JP2014186022A - Method for diagnosing solar cell panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for diagnosing a solar cell panel, capable of quantitatively diagnosing a degree of the deterioration of a solar cell panel.SOLUTION: The method for diagnosing a solar cell panel comprises: connecting an impedance measuring device capable of sweeping a measurement frequency with the output terminal of the solar cell panel; measuring the frequency dependence of the impedance of the solar cell panel using the impedance measuring device; determining the equivalent circuit constant of the solar cell panel on the basis of a resonance frequency and resonance characteristics in the measured frequency dependence; and detecting a level of the deterioration of the solar cell panel by comparing the determined equivalent circuit constant with a value when the solar cell panel is normal.

Description

  The present invention relates to a solar cell panel diagnostic method.

  Solar power generation is highly expected as an alternative energy to thermal power generation and nuclear power generation. Crystalline solar cell panels using single crystal or polycrystalline silicon substrates and solar cells by depositing a thin film such as silicon on a glass substrate In recent years, the production of thin film solar cell panels that form the shape has increased dramatically. Currently, a solar power generation system in which a plurality of these solar panels are connected in series and parallel according to the purpose is used not only for general household power generation but also for large-scale power plants with a power generation of 1 MW or more. It has come to be.

  Solar cell panels have few mechanically operating parts and are generally said to have a lifetime of more than 20 years. In practice, however, many problems occur within a few years from the start of operation due to various causes. It has been reported. Deterioration of the power generation layer in the solar cell, increase in resistance due to corrosion of the electrode and wiring part, insulation deterioration of the sealing material filled between the solar cell and the metal frame, fixing the solar cell panel The characteristics of the solar cell panel may be deteriorated due to poor grounding of the metal pedestal or the like, which may eventually lead to malfunction. In order to further spread solar cells, there is a need for a diagnostic technique that can detect such a deterioration state of a solar cell panel at an early stage. If the deterioration state of the solar panel can be detected at an early stage, if some solar panels in the photovoltaic power generation system are deteriorated, if the solar panel is repaired or replaced at an appropriate timing, the solar panel It is possible to avoid the failure of the battery panel and the occurrence of the entire system. For this purpose, panel deterioration diagnosis and failure prediction technology are important.

  Since the amount of power generated by a solar panel varies greatly depending on external factors such as the amount of solar radiation and weather conditions at that time, whether the panel is operating normally only by monitoring the current / voltage and power generation amount of the solar panel. It is difficult to judge. In such power generation monitoring, so-called “0” / “1” determinations such as “operating” / “not operating” are possible, but the amount of solar radiation varies every moment. In an actual installation environment, it is difficult to determine whether an abnormality has occurred in the panel even if the power generation amount is reduced. In addition, when constructing a solar power generation system, it is difficult to determine on the spot whether the panel connection has a defect or the product itself has a problem when the construction is completed.

  In Patent Document 1, a roof steel plate on the back surface of a solar cell module is connected to a grounding electrode with a ground wire, an LCR meter is connected to a positive terminal and a grounding electrode of the solar cell module, and a static cell between the solar cell and the grounding electrode is connected. It is described that the capacitance is measured. Thus, according to Patent Document 1, when the connection from the solar cell module to the grounding electrode is not performed, the capacitance measurement value is significantly smaller than that when the connection is performed. It is said that it can be confirmed whether the module is connected to the grounding pole.

  Patent Document 2 describes that an input end of an LCR meter is connected to a terminal of a solar cell string in which a plurality of solar cell modules are connected in series, and the capacitance between the grounds is measured. Thus, according to Patent Document 2, the formula (number of solar cell modules up to the disconnection point) = (capacitance at the time of failure / capacitance at the time of soundness) × (number of solar cell modules in the solar cell string) Thus, it is said that the disconnection position between the solar cell modules can be easily specified.

Japanese Patent No. 3450701 Japanese Patent No. 4604250

  The techniques described in Patent Document 1 and Patent Document 2 are premised on measuring the capacitance between the output terminal of the solar cell panel and the ground (ground) using an LCR meter. For this reason, even if the technology described in Patent Document 1 and Patent Document 2 can detect a disconnection state between solar cell panels and a grounding failure with a frame to which the panel is attached or a frame of the solar cell panel, It is considered difficult to detect problems and problems of the solar battery panel itself such as deterioration of the power generation layer of the battery cell, poor resistance of the electrode / wiring part, and poor insulation of the solar battery cell.

  In addition, with the techniques described in Patent Document 1 and Patent Document 2, it is considered that the measurement of the capacitance itself is insufficiently accurate. For example, even if it is possible to determine the presence or absence of disconnection between the panels of the solar cell string, it is difficult to quantitatively detect the degree of deterioration in the middle of the disconnection.

  This invention is made | formed in view of the above, Comprising: It aims at obtaining the diagnostic method of the solar cell panel which can diagnose the deterioration degree of a solar cell panel quantitatively.

  In order to solve the above-described problems and achieve the object, a method for diagnosing a solar cell panel according to one aspect of the present invention includes connecting an impedance measuring instrument capable of sweeping a measurement frequency to an output terminal of the solar cell panel. Measuring the frequency dependence of the impedance of the solar cell panel using the impedance measuring instrument, and determining an equivalent circuit constant of the solar cell panel based on a resonance frequency and a resonance characteristic in the measured frequency dependence. The degree of deterioration of the solar cell panel is detected by comparing the value of the determined equivalent circuit constant with the value when the solar cell panel is normal.

  According to the present invention, an impedance measuring device capable of sweeping the measurement frequency is connected to the output terminal of the solar cell panel, and the frequency dependence of the impedance of the solar cell panel is measured using the impedance measuring device. Thereby, the resonance frequency and resonance characteristic in the frequency dependence of the measured impedance can be grasped. And the equivalent circuit constant of a solar cell panel is determined based on the grasped resonance frequency and resonance characteristic. For example, the solar cell panel is obtained by fitting the resonance frequency and resonance characteristic in the frequency dependence of the impedance obtained from the equivalent circuit model corresponding to the solar cell panel to the resonance frequency and resonance characteristic in the frequency dependence of the measured impedance. Can be determined. Then, the degree of deterioration of the solar cell panel is detected by comparing the determined value of the equivalent circuit constant with the value when the solar cell panel is normal. Thereby, while being able to grasp | ascertain the state of solar cell panel itself numerically and being able to compare numerically with the value when it is normal, the deterioration degree of a solar cell panel can be diagnosed quantitatively.

FIG. 1 is a schematic configuration diagram schematically illustrating a method for diagnosing deterioration / failure of a solar cell panel according to a first embodiment. 2 was measured using the deterioration and failure diagnosis method for a solar cell panel according to the first embodiment, is a diagram illustrating an example of a dependence on the intensity and phase of the frequency of the high frequency impedance Z _PV solar panel. FIG. 3 is a diagram showing a high-frequency equivalent circuit model of the solar cell panel in the first embodiment. FIG. 4 is a diagram illustrating an example of a result obtained by measuring the impedance of the solar cell panel using the method for diagnosing deterioration / failure of the solar cell panel according to the first embodiment and performing an equivalent circuit analysis. FIG. 5 is a diagram illustrating an example of a result of diagnosing the degree of deterioration of the solar cell panel using the method for diagnosing deterioration / failure of the solar cell panel according to the first embodiment. FIG. 6 is a diagram schematically illustrating a schematic configuration of a method for diagnosing deterioration / failure of a solar cell panel according to the second embodiment. FIG. 7 is a diagram schematically illustrating a schematic configuration of a method for diagnosing deterioration / failure of a solar cell panel according to the third embodiment. FIG. 8 is a diagram schematically illustrating a schematic configuration of a method for diagnosing deterioration / failure of a solar cell panel according to the fourth embodiment. FIG. 9 is a diagram schematically illustrating a schematic configuration of a method for diagnosing deterioration / failure of a solar cell panel according to a fifth embodiment. FIG. 10 is a diagram illustrating an example of the dependence of the high-frequency impedance _Ztotal of the entire measurement circuit on the strength and phase frequency evaluated using the method for diagnosing deterioration / failure of a solar cell panel according to the fifth embodiment. FIG. 11 is a diagram schematically illustrating a schematic configuration of a method for diagnosing deterioration / failure of a solar cell panel according to the sixth embodiment.

  Embodiments of a diagnostic method for a solar cell panel according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
A method for diagnosing a solar cell panel according to the first embodiment will be described.

  The solar cell panel to be diagnosed is, for example, a solar cell panel including a thin film or crystalline solar cell. The diagnosis target of the solar cell panel diagnosis method includes, for example, not only the failure of the solar cell panel but also the deterioration in the middle of the failure. The diagnosis target of the solar cell panel diagnosis method detects, for example, the degree of deterioration of the solar cell panel.

  Specifically, for example, as shown in FIG. 1, an impedance measuring device 15 is connected to the output terminal of the solar cell panel 11. 1 is a schematic diagram showing a method for diagnosing deterioration of a solar cell panel according to Embodiment 1. FIG.

  The solar cell panel 11 is a thin film solar cell panel, for example. In the solar cell panel 11, a photovoltaic cell is formed on a glass substrate 12 by laminating a power generation layer such as silicon, a transparent electrode film, and the like. The solar cell panel 11 is, for example, a frameless type in which a metal frame is not disposed around the solar cell panel 11. Further, an output terminal box 13 for taking out electric power is disposed on the back side of the solar cell panel 11.

  The central conductor 18 of the coaxial cable 17 connected to the measurement port 16 of the impedance measuring instrument 15 is connected to one terminal (positive electrode side) 13a of the output terminal box 13 for panel deterioration diagnosis. An outer conductor 19 of the coaxial cable 17 is connected to the other terminal (negative electrode side) 13 b of the output terminal box 13. In the coaxial cable 17, the outer conductor 19 is electrically insulated from the center conductor 18 via the dielectric 20.

  The impedance measuring instrument 15 has a function of substantially sweeping the measurement frequency and substantially sweeping the measurement frequency (for example, sweeping continuously or discretely sweeping at a predetermined interval (for example, a constant interval)). Have. The impedance measuring instrument 15 is, for example, a network analyzer, an impedance analyzer, a combination analyzer, or the like.

  Next, the impedance measurement of the solar cell panel 11 will be described in detail. Here, a method of measuring impedance by a one-port reflection method using a network analyzer as the impedance measuring device 15 will be described.

A weak high-frequency signal is sent from the measurement port 16 of the impedance measuring device 15 to the solar cell panel 11, and the power of the incident wave and the power of the reflected wave returning from the solar cell panel 11 to the impedance measuring device 15 are measured. . In the impedance measuring instrument 15, the reflection coefficient (intensity and phase) is obtained from the amplitude ratio between the incident wave and the reflected wave, and finally the impedance Z _PV of the solar cell panel 11 can be obtained. In this measurement, the frequency F of the high-frequency signal is swept within a certain range (F ₁ <F <F ₂ ) to obtain the frequency F dependence of the impedance Z _PV of the solar cell panel 11 (FIGS. 2A and 2B). )reference).

An example of the result of measuring the impedance Z _PV of the solar cell panel 11 using the diagnostic method shown in FIG. 1 is shown in FIG. 2A shows the dependence of the intensity of the impedance Z _PV on the frequency F, and FIG. 2B shows the dependence of the phase of the impedance Z _PV on the frequency F. FIG. 2 shows that this measurement is performed, for example, in the night zone (dark state) where the solar cells in the solar panel 11 do not generate power. For example, the lower limit frequency is set to F ₁ = 300 kHz and the upper limit frequency is set to F ₂ = 10 MHz. This is a result of measuring the impedance Z _PV of the solar cell panel 11 while increasing the frequency F from F ₁ to F ₂ .

When the frequency is gradually increased from F = 300 kHz, the intensity of the impedance Z _PV of the solar cell panel 11 shown in FIG. 2A first decreases, and after the frequency shows a minimum at F to 1.5 MHz, the frequency again It has increased. The frequency is F> 5 MHz, and the characteristics are almost flat. On the other hand, the phase of the impedance Z _PV shown in FIG. 2B is abruptly changing from −90 ° (capacitive load) to + 90 ° (inductive load) at a frequency of F to 1.5 MHz. . And the frequency is F> 2 MHz and shows a substantially flat characteristic.

As shown in FIGS. 2A and 2B, the frequency dependence of the impedance Z _PV of the solar cell panel 11 measured in this example shows resonance characteristics at F to 1.5 MHz, and the strength of Z _PV When the frequency when the phase is 0 ° and the phase is 0 ° (that is, the resonance frequency) is obtained, in this solar cell panel 11, the resonance frequency is F _res = 1.48 MHz. Moreover, the minimum value of the impedance was Z _PV = 7.3Ω (@ 1.48 MHz).

  Since the values of the resonance frequency and the minimum impedance are determined by the state of the solar cell panel, the state (for example, the degree of deterioration) of the solar cell panel can be grasped and managed by grasping these numerical values.

  Here, even if these numerical values (for example, the resonance frequency and the minimum value of the impedance) change, it is not directly known which part of the solar cell panel 11 has a problem. In order to identify the defective portion, the solar cell panel 11 may be replaced with an equivalent circuit. If the value of a specific element (for example, a series resistor) in the equivalent circuit changes, it can be considered that a problem has occurred at a location (electrode or wiring portion) corresponding to this element. Thus, it is effective to grasp and manage the equivalent circuit constant specific to the solar cell panel 11.

FIG. 3 shows an equivalent circuit model in the dark state of the solar cell panel 11 shown in FIG. Electrodes and wiring portions 11a of the solar cell panel 11 can be expressed by the series connection of the series resistor r _s and parasitic inductance L. Further, the solar cell portion (electrode / power generation layer / electrode) 11b has a series resistance r _s of the electrode portion and a shunt resistance R _sh of the power generation layer, and in the dark state without light irradiation, the pn junction portion of the power generation layer The junction capacitance _Cd can be used to represent a series-parallel circuit as shown in FIG. Therefore, it is considered that the total impedance Z _PV of the solar cell panel 11 viewed from the output terminal box 13 can be expressed by the following formula (1).

In Equation (1), ω represents an angular frequency (F = ω / (2π)), j represents a complex imaginary unit, and values of ω and circuit constants (L, R _sh , C _d ) are ωL−ωR _sh ^2. when satisfying the relationship _{C d / {1+ (ωR sh} C d) 2} = 0, the value of the imaginary part of _{Z PV} is zero, the intensity of the time _{Z PV} minimum phase becomes 0 °. That is, this is the resonance condition of the circuit, and when the values of L, R _sh , and C _d are given, the resonance frequency F _res can be obtained by the following equation (2).

When the frequency range is appropriately selected, the impedance Z _PV of the solar cell panel 11 exhibits resonance characteristics as shown in FIG. 2A, and the intensity of Z _PV greatly changes in the frequency region before and after the resonance frequency F _res. Therefore, the mathematical formulas (1) and (2) are fitted to the actually measured values in this region (see FIG. 4). As a result, the four circuit constants (r _s , R _sh , L, C _d ) that are the fitting parameters in the equations (1) and (2) can be obtained relatively easily.

It is not always necessary to use such resonance characteristics when fitting Equation (1), but it is desirable to perform fitting in a frequency region before and after the resonance frequency _Fres in order to improve fitting accuracy.

As a specific example, FIG. 4 shows the result of fitting in the frequency region from F = 300 kHz to 4 MHz as a region including the resonance frequency (F _res = 1.48 MHz) in FIG. Here, a circle is an actual measurement value of the impedance Z _PV , and a solid line is a result of fitting the mathematical formula (1). It can be seen that the measured values and the fitting results are relatively well matched. The values of equivalent circuit constants obtained by this fitting were series resistance r _s = 7.1Ω, parasitic inductance L = 2.8 μH, shunt resistance R _sh = 4.3 kΩ, and junction capacitance C _d = 4.0 nF. . In this way, the equivalent circuit constant of the solar cell panel can be obtained.

  In the present embodiment, a measurement method in which the measurement port 16 of the network analyzer is connected to the positive terminal 13a of the solar cell panel 11 is illustrated, but conversely, the negative electrode side terminal 13b of the solar cell panel 11 is connected. A measurement port 16 of the network analyzer may be connected, and a similar result is obtained.

  Next, the result of diagnosing the degree of deterioration of the solar cell panel 11 using the method for diagnosing the solar cell panel 11 shown in the present embodiment will be described. Here, a high temperature / high humidity test (temperature: + 85 ° C., humidity: 85% RH) was performed on one solar cell panel at different times, and the results of evaluating the power generation characteristics and high frequency characteristics of the panel after the test are illustrative. Explained.

The high-temperature and high-humidity test times were 1000 hours and 2000 hours, and the characteristics were evaluated three times in total including the initial values before the test. From the results of the high frequency characterization, the equivalent circuit constant of the solar cell panel _{(r s, R sh, L} , C d) were determined by the method measurement and analysis described in FIGS.

FIG. 5 shows changes in the equivalent circuit constants (L, r _s , C _d , R _sh ) and conversion efficiency (η) of a solar cell panel after a high temperature / high humidity test (1000 hours, 2000 hours). Is shown. Here, circuit constants and conversion efficiency values are normalized with initial values before testing. The initial value before the test is used as a value when the solar cell panel is normal. That is, normalizing circuit constants and conversion efficiency values with initial values before the test is equivalent to comparing circuit constants and conversion efficiency values with values when the solar panel 11 is normal. Equivalent to.

As shown in FIG. 5, the conversion efficiency η of the solar cell panel hardly changed in the high temperature / high humidity test for 1000 hours. However, for the circuit constant of the panel it is slightly reduced and the value of the junction capacitance C _d values and the shunt resistor R _sh of the power generation layer of the solar cell as compared with before the test. That is, in the high-temperature and high-humidity test for 1000 hours, almost no change is observed in the power generation characteristics of the solar cell panel, but it is recognized that slight degradation has occurred as early as possible in the power generation layer.

When the high-temperature and high-humidity test was continued on this solar cell panel, as shown in FIG. 5, the conversion efficiency η greatly decreased to 0.86 after 2000 hours. On the other hand, as for the circuit constant, while the series resistance r _s of the parasitic inductance L and the wiring and the electrode of the wiring does not change still little, junction capacitance C _d of the power generation layer is 0.87, the shunt resistance R _sh 0 To 91. From these results, it can be said that the degradation of the power generation layer caused a decrease in the conversion efficiency η. Also, Siri corresponding to the wiring or the electrode portion - because the value of's resistance r _s is constant, the high-temperature and high-humidity test up to 2000 hours, the corrosion of the metal can be said to not occurred.

Thus, before the conversion efficiency of the solar cell panel is decreased as early as from the fact that detects the Taker of C _d and R _sh, compared with the conventional power generation monitoring, the diagnostic method of the present embodiment It is concluded that the degree of deterioration of the solar cell panel can be diagnosed more sensitively and quantitatively.

For example, in FIG. 5, the equivalent circuit constants (L, r _s , C _d , R _sh ) and the conversion efficiency (η) are normalized with initial values (values when the solar cell panel 11 is normal). . Each of these normalized values corresponds to a comparison result with a value when the solar cell panel 11 is normal, and is also a value that quantitatively indicates the degree of deterioration.

Accordingly, for example, the solar cell panel 11 needs to be repaired or replaced by comparing the standardized values of the equivalent circuit constants (L, r _s , C _d , R _sh ) and the conversion efficiency (η) with the threshold values. It can be determined whether or not. For example, greater than the threshold THη for value conversion efficiency of the conversion efficiency (eta), the value of the parasitic inductance L is larger than the threshold value THL for parasitic inductance, Series -'s value of the resistor r _s is Siri - threshold for's resistance Even when larger than THr _s , the junction capacitance C _d becomes equal to or less than the junction capacitance threshold THC _d (first condition), and the shunt resistance R _sh becomes equal to or less than the shunt resistance threshold THR _sh (second). When at least one of the above conditions is satisfied, it can be determined that the solar cell panel needs to be repaired or replaced. Further, when it is determined that the solar panel 11 needs to be repaired or replaced, the user is prompted to repair or replace the solar panel 11 (for example, by a visual method such as message display or lamp lighting). Can be notified. In addition, when neither 1st conditions nor 2nd conditions are satisfy | filled, it can be judged that repair and replacement | exchange of the solar cell panel 11 are unnecessary. Thus, the degree of deterioration of the solar cell panel 11 can be quantitatively diagnosed.

Note that the rate of change between a plurality of times (for example, after 1000 hours and after 2000 hours) with respect to normalized values of equivalent circuit constants (L, r _s , C _d , R _sh ) and conversion efficiency (η) The failure time of the solar cell panel 11 can also be predicted by looking at the above. In this case, the predicted failure time can be notified to the user (for example, by a visual method such as message display or lamp lighting).

  Here, suppose a case where the characteristics of the solar cell panel 11 are measured using an impedance measuring instrument (for example, an LCR meter) whose measurement frequency is not sweepable. In this case, only the electrostatic capacitance between the solar cell panel 11 and the earth (ground) can be grasped, and it is difficult to quantitatively diagnose the degree of deterioration of the solar cell panel 11.

  On the other hand, in the first embodiment, the impedance measuring device 15 capable of sweeping the measurement frequency is connected to the output terminal of the solar cell panel 11, and the impedance dependence of the impedance of the solar cell panel 11 using the impedance measuring device 15. Measure. Thereby, the resonance frequency and resonance characteristic in the frequency dependence of the measured impedance can be grasped. And the equivalent circuit constant of the solar cell panel 11 is determined based on the grasped resonance frequency and resonance characteristic. For example, the solar cell panel 11 is obtained by fitting the resonance frequency and the resonance characteristic in the frequency dependence of the impedance corresponding to the circuit model corresponding to the equivalent circuit constant to the resonance frequency and the resonance characteristic in the frequency dependence of the measured impedance. Can be determined. Then, the degree of deterioration of the solar cell panel 11 is detected by comparing the determined value of the equivalent circuit constant with the value when the solar cell panel 11 is normal. Thereby, while being able to grasp | ascertain the state of solar cell panel itself numerically and being able to compare numerically with the value when it is normal, the deterioration degree of a solar cell panel can be diagnosed quantitatively.

  Moreover, in Embodiment 1, the slight degradation of the solar cell panel 11 can be detected by grasping and monitoring the equivalent circuit constant of the solar cell panel 11. Thereby, it is possible to prompt the user to repair or replace the solar cell panel 11 at an appropriate timing before failure occurs. Thereby, since it becomes possible to repair or replace the solar cell panel 11 before a serious failure occurs, there is an effect that the entire solar cell system including a plurality of the solar cell panels 11 can be efficiently maintained.

  In the first embodiment, a plurality of equivalent circuit constants of the solar cell panel 11 are determined based on the resonance frequency and the resonance characteristics in the frequency dependence of the measured impedance. Thereby, it is also possible to specify the deterioration location in the solar cell panel 11 by monitoring the change of the respective values of the plurality of equivalent circuit constants from when the solar cell panel 11 is normal.

  Moreover, in Embodiment 1, the measurement of the frequency dependence of the impedance of the solar cell panel 11 is performed at nighttime when the solar cell panel 11 is not generating power. Accordingly, since a circuit model corresponding to the equivalent circuit constant can be assumed with high accuracy, a plurality of equivalent circuit constants of the solar cell panel 11 can be accurately calculated based on the resonance frequency and the resonance characteristics in the frequency dependence of the measured impedance. Can be determined.

  In the first embodiment, the resonance characteristic used when determining the equivalent circuit constant includes a characteristic at a frequency higher than the resonance frequency and a characteristic at a frequency lower than the resonance frequency. As a result, the resonance frequency and the resonance characteristic in the frequency dependence of the impedance corresponding to the circuit model corresponding to the equivalent circuit constant can be accurately fitted to the resonance frequency and the resonance characteristic in the frequency dependence of the measured impedance. The accuracy in determining the equivalent circuit constant can be improved.

  In the first embodiment, the measurement of the frequency dependence of impedance is included in the range of the measurement frequency from 100 Hz to 10 MHz. For example, in measurement of frequency dependence of impedance, the measurement frequency is swept in a frequency range including a range of 300 Hz to 10 MHz. As a result, it is possible to measure the frequency dependence of the impedance while including a characteristic at a frequency higher than the resonance frequency in the frequency dependence of the impedance and a characteristic at a frequency lower than the resonance frequency. As a result, the resonance frequency and the resonance characteristic in the frequency dependence of the impedance corresponding to the circuit model corresponding to the equivalent circuit constant can be fitted to the resonance frequency and the resonance characteristic in the frequency dependence of the measured impedance with high accuracy. .

Embodiment 2. FIG.
Next, a solar cell panel diagnosis method according to the second embodiment will be described. Below, it demonstrates focusing on a different part from Embodiment 1. FIG.

  In Embodiment 1, since the measurement port 16 of the impedance measuring instrument 15 is directly connected to the output terminal box 13 of the solar cell panel 11 as shown in FIG. When light is incident on the light receiving surface of the panel 11, the solar cell panel 11 generates power, and a DC voltage of, for example, about several tens of volts may be applied to the measurement port 16 of the impedance measuring device 15. For this reason, in the actual environment installed outdoors, even if it is a measurement at nighttime, it is connected to the solar cell panel 11 in consideration of the case where external light accidentally hits the solar cell panel 11. The impedance measuring instrument 15 may break down.

  Therefore, in the second embodiment, as shown in FIG. 6, a blocking capacitor 21 is inserted between the output terminal box 13 (positive terminal 13 a) of the solar cell panel 11 and the impedance measuring device 15. As a result, the high-frequency signal for measurement supplied from the measurement port 16 to the solar cell panel 11 can easily pass through the blocking capacitor 21 and propagate to the solar cell panel 11 because the frequency is sufficiently high. However, the DC voltage / current generated in the solar cell panel 11 is cut by the blocking capacitor 21. As a result, failure of the impedance measuring instrument 15 due to overvoltage generated in the solar cell panel 11 can be prevented. The negative terminal 13b and the return node 22 of the solar panel 11 are electrically connected.

  Moreover, when diagnosing the solar cell panel 11-2 incorporated in the photovoltaic power generation system S including the plurality of solar cell panels 11-1 to 11-3, as shown in FIG. 15 and inserted between. Thereby, also in the daytime zone in which the solar cell panel 11-2 generates power, it is possible to suppress the direct current generated by the power generation from flowing into the impedance measuring device 15, and to protect the impedance measuring device 15.

  As described above, in the second embodiment, the frequency dependence of impedance is measured by inserting the blocking capacitor 21 between the output terminal box 13 (positive terminal 13a) of the solar cell panel 11 and the impedance measuring instrument 15. It is done in the state. Thereby, for example, when external light accidentally hits the solar cell panel 11 in the measurement at nighttime, it is possible to suppress the overvoltage generated in the solar cell panel 11 from flowing into the impedance measuring device 15. 11 can prevent a failure of the impedance measuring instrument 15 due to an overvoltage generated in the circuit 11.

  Moreover, in Embodiment 2, since the impedance measuring device 15 measures the frequency dependence of the impedance of the solar cell panel 11 via the blocking capacitor 21, the impedance measuring device 15 is disconnected from the solar cell panel 11 in a DC manner. Therefore, it is possible to measure even when the solar cell is generating power (that is, in a bright state). Thereby, circuit analysis for determining the equivalent circuit constant is easy.

Embodiment 3 FIG.
Next, a solar cell panel diagnosis method according to the third embodiment will be described. Below, it demonstrates centering on a different part from Embodiment 2. FIG.

  In the second embodiment, the terminal 13b on the negative electrode side of the solar cell panel 11-2 and the node 22 on the return side of the impedance measuring device 15 are not grounded, and the impedance measuring device 15 is in an electrically floating state. Yes. For this reason, when measuring the impedance when the solar cell panel 11 is generating power, it is necessary to pay attention to the fact that the DC voltage on the negative electrode side is applied to the node 22 on the return side of the impedance measuring instrument 15. .

  Therefore, in the third embodiment, in consideration of safety during measurement, as shown in FIG. 7, a blocking capacitor 23 is also provided between the node 22 on the return side of the coaxial cable 17 and the solar cell panel 11-2. insert. Further, the casing of the impedance measuring device 15 may be grounded via the ground wire 24. In addition, in the equivalent circuit when the solar battery panel 11 is generating power, the pn junction part of the power generation layer of the solar battery cell is not a capacitor but is short-circuited, and the valence circuit constant is determined. It is necessary to perform a circuit analysis for this purpose.

  As described above, in the third embodiment, the frequency dependency of the impedance is measured by inserting the blocking capacitor 21 between the terminal 13a on the positive electrode side of the solar cell panel 11 and the impedance measuring instrument 15, and the solar cell. This is performed with the blocking capacitor 23 inserted between the terminal 13 b on the negative electrode side of the panel 11 and the impedance measuring device 15 (the node 22 on the return side). Thereby, the safety | security at the time of a measurement can be improved.

Embodiment 4 FIG.
Next, a solar cell panel diagnosis method according to Embodiment 4 will be described. Below, it demonstrates focusing on a different part from Embodiment 1. FIG.

  In the first embodiment, a case where a network analyzer is used as the impedance measuring instrument 15 for measuring the impedance of the solar cell panel 11 is illustrated, but in the fourth embodiment, the frequency can be swept as shown in FIG. Is connected to the output terminal box 13 of the solar cell panel 11 (that is, each of the positive terminal 13a and the negative terminal 13b), and a current / voltage sensor 27 is disposed near the connection position. The high-frequency waveform of current / voltage may be observed using the waveform observation / calculation unit 25. That is, the high-frequency signal generator 26, the current / voltage sensor 27, and the waveform observation / calculation unit 25 can constitute an impedance measuring device 28 that can operate in the same manner as the impedance measuring device 15 (see FIG. 1).

For example, when the current / voltage amplitude (I ₀ , V ₀ ) and the phase difference (θ) are obtained from the observed waveform, the impedance Z _PV of the solar cell panel 11 can be obtained from the following equation (3).

In such a method of obtaining the impedance from the current / voltage measurement, it is not easy to accurately measure the phase difference θ between the current and the voltage when the frequency of the measurement signal is high. In this case, the impedance Z _PV It should be noted that errors are likely to be included in.

As described above, in the fourth embodiment, the frequency of the weak high-frequency signal applied to the solar cell panel 11 by the high-frequency signal generator 26 is swept, and the current / voltage of the incident wave and the current / voltage of the reflected wave are obtained. The current / voltage sensor 27 observes the synthesized current / voltage waveform, and the current / voltage amplitude (I ₀ , V ₀ ) and phase difference (θ) are obtained from the waveform observed by the waveform observation / calculation unit 25. Then, the impedance Z _PV of the solar cell panel 11 is obtained. Thereby, the impedance measuring device 28 equivalent to the impedance measuring device 15 whose measuring frequency can be swept can be connected to the output terminal of the solar cell panel 11, and the impedance dependence of the impedance of the solar cell panel 11 using the impedance measuring device 28. Can be measured.

Embodiment 5 FIG.
Next, a solar cell panel diagnosis method according to Embodiment 5 will be described. Below, it demonstrates focusing on a different part from Embodiment 1. FIG.

In the fifth embodiment, as shown in FIG. 9, an inductor 29 for adjusting the resonance point is provided in the measurement line between the output terminal box 13 (positive terminal 13 a) of the solar cell panel 11 and the impedance measuring instrument 15. insert. As a result, the impedance Z _total of the entire measurement circuit as viewed from the impedance measuring instrument 15 needs to consider the impedance of the resonance point adjusting inductor 29 in addition to the impedance Z _PV of the solar cell panel 11. Since an equivalent circuit of the resonance point adjusting inductor 29 is considered as a series circuit of an inductance component L _coil and a resistance component R _coil , the impedance Z _total of the entire measurement circuit is expressed by the following equation (4).

Further, the frequency at which the value of the imaginary part of Z _total becomes zero, that is, the resonance frequency F _res is obtained by the following equation (5).

Thus, the resonance characteristics of the entire measurement circuit are influenced by the resonance point adjusting inductor 29. An example is shown in FIG. 10A shows the dependence of the intensity of the impedance Z _total on the frequency F, and FIG. 10B shows the dependence of the phase of the impedance Z _total on the frequency F. Here, the circuit constants (C _d = 10 nF, R _sh = 10 kΩ, L = 0.2 μH, R _s = 1Ω) of the solar cell panel in Formula (4) are fixed, and the resistance of the inductor 29 for adjusting the resonance point Assuming that the component is zero (R _coil = 0), the value of the inductance component was changed in the range of L _coil = 0 to 4.8 μH, and the impedance Z _total was calculated.

As shown in FIG. 10, when no inductor is inserted in the measurement line, resonance occurs at a frequency of about 3.5 MHz. This is due to L (= 0.2 μH) and C _{d of the} solar cell panel. It is a series resonance by (= 10 nF). Next, when an inductor is inserted and the value of L _coil is increased to a maximum of 4.8 μH, the resonance frequency is greatly reduced from about 3.5 MHz to about 0.7 MHz. Thus, by selecting the value of L _coil of the inductor to be inserted, the resonance frequency can be adjusted in a wide range.

If the material / structure of the solar cell panel and the size of the panel are different, the circuit constants of the panel are different, and the resonance frequency is also different for each panel. Therefore, if various types of solar cell panels are to be diagnosed using the same impedance measuring device 15, the frequency sweep range needs to be sufficiently widened, which increases the cost of the impedance measuring device. On the other hand, when the inductor 29 for adjusting the resonance point is incorporated, if the value of L _coil is appropriately selected according to the type and size of the solar cell panel, almost all panels can be covered with the same impedance measuring instrument. it can.

If the value of L _coil is sufficiently large (for example, L _coil = several 10 to several hundreds μH), the resonance frequency can be lowered to a frequency band of F _res = several kHz to several 10 kHz. At such a low frequency, the impedance measurement becomes remarkably easy, and the cost of the impedance measuring instrument can be greatly reduced.

Further, as shown in FIG. 10, when the value of L _coil is large, the change in impedance near the resonance frequency becomes severe. In such a case, when the value of the resonance frequency is obtained from the graph or the equivalent circuit constant is obtained by curve fitting with the actual measurement data, the accuracy can be improved, which is very convenient.

Embodiment 6 FIG.
Next, a solar cell panel diagnosis method according to Embodiment 6 will be described. Below, it demonstrates focusing on a different part from Embodiment 1. FIG.

  In Embodiment 6, a method of diagnosing a specific solar cell panel in a string in which a plurality of solar cell panels are connected in series will be described with reference to FIG. As in the third embodiment, a blocking capacitor 21 is inserted between the output terminal box 13 (positive terminal 13 a) of the solar cell panel 11 and the impedance measuring device 15, and a node on the return side of the coaxial cable 17. A blocking capacitor 23 is also inserted between 22 and the solar cell panel 11. The high-frequency signal for measurement supplied from the impedance measuring device 15 to the solar cell panel 11 has a sufficiently high frequency (in other words, because the capacitance of the capacitor is sufficiently large), the blocking capacitor 21 is easily provided. Although it can pass and propagate to the solar cell panel 11, the DC voltage / current generated in the solar cell panel 11 is cut by the blocking capacitors 21 and 23. As a result, failure of the impedance measuring instrument 15 due to overvoltage generated in the solar cell panel 11 can be prevented. Further, since the node 22 on the return side of the coaxial cable 17 is also electrically disconnected by the blocking capacitor 23, the casing of the impedance measuring instrument 15 can be grounded via the ground wire 24 to prevent electric shock. .

  Further, as shown in FIG. 11, an interference preventing diode 30 is inserted for each panel at a connection portion between adjacent solar cell panels in the string. In the nighttime when impedance is measured, since the solar cell panel does not generate power, no voltage is generated at both ends of the diode 30, and the diode 30 is turned off. Therefore, the high frequency signal supplied from the impedance measuring instrument 15 to the specific solar cell panel 11 cannot propagate to other panels adjacent to this panel, and as a result, only the solar cell panel to be measured Impedance measurement is possible. On the other hand, during the daytime when the solar cell panel is generating power, a voltage is generated at both ends of the diode 30, so that the diode 30 is turned on and all the solar cell panels in the string are electrically connected. . In addition, if the impedance measurement of a solar cell panel is performed in such a state, it will also be influenced by other than the panel to be measured (particularly the panels on both sides), making measurement difficult.

  As described above, in the sixth embodiment, in a solar cell string in which a plurality of solar cell panels are connected in series, a diode is inserted between adjacent panels. These diodes are turned off, and each panel is electrically disconnected. Thereby, in the impedance measurement of a solar cell panel, interference from other solar cell panels can be prevented.

  Furthermore, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention in the implementation stage. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent requirements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the above embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and is described in the column of the effect of the invention. In the case where a certain effect can be obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention. Furthermore, the constituent elements over different embodiments may be appropriately combined.

  As described above, the method for diagnosing a solar cell panel according to the present invention is useful for diagnosing degradation or failure of a solar cell panel.

  11 Solar panel, 12 Glass substrate, 13 Output terminal box, 15, 28 Impedance measuring device, 16 Measurement port, 17 Coaxial cable, 18 Center conductor, 19 Outer conductor, 20 Dielectric, 21, 23 Blocking capacitor, 22 Return side Node, 24 ground wire, 25 waveform observation / calculation unit, 26 high frequency signal generator, 27 current / voltage sensor, 29 inductor for adjusting resonance point, 30 interference preventing diode, 31 connector.

Claims (7)

Connect an impedance measuring instrument that can sweep the measurement frequency to the output terminal of the solar panel,
Measure the frequency dependence of the impedance of the solar cell panel using the impedance measuring instrument,
Based on the resonance frequency and resonance characteristics in the measured frequency dependence, determine an equivalent circuit constant of the solar cell panel,
A method for diagnosing a solar cell panel, comprising comparing a value of the determined equivalent circuit constant with a value when the solar cell panel is normal to detect a degree of deterioration of the solar cell panel . The method for diagnosing a solar cell panel according to claim 1, wherein the measurement is performed at nighttime when the solar cell panel is not generating power. The solar cell panel diagnosis method according to claim 1 or 2, wherein the measurement is performed in a state where a blocking capacitor is inserted between an output terminal of the solar cell panel and the impedance measuring instrument. 4. The measurement according to claim 1, wherein the measurement is performed in a state in which an inductor for adjusting a resonance point is inserted between an output terminal of the solar cell panel and the impedance measuring instrument. 5. Diagnostic method for solar cell panels. The diagnosis of the solar cell panel according to any one of claims 1 to 4, wherein the resonance characteristic includes a characteristic at a frequency higher than the resonance frequency and a characteristic at a frequency lower than the resonance frequency. Method. In the said measurement, a measurement frequency is contained in the range of 100 Hz or more and 10 MHz or less. The diagnostic method of the solar cell panel of any one of Claim 1 to 5 characterized by the above-mentioned. An impedance measuring instrument capable of sweeping the measurement frequency is connected to the output terminal of one solar cell panel in a solar cell string in which a plurality of solar cell panels are connected in series or in parallel.
Frequency dependence of impedance of the solar cell panel using the impedance measuring instrument in a state where an interference preventing diode is inserted between two adjacent solar cell panels directly connected to the solar cell panel Measuring sex
Based on the resonance frequency and resonance characteristics in the measured frequency dependence, determine an equivalent circuit constant of the solar cell panel,
A method for diagnosing a solar cell panel, comprising comparing a value of the determined equivalent circuit constant with a value when the solar cell panel is normal to detect a degree of deterioration of the solar cell panel .

Images