JP2023152514A - Soundness diagnosis system and method for photovoltaic power generation device - Google Patents

Abstract

To provide a soundness diagnosis system capable of easily and accurately diagnosing soundness of strings of a photovoltaic power generation device.SOLUTION: In a soundness diagnosis system for a photovoltaic power generation device in which (m) ((m) is a natural number equal to or greater than 2) strings are connected in parallel, a total current value I is acquired by totaling a current value in of an n-th (1≤n≤m) string in the strings and current values from working strings in installed strings. Next, a current contribution index kn=N(in/I) (N is a constant which is set in such a manner that a value of kn in normal power generation of the device is normalized to 1 and corresponds to the number of working strings) and in a case where kn satisfies kn≥R (wherein R is a value selected from a range of 0.50 to 0.90), it is determined that the n-th string is sound.SELECTED DRAWING: Figure 2

Description

The present invention relates to a system and method for diagnosing the health of a solar power generation device that can easily and accurately diagnose the health of a solar cell string in the solar power generation device.

2. Description of the Related Art Photovoltaic power generation devices in which a large number of solar panels are arranged in order to effectively utilize solar energy have already become quite popular. There are various types of solar power generation devices, from small-scale devices installed on the roofs of homes to large-scale devices that can generate more than 1 megawatt, enough to cover local electricity.

In a large-scale solar power generation device, multiple solar cell modules are connected in series to form a solar cell string, and multiple solar cell strings are further connected in parallel and sent to the power conditioner of the solar power generation device. The power conditioner performs power conversion, etc., and becomes the final power output.

In solar power generation equipment, in addition to component defects and aging due to long-term use, solar power generation equipment may fail due to various factors such as damage caused by lightning in various parts, formation of shadows due to plant growth, and adhesion of flying objects. A decrease in the battery's current value (power generation amount) often occurs. Therefore, in order to confirm whether the solar power generation device is maintained in good health, health diagnosis of the performance and operation of each solar cell module or string is periodically performed.

As part of the above periodic health diagnosis, conventionally, the IV curve of the solar cell string was measured by connecting it at the junction box, and the presence or absence of abnormality in the shape of the IV curve, abnormality in open voltage, and abnormality in short circuit current was determined. I was diagnosing gender.

However, the conventional diagnostic method using IV curve measurement has to be performed comprehensively on a huge number of solar cell strings, and can only be performed at the site where the solar cell strings are installed. Furthermore, conventional diagnostic methods are limited to weather conditions and time zones suitable for IV curve measurement, and it is necessary to disconnect the string or junction box from the power generation system each time measurement is performed. As described above, conventional diagnostic methods have a large room for improvement in terms of labor and time required for testing.

JP2015-68690A JP 2017-60307 Publication JP2020-28192A

The present invention was devised in view of the current state of the prior art, and its purpose is to provide a health diagnostic system that can easily and accurately diagnose the health of each solar cell string that constitutes a solar power generation device. and to provide a method.

As a result of intensive studies to achieve such an objective, the present inventor has determined that the current value generated by each of a plurality of solar cell strings connected in parallel and under the same voltage condition is determined by solar radiation intensity, ambient temperature, etc. Although the current value may fluctuate over time even during the day due to the influence of the fluctuation factors of It has been found that the ratio of the current value of each individual solar cell string to the summed total current value is basically always constant. Then, instead of conventional IV curve measurement, a specific current contribution index is calculated for the current value of each solar cell string so that the standard value during normal power generation of the device is normalized to 1, and this current contribution Even if the index deviates from 1 due to mismatch in conditions between solar cell strings, the health of each solar cell string is determined by whether it is within an acceptable range, that is, whether it is at least a certain lower limit value. The inventors have discovered that the health of a solar power generation device can be easily and accurately diagnosed by doing so, and have completed the present invention.

That is, the present invention has been made based on the above findings, and consists of the following (1) to (6).
(1) A health diagnosis system for a solar power generation device that collects current by connecting m solar cell strings in parallel (m is a natural number of 2 or more),
The current value _i of the n-th solar cell string (n is a natural number selected from 1≦n≦m) among the solar cell strings, and the operating solar cell among the m solar cell strings. a data acquisition unit configured to acquire a total current value I that is the sum of current values from the string;
Based on the current value i _n acquired by the data acquisition unit and the total current value I, the current contribution index k _n =N (i _n /I) (however, N is the value of k _n when the device normally generates power is 1). It is a constant set to be normalized and corresponds to the number of solar cell strings in operation), and k _n is k _n ≧ R (where R is in the range of 0.50 to 0.90). and a data determination unit configured to determine that the n-th solar cell string is healthy when the formula (a value selected from ) is satisfied. Diagnostic system.
(2) The health diagnosis system for a solar power generation device according to (1), wherein R is a value selected from a range of 0.60 to 0.85.
(3) According to (1) or (2), the determination result of each solar cell string determined by the data determination unit is configured to be transmitted to a result display means in a remote location via Internet communication. Health diagnosis system for the solar power generation device described.
(4) A method for diagnosing the health of a solar power generation device that collects current by connecting m solar cell strings in parallel (m is a natural number of 2 or more),
The data acquisition unit obtains the current value i _n of the n-th solar cell string (n is a natural number selected from 1≦n≦m) and the operating solar cell among the m solar cell strings. a data acquisition step of acquiring a total current value I that is the sum of current values from the string;
Based on the acquired current value i _n and total current value I, the data judgment unit calculates the current contribution index k _n =N (i _n /I) (where N is the value of k _n when the device normally generates electricity). It is a _constant set to _be normalized to A method for diagnosing the health of a solar power generation device, the method comprising the step of determining that the n-th solar cell string is healthy if the formula (a value selected from a range) is satisfied.
(5) The method for diagnosing the health of a solar power generation device according to (4), wherein R is a value selected from a range of 0.60 to 0.85.
(6) The solar power generation device according to (4) or (5), characterized in that the determination result of each solar cell string determined in the health determination step is transmitted to a result display means in a remote location via Internet communication. health diagnosis method.

According to the system and method for diagnosing the health of a solar power generation device of the present invention, all the problems of the conventional diagnosis method using IV curve measurement can be solved while maintaining a simple and highly accurate diagnosis method. Furthermore, since the results of health diagnosis of the solar cell string can be obtained remotely without stopping power generation, it is possible to eliminate the difficulty of conventional regular inspections.

FIG. 1 shows an example of a solar power generation device that is a target of the health diagnosis system and method of the present invention. FIG. 2 shows a schematic diagram of an example of the health diagnosis system of the present invention. FIG. 3 shows a graph of an example of the diagnosis results performed in the health diagnosis system of the present invention.

Hereinafter, the solar power generation device health diagnosis system and method of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 shows an example of a solar power generation device that is subject to the health diagnosis of the present invention. For example, as shown in FIG. 1, a solar power generation device has a plurality of solar cell strings 102 in which a plurality of solar cell modules 101 are connected in series, and the plurality of solar cell strings 102 are connected in parallel. The energy is collected in a power conditioner 104 via a box 103. A plurality of such power conditioners 104 exist, and these plurality of power conditioners 104 are connected to constitute one power generation site. The generated power from the power generation site passes through the substation equipment 105 and is sold or used for its own use.

The system and method of the present invention can be used for everything from small-scale devices installed on the roofs of domestic residences to large-scale devices that generate power of 1 MW or more. It is particularly effective when used in a mega solar system with a power generation capacity of 1 megawatt or more, which requires a great deal of effort to inspect. In particular, in mega solar systems, it has traditionally been difficult to easily and accurately diagnose the health of each solar cell string containing a large number of solar cell modules. Below, the ratio between the current value of each solar cell string and the total current value, which is the sum of the current values from the installed solar cell strings that are in operation, is basically always constant. Based on this idea, the individual current contribution index of each solar cell string is calculated, and the health can be efficiently and accurately diagnosed based on whether the current contribution index deviates from the standard value within a certain range. can do.

In the solar power generation device targeted by the present invention, the number of modules per string is not particularly limited as long as it is plural, and the number of strings in the device is also not particularly limited as long as it is plural. In the solar power generation device targeted by the present invention, it is preferable that the number of modules per string is 3 to 100, and the number of strings in the device is 3 to 100,000. In the present invention, even if the individual solar cell strings used in the target solar power generation device have different structural types, they are connected in parallel and under the same voltage condition. There is no particular problem as long as the solar cell strings in the device are of the same structure type and under the same installation conditions in order to efficiently and accurately diagnose the health from the current value measurement data. It is preferable to perform a health diagnosis on a device installed under certain conditions (for example, under solar radiation conditions).

As mentioned above, even if multiple solar cell strings in a solar power generation device are connected in parallel and under the same voltage condition, the current value generated by each of the multiple solar cell strings depends on the solar radiation intensity, Although it may fluctuate over time during the day due to the influence of fluctuation factors such as ambient temperature, even if this is the case, the amount of energy generated from the solar cell strings that are installed and in operation. The ratio (i _n /I) of the current value i _n of each solar cell string to the total current value I, which is the sum of the current values, is basically always constant. As long as each solar cell string is generating power normally (in other words, is healthy), deviations from the standard value of this ratio are normal even if there are slight variations in the conditions between the solar cell strings. is within a certain range, the current contribution index k _n (=Ni _n /I) is calculated by normalizing the standard value during normal power generation of the device to 1, and the current contribution index k of each solar cell string is calculated. It has been found that by determining whether _n is within an appropriate range, the health of each solar cell string can be easily and accurately diagnosed.

Based on these findings, the present invention provides a system and method that can easily and accurately diagnose the health of a solar power generation device that collects electricity by connecting multiple solar cell strings in parallel. be. In the health diagnosis system of the present invention, the current value _in of each solar cell string in the solar power generation device and the current value from the solar cell strings that are in operation among the installed solar cell strings are summed. Based on the data acquisition unit configured to acquire the total current value I obtained by the data acquisition unit, and the individual current values and total current value I acquired by the data acquisition unit, the current contribution index of each solar cell string k _n =N (i _n /I) (N is a constant set so that the value of k _n during normal power generation of the device is normalized to 1, and corresponds to the number of solar cell strings in operation) and a data determination unit that calculates the current contribution index kn, checks whether this current contribution index _kn satisfies an appropriate range, and determines that a solar cell string that satisfies the range is healthy.

It is sufficient that the data acquisition section can measure the current value of each solar cell string temporarily, intermittently, or continuously, and it is preferable that the data acquisition section can at least temporarily store the measured data. Generally, since the data acquisition unit measures the current value of each solar cell string using a connection box or the like, it is preferably provided at or near the measurement site. The data acquisition unit not only collects measured data on the current value of each solar cell string, but also receives weather data such as ambient temperature from an air temperature sensor, solar radiation intensity from a pyranometer, power generation data from power conditioners, and electricity sales data from substation equipment. It may be possible to obtain it. Further, it is sufficient that the data determination section can determine whether the current contribution index of the present invention is within an appropriate range based on the data acquired by the data acquisition section, and it is sufficient that the data determination section can determine whether or not the current contribution index of the present invention is within an appropriate range. Good too. The data acquisition section and the data determination section are generally provided separately, but may be integrated at or near the measurement site. Furthermore, it is preferable that the diagnostic results of each solar cell string determined by the data determining section can be transmitted to a remote display, a smartphone, a personal computer, or other result display device via Internet communication. This allows the administrator to easily know the results of abnormality diagnosis from a remote location, even if the administrator is not at the site where the device is installed.

In the health diagnosis method of the present invention, as shown in FIG. In the device, the current value i _n of the nth solar cell string (n is a natural number selected from 1≦n≦m) among the m solar cell strings and the m solar cells installed. The data acquisition section acquires the total current value I, which is the sum of the current values from the solar cell strings that are in operation in the string, from a measuring device that measures it, for example, with a junction box, and then the n acquired by the data acquisition section. Based on the current value i _n of the th solar cell string and the total current value I from the operating solar cell strings, the current contribution index k _n (k _n =N(i _n /I), where N is the device The data judgment unit calculates the value of _kn (standard value) during normal power generation (this is a constant set so that it is normalized to 1, and corresponds to the number of solar cell strings in operation), The data determination unit determines that k _n is k _n ≧R (where R is 0.50 to 0.90, preferably 0.55 to 0.85, more preferably 0.60 to 0.85, even more preferably 0. 60 to 0.80), and if k _n satisfies this equation, it is determined that the n-th solar cell string is healthy. This determination can be made for all individual solar cell strings (all the natural number-th solar cell strings that n can take) of the solar power generation device.

Here, a method for calculating the current contribution index k _n will be shown below.
First, since the total current value I is the sum of the current values i _n of the individual solar cell strings, it can be written as follows.
I=i ₁ +i ₂ +…i _n +…+i _m
Further, the power generated by each solar cell string can be described as follows.
i _n V=P _n =α _n (T, V, S) S
However, V is the voltage of the solar cell string (common to all solar cell strings), P _n is the generated power of the nth solar cell string, and α _n (T, V, S) is the voltage of the nth solar cell string. is the power generation efficiency of the solar cell string, S is the solar radiation intensity, T is the ambient temperature, and the power generation efficiency is influenced by the solar radiation intensity S, the ambient temperature T, etc.

Next, the contribution rate of the current value of each solar cell string can be written as follows.
i _n /I=α _n /(α ₁ +α ₂ +…α _n +…+α _m )
Therefore, the current contribution index k _n of each solar cell string can be written as follows.
k _n =N(i _n /I)

However, N is a constant set so that the standard value of _kn (during normal power generation) is normalized to 1. Specifically, N is the number of solar cell strings in operation among the m installed solar cell strings, which corresponds to the number of solar cell strings contributing to the total current value I. do. Therefore, when all m installed solar cell strings contribute to the total current value I, N becomes m. In addition, if only some (plurality) of the m installed solar cell strings contribute to the total current value I due to reasons such as some solar cell strings not being able to generate electricity, N is (plural) of solar cell strings.

Assuming that the permissible variation rate of current values of individual solar cell strings is within the range of ±r, if each solar cell string is healthy, its current contribution index k _n is, for example, in the following range. It turns out.
(1-r)/(1+r)≦k _n ≦(1+r)/(1-r)
In the above formula, k _n defines the range of upper and lower limits, but in reality, there is no particular problem in exceeding the upper limit. Therefore, in reality, it is sufficient to judge the health of the solar cell string only based on whether k _n is equal to or greater than the above lower limit.
Then, (1-r)/(1+r)≦k _n
Considering the solar radiation intensity S and/or the ambient temperature T, etc., and setting the allowable variation ratio r in the range of 0.05 to 0.30, if r = 0.05, (1-r)/(1+r )≈0.90, and when r=0.30, (1−r)/(1+r)≈0.54.
Here, to simplify the equation, let (1-r)/(1+r)=R and let the lower limit of k _n be R, then the above equation can be expressed as k _n ≧ R, and R is 0. .54 to 0.90, and R is approximately 0.50 to 0.90.

The data determination unit determines that this k _n is k _n ≧R (where R is 0.50 to 0.90, preferably 0.55 to 0.85, more preferably 0.60 to 0.85, and even more preferably 0 The n-th solar cell string is determined to be healthy if the formula (a value selected from the range of .60 to 0.80) is satisfied, and if it is not satisfied, the n-th solar cell string is not healthy. It is determined that

The health diagnosis of individual solar cell strings as described above can be performed sequentially or simultaneously on all solar cell strings present in the apparatus. Further, this health diagnosis can be performed based not only on temporarily acquired data obtained from the data acquisition unit but also on intermittent acquired data or continuous acquired data over time. Further, the diagnosis results of each solar cell string determined in the above-mentioned health determination step are transmitted to result display means such as a smartphone or a personal computer via Internet communication.

There are two causes for a decrease in the current value (power generation amount) of a solar cell: temporary causes that can be ignored, and permanent causes that require repair or replacement. Temporary causes include sunlight hours, the presence of clouds, rain and other weather conditions, and shadows from buildings. Permanent causes include failures in parts such as solar cell modules, failures in measurement equipment and communication methods, Possible causes include bird droppings, nearby plant growth, flying objects, poor soldering/screw connections in devices, malfunctions in solar cell modules, salt fog, and poor contact due to moisture corrosion. These problems can be solved by continuously implementing the method for diagnosing the health of a solar power generation device of the present invention over time, or by performing the method for diagnosing the health of a solar power generation device of the present invention for a day By performing these tests continuously over time and at fixed times, it is possible to distinguish between temporary causes that can be ignored and permanent causes that require repair or replacement. can.

Next, FIG. 3 shows a graph of an example of the results of diagnosis performed using the health diagnosis system of the present invention for 12 solar cell strings. The vertical axis of the graph is the current contribution index k _n (where n=1 to 12), and the horizontal axis is time. Acquisition of current values by the data acquisition unit is performed continuously over time. Diagnosis results for 12 solar cell strings are shown in the graph. In the case of the graph of FIG. 3, the number of operating solar cell strings is 12, so N in the formula for the current contribution index k _n is 12. Moreover, the results of the graph shown in FIG. 3 can be displayed on a result display means located at a remote location from the solar power generation device.

As you can see from this graph, the sunrise time is after 7:05 in the morning, and the sunset time is after 17:35 in the evening, but from around 8:00 to around 12:35, the current contribution index k Since _n is approximately 1 for all solar cell strings, it is understood that all solar cell strings are healthy. From around 12:35 to around 15:00, the current contribution index k _n of two specific solar cell strings significantly decreased to less than 0.5, indicating that a healthy power generation state could not be maintained due to some factor. is understood. The current contribution index k _n of these two solar cell strings was approximately 1 before 12:35, indicating a healthy power generation state. This is thought to be because the solar radiation, which was uniform in all the solar cell strings, was no longer uniform after 12:35. For example, this is thought to be because as the position of the sun moves, two specific solar cell strings come under the shadow of a building, etc., and sunlight to the two specific solar cell strings is blocked. Note that from around 12:35 to around 15:00, the current contribution index k _n of the remaining solar cell strings other than the two specific solar cell strings is higher than 1; This is because two specific solar cell strings with decreasing _n were affected. From around 15:00 to around 17:35, the current contribution index k _n of almost all the solar cell strings fluctuates moment by moment. This is thought to be because the influence of shadows has reached almost all of the solar cell strings, and the influence of shadows is also fluctuating from moment to moment as the position of the sun moves. From the above analysis, from around 12:35 to around 15:00, the current contribution index k _n of two specific solar cell strings is less than 0.5, and a healthy power generation state cannot be maintained. , when considered comprehensively in conjunction with data from other time periods, the low current contribution index k _n of two specific solar cell strings from around 12:35 to around 15:00 can be ignored due to the influence of shadows. It is determined that the damage is due to a temporary cause that may require repair or replacement, and is not due to a permanent cause that requires repair or replacement. In this way, by continuously implementing the solar power generation device health diagnosis method of the present invention over time over a day, even from a remote location without the need to go to the site, it may be ignored. Health can be accurately diagnosed while distinguishing between temporary causes and permanent causes that require repair or replacement.

According to the present invention, the health of a solar cell string in a solar power generation device can be easily and accurately diagnosed, and is therefore extremely useful in the industry.

101 Solar cell module 102 Solar cell string 103 Connection box 104 Power conditioner 105 Substation equipment

Claims (6)

A health diagnosis system for a solar power generation device that collects current by connecting m solar cell strings in parallel (m is a natural number of 2 or more),
The current value _i of the n-th solar cell string (n is a natural number selected from 1≦n≦m) among the solar cell strings, and the operating solar cell among the m solar cell strings. a data acquisition unit configured to acquire a total current value I that is the sum of current values from the string;
Based on the current value i _n acquired by the data acquisition unit and the total current value I, the current contribution index k _n =N (i _n /I) (however, N is the value of k _n when the device normally generates power is 1). It is a constant set to be normalized and corresponds to the number of solar cell strings in operation), and k _n is k _n ≧ R (where R is in the range of 0.50 to 0.90). and a data determination unit configured to determine that the n-th solar cell string is healthy when the formula (a value selected from ) is satisfied. Diagnostic system. The health diagnostic system for a solar power generation device according to claim 1, wherein R is a value selected from a range of 0.60 to 0.85. Solar power generation according to claim 1 or 2, characterized in that the determination result of each solar cell string determined by the data determination section is configured to be transmitted to a result display means in a remote location via Internet communication. Equipment health diagnosis system. A method for diagnosing the health of a solar power generation device that collects current by connecting m solar cell strings in parallel (m is a natural number of 2 or more),
The data acquisition unit obtains the current value i _n of the n-th solar cell string (n is a natural number selected from 1≦n≦m) and the operating solar cell among the m solar cell strings. a data acquisition step of acquiring a total current value I that is the sum of current values from the string;
Based on the acquired current value i _n and total current value I, the data judgment unit calculates the current contribution index k _n =N (i _n /I) (where N is the value of k _n when the device normally generates electricity). It is a _constant set to _be normalized to A method for diagnosing the health of a solar power generation device, the method comprising the step of determining that the n-th solar cell string is healthy if the formula (a value selected from a range) is satisfied. The method for diagnosing the health of a solar power generation device according to claim 4, wherein R is a value selected from a range of 0.60 to 0.85. The method for diagnosing the health of a solar power generation device according to claim 4 or 5, characterized in that the determination result of each solar cell string determined in the health determination step is transmitted to result display means at a remote location via Internet communication. .