JP2014165232A - Photovoltaic power generation module and photovoltaic power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photovoltaic power generation module in which the degree of deterioration of a solar cell panel can be detected, and the panel can be repaired or replaced before reaching a critical failure.SOLUTION: A photovoltaic power generation module includes an output terminal box for taking out the power generation output of a solar cell panel, a backflow prevention diode inserted into the output line of the output terminal box, and an impedance measurement device of the solar cell panel. The impedance measurement device includes a signal generation unit for superimposing a micro signal of variable frequency to the output line, a high frequency signal detection unit provided in the output line and detecting a high frequency signal, and an impedance calculation unit for calculating the high frequency characteristics of impedance of the solar cell panel from the high frequency signal thus detected.

Description

  The present invention relates to a solar power generation module capable of performing deterioration detection and failure diagnosis of a solar battery panel, and a solar power generation system using the solar power generation module.

  Solar power generation is highly expected as an alternative energy to thermal power generation and nuclear power generation, and the production amount of solar cells in recent years has increased dramatically. Solar cells include crystalline solar cells that form solar cells using single-crystal or polycrystalline silicon substrates, and thin-film solar cells that form solar cells by depositing a thin film such as silicon on a glass substrate. It is used. The installation unit of the solar cell in the solar power generation system is a solar power generation module. A solar panel is a panel formed by connecting a plurality of the above-mentioned solar cells in series and parallel according to the purpose. A solar panel is provided with an outer frame (frame) or a connection box. Functions as a module. A photovoltaic power generation system is configured by combining a number of photovoltaic power generation modules installed on a gantry, power transmission cables, power conditioners, and the like. Such a system is used not only in general household power generation applications but also in large-scale solar power plants having a power generation amount of 1 MW or more.

Solar cell panels have no mechanically operating parts and are generally said to have a lifetime of more than 20 years. However, in reality, there have been cases where malfunctions have occurred within a few years from the start of operation due to various causes. It has been reported. The causes of the failure are deterioration of the power generation layer in the solar battery cell, increase in resistance due to corrosion of the electrode and wiring part, insulation deterioration of the sealing material filled between the solar battery cell and the metal frame, solar battery panel There is a known grounding failure of a metal frame that fixes
Due to these problems, the characteristics of the solar cell panel may be deteriorated, which may eventually lead to malfunction. In order to increase the reliability of solar power generation and further promote the spread, there is a need for a diagnostic technique that can detect such a deterioration state of the solar cell panel at an early stage.

  At present, as a method for confirming the operation state of the solar cell panel, it is common to monitor the power generation amount of each panel. Also, as a diagnostic method for detecting the presence or absence of solar panel connection failure, attach the solar cell panel output terminal and a metal frame or panel on the outer periphery of the panel that is electrically grounded. A method of diagnosing the grounding state of a solar cell panel by measuring the capacitance between the metal base and the measured value with an LCR meter and comparing the measured capacitance value with the normal panel value. It is known (see, for example, Patent Document 1).

  Further, in the case of a solar cell string in which a plurality of solar cell panels are connected in series, the number of panels is changed, and the capacitance between the output terminal of the string and the ground is measured in advance to create a database. It is shown that it is possible to detect which panel is disconnected (for example, see Patent Document 2).

JP-A-11-248879 JP 2008-91828 A

  If some of the PV modules in the PV system fail, there may be a problem that affects the entire system. It is ideal to repair or replace the solar power generation module or solar battery panel at an appropriate timing. For that purpose, deterioration diagnosis technology and failure prediction technology for individual solar cell panels are necessary.

  However, because the amount of power generated by the solar panel varies greatly depending on external factors such as the amount of solar radiation and weather conditions at that time, simply monitoring the current, voltage, and amount of power generated by the solar panel will cause the panel to operate normally. It is difficult to judge whether or not. In such power generation monitoring, so-called “0” / “1” determinations such as “operating” / “not operating” of the panel are possible, but the amount of solar radiation changes every moment. In an actual installation environment, it is difficult to determine whether or not an abnormality has occurred in the solar cell panel in a situation where the power generation amount is decreasing. Moreover, even when constructing a solar power generation system, it is difficult to determine on the site whether or not there is a problem with the panel connection or whether the product itself has a problem when the construction is completed.

  Moreover, in the conventional diagnostic method based on the measurement of electrostatic capacity, since the electrostatic capacity between the output terminal of the solar battery panel and the ground is measured using an LCR meter, the disconnection situation between the solar battery panels or the panel is attached. Although it is possible to detect a grounding failure with the frame of the pedestal or panel, there is a problem with the solar panel itself such as deterioration of the power generation layer of the solar cell, resistance failure of the electrode / wiring section, cell insulation failure, etc. The problem could not be detected. In addition, the capacitance measurement itself is not accurate enough, and it was possible to determine the presence or absence of disconnection between the panels of the solar cell string, but quantitatively detected the degree of deterioration during the disconnection. It was difficult. Furthermore, in the measurement work, it was necessary to carry the LCR meter, which is a measuring instrument, to the place where the solar cell panel is installed, and to measure the capacitance for each panel.

  This invention was made in order to solve the above problems, and provides a photovoltaic power generation module capable of quantitatively detecting the location and degree of degradation of a solar cell panel by a simple method. In addition, in a photovoltaic power generation system using this module, information for accurately grasping the failure of each photovoltaic power generation module is collected, and maintenance of the photovoltaic power generation module is efficiently performed, thereby generating power. It is an object to obtain a photovoltaic power generation system that can be stably maintained.

  The photovoltaic power generation module of the present invention includes an output terminal box for extracting the power generation output of the solar cell panel through the output line, and the output terminal box measures the backflow prevention diode inserted into the output line and the impedance of the solar cell panel. The impedance measuring device includes a signal generating unit that superimposes a high-frequency signal having a variable frequency on the output line, a signal detecting unit that is provided on the output line and detects the high-frequency signal, and a signal detecting unit. And an impedance calculating unit that calculates high-frequency characteristics of the impedance of the solar cell panel from the detected high-frequency signal.

  According to the present invention, by obtaining a high frequency impedance characteristic for each solar cell panel with a simple device and monitoring the equivalent circuit constant with high accuracy, it is possible to detect the degree of deterioration of the solar cell panel, resulting in a serious failure. It is possible to repair or replace the panel before it arrives. Thereby, the effect that maintenance of the whole photovoltaic power generation system can be performed efficiently is acquired.

It is a schematic block diagram which shows the solar energy power generation module of Embodiment 1 of this invention. It is a block diagram of the high frequency impedance measuring apparatus of Embodiment 1 of this invention. It is a circuit block diagram of the high frequency impedance measuring apparatus of Embodiment 1 of this invention. It is an example of the high frequency voltage and electric current waveform in the output terminal of the solar cell panel obtained with the high frequency impedance measuring apparatus of Embodiment 1 of this invention. 1 is a circuit diagram of a high-frequency voltage / current detection sensor of a high-frequency impedance measuring apparatus according to Embodiment 1 of the present invention. It is a graph which shows the example of the high frequency characteristic of the impedance of the solar cell panel obtained with the high frequency impedance measuring apparatus of Embodiment 1 of this invention. It is a figure which shows the high frequency equivalent circuit model of the solar cell panel in Embodiment 1 of this invention. It is a figure which shows the example of the result of having performed the impedance characteristic of the solar cell panel of Embodiment 1 of this invention, and an equivalent circuit analysis. It is a graph which shows the example of the high frequency characteristic of the impedance obtained with the high frequency impedance measuring apparatus of Embodiment 2 of this invention. It is a figure which shows the signal waveform of the high frequency impedance measuring apparatus of Embodiment 3 of this invention. It is a figure which shows the structure of the solar energy power generation system of Embodiment 4 of this invention. It is a figure which shows the structure of the photovoltaic power generation module back surface of Embodiment 4 of this invention.

Hereinafter, a solar power generation module according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to the specific examples described in these embodiments.
Embodiment 1 FIG.
1 is a perspective view showing a schematic configuration of a photovoltaic power generation module GM according to Embodiment 1. FIG. FIG. 1 shows a state where the light receiving surface is facing down and the back surface is facing up. The solar cell panel 1 is a thin film solar cell having a structure in which, for example, a power generation layer such as silicon or a transparent electrode film is laminated on a glass substrate to form a solar cell, and the back surface is sealed with a backsheet, laminated glass, or the like. It is. On the back surface side of the solar cell panel 1, a tab wire T that is a conductive path for taking out the power generation output is stretched and connected to an output terminal box 2 arranged on the solar cell panel 1. Furthermore, it is configured to extract DC power from the output terminal box 2 through the output line 3. A frame AF made of an aluminum alloy is attached to the outer periphery of the solar cell panel 1 in order to protect the end.

FIG. 2 is a configuration diagram of the high-frequency impedance measuring device MD connected to the output of the solar cell panel according to the first embodiment. The structure of the apparatus which measures the high frequency characteristic provided in the output terminal box 2, and performs a calculation is shown.
An output power transmission line connected to the power generation layer of the solar battery cell via the tab line T is connected to the output terminal box 2 and is taken out as an output line 3 that outputs the generated DC power. The output line 3 is provided with a high-frequency signal generator 25 that feeds power by superimposing a high-frequency signal of a minute voltage, and a high-frequency voltage / current detector 24 that detects voltage / current from the output line. The high-frequency signal generator 25 has a function of continuously changing the frequency, and the frequency of the high-frequency signal is variable. The position where the high-frequency signal generator 25 and the high-frequency voltage / current detector 24 are provided in the output line 3 is closer to the solar cell panel than the reverse current prevention diode 26 inserted into the output line 3 (not including the backflow prevention diode 26). ). That is, a high frequency signal is superimposed on the output line 3 between the backflow prevention diode 26 and the solar cell panel 1.
When a power generation system is configured using a plurality of photovoltaic power generation modules GM, the reverse current prevention diode 26 causes an excessive current to flow from another panel when one of the modules breaks down and becomes short-circuited. This is to prevent burning.

  The high frequency voltage and current data detected from the output line is converted into high frequency characteristic data of impedance by the impedance calculation unit 23, passes through the control unit 21, and from the data communication unit 22 via the external host computer HC and the communication means 28. Sent and received.

Further, the output line 3 is provided with a power supply unit 27 that stores a part of the power generated by the solar cell panel and supplies power to each of the blocks. (The power supply line from the power supply unit 27 is not shown.)
FIG. 3 is a circuit configuration diagram of the high-frequency impedance measuring device MD connected to the output terminal of the solar cell panel according to Embodiment 1, and shows a circuit for measuring and calculating the high-frequency characteristic of the impedance stored in the output terminal box 2. Shown in block diagram. The output line 3 includes a positive side line and a negative side line of DC power generated by the solar cell panel. In FIG. 3, the output line 31 is a negative side line and the output line 32 is a positive side line. In a state where a plurality of solar battery panels are connected, a backflow prevention diode 26 is inserted in the plus side line in order to protect a healthy panel when another panel fails. The left end of the output line 3 in FIG. 3 is connected to the solar cell panel 1 at the tip.

  A high frequency signal source 33 that superimposes a high frequency on the output line 3 supplies a high frequency signal from the position on the power generation layer side through the blocking capacitor 34 from the backflow prevention diode. The high frequency signal source 33 outputs a high frequency in the frequency range set by the control unit 42. The high frequency signal source 33 is combined with the blocking capacitor 34 to constitute the high frequency signal generator 25.

  A voltage sensor 37 that detects a high-frequency voltage between the output lines is disposed between the output line 31 and the output line 32, and a current sensor 36 that detects a high-frequency current is inserted into the output line 32 of the plus side line. . The signals detected by the voltage sensor 37 and the current sensor 36 are converted into a high frequency impedance by the voltage / current phase difference comparison unit 40 and the impedance calculation unit 41.

  The high frequency frequency superimposed by the high frequency signal source 33 is changed within a predetermined range, and the detection value is acquired for each sampling frequency point, whereby the impedance is converted into the impedance at each frequency point, and the control unit 42 (21 ) Is calculated as a high frequency characteristic of impedance. The obtained high frequency characteristic of the impedance is transmitted from the data communication unit 43 (22) to the external host computer HC as the impedance data of the solar battery panel. The power supply unit 27 is disposed between the output lines, stores electricity when the solar cell panel 1 generates power during the daytime, and is used as a power supply for operating the circuit when calculating the impedance.

  For the output terminal box, since impedance is detected and calculated using a high-frequency signal of about MHz, noise in the installation environment of the solar cell panel becomes a problem. Therefore, in the present embodiment, a casing in which conductive metal plating is applied to the inner surface of the output terminal box 2 is used. Thereby, when a weak high frequency signal is superimposed on the output line of the solar cell panel, the impedance can be detected and calculated with high accuracy without being affected by external noise.

  Next, a method for measuring and calculating impedance will be described in detail. The high frequency signal generated by the high frequency signal source 33 is superimposed on the output line 3 of the solar cell via the blocking capacitor 34. In this case, the blocking capacitor 34 serves to block the generated direct current flowing through the output line 3 from flowing into the high-frequency signal source 33. On the contrary, the high frequency signal for measurement can easily pass through the blocking capacitor 34 and propagate to the solar cell panel 1 because the frequency is sufficiently high.

  The high-frequency signal is supplied from the solar cell panel 1 side to the position of the backflow prevention diode 26 and transmitted to the solar cell panel 1 side. The transmitted high frequency is detected by a current sensor 36 inserted in the output line 32 and a voltage sensor 37 connected between the output lines, and a high frequency signal corresponding to the impedance of the solar cell panel is detected. In this case, the current sensor 36 can detect a signal in a state where it is galvanically insulated from the output line 3 by using a pickup coil type. The voltage sensor 37 can detect a signal without directly touching the output line by using an electrostatic coupling type.

  The detected high frequency voltage and high frequency current are amplified by the voltage measurement unit 38 and the current measurement unit 39, respectively. FIG. 4 is an example of a high-frequency voltage / current waveform in the output line 3 connected to the output terminal of the solar cell panel obtained by the high-frequency impedance measuring apparatus MD according to the first embodiment. The waveform of FIG. 4 shows a voltage waveform Wv and a current waveform Wi output from the voltage measurement unit 38 and the current measurement unit 39 at a certain frequency F. The phase difference PD indicates the phase difference between the voltage waveform Wv and the current waveform Wi. Note that the amplitude and phase difference PD of the voltage waveform Wv and the current waveform Wi change in accordance with the impedance of the solar cell panel 1.

Next, the high frequency voltage and current are calculated by the phase comparison unit 40 and the impedance calculation unit 41 included in the impedance calculation unit 23, and converted into high frequency impedance at a certain frequency F. The impedance [Z _PV ] of the solar cell panel is obtained from the following equation from the amplitude [I ₀ , V ₀ ] of the voltage and current and the phase difference PD [θ].

When obtaining the impedance from the high-frequency current / voltage, a phase difference is caused unless the mounting positions of the voltage sensor and the current sensor can be made exactly the same, so that a slight difference in the measurement position of the sensor becomes a problem. Particularly, when the digit of the frequency of the high frequency signal superimposed on the output line is about MHz, it is difficult to accurately measure the phase difference theta, easily includes errors in the impedance Z _PV. Therefore, as described later, it is necessary to measure the phase difference in the frequency band to be used in advance and to correct the actual measurement value.

  FIG. 5 is a circuit diagram of the high-frequency voltage / current detection sensor of the high-frequency impedance measuring apparatus MD in the first embodiment. In the present embodiment, the current sensor 52 and the voltage sensor 53 shown in FIG. 5 are configured as one sensor unit 51, and the arrangement of the current sensor 52 (corresponding to the current sensor 36) and the voltage sensor 53 (corresponding to the voltage sensor 37) is arranged. Fixed. Terminal 54, terminal 55, terminal 56, and terminal 57 are each connected to the output line of the solar cell, terminal 54 and terminal 55 are connected to the solar cell panel 1, and terminal 56 and terminal 57 are connected to the high-frequency signal source 33 side. The

  Using a sensor unit as described above, a dummy load of 50Ω is connected to the terminals 54 and 55, and the phase difference PD is measured in the frequency range generated from the high-frequency signal source 33. A calibration value is used when the phase difference PD is calculated from the waveforms detected by the current sensor 52 and the voltage sensor 53 connected to the panel.

  Here, by changing the frequency of the high-frequency signal output from the high-frequency signal source 33, measuring the high-frequency current / voltage for each sampling point, and calculating the high-frequency impedance, the high-frequency impedance characteristics of the solar cell panel 1, that is, the impedance Frequency dependence is obtained. The obtained high frequency characteristic data of the impedance of the solar cell panel 1 is transmitted from the data communication unit 43 to the external host computer HC.

  FIG. 6 is a graph showing an example of the high-frequency characteristic of the impedance of the solar cell panel obtained by the high-frequency impedance measuring apparatus according to the first embodiment. The impedance characteristics of the solar cell panel 11 were calculated using the detection / calculation method described above. The solar cell panel 11 used was composed of an amorphous silicon layer and a fine silicon substrate on a 1.0 m × 1.4 m glass substrate. A thin film silicon solar battery cell having a tandem structure in which a crystalline silicon layer was stacked and sealed with a glass plate with a sealing material interposed therebetween was used.

The graph (A) in FIG. 6 represents the dependency of the impedance Z _{PV on} the frequency F, and the graph (B) represents the dependency of the phase difference PD on the frequency F. These impedance characteristics are measured in the night zone (dark state) where the solar cell panel 11 does not generate power, the lower limit frequency is set to F ₁ = 300 kHz, the upper limit frequency is set to F ₂ = 10 MHz, and the high frequency signal source 33 uses the frequency F. Was changed from F ₁ to F _2, and the impedance Z _PV of the solar cell panel 11 was calculated with respect to the frequency of the sampling point.

As shown in the graph (A) of FIG. 6, as the frequency F increases from 300 kHz, the intensity of the impedance Z _PV of the solar cell panel 11 first decreases, and the frequency indicated by the arrow is F = 1. After showing a minimum value around 8 MHz, it increased again. On the other hand, as shown in the graph (B) of FIG. 6, the phase difference PD of the impedance Z _PV has a frequency of F to 1.8 MHz and is −90 ° (capacitive load) to + 90 ° (inductive load). And the sign is reversed at the point indicated by the arrow. From this, it can be seen that the frequency characteristic of the impedance Z _PV of the solar cell panel 11 shows a resonance characteristic around F = 1.8 MHz. The resonance frequency F _res is a frequency when the value of the impedance Z _PV is minimum and the phase becomes 0 °. In this example of the solar cell panel 11, F _res = 1.774 MHz. The minimum value of the impedance Z _PV was 12.33Ω (@ 1.774 MHz).

  Since the values of the resonance frequency and the minimum impedance are determined by the state of the solar cell panel 1, the state of the panel can be grasped and managed by grasping these numerical values. However, only by detecting that these numerical values have changed, it is impossible to know which part of the panel has a problem and in which part. In order to identify the defect location, the impedance characteristics of the solar cell panel 1 may be replaced with an electrical equivalent circuit, and the characteristics of each element may be calculated assuming a constant circuit with virtual elements. Among the specific elements in the equivalent circuit, for example, if the value of the series resistance changes, it can be considered that a problem has occurred at a location (that is, an electrode or a wiring portion) corresponding to this element. As described above, grasping and managing the equivalent circuit constant specific to the solar cell panel is effective for identifying the defective part.

Hereinafter, a method for grasping and managing the state of the solar cell panel from the high frequency characteristic of the impedance on the host computer HC of the photovoltaic power generation system will be described.
FIG. 7 is a diagram showing a high-frequency equivalent circuit model of the solar cell panel, and specifically shows an equivalent circuit model in a dark state up to the output terminal box of the solar cell panel 1 shown in FIG. Electrodes and wiring of the solar cell panel 1 is represented by the series connection of the series resistor r _s and parasitic inductance L. In addition, the solar cell portion having the internal configuration of the electrode / power generation layer / electrode has a pn junction of the power generation layer in the dark state without light irradiation in addition to the series resistance r _s of the electrode portion and the shunt resistance R _sh of the power generation layer. part using junction capacitance C _d of, can be represented by a series-parallel circuit as shown in FIG.

Therefore, it is considered that the total impedance Z _PV of the solar cell panel 1 viewed from the output terminal box 2 can be expressed by the following equation.


Here, 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


When satisfying the relationship, 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.

As shown in FIG. 6, the impedance Z _PV of the solar cell panel 1 shows resonance characteristics, and Z _PV changes greatly in the frequency region before and after the resonance frequency _Fres. Therefore, in this region, the equations (2) and (4 When the equation (4) is fitted to an actual measurement value, four circuit constants (r _s , R _sh , L, C _d ) that are fitting parameters in the equation can be relatively easily obtained. It is not always necessary to use such resonance characteristics when fitting the equation (2), but it is desirable to perform fitting in a frequency region before and after the resonance frequency _Fres in order to improve fitting accuracy.

FIG. 8 is a diagram illustrating an example of the result of performing impedance circuit analysis and equivalent circuit analysis of the solar cell panel. FIG. 8 shows the result of fitting in the frequency region where the frequency F is from 500 kHz to 4 MHz as the region including the resonance frequency (F _res = 1.774 MHz). Here, circle is the measured value of the impedance Z _PV, the solid line is the result of fitting (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 = 12.2Ω, parasitic inductance L = 3.2 μH, shunt resistance R _sh = 5.3 kΩ, and junction capacitance C _d = 4.5 nF. . In this way, the equivalent circuit constant of the solar cell panel 1 can be obtained.

Next, a method for diagnosing a solar cell panel based on circuit constants obtained by equivalent circuit analysis and a result of diagnosing the degree of deterioration of the solar cell panel 1 will be described. Here, a high-temperature / high-humidity test was performed using the solar cell panel 11 described above, and the power generation characteristics and high-frequency characteristics of the panel were evaluated after the test. The conditions of the high temperature / high humidity test are an air temperature of 85 ° C. and a humidity of 85% RH. The test times were 1,000 hours and 2,000 hours, and the characteristics were evaluated a total of three times including the initial values before the test. From the results of the high frequency characterization, the manner already measurement and analysis described, it was determined the equivalent circuit constant of the solar cell panel _{11 (r s, R sh,} L, C d) a.

Table 1 shows the equivalent circuit constants (r _s , R _sh , L, C _d ) and conversion efficiency of the solar cell panel after the high temperature / high humidity test (1,000 hours, 2,000 hours) was performed. η) is shown. Here, circuit constants and conversion efficiency values are normalized with initial values before testing. After 1,000 hours of high temperature and high humidity test, the conversion efficiency η of the solar cell panel hardly changes. However, for the circuit constant of the panels, it is slightly lowered value of the junction capacitance C _d 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 of 1,000 hours, almost no change is observed in the power generation characteristics of the solar cell panel, but it is recognized that slight degradation occurs in the power generation layer. When the solar cell panel 11 was continuously subjected to the high temperature / high humidity test, as shown in Table 1, the conversion efficiency η was greatly reduced to 0.86 after 2,000 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 portions of the wiring hardly changed, the junction capacitance C _d of the power generation layer is 0.85, the shunt resistance R _sh 0. It was greatly reduced to 90. 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, at a high temperature and high humidity test for 2,000 hours, the corrosion of the metal can be said to not occurred.

Thus, according to the photovoltaic module of the present invention, before the conversion efficiency of the solar cell panel is lowered, at an early stage, it is possible to detect the Taker of C _d and R _sh. By detecting and calculating the high frequency characteristics of impedance for each solar panel and using the data to determine the deterioration of the solar panel, it is possible to detect the deterioration more sensitively than conventional power generation monitoring. It is.

  The photovoltaic power generation module according to the present invention superimposes a high frequency signal having a variable measurement frequency via a blocking capacitor on the output line of the solar cell panel 1 at a position not including a backflow prevention diode, The high frequency signal superimposed from the current sensor is detected, the frequency dependence of the high frequency impedance is calculated from the obtained signal, and transmitted to the outside. The photovoltaic power generation system obtains the high-frequency equivalent circuit constant of the solar cell panel 1 from the obtained impedance frequency-dependent characteristics before and after the resonance point, changes over time in the equivalent circuit constant, and circuits in the normal solar cell panel 1. By using a constant as a reference value, the deterioration state of the solar cell panel and the presence or absence of a failure can be diagnosed in detail by relative comparison.

Embodiment 2. FIG.
In the first embodiment, the frequency of the high-frequency signal generator 25 is changed from 300 kHz to 10 MHz at equal intervals. However, the sampling in the impedance measurement does not necessarily have to be uniform over the entire band of the high frequency signal. FIG. 9 is a graph showing an example of the high frequency characteristic of the impedance obtained by the high frequency impedance measuring device MD, and the density of the plot is not constant with respect to the frequency. That is, the frequency characteristics are acquired finely in the band where the plot is dense, and the frequency characteristics are acquired roughly in the band where the plot is coarse. The dense band is a band centered on the resonance frequency. Here, the average sampling interval in the frequency band within the frequency range to be measured and including the resonance frequency of the solar cell panel 1 is determined to be smaller than the average sampling interval in the outer frequency band.

As described above, the sampling interval for detecting the high-frequency current / voltage and calculating the impedance may be changed between the frequency band around the resonance point and the frequency band away from the resonance point. In FIG. 9, high-density sampling is performed at a sampling interval of 16 KHz between 800 kHz and 2.6 MHz. On the other hand, outside the frequency range, sampling with a low density of sampling interval = 160 KHz was performed.
The characteristic change is rapid around the resonance frequency, but the change is gentle elsewhere, so the accuracy of the impedance characteristic obtained is almost the same, and the equivalent circuit constant calculated from the characteristic is also the embodiment. An accuracy almost equal to 1 can be obtained. In this case, since the frequency band before and after the important resonance point is roughly measured in a region other than that, the time required for detection and calculation can be shortened. Further, since the amount of calculated impedance data can be reduced, there is an advantage that the circuit configuration in the output terminal box can be made compact and the amount of data to be transferred can be reduced. Therefore, even in a large-scale photovoltaic power generation system using a large number of photovoltaic power generation modules, it is possible to diagnose the deterioration state of the solar cell panel and the presence or absence of a failure in a short time.

Embodiment 3 FIG.
In the first embodiment, the case where a high frequency signal of a sine wave is superimposed on the output line of the solar cell panel is described, but a rectangular pulse signal may be superimposed on the output line. FIG. 10 is a diagram showing a signal waveform of the high-frequency impedance measuring apparatus for the solar battery panel in the present embodiment. When the pulse signal 101 shown in the figure is superimposed on the output line 3, the voltage waveform 102 shown in the following figure was obtained from the voltage sensor 37. Similarly, in the current sensor 36, a similar current waveform is obtained.
The obtained voltage waveform and current waveform are subjected to Fourier transform by a dedicated calculation unit, and calculation for decomposing into a combination of sine waves is executed. The high frequency impedance is calculated from the sine wave signal obtained by the calculation using the method described in the first embodiment.
A value on the order of nsec (1 ns or more and 10 ns or less) is selected as the rise time of the superimposed pulse signal 101. One pulse repetition period is selected from about 10 nsec to 1 msec. The pulse signal 101 includes a high-frequency component because it rises quickly, and can be considered as a high-frequency signal regardless of the repetition period in the present invention.

In addition, when calculating an impedance from the sine wave obtained by Fourier transform, it can be used as a practical electric current / voltage signal from the fundamental wave to the fifth order wave. Therefore, in order to obtain impedance characteristics using waveforms from the fundamental wave to the fifth order wave, it is desirable that the frequency of the fundamental wave is in a range below the resonance frequency of the impedance.
In this case, since the rectangular pulse signal is superimposed on the output line of the solar cell panel, the pulse signal generation unit may be a logic circuit generation method. Therefore, there exists an advantage which can implement | achieve the system which diagnoses the deterioration state of a solar cell panel and the presence or absence of a failure with a comparatively simple structure.

Embodiment 4 FIG.
FIG. 11 is a schematic diagram illustrating a configuration of a solar power generation system using the above-described solar power generation module GM. In this system, a plurality of photovoltaic power generation modules GM are arranged, and the output line 3 and the communication means 28 are connected. It goes without saying that the communication means 28 is not necessarily wired and may be wireless. The output line 3 is connected to the power conditioner 60, and a direct current is converted into an alternating current by the power conditioner 60. The communication means 28 is connected to the host computer HC and transmits impedance information from the solar power generation module GM to the host computer HC and transmits a command from the host computer HC to the solar power generation module GM. The communication unit 29 is a data transmission unit that connects the power conditioner 60 and the host computer HC, and can transmit information related to the operating condition of the power conditioner 60 to the host computer HC.
FIG. 12 is a diagram illustrating the configuration of the back surface of the photovoltaic power generation module GM. The output line 3 and the communication means 28 are connected to the output terminal box 2 and attached to the back surface of the solar cell panel 1. A high frequency impedance measuring device MD is mounted on the output terminal box 2, and data is transmitted to the host computer HC via the control unit 21 and the data communication unit 22. The host computer HC calculates an equivalent circuit constant for each solar cell panel 1 from the obtained high frequency characteristic of the impedance, and detects the degree of deterioration of the solar cell panel 1 by comparison with a reference value.

The solar power generation system as described above may control the operation of the high-frequency impedance measuring device MD from the host computer HC to the control unit 21 via the data communication unit 22. By controlling the high frequency impedance measuring device MD, the impedance measurement of each solar cell panel 1 of the entire photovoltaic power generation system can be sequentially executed. Impedance measurement is preferable at night when it is not exposed to sunlight. Using a clock built in the host computer HC, measurement can be automatically started at each module at sunset to check for the occurrence of defects. . When a defective solar power generation module is detected, the necessary amount of maintenance such as replacement of the solar battery panel 1 or repair of the output terminal box 2 is performed as soon as possible so that the amount of power generation during the day is not reduced. It becomes possible to operate a solar power generation system.

DESCRIPTION OF SYMBOLS 1 Solar cell panel 2 Output terminal box 3 Output line 21 Control part 22 Data communication part 23 Impedance calculation part 24 Current / voltage detection part 25 High frequency signal generation part 26 Backflow prevention diode 27 Power supply part 33 High frequency signal source 34 Blocking diode 36 Current sensor 37 Voltage sensor

Claims (9)

A photovoltaic power generation module having an output terminal box for extracting the power generation output of the solar cell panel through an output line,
The output terminal box is
A backflow prevention diode inserted in the output line;
An impedance measuring device for measuring the impedance of the solar cell panel;
With
The impedance measuring device includes:
A signal generator for superimposing a high-frequency signal on the output line;
A signal detector provided on the output line for detecting a high-frequency signal;
An impedance calculator that calculates a high-frequency characteristic of the impedance of the solar cell panel from a high-frequency signal detected by the signal detector;
A solar power generation module comprising: The photovoltaic module according to claim 1, wherein the high-frequency signal superimposed on the output line is variable in a frequency range including a resonance frequency of the solar cell panel. The photovoltaic power generation module according to claim 2, wherein a frequency range of the high-frequency signal includes a range of 300 Hz to 10 MHz. The photovoltaic generator module according to any one of claims 1 to 3, wherein the signal generator superimposes a high-frequency signal on an output line of the solar cell panel via a blocking capacitor. 5. The photovoltaic power generation module according to claim 1, wherein the signal generator superimposes a high-frequency signal on the output line between the backflow prevention diode and the solar battery panel. The signal detection unit performs sampling at a predetermined frequency interval,
Within the frequency range to be measured
The average sampling interval in the first frequency band in the range including the resonance frequency of the solar cell panel,
Smaller than the average sampling interval in the second frequency band not including the first frequency band,
The photovoltaic power generation module according to any one of claims 1 to 5. The solar power generation module according to claim 1, wherein the high-frequency signal superimposed on the output line is a pulse signal. A solar power generation system including a plurality of the solar power generation modules according to any one of claims 1 to 7,
Calculate the equivalent circuit constant of the solar cell panel from the high frequency characteristics of the impedance,
By comparing the value of the equivalent circuit constant with the reference value,
A solar power generation system for detecting deterioration of the solar cell panel. The photovoltaic power generation system according to claim 8, wherein the measurement of the high-frequency characteristic of the impedance is automatically started after sunset.