design is considered and American Standard is concluded, f
1generally be taken as 10kHz ~ 50kHz.
Step 3, signal processing apparatus receiving balance correct the two-way electric quantity signal that exports of output device, and a road is photovoltaic string Direct Sampling electric quantity signal, and the neighbour of another Lu Weijing balancing gain process goes here and there sampling electric quantity signal.In order to highlight the effect of fault electric arc to sampling electric quantity signal, from unitary variant principle, should ensure that the adjacent two string sampling electric quantity signal types inputing to signal processing apparatus are consistent, namely crude sampling electric quantity signal type should be consistent.Then signal processing apparatus is according to set function, two input signals of device is carried out difference processing and carries out electric quantity signal type conversion, generates the characteristic signal treating the process of DC Line Fault electric arc detecting device.
The electric quantity signal through differential conversion process that step 4, DC Line Fault electric arc detecting device Received signal strength processing unit export, judges whether this electric quantity signal through differential conversion process exceeds setting range N
0.If do not exceed setting range N
0, then show that the signal processing apparatus of corresponding adjacent two photovoltaic strings does not export effective non-zero differential signal, judge current sample time input to corresponding adjacent two photovoltaic strings of photovoltaic system of signal processing apparatus electricity difference very little, difference can be ignored and think that both are equal, photovoltaic system is in normal operating conditions, DC Line Fault electric arc detecting device port output low level also keeps, the corresponding order wire being connected to balance correction output device also continues output low level, keep the current set value of balancing gain in described balance correction output device constant, then return step 2 and carry out reading in of sampled signal next time, if differential signal exceeds setting range N
0, then show that the signal processing apparatus of corresponding adjacent two photovoltaic strings exports non-zero differential signal, judge that electricity that current sample time inputs to the corresponding adjacent photovoltaic string of photovoltaic system of signal processing apparatus is not etc., this or because of the average effect of photoenvironment residing for photovoltaic string outside different, or because of the photovoltaic module number that comprises of photovoltaic string inside not etc., or because of the noise signal that comprises of photovoltaic string inside not etc., or to cause because breaking down electric arc in photovoltaic string, also need to carry out further situation differentiation, the non-zero input of differential signal makes the transition of DC Line Fault electric arc detecting device port send high level signal and keep, now respective communication line also continuous transmission high level, DC Line Fault electric arc detecting device latches this non-zero differential signal D automatically, then go to step five and carry out fault electric arc signature analysis, determine whether to need the balancing gain in adjustment correction output device.
The average effect being sampled photoenvironment residing for adjacent photovoltaic string outside in pending photovoltaic system is different, even if the photovoltaic module number that two photovoltaic string inside comprise is consistent, but the U-I characteristic curve exported due to each photovoltaic module is closely related with the photoenvironment residing for self, therefore the U-I characteristic curve that in photovoltaic system, adjacent photovoltaic string exports is inevitable also different under different average eguivalent lighting effects, thus produces non-zero differential signal.In like manner, even if the average eguivalent photoenvironment residing for two photovoltaic strings is identical, but the photovoltaic module number comprised due to each photovoltaic string inside is inconsistent, the U-I characteristic curve that in photovoltaic system, adjacent photovoltaic string exports also can be caused different, also can produce non-zero differential signal.Non-zero differential signal under both of these case exports difference by photovoltaic system self to be caused, be not caused by the fault electric arc occurred in system, thus the differential signal that it may be necessary under identification both of these case generates and takes balance correction output device to be eliminated, to guarantee that fault electric arc is the single factor causing the generation of non-zero differential signal, be conducive to the reliability that elevator system fault electric arc detects.
Here the average lighting effect of the different equivalent of indication comprises following situation: 1) photovoltaic system run into that cirrocumulus is sailed, aircraft skims over, leaf is sailed, small bird flies over etc. in short-term illumination variation environment time, in photovoltaic system certain to or several of short duration difference is occurred to the photoenvironment residing for adjacent photovoltaic string, and this light differential makes the U-I output characteristic curve of corresponding adjacent two photovoltaic strings there are differences; 2) along with the movement of position of sun, the object making building, trees etc. have screening effect has blocked the part of module of photovoltaic system, to cause in photovoltaic system certain to or several change procedure photoenvironment residing for adjacent photovoltaic string being occurred to dynamic differential, and this light differential makes the U-I output characteristic curve of corresponding adjacent two photovoltaic strings there are differences; 3) dust spot, fallen leaves, ice and snow is caused on photovoltaic module during the situation such as skewness in ambient weather factor, in photovoltaic system certain to or several light transmission capacity long-term existence difference to adjacent photovoltaic string, and this light differential makes the U-I output characteristic curve of corresponding adjacent two photovoltaic strings there are differences; 4) photovoltaic system self aging action in various degree causes the transformation efficiency of photovoltaic module to illumination there are differences, long-term local pyrexia causes on photovoltaic module and form the situations such as hot spot pockety, in photovoltaic system certain to or several light transmission capacity to adjacent photovoltaic string also long-term existence difference, and this light differential makes the U-I output characteristic curve of corresponding adjacent two photovoltaic strings there are differences.
The noise signal that photovoltaic string inside mentioned here comprises makes a general reference the signal that the electromagnetic noise interference of environment causes residing for system, these signals generally all there are differences between adjacent photovoltaic string in photovoltaic system, namely differential signal can be produced after the process of signal processing apparatus, but its order of magnitude often comparatively uneven illumination, the differential signal order of magnitude caused by photovoltaic module quantity variance is much smaller, after the order of magnitude of this differential signal acquires a certain degree, feature is detected due to fault electric arc can not be fallen into, still can rely on balance correction output device to be eliminated.
Wherein, the output signal setting range N through differential conversion process is limited
0larger, export strictly equal requirement to two adjacent photovoltaic strings lower, the composition that the difference processing signal of output carries photovoltaic system itself affect factor increases the weight of relatively, and the general precision of combined input signal Algorithm Analysis requires consideration, N
0span for-B ~ B, B is 10
-3~ 10
-15.
After step 5, DC Line Fault electric arc detecting device confirmation signal processing unit export non-zero differential signal, being brought into by this differential signal immediately to what set is used in the characteristic quantity calculating formula of signal analysis, obtain the numerical value of individual features amount, and compared with the characteristic quantity threshold value of setting, judge whether to break down in current sample time photovoltaic system arc event.If break down arc event, be then designated as primary fault arc event, corresponding counts variable N counting adds one, goes to step eight; If do not break down arc event, then judge that current photovoltaic system does not break down electric arc, even if N has value to be also the fault electric arc erroneous judgement that accidental factor causes, reset variable N, go to step six.
Wherein, photovoltaic system fault electric arc with routine detects to be compared, feature of the present invention is just the signal processing function of abovementioned steps, make the input signal of DC Line Fault electric arc detecting device be differential signal after balancing gain, differential conversion process and non-immediate is sampled from original system the electric quantity signal obtained, thus the common mode signal components that the crosstalk etc. in elimination primary signal causes, and the differential signal components caused by crosstalk does not possess fault electric arc feature, can be balanced and correct output device compensation elimination.Characteristic quantity and the threshold value of application signal analysis theory acquisition differential signal have been mature technology, do not carry out expansion explanation here.
Step 6, confirmation system do not break down after arc event, judging that photovoltaic string in current sample time photovoltaic system in corresponding adjacent string exports electricity is not etc. caused by photovoltaic system oneself factor, this or because of the average effect of photoenvironment residing for photovoltaic string outside different, or because of the photovoltaic module number that comprises of photovoltaic string inside not etc., or the noise signal comprised because of photovoltaic string inside etc. does not cause.Now order wire is sent to the high level control command of balance correction output device just now effectively, and balance correction output device receives the balancing gain correction instruction sent by DC Line Fault electric arc detecting device through order wire transmission.Thus, balance correction output device is according to setting rule regulating balancing gain: export the balancing gain in electric quantity signal adjustment balance correction output device according to adjacent two photovoltaic strings of current sample time photovoltaic system, exports to eliminate the non-zero differential signal of photovoltaic system current time caused by photovoltaic system self reason.
Balance correction output device, according to the balancing gain G in balance correction output device, the sampling electric quantity signal M, the non-zero differential signal D that directly export photovoltaic string, obtains the sampling electric quantity signal M' of adjacent photovoltaic string according to calculating formula M'=(M-D)/G.Calculating formula G'=M/M' is then utilized to obtain the new balancing gain G' next time sampled signal being carried out to balancing gain correction.After the balancing gain completed in balance correction output device corrects, balance correction output device sends settling signal through order wire to DC Line Fault electric arc detecting device, DC Line Fault electric arc detecting device is made to reset output port, low level output state corresponding when keeping difference processing signal to be zero.
Step 7, judge in balance correction output device, whether balancing gain exceeds setting range, if exceed setting range N
2then judge that the photovoltaic string output electric quantity signal in the corresponding adjacent string of current sample time photovoltaic system has big difference; or reach the upper limit because excising fault photovoltaic module quantity; or cause because suffered light differential is huge; the electricity off-rating that under this state, photovoltaic system members bears; the destabilizing factor of system works increases, and should take safeguard measure and make photovoltaic system quit work, safeguarding.If do not exceed setting range N
2then judge that the photovoltaic string output electric quantity signal in the corresponding adjacent string of current sample time photovoltaic system is more or less the same, even if excise a small amount of fault photovoltaic module or face the little illumination variation environment of difference, system component still can reliably normally run, can continue to maintain photovoltaic system normal power generation state, return step 2 and carry out reading in of sampled signal next time.
Wherein, balancing gain G is larger, and the adjacent string U-I output characteristic curve difference that photovoltaic system allows is larger, and the fault photovoltaic module quantity that system can be excised is more, the uneven illumination environment that can bear is larger, greatly can extend the time of system peak power output thus.But when photovoltaic system adjacent photovoltaic string U-I output characteristic curve difference reaches capacity, the undertension that minimal pressure photovoltaic string provides normally works to maintain inverter, export even if photovoltaic system exists electricity, also cannot be fed to electrical network through inverter conversion.Also can there is the phenomenon of high pressure photovoltaic string to low pressure photovoltaic string feeding electric current in the photovoltaic system of clog-free diode.Period, the U-I output characteristic curve of low pressure photovoltaic string is positioned at the below of high pressure photovoltaic string U-I output characteristic curve, regulating through MPPT algorithm makes low pressure photovoltaic string find new working point till low pressure photovoltaic string output voltage is equal with high pressure photovoltaic string, and corresponding self output current of low pressure photovoltaic string declines to some extent.When two photovoltaic string difference photovoltaic module quantity are too much, the U-I output characteristic curve of low pressure photovoltaic string then differs larger with pressure photovoltaic string U-I output characteristic curve, point on the U-I output characteristic curve of the now corresponding low pressure photovoltaic string of the magnitude of voltage of high pressure photovoltaic string is positioned at fourth quadrant, namely this low pressure photovoltaic string does not only have output current to accept the feeding electric current of other photovoltaic strings on the contrary, the possibility making low pressure photovoltaic string there is overcurrent to burn.The photovoltaic system of blocking diode is had then to there is not feedback stream circulation phenomenon between photovoltaic string, the output voltage difference of two photovoltaic strings all drops on blocking diode, when difference with aforementioned clog-free diode system is the output voltage of the U-I output characteristic curve open circuit voltage of the low pressure photovoltaic string after excising fault photovoltaic module to greatest extent lower than high pressure photovoltaic string, this low pressure photovoltaic string quits work.
Therefore, setting range N is being determined
2time, following principle should be considered conclude: 1) in the photovoltaic system of particular job, obtain according to its rated voltage current class the maximum voltage electric current tolerance value that photovoltaic string can bear, consider excision a string in photovoltaic module reach limiting value or the worst photoenvironment under the photovoltaic string that produces export the maximum tolerance value that maximal regulated electricity that electricity difference maximum situation causes still is no more than the corresponding electricity of single string; 2) for ensureing that photovoltaic system can continue reliable and stable work, in two photovoltaic string electricity situation with the biggest gap, also namely N is reached
2during boundary, export the minimum operating voltage requirement that the less photovoltaic string of electricity should be able to meet inverter; 3) excise a string in photovoltaic module reach limiting value or the worst photoenvironment under after the photovoltaic string that produces exports electricity difference maximum situation, within the stable operating point after the U-I output characteristic curve after change can guarantee MPPT algorithm adjustment is constrained on short dot and open circuit point; 4) for the type of attachment of the balance correction output device of adjacent string, scope N
2the lower limit of setting and N
2the upper limit should present reciprocal relation.
Step 8, cause the misoperation of DC Line Fault electric arc detecting device in order to avoid accidentalia, by setting fault electric arc event count variable threshold N
1, think that only having fault electric arc event to recur reaches N
1after secondary, just think and improve DC Line Fault electric arc detecting device detecting reliability thus by the electric arc that to break down in system.If N=N
1, then judge to create fault electric arc in photovoltaic system, DC Line Fault electric arc detecting device controls the trip gear cut-off breaker in respective lines, localized resection fault photovoltaic module is to extinguish fault electric arc, and generate fault electric arc process record report in time to supervisor, after keeping excision fault photovoltaic module, remaining photovoltaic module still normally runs work, now the place photovoltaic string of this excision fault photovoltaic module may there are differences with adjacent photovoltaic string U-I output characteristic curve, the balancing gain in balance correction output device should be re-established according to the sampling electricity now reading in adjacent string, reset variable N, therefore return step 2 and carry out reading in of sampled signal next time, if N < is N
1then need to carry out fault electric arc further and detect the judgement avoiding accidental malfunction to disturb fault electric arc, now because system may break down electric arc, in photovoltaic system, the electric quantity change difference of adjacent photovoltaic string may be caused by fault electric arc, the current set value of balancing gain in described balance correction output device should be kept constant, guarantee the differential conversion feature invariant that fault electric arc causes thus, then return step 2 and carry out reading in of sampled signal next time.
Wherein, fault electric arc event count variable threshold N
1larger, detected system charge change is that the probability caused by fault electric arc is higher, and fault electric arc detecting reliability is also higher, and the requirement in conjunction with fast shut-off fault electric arc is considered, N
1generally be taken as 3 ~ 5.
Now need to carry out sampled signal next time to the place photovoltaic string of this excision fault photovoltaic module with adjacent photovoltaic string to read in and do differential conversion process and judge whether differential conversion signal exceeds threshold value N
0, determine whether thus to correct the balancing gain in described balance correction output device, but not the reason of the balancing gain that photovoltaic module number directly corrects in described balance correction output device is contained by foundation two photovoltaic string inside: when needing to correct balancing gain after excision fault photovoltaic module, may by chance there is unbalanced lighting effect, the average lighting effect causing the less photovoltaic string of photovoltaic module number to be subject to is stronger, offset thus excision fault photovoltaic module cause U-I output characteristic curve to reduce effect, if now contained by direct basis two photovoltaic string inside, photovoltaic module number corrects the balancing gain in described balance correction output device, after correction balancing gain can be caused on the contrary to complete, still the differential signal of old non-zero exports.
Complete and to carry out before sampled signal is read in after certain fault electric arc detects excision fault photovoltaic module next time, fault electric arc event count variable N should be reset, avoid now that it is fault electric arc event because of wrong diagnosis when accidental factor causes signal analysis, to dependent variable N=N
1+ 1 direct wrong diagnosis now breaks down electric arc again, and without N
1secondary continuous fault arc event diagnosis.
See Fig. 1 c, the another kind of execution mode of the photovoltaic system fault arc detection method under common-mode signal disturbed condition of the present invention, namely adopt and first carry out fault electric arc and detect this sequential processing mode of judgement of then carrying out differential signal whether non-zero when not breaking down arc event, comprise the following steps:
1) starting stage is run, according to the initial condition of the output situation determination balancing gain of photovoltaic system adjacent photovoltaic crosstalk amount at photovoltaic system;
2) during photovoltaic system runs, by sample frequency f
1the output electric quantity signal of photovoltaic system arbitrary neighborhood two photovoltaic string is sampled, obtain two-way detection signal, wherein after balancing gain, differential conversion process will be carried out with another road detection signal by a road detection signal, DC Line Fault electric arc detecting device is according to the read in sampled signal after balancing gain and differential conversion process, fault electric arc detection is carried out by characteristic quantity Threshold Analysis, and judge whether current sample time breaks down arc event, if break down arc event, then counting variable N counts, and then goes to step 4); If do not break down arc event, then reset counting variable N, then go to step 3);
3) whether DC Line Fault electric arc detecting device exceeds setting range N according to the read in detection signal after balancing gain and differential conversion process
0, judge whether the signal processing apparatus of arbitrary neighborhood two photovoltaic string exports non-zero differential signal, if exceed setting range N
0then to judge in current sample time photovoltaic system that this does not wait the electricity that adjacent photovoltaic string inputs to signal processing apparatus and produces non-zero differential signal, this or because of the average effect of photoenvironment residing for photovoltaic string different, or the photovoltaic module number to comprise because of photovoltaic string is not etc., or to cause because the noise signal that comprises of photovoltaic string inside does not wait, therefore the balancing gain in correction balance correction output device is until be no more than setting range N
0till, then go to step 5); If do not exceed setting range N
0, then judge that current sample time photovoltaic system does not export non-zero differential signal and is in normal condition, then keep the current set value of balancing gain in described balance correction output device constant, then return step 2) carry out sampled signal next time and read in;
4) whether failure judgement arc event recurs, if fault electric arc event recurs N
1secondary, then judge to break down in photovoltaic system electric arc, excision fault photovoltaic module, keep the still normal work of residue photovoltaic system assembly, reset counting variable N, then return step 2) carry out sampled signal next time and read in; If fault electric arc event does not recur N
1secondary, then keep the current set value of balancing gain in described balance correction output device constant, then return step 2) carry out sampled signal next time and read in;
5) judge in balance correction output device, whether balancing gain exceeds setting range N
2if exceed setting range N
2then judge that the photovoltaic string output electric quantity signal in the corresponding adjacent string of current sample time photovoltaic system has big difference, or reach the upper limit because excising fault photovoltaic module quantity, or cause because suffered light differential is huge; take safeguard measure and make photovoltaic system quit work, safeguarding.If do not exceed setting range N
2, then the photovoltaic string judging in current sample time photovoltaic system corresponding adjacent string exports electric quantity signal and is more or less the same, and system component still can reliably normally run, and then returns step 2) carry out sampled signal next time and read in.
What this kind of execution mode adopted is first carries out fault electric arc and detects and then carry out differential signal when not breaking down arc event whether non-zero judges this sequential processing mode.When in most cases the photovoltaic system initial stage of better performances comes into operation, the probability of the electric arc that breaks down is less.Thus, the differential signal most cases exported through signal processing apparatus is zero, does not need the fault eigenvalue being carried out input signal by DC Line Fault electric arc detecting device to extract, analyze, compare completely.Therefore, although this kind of execution mode can realize the thought of the inventive method, but it additionally consumes too much DC Line Fault electric arc detecting device processing signals time and internal memory, be unfavorable for the lifting of photovoltaic system signal transacting rapidity, be more unfavorable for the lifting of whole DC Line Fault electric arc detecting device operating efficiency.
Composition graphs 2, sets forth application removing method of the present invention in the software implementing course comprising DC Line Fault electric arc detecting device photovoltaic system.Due in the present invention to all available algorithm programming realization such as the balancing gain process of signal, differential conversion process, therefore Fig. 2 a and Fig. 2 b provides software simulating the most succinct hardware frame structure chart of the present invention.
Composition graphs 2a, sets forth application removing method of the present invention in the specific photovoltaic system comprising the DC Line Fault electric arc detecting device being integrated in photovoltaic module.
Suppose that the photovoltaic system in Fig. 2 a comprises J photovoltaic string; each photovoltaic string comprises K photovoltaic module; corresponding photovoltaic module 10 has J × K; with it the detection electricity device 8 of complete configuration, DC Line Fault arc protection device (trip gear 5, circuit breaker 6, short switch 9) is corresponding is also J × K; because every two sampling electric quantity signals carry out differential conversion process, fault electric arc analysis by a DC Line Fault electric arc detecting device 2, therefore total (J-1) × K of this checkout gear.Under normal circumstances, photovoltaic system 1 exports direct current power, and input in inverter 3 through circuit breaker 6, detection electricity device 8, direct current is changed into alternating current and is delivered to AC network 7 by inverter 3.According to design philosophy of the present invention, DC Line Fault electric arc detecting device 2 reads in the sampling electric quantity signal of the same type of same position place photovoltaic module between adjacent string, and this sampling electric quantity signal completes detection by detecting electricity device 8.Then complete a series of function such as balancing gain computing and correction, differential conversion process, fault electric arc detection by the software program in DC Line Fault electric arc detecting device 2.
Due to each DC Line Fault electric arc detecting device 2 judgement is whether the differential signal of the photovoltaic module output of corresponding position in adjacent string is containing fault electric arc feature, cause so this fault electric arc may be any one fault in two photovoltaic modules, thus the output control terminal of each DC Line Fault electric arc detecting device 2 controls photovoltaic module two trip gear 5 of corresponding sampling electricity.After completing fault electric arc location, send control signal and make the action and guarantee that another normal photovoltaic module still normally runs together with short switch 9 of the circuit breaker 6 at fault photovoltaic module place.Photovoltaic system self may be caused to export the lack of balance of electricity after excision fault photovoltaic module, thus be necessary the differential signal setting range N carrying out next sampling instant
0and the judgement of fault electric arc, carrying out balancing gain correction when not breaking down arc event, when the output electricity gap of two photovoltaic strings is little, still maintaining the operation of photovoltaic system, promote photovoltaic system running time; And when the output electricity gap of two photovoltaic strings larger possibility initiating system job insecurity, then cut off all photovoltaic modules immediately, stop the operation of photovoltaic system.
Because the simultaneous probability of photovoltaic system fault electric arc is extremely low, so the fault electric arc under current sample time is generally single fault.If treated differential signal after testing after diagnostic system to break down electric arc, then illustrate that this to break down electric arc to a certain photovoltaic module of adjacent photovoltaic module being in same position place; If treated differential signal after testing after diagnostic system not break down electric arc, then illustrate that this is all in normal condition to the adjacent photovoltaic module being in same position place.Such as, first string first photovoltaic module and second is gone here and there the differential signal that first photovoltaic module export and is shown fault electric arc feature, second string first photovoltaic module and the 3rd is gone here and there the differential signal that first photovoltaic module export and is not shown fault electric arc feature, then should excise the first string first photovoltaic module, corresponding first string and second go here and there between DC Line Fault electric arc detecting device control output end export " 10 ", second string and the 3rd go here and there between DC Line Fault electric arc detecting device control output end export " 00 " (high level be effective, DC Line Fault arc protection device sends the signal of action trip gear 5), first string first photovoltaic module and second is gone here and there the differential signal that first photovoltaic module export electricity and is shown fault electric arc feature, second string first photovoltaic module and the 3rd is gone here and there the differential signal that first photovoltaic module export and is shown fault electric arc feature, then should excise the second string first photovoltaic module, corresponding first string and second go here and there between DC Line Fault electric arc detecting device control output end export " 01 ", second go here and there and the 3rd go here and there between DC Line Fault electric arc detecting device control output end export " 10 ".
In like manner; the hardware frame figure that the specific photovoltaic systems soft ware comprising the DC Line Fault electric arc detecting device being integrated in photovoltaic string realizes is consistent with the version of Fig. 2 a; DC Line Fault electric arc detecting device 2 is J-1; detecting electricity device 8 is J, and DC Line Fault arc protection device (trip gear 5, circuit breaker 6, short switch 9) is J × K.Difference is mainly: the first, though DC Line Fault electric arc detecting device 2 still only has two input signal ports, should read in the sampling electric quantity signal of the same type at the upper same position place of string between adjacent string; Second, DC Line Fault electric arc detecting device 2 still only has an output signal port, the photovoltaic string at fault electric arc place is first tentatively determined according to aforesaid fault electric arc location thought, then or take to scan one by one, or take fault dictionary method, realize the location of syndrome serial internal fault photovoltaic module again, namely in Fig. 2 a, the fault photovoltaic module of " Column Row " locates thought.
Composition graphs 2b, sets forth application removing method of the present invention in the specific photovoltaic system comprising the DC Line Fault electric arc detecting device being integrated in inverter.
In structure, the specific photovoltaic systems compliant of the DC Line Fault electric arc detecting device being integrated in inverter is comprised with routine, DC Line Fault electric arc detecting device 2 only 1, but handled signal is not the detection electric quantity signal in photovoltaic system bus, but equivalent process is integrated in the differential signal inputing to J-1 DC Line Fault electric arc detecting device 2 in the specific photovoltaic system of photovoltaic string, J input signal port is namely set, for reading in the sampling electric quantity signal of the same type at all photovoltaic string same position places, this testing process detects electricity device 8 by J and realizes.J sampling electric quantity signal reads in in DC Line Fault electric arc detecting device 2, and the input sample electric quantity signal of every two adjacent string of parallel processing simultaneously, obtains J-1 the differential signal that pending fault electric arc is analyzed after balancing gain, differential conversion process.For excising corresponding fault photovoltaic module, the DC Line Fault arc protection device (trip gear 5, circuit breaker 6, short switch 9) be equipped with still is J × K.
DC Line Fault electric arc detecting device 2 correspondence has J output signal port, controls each photovoltaic string one by one successively.Tentatively determine the photovoltaic string at fault electric arc place according to aforesaid fault electric arc location thought, then or take to scan one by one, or take fault dictionary method, all can realize the location of syndrome serial internal fault photovoltaic module.For example, when determining that J photovoltaic string K photovoltaic module fault need be excised, DC Line Fault electric arc detecting device 2 J output control terminal mouth exports control signal " 0...01 " (altogether K-1 individual 0).Therefore, the DC Line Fault electric arc detecting device being integrated in inverter side is just integrated with the function sum that aforementioned J-1 is integrated in the DC Line Fault electric arc detecting device of photovoltaic string, internal algorithm program and processing procedure do not change, and what change is only DC Line Fault electric arc detecting device input/output port number.
Composition graphs 3, Fig. 4, Fig. 5, set forth application removing method of the present invention in the hardware implementing process comprising DC Line Fault electric arc detecting device photovoltaic system.Because the signal processing apparatus in the present invention not only has difference effect to sampling electric quantity signal, also has the effect of electric quantity signal type conversion, so the sampled signal type of sample circuit has nothing to do with the analytic signal type of DC Line Fault electric arc detecting device, thus widen the alternative signal collection that photovoltaic system fault electric arc detects signature analysis, solve the problems such as the contradiction of fault electric arc Algorithm Analysis requirement signal type same detection corresponding signal type difficulty.For embodying the convertible sampled signal of signal processing apparatus and this advantage of analytic signal, in conjunction with broad field of application of the present invention, the DC Line Fault electric arc detecting device photovoltaic system here for each specific integrated form provides the signal processing apparatus circuit model realizing signal with different type conversion.
Composition graphs 3a and Fig. 3 b, sets forth application removing method of the present invention in the signal processing of the specific photovoltaic system and inside that comprise the DC Line Fault electric arc detecting device being integrated in inverter.
As shown in Figure 3 a, adopt the frame structure being similar to Fig. 2 b, the differential signal that just DC Line Fault electric arc detecting device 2 inputs is realized by hardware unit, namely the sampling electric quantity signal at two photovoltaic string same position places of arbitrary neighborhood after testing electricity device 8 obtain after, through balance correction output device 11, signal processing apparatus 12 process after obtain J-1 to be detected differential conversion signal.After these differential signals synchronously input to DC Line Fault electric arc detecting device 2, parallel processing is carried out to these signals in J-1 input port: when the differential signal of input is in setting range, system is in normal operating conditions, detects the electric quantity signal sampling that electricity device 8 carries out subsequent time; When differential input signal is not in setting range, think that input signal is effective, the order wire being connected to balance correction output device keeps high level instruction, this non-zero differential signal is then used to carry out fault electric arc detection, when not breaking down arc event, resetting counting variable N, getting rid of the accidentalia causing erroneous judgement, the high level instruction of balance correction output device 11 received communication line transmission, with the left electricity inputted for benchmark carries out balancing gain correction according to established principle to right wing.
If photovoltaic system runs into the average lighting effect of aforementioned different equivalent, to make in photovoltaic system certain to or several adjacent photovoltaic string U-I output characteristic curve to be there are differences, just need to correct balancing gain.For example, current sample time has obtained the sampling electric quantity signal M=U (U is the output voltage electricity of this photovoltaic string), the non-zero differential signal D=CU (C is constant) that directly export photovoltaic string, obtains new balancing gain G'=G/ (1-C) by the balancing gain G in current sample time balance correction output device 11.After completing the write of new balancing gain, balance correction output device 11 sends settling signal through order wire 4 to DC Line Fault electric arc detecting device 2, DC Line Fault electric arc detecting device 2 is made to reset output port, the Status Flag that the zero differential signal that Recovery processing exports is corresponding.
During the arc event that breaks down, balance correction output device 11 ignores the high level instruction of order wire transmission, keep balancing gain current set value constant, the differential signal that DC Line Fault electric arc detecting device 2 inputs is constant, remains that original fault electric arc characteristic signal proceeds fault electric arc testing process thus.Corresponding counts variable N adds 1, only has when this counting variable reaches setting threshold N
1just judge to create fault electric arc in photovoltaic system, DC Line Fault electric arc detecting device 2 carries out the location of fault photovoltaic string, fault photovoltaic module successively by aforementioned principle, control signal is exported by corresponding output port, control trip gear 5 cut-off breaker 6, extinguish fault electric arc, and action short switch 9 excises fault photovoltaic module and keeps the still normal operation of other assemblies of photovoltaic system, generate fault electric arc process record, in time to supervisor's report, then carry out the electricity processing procedure in next sampling period.
The fault photovoltaic module excision that this process is carried out will inevitably cause adjacent photovoltaic string output electric quantity signal not, and need the correction carrying out balancing gain, trimming process is similar to the trimming process under the average lighting effect of different equivalent.Here this correction thought can be understood by the following correction fact in particular cases: such as, certain is in photovoltaic string, the photovoltaic module number of normal photovoltaic string is K, syndrome serial after another excision fault photovoltaic module is that (K-1) is individual, obvious current sample time fault photovoltaic string does not also have enough time to carry out MPPT adjustment, when not considering the average lighting effect of two strings and photovoltaic module self electric quantity exports difference, the new balancing gain parameter G'=K/ (K-1) in the balance correction output device 11 calculated by aforementioned principle.Then along with the lifting of fault photovoltaic string voltage, the corresponding magnitude of current is through the adjustment of MPPT, and the working point of photovoltaic string constantly changes, and the electricity gap of adjacent string forms the Dynamic Regulating Process of balancing gain.
After each balancing gain corrects, judge whether it exceeds setting range, if exceed setting range N
2then judge that the photovoltaic string output electric quantity signal in the corresponding adjacent string of current sample time photovoltaic system has big difference, now photovoltaic system enters labile state, is no longer applicable to working on; should safeguard measure be taked and make photovoltaic system quit work, safeguarding.If do not exceed setting range N
2then judge that the photovoltaic string output electric quantity signal in the corresponding adjacent string of current sample time photovoltaic system is more or less the same, even if now photovoltaic system excises a small amount of fault photovoltaic module or the illumination variation environment that faces difference little still can reliably normally run, next cycle electricity sampling can be carried out and continue to maintain photovoltaic system normal power generation state.Aforementionedly mention, the signal difference that the noise signal that on circuit, some is produced by equipment such as inverters causes and order balancing gain depart from 1, and it is still at required N
2in scope, system still can be made to be regarded as normal condition and to continue to run.
As shown in Figure 3 b, it is voltage signal that the input of signal processing apparatus 12 detects electricity type, and two input ports due to device are voltage signal U
1, U
2, therefore the input impedance of this device is high impedance, carries out difference processing and signal demand carries out subtraction process to it, and after differential voltage output signal U after VCVS conversion (voltage amplification factor β=1) must convert
out, be also voltage signal owing to exporting, therefore the output impedance of this device is Low ESR.Therefore, as long as signal processing apparatus 12 meets the circuit model shown in Fig. 3 b, just can sample detection electricity device 8 the voltage signal U obtained
1, U
2carry out differential conversion process, obtain treating that DC Line Fault electric arc detecting device 2 carries out the differential voltage input signal U of fault electric arc analysis
out=U
1-U
2.
Composition graphs 4a and Fig. 4 b, sets forth application detection method of the present invention in the signal processing of the specific photovoltaic system and inside that comprise the fault arc detection device being integrated in photovoltaic string.
As shown in fig. 4 a, compare with Fig. 3 a, be J-1 but not a DC Line Fault electric arc detecting device 2, corresponding failure photovoltaic module location is realized by preceding method, when the fault photovoltaic module of 2nd ~ J-1 middle photovoltaic string need excise, two the DC Line Fault electric arc detecting devices 2 relevant to this photovoltaic string all can send command adapted thereto, and two ends photovoltaic string then only has a DC Line Fault electric arc detecting device 2 to send command adapted thereto.For example, when having determined that J-1 photovoltaic string K photovoltaic module fault need be excised, J-2 the DC Line Fault electric arc detecting device 2 output control terminal mouth in left side exports control signal " 0...0 " (altogether K 0), " 0...01 " (altogether K-1 0) to J-2 photovoltaic string, J-1 photovoltaic string successively, and J-1 the DC Line Fault electric arc detecting device 2 output control terminal mouth on right side is successively to J-1 photovoltaic string, J photovoltaic string output control signal " 0...01 " (being total to K-1 individual 0), " 0...0 " (being total to K individual 0).
What will remark additionally here is one of the inventive method remarkable result: other common-mode signals had by signal differential conversion elimination arbitrary neighborhood string, are realized the filtering of common mode signal noise, enhance the reliability and sensitivity that fault electric arc detects.In general, the inverter switching device noise signal in photovoltaic system can send from inverter, propagates along each photovoltaic string to the side away from inverter, and its characteristic signal frequency range presents the feature of common mode on each photovoltaic string, adds the difficulty that fault electric arc detects.Thus the mutual connection structure of this arbitrary neighborhood two of Fig. 4 a photovoltaic string can eliminate the interference that inverter noise signal detects fault electric arc effectively.
As shown in Figure 4 b, it is voltage signal that the input of signal processing apparatus 12 detects electricity type, and two input ports due to device are voltage signal U
1, U
2, therefore the input impedance of this device is high impedance, carries out difference processing and signal demand carries out subtraction process to it, and after difference current output signal I after VCCS conversion (amplifying admittance g=1) must convert
out, due to output current signal, therefore the output impedance of this device is high impedance.Therefore, as long as signal processing apparatus 12 meets the circuit model shown in Fig. 4 b, just can sample detection electricity device 8 the voltage signal U obtained
1, U
2carry out differential conversion process, obtain treating that DC Line Fault electric arc detecting device 2 carries out the difference current input signal I of fault electric arc analysis
out=g (U
1-U
2).
Composition graphs 5a and Fig. 5 b, sets forth application detection method of the present invention in the signal processing of the specific photovoltaic system and inside that comprise the DC Line Fault electric arc detecting device being integrated in photovoltaic module.
As shown in Figure 5 a, adopt the frame structure being similar to Fig. 2 a, the differential signal that just DC Line Fault electric arc detecting device 2 inputs is realized by hardware unit, and sets up order wire 4.
As shown in Figure 5 b, it is current signal that the input of signal processing apparatus 12 detects electricity type, and two input ports due to device are current signal I
1, I
2, therefore the input impedance of this device is Low ESR, carries out difference processing and signal demand carries out subtraction process to it, and after difference current output signal I after CCCS conversion (current amplification factor β=1) must convert
out, be also current signal owing to exporting, therefore the output impedance of this device is high impedance.Therefore, as long as signal processing apparatus 12 meets the circuit model shown in Fig. 5 b, just can sample detection electricity device 8 the current signal I obtained
1, I
2carry out differential conversion process, obtain treating that DC Line Fault electric arc detecting device 2 carries out the difference current input signal I of fault electric arc analysis
out=I
1-I
2.
In a word, photovoltaic system fault arc detection method under above-mentioned common-mode signal disturbed condition, by the detection signal between differential conversion process photovoltaic system arbitrary neighborhood two photovoltaic string, eliminate the common mode signal components caused by factors such as crosstalk that detection signal comprises, then utilize the differential conversion signal of gained to carry out fault electric arc detection by DC Line Fault electric arc detecting device.Simultaneously, the present invention is not when breaking down arc event, the non-zero differential signal corrected between adjacent photovoltaic string by balancing gain is exported, get rid of the situation that checkout gear input signal affects by other variance factors, after excising fault photovoltaic module when breaking down electric arc, continuous service is until balancing gain exceeds setting range, extends the system maximum power output time.The present invention efficiently solves the fault arc detection device be positioned on regular link to be affected and the problem of malfunction by the common mode signal components caused by factors such as crosstalk, avoid local fault electric arc initiation total system out of service, drastically increase the system failure electric arc location prevention ability under Signal transmissions disturbed condition.
Claims (8)
1. the photovoltaic system fault arc detection method under common-mode signal disturbed condition, is characterized in that: comprise the following steps:
The first step, elimination photovoltaic system fault electric arc detect common-mode signal interference
In photovoltaic system running, to photovoltaic system arbitrary neighborhood two photovoltaic string synchronized sampling, balancing gain and differential conversion process are carried out successively to the output electric quantity signal that sampling obtains;
Second step, the differential signal utilizing differential conversion process to obtain by DC Line Fault electric arc detecting device carry out fault electric arc detection;
3rd step, according to fault electric arc testing result, when not breaking down arc event, correct according to non-zero Difference signal pair balancing gain, balancing gain after correction makes photovoltaic system continuous service when not exceeding setting range, when breaking down electric arc, excise corresponding photovoltaic string internal fault photovoltaic module, then make photovoltaic system continue to run until balancing gain exceeds setting range, the principle correcting balancing gain ensures when not breaking down arc event that the signal inputing to DC Line Fault electric arc detecting device is zero differential signal.
2. the photovoltaic system fault arc detection method according to claim 1 under a kind of common-mode signal disturbed condition, is characterized in that: specifically comprise the following steps:
1) starting stage is run, according to the initial condition of the output situation determination balancing gain of photovoltaic system adjacent photovoltaic crosstalk amount at photovoltaic system;
2) during photovoltaic system runs, by sample frequency f
1the output electric quantity signal of photovoltaic system arbitrary neighborhood two photovoltaic string is sampled, obtain two-way detection signal, wherein after balancing gain, will carry out differential conversion process with another road detection signal by a road detection signal, whether DC Line Fault electric arc detecting device exceeds setting range N according to the read in detection signal after balancing gain and differential conversion process
0, judge whether the electric quantity signal read in forms non-zero differential signal, if exceed setting range N
0, then judge that in current sample time photovoltaic system, corresponding adjacent two photovoltaic strings output electric quantity signals form non-zero differential signal after balancing gain and differential conversion process, go to step 3); If do not exceed setting range N
0then judge that corresponding adjacent two photovoltaic strings of current sample time photovoltaic system export electric quantity signal and form zero differential signal after balancing gain and differential conversion process, keep the set point of current balancing gain constant, then carry out reading in through the detection signal of balancing gain and differential conversion process next time;
3) DC Line Fault electric arc detecting device is according to read in non-zero differential signal, fault electric arc detection is carried out by characteristic quantity Threshold Analysis, and judge whether current sample time breaks down arc event, if break down arc event, then counting variable N counts, and then goes to step 4); If do not break down arc event, then reset counting variable N, the output electric quantity signal according to corresponding adjacent two photovoltaic strings of current sample time photovoltaic system corrects balancing gain, then goes to step 5);
4) whether failure judgement arc event recurs: if fault electric arc event recurs N
1secondary, then judge to break down in current sample time photovoltaic system electric arc, excision fault photovoltaic module, keep the still normal work of residue photovoltaic system assembly, reset counting variable N, then return step 2); If fault electric arc event does not recur N
1secondary, then keep the set point of current balancing gain constant, then return step 2);
5) judge whether balancing gain exceeds setting range N
2if exceed setting range N
2, then judge that the corresponding adjacent photovoltaic string of current sample time photovoltaic system exports electric quantity signal and has big difference, take safeguard measure and make photovoltaic system quit work, if do not exceed setting range N
2, then judge that the corresponding adjacent photovoltaic string of current sample time photovoltaic system exports electric quantity signal and is more or less the same, photovoltaic system still can reliably normally run, and returns step 2).
3. the photovoltaic system fault arc detection method according to claim 2 under a kind of common-mode signal disturbed condition, is characterized in that: described sample frequency f
1span be 10kHz ~ 50kHz, setting range N
0span for-B ~ B, B is 10
-3~ 10
-15, N
1span be 3 ~ 5.
4. the photovoltaic system fault arc detection method according to claim 1 under a kind of common-mode signal disturbed condition, it is characterized in that: when using software simulating to eliminate photovoltaic system fault electric arc detection common-mode signal interference, DC Line Fault electric arc detecting device need be set up photovoltaic module and export electric quantity signal input port, and balancing gain corrects and software simulating in differential conversion processing and utilizing DC Line Fault electric arc detecting device; When using hardware implementing to eliminate photovoltaic system fault electric arc detection common-mode signal interference, need detect the balance correction output device that to arrange between electricity device and DC Line Fault electric arc detecting device and correct for balancing gain and the signal processing apparatus for differential conversion process in photovoltaic system, balancing gain corrects and is realized by the communication between balance correction output device and DC Line Fault electric arc detecting device.
5. the photovoltaic system fault arc detection method according to claim 4 under a kind of common-mode signal disturbed condition, it is characterized in that: when photovoltaic system of sampling exports electricity, should ensure that the output electricity type of sampling from adjacent two photovoltaic strings is consistent, the output electric quantity signal for the adjacent photovoltaic string being inputed to same DC Line Fault electric arc detecting device by described input port should have consistent electricity type.
6. the photovoltaic system fault arc detection method according to claim 1 under a kind of common-mode signal disturbed condition, is characterized in that: the method that described elimination photovoltaic system fault electric arc detects common-mode signal interference is to eliminating crosstalk common mode component that photovoltaic system fault electric arc causes and the circuit common mode noise signal that other extraneous factors produce is all applicable.
7. the photovoltaic system fault arc detection method according to claim 1 under a kind of common-mode signal disturbed condition, it is characterized in that: Ruo Jin mono-road differential signal presents fault electric arc feature, so fault electric arc occurs in and is formed in the first photovoltaic string of this road differential signal or last photovoltaic string; If adjacent two paths of differential signals all presents fault electric arc feature, so fault electric arc occurs in the common photovoltaic string of this two paths of differential signals of formation.
8. the photovoltaic system fault arc detection method according to claim 2 under a kind of common-mode signal disturbed condition, it is characterized in that: step 2) in zero differential signal make DC Line Fault electric arc detecting device port output low level and keep, instruction photovoltaic system be in this state that takes place frequently of normal operating conditions.
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