JP6408280B2 - Solar cell abnormality detection method and power management apparatus - Google Patents

Description

  The present invention relates to a solar cell abnormality detection method and a power management apparatus.

  In recent years, a demand for a photovoltaic power generation system which is one of renewable energies has increased, and a mega solar system exceeding 1 MW has been constructed. In such a large-scale system, when the system is stopped for some reason, the influence on the consumer is large. Therefore, it is desirable to detect and deal with when a small abnormality occurs. Therefore, introduction of a solar cell abnormality detection method with higher accuracy than before is required.

  For example, the conventional abnormality detection method of the photovoltaic power generation system acquires information such as the amount of power generation from the power conditioner, the power generation state, and an equipment error, and detects the abnormality of the photovoltaic power generation system based on the information. There is something to display. Although this method can detect a large abnormality such as a significant decrease in the amount of power generation or a failure of each device, it cannot find and deal with a small abnormality in a large-scale system. For this reason, there is a possibility that it is not possible to promptly perform repairs necessary to operate the system stably.

  In Patent Document 1, in addition to information such as power generation amount, power generation state, and error from a power conditioner, abnormality detection is performed by detecting abnormality by combining weather observation data such as solar radiation amount and temperature and time information. A system is disclosed. This system calculates a ratio between the theoretical power generation amount calculated based on the detected amount of solar radiation and the power generation amount measured by the power amount detector, and performs abnormality diagnosis based on the ratio.

JP 2011-216811 A

  In the solar light abnormality diagnosis system of Patent Document 1, abnormality diagnosis is performed based on the above-described ratio between the theoretical power generation amount and the measured power generation amount, but it is difficult to set a threshold value for determining the ratio. In order not to detect a normal state as an abnormality, the threshold value needs to be lowered to some extent, but this may cause a small abnormality to be overlooked. However, as described in the background art, in order to operate the system stably, it is necessary to detect and deal with small anomalies. For this purpose, it depends on the characteristics of the solar cell and the system. There was a problem of being forced to make detailed settings.

  The objective of this invention made | formed in view of this point is to provide the method of detecting the small abnormality of a solar power generation system correctly.

  In order to solve the above-mentioned problems, a solar cell abnormality detection method according to the present invention includes a step of obtaining a power value or a current value of output power from a solar cell, a step of obtaining a solar radiation amount, and the power value or current. A step of calculating a correlation coefficient between the value and the amount of solar radiation, and a step of determining that the solar cell is abnormal when the correlation coefficient is smaller than a predetermined threshold value.

  It is preferable that the method further includes a step of correcting the predetermined threshold in accordance with a change in the amount of solar radiation within a predetermined time.

The predetermined threshold value after the correction is an initial value Th _init of the predetermined threshold value, a correction coefficient K, and a real number N that satisfies 1 <N <3.
Th _init −K / (maximum solar radiation amount−minimum solar radiation amount) ^N
It is preferable to be represented by

  In order to solve the above problem, a power management device according to the present invention is a power management device for detecting an abnormality of a solar cell, and includes a power value or a current value of output power from the solar cell, and solar radiation. Obtaining a quantity, calculating a correlation coefficient between the power value or current value and the amount of solar radiation, and determining that the solar cell is abnormal when the correlation coefficient is smaller than a predetermined threshold value. Features.

  According to the solar cell abnormality detection method and the power management apparatus according to the present invention, it is possible to accurately detect a small abnormality of the photovoltaic power generation system.

1 is a block diagram of a photovoltaic power generation system including a power management apparatus according to an embodiment of the present invention. It is a figure which shows the abnormality determination flow by the power management apparatus which concerns on embodiment of this invention. It is a figure (Example 1) which shows the relationship between the solar radiation amount and a solar cell string electric current value. It is a figure (Example 2) which shows the relationship between solar radiation amount and a solar cell string electric current value. It is a figure (Example 3) which shows the relationship between solar radiation amount and a solar cell string electric current value. (Example 4) which shows the relationship between solar radiation amount and a solar cell string electric current value. It is a figure (Example 5) which shows the relationship between solar radiation amount and a solar cell string electric current value.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram of a photovoltaic power generation system including a power management apparatus according to an embodiment of the present invention. In FIG. 1, a thick solid line indicates a path through which electric power flows, and a thin broken line indicates a flow of a control signal or information to be communicated.

  A solar power generation system 100 illustrated in FIG. 1 includes a power management device 1, a solar cell 2, a power control device 3, a pyranometer 4, and a load 5.

  The power management device 1 is for detecting an abnormality of the solar cell 2 based on the generated power from the solar cell 2 and the solar radiation amount information from the solar radiation meter 4. The power management apparatus 1 may be configured by hardware, or a function may be realized by causing a CPU to execute a program. Details of the abnormality detection method will be described later.

  The power management apparatus 1 is connected to the power control apparatus 3, the pyranometer 4, and the like by, for example, a wired or wireless LAN (Local Area Network). The power management apparatus 1 can communicate with these devices using a predetermined communication protocol. For example, ECHONET Lite (registered trademark) can be used as the communication protocol. The power management apparatus 1 can acquire information on the operating state of other functional blocks through communication using ECHONET Lite, and can also control other functional blocks. Note that ECHONET Lite is merely an example, and other communication protocols may be used.

  The solar cell 2 converts sunlight energy into DC power. The solar battery 2 is configured such that, for example, power generation units having photoelectric conversion cells are connected in a matrix and output a current corresponding to the amount of incident light. The type of solar cell 2 is not limited as long as it is capable of photoelectric conversion, such as a silicon-based polycrystalline solar cell, a silicon-based single crystal solar cell, or a thin-film solar cell such as CIGS.

  The power control device 3 converts the power generated by the solar cell 2 and supplies it to the load 5. The power control device 3 includes a DC / DC converter for stepping up or stepping down direct current power while maintaining direct current, and an inverter for converting direct current power into 100V or 200V alternating current power. The power control device 3 communicates with the power management device 1 and transmits and receives various types of information related to the output current value and the operating state of the solar cell 2.

  The above DC / DC converter performs solar power generation by performing MPPT (Maximum Power Point Tracking) control on the generated power from the solar cell 2 and increasing or decreasing the voltage to a predetermined voltage. DC / DC converter suitable for the above.

  The pyranometer 4 measures solar radiation energy using a thermoelectric element or a photoelectric element and converts it into an electrical signal. In this embodiment, the solar radiation meter 4 can be a measuring instrument that can transmit the measurement result of the solar radiation amount to the power management apparatus 1 by wireless LAN, for example. Further, the current output of the pyranometer 4 may be directly connected to the power management apparatus 1 by wire, and the current measurement may be performed in the power management apparatus 1.

  The load 5 is a load that operates at a single-phase AC 100V or 200V used at home. Examples of the load 5 include household appliances such as a dryer, a home game machine or an audio system for listening to music, as well as electrical appliances such as a refrigerator, an emergency light, a hot water supply system or a home network server which should avoid power outages as much as possible. For example, load.

  In the present embodiment, the load 5 to be connected is assumed to be an electric device that can be used in Japan. However, the load can be appropriately changed in consideration of the use of an electric device that can be used outside of Japan. For example, it is possible to arrange an inverter capable of outputting AC 220 to 240 V so that electrical devices usable in Asia, Oceania, and Europe can be connected. In addition, since a three-phase three-wire 200V is often used for a commercial refrigerator, an air conditioner, or a motor drive in a factory, an inverter for converting to a three-phase 200V may be arranged.

  Next, a specific control example of the power management apparatus 1 according to the present embodiment will be described with reference to FIG.

  In FIG. 2, the power management apparatus 1 acquires the output current value of the solar cell 2 from the power control apparatus 3 (step S101). For example, the power control device 3 measures the current value from the solar cell 2 and the power management device 1 acquires the output current value of the solar cell 2 from the power control device 3 through communication such as ECHONET Lite. it can. Further, the power management device 1 may acquire the output current value from the solar cell 2 by direct communication.

  Moreover, the power management apparatus 1 acquires solar radiation amount information from the solar radiation meter 4 (step S102). The acquisition of the amount of solar radiation information is preferably performed at approximately the same time as the acquisition of the output current value of the solar cell 2 in step S101. In the present embodiment, the power management device 1 is configured to acquire the solar radiation amount from the solar radiation meter 4, but is not limited to this mode. For example, you may comprise so that the power management apparatus 1 may acquire the solar radiation amount information of the installation area of the solar cell 2 via the internet.

Next, the power management apparatus 1 has a correlation coefficient R between the solar radiation amount x _i (1 ≦ i ≦ n) acquired in steps S101 and S102 and the output current value y _i (1 ≦ i ≦ n) of the solar cell 2. Is calculated by the following formulas (1) to (4) (step S103).

  The power management apparatus 1 determines that the photovoltaic power generation system 100 is normal if the correlation coefficient R calculated in step S103 is equal to or greater than a predetermined threshold, and an abnormality occurs if the correlation is less than the predetermined threshold. It is determined that

Next, the power management apparatus 1 corrects the threshold value for determining whether or not the output power of the solar cell 2 is abnormal (step S104). In this embodiment, for example, when the change in the amount of solar radiation is small, such as during south-central time, the correlation between the amount of solar radiation and the output current value of the solar cell 2 is difficult to see. The number of relations tends to be calculated small. Therefore, when the change in the amount of solar radiation is small, correction is performed so that the threshold value becomes small. The corrected threshold Th _cor is calculated by the following formula (5) using, for example, a threshold initial value Th _init , a correction coefficient K, and a real number N satisfying 1 <N <3.

ここで、数式（５）における日射量最大値及び日射量最小値は、過去の所定時間内の日射量の最大値及び最小値である。

Here, the maximum amount of solar radiation and the minimum amount of solar radiation in Equation (5) are the maximum and minimum values of the amount of solar radiation within a predetermined past time.

  Note that the correction of the threshold value in step S104 may not be performed depending on the time zone to be determined.

  The power management apparatus 1 compares the correlation coefficient calculated in step 103 with the corrected threshold value calculated in step S104 (the threshold initial value when step S104 is not performed) (step S105). If the power management apparatus 1 determines that the correlation coefficient is smaller than the threshold value, it determines that an abnormality has occurred in the solar cell 2 (step S106). An indication that an abnormality has occurred in the battery 2 is performed.

  After performing the process associated with the abnormality determination in step S106 or when determining that the correlation coefficient is greater than or equal to the threshold value in step S105, the power management apparatus 1 ends the process.

  In addition, in this embodiment, although the power management apparatus 1 was comprised so that the output current value of the solar cell 2 might be acquired from the power control apparatus 3, it is not limited to this aspect. The power management apparatus 1 may obtain the output power value of the solar cell 2 and calculate a correlation coefficient with the amount of solar radiation.

  Thus, according to the present embodiment, the correlation coefficient is calculated based on the amount of solar radiation and the output current value or output power value from the solar battery 2, and the correlation coefficient calculation result and the predetermined threshold value are calculated. In comparison, the solar cell 2 is configured to detect an abnormality. Thereby, the setting of the threshold value for abnormality detection becomes easy, and it becomes unnecessary to perform detailed setting of the threshold value according to the characteristics of the solar cell 2.

  Moreover, in this embodiment, it comprised so that the threshold value for abnormality determination might be correct | amended according to the variation | change_quantity of the solar radiation amount in predetermined time. As a result, even if there is almost no change in the amount of solar radiation and the correlation coefficient is likely to decrease, the threshold value to be compared with the correlation coefficient is corrected so that an abnormality is not determined during normal operation.

Further, in the present embodiment, the predetermined threshold value is the threshold value initial value Th _init , the correction coefficient K, and a real number N satisfying 1 <N <3. Th _init −K / (maximum solar radiation amount−minimum solar radiation amount value) ^N
The threshold value is lowered according to the degree of the change in the amount of solar radiation. As a result, even when there is almost no change in the amount of solar radiation and the correlation coefficient tends to decrease, an abnormality determination is not made during normal operation.

  Finally, an example in which abnormality determination of the solar cell 2 is performed based on the output current value actually obtained from the solar cell 2 and the solar radiation amount information will be described.

Example 1
FIG. 3 shows an example in which abnormality determination is performed by acquiring the amount of solar radiation and the output current value from the solar cell 2 every 5 minutes from 9:30 am to 9:55 am on a certain day. In the first embodiment, the threshold value is not corrected in step S104 in FIG. FIG. 3A shows the result of acquisition of the amount of solar radiation and the output current value, and FIG. 3B is a graph of the result. As can be seen from FIG. 3B, the amount of solar radiation and the output current value have a substantially linear relationship, and the correlation coefficient between them is a very high value of 0.995. If the abnormality determination threshold is set to 0.5, the operation of the solar cell 2 is determined to be normal.

  The correlation coefficient is calculated based on the past six measurement values. The same applies to other embodiments described later. When the number of measurement data used for calculating the correlation coefficient is too large, it takes time for the occurrence of abnormality to be reflected in the fluctuation of the correlation coefficient. On the other hand, if the number of measurement data is too small, variations in correlation coefficients occur and the accuracy of abnormality detection is reduced. In this embodiment, measurement values for six times are used.

(Example 2)
FIG. 4 shows an example in which abnormality determination is performed by acquiring the amount of solar radiation and the output current value from the solar cell 2 every 5 minutes from 9:25 am to 10:05 on a certain day. In the second embodiment, the threshold value is not corrected in step S104 in FIG. Fig.4 (a) shows the acquisition result of solar radiation amount and an output electric current value, FIG.4 (b) graphs the result. As can be seen from FIG. 4B, the solar radiation amount and the output current value have a substantially linear relationship until a certain time (9:50), but thereafter, the solar radiation amount from the solar cell 2 with respect to the solar radiation amount. It can be seen that the output current value has decreased. The correlation coefficient between them is 0.995 at 9:50, which is a very high value, but decreases to 0.015 at 9:55. If the threshold for abnormality determination is set to 0.5, it is determined that an abnormality has occurred in the operation of the solar cell 2 at 9:55. Thus, by performing abnormality determination using the correlation coefficient, it is possible to detect the abnormality immediately after the abnormality has occurred.

  In the example of FIG. 4, the output current value from the solar cell 2 at 9:55 is about 90% of the normal value, and the decrease in the current value is only about 10%. In the conventional abnormality determination method, when the threshold for abnormality detection is set low, the example in FIG. 4 may not be determined as abnormal. In the present embodiment, since the correlation coefficient is calculated and the result is compared with a predetermined threshold, abnormality detection can be performed more accurately.

(Example 3)
FIG. 5 shows an example in which abnormality determination is performed by acquiring the solar radiation amount and the output current value from the solar cell 2 every 5 minutes from 12:05 PM to 12:30 PM on a certain day. In the third embodiment, the threshold value is not corrected in step S104 in FIG. Fig.5 (a) shows the acquisition result of solar radiation amount and an output electric current value, FIG.5 (b) graphs the result. As can be seen from FIG. 5 (b), there is almost no change in the amount of solar radiation in the above-mentioned time zone, and as a result, the correlation coefficient is 0.362, which is a very low value although there is no abnormality in the output of the solar cell 2. It has become. Therefore, if the abnormality determination threshold is set to 0.5, it is determined that an abnormality has occurred even though the operation of the solar cell 2 is operating normally.

Example 4
FIG. 6 is an embodiment in the case where the threshold value correction in step S104 in FIG. 2 is performed on the solar radiation amount in FIG. 5 and the output current value obtained from the solar cell 2. The correction conditions were K = 0.0002 and N = 2 in Equation (5). The threshold initial value is 0.5. In Example 3, since the change in the amount of solar radiation was small, the correlation coefficient was as low as 0.362, and it was determined to be abnormal because the threshold value was less than 0.5. However, in the fourth embodiment, the threshold value is corrected by applying the above condition to Equation (5). As a result, the corrected threshold value is −1.5, and correlation coefficient ≧ threshold value is satisfied. Is done.

(Example 5)
FIG. 7 shows an example in which the threshold value correction in step S104 of FIG. 2 is performed on the solar radiation amount of FIG. 4 and the output current value acquisition data from the solar cell 2. In the fifth embodiment, since the change in the amount of solar radiation is larger than that in the fourth embodiment, the difference between the threshold values before and after the correction is small, and the same determination result as in the second embodiment shown in FIG. 4 is obtained. As described above, when a certain change is observed in the amount of solar radiation, even if the threshold value is corrected in step S104, the correction amount of the threshold value is small, and thus the abnormality determination result is not greatly affected.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various changes or modifications based on the present disclosure. Therefore, it should be noted that these variations or modifications are included in the scope of the present invention. For example, the functions included in each component, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of components, steps, etc. can be combined into one or divided. It is.

DESCRIPTION OF SYMBOLS 1 Power management apparatus 2 Solar cell 3 Power control apparatus 4 Solar radiation meter 5 Load 100 Solar power generation system

Claims (4)

Obtaining a power value or a current value of output power from the solar cell;
A step of obtaining an amount of solar radiation;
Calculating a correlation coefficient between the power value or current value and the amount of solar radiation;
And a step of determining that the solar cell is abnormal when the correlation coefficient is smaller than a predetermined threshold value.   The solar cell abnormality detection method according to claim 1, further comprising a step of correcting the predetermined threshold in accordance with a change in the amount of solar radiation within a predetermined time. The predetermined threshold value after the correction is an initial value Th _init of the predetermined threshold value, a correction coefficient K, and a real number N that satisfies 1 <N <3.
Th _init −K / (maximum solar radiation amount−minimum solar radiation amount) ^N
The solar cell abnormality detection method according to claim 2, represented by: A power management device for detecting an abnormality in a solar cell,
Obtaining the power value or current value of the output power from the solar cell, and the amount of solar radiation,
Calculating a correlation coefficient between the power value or current value and the amount of solar radiation;
The power management apparatus, wherein the solar cell is determined to be abnormal when the correlation coefficient is smaller than a predetermined threshold value.

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