Degradation diagnosis device for solar cell string and solar power generation system having the same

Abstract

A degradation diagnosis device (30) for a solar cell string (10) and a solar power generation system (100) are provided, comprising: an impedance measuring device (32) for measuring the frequency characteristics of a first impedance between one end and the other end of a plurality of solar power generation units (13a) connected in series in the solar cell string (10), and for measuring the frequency characteristics of a second impedance between one end of the plurality of solar power generation units (13a) connected in series in the solar cell string (10) and a frame (13d); and an analysis unit (34) for analyzing the frequency characteristics of the first impedance between the plurality of solar power generation units (13a) connected in series in the solar cell string (10). A first increment from an initial value of a series resistance component between one end and the other end of a plurality of connected solar power generation units (13a) is calculated, and based on the frequency characteristics of a second impedance, a second increment from an initial value of a resistance component between one end of a plurality of serially connected solar power generation units (13a) of a solar cell string (10) and a frame (13d) is calculated; and a degradation determination unit (36) determines the position of a solar cell module (13) whose resistance has increased within the solar cell string (10) based on the first increment and the second increment calculated by the analysis unit (34).

Description

Technical Field

[0001] The present invention relates to a degradation diagnosis device for a solar cell string and a solar power generation system having the degradation diagnosis device. Background Art

[0002] A solar cell module is constructed, for example, by connecting crystalline solar cells that use a single crystal or polycrystalline silicon substrate to form a solar cell unit, or thin-film solar cells that deposit a silicon thin film on a glass substrate to form a solar cell unit, in series or in parallel to form a panel, and has a frame and a terminal box serving as an outer frame.

[0003] A plurality of these solar cell modules are prepared, and the solar cell cells of the plurality of solar cell modules are connected in series. The frames of these solar cell modules are fixed to a common metal frame, thereby forming a solar cell string.

[0004] A plurality of solar cell strings are arranged in an array and combined with a transmission cable, a connection box and a power conditioner to form a solar power generation system. Such a solar power generation system is not only used for ordinary household power generation purposes, but also for large-scale solar power plants with a power generation capacity of greater than or equal to 1MW.

[0005] Generally, solar cell modules do not have mechanically operated parts, and their lifespan is claimed to be greater than or equal to 20 years. However, in reality, due to various reasons, there have been reports of failures occurring several years after the start of operation. As causes of failure, for example, it is known that there is an increase in resistance caused by the degradation of the power generation layer in the solar cell unit or the corrosion of the electrode part, a decrease in the transmittance of the packaging material filled between the solar cell unit and the glass to protect the solar cell unit, insulation degradation, an increase in wiring resistance in the solar cell module, or poor grounding of the metal bracket to which the solar cell module is fixed.

[0006] Due to these failures, the power of the solar cell module is sometimes reduced, resulting in an operational failure. Therefore, in order to improve the reliability of the solar power generation system and achieve further popularization, a technology that can diagnose the presence or absence of a failure in the solar cell module or solar cell string is also sought. For example, as a method for diagnosing a failure in a solar cell string, a method for diagnosing a failure in a solar cell string by measuring the inductance of the solar cell string has been proposed (for example, refer to Patent Document 1).

[0007] Patent Document 1: Japanese Patent No. 6214845 Summary of the invention

[0008] However, in the existing method of diagnosing solar cell string faults, fault diagnosis is performed on a solar cell string basis, and it is not possible to identify the solar cell module that has deteriorated within the solar cell string. Therefore, there is a problem that the solar cell modules need to be removed one by one for confirmation, which requires a lot of time and work.

[0009] Therefore, the present invention is proposed to solve such conventional problems, and its object is to provide a degradation diagnosis device for a solar cell string capable of identifying the position of a degraded solar cell module in the solar cell string and a solar power generation system having the degradation diagnosis device.

[0010] In order to achieve the above object, a degradation diagnosis device for a solar cell string according to the present invention includes a solar cell string having a plurality of solar cell modules, each of which has a solar power generation unit and a conductive frame, wherein the solar power generation units of the plurality of solar cell modules are electrically connected in series, and the frames of the plurality of solar cell modules are electrically connected in common, and the degradation diagnosis device for the solar cell string includes: an impedance measuring device that measures a frequency characteristic of a first impedance between one end and the other end of the plurality of solar power generation units connected in series of the solar cell string, and measures a frequency characteristic of a second impedance between one end of the plurality of solar power generation units connected in series of the solar cell string and the frame; an analyzing unit that calculates a first increase from an initial value of a series resistance component between one end and the other end of the plurality of solar power generation units connected in series of the solar cell string based on the frequency characteristic of the first impedance, and calculates a second increase from an initial value of a resistance component between one end of the plurality of solar power generation units connected in series of the solar cell string and the frame based on the frequency characteristic of the second impedance; and a degradation determination unit that determines a position of a solar cell module whose resistance in the solar cell string has increased based on the first increase and the second increase calculated by the analysis unit.

[0011] Effects of the Invention

[0012] The degradation diagnosis device for a solar cell string of the present invention configured as described above and the solar power generation system having the degradation diagnosis device calculate the first increment of the series resistance component between one end and the other end of a plurality of solar power generation units connected in series from the initial value and the second increment of the resistance component between one end and the frame of a plurality of solar cell units connected in series from the initial value by the analysis unit, and the degradation determination unit determines the position of the solar cell module whose resistance has increased in the solar cell string based on the first increment and the second increment calculated by the analysis unit. Thus, the position of the solar cell module in which degradation has occurred in the solar cell string can be determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a diagram schematically showing the general configuration of a solar power generation system and a degradation diagnosis device for a solar cell string according to Embodiment 1 of the present invention.

[0014] Figure 2 This is a diagram showing a schematic configuration of the interior of a connection box of a photovoltaic power generation system and a photovoltaic string degradation diagnosis device according to Embodiment 1 of the present invention.

[0015] Figure 3 This is a flowchart showing the operation of the degradation diagnosis device according to Embodiment 1 of the present invention.

[0016] Figure 4 This is a diagram showing an example of the frequency characteristics of the second impedance between the output terminal 11 - 1 and the frame 13 d at various positions of the solar cell module having increased resistance in the solar cell string according to the first embodiment of the present invention.

[0017] Figure 5 This is a diagram showing an example of the relationship between the parameter X and the position of the solar cell module 13 where the resistance increases according to the first embodiment of the present invention.

[0018] Figure 6 This is a diagram showing an equivalent circuit model of a solar cell string according to Embodiment 1 of the present invention.

[0019] Figure 7 This is a simplified diagram of an equivalent circuit model of a solar cell string according to Embodiment 1 of the present invention.

[0020] Figure 8 This is a diagram showing a schematic configuration of the interior of a connection box of a photovoltaic power generation system and a photovoltaic string degradation diagnosis device according to a second embodiment of the present invention.

[0021] Fig. 9 This is a flowchart showing the operation of the degradation diagnosis device according to the second embodiment of the present invention.

[0022] Fig.10 This is a flowchart showing the operation of the degradation diagnosis device according to Embodiment 3 of the present invention.

[0023] Fig.11 This is a flowchart showing the operation of the degradation diagnosis device according to the fourth embodiment of the present invention. DETAILED DESCRIPTION

[0024] First, the structure of the degradation diagnosis device of the solar cell string and the solar power generation system having the degradation diagnosis device of the present invention will be described with reference to the accompanying drawings. In addition, the figures are schematic diagrams, which are diagrams that conceptually illustrate functions or structures. In addition, the present invention is not limited to the embodiments shown below. Except for the cases specifically described, the basic structure of the degradation diagnosis device of the solar cell string and the solar power generation system having the degradation diagnosis device is common in all embodiments. In addition, the parts marked with the same reference numerals are the same or equivalent parts, which are common to the entire text of the specification.

[0025] Implementation method 1.

[0026] Figure 1 This is a diagram schematically showing the general configuration of a solar power generation system and a degradation diagnosis device for a solar cell string according to the present embodiment. Figure 2 This is a diagram showing a schematic configuration of the interior of a connection box of a solar power generation system and a degradation diagnosis device for a solar cell string according to the present embodiment.

[0027] like Figure 1 As shown, the solar power generation system 100 includes a solar cell string 10, a connection box 20 connected to the solar cell string 10, a degradation diagnosis device 30 connected to the connection box 20 and diagnosing degradation of the solar cell string 10, and a transmission cable and a power conditioner (not shown). The solar cell string 10 has an output terminal 11-1 on the positive side and an output terminal 11-2 on the negative side, and the output terminals 11-1 and 11-2 are electrically connected to the connection box 20 via output cables 12-1 and 12-2. In addition, as for the solar cell string 10, the output terminals 11-1 and 11-2 are electrically connected to the transmission cable and the power conditioner (not shown) via the output cables 12-1 and 12-2 and a switching unit such as a switch (not shown) in the connection box 20. Moreover, the power generated by the solar cell string 10 is output from the output terminals 11-1 and 11-2 to the transmission cable and the power conditioner (not shown) via the connection box 20.

[0028] like Figure 1 As shown in FIG. 1 , the solar cell string 10 includes a plurality of solar cell modules 13. Each of the plurality of solar cell modules 13 includes a solar power generation unit 13a, a terminal box 13b, 13c, and a frame 13d. Figure 1 One solar cell string and five solar cell modules are shown, but multiple solar cell strings may be connected in parallel, and the number of solar cell modules is not limited to five, as long as two or more solar cell modules are connected in series.

[0029] The solar power generation unit 13a generates electricity in response to the received sunlight. The solar power generation unit 13a uses, for example, solar cell units connected in series or in parallel. Here, the solar cell unit may be a solar cell unit composed of a semiconductor using a PN junction, for example, a crystalline solar cell unit composed of a single crystal silicon substrate, or a thin film solar cell unit composed of a glass substrate and a silicon thin film, etc.

[0030] The terminal boxes 13b and 13c have a positive terminal box 13b and a negative terminal box 13c, and are arranged on the back side of the solar cell module 13 to obtain the generated power of the solar power generation unit 13a. The positive terminal box 13b is electrically connected to the output terminal 11-1 on the positive side, and the negative terminal box 13c is electrically connected to the output terminal 11-2 on the negative side. Thus, the generated power obtained by the terminal boxes 13b and 13c is output to the outside of the solar cell string 10 via the output terminals 11-1, 11-2 and the connection box 20.

[0031] The frame 13d is a conductive frame such as a metal frame, and is disposed on the outer periphery of the solar cell module 13. The frame 13d is usually electrically insulated from the solar power generation unit 13a, the terminal boxes 13b and 13c, and the output terminals 11-1 and 11-2.

[0032] As for the plurality of solar cell modules 13 of the solar cell string 10, Figure 1 As shown, a plurality of solar power generation units 13a are electrically connected in series through output cables 14-1 and 14-2. That is, as a series connection, in this embodiment, the output cable 14-2 on the negative pole side of one solar cell module 13 of any two adjacent solar cell modules 13 is connected to the output cable 14-1 on the positive pole side of the other solar cell module 13. As a result, the output cable 14-1 of the solar cell module 13 at one end and the output cable 14-2 of the solar cell module 13 at the other end become output cables that are not used for the series connection.

[0033] like Figure 1As shown, multiple frames 13d of multiple solar cell modules 13 are electrically connected in common. As such a common connection, in this embodiment, the frame 13d of one solar cell module 13 of any two adjacent solar cell modules 13 is electrically connected to the frame 13d of the other solar cell module 13 via grounding wires 15-1 and 15-2, and the grounding wire 15-2 of the frame 13d of the solar cell module 13 located at the other end is grounded. In addition, the connection between the frames 13d is not limited to such a series connection. For example, when the solar cell module 13 is fixed to a metal bracket and installed outdoors, the grounding wire can be replaced by the bracket to electrically connect the frame 13d. In addition, the grounding wire 15-1 of the frame 13d of the solar cell module 13 located at one end is not only electrically connected to the frame 13d of the adjacent solar cell module 13, but also electrically connected to the connection box 20 via the grounding wire 16.

[0034] like Figure 2 As shown, the connection box 20 includes a blocking capacitor 22 for DC cutoff connected to the output cable 12-1 at one end, a switch 24 connected to the output cable 12-2 at one end, an inductor 26 for resonance point adjustment connected to the ground line 16 at one end, and a switch 28 connected to the other end of the inductor 26. The other end of the blocking capacitor 22 and the other ends of the switches 24 and 28 are connected to the coaxial cable 40.

[0035] like Figure 2 As shown, the coaxial cable 40 includes a central conductor 42, an insulating dielectric 44, and an outer conductor 46. The central conductor 42 is electrically connected to the other end of the DC blocking capacitor 22 and is connected to the outer conductor 46 described later. Figure 1 The external conductor 46 is electrically connected to the other end of the switches 24 and 28 and is connected to the measuring terminal of the impedance measuring device 32 of the degradation diagnosis device 30. Figure 1 The center conductor 42 and the outer conductor 46 are electrically insulated from each other by the dielectric 44 .

[0036] Here, the resonance point adjustment inductor 26 and the switch 28 are connected in series to form a resonance point adjustment circuit. The value of the resonance point adjustment inductor 26 may be selected so that the resonance frequency of the second impedance to be measured falls within the measurement frequency region of the impedance measurement device 32 described later. Figure 2 The position relationship is opposite.

[0037] The switches 24 and 28 may be manual toggle switches, or switching elements such as diode switches driven by gate signals or MOSFETs (Metal-Oxide-Semiconductor-Field-Effect-Transistors), mechanical relays, and the like.

[0038] like Figure 1 As shown, degradation diagnosis device 30 for diagnosing degradation of solar cell string 10 includes an impedance measurement device 32 , an analysis unit 34 , and a degradation determination unit 36 ​​.

[0039] The impedance measuring device 32 measures the frequency characteristics of the first impedance between one end and the other end of the plurality of solar power generation units 13a connected in series of the solar cell string 10, and measures the frequency characteristics of the second impedance between one end of the positive pole side of the plurality of solar power generation units 13a connected in series of the solar cell string 10 and the frame 13d.

[0040] Specifically, if Figure 1 and Figure 2 As shown, the impedance measuring device 32 is electrically connected to the output terminal 11-1 on the positive side via the blocking capacitor 22 in the connection box 20, and is electrically connected to the output terminal 11-2 on the negative side via the switch 24 in the connection box 20. Therefore, by turning on the switch 24 and turning off the switch 28, the frequency characteristics of the first impedance between one end and the other end of the plurality of solar power generation units 13a connected in series of the solar cell string 10 can be measured. Then, the resonance point of the first impedance is determined based on the measured frequency characteristics of the first impedance, and the value of the first impedance corresponding to the resonance point is output to the analysis unit 34 of the subsequent stage.

[0041] In addition, if Figure 1 and Figure 2 As shown, the impedance measuring device 32 is electrically connected to the commonly connected frame 13d via the switch 28 and the inductor 26 in the connection box 20. Therefore, by turning off the switch 24 and turning on the switch 28, the frequency characteristics of the second impedance between one end of the plurality of solar power generation units 13a connected in series of the solar cell string 10 and the frame 13d can be measured. Then, the resonance point of the second impedance is determined based on the measured frequency characteristics of the second impedance, and the value of the second impedance corresponding to the resonance point is output to the analysis unit 34 of the subsequent stage.

[0042] Here, the impedance measuring device 32 can determine the resonance point by substantially scanning the measurement frequency, so in this embodiment, the impedance measuring device 32 uses a high-frequency measurement signal to measure the frequency characteristics of the first impedance and the second impedance. In addition, substantially scanning the measurement frequency means, for example, an action of continuously scanning the frequency or an action of discretely scanning at fixed intervals. As such an impedance measuring device 32, for example, a network analyzer, an impedance analyzer, or a combination analyzer can be applied, and a device in which a variable-frequency high-frequency transmitter, a current sensor, a voltage sensor, an A / D converter, or an operation device is combined can also be applied.

[0043] Here, the impedance measuring device 32 measures the frequency characteristics of the second impedance between one end of the positive pole side of the plurality of solar power generation units 13a connected in series of the solar cell string 10 and the frame 13d, but is not limited to the positive pole side, and can also measure the impedance between the other end of the negative pole side of the plurality of solar power generation units 13a connected in series of the solar cell string 10 and the frame 13d.

[0044] In addition, Figure 1 In the example, it is assumed that the housing of the impedance measuring device 32 is grounded through a 3P-type socket or a grounding wire, but the housing of the impedance measuring device 32 does not necessarily have to be grounded and may be electrically floating. Figure 1 The grounding wire 16 of the solar cell string 10 shown is grounded through the frame of the impedance measuring device 32 when the switch 28 is turned on, but other grounding wires may be used for grounding. Whether the frame of the impedance measuring device 32 and the solar cell string 10 are grounded or not does not substantially affect the diagnosis result of the degradation diagnosis device 30 for the solar cell string 10 according to the present embodiment.

[0045] The frequency characteristics of the first impedance and the second impedance measured by the impedance measuring device 32 are measured, for example, during the time period at night when the solar cell module 13 is not generating electricity, and when the solar cell module 13 is in a dark state. Here, during the process of measuring the frequency characteristics of the first impedance and the second impedance, if light is incident on the light receiving surface of the solar cell module 13 occasionally, the solar cell module 13a in the solar cell module 13 generates electricity, and a relatively large DC voltage of, for example, several tens to several hundreds of volts is generated between the terminal box 13b and the terminal box 13c.

[0046] In order to protect the impedance measuring device 32 from being damaged by the overvoltage, in the present embodiment, the DC blocking capacitor 22 for DC cutoff is provided between the solar cell string 10 and the measuring terminal of the impedance measuring device 32. On the other hand, since the frequency of the measuring signal supplied from the measuring terminal of the impedance measuring device 32 to the solar cell string 10 is relatively high as described above, the measuring signal can be easily transmitted to the solar cell string 10 through the DC blocking capacitor 22.

[0047] The analyzing unit 34 calculates the first increase ΔR from the initial value of the series resistance component between one end and the other end of the plurality of solar power generating units 13a connected in series in the solar cell string 10 based on the frequency characteristic of the first impedance. s The second increase ΔR from the initial value of the resistance component between one end of the plurality of solar power generating units 13a connected in series and the frame 13d of the solar cell string 10 is calculated based on the second impedance. frame Perform calculations.

[0048] Although the details will be described later, the analysis unit 34 sets the value of the first impedance corresponding to the resonance point input from the impedance measuring device 32 as the parasitic series resistance component R between one end and the other end of the plurality of solar power generation units 13a connected in series in the solar cell string 10. s The analyzing unit 34 calculates the series resistance component between one end and the other end of the plurality of solar power generating units 13a connected in series in the solar cell string 10 from the initial value R s0 The first increment ΔR s =R s -R s0 Perform calculations.

[0049] The analyzing unit 34 sets the value of the second impedance corresponding to the resonance point input from the impedance measuring device 32 as the parasitic resistance component R between one end of the plurality of solar power generating units 13a connected in series in the solar cell string 10 and the frame 13d. frame The analysis unit 34 calculates the parasitic resistance component between one end of the plurality of solar power generating units 13a connected in series and the frame 13d of the solar cell string 10 from the initial value R frame0 The second increment ΔR frame =R frame -R frame0 Perform calculations.

[0050] Then, the analyzing unit 34 calculates the first increment ΔR s and the second increment ΔR frame The signal is output to the degradation determination unit 36 ​​.

[0051] The degradation determination unit 36 ​​calculates the first increase ΔR calculated by the analysis unit 34 based on the first increase ΔR.s and the second increment ΔR frame , the position of the solar cell module 13 where the resistance in the solar cell string 10 is increased is determined.

[0052] Although the details will be described later, the degradation determination unit 36 ​​uses the first increase ΔR calculated by the analysis unit 34 s and the second increment ΔR frame , the parameter X depending on the resistance increase position in the solar cell string 10 is X=ΔR frame / ΔR s Then, based on the calculated parameter X, the solar cell module 13 having an increased resistance value in the solar cell string 10 is identified.

[0053] Here, the analysis unit 34 and the degradation determination unit 36 ​​are composed of, for example, a processor or CPU (Central Processing Unit) not shown, and a storage device such as a semiconductor memory, and are implemented by the processor or CPU executing a program stored in the storage device such as a semiconductor memory. In addition, not only the analysis unit 34 and the degradation determination unit 36, but also the control of the impedance measurement device 32, the storage and forwarding of the measurement data, etc. can be implemented as functions of the processor or CPU, and a series of actions from measurement to output of the diagnosis result can also be automatically performed.

[0054] In addition, in the present embodiment, the analysis unit 34 performs the first increment ΔR s and the second increment ΔR frame The calculation of the parameter X is performed in the degradation determination unit 36, but the first increment ΔR may be calculated by the analysis unit 34 alone. s , the second increment ΔR frame The degradation determination unit 36 ​​also calculates the parameter X, and specifies the solar cell module 13 having an increased resistance value in the solar cell string 10 based on the parameter X calculated by the analysis unit 34 .

[0055] Thus, the solar power generation system 100 and the degradation diagnosis device 30 of the solar cell string 10 according to the present embodiment are configured.

[0056] Next, the operation of the solar power generation system 100 and the degradation diagnosis device 30 for the solar cell string 10 according to the present embodiment will be described. Figure 31 is a flowchart showing the operation of the degradation diagnosis device 30 according to the present embodiment. Here, the degradation diagnosis device 30 of the solar power generation system 100 and the solar cell string 10 according to the present embodiment starts diagnosis when the solar cell module 13 is in a dark state, such as during the night time when the solar power generation unit 13a of the solar cell module 13 is not generating electricity.

[0057] First, when degradation diagnosis device 30 starts diagnosis of solar cell string 10 , solar cell string 10 is disconnected from a power transmission cable and a power conditioner (not shown) for solar power generation by a switching unit such as a switch (not shown) in connection box 20 and connected to degradation diagnosis device 30 .

[0058] Then, if Figure 3 As shown, when the diagnosis of the solar cell string 10 is started, the first analysis step is performed.

[0059] First, the switch 24 of the connection box 20 is turned on to electrically connect the output terminal of the terminal box 13c on the negative electrode side of the solar cell string 10 to the outer conductor 46 of the coaxial cable 40 and the ground terminal of the impedance meter 32. Then, the switch 28 of the connection box 20 is turned off to electrically insulate the frame 13d of the solar cell module 13 from the ground terminal of the impedance meter 32 (S11).

[0060] Next, with the switch 24 turned on and the switch 28 turned off, the impedance measuring device 32 measures the frequency characteristics of the first impedance between one end and the other end of the plurality of solar power generating units 13a connected in series in the solar cell string 10 (S12). Then, the resonance point of the first impedance is determined based on the measured frequency characteristics of the first impedance, and the value of the first impedance corresponding to the resonance point is output to the analysis unit 34 at the subsequent stage.

[0061] Then, the analyzing unit 34 sets the value of the first impedance corresponding to the resonance point input from the impedance measuring device 32 as the parasitic series resistance component R between one end and the other end of the plurality of solar power generating units 13a connected in series in the solar cell string 10. s When the impedance measurement process in step S12 is the first measurement after the degradation diagnosis device 30 is installed, that is, the initial measurement, the analysis unit 34 calculates the initial value R of the parasitic series resistance component. s0 The data is recorded in a storage device such as a semiconductor memory (S13), and the process proceeds to step S21.

[0062] Here, the series resistance component R sFor example, the frequency characteristics of the first impedance between one end and the other end of the plurality of solar power generation units 13a connected in series in the solar cell string 10 are measured between 1 kHz and 1 MHz, and the impedance value at the resonance point where the obtained impedance becomes the minimum value is set as the parasitic series resistance component R of the solar cell string 10. s .

[0063] After the initial measurement, the analysis unit 34 sets the value of the first impedance corresponding to the resonance point input from the impedance measurement device 32 as the parasitic series resistance component R between one end and the other end of the plurality of solar power generation units 13a connected in series in the solar cell string 10. s The analysis unit 34 calculates the parasitic series resistance component R between one end and the other end of the plurality of solar power generating units 13a connected in series in the solar cell string 10. s From the initial value R s0 The first increment ΔR s =R s -R s0 Calculate the first increment ΔR s The signal is output to the degradation determination unit 36 ​​(S14).

[0064] Next, when the first analysis step is completed, the second analysis step is performed.

[0065] First, the switch 24 of the connection box 20 is turned OFF to electrically insulate the output terminal of the terminal box 13c on the negative side of the solar cell string 10 from the external conductor 46 of the coaxial cable 40 and the ground terminal of the impedance meter 32. Then, the switch 28 of the connection box 20 is turned ON to electrically connect the frame 13d of the solar cell module 13 to the ground terminal of the impedance meter 32 (S21).

[0066] Next, in a state where the switch 24 is turned OFF and the switch 28 is turned ON, the impedance measuring device 32 measures the frequency characteristics of the second impedance between one end of the positive electrode side of the plurality of solar power generation units 13a connected in series in the solar cell string 10 and the frame 13d of the solar cell module 13 (S22). Then, the resonance point of the second impedance is determined based on the measured frequency characteristics of the second impedance, and the value of the second impedance corresponding to the resonance point is output to the analysis unit 34 at the subsequent stage.

[0067] Then, the analyzing unit 34 sets the value of the second impedance corresponding to the resonance point input from the impedance measuring device 32 as the parasitic resistance component R between one end of the plurality of solar power generating units 13a connected in series in the solar cell string 10 and the frame 13d. frame When the impedance measurement process in step S22 is the first measurement after the degradation diagnosis device 30 is installed, that is, the initial value R of the parasitic series resistance component is set toframe0 The data is recorded in a storage device such as a semiconductor memory (S23), and the diagnosis of the initial measurement is completed.

[0068] Here, the series resistance component R frame For example, the frequency characteristics of the second impedance between one end of the plurality of solar power generation units 13a connected in series in the solar cell string 10 and the frame 13d are measured between 1kHz and 1MHz, and the impedance value at the resonance point where the obtained impedance becomes the minimum value is set as the parasitic resistance component R of the solar cell string 10. frame .

[0069] After the initial measurement, the analysis unit 34 sets the value of the second impedance corresponding to the resonance point input from the impedance measurement device 32 as the parasitic resistance component R between one end of the plurality of solar power generation units 13a connected in series in the solar cell string 10 and the frame 13d. frame The analysis unit 34 calculates the parasitic resistance component R between one end of the plurality of solar power generating units 13a connected in series in the solar cell string 10 and the frame 13d. frame From the initial value R frame0 The second increment ΔR frame =R frame -R frame0 Calculate the second increment ΔR frame The data is output to the degradation determination unit 36 ​​(S24).

[0070] Next, when the second analysis step is completed, the first degradation determination step is performed.

[0071] First, the degradation determination unit 36 ​​determines the degradation state based on the first increase ΔR calculated in the first analysis step and the second analysis step. s and the second increment ΔR frame , for parameter X = ΔR frame / ΔR s Perform calculations.

[0072] Then, although the details will be described later, since the parameter X is a parameter that depends on the position of the solar cell module 13 in the solar cell string 10, the degradation determination unit 36 ​​identifies the solar cell module 13 having an increased resistance value in the solar cell string 10 based on the parameter X (S32).

[0073] At this time, assuming that the resistance value of one solar cell module 13 in the solar cell string 10 has significantly increased due to, for example, degradation of the power generation layer in the solar cell unit or corrosion of the electrode portion, the degradation determination unit 36 ​​determines that the first increment ΔR calculated by the analysis unit 34 is sThen, the degradation determination unit 36 ​​can notify the user of the position of the solar cell module 13 determined based on the parameter X where the resistance value has increased.

[0074] Here, in the present embodiment, the second analysis step is performed after the first analysis step is performed, but the first analysis step may be performed after the second analysis step is performed.

[0075] Next, the detailed operation principle of the solar power generation system 100 and the degradation diagnosis device 30 for the solar cell string 10 according to the present embodiment will be described.

[0076] Figure 4 This is a diagram showing an example of the frequency characteristics of the second impedance between the output terminal 11 - 1 and the frame 13 d at various positions of the solar cell module 13 with increased resistance in the solar cell string 10 according to the present embodiment. Figure 4 Shown in Figure 1 Among the solar cell modules 13 A to E in the solar cell string 10, the series resistance component R of a solar cell module 13 s Added the second impedance frequency characteristic near the resonance point at 10Ω.

[0077] like Figure 4 As shown, it can be seen that relative to the series resistance component R s If there is no increase, the impedance value at the resonance point is the series resistance component R frame The tendency is to decrease in the order of A to F. Here, Figure 4 F assumes a case where a series resistance component of 10Ω is added between E of the solar cell module 13 and the output cable 12 - 2 for some reason.

[0078] Figure 5 1 is a diagram showing an example of the relationship between the parameter X according to the present embodiment and the position of the solar cell module 13 where the resistance increases. Figure 5 Shown in Figure 4 R frame and R s Relationship between the calculated parameter X value and the position of the solar cell module with increased series resistance component: It can be confirmed that the value of parameter X tends to approach 0 from 1 in the order of A, B, C, D, E, and F for the solar cell modules 13 with increased resistance.

[0079] Next, the reason why the parameter X depends on the position where the resistance is increased in the solar cell string 10 will be described in detail. Figure 6 It is a diagram showing an equivalent circuit model of a solar cell string according to the present embodiment. Figure 7This is a simplified diagram of an equivalent circuit model of a solar cell string according to the present embodiment.

[0080] like Figure 6 As shown, each solar cell module 13 is composed of the following components: a series resistance component R generated by electrodes, cables, etc. s , the inductance component L generated by electrodes, cables, etc. s , the series capacitance component C generated by the capacitance between the pn junctions of the solar cell unit, and the capacitance component C between the frames f Therefore, it can be simply expressed by the following circuit model: s and the inductance component L s A plurality of solar cell modules 13 are connected in series, and each solar cell module 13 is connected to the frame 13d via a capacitance component C f Connected to ground wirings 15 - 1 and 15 - 2 .

[0081] For example, consider the series resistance component R of A of the solar cell module 13. sA If the impedance between the output terminal 11-1 of the solar cell string 10 and the frame terminal is measured, the series resistance component R sA is connected in series between the output terminal 11-1 and the frame 13d, so the parasitic resistance component R frame The increase in ΔR frame Equal to ΔR, parameter X = ΔR frame / ΔR s =1.

[0082] On the other hand, it is considered that the series resistance component R of B of the solar cell module 13 sB In this case, the current flowing from the output terminal 11-1 of the solar cell string 10 flows to the node P A At the solar cell module 13, the component B and the component C of A toward the solar cell module 13 are generated. fA After B of the solar cell module 13, the series resistance component R s Increase ΔR, but due to C fA The impedance does not increase, so the parasitic resistance component R frame The increase in ΔR frame The series resistance component R of the solar cell module 13 is sA The increase is small.

[0083] Similarly, the series resistance component R of C in the solar cell module 13 sC When ΔR is increased, the parasitic resistance component R frame The increase in ΔRframe The series resistance component R of the solar cell module 13 is sB When the above situation is repeated to the E of the solar cell module 13, if the series resistance component R of N of a solar cell module 13 is sN The parasitic resistance component R when ΔR is added frame The increase in ΔR frame Let ΔR frame (N), then ΔR frame (A)>ΔR frame (B)>ΔR frame (C)>ΔR frame (D)>ΔR frame (E)>ΔR frame (F) holds true, as the position where the resistance increases approaches F, the parameter X approaches 0. Here, when the position where the resistance increases is F, Figure 1 As shown in FIG. 1 , since it is assumed that the resistance between the E of the solar cell module 13 and the output cable 12-2 increases due to some reason, the parasitic resistance component R between one end of the plurality of solar power generation units 13a connected in series of the solar cell string 10 and the frame 13d is not affected. frame The increase in parasitic resistance component R frame The increase in ΔR frame (F) is 0, and parameter X is also 0. That is, parameter X also has Figure 5 The relationship depending on the position of the solar cell module 13 is as shown.

[0084] Figure 7 To explain mathematically Figure 6 Here, in each solar cell module 13, if the impedance between the terminal box 13b on the positive electrode side and the terminal box 13c on the negative electrode side of the solar cell modules A to E is set to Z N , let the admittance determined by the capacitance between the output terminal 11 - 1 of the solar cell modules 13 of A to E and the frame 13 d be Y N , let the angular frequency be ω, then the impedance Z can be expressed as follows N and admittance Y N ,therefore Figure 7 The circuit can be represented by the impedance Z N and admittance Y N A ladder circuit in which the series and parallel connections are alternately connected. Here, N represents a solar cell module 13 among A to E. For example, in the case of the solar cell module 13 of A, the impedance Z A and admittance Y A .

[0085] [Mathematical formula 1]

[0086]

[0087] [Mathematical formula 2]

[0088]

[0089] If based on the impedance Z N and admittance Y N , the impedance Z between the output terminal 11 - 1 of the solar cell module 13 and the frame 13 d can be expressed by the following equation.

[0090] [Mathematical formula 3]

[0091]

[0092] According to this formula, the increase amount ΔR of the series resistance component measured between the output terminal 11 - 1 and the output terminal 11 - 2 of the solar cell module 13 is calculated in each case. s With Z A To Z E For example, the series resistance component of C in the solar cell module 13 increases by ΔR s In the case of s is relative to Z c The series resistance component of C of the solar cell module 13 increases by ΔR s The impedance Z between the output terminal 11 - 1 of the solar cell module 13 and the frame 13 d in the case of , that is, the impedance Z(C) can be expressed by the following equation.

[0093] [Formula 4]

[0094]

[0095] That is, it can be seen that due to the real part of Z and the parasitic resistance component R frame = are equal, so the series resistance components A to E of the solar cell module 13 each increase by ΔR s In the case of frame The same relationship as above gives ΔR frame (A)>ΔR frame (B)>ΔR frame (C)>ΔR frame (D)>ΔR frame (E)>ΔR frame (F). Therefore, regarding parameters X(A) to X(F), Figure 5In the relationship shown, the parameter X is a parameter depending on the position of the solar cell module whose resistance increases in the solar cell string 10 .

[0096] Based on the above reasons, it can be qualitatively explained that Figure 5 The relationship between the parameter X and the position of the solar cell module 13 in the solar cell string 10.

[0097] In order to determine the resistance increase position of the solar cell module 13 in the solar cell string 10, for example, a circuit calculation is performed in advance to calculate the relationship between the parameter X and the position of the resistance increase of the solar cell module 13 in the solar cell string 10. Then, the parameter X obtained by measuring the frequency characteristics of the first and second impedances is compared with the parameter X of the calculated value, and the position of the solar cell module 13 can be determined based on the parameter X of the calculated value that is closest.

[0098] Here, when the solar cell string 10 is composed of solar cell modules 13 of the same specification connected in series, the equivalent circuit and circuit constant can be determined by measuring the frequency characteristics of the impedance of one solar cell module 13 in advance based on the equivalent circuit of one solar cell module 13 through circuit calculation. Then, using this value, the circuit calculation is performed when the resistance value of the solar cell module 13 in the solar cell string 10 is increased, and it is possible to obtain Figure 5 The positional relationship between the parameter X and the solar cell module 13. The circuit calculation in this case may be performed by a computer in the degradation determination unit 36, or, for example, may be calculated by an external computer and the result may be handed over to the degradation determination unit 36.

[0099] The degradation diagnosis device for a solar cell string constructed as described above and a solar power generation system having the degradation diagnosis device are provided, for example, in a Figure 1 After the degradation diagnosis device of the solar cell string and the solar cell power generation system having the degradation diagnosis device are provided, an initial measurement of the first analysis step is performed in a time period when the power generation is sufficiently low 2 hours after sunset or 2 hours before sunrise, and the parasitic series resistance component R between one end and the other end of the plurality of solar power generation units 13a connected in series of the solar cell string 10 is measured. s The initial value R s0 Similarly, the initial measurement of the second analysis step is performed to measure the parasitic resistance component R between one end of the plurality of solar power generation units 13a connected in series and the frame 13d of the solar cell string 10. frame The initial value R frame0 Make a record.

[0100] After that, the first analysis step and the second analysis step are performed every day during a period of time when the power generation is sufficiently low 2 hours after sunset or 2 hours before sunrise. The analysis unit 34 calculates the first increment ΔR s and the second increment ΔR frame Then, the degradation determination unit 36 ​​calculates the first increase ΔR based on the first increase ΔR. s and the second increment ΔR frame , calculate parameter X and monitor parameter X on a daily basis.

[0101] For example, the first increase ΔR of the series resistance component increased due to degradation of the power generation layer in the solar cell or corrosion of the electrode portion is s The threshold value of is set to 1Ω. For example, in the first analysis step performed during daily monitoring, the first increment ΔR s When the threshold value 1Ω is exceeded, the degradation determination unit 36 ​​performs a first degradation determination step of determining the position of the solar cell module 13 where the resistance value has increased based on the parameter X. Then, the degradation determination unit 36 ​​can notify the user of the position of the solar cell module 13 where the resistance value has increased, which is determined based on the parameter X.

[0102] Thus, the degradation diagnosis device for a solar cell string according to the present embodiment and the solar power generation system including the degradation diagnosis device can identify the position of a solar cell module in which degradation has occurred within the solar cell string.

[0103] Therefore, in the past, fault diagnosis could only be performed on a solar cell string basis, and determining a faulty solar cell module within a solar cell string required a great deal of time and effort. However, the degradation diagnosis device for a solar cell string and a solar power generation system having the degradation diagnosis device involved in the present embodiment can determine the position of a degraded solar cell module within a solar cell string, thereby significantly reducing the time and effort required for fault diagnosis of a solar cell module within a solar cell string.

[0104] In addition, the degradation diagnosis device for a solar cell string and the solar power generation system having the degradation diagnosis device according to the present embodiment can use a high-frequency signal in the measurement of the frequency characteristics of the impedance, and thus can diagnose the degradation of a large number of solar cell modules. In addition, since the degradation diagnosis can be performed at night when the power generation is sufficiently low 2 hours after sunset or 2 hours before sunrise, it is possible to suppress the reduction of the power generation of the solar power generation of the entire solar power generation system for the purpose of degradation diagnosis.

[0105] Implementation method 2.

[0106] The degradation diagnosis device for the solar power generation system and solar cell string of the present embodiment has the functions of the analysis unit 34 and the degradation determination unit 36 ​​of the degradation diagnosis device 30 of the first embodiment, and further has the analysis unit 34 calculate the third increase ΔR′ from the initial value of the resistance component between the other end of the negative electrode side of the plurality of solar power generation units 13a connected in series and the frame 13d. frame The degradation determination unit 36 ​​calculates the parameter X' that depends on the resistance increase position in the solar cell string 10 by X'=ΔR'. frame / ΔR s The calculation is performed, and then, based on the calculated parameters X and X′, the solar cell module 13 having an increased resistance value in the solar cell string 10 is identified.

[0107] The schematic configuration of the solar power generation system and the degradation diagnosis device for the solar cell string according to the present embodiment is similar to that of the first embodiment. Figure 1 Similarly, description of the same configurations other than the characteristic portions of the analysis unit 34 and the degradation determination unit 36 ​​of the present embodiment will be omitted. Figure 8 1 is a diagram showing a schematic structure of the inside of a connection box of a solar power generation system and a solar cell string degradation diagnosis device according to the present embodiment. Figure 2 The parts with the same reference numerals are configured similarly to the connection box 20 in the first embodiment, and thus detailed description thereof will be omitted.

[0108] like Figure 8 As shown, in addition to the same structure as the connection box 20 of embodiment 1, the connection box 20a has a switch 29 connected to the output cable 12-1, a switch 24a connected to the output cable 12-2, and a switch 28a connected between the other end of the inductor 26 connected to the ground wiring 16 and the outer conductor 46 of the coaxial cable 40.

[0109] The switch 29 can switch between terminal a connected to the blocking capacitor 22 and terminal b connected to the outer conductor 46 of the coaxial cable 40. The switch 24a can switch between terminal c connected to the blocking capacitor 22 and terminal d connected to the outer conductor 46 of the coaxial cable 40.

[0110] Although the details will be described later, by connecting the switch 29 to the terminal a, connecting the switch 24a to the terminal d, and turning off the switch 28, one end and the other end of the plurality of solar power generation units 13a connected in series of the solar cell string 10 are electrically connected, and the frequency characteristics of the first impedance can be measured. In addition, by connecting the switch 29 to the terminal a, turning off the switch 24a, and turning on the switch 28, one end of the positive side of the plurality of solar power generation units 13a connected in series of the solar cell string 10 and the frame 13d are electrically connected, and the frequency characteristics of the second impedance can be measured. In addition, by turning off the switch 29, connecting the switch 24a to the terminal c, and turning on the switch 28, the other end of the negative side of the plurality of solar power generation units 13a connected in series of the solar cell string 10 and the frame 13d are electrically connected, and the frequency characteristics of the third impedance can be measured.

[0111] Next, the operation of the solar power generation system 100 and the degradation diagnosis device 30 for the solar cell string 10 according to the present embodiment will be described. Fig. 9 2 is a flowchart showing the operation of the degradation diagnosis device 30 according to the present embodiment. Figure 3 The parts with the same reference numerals are the same as those in Embodiment 1, and thus detailed descriptions thereof are omitted, and only the differences from Embodiment 1 are described.

[0112] First, if the degradation diagnosis device 30 starts the diagnosis of the solar cell string 10 as in the first embodiment, the solar cell string 10 is disconnected from the unillustrated power transmission cable and power conditioner for solar power generation through a switching unit such as an unillustrated switch in the connection box 20 and connected to the degradation diagnosis device 30.

[0113] Then, if Fig. 9 As shown, when the diagnosis of the solar cell string 10 is started, the first analysis step is performed.

[0114] First, if Fig. 9 As shown, the switch 24a of the connection box 20a is connected to the terminal d, and the switch 28 is turned OFF. As a result, the output terminal 11-2 of the terminal box 13c on the negative side of the solar cell string 10 is electrically connected to the outer conductor 46 of the coaxial cable 40 and the ground terminal of the impedance measuring device 32, and the frame 13d of the solar cell module 13 is electrically insulated from the ground terminal of the impedance measuring device 32. Then, the switch 29 of the connection box 20a is connected to the terminal a, and the output terminal 11-1 of the terminal box 13b on the positive side of the solar cell string 10 is electrically connected to the central conductor 42 of the coaxial cable 40 and the measuring terminal of the impedance measuring device 32 (S11a).

[0115] Thereafter, the steps from step S12 to step S14 of the first analysis process are performed, but since they are the same as those in the first embodiment, detailed descriptions thereof are omitted.

[0116] Next, when the first analysis step is completed, the second analysis step is performed.

[0117] First, if Fig. 9 As shown, the switch 24a of the connection box 20a is set to OFF, and the switch 28 is set to ON. As a result, the output terminal 11-2 of the terminal box 13c on the negative side of the solar cell string 10 is electrically insulated from the ground terminal of the impedance meter 32, and the frame 13d of the solar cell module 13 is electrically connected to the outer conductor 46 of the coaxial cable 40 and the ground terminal of the impedance meter 32. Then, the switch 29 of the connection box 20a is connected to the terminal a, and the output terminal 11-1 of the terminal box 13b on the positive side of the solar cell string 10 is electrically connected to the central conductor 42 of the coaxial cable 40 and the measuring terminal of the impedance meter 32 (S21a).

[0118] Afterwards, if Fig. 9 As shown, the steps from step S22 to step S24 of the second analysis process are performed, but the detailed description is omitted because they are the same as in Embodiment 1. In the case of initial measurement, after step 23, the diagnosis is not ended as in Embodiment 1, and the third analysis process described later is entered.

[0119] Next, when the second analysis step is completed, the first degradation determination step is performed. Since the first degradation determination step is the same as that in the first embodiment, a detailed description thereof will be omitted. Fig. 9 As shown, based on the first increase ΔR calculated in the first analysis step and the second analysis step s and the second increment ΔR frame , for parameter X = ΔR frame / ΔR s Calculation is performed ( S31 ), and based on the parameter X, a first position of the solar cell module 13 where the resistance value has increased in the solar cell string 10 is identified ( S32 ).

[0120] Next, when the first degradation determination step is completed, the third analysis step is performed.

[0121] First, if Fig. 9As shown, the switch 24a of the connection box 20a is connected to the terminal c, and the switch 28 is set to ON. As a result, the output terminal 11-2 of the terminal box 13c on the negative side of the solar cell string 10 is electrically connected to the central conductor 42 of the coaxial cable 40 and the measuring terminal of the impedance measuring device 32, and the frame 13d of the solar cell module 13 is electrically connected to the outer conductor 46 of the coaxial cable 40 and the ground terminal of the impedance measuring device 32. Then, the switch 29 of the connection box 20a is set to OFF, and the output terminal 11-1 of the terminal box 13b on the positive side of the solar cell string 10 is electrically insulated from the ground terminal of the impedance measuring device 32 (S41).

[0122] Next, in a state where the switch 24a is connected to the terminal c, the switch 28 is turned on, and the switch 29 is turned off, the impedance measuring device 32 measures the frequency characteristics of the third impedance between the other end of the negative electrode side of the plurality of solar power generation units 13a connected in series in the solar cell string 10 and the frame 13d of the solar cell module 13 (S42). Then, the resonance point of the third impedance is determined based on the measured frequency characteristics of the third impedance, and the value of the third impedance corresponding to the resonance point is output to the analysis unit 34 of the subsequent stage.

[0123] Then, if Fig. 9 As shown, the analysis unit 34 sets the value of the third impedance corresponding to the resonance point input from the impedance measuring device 32 as the parasitic resistance component R′ between the other end of the negative electrode side of the plurality of solar power generation units 13a connected in series in the solar cell string 10 and the frame 13d. frame In the case where the impedance measurement process in step S42 is an initial measurement after the degradation diagnosis device 30 is installed, the initial value R′ of the parasitic series resistance component is frame0 The data is recorded in a storage device such as a semiconductor memory (S43), and the diagnosis of the initial measurement is completed.

[0124] Here, the parasitic resistance component R' frame For example, the frequency characteristics of the third impedance between the other end of the negative electrode side of the plurality of solar power generation units 13a connected in series in the solar cell string 10 and the frame 13d are measured between 1kHz and 1MHz, and the impedance value at the resonance point where the obtained impedance becomes the minimum value is set as the parasitic resistance component R' of the solar cell string 10. frame .

[0125] After the initial determination, Fig. 9 As shown, the analysis unit 34 sets the value of the third impedance corresponding to the resonance point input from the impedance measuring device 32 as the parasitic resistance component R′ between the other end of the negative electrode side of the plurality of solar power generation units 13a connected in series in the solar cell string 10 and the frame 13d. frameThe parasitic resistance component R′ between the other end of the negative electrode side of the plurality of solar power generation units 13a connected in series in the solar cell string 10 and the frame 13d is frame From the initial value R' frame0 The third increment ΔR' frame =R' frame -R' frame0 Calculation is performed (S44).

[0126] Then, the analysis unit 34 calculates the third increase ΔR′ calculated in the third analysis step. frame The signal is output to the degradation determination unit 36 ​​.

[0127] Next, when the third analysis step is completed, the second degradation determination step is performed.

[0128] First, if Fig. 9 As shown, the degradation determination unit 36 ​​determines the first increase ΔR calculated in the first analysis step and the third analysis step based on the first increase ΔR. s and the third increment ΔR' frame , for parameter X' = ΔR' frame / ΔR s Calculation is performed (S51).

[0129] Then, similarly to the first embodiment, since parameter X' is also a parameter depending on the position of solar cell module 13 in solar cell string 10, degradation determination unit 36 ​​identifies the second position of solar cell module 13 having increased resistance in solar cell string 10 based on parameter X' (S52).

[0130] Here, the parameter X' is a parameter that depends on the position of the solar cell module 13 in the solar cell string 10, but the relationship between the position of the solar cell module 13 and the value of the parameter X' is the same as Figure 5 Contrary to the parameter X, the parameter X' tends to increase from near 0 to 1 as the position of the solar cell module 13 moves from A to F. The slope direction of the parameter X' is opposite to that of the parameter X, but the principle is the same as that of the first embodiment, so the description is omitted.

[0131] Next, the first position of the solar cell module 13 with increased resistance determined in step S32 is compared with the second position of the solar cell module 13 with increased resistance determined in step S52. At this time, when the first position and the second position of the solar cell module 13 are the same, the position of the solar cell module 13 with increased resistance determined is directly output as the determination result (S53). On the other hand, when the first position and the second position of the solar cell module 13 are different from each other, since the determination result measured by the output terminals 11-1 and 11-2 close to the output terminal 11-1 on the positive side and the output terminal 11-2 on the negative side in the solar cell string 10 has high accuracy, the result of the position determination of the solar cell module 13 determined by them is output as a true determination result.

[0132] For example, it is assumed that in the first degradation determination step, the degradation determination unit 36 ​​determines that the first position of the solar cell module 13 with increased resistance is D, and in the second degradation determination step, the degradation determination unit 36 ​​determines that the second position of the solar cell module 13 with increased resistance is C. In this case, since the accuracy of the determination result measured by the output terminal 11-2 close to the output terminal 11-1 on the positive side and the output terminal 11-2 on the negative side in the solar cell string 10 is high, the degradation determination unit 36 ​​outputs the second position C of the solar cell module 13 determined in the second degradation determination step as a true determination result.

[0133] Therefore, the degradation diagnosis device for the solar cell string involved in this embodiment and the solar power generation system having the degradation diagnosis device can determine the position of the solar cell module that has been degraded in the solar cell string, and by using the measurement result obtained from the output terminal on the high-precision side as the judgment result, the position of the solar cell module that has been degraded can be accurately judged even when the number of solar cell modules connected in series is large.

[0134] In addition, since the degradation diagnosis device for the solar cell string and the solar power generation system having the degradation diagnosis device according to the present embodiment have the same structure and operation principle as those of the first embodiment, the degradation diagnosis device for the solar cell string and the solar power generation system having the degradation diagnosis device according to the present embodiment can determine the position of the solar cell module that has degraded in the solar cell string, as in the first embodiment, and thus can significantly reduce the time and workload required for fault diagnosis of the solar cell module in the solar cell string. In addition, the degradation diagnosis device for the solar cell string and the solar power generation system having the degradation diagnosis device according to the present embodiment can use a high-frequency signal in the measurement of the frequency characteristics of the impedance, and thus can diagnose the degradation of a large number of solar cell modules. In addition, since the degradation diagnosis can be performed at night, which is a time period when the power generation is sufficiently low 2 hours after sunset or 2 hours before sunrise, it is possible to suppress the reduction of the power generation of the solar power generation of the entire solar power generation system for the purpose of degradation diagnosis.

[0135] Here, in this embodiment, the second analysis process is performed after the first analysis process, and then the third analysis process is performed, but the timing of performing each analysis process can be changed in various ways. In addition, in this embodiment, the second degradation determination process is performed after the first degradation determination process, but the parameter X' may be calculated first and the resistance increase position may be determined, or the parameter X and the parameter X' may be calculated at the same time and each resistance increase position may be determined.

[0136] Implementation method 3.

[0137] The solar power generation system and degradation diagnosis device for a solar cell string according to the present embodiment differ from the second embodiment in that the degradation determination unit determines that the resistance of the plurality of solar cell modules in the solar cell string has increased based on the calculated parameters X and X′.

[0138] The schematic configuration of the solar power generation system and the degradation diagnosis device for the solar cell string according to the present embodiment is similar to that of the first embodiment. Figure 1 And implementation method 2 Figure 8 Similarly, description of the same configuration other than the characteristic portion of the degradation determination unit 36 ​​of the present embodiment will be omitted.

[0139] Next, the operation of the solar power generation system 100 and the degradation diagnosis device 30 for the solar cell string 10 according to the present embodiment will be described. Fig.10 2 is a flowchart showing the operation of the degradation diagnosis device 30 according to the present embodiment. Fig. 9The parts with the same reference numerals are the same as those in Implementation Example 2, and thus detailed descriptions are omitted, and only the differences from Implementation Example 2 are described.

[0140] Regarding the operation of the degradation diagnosis device 30 of the solar power generation system 100 and the solar cell string 10 involved in this embodiment, the first analysis process, the second analysis process, the first degradation judgment process, the third analysis process and the second degradation judgment process up to step S52 are the same as those in the second embodiment.

[0141] Thereafter, the position of the solar cell module 13 with increased resistance determined in step S32 is compared with the position of the solar cell module 13 with increased resistance determined in step S52. At this time, when the positions of the solar cell modules 13 are the same, the position of the solar cell module 13 with increased resistance determined is directly output as the determination result (S53). On the other hand, when the positions of the solar cell modules 13 are different from each other, it is thought that there is not one solar cell module 13 with increased resistance in the solar cell string 10, so the degradation determination unit 36 ​​determines that the resistance of the plurality of solar cell modules 13 in the solar cell string 10 has increased, and outputs the result (S54a).

[0142] For example, it is assumed that in the first degradation determination step, the degradation determination unit 36 ​​determines that the position of the solar cell module 13 with increased resistance is D, and in the second degradation determination step, the degradation determination unit 36 ​​determines that the position of the solar cell module 13 with increased resistance is A. In this case, it is thought that there is not one solar cell module 13 with increased resistance in the solar cell string 10, so the degradation determination unit 36 ​​determines that the resistance of the plurality of solar cell modules 13 in the solar cell string 10 has increased, and outputs this result.

[0143] Thus, the degradation diagnosis device for a solar cell string according to the present embodiment and the solar power generation system having the degradation diagnosis device can determine that the resistance of the plurality of solar cell modules 13 in the solar cell string 10 has increased and output the result, thereby being able to communicate the progress of degradation in the plurality of solar cell modules to the user. In addition, the user can grasp the degradation status in detail including the degradation status of the plurality of solar cell modules.

[0144] In addition, since the degradation diagnosis device for the solar cell string and the solar power generation system having the degradation diagnosis device according to the present embodiment have the same structure and operation principle as those of the first embodiment, the degradation diagnosis device for the solar cell string and the solar power generation system having the degradation diagnosis device according to the present embodiment can determine the position of the solar cell module that has degraded in the solar cell string, as in the first embodiment, and thus can significantly reduce the time and workload required for fault diagnosis of the solar cell module in the solar cell string. In addition, the degradation diagnosis device for the solar cell string and the solar power generation system having the degradation diagnosis device according to the present embodiment can use a high-frequency signal in the measurement of the frequency characteristics of the impedance, and thus can diagnose the degradation of a large number of solar cell modules. In addition, since the degradation diagnosis can be performed at night, which is a time period when the power generation is sufficiently low 2 hours after sunset or 2 hours before sunrise, it is possible to suppress the reduction of the power generation of the solar power generation of the entire solar power generation system for the purpose of degradation diagnosis.

[0145] Implementation method 4.

[0146] The degradation diagnosis device for the solar power generation system and solar cell string of the present embodiment is different from the first embodiment in that the resistance increase of each solar cell module that changes over time is recorded, and the degraded solar cell module is identified based on the accumulated resistance increase value of each solar cell module.

[0147] The schematic configuration of the solar power generation system and the degradation diagnosis device for the solar cell string according to the present embodiment is similar to that of the first embodiment. Figure 1 Similarly, the same structure other than the characteristic parts of the analysis unit 34 and the degradation determination unit 36 ​​of this embodiment is omitted. In addition, the general structure of the inside of the connection box of the degradation diagnosis device for the solar power generation system and the solar cell string involved in this embodiment is also the same as that of the first embodiment, so the detailed description is omitted.

[0148] The degradation diagnosis device for the solar power generation system and solar cell string of the present embodiment records the resistance increase of each solar cell module that changes over time, and identifies the degraded solar cell module based on the accumulated resistance increase value of each solar cell module.

[0149] Although the details will be described later, the analysis unit 34 sets the value of the first impedance corresponding to the resonance point input from the impedance measuring device 32 as the parasitic series resistance component R between one end and the other end of the plurality of solar power generation units 13a connected in series in the solar cell string 10. s(k) The series resistance component between one end and the other end of the plurality of solar power generation units 13a connected in series in the solar cell string 10 is then measured from the previous measured value R s The fourth increment ΔR from (k-1) s (k) = R s (k)-R s (k-1) is calculated.

[0150] The analyzing unit 34 sets the value of the second impedance corresponding to the resonance point input from the impedance measuring device 32 as the parasitic resistance component R between one end of the plurality of solar power generating units 13a connected in series in the solar cell string 10 and the frame 13d. frame (k) The parasitic resistance component between one end of the plurality of solar power generating units 13a connected in series and the frame 13d of the solar cell string 10 is then measured from the previous measurement value R frame The fifth increment ΔR from (k-1) frame (k) = R frame (k)-R frame (k-1) is calculated.

[0151] Then, the analyzing unit 34 calculates the fourth increment ΔR s (k) and the fifth increment ΔR frame (k) Output to the degradation determination unit 36.

[0152] The degradation determination unit 36 ​​calculates the fourth increase ΔR calculated by the analysis unit 34 based on the fourth increase ΔR. s (k) and the fifth increment ΔR frame (k) The position of the solar cell module 13 where the resistance in the solar cell string 10 is increased is determined.

[0153] Although the details will be described later, the degradation determination unit 36 ​​uses the fourth increase ΔR calculated by the analysis unit 34 s (k) and the fifth increment ΔR frame (k), the parameter X(k) which depends on the position where the resistance in the solar cell string 10 is increased is X(k)=ΔR frame (k) / ΔR s Then, the degradation determination unit 36 ​​specifies the position of the solar cell module 13 in the solar cell string 10 where the resistance value has increased, based on the calculated parameter X(k).

[0154] Then, the degradation determination unit 36 ​​calculates the series resistance value R of the solar cell module 13 at the location where the resistance increase has occurred. sy Add the 4th increment ΔR s(k) and recorded in a storage device such as a semiconductor memory.

[0155] Next, the operation of the solar power generation system 100 and the degradation diagnosis device 30 for the solar cell string 10 according to the present embodiment will be described. Fig.11 2 is a flowchart showing the operation of the degradation diagnosis device 30 according to the present embodiment. Figure 3 The parts with the same reference numerals are the same as those in Embodiment 1, and thus detailed descriptions thereof are omitted, and only the differences from Embodiment 1 are described.

[0156] First, when degradation diagnosis device 30 starts diagnosis of solar cell string 10 for the kth time, solar cell string 10 is disconnected from the unillustrated power transmission cable and power conditioner for solar power generation through a switching unit such as an unillustrated switch in connection box 20 and connected to degradation diagnosis device 30 .

[0157] Then, if Fig.11 As shown in FIG. 1 , when the k-th diagnosis of the solar cell string 10 is started, the fourth analysis step is performed.

[0158] First, if Fig.11 As shown, the switch 24 of the connection box 20 is turned on, and the output terminal of the terminal box 13c on the negative electrode side of the solar cell string 10 is electrically connected to the outer conductor 46 of the coaxial cable 40 and the ground terminal of the impedance meter 32. Then, the switch 28 of the connection box 20 is turned off, and the frame 13d of the solar cell module 13 is electrically insulated from the ground terminal of the impedance meter 32 (S11).

[0159] Then, if Fig.11 As shown in FIG. 1 , in a state where the switch 24 is turned on and the switch 28 is turned off, the impedance measuring device 32 measures the frequency characteristics of the first impedance between one end and the other end of the plurality of solar power generating units 13a connected in series in the solar cell string 10. Then, the resonance point of the first impedance is determined based on the measured frequency characteristics of the first impedance, and the value of the first impedance corresponding to the resonance point is output to the analysis unit 34 at the subsequent stage.

[0160] Then, if Fig.11 As shown, the analysis unit 34 sets the value of the first impedance corresponding to the resonance point input from the impedance measuring device 32 in the k-th diagnosis as the parasitic series resistance component R between one end and the other end of the plurality of solar power generating units 13a connected in series in the solar cell string 10. s (k), and is recorded in a storage device such as a semiconductor memory (S12a). If the impedance measurement process in step S12a is the first measurement after the degradation diagnosis device 30 is installed, that is, the initial measurement, Fig.11As shown, the analysis unit 34 provides an initial value R of the parasitic series resistance component to the storage device such as the semiconductor memory. s (1) After recording, the process proceeds to step S21.

[0161] After the initial determination, Fig.11 As shown, the analyzing unit 34 calculates the previously measured value R of the parasitic series resistance component between one end and the other end of the plurality of solar power generating units 13a connected in series in the solar cell string 10. s (k-1) is set as the initial value, and the previous measured value R s The increment from (k-1) is the fourth increment ΔR s (k) = R s (k)-R s (k-1) is calculated, and the calculated fourth increment ΔR s (k) Output to the degradation determination unit 36 ​​(S14a).

[0162] Next, when the fourth analysis step is completed, the fifth analysis step is performed.

[0163] First, if Fig.11 As shown, the switch 24 of the connection box 20 is turned OFF, and the output terminal of the terminal box 13c on the negative side of the solar cell string 10 is electrically insulated from the external conductor 46 of the coaxial cable 40 and the ground terminal of the impedance meter 32. Then, the switch 28 of the connection box 20 is turned ON, and the frame 13d of the solar cell module 13 is electrically connected to the ground terminal of the impedance meter 32 (S21).

[0164] Then, if Fig.11 As shown in FIG. 1 , in a state where the switch 24 is turned OFF and the switch 28 is turned ON, the impedance measuring device 32 measures the frequency characteristics of the second impedance between one end of the positive electrode side of the plurality of solar power generating units 13a connected in series in the solar cell string 10 and the frame 13d of the solar cell module 13. Then, the resonance point of the second impedance is determined based on the measured frequency characteristics of the second impedance, and the value of the second impedance corresponding to the resonance point is output to the analysis unit 34 at the subsequent stage.

[0165] Then, if Fig.11 As shown, the analyzing unit 34 sets the value of the second impedance corresponding to the resonance point input from the impedance measuring device 32 in the k-th diagnosis as the parasitic resistance component R between one end of the plurality of solar power generating units 13a connected in series in the solar cell string 10 and the frame 13d. frame(k), and is recorded in a storage device such as a semiconductor memory (S22a). If the impedance measurement process in step S22a is the first measurement after the degradation diagnosis device 30 is installed, that is, the initial value R of the parasitic series resistance component is stored in the storage device such as a semiconductor memory. frame (1) Recording is performed and the diagnosis of the initial measurement is completed.

[0166] After the initial determination, Fig.11 As shown, the analysis unit 34 calculates the previously measured value R of the parasitic resistance component between one end of the plurality of solar power generating units 13a connected in series and the frame 13d of the solar cell string 10. frame (k-1) is set as the initial value, and the previous measured value R frame The increment from (k-1) is the fifth increment ΔR frame (k) = R frame (k)-R frame (k-1) is calculated, and the calculated fifth increment ΔR frame (k) Output to the degradation determination unit 36. (S24a).

[0167] Next, when the fifth analysis step is completed, the third degradation determination step is performed.

[0168] First, if Fig.11 As shown, the degradation determination unit 36 ​​determines the fourth increase ΔR calculated in the fourth analysis step and the fifth analysis step based on the fourth increase ΔR. s (k) and the fifth increment ΔR frame (k), for parameter X(k) = R frame Δ(k) / ΔR s (k) Perform calculations.

[0169] Since the parameter X(k) depends on the position of the solar cell module 13 in the solar cell string 10, the degradation determination unit 36 ​​specifies the solar cell module 13 having an increased resistance value in the solar cell string 10 based on the parameter X(k) (S32a).

[0170] Then, if Fig.11 As shown, the series resistance value R of the solar cell module 13 at the resistance increase position y determined as the resistance value increase based on the parameter X(k) is sy Add ΔR s (k), as the series resistance value R of the solar cell module 13 at the resistance increase position y sy , recorded in a storage device such as a semiconductor memory (S33). The series resistance value R of the solar cell module 13 at the resistance increase position y syFor the next and subsequent diagnosis, after the initial measurement, each time the diagnosis is performed, the recorded series resistance value R of each solar cell module 13 is sent to the user. sy Accumulate the 4th increment ΔR s (k).

[0171] Here, the initial series resistance value R of each solar cell module 13 is sy The resistance value R can be obtained before the initial measurement and recorded in a storage device such as a semiconductor memory. Alternatively, the initial resistance value of all solar cell modules 13 in the solar cell string 10 can be assumed to be the same, and the series resistance value R obtained by the initial measurement can be recorded in a storage device such as a semiconductor memory. s (1) The value obtained by dividing by the number of solar cell modules 13 is used as the initial series resistance value R sy .

[0172] Here, the parameter X(k) is different from other embodiments in that it is not an initial value measured by initial measurement, but a fourth increment ΔR obtained based on the previous measurement value. s (k) and the fifth increment ΔR frame (k) is calculated. Therefore, the parameter X(k) is affected by the change in the resistance value of each solar cell module 13 whose resistance increases with the passage of time. Compared with the parameter X obtained from the initial value in the first embodiment, the slope and the like may change with the passage of time, and the position of the solar cell module 13 whose resistance increases may not be accurately determined. In the present embodiment, in order to cope with such a change in the parameter X(k) with the passage of time, in the step of determining the position of the solar cell module 13 whose resistance increases in step S32a, the relationship between the parameter X(k) in the kth diagnosis and the position of the solar cell module 13 whose resistance increases can be corrected in advance based on the series resistance value of each solar cell module 13 added and recorded so far, and the solar cell module 13 having the increased resistance value can be determined based on the relationship between the corrected parameter X(k) and the position of the solar cell module 13 whose resistance increases.

[0173] Here, the correction of the relationship between the parameter X(k) and the position of the solar cell module 13 with increased resistance does not need to be performed every time the diagnosis is performed. The correction of the relationship between the parameter X(k) and the position of the solar cell module 13 with increased resistance can be performed based on the accumulated resistance increase of the solar cell module 13, or the correction of the relationship between the parameter X(k) and the position of the solar cell module 13 with increased resistance can be performed in units of a specified number of diagnostic times.

[0174] In the degradation diagnosis device 30 for a solar cell string and the solar power generation system 100 having the degradation diagnosis device as described above, the accumulated series resistance value R of one solar cell module 13 in the solar cell string 10 is sy When the value exceeds a predetermined threshold, the degradation determination unit 36 ​​can determine that the resistance has increased due to degradation of the power generation layer in the solar cell unit of a solar cell module 13 or corrosion of the electrode portion, for example, and notify the user of the location of the solar cell module 13 where the resistance value has increased.

[0175] Here, in the present embodiment, the fifth analysis step is performed after the fourth analysis step is performed, but the fourth analysis step may be performed after the fifth analysis step is performed.

[0176] In this embodiment, the series resistance value R of the solar cell module 13 is sy Add ΔR s (k), based on the cumulative series resistance value R sy , the solar cell module 13 having an increased resistance value is identified, but it is also possible to calculate the ΔR s The integrated value of (k) is recorded, and the integrated value is compared with a threshold value to identify the solar cell module 13 having an increased resistance value, and the user is notified.

[0177] Therefore, the degradation diagnosis device for the solar cell string involved in this embodiment and the solar power generation system having the degradation diagnosis device can determine the position of the solar cell module that has degraded in the solar cell string, and can record the resistance increase of each solar cell module that changes with the passage of time, and estimate the cumulative resistance increase value of each solar cell module.

[0178] Therefore, compared with the first embodiment, the position of the degraded solar cell module in the solar cell string can be accurately identified, and the time and workload required for fault diagnosis of the solar cell module in the solar cell string can be further reduced.

[0179] In addition, since the present embodiment has the same structure and operating principle as the first embodiment, the degradation diagnosis device for the solar cell string and the solar power generation system having the degradation diagnosis device according to the present embodiment can determine the position of the solar cell module that has degraded in the solar cell string, similarly to the first embodiment, and thus can significantly reduce the time and workload required for fault diagnosis of the solar cell module in the solar cell string. In addition, the degradation diagnosis device for the solar cell string and the solar power generation system having the degradation diagnosis device according to the present embodiment can use a high-frequency signal in the measurement of the frequency characteristics of the impedance, and thus can diagnose the degradation of a large number of solar cell modules. In addition, since the degradation diagnosis can be performed at night, which is a time period when the power generation is sufficiently low 2 hours after sunset or 2 hours before sunrise, it is possible to suppress the reduction of the power generation of the solar power generation of the entire solar power generation system for the purpose of degradation diagnosis.

[0180] Here, this embodiment can also be applied to Embodiment 2 and Embodiment 3. That is, the resistance component between the other end of the negative electrode side of the plurality of solar power generation units 13a connected in series in the solar cell string 10 and the frame 13d can be used to calculate the k-th R value based on the previous measurement value as in this embodiment. s and R frame In this case, based on the calculated parameters X(k) and X'(k), the position of the solar cell module 13 having increased resistance in the solar cell string 10 can be more accurately determined, and the time and workload required for fault diagnosis of the solar cell module in the solar cell string can be further reduced.

[0181] In addition, the present invention can freely combine various embodiments within the scope of the invention, and appropriately deform or omit each embodiment. Moreover, the present invention is not limited to the above-mentioned embodiments, and various deformations can be made in the implementation stage without departing from the scope of its purpose. In addition, the above-mentioned embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining the disclosed multiple structural conditions.

[0182] Description of the label

[0183] 10 solar cell string, 13 solar cell module, 20, 20a connection box, 30 degradation diagnosis device, 32 impedance measuring device, 34 analysis unit, 36 degradation determination unit, 100 solar power generation system

Claims

1. A degradation diagnosis device for a solar cell string, the solar cell string having a plurality of solar cell modules, the solar cell modules having a solar power generation unit and a conductive frame, the solar power generation units of the plurality of solar cell modules being electrically connected in series, and the frames of the plurality of solar cell modules being electrically connected in common, The degradation diagnosis device for a solar cell string is characterized by comprising: an impedance measuring device for measuring a frequency characteristic of a first impedance between one end and the other end of the plurality of solar power generating units connected in series in the solar cell string, and for measuring a frequency characteristic of a second impedance between one end of the plurality of solar power generating units connected in series in the solar cell string and the frame; an analyzing unit that calculates a first increase from an initial value of a series resistance component between one end and the other end of the plurality of solar power generating units connected in series of the solar cell string based on the frequency characteristics of the first impedance, and calculates a second increase from an initial value of a resistance component between one end of the plurality of solar power generating units connected in series of the solar cell string and the frame based on the frequency characteristics of the second impedance; and a degradation determination unit that determines a position of a solar cell module having increased resistance within the solar cell string based on the first increase and the second increase calculated by the analysis unit, When the first increment is set to ΔR s , the second increment is set to ΔR frame hour, The analysis part is about ΔR frame / ΔR s Calculate the value of The degradation determination unit is based on the ΔR frame / ΔR s The position of the solar cell module where the resistance in the solar cell string increases is determined based on the value of 2. The degradation diagnosis device for a solar cell string according to claim 1, characterized in that: The initial value of the series resistance component and the initial value of the resistance component are values ​​at the time of initial measurement of the solar cell string.

3. The degradation diagnosis device for a solar cell string according to claim 1, characterized in that: The impedance measuring device measures the frequency characteristics of the third impedance between the other ends of the plurality of solar power generating units connected in series in the solar cell string and the frame. The analyzing unit calculates a third increase from an initial value of a resistance component between the other ends of the plurality of solar power generating units connected in series in the solar cell string and the frame based on the frequency characteristics of the third impedance, The degradation determination unit determines a position of the solar cell module where the resistance in the solar cell string increases based on the first increase, the second increase, and the third increase calculated by the analysis unit. When the third increment is set to ΔR' frame hour, The analysis part is about ΔR' frame / ΔR s Calculate the value of The degradation determination unit is based on the ΔR frame / ΔR s The value of ΔR' frame / ΔR s The position of the solar cell module where the resistance in the solar cell string increases is determined based on the value of 4. The degradation diagnosis device for a solar cell string according to claim 3, characterized in that: The degradation determination unit is based on the ΔR frame / ΔR s The first position of the solar cell module where the resistance in the solar cell string increases is determined based on the ΔR' frame / ΔR s The second position of the solar cell module where the resistance in the solar cell string increases is determined based on the value of , and when the first position and the second position are different from each other, the solar cell module close to the output terminal used in the measurement is determined as the solar cell module where the resistance increases.

5. The degradation diagnosis device for a solar cell string according to claim 3 or 4, characterized in that: The degradation determination unit is based on the ΔR frame / ΔR s The first position of the solar cell module where the resistance in the solar cell string increases is determined based on the ΔR' frame / ΔR s The second position of the solar cell module where the resistance in the solar cell string increases is determined based on the value of , and when the first position and the second position are different from each other, it is determined that the resistance of the plurality of solar cell modules in the solar cell string increases.

6. The degradation diagnosis device for a solar cell string according to claim 1, characterized in that: The initial value of the series resistance component and the initial value of the resistance component are the series resistance component and the resistance component of the solar cell string measured last time, The analyzing unit calculates the first increment and the second increment based on the series resistance component and the resistance component of the solar cell string measured the last time, The degradation determination unit adds the first increment to a previously measured series resistance value of the solar cell module at a position determined based on the first increment and the second increment, and records the result.

7. The degradation diagnosis device for a solar cell string according to claim 1, characterized in that: The initial value of the series resistance component and the initial value of the resistance component are the series resistance component and the resistance component of the solar cell string measured last time, The analyzing unit calculates the first increment and the second increment based on the series resistance component and the resistance component of the solar cell string measured the last time, The degradation determination unit adds the first increment to a previously measured series resistance value of the solar cell module at a position determined based on the first increment and the second increment, and records the result.

8. The degradation diagnosis device for a solar cell string according to claim 3, characterized in that: The initial value of the series resistance component and the initial value of the resistance component are the series resistance component and the resistance component of the solar cell string measured last time, The analyzing unit calculates the first increment and the second increment based on the series resistance component and the resistance component of the solar cell string measured the last time, The degradation determination unit adds the first increment to a previously measured series resistance value of the solar cell module at a position determined based on the first increment and the second increment, and records the result.

9. The degradation diagnosis device for a solar cell string according to claim 3, characterized in that: The initial value of the series resistance component and the initial value of the resistance component are the series resistance component and the resistance component of the solar cell string measured last time, The analyzing unit calculates the first increment and the second increment based on the series resistance component and the resistance component of the solar cell string measured the last time, The degradation determination unit adds the first increment to a previously measured series resistance value of the solar cell module at a position determined based on the first increment and the second increment, and records the result.

10. The degradation diagnosis device for a solar cell string according to claim 4, characterized in that: The initial value of the series resistance component and the initial value of the resistance component are the series resistance component and the resistance component of the solar cell string measured last time, The analyzing unit calculates the first increment and the second increment based on the series resistance component and the resistance component of the solar cell string measured the last time, The degradation determination unit adds the first increment to a previously measured series resistance value of the solar cell module at a position determined based on the first increment and the second increment, and records the result.

11. The degradation diagnosis device for a solar cell string according to claim 5, characterized in that: The initial value of the series resistance component and the initial value of the resistance component are the series resistance component and the resistance component of the solar cell string measured last time, The analyzing unit calculates the first increment and the second increment based on the series resistance component and the resistance component of the solar cell string measured the last time, The degradation determination unit adds the first increment to a previously measured series resistance value of the solar cell module at a position determined based on the first increment and the second increment, and records the result.

12. A solar power generation system, characterized in that: have: The degradation diagnosis device for the solar cell string according to any one of claims 1 to 11; and The solar cell string has the plurality of solar cell modules, each of which has the solar power generation unit and the conductive frame. The solar power generation units of the plurality of solar cell modules are electrically connected in series, and the plurality of frames of the plurality of solar cell modules are electrically connected in common.

13. A method for diagnosing degradation of a solar cell string, using a device for diagnosing degradation of a solar cell string, wherein the solar cell string has a plurality of solar cell modules, each solar cell module having a solar power generation unit and a conductive frame, wherein the solar power generation units of the plurality of solar cell modules are electrically connected in series, and the frames of the plurality of solar cell modules are electrically connected in common, The degradation diagnosis method of a solar cell string is characterized by comprising the following steps: Using the degradation diagnosis device, measuring the frequency characteristics of a first impedance between one end and the other end of the plurality of solar power generating units connected in series in the solar cell string, and measuring the frequency characteristics of a second impedance between one end of the plurality of solar power generating units connected in series in the solar cell string and the frame; Using the degradation diagnosis device, a first increase from an initial value of a series resistance component between one end and the other end of the plurality of solar power generating units connected in series of the solar cell string is calculated based on the frequency characteristics of the first impedance, and a second increase from an initial value of a resistance component between one end of the plurality of solar power generating units connected in series of the solar cell string and the frame is calculated based on the frequency characteristics of the second impedance; and Using the degradation diagnosis device, based on the calculated first increment and second increment, a position of a solar cell module having increased resistance in the solar cell string is determined; When the first increment is set to ΔR s , the second increment is set to ΔR frame hour, The degradation diagnosis device is used to determine ΔR frame / ΔR s Calculate the value of The degradation diagnosis device is based on the ΔR frame / ΔR s The position of the solar cell module where the resistance in the solar cell string increases is determined based on the value of 14. A degradation diagnosis device for a battery string, the battery string having a plurality of battery modules, the battery modules having a plurality of battery cells and a conductive frame, the plurality of battery modules being electrically connected in series, the frames of the plurality of battery modules being electrically connected in common, The battery string degradation diagnosis device is characterized by having: an impedance measuring device for measuring a frequency characteristic of a first impedance between one end and the other end of the plurality of battery modules connected in series in the battery string, and for measuring a frequency characteristic of a second impedance between one end of the plurality of battery modules connected in series in the battery string and the frame; an analyzing unit that calculates a first increase from an initial value of a series resistance component between one end and the other end of the plurality of battery modules connected in series in the battery string based on the frequency characteristics of the first impedance, and calculates a second increase from an initial value of a resistance component between one end of the plurality of battery modules connected in series in the battery string and the frame based on the frequency characteristics of the second impedance; and A degradation determination unit determines a position of a battery module whose resistance in the battery string increases based on the first increase and the second increase calculated by the analysis unit, and determines the position of the battery module whose resistance in the battery string increases based on the first increase and the second increase calculated by the analysis unit, and determines the position of the battery module whose resistance in the battery string increases based on the first increase as ΔR s , the second increment is set to ΔR frame hour, The analysis part is about ΔR frame / ΔR s Calculate the value of The degradation determination unit is based on the ΔR frame / ΔR s The position of the battery module where the resistance in the battery string increases is determined based on the value of 15. A method for diagnosing degradation of a battery string, using a device for diagnosing degradation of a battery string, wherein the battery string has a plurality of battery modules, the battery modules have a plurality of battery cells and a conductive frame, the plurality of battery modules are electrically connected in series, and the frames of the plurality of battery modules are electrically connected in common, The battery string degradation diagnosis method is characterized by comprising the following steps: Using the degradation diagnosis device, measuring a frequency characteristic of a first impedance between one end and the other end of the plurality of battery modules connected in series in the battery string, and measuring a frequency characteristic of a second impedance between one end of the plurality of battery modules connected in series in the battery string and the frame; Using the degradation diagnosis device, calculating a first increase from an initial value of a series resistance component between one end and the other end of the plurality of battery modules connected in series in the battery string based on the frequency characteristics of the first impedance, and calculating a second increase from an initial value of a resistance component between one end of the plurality of battery modules connected in series in the battery string and the frame based on the frequency characteristics of the second impedance; and Using the degradation diagnosis device, based on the calculated first increase and second increase, a position of a battery module having increased resistance in the battery string is determined; When the first increment is set to ΔR s , the second increment is set to ΔR frame hour, The degradation diagnosis device is used to determine ΔR frame / ΔR s Calculate the value of The degradation diagnosis device is based on the ΔR frame / ΔR s The position of the battery module where the resistance in the battery string increases is determined based on the value of

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