CN104601105A - Arc detection method for fault of photovoltaic system under abnormal light condition - Google Patents
Arc detection method for fault of photovoltaic system under abnormal light condition Download PDFInfo
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Abstract
The invention discloses an arc detection method for the fault of a photovoltaic system under an abnormal light condition. When an MPPT algorithm dynamic regulating system operating point is not caused by a fault arc accident, by allowing the fault arc characteristic quantity threshold value to tightly track the system operation point variation curve regulated by the MPPT algorithm, the circumstances that the fault arc detection electric quantity varies dynamically or lowers continuously caused by light change can be dealt, and the detection device can effectively detect fault arc in the photovoltaic system at any time can be ensured. According to the detection method, the fault arc detection precaution capacity of the photovoltaic system under abnormal light condition caused by changes of weather and environment is greatly improved, the misoperation problem caused by that the original set threshold value of the photovoltaic fault arc protection device is invalid is effectively solved, and the loophole that the traditional detection device is difficult to detect potential arc threats under the special situations is filled.
Description
Technical field
The invention belongs to the electric fault detection technique field of photovoltaic, be specifically related to a kind of photovoltaic system working point regulated based on inverter MPPT algorithm under improper illumination condition, DC Line Fault electric arc detecting device dynamically follows the tracks of these working points to adjust the judging characteristic amount threshold value of setting, realizes the method for photovoltaic system internal fault arc-detection under improper illumination condition.
Background technology
Along with growing tension and the environment sustainable development requirement of global energy, the regenerative resource of this novel environment friendly of photovoltaic generation obtains applying more and more widely at residential electricity consumption and industry and commerce field.In photovoltaic generating system, fault electric arc is normally aging by line insulation, damaged or electric loop exists bus cases etc. and connects and to loosen etc. that not operation reason causes.Fault electric arc can absorb most of energy of photovoltaic system generation and transfer high-temperature ionized gas to when occurring, owing to lacking the supervision of omnibearing DC Line Fault checkout gear, cable, electric equipment and header box obviously can burn by this lasting high-temperature gas; A large amount of heat that fault electric arc discharge sustain is released also may light the inflammable explosive article around photovoltaic system, finally causes region area to have a power failure and explosive fire accident accident, very easily causes the property loss even threat to life safety of photovoltaic system assembly and related facility.Therefore, under improper illumination condition, under any circumstance especially accurately detect also open failure electric arc is the fundamental way of taking precautions against hazardous accidents.
1999; cooperated the U.S. GB UL1699 drafted with national electrical manufacturers association by Underwriters Laboratories; mainly ac fault detection equipment quality testing standard is specified, and mandatory requirement AC system and civil buildings bedroom must install fault electric arc detect protective device protected.Last century, the nineties was the prosperous age of photovoltaic system, but easily there is the problems such as module, binding post and connection bus cases loosen in system, fault electric arc is caused to take place frequently, although these fault electric arc electric currents are very little, but the enough initiation fires of the energy generated, threaten the security of the lives and property in surrounding environment.The inefficacy of ac fault detection device GB and the extensive application of photovoltaic system make the detection isolating problem of photovoltaic DC fault electric arc increasingly serious, and the GB UL1699B that the U.S. formulated in 2011 formally proposes standard with regard to the DC Line Fault electric arc detecting device quality inspection problem of photovoltaic system.China also in propose in recent years about AFDD general designing requirement and it can be used as the draft proplsal of electric fire monitoring system, in visible photovoltaic system, the control of fault electric arc is extremely urgent.
At present, detect for photovoltaic system fault electric arc, the detection characteristic quantity threshold value researched and proposed both at home and abroad is all in normal table illumination external environment, working point and system charge based on system and does not change this prerequisite, does not relate to the situation that external environment change or accidental factor make illumination variation initiating system working point and system charge variation.And under improper illumination condition (rainy weather, black clouds is unbroken, improper illumination weather environment is stablized in leaf Long term Animal covering etc. and cirrocumulus is sailed, aircraft skims over, leaf is sailed, small bird flies over, sunrise sunsets etc. are in short-term under illumination variation environment), MPPT algorithm in inverter is dynamic adjustments photovoltaic system working point just, on the low side during the equal compared with normal of electricity of photovoltaic system, corresponding output characteristic curve and system charge also compared with normal time on the low side, now once the electric arc that breaks down, the characteristic quantity that the collection of DC Line Fault electric arc detecting device calculates often cannot reach setting threshold, the fault electric arc judging characteristic amount initial threshold set under making normal illumination lost efficacy, cause device tripping.This just causes photovoltaic system to there is larger potential arc fault threat, and the sustained combustion of this low current fault electric arc, also possesses enough energy and damage photovoltaic system, initiation fire, bring life and property loss.
Summary of the invention
The object of the invention is to solve DC Line Fault arc protection device former setting threshold under photovoltaic system enters improper illumination condition lost efficacy and the problem of the tripping of initiation, provide the photovoltaic system fault arc detection method under a kind of improper illumination condition.
For achieving the above object, present invention employs following technical scheme:
This fault arc detection method comprises the following steps:
When photovoltaic system does not break down arc event, based on the MPPT algorithm actuating signal identification photovoltaic system working point variation in inverter, based on the characteristic quantity threshold value judged for fault electric arc event in photovoltaic system working point variation adjusted in concert DC Line Fault electric arc detecting device, described characteristic quantity threshold value is made to present same variation tendency along with the change of the system charge in photovoltaic system working point.
Described fault arc detection method specifically comprises the following steps:
1) DC Line Fault electric arc detecting device carries out fault electric arc detection according to described characteristic quantity threshold value, and judges whether current sample time breaks down arc event, if break down arc event, then counting variable N counts, and then goes to step 3); If do not break down arc event, then reset counting variable N, go to step 2);
2) the whether action of MPPT algorithm in inverter is judged, if action, then judge that current sample time photovoltaic system enters improper illumination condition, DC Line Fault electric arc detecting device reads in the photovoltaic system working point after the variation of inverter output, calculate the described characteristic quantity threshold value set point corresponding when upper once fault electric arc detects in conjunction with the initial set value of described characteristic quantity threshold value and photovoltaic system working point corresponding to initial set value, then return step 1) carry out fault electric arc next time and detect; If not operating, then keep the current set value of described characteristic quantity threshold value constant, then return step 1) carry out fault electric arc detection next time;
3) whether failure judgement arc event recurs, if fault electric arc event recurs N
0secondary, N is accumulative reaches set point N
0, then judge to break down in photovoltaic system electric arc, take corresponding safeguard measure; If fault electric arc event does not recur N
0secondary, N is not accumulative reaches set point N
0, then step 1 is returned) continue to use the current set value of described characteristic quantity threshold value to carry out fault electric arc detection next time.
The frequency of described sampling is 10kHz ~ 100kHz, N
0span be 3 ~ 5.
Calculate in the set point of described characteristic quantity threshold value, corresponding to the initial set value of reflection characteristic quantity threshold value, the system charge of photovoltaic system working point and the photovoltaic system working point after changing should be consistent, and the change of the numerical value of this system charge is only changed by illumination condition and causes.
For the photovoltaic system formed according to remaining photovoltaic module after fault electric arc testing result excision fault photovoltaic block, should the photovoltaic system working point set point to described characteristic quantity threshold value corresponding according to described photovoltaic module carry out initialization, then according to step 1) to step 3) and proceed fault electric arc detect.
Described MPPT algorithm actuating signal obtains after communicating with inverter by DC Line Fault electric arc detecting device with the variation of photovoltaic system working point.
The present invention has technique effect useful as follows:
1) the method hardware implementing is simple, only need add the order wire between DC Line Fault electric arc detecting device and inverter in former photovoltaic system, and the working point in order to MPPT algorithm actuating signal and photovoltaic system dynamic conditioning is transmitted, with low cost;
2) the method is when fault electric arc causes photovoltaic system working point to change, and characteristic quantity threshold value remains unchanged, and has effectively stopped fault electric arc to this disturbing factor of system works point disturbance, enhances the reliability that fault electric arc detects under improper illumination condition;
3) the method also can accurate and effective detect for the fault electric arc betiding photovoltaic system under improper illumination condition, widen the scope of DC Line Fault electric arc detecting device identification of defective electric arc, make DC Line Fault arc protection device in any environment can action accurately and reliably, fault electric arc in timely cut-out photovoltaic system, fault electric arc potential under avoiding these situations threatens the life and property loss caused;
4) the method excises fault photovoltaic block in time after discovery fault electric arc, and according to new working point now, the DC Line Fault electric arc detecting device characteristic quantity threshold value of fault photovoltaic block place photovoltaic string and inverter end is re-established, make the still energy normal table work of all the other photovoltaic modulies, substantially prolongs the operating time of photovoltaic system under frequent non-illumination condition, add economic benefit.
Accompanying drawing explanation
Fig. 1 a is one of photovoltaic system fault arc detection method flow chart under improper illumination condition of the present invention;
Fig. 1 b is the photovoltaic system fault arc detection method flow chart two under improper illumination condition of the present invention;
Fig. 2 is that detection method of 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 is that detection method of 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 is that detection method of 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 block;
Fig. 5 a is that fine day is stablized normal illumination and transferred overcast and rainy this to and to stablize under improper illumination weather environment in inverter MPPT algorithm to the adjustment curve of photovoltaic system working point;
Fig. 5 b is that fine day is stablized normal illumination and transferred overcast and rainy this to and stablize the corresponding judging characteristic amount threshold curve that DC Line Fault electric arc detecting device real-time tracking photovoltaic system working point under improper illumination weather environment generates;
Fig. 5 c is that fine day is stablized normal illumination and transferred overcast and rainy this to and stablize photovoltaic system catastrophic failure electric arc curve after improper illumination weather environment;
Fig. 6 a be sunset this in short-term under illumination variation environment in inverter MPPT algorithm to the adjustment curve of photovoltaic system working point;
Fig. 6 b is this corresponding judging characteristic amount threshold curve that DC Line Fault electric arc detecting device real-time tracking photovoltaic system working point generates under illumination variation environment in short-term of sunset;
Fig. 7 a be cirrocumulus sail this in short-term under illumination variation environment in inverter MPPT algorithm to the adjustment curve of photovoltaic system working point;
Fig. 7 b is that cirrocumulus is sailed this corresponding judging characteristic amount threshold curve that DC Line Fault electric arc detecting device real-time tracking photovoltaic system working point generates under illumination variation environment in short-term;
Fig. 7 c is catastrophic failure electric arc curve after cirrocumulus is sailed.
In figure: 1, photovoltaic system; 2, DC Line Fault electric arc detecting device; 3, inverter; 30, inverter port; 31, inverter port; 4, order wire; 5, trip gear; 6, circuit breaker; 7, AC network; 8, electricity device is detected; 9, short switch; 10, photovoltaic module.
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 improper illumination condition: after the arc event that do not break down in confirmation photovoltaic system, carry out MPPT algorithm motion detection again, after action, just make the setting threshold in DC Line Fault electric arc detecting device dynamically follow the tracks of the change of working point.The system works point variation curve regulated by making failure judgement arc characteristic amount threshold value tight tracking MPPT algorithm, just can tackle illumination variation initiating failure arc-detection electricity dynamic change or continue the situations such as on the low side, ensure that checkout gear effectively can detect the fault electric arc in photovoltaic system at any time, the fault electric arc completed under improper illumination condition detects, and effectively eliminates the interference of fault electric arc to system works point.The present invention greatly improves the fault electric arc of photovoltaic system under the improper illumination condition caused by weather environment change etc. and detects prevention ability; compensate for conventional detection devices and the potential electric arc under improper illumination condition is threatened to the leak being difficult to detect, efficiently solve the tripping problem of photovoltaic fault arc protection device under above-mentioned improper illumination condition.
Composition graphs 1b, is specifically described the step of the photovoltaic system fault arc detection method under improper illumination condition of the present invention.
The initialization procedure of step one, fault arc detection method: comprise the clearing of inverter port reset, event of failure times N resets, and (residing for the photovoltaic system that initial characteristics amount threshold value is corresponding, normal illumination environment E be able to make whole system work in rated condition (P for clearing, typing photovoltaic system initial characteristics amount threshold value F and working point thereof, U), wherein, P=P
n, U=U
n, P
nfor rated power, U
nfor rated voltage) and the communication mode of order wire arrange.
Step 2, DC Line Fault electric arc detecting device are every certain sampling time T
1just the electric quantity signal of detection system, brings into characteristic quantity calculating formula and compares with setting characteristic quantity threshold value now, judging whether the arc event that breaks down.If break down arc event, be then designated as primary fault arc event, corresponding counts variable N counting adds one, turns to step 6; 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, turn to step 3.
Wherein, sampling time T
1less, sample frequency f
1higher, more accurate to the detection of fault electric arc event generation time, photovoltaic fault electric arc detection system is also higher to the sensitivity of fault electric arc, and combined with hardware design is considered, f
1generally be taken as 10kHz ~ 100kHz.
Step 3, confirmation system do not break down after arc event, and the order wire that detection inquiry is immediately connected between inverter and DC Line Fault electric arc detecting device is with or without MPPT actuating signal.
Photovoltaic system is once under entering improper illumination condition, and the illumination that photovoltaic module is subject to will change or enter another illumination stable state after dynamic change in short-term by compared with normal illumination dynamic continuance.Now photovoltaic system U-I output characteristic curve will change thereupon, U-I output characteristic curve during inevitable compared with normal illumination is low, U-I output characteristic curve after change and the system load characteristic curve intersection do not changed, determine new system works point, the MPPT algorithm of touching in inverter adjusts working point until system output power is maximum.Now, in inverter, MPPT algorithm action makes the transition of inverter port send high level signal, makes order wire transmit high level and keep, and exports the change curve of photovoltaic system working point from another port subsequently; If MPPT algorithm is failure to actuate in inverter, then inverter port exports as low level and keeps.
Step 4, DC Line Fault electric arc detecting device detect order wire signal transmission by inquiry and learn now MPPT algorithm whether action.If order wire is input as high level signal, then in judgement system, MPPT algorithm action is that light change causes suffered by photovoltaic block, and system works point changes, and now photovoltaic system is under improper illumination condition, turns to step 5; If order wire is input as low level signal, then judge that action does not occur the MPPT algorithm in inverter, photovoltaic system working point does not change, photovoltaic module is under continual and steady illumination condition and normally runs, keep former setting characteristic quantity threshold value constant, return step 2 and proceed the detection of next round fault electric arc.
Here improper illumination condition understands the change of initiating system working point usually, systems axiol-ogy electricity initial threshold inefficacy and the direct-current arc checkout gear of causing on the low side is caused to lose efficacy, mainly contain following situation: 1) photovoltaic system enters that rainy weather, black clouds are unbroken, leaf Long term Animal covering etc. stablizes improper illumination weather environment, the illumination that photovoltaic module is subject to enters new illumination stable state after will experiencing the dynamic change of very short time, photovoltaic system output characteristic curve changes to new state thereupon; 2) photovoltaic system runs into that cirrocumulus is sailed, aircraft skims over, leaf is sailed, small bird flies over etc. in short-term under illumination variation environment, the illumination that photovoltaic module is subject to returns to former normal illumination stable state after will experiencing the dynamic change of long period, photovoltaic system output characteristic curve changes to new state thereupon, after short stay, return to initial condition; 3) photovoltaic system enters sunrise sunset etc. in short-term under illumination variation environment, and the illumination that photovoltaic module is subject to will experience the lasting dynamic change of long period, and photovoltaic system output characteristic curve continues dynamic change to new state.
Step 5, confirmation system do not break down after arc event, inscribe the working point of MPPT algorithm dynamic conditioning and exported by port when inverter gathers this, and DC Line Fault electric arc detecting device waits for the new system works point of obtaining communication line transmission.Once after DC Line Fault electric arc detecting device reads in new system works point now, according to the specified photovoltaic system works point of initial setting characteristic quantity threshold value and correspondence thereof, calculate the new settings characteristic quantity threshold value of next time reading in the time period.The new threshold value after according to the adjustment of system works point is utilized to replace the set point of former threshold value as characteristic quantity criterion, return step 2 and proceed the detection of next round fault electric arc, realize the characteristic quantity threshold value under improper illumination condition thus and the dynamic realtime of system works point is followed the tracks of.
The inventive method proposes to carry out fault electric arc next time and inquires about MPPT algorithm whether action before detecting, so the order of accuarcy obtaining MPPT algorithm real action moment and photovoltaic system working point change moment all depends on the detection frequency of fault electric arc, namely system charge sample frequency f
1.
Step 6, 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
0, think that only having fault electric arc event to recur reaches N
0after 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
0then 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, extinguish fault electric arc, and give the alarm to supervisor in time, if remaining photovoltaic module still normally runs work after requiring excision fault photovoltaic block further, now the electricity of fault photovoltaic block place photovoltaic string and inverter end all changes, and should re-establish according to the new working point of current system to the characteristic quantity threshold value in these DC Line Fault electric arc detecting devices; If N < is N
0then 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, system works point and electric quantity change may be caused by fault electric arc, former setting threshold should be kept constant, return step 2 and proceed the detection of next round fault electric arc.
Wherein, fault electric arc event count variable threshold N
0larger, 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
0generally be taken as 3 ~ 5.
Composition graphs 2, sets forth application detection method of the present invention in the specific photovoltaic system comprising the DC Line Fault electric arc detecting device being integrated in inverter.
In Fig. 2, 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.
Under normal table illumination condition, do not break down electric arc time, corresponding inverter port 30 remains low level signal, can not export the change curve of photovoltaic system working point by trigger inverter 3, can't transmission system working point on order wire 4.Characteristic quantity threshold value now in DC Line Fault electric arc detecting device 2 remains unchanged, and calculating differentiation characteristic quantity, and comparing with original start characteristic quantity threshold value all the time, carrying out the fault electric arc testing process under normal lighting conditions by detecting electricity device 8.Once Judging fault arc event occurs, corresponding counts variable N adds 1, keeps the constant continuation fault electric arc of characteristic quantity threshold value to detect, effectively avoids new settings threshold value to be subject to the interference of fault electric arc.Only have when this counting variable reaches N
0, just judge to create fault electric arc in photovoltaic system, DC Line Fault electric arc detecting device 2 controls trip gear 5 cut-off breaker 6, extinguishes fault electric arc, and gives the alarm to supervisor in time; Otherwise clearing counting variable N gets rid of the accidentalia causing erroneous judgement, and proceeds to detect judgement.
And photovoltaic system experience cirrocumulus is sailed, aircraft skims over, leaf is sailed, sunrise sunset etc. in short-term illumination variation environment or experience suddenly that long rainy weather, black clouds are unbroken by normal illumination environment, leaf Long term Animal covering etc. stablize improper illumination weather environment time, before photovoltaic system illumination comparatively, state changes, the output characteristic curve of photovoltaic system changes, and the MPPT algorithm action in trigger inverter 3 starts to regulate photovoltaic system working point to maximum power point.Now, inverter port 30 keeps exporting high level signal, triggers DC Line Fault electric arc detecting device 2 read in the photovoltaic system working point change curve that another inverter port 31 exports through order wire 4.DC Line Fault electric arc detecting device 2 obtains photovoltaic system working point (P' now, U') after, according to photovoltaic system normal illumination working point (P, U) that former setting characteristic quantity threshold value F is corresponding, calculate the new settings characteristic quantity threshold value in next sampling time section
make the working point of setting threshold real-time tracking photovoltaic system change thus, constantly utilize the threshold value after new adjustment as characteristic quantity criterion, afterwards just with carrying out the judgement of fault electric arc event and starting the links such as protection under normal circumstances.After system enters overcast and rainy or sunset completely, the illumination that photovoltaic system accepts does not change, and now system works point also just no longer changes, and keeps Low threshold constant, and the detection electricity of tackling thus under improper illumination condition reduces situation.
What need additional description is, if DC Line Fault electric arc detecting device 2 to detect after fault electric arc only disengagement failure photovoltaic block but not whole photovoltaic system, so for ensureing that residue photovoltaic module still normally works, being integrated in threshold value in the DC Line Fault electric arc detecting device 2 of inverter needs to reinitialize according to now photovoltaic system output services point.
Composition graphs 3, sets forth application detection method of the present invention in the specific photovoltaic system comprising the fault arc detection device being integrated in photovoltaic string.
Suppose that the photovoltaic system in Fig. 3 comprises M photovoltaic string.Trip gear 5, the circuit breaker 6 of the detection electricity device 8 in comparison diagram 2, Fig. 3, DC Line Fault electric arc detecting device 2 and corresponding control thereof are distributed in each photovoltaic string but not inverter end.Therefore, the order wire 4 of this system on hardware also should be consistent with the number of DC Line Fault electric arc detecting device 2, is M.It is at normal illumination environment, in short-term illumination variation environment and under stablizing improper illumination weather environment, all consistent with photovoltaic system shown in Fig. 2 to the detection protection of fault electric arc.
Here be noted that under former normal illumination condition of work, the characteristic quantity threshold value in each DC Line Fault electric arc detecting device 2 sets for the photovoltaic string electricity at place, and working point under former normal illumination [(P, U), wherein, P=P
n, U=U
n] and the new working point of the photovoltaic system (P', U') that collects all or for whole photovoltaic system, so new settings threshold calculations formula is still
in addition, the electric arc once photovoltaic system breaks down, if only excise fault photovoltaic block but not the photovoltaic string at whole fault photovoltaic block place, so for ensureing that cause barrier photovoltaic string still normally works, being integrated in threshold value in the DC Line Fault electric arc detecting device 2 of syndrome serial needs to reinitialize according to now photovoltaic system output services point.
Composition graphs 4, sets forth application detection method of the present invention in the specific photovoltaic system comprising the DC Line Fault electric arc detecting device being integrated in photovoltaic block.
Suppose that the photovoltaic system in Fig. 4 comprises M photovoltaic string, each photovoltaic string comprises N number of photovoltaic module.Comparison diagram 2, the trip gear 5 of the detection electricity device 8 in Fig. 4, DC Line Fault electric arc detecting device 2 and corresponding control thereof, circuit breaker 6, short switch 9 are distributed in each photovoltaic block but not inverter end, and circuit breaker 6 is guaranteed only to excise fault photovoltaic block and do not affect other normal photovoltaic blocks and run together with short switch 9.Therefore, the order wire 4 of this system on hardware also should be consistent with the number of DC Line Fault electric arc detecting device 2, is M × N.In like manner, under former normal illumination condition of work, the characteristic quantity threshold value in each DC Line Fault electric arc detecting device 2 sets for the photovoltaic block electricity at place, and the new settings threshold value in next sampling time section is still
it is the sensitiveest that the photovoltaic system structure of application drawing 4 the input electricity choosing DC Line Fault arcing device 2 accept illumination variation as input point to photovoltaic system, but hardware drops into also relatively large.
Composition graphs 5, set forth fine day dash forward turn with rainy weather be representative stablize improper illumination weather environment under, the fault electric arc testing process that DC Line Fault electric arc detecting device tracking photovoltaic system working point dynamic adjustments happens suddenly under generating the process and these environment of reply differentiating characteristic quantity threshold value.
Fig. 5 a turns so that fine day is prominent for rainy weather, and describe that photovoltaic system enters rainy weather from normal table illumination weather environment, black clouds is unbroken, leaf blocks for a long time, Long term Animal stop etc. stablizes the photovoltaic system working point variation track of improper illumination weather environment.Fine day before can think 1 state residing for photovoltaic system, and its intensity of illumination corresponds to E
1(W/m
2), the output characteristic curve of photovoltaic system corresponds to L
1, system stability working point is A (P, U), and judging characteristic amount initial setting threshold value is F; Final rainy weather can think 2 states residing for photovoltaic system, and its intensity of illumination corresponds to E
2(W/m
2), the output characteristic curve of photovoltaic system corresponds to L
2, system stability working point is B (P', U').
Under being in fine day illumination before system, at t
1moment is prominent when meeting this quick Changes in weather overcast and rainy, after the change of a very short time is experienced in the illumination of photovoltaic system, at t
2moment enters a lower stable illumination conditions (2 state) immediately.Photovoltaic system enters above-mentioned these and stablizes improper illumination weather environment comparatively rapidly, so system is in L
1with L
2between Discrete Dynamic adjustment curve L
iless, corresponding new system works point (P'
i, U'
i) also less.Fig. 5 b is obtained according to new threshold setting method F'=P' × C (in the photovoltaic system of different structure, C value is different, but is fixed value for same photovoltaic system different operating point C).
Fig. 5 c illustrate photovoltaic system enter overcast and rainy after t
3moment breaks down, and detected electricity amplitude compared with normal light stable have dropped according in weather environment, and its decline degree depends on the minimizing degree stablizing the illumination of improper illumination weather environment.Therefore, the sampling electric quantity signal after decay brings characteristic quantity calculating formula income value into very likely lower than initial setting threshold value, causes device tripping to cause and detects inefficacy.But the judgment threshold in application drawing 5b, is equivalent to DC Line Fault electric arc detecting device and changes along with the change of external environment illumination the examination criteria of fault electric arc, make the input electric quantity change track of the accurate tracing and detecting apparatus of failure judgement electric arc standard.According to the requirement of the inventive method, there is moment t at fault electric arc in threshold value
3remain unchanged later, but not continue to follow the system works point on the low side caused by fault electric arc, as t in Fig. 5 b
3shown in dotted line after moment, effectively prevent the setting of characteristic quantity threshold value by fault electric arc to the interference of system charge, accurately detect the fault electric arc under each system works point thus.
The illumination variation in short-term such as cirrocumulus is sailed, aircraft skims over, leaf is sailed, small bird flies over, what photovoltaic system was with veil from normal table illumination weather environment stablizes improper this process of illumination weather environment with consistent described in Fig. 5, continue very short unlike this steady-state process of state 2 in Fig. 5 a, then experience of short duration Dynamic Regulating Process and once more return to this stabilization process of state 1.Therefore, break down in the masking process detection method of electric arc of photovoltaic system is similar with Fig. 5.
Composition graphs 6, set forth with sunset be representative the weather environment of illumination variation in short-term under, the fault electric arc testing process that DC Line Fault electric arc detecting device tracking photovoltaic system working point dynamic adjustments happens suddenly under generating the process and these environment of reply differentiating characteristic quantity threshold value.
Fig. 6 a, for sunset, describes photovoltaic system and slowly enters night (sunset) from normal table illumination weather environment or slowly enter the photovoltaic system working point variation track of the illumination variation weather environment in short-term such as normal table illumination weather environment (sunrise) from night.The fine day started can think 1 state residing for photovoltaic system, and its intensity of illumination corresponds to E
1(W/m
2), the output characteristic curve of photovoltaic system corresponds to L
1, system stability working point is A (P, U), and judging characteristic amount setting threshold is F; Final Critical Light is according to 2 states can thought residing for photovoltaic system, and its intensity of illumination corresponds to E
2(W/m
2), the output characteristic curve of photovoltaic system corresponds to L
2, system works point is B (P', U'), then along L
2adjustment working point is to C (0, U') [wherein, U' is the threshold voltage of inverter work].Now whole photovoltaic system has voltage to export and no current output, the open-circuit working point of correspondence system under Critical Light shines.
System gradually enters Critical Light photograph from fine day full exposure or shines from Critical Light and gradually enters full exposure, and the illumination of photovoltaic system need experience the gradual change of about a hour.Dynamic Regulating Process in these situations is slow, so the Discrete Dynamic regulating system working point selected by centre is more, still obtains Fig. 6 b by new threshold setting method.
When if fault betides this process, especially sunset closes to an end, detected electricity amplitude declines to a great extent, and must cause the tripping of DC Line Fault arc protection device, and the sustained combustion of small area analysis electric arc destroys photovoltaic module even initiation fire.So the judgment threshold of the multiple dynamic changes in application drawing 6b, corresponding to the multiple operating states between state 1 and state 2, effectively prevent the incipient fault electric arc under these environment.After state 2, threshold value is 0, and now photovoltaic system no current exports, and voltage is also minimum, thus can stop the detection to fault electric arc.It should be noted that, if employing voltage is the reflection characteristic quantity of the corresponding working point of initial threshold and current new working point here, then the reduction formula of new settings threshold value becomes
threshold value changes till system quits work (output current, voltage are 0) completely according to still following working point change afterwards at Critical Light.
Fig. 5 and Fig. 6 demonstrate the inventive method effectively can prevent improper illumination condition under photovoltaic system fault electric arc problem, ensure that photovoltaic system still can normally work under the common illumination condition such as overcast and rainy, sunrise sunset, take full advantage of the improper illumination of these weather environments thus, while extending whole photovoltaic system generating dutation, also add the generating capacity of system.
Composition graphs 7, set forth under skimming over as representative the weather environment of illumination variation in short-term with aircraft, DC Line Fault electric arc detecting device tracking photovoltaic system working point dynamic adjustments generates the fault electric arc testing process that the process that differentiates characteristic quantity threshold value and these environment of reply terminate rear burst.
Fig. 7 a sails for cirrocumulus, describes the photovoltaic system working point variation track of photovoltaic system from the normal table illumination weather environment illumination variation environment in short-term such as enter that cirrocumulus is sailed, aircraft skims over, leaf is sailed, small bird flies over.Described in front, the photovoltaic system environment in these situations to state 2, again returns to state 1 after staying for some time in state 1 quick adjustment.
Fig. 7 c describes the fault electric arc situation under a kind of improper illumination condition of very coincidence.Photovoltaic system is (t when this environment of illumination variation in short-term terminates to be about to return to normal illumination
3moment) system burst failure condition, normal illumination makes MPPT algorithm height-adjusting system working point, intrasystem sample detecting electricity amplitude raises, but series fault arc now occurs just makes sample detecting electricity decline, the energy that photovoltaic system increases by illumination strengthens all supplies fault electric arc just, make it be under state 2 always, be similar to cirrocumulus always in photovoltaic system upper end.And the initial threshold of current fault electric arc detection algorithm design can be hidden and thinks Changes in weather by mistake series fault arc, t namely can not be thought
1to t
2electricity variation is that fault electric arc causes, then because systems axiol-ogy electricity continues to remain unchanged, therefore at t
3the fault electric arc that moment occurs relies on original start threshold value to be detected.
By detection method, by the change judgment threshold in Fig. 7 b, make DC Line Fault electric arc detecting device threshold value at t
1moment continues to drop, and at t
3threshold value after keeping this to turn down after moment fault occurs is constant, and order fault electric arc is now detected.
The present invention is not when being caused by fault electric arc event in MPPT algorithm dynamic adjusting system working point, the system works point variation curve regulated by making failure judgement arc characteristic amount threshold value tight tracking MPPT algorithm, just can tackle illumination variation initiating failure arc-detection electricity dynamic change or continue the situations such as on the low side, ensureing that checkout gear effectively can detect the fault electric arc in photovoltaic system at any time.The inventive method compensate for the leak that fault electric arc detects protective device, improve the ability of DC Line Fault electric arc detecting device reply weather environment change, make DC Line Fault arc-detection protective device in any environment can action accurately and reliably, fault electric arc in timely cut-out photovoltaic system, the possibility of photovoltaic system breaking out of fire is in these cases reduced greatly, guarantee that photovoltaic system in any environment all can safe operation, life and property loss caused by the fault electric arc not easily detected under preventing these environment, conscientiously, ensured the security of the lives and property.It is all applicable that the inventive method carries out improper illumination detection for the photovoltaic system as usual run after the photovoltaic system of any integrated form of DC Line Fault electric arc detecting device, photovoltaic block of fixing a breakdown.
Claims (6)
1. the photovoltaic system fault arc detection method under improper illumination condition, is characterized in that: this fault arc detection method comprises the following steps:
When photovoltaic system does not break down arc event, based on the MPPT algorithm actuating signal identification photovoltaic system working point variation in inverter, based on the characteristic quantity threshold value judged for fault electric arc event in photovoltaic system working point variation adjusted in concert DC Line Fault electric arc detecting device, described characteristic quantity threshold value is made to present same variation tendency along with the change of the system charge in photovoltaic system working point.
2. the photovoltaic system fault arc detection method according to claim 1 under a kind of improper illumination condition, is characterized in that: described fault arc detection method specifically comprises the following steps:
1) DC Line Fault electric arc detecting device carries out fault electric arc detection according to described characteristic quantity threshold value, and judges whether current sample time breaks down arc event, if break down arc event, then counting variable N counts, and then goes to step 3); If do not break down arc event, then reset counting variable N, go to step 2);
2) the whether action of MPPT algorithm in inverter is judged, if action, then judge that current sample time photovoltaic system enters improper illumination condition, DC Line Fault electric arc detecting device reads in the photovoltaic system working point after the variation of inverter output, calculate the described characteristic quantity threshold value set point corresponding when upper once fault electric arc detects in conjunction with the initial set value of described characteristic quantity threshold value and photovoltaic system working point corresponding to initial set value, then return step 1) carry out fault electric arc next time and detect; If not operating, then keep the current set value of described characteristic quantity threshold value constant, then return step 1) carry out fault electric arc detection next time;
3) whether failure judgement arc event recurs, if fault electric arc event recurs N
0secondary, then judge to break down in photovoltaic system electric arc, take corresponding safeguard measure; If fault electric arc event does not recur N
0secondary, then return step 1) continue to use the current set value of described characteristic quantity threshold value to carry out fault electric arc detection next time.
3. the photovoltaic system fault arc detection method according to claim 2 under a kind of improper illumination condition, is characterized in that: the frequency of described sampling is 10kHz ~ 100kHz, N
0span be 3 ~ 5.
4. the photovoltaic system fault arc detection method according to claim 2 under a kind of improper illumination condition, it is characterized in that: calculate in the set point of described characteristic quantity threshold value, corresponding to the initial set value of reflection characteristic quantity threshold value, the system charge of photovoltaic system working point and the photovoltaic system working point after changing should be consistent, and the change of the numerical value of this system charge is only changed by illumination condition and causes.
5. the photovoltaic system fault arc detection method according to claim 2 under a kind of improper illumination condition, it is characterized in that: for the photovoltaic system formed according to remaining photovoltaic module after fault electric arc testing result excision fault photovoltaic block, should the photovoltaic system working point set point to described characteristic quantity threshold value corresponding according to described photovoltaic module carry out initialization, then according to step 1) to step 3) and proceed fault electric arc detect.
6. state the photovoltaic system fault arc detection method under a kind of improper illumination condition according to claim 1, it is characterized in that: described MPPT algorithm actuating signal obtains after communicating with inverter by DC Line Fault electric arc detecting device with the variation of photovoltaic system working point.
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| CN113437723A (en) * | 2021-07-06 | 2021-09-24 | 丰郅(上海)新能源科技有限公司 | Method for detecting fault arc |
| CN116660701A (en) * | 2023-07-31 | 2023-08-29 | 武汉新能源接入装备与技术研究院有限公司 | Arc detection method and system |
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