KR101810857B1 - Method of diagnosing potential induced degradation in photovoltaic module - Google Patents

Abstract

The present invention relates to a method for diagnosing a solar cell module in which a PID phenomenon occurs in which the output of the solar cell module decreases in accordance with a decrease in electrical characteristics of the cell. The diagnostic method according to the present invention includes the steps of: measuring the voltage output of the solar cell module under an environment with no irradiation dose; selecting a solar cell module to which a voltage resulting from the measurement of the voltage output is not output, . According to the present invention, when a PID phenomenon occurs in a solar cell module, the PID phenomenon can be distinguished from the cause of shading, snowfall, pollution and other causes without directly visual inspection, so that appropriate measures can be taken in a timely manner have.

Description

METHOD OF DIAGNOSING POTENTIAL INDUCED DEGRADATION IN PHOTOVOLTAIC MODULE In a solar cell module,

The present invention relates to a method of diagnosing a solar cell module, and more particularly, to a method of diagnosing a solar cell module in which a PID (Potential Induced Degradation) phenomenon occurs by measuring a voltage.

There are various reasons for the decrease in output of solar cells. It may be due to shading in the solar cell, or because the solar cell is blocked from the sunlight due to snowfall in winter. In addition, the surface of the solar cell may be contaminated with foreign matter such as various dusts and bird shots. In addition to these external factors, it may be caused by deterioration of the solar cell itself. In particular, PID (Potential Induced Degradation) phenomenon, which is a phenomenon of deterioration of electrical characteristics due to high voltage stress, can be caused even in a solar cell whose operating time is not long.

In solar cells, high voltage, high humidity, and high temperature can cause leakage current between solar cell and frame. This leakage current causes electrical charge (polarization), and polarizations interfere with the photoelectric effect of the solar cell, so that the characteristics of the solar cell deteriorate over time. As a result, the phenomenon that the total output of the module decreases with time is called PID.

Generally, in a photovoltaic power generation system, the potential of the solar cell frame becomes 0V, and the potential of the solar cell changes depending on the ground position (?) Or (+). At this time, electrons are emitted from the material used for the module due to the voltage between the solar cell and the frame, and the discharge is generated through the grounded frame, so that the output of the entire module is lowered.

In a solar cell module in which a PID phenomenon occurs, the amount of electricity produced is reduced, thereby reducing reliability and causing economic loss. Therefore, it is necessary to selectively recover and replace the solar cell module that generates the PID phenomenon, but it is difficult to visually judge whether the PID phenomenon occurs or not, and a method that can be remotely determined without depending on the method of photographing with special equipment It is hard to find at present.

A conventional technique for remotely selecting a solar cell module in which a problem occurs is disclosed in Patent Document 10 ?? 1051496 (Registered on Jul. 18, 2011). As shown in FIG. 1, this prior art attaches an end device having a sensor to a solar cell module, transmits sensing data to a central monitoring station through a wireless sensor network, The stored power generation amount is compared and analyzed to make it easy to find a degraded or faulty solar cell module. This prior art has an advantage in that it is possible to select a solar cell module in which an abnormality occurs without observing it with the naked eye.

However, as described above, the cause of the abnormality in the solar cell module may be many causes other than the PID phenomenon. Therefore, it is difficult to confirm the abnormal type of the specific solar cell module by the above-described conventional technology, There is a problem that can not be solved at all.

Patent Registration No. 10-1051496 (Registration date: 2011. 07. 18)

It is therefore an object of the present invention to provide a method of diagnosing a solar cell module capable of easily selecting a solar cell module in which a PID phenomenon occurs as monitoring data without visual confirmation .

In order to accomplish the above object, the present invention provides a method of selecting a solar cell module in which a PID phenomenon occurs in which the output of the solar cell module decreases in accordance with a decrease in electrical characteristics of the solar cell module, Measuring a voltage output of the solar cell module; and selecting the solar cell module to which the PID phenomenon has occurred, the solar cell module to which the measurement result voltage of the voltage output is not output.

Preferably, the voltage output is measured for each solar cell array in which a plurality of solar cell modules are electrically connected to one another. Further, the solar cell array connects solar cell arrays of a plurality of rows so as to be connected in parallel to one serial connection half, and connects an inverter into which the current outputted from the series connection half flows, to the serial connection half. In addition, the voltage output measurement of the solar cell module is carried out in the series connection panel or the inverter.

Preferably, the open-circuit voltage is measured for each solar cell array selected as the occurrence of the PID phenomenon in the sorting step, and a value obtained by subtracting the open-circuit voltage measurement value of the selected solar cell array from the open- Calculating a delta voltage of the photovoltaic array; determining whether the delta voltage value of any one of the selected photovoltaic arrays is smaller than a predetermined value for a predetermined period of time; And when the delta voltage value of any one of the solar cell arrays is measured to be greater than a certain ratio of a certain value for a predetermined time, the one of the solar cell arrays is classified as a solar cell array in which the PID phenomenon is generated . The method further includes restoring the solar cell array to a normal solar cell array by applying a reverse voltage to the solar cell array recognized as a solar cell module having a PID phenomenon. If the time point at which the open-circuit voltage is measured by irradiating sunlight to the selected solar cell module as the occurrence of the PID occurrence is delayed for a certain time or more than the open-circuit voltage measurement time at the normal solar cell module, The module further includes a step of recognizing that the PID generation phenomenon has occurred.

Advantageously, said specific value is a constant value between 30% and 60% of the open circuit voltage of a normal solar cell array, said predetermined time being at least 30 seconds. The predetermined time is between 5 minutes and 6 hours.

According to the diagnostic method of the PID generating solar cell module according to the present invention, when a PID phenomenon occurs in the solar cell module, the PID phenomenon can be distinguished from the cause of shading, snowfall, The timely, timely and appropriate action of the modules can save time, money and effort on maintenance of the photovoltaic system. Further, according to the present invention, it is possible to prevent further damage due to the long-term disposal of the PID phenomenon, thereby enhancing the durability of the solar power generation system.

1 is a block diagram showing a conventional technique.
Fig. 2 is a test photograph for artificial induction of PID phenomenon.
3 is a graph illustrating a power output reduction of a solar cell module due to the occurrence of a PID phenomenon.
4 is an electro luminescent (EL) image photograph before and after the PID phenomenon occurs.
5 is a graph showing current generation with time of a normal solar cell module and a PID generating solar cell module.
6 is a graph showing voltage output of a normal solar cell module and a PID generating solar cell module with respect to time in comparison with a solar radiation amount.
FIG. 7 is a graph showing the voltage output over time over several days by applying a larger time variable in the graph of FIG.
8 is a graph showing a difference between the open-circuit voltage of the normal solar cell module and the open-circuit voltage of the PID-generating solar cell module over time.
9 is an array configuration diagram for testing a solar cell module in an embodiment of the present invention.
10 is a flowchart showing a sorting method according to an embodiment of the present invention.

The specific structure or functional description presented in the embodiment of the present invention is merely illustrative for the purpose of illustrating an embodiment according to the concept of the present invention, and embodiments according to the concept of the present invention can be implemented in various forms. And should not be construed as limited to the embodiments described herein, but should be understood to include all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

In the present invention, in order to test the characteristics of a solar cell module in which a PID is generated, a PID phenomenon is artificially caused on a part of a normal solar cell to compare the electrical characteristics of a solar cell module having a PID phenomenon with a normal solar cell module Based on the results of several tests over a long period of time, a diagnostic method for the PID generating solar cell module was derived through comparison of the first hypothesis and data analysis according to the test.

The test method will be briefly described with reference to FIG. 2, and then a screening method according to the present invention will be described with reference to the drawings.

In the present invention, as shown in FIG. 2, in order to artificially generate a PID phenomenon in a normal solar cell module 1, a temperature of 85 degrees Celsius and a humidity of 85% are created and a direct current voltage of 1000 V is applied to the solar cell module frame, 24 hours have elapsed after application to the () terminal of the battery module. At this time, it is preferable to cause the PID phenomenon only in a part of the solar cell module 1 so that the efficiency of the experiment and the comparison with the normal module can be simplified. Therefore, the foil 2 is brought into contact with the edge portion of the solar cell module 1, and the voltage is applied only to the portion where the foil 2 is contacted.

FIG. 4 shows a comparative photograph of the PID-induced solar cell module and the normal solar cell module in the same manner as described above. The power output difference between the PID-induced solar cell module and the normal solar cell module is shown in FIG. Are shown in the graph.

As shown in FIG. 3, in the solar cell module in which the PID phenomenon occurs, the power output is reduced by 42.2% as compared with the normal solar cell module. Therefore, when the PID- It can be seen that damage may also occur to the module.

As a result of conducting a test for about 10 days for the field demonstration of the PID generating solar cell module and the normal solar cell module caused by the method shown in FIG. 2, the electrical characteristics over time are shown in the graphs of FIGS. 5 to 8 have.

For reference, 250W micro inverter was used in this test, and normal solar cell module and PID generated solar cell module were connected to grid system and operated.

The temperature, irradiation, and ambient temperature / humidity measurement sensors were installed on the back side of the normal solar cell module and the PID generated solar cell module, and the average data per 5 seconds was continuously stored for 7 days with 5 seconds as the unit time.

5 and 6 show the results of the daytime current generation test of the day with a good solar radiation amount.

FIG. 5 is a graph showing a comparison of a direct current generation amount of a normal solar cell module and a PID generating solar cell module with a solar radiation amount over time during a day. Here, an enlarged view at the start of the solar radiation is shown in the lower end of Fig. In the case of a solar cell installed at the same angle of incidence angle, when the solar radiation start time is examined in detail, in the case of a normal solar cell module, current is generated at the same time as the solar radiation starts. However, It can be seen that the current is generated from 18 to 20 minutes. This result provides an additional method of selecting a PID-generating solar cell module to be described later and will be described later.

6 is a graph comparing voltage characteristics of a PID-generating solar cell module and a normal solar cell module during a daytime.

In the morning and evening when the solar radiation is small in the daytime, the voltage output of the PID generating solar cell module differs from the normal solar cell module in the morning and the normal solar cell module also generates heat As a result, the voltage difference between the solar cell module and the PID generating solar cell module is smaller than that in the morning and evening.

FIG. 7 is a graph of voltage characteristics similar to FIG. Fig. 6 is a graph based on the irradiation amount during one day, whereas Fig. 7 is a graph recorded over nine days.

In FIG. 7, the high-rising part shows the weekly time zone, and the part near the bottom shows the night time zone. Particularly noteworthy is that the residual voltage is present in the normal solar cell module at nighttime, but the residual voltage is not measured in the PID generating solar cell module.

In FIG. 7, a portion between the raised portions, that is, a portion indicated by an elliptical circle is a portion indicating the residual voltage of the normal solar cell module. In Fig. 7, the voltage outputted from the normal solar cell module in the dark time period where there is no solar radiation at night or dawn is approximately 1 Vdc. At this time, more than 20Vdc voltage will be generated in commercial solar cell above 3kW class.

The diagnostic method of the PID generating solar cell module using the test results described above will be described.

A method of diagnosing a PID generating solar cell module according to the present invention is a method of diagnosing a PID generating solar cell module in which a voltage output of a solar cell module is measured under an environment where there is no irradiation dose, (Hereinafter, referred to as a 'residual voltage measuring step (I)'), which is recognized as being a PID generating solar cell array. That is, even in a dark situation such as a night time or early morning before sunrise, if the residual voltage is measured, it is recognized as a normal solar cell module, and when the residual voltage is 0, it is classified as a solar cell module in which a PID phenomenon occurs.

In this case, as shown in FIG. 9, the voltage output measurement is conveniently performed by arranging a plurality of solar cell modules 11 electrically connected to each other and measuring the solar cell arrays 10 formed of one row. In this case, the solar cell array 10 connects the plurality of solar cell arrays 10 in parallel so as to be connected to one serial connection unit 20, and one serial connection unit 20 is connected to the serial connection unit 20 And the inverters 30 to which the output current flows are connected one by one. Here, the voltage measurement sensor (not shown) for voltage measurement can be installed in the serial connection unit 20 or the inverter 30, so that it is possible to investigate whether or not the PID phenomenon of a plurality of solar battery modules occurs by using only the minimum voltage measurement sensor.

However, even in the case of the initially selected PID generating solar cell array in the residual voltage measuring step (I), normal solar cell arrays may be mixed. Additional screening procedures may therefore be required. The delta voltage can be used as a means for further screening. The delta voltage is a value obtained by subtracting the open-circuit voltage of the solar cell module from the open-circuit voltage of the normal solar cell module, which has been confirmed to have generated the PID phenomenon finally. That is, the delta voltage is the difference between the open-circuit voltage of the normal solar cell module and the open-circuit voltage of the solar cell module in which the PID is generated.

FIG. 8 is a graph showing a change in the delta voltage value over time. As shown in FIG. 8, the normal solar cell module and the solar cell module in which the PID is generated are different from each other at the time when the open-circuit voltage is generated. Min. By utilizing the characteristics of these delta voltages, a method for additional PID sorting can be provided.

First, the step (II) of measuring the delta voltage value of the first screening PID generating solar cell module in the residual voltage measuring step (I) for a predetermined period of time may be preceded. And the delta voltage value of the first selective PID generating solar cell array measured for a certain period of time in the step II continuously exceeds 30% of the specific value of the open voltage of the normal solar cell array 10 for 30 seconds or more The PID generating solar cell array is recognized to be a solar cell array in which a PID phenomenon has occurred (hereinafter, referred to as a secondary selection PID generating solar cell array), but if the delta voltage value Is smaller than an arbitrary specific value of 30% or more of the open-circuit voltage value of the normal solar cell array 10, step (III) in which the first selective PID generating solar cell array is recognized as a normal solar cell module is additionally set . Wherein the delta voltage of any particular value may be a constant value between 30% and 60% of the open circuit voltage of a normal solar cell array.

Meanwhile, the selection method according to the present invention includes a step (IV) of connecting the secondary selection PID generating solar cell array to a recovery system for applying a reverse voltage to the solar cell array and applying a reverse voltage to recover the normal secondary solar cell array .

Further, although not shown in FIG. 10, additional steps may be further set to more accurately determine whether a PID phenomenon has occurred. In this additional step, solar light is irradiated on the solar cell module selected in the step (I) for selecting the solar cell module in which the PID generation phenomenon has occurred, and the time when the open voltage is measured from the selected solar cell module is normal solar In the case where the open-circuit voltage of the battery module is delayed for a certain period of time or longer than the measurement time, the selected solar cell module is recognized as a solar cell module in which the PID generation phenomenon has occurred. At this time, the predetermined time may be several minutes in short time and 6 hours in long time. However, the V stage does not follow the IV stage in time, but may be a stage preceding the stage II or a stage performed after the stage III.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. It will be apparent to those of ordinary skill in the art.

1: solar cell module 2: foil
10: solar cell array 11: solar cell module
20: serial connection board 30: inverter

Claims (9)

1. A method for selecting a solar cell module in which a PID phenomenon occurs in which the output of the solar cell module is reduced due to deterioration of electrical characteristics of the cell,
Measuring a voltage output of the solar cell module under an environment where there is no solar radiation;
Selecting a solar cell module to which a voltage resulting from the measurement of the voltage output is not output as a solar cell module having a PID phenomenon; And
If the time point at which the open-circuit voltage is measured by irradiating sunlight to the solar cell module selected as the occurrence of the PID phenomenon is delayed for a certain time or more than the time of measuring the open-circuit voltage at the normal solar cell module, And recognizing that a phenomenon has occurred. The method for diagnosing a PID generating solar cell module according to claim 1,
The method according to claim 1,
Wherein the voltage output is measured by a plurality of solar cell arrays each comprising a single row, the plurality of solar cell modules being electrically connected to each other.
3. The method of claim 2,
Wherein the solar cell array connects a plurality of solar cell arrays in parallel so as to be connected to one serial connection half and connects an inverter into which the current outputted from the series connection half flows to the serial connection half. Diagnostic method of solar cell module.
[Claim 4 is abandoned upon payment of the registration fee.] The method of claim 3,
Wherein the voltage output measurement of the solar cell module is performed in a serial connection panel or an inverter.
3. The method of claim 2,
The open voltage is measured for each selected solar cell array in which the PID phenomenon has occurred in the sorting step and the delta voltage which is a value obtained by subtracting the open-circuit voltage measurement value of the selected solar cell array from the open- , ≪ / RTI &
Wherein when the delta voltage value of any of the selected solar cell arrays is measured to be smaller than a certain value for a predetermined time, the one of the solar cell arrays is classified as a normal solar cell array, If the value of the delta voltage of the array is measured to be larger than a certain ratio of a certain specific value for a predetermined time, the step of sorting the one solar cell array as a solar cell array in which the PID phenomenon has occurred
Wherein the method further comprises the steps of:
[Claim 6 is abandoned due to the registration fee.] 6. The method of claim 5,
Wherein the specific value is a constant value between 30% and 60% of the open circuit voltage of a normal solar cell array, and the predetermined time is at least 30 seconds.
6. The method of claim 5,
And recovering the normal solar cell array by applying a reverse voltage to the solar cell array recognized as a solar cell module having a PID phenomenon.
delete [Claim 9 is abandoned upon payment of registration fee.] The method according to claim 1,
Wherein the predetermined time is between 5 minutes and 6 hours.

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