JP2020022365A - Deterioration determination method and deterioration determination device for solar cell module - Google Patents

Abstract

To provide a deterioration determination method and a deterioration determination device for a solar cell module capable of determining a deteriorated solar cell module, in a state where the solar cell module is connected with a solar cell string.SOLUTION: In a case where reference I-V characteristics has an active region of a bypass diode 4c, a determination index is defined as a potential difference between a voltage value at an intersection point of a straight line obtained with a voltage value and a current value in a linear region of shading I-V characteristics to a voltage axis and a voltage value at an intersection point of a straight line obtained with a voltage value and a current value in a linear region of the reference I-V characteristics to the voltage axis. In a case where the reference I-V characteristics has no active region of the bypass diode 4c, the determination index is defined as a potential difference between a voltage value at an intersection point of a straight line obtained with a voltage value and a current value at a measuring point belonging to the linear region of the shading I-V characteristics to the voltage axis and a voltage value at an intersection point for the reference I-V characteristics to the voltage axis. The deterioration determination method and deterioration determination device 10 for a solar cell module determines that there is a determination when the determination index is within a determination range.SELECTED DRAWING: Figure 10

Description

  The present invention provides a solar power generation system in which a solar cell string configured by electrically connecting a plurality of solar cell modules in series is connected to a power system by a power conditioner. The present invention relates to a method and an apparatus for determining deterioration of a solar cell module for determining a solar cell module that has deteriorated (function deterioration such as failure or power generation failure) from the solar cell module.

  In recent years, with the background of social trends toward post-nuclear power plants, the construction of new nuclear power plants is becoming more difficult, and existing nuclear power plants have a long service life. Utilization is an urgent issue at the national policy level. In particular, the introduction of a photovoltaic power generation system using sunlight as one of renewable energy is rapidly progressing.

  The photovoltaic power generation system includes a plurality of sets of photovoltaic strings in units of a photovoltaic string in which a plurality of photovoltaic modules are electrically connected in series, and is connected to one connection box for each set of photovoltaic strings. The power generator is connected to a power system such as a commercial power supply by a power conditioner (power conversion device) through the connection box.

  In this type of photovoltaic power generation system, when the solar cell module is deteriorated due to long-term use, the output power is reduced. Therefore, means for detecting deterioration of the solar cell module is required. Since the solar cell module has a structure in which materials with different coefficients of thermal expansion, such as semiconductors and metals, are electrically bonded, the function gradually deteriorates in the long term due to the thermal stress caused by repeated cold and warm every day or night or season. The members may be suddenly damaged due to lightning, storms, etc., and it is inevitable that such factors cause power generation failure in the entire solar cell module.

  2. Description of the Related Art Conventionally, as a means for detecting deterioration of a solar cell module, a solar cell string inspection device that specifies a solar cell string including a deteriorated solar cell module is known (for example, see Patent Document 1).

  This solar cell string inspection apparatus includes a characteristic measuring unit that measures an IV characteristic (IV curve) from output power of a solar cell string to be inspected, and an index based on the IV characteristic measured by the characteristic measuring unit. , A comparison monitoring unit that compares the calculated index with a preset threshold value, and a display recording unit that displays and records the result of comparison between the index and the threshold value.

JP 2012-16953 A

  By the way, in the solar cell string inspection device disclosed in Patent Document 1 described above, an abnormal solar cell string is identified without depending on time-lapse data in a solar cell panel whose output has been reduced due to deterioration of a solar cell module. Can be.

  However, the solar cell string inspection device of Patent Literature 1 has a problem that a deteriorated solar cell module cannot be determined from a plurality of solar cell modules constituting a solar cell string.

  A solar cell string is configured by electrically connecting a plurality of solar cell modules in series.To determine a solar cell module that has failed or deteriorated in function, and to identify the failure type and deterioration level, From the viewpoint of work efficiency, it is desirable that inspection can be performed without separating each solar cell module.

  On the other hand, a solar cell module includes a cell string in which a large number of solar cells are electrically connected in series, and a bypass diode (BPD) provided on a path on which a generated current bypasses the cell string when the cell string fails to generate power. ) Is formed as a unit, and a plurality of clusters are electrically connected in series with each other as a unit. However, these solar cell module components have failures and functional deterioration due to various factors. For example, in the case of a cluster, the power generation capacity of the cell string is significantly reduced due to the disconnection of the conductive wire (bus par) of the cell, the disconnection of the cluster due to solder cracks, etc., and the high resistance of the cluster caused by the chemical modification of the material of the cell. Or lose. On the other hand, in bypass diodes, a bypass diode short-circuit failure occurs when the bypass diode is damaged due to lightning, etc., causing a short circuit, and a bypass diode open failure in which conductivity is lost due to thermal damage due to long-term generation of current flowing through the bypass diode. There is. There are various other factors such as deterioration and peeling of the filling resin and electrode corrosion due to water penetration.

  Until now, the solar cell module was separated from the solar cell string, the IV characteristics of each solar cell module were measured, and the power generation performance of the solar cell module was evaluated. However, if a solar cell module having a power generation failure exists in the solar cell string, the IV characteristics of the entire solar cell string, that is, the shape of the IV curve, change in a complicated manner. It is possible to determine a deteriorated solar cell module without separating the solar cell module from the solar cell string, and to find and determine failures and functional deterioration of its components (clusters, bypass diodes) by a simple method and operation. It was difficult.

  The present invention has been proposed in view of the above-described problems, and an object of the present invention is to provide a solar cell module capable of determining a deteriorated solar cell module while the solar cell module is connected to the solar cell string. It is an object of the present invention to provide a battery module deterioration determination method and a deterioration determination device.

  A method for determining deterioration of a solar cell module according to the present invention is a method for determining deterioration of a solar cell module that determines the deteriorated solar cell module from a solar cell string in which a plurality of solar cell modules are connected in series. The reference IV characteristic of the solar cell string in a state where all the solar cell modules are not shielded from light is measured, and one of the solar cell modules selected from a plurality of the solar cell modules is connected to the conductive path of the solar cell module. The solar cell module is shielded from light so as to pass through a bypass diode provided in each of the plurality of clusters constituting the solar cell module, and the light-shielding IV characteristic of the solar cell string in the light-shielded state is measured. When the V characteristic has an operation region of the bypass diode, the light shielding I The voltage value at the point where a straight line obtained by the least square method using the voltage value and the current value of at least two measurement points belonging to a linear region extending from the operating point of the bypass diode to the low voltage side of the V characteristic intersects the voltage axis. A straight line obtained by the least squares method using the voltage value and the current value of at least two measurement points belonging to a linear region extending from the operating point of the bypass diode having the reference IV characteristic to the low voltage side and intersects the voltage axis. A potential difference from a voltage value at a point is extracted as a determination index, and when the reference IV characteristic does not have an operating region of the bypass diode, the potential difference from the operating point of the bypass diode in the light-shielded IV characteristic is obtained. At the point where the straight line obtained by the least squares method using the voltage and current values of at least two measurement points belonging to the linear region extending to the low voltage side intersects the voltage axis A potential difference between a voltage value and a voltage value at a point intersecting the voltage axis of the reference IV characteristic is extracted as a determination index, and for each of the voltage values corresponding to the number of deteriorated clusters of the solar cell module on a one-to-one basis. Calculating a voltage range having a voltage value width equal to one cluster voltage value as a determination region, and determining that the solar cell module is deteriorated when the potential difference serving as the determination index is within the determination region. It is characterized by the following.

  The method for determining deterioration of a solar cell module according to the present invention, in the above configuration, when it is determined that the solar cell module has not deteriorated based on the determination index, the light-shielding IV characteristic is higher than the linear region. Based on a potential difference between a voltage value corresponding to a predetermined current value on the low voltage side and a voltage value corresponding to the predetermined current value of the reference IV characteristic, it is determined whether or not the current of the solar cell string has decreased. Is preferred.

  The deterioration determination device for a solar cell module according to the present invention is a deterioration determination device for a solar cell module that determines the deteriorated solar cell module from a solar cell string in which a plurality of solar cell modules are connected in series. A variable load resistor connected to both ends of the battery string, a current measuring unit for measuring a current value flowing through the solar cell string, and a voltage measurement for measuring a voltage value at a connection portion of the solar cell string with the variable load resistor And a reference IV characteristic of the solar cell string in a state where all of the plurality of solar cell modules are not shielded from light, and one solar cell module selected from the plurality of solar cell modules. Are provided in each of a plurality of clusters constituting the solar cell module. An IV characteristic measuring unit capable of measuring a light-shielded IV characteristic of the solar cell string in a state where light is shielded so as to be a path passing through the bypass diode; Is obtained by the least squares method using the voltage value and the current value of at least two measurement points belonging to a linear region extending from the operating point of the bypass diode to the low voltage side in the light-shielded IV characteristics. The voltage value at the point where the straight line intersects the voltage axis and the voltage value and the current value of at least two measurement points belonging to a linear region extending from the operating point of the bypass diode of the reference IV characteristic to the low voltage side. A potential difference from a voltage value at a point where a straight line obtained by the least squares method intersects the voltage axis is extracted as a judgment index, and the reference IV characteristic is obtained by the bypass filter. When there is no operating region of the diode, the minimum value is obtained by using the voltage value and the current value of at least two measurement points belonging to a linear region extending from the operating point of the bypass diode to the low voltage side of the light-shielded IV characteristic. The potential difference between the voltage value at the point where the straight line obtained by the square method intersects the voltage axis and the voltage value at the point where the reference IV characteristic intersects the voltage axis is extracted as a judgment index, and the deterioration of the solar cell module is determined. For each of the voltage values corresponding to the number of clusters on a one-to-one basis, a voltage range having a voltage value width equal to one cluster voltage value is calculated as a determination area, and the potential difference serving as the determination index is within the determination area. A deterioration determining unit that determines that the solar cell module is deteriorated in some cases.

  The deterioration determination device for a solar cell module according to the present invention, in the above-described configuration, when the deterioration determination unit determines that the solar cell module has not deteriorated based on the determination index, Based on a potential difference between a voltage value corresponding to a predetermined current value on the low voltage side of the linear region and a voltage value corresponding to the predetermined current value of the reference IV characteristic, a current drop of the solar cell string is reduced. Is preferably determined.

  Advantageous Effects of Invention According to the present invention, it is possible to provide a method and an apparatus for determining deterioration of a solar cell module that can determine a deteriorated solar cell module while the solar cell module is connected to the solar cell string.

It is explanatory drawing which shows the state which connected the deterioration determination apparatus of the solar cell module which is one Embodiment of this invention to the solar cell string to be measured. It is explanatory drawing which shows the structure of the solar cell module shown in FIG. FIG. 2 is a block diagram of the deterioration determination device for a solar cell module shown in FIG. 1. It is a figure which shows the standard IV characteristic of a solar cell string. It is explanatory drawing which shows the state in which a part of solar cell module to be discriminated was shielded from light by a light shielding plate. FIG. 5 is an explanatory diagram showing a procedure for determining the number of degraded clusters and the presence / absence of a current decrease of a solar cell module to be determined from a light-shielded IV characteristic and a reference IV characteristic according to the aspect of the first embodiment of the present invention. FIG. 4 is a diagram illustrating a processing diagram of measurement data in the first embodiment. FIG. 4 is a diagram illustrating a processing flow of measurement data in the first embodiment. FIG. 9 is a diagram illustrating a processing flow following the processing flow illustrated in FIG. 8. FIG. 11 is an explanatory diagram showing a procedure for determining the number of degraded clusters of a solar cell module to be determined from a light-shielded IV characteristic and a reference IV characteristic according to the second embodiment of the present invention. FIG. 11 is a diagram illustrating a processing diagram of measurement data in the second embodiment. FIG. 14 is a diagram illustrating a processing flow of measurement data in the second embodiment. FIG. 13 is a view illustrating a processing flow following the processing flow illustrated in FIG. 12; (A) is an explanatory view showing a current flow in a non-light-shielded state in a solar cell module in which a bypass diode has an open failure, and (b) is an explanatory diagram showing a current flow in a solar cell module in which a bypass diode has an open failure. FIG. 4 is a diagram showing a current flow of FIG. It is explanatory drawing which shows the light-shielding IV characteristic of the solar cell module in which a bypass diode has an open failure compared with the reference IV characteristic. It is a characteristic diagram which shows the example of the simulated IV characteristic. It is a figure showing the processing flow of the measurement data at the time of judging the open failure of the bypass diode. FIG. 18 is a diagram illustrating a processing flow following the processing flow illustrated in FIG. 17.

  Hereinafter, the present invention will be described more specifically with reference to the drawings.

  The solar power generation system 1 illustrated in FIG. 1 has a configuration in which a solar cell panel 2 is linked to a power system by a power conditioner (power conversion device: PCS) 3 including an inverter.

  The solar cell panel 2 has a solar cell string 5 in which eight solar cell modules 4 are connected in series as one unit, and the four sets of solar cell strings 5 are electrically connected in parallel inside the connection box 6. Thus, power is collected and electrically connected to the power conditioner 3 via the connection box 6. The connection box 6 includes four disconnectors 6a corresponding to the respective solar cell strings 5, and backflow prevention diodes 6b corresponding to the respective disconnectors 6a.

  The power conditioner 3 converts a direct current generated by the solar panel 2 into an alternating current and outputs the alternating current to a power system, and an MPPT (Maximum Power) so as to maximize the generated power of all the solar cell strings 5. Voltage is controlled by Point Tracking) method.

  As shown in FIG. 2, each solar cell module 4 has, as its internal configuration, ten solar cells (power generation elements) 4 a each arranged in two rows of five and electrically connected in series. Cluster 4d including the cell string 4b thus formed and a bypass diode (BPD) 4c provided on a current path bypassing the cell string 4b, and the respective clusters 4d are electrically connected to each other. Are connected in series. Note that, for convenience, in FIG. 2, only one solar cell 4a in each cell string 4b is denoted by a reference numeral.

  The bypass diode 4c has the same voltage across the portion where the power generation of the cell string 4b in the cluster 4d is relatively reduced due to uneven irradiation of sunlight to the cell string 4b due to a shadow or a failure. It operates when the voltage generated by the normally generating portion of the cell string 4b in the cell 4d becomes higher than the generated voltage and becomes equal to the forward voltage of the bypass diode 4c, and the generated current is bypassed to the cell string 4b. This is to avoid a hot spot from being generated in the cell string 4b by bypassing. Therefore, when the entire normal solar cell module 4 is uniformly irradiated with sunlight, the total electromotive force generated by the power generation of each solar cell 4a is equal to or higher than the forward voltage of the bypass diode 4c. As shown by a bold line, the generated current flows through each cell string 4b in order without passing through the bypass diode 4c.

  In the case shown in the figure, the solar cell panel 2 has a configuration in which four solar cell strings 5 are arranged in a plurality of rows in a vertical direction on the paper surface, but the number of the solar cell strings 5 constituting the solar cell panel 2 is the same. Is optional. Further, each of the solar cell strings 5 has a configuration in which eight solar cell modules 4 are connected in series, but the number of the solar cell modules 4 constituting the solar cell string 5 is also arbitrary. Furthermore, although the solar cell module 4 is configured to have three clusters 4d each including ten solar cells 4a, the number of the clusters 4d configuring the solar cell module 4 and the solar cells configuring the cluster 4d The number of cells 4a is also arbitrary.

  In the above-described solar power generation system 1, when the solar cell module 4 is deteriorated due to long-term use or the like, the output voltage of the solar cell panel 2 is reduced. Therefore, it is necessary to detect the deterioration of the solar cell module 4. . According to the deterioration determination method according to one embodiment of the present invention, the solar cell module 4 to be determined is separated from the solar cell string 5 from the solar cell string 5 in which the plurality of solar cell modules 4 are connected in series. It is possible to determine the deteriorated solar cell module 4 while being connected to the solar cell string 5.

  The deterioration determination method according to one embodiment of the present invention can be performed, for example, using the deterioration determination device 10 for a solar cell module according to one embodiment of the present invention having the configuration shown in FIG. The solar cell module deterioration determination device 10 includes an IV characteristic measurement unit 11 and a deterioration determination unit 12.

  When determining the deterioration of the solar cell module 4, as shown in FIG. 1, the solar cell string 5 including the solar cell module 4 to be subjected to the deterioration determination is disconnected from the power conditioner 3 by opening the disconnector 6a, An IV characteristic measuring unit 11 is connected to the solar cell string 5 via a disconnector 6a to form a closed loop.

  As shown in FIG. 3, the IV characteristic measuring unit 11 is connected in series to the variable load resistors 11 a connected to both ends of the conductive lines 5 a and 5 b of the solar cell string 5 and to the conductive line 5 b of the solar cell string 5. A current measuring unit 11b for measuring a current value flowing through the photovoltaic string 5; and a connection portion between both ends of the conductive wires 5a and 5b of the photovoltaic string 5 connected in parallel with the variable load resistor 11a. And a voltage measuring unit 11c for measuring the voltage value at The voltage value of the variable load resistor 11a is equal to the voltage across the solar cell string 5. As the variable load resistor 11a, for example, a semiconductor element such as an FET (Field Effect Transistor) is used.

  The IV characteristic measuring section 11 further includes a control section 11d. The control unit 11d can be configured by a microcomputer including, for example, a CPU (Central Processing Unit).

  The variable load resistor 11a is connected to the control unit 11d, and its operation is controlled by the control unit 11d to change the value of the load resistance. The current measurement unit 11b and the voltage measurement unit 11c are also connected to the control unit 11d, and the current value measured by the current measurement unit 11b and the voltage value measured by the voltage measurement unit 11c are input to the control unit 11d.

  The IV characteristic measuring unit 11 measures the current value and the voltage value of the solar cell string 5 while changing the value of the load resistance of the variable load resistor 11a, using the command from the deterioration determining unit 12 as a trigger, The IV characteristics of the solar cell string 5 can be measured. For example, the IV characteristic measuring unit 11 measures the current value and the voltage value of the solar cell string 5 while changing the value of the load resistance of the variable load resistance 11a in a state where all the plurality of solar cell modules 4 are not shaded. Thus, the reference IV characteristics of the solar cell string 5 can be measured. In addition, the IV characteristic measuring unit 11 sets one of the plurality of solar cell modules 4 selected from the plurality of solar cell modules 4 into a plurality of clusters 4 d in which the conductive path of the solar cell module 4 configures the solar cell module 4. By measuring the current value and the voltage value of the solar cell string 5 while changing the value of the load resistance of the variable load resistance 11a in a state where light is blocked so as to be a path via the bypass diode 4c provided in the The light-shielded IV characteristics of the solar cell string 5 can be measured. After measuring the IV characteristic of the solar cell string 5 as described above, the IV characteristic measuring unit 11 wirelessly transmits the measured data to the deterioration determining unit 12.

  Note that the IV characteristic generally means a current flowing through the solar cell module or the solar cell string and a load resistance at that time with respect to a predetermined resistance value of the variable load resistance connected to the solar cell module or the solar cell string. It is a relational expression obtained by measuring the voltage value while changing the resistance value, and is also called an IV curve (IV curve). Hereinafter, the “IV characteristic” may be referred to as “IV characteristic”.

  The deterioration determination unit 12 includes a control unit 12a. The control unit 12a can be configured by a microcomputer including, for example, a CPU (Central Processing Unit).

  Between the control unit 12a of the deterioration determination unit 12 and the control unit 11d of the IV characteristic measurement unit 11, data is wirelessly transmitted and received by the wireless interfaces 11e and 12b. As the wireless interfaces 11e and 12b, for example, specific low-power wireless stations can be used.

  The transmission and reception of data between the control unit 12a of the deterioration determination unit 12 and the control unit 11d of the IV characteristic measurement unit 11 are performed by wired communication instead of wireless communication using the wireless interfaces 11e and 12b. It can also be. In this case, the IV characteristic measuring unit 11 and the deterioration determining unit 12 can be configured as an integrated device.

  The deterioration determination unit 12 has a data storage unit 12c, and uses various data such as the IV characteristics transmitted from the control unit 11d of the IV characteristic measurement unit 11 to perform the deterioration of the solar cell module described below. Various data can be stored in the data storage unit 12c while performing the determination process. In addition, the deterioration determination unit 12 is input by the operator with a display unit 12d such as a monitor that displays various information such as IV characteristics (IV curves) and determination results, and various operations such as start of measurement. And an operation unit 12e.

  Next, a procedure for determining the deteriorated solar cell module 4 from the solar cell string 5 in which the plurality of solar cell modules 4 are connected in series using the solar cell module deterioration determination apparatus 10 having such a configuration will be described. I do.

  First, as shown in FIG. 1, a deterioration determination device 10 for a solar cell module is connected to a solar cell string 5 including a solar cell module 4 to be subjected to deterioration determination, and a plurality of solar cells are measured by an IV characteristic measuring unit 11. The reference IV characteristics of the solar cell string 5 in a state where all the battery modules 4 are not shielded from light are measured. More specifically, the current value and the voltage value of the solar cell string 5 are measured while changing the load resistance of the variable load resistance 11a in a state where all the solar cell modules 4 constituting the solar cell string 5 are not shielded from light, From these measurement results, the reference IV characteristics of the solar cell string 5 in a state where light is not blocked are measured.

  The reference IV characteristic measured by the IV characteristic measuring unit 11 is transmitted to the deterioration determining unit 12 by the wireless interfaces 11e and 12b and displayed on the display unit 12d. FIG. 4 shows an example of the reference IV characteristic displayed on the display unit 12d.

  In the reference IV characteristics shown in FIG. 4, a region A surrounded by a broken line indicates that there is a cluster 4d in which the bypass diode 4c is operating in the solar cell string 5, and is surrounded by a broken line. The region B indicates that the solar cell module 4 whose power generation efficiency has relatively decreased in the solar cell string 5 exists.

  Next, one of the plurality of solar cell modules 4 constituting the solar cell string 5 to which the solar cell module deterioration determination device 10 is connected is selected from among a plurality of solar cell modules 4 whose deterioration is to be determined. The module 4 is shielded from light by a light shielding plate. Then, the light-shielding IV characteristic of the solar cell string 5 in a state where one of the solar cell modules 4 to be determined for deterioration is shielded by the light-shielding plate is measured by the IV characteristic measuring unit 11.

  Here, in the measurement of the light-shielding IV characteristic, the entire surface of one selected solar cell module 4 can be covered with a light-shielding plate, but as shown in FIG. If the path can be a path via the bypass diode 4c provided in each of the plurality of clusters 4d constituting the solar cell module 4, only a partial area of the solar cell module 4 is shielded by the light shielding plate 20. You may make it.

  The light-shielded IV characteristic measured by the IV characteristic measuring unit 11 is transmitted to the deterioration determining unit 12 via the wireless interfaces 11e and 12b, and is displayed on the display unit 12d as shown in FIG. Displayed with

  Next, the deterioration judging unit 12 calculates the voltage value V1s in the linear region extending from the operating point Ps of the bypass diode 4c of the light-shielded IV characteristic measured by the IV characteristic measuring unit 11 to the low voltage side, and the IV characteristic. A determination index is extracted from the voltage value V1s in the linear region of the reference IV characteristic measured by the measurement unit 11 and the voltage value V1r at the same measurement point (the same current value), and deterioration is determined based on the determination index. The presence or absence of deterioration of the solar cell module 4 to be determined is determined. Since the solar cell module 4 includes three clusters 4d, the deterioration of the solar cell module 4 is the deterioration of the cluster 4d.

  Here, the deterioration (cluster deterioration) of the cluster 4d of the solar cell module 4 includes an increase in the resistance of the cluster, a break in the cluster, and a short-circuit failure of the bypass diode 4c.

  The term “high cluster resistance” refers to a degraded state in which the bypass diode 4c is operating because the cluster 4d is electrically conductive but has high resistance. In this deteriorated state, the open-circuit voltage value Voc of the entire IV characteristic of the solar cell string 5 does not change from the open-circuit voltage value Voc of the normal solar cell string 5 without cluster deterioration, but is bypassed from the open-circuit voltage value Voc. A voltage region close to a straight line (a region where the bypass diode 4c does not operate) occurs between the operating points Pr and Ps of the diode 4c, and the IV characteristic rises on the lower voltage side than the operating points Pr and Ps of the bypass diode 4c. ing.

  The cluster disconnection is a degraded state in which the bypass diode 4c is operating due to the lack of electrical conduction in the cluster 4d. In this deteriorated state, assuming that the forward voltage of the bypass diode 4c is Vd, the open-circuit voltage value Voc of the entire IV characteristic of the solar cell string 5 is calculated from the open-circuit voltage value of the normal solar cell string 5 without cluster deterioration. Shift by Vc-Vd. Here, Vc is a cluster voltage defined by Voc / (the number of clusters constituting one solar cell module 4 × the number of solar cell modules 4 constituting the solar cell string 5), and in this embodiment, , Vc = Voc / (3 × 8).

  The short-circuit failure of the bypass diode 4c is a deteriorated state in which the rectifying function of the bypass diode 4c is lost and the bypass diode 4c is electrically short-circuited. In this degraded state, the forward voltage Vd of the bypass diode 4c does not occur, so that the IV characteristic shifts from the open voltage value Voc of the normal solar cell string 5 to the low voltage side by Vc.

  When the solar cell string 5 does not include cluster deterioration, the gradient of the tangent line near the open-circuit voltage value Voc of the IV characteristic is dI / dV = −1 / Rs (Rs is the equivalent circuit of the solar cell string. (A series resistance component). Rs changes over a long period of several years, but is sufficiently long compared to the time scale (hundreds of milliseconds) for measuring the IV characteristics, and can be regarded as a constant during the measurement of the IV characteristics. The shape of the IV characteristic has linearity (linearity) near the open-circuit voltage value Voc. The linearity of the IV characteristic is established in the vicinity of the open-circuit voltage value Voc also in the solar cell string 5 including cluster disconnection or cluster deterioration due to short-circuit failure of the bypass diode 4c. On the other hand, in the case of the cluster deterioration in which the resistance of the cluster 4d is increased, the linear characteristic satisfying the above-described relationship of dI / dV = −1 / Rs in the IV characteristic in a region extending from the operating point Ps of the bypass diode 4c to the low voltage side. It can be considered that there is a region having a characteristic (linearity). That is, the light-shielding IV characteristic has an operation region of the bypass diode 4c due to light-shielding, and a region having linearity extending from the operating point Ps of the bypass diode 4c to the low voltage side is a linear region. As shown in FIG. 6, when the reference IV characteristic and the light-shielded IV characteristic each have an operation region of the bypass diode 4c, the linear region in the reference IV characteristic and the light-shielded IV characteristic is the bypass region. A region extending from the operating points Pr and Ps of the diode 4c to the low voltage side and having linearity (linearity) satisfying the above-described relationship of dI / dV = 1 / Rs (Rs: series resistance component). is there.

  In the case of a sufficient power generation amount (for example, the short-circuit current value Isc is 2 A or more) at the time of measuring the IV characteristic, the current of 20% of the short-circuit current value Isc is considered in consideration of the forward voltage Vd of many commercially available bypass diodes 4c. If the value is a value, the above-described linearity (linearity) of the IV characteristic is maintained.

  Therefore, in the aspect of the first embodiment of the present invention, as shown in FIG. 6, the deterioration determination unit 12 sets the current value (20% current value) corresponding to 20% of the short-circuit current value Isc as the measurement point, and A voltage value V1s corresponding to the measurement point (20% current value) on the linear region extending from the operating point Ps of the bypass diode 4c having the -V characteristic to the low voltage side, and a measurement point corresponding to the linear region having the reference IV characteristic. (20% current value), a potential difference ΔV1 between the voltage value V1s and the voltage value V1r is extracted as a determination index, and deterioration of the solar cell module 4 is determined based on the potential difference ΔV1. The presence or absence is determined.

  In the first embodiment, a voltage value V1r of the reference IV characteristic and a voltage value V1s of the light-shielding IV characteristic are obtained using a current value corresponding to 20% of the short-circuit current value Isc as a measurement point. However, as long as it is on a linear region extending from the operating point Ps of the bypass diode 4c to the low voltage side, a point corresponding to any current value may be set as the measurement point. In addition, since the linearity of the light-shielded IV characteristic becomes better as it is closer to the operating point Ps of the bypass diode 4c, a current value closer to the operating point Ps of the bypass diode 4c having the light-shielded IV characteristic is set as a measurement point. It is more preferable to set the operating point Ps of the bypass diode 4c having the light-shielded IV characteristic as the measurement point.

  In the linear region of the reference IV characteristic and the linear region of the light-shielded IV characteristic, the potential difference ΔV1 (discrete value) for the same current value in the linear region is one to one of the number of deteriorations of the cluster 4d of the solar cell module 4. 1 corresponds. Therefore, according to the method for determining deterioration of a solar cell module of the present embodiment, not only the presence or absence of cluster deterioration of solar cell module 4 but also the number of deteriorated clusters 4d is determined based on the above-described determination index, that is, potential difference ΔV1. can do.

  For example, one of the three clusters 4d constituting the solar cell module 4 is deteriorated, and the current from the adjacent solar cell module 4 is bypassed without flowing to the cell string 4b in the one deteriorated cluster 4d. When the current flows through the path via the diode 4c and flows into the cell string 4b in the two normal clusters 4d, the potential difference between both ends of the solar cell module 4 becomes 2Vc− in the case of increasing the resistance of the cluster or disconnecting the cluster. Vd, and becomes 2Vc in the case of a short-circuit failure of the bypass diode 4c. Here, if the three clusters 4d of the solar cell module 4 are shielded from light by the light shielding plate 20 and the generated current is diverted to the path passing through all the three bypass diodes 4c, the cluster resistance is increased or the cluster is disconnected. , The potential difference between both ends of the solar cell module 4 becomes −3 Vd, and the potential difference between both ends of the solar cell module 4 in the case of a short-circuit failure of the bypass diode 4 c becomes −2 Vd. Therefore, the potential difference between both ends of the solar cell module 4 before and after the light shielding is (2Vc−Vd) − (− 3Vd) = 2Vc + 2Vd in the case of a high cluster resistance or cluster disconnection, and 2Vc in the case of a short-circuit failure of the bypass diode 4c. Since − (− 2Vd) = 2Vc + 2Vd, the existence of one deteriorated cluster 4d in the solar cell module 4 means that the voltage across the solar cell module 4 is 2Vc + 2Vd by blocking the solar cell module 4 from light. It can be determined by detecting the occurrence.

  On the other hand, two of the three clusters 4d constituting the solar cell module 4 are deteriorated, and the current from the adjacent solar cell module 4 flows through the cell string 4b in the two deteriorated clusters 4d. When the current flows through the bypass diode 4c and flows through the cell string 4b in one normal cluster 4d, the potential difference between both ends of the solar cell module 4 becomes high in the case of high cluster resistance or cluster disconnection. Vc−2Vd, and becomes Vc in the case of a short-circuit failure of the bypass diode 4c. Here, if the three clusters 4d of the solar cell module 4 are shielded from light by the light shielding plate 20 and the generated current is diverted to the path passing through all the three bypass diodes 4c, the cluster resistance is increased or the cluster is disconnected. , The potential difference between both ends of the solar cell module 4 becomes −3 Vd, and the potential difference between both ends of the solar cell module 4 in the case of a short-circuit failure of the bypass diode 4 c becomes −2 Vd. Therefore, the potential difference between both ends of the solar cell module 4 before and after the light shielding is (Vc−2Vd) − (− 3Vd) = Vc + Vd in the case of a high cluster resistance or cluster disconnection, and Vc in the case of a short-circuit failure of the bypass diode 4c. Since − (− Vd) = Vc + Vd, the existence of the two deteriorated clusters 4 d in the solar cell module 4 means that the voltage between both ends of the solar cell module 4 is Vc + Vd by shading the solar cell module 4. It can be determined by detecting the occurrence.

  Similarly, all three clusters 4d constituting the solar cell module 4 deteriorate, and current from the adjacent solar cell module 4 passes through the bypass diode 4c without flowing to the cell string 4b in all three clusters 4d. In the case where the current flows through the route, the potential difference between both ends of the solar cell module 4 before and after the light shielding becomes (−3Vd) − (− 3Vd) = 0 in the case of high cluster resistance or cluster disconnection, and the short-circuit of the bypass diode 4c. In the case of a failure, -Vd-(-Vd) = 0, so that the existence of the three deteriorated clusters 4d in the solar cell module 4 indicates that the voltage across the solar cell module 4 The determination can be made by detecting that the value becomes 0 by shielding the light.

  As described above, the number of degraded clusters included in one solar cell module 4 and the difference (discrete value) between the open-circuit voltage values before and after light shielding correspond to one-to-one. Therefore, in the method for determining the deterioration of the solar cell module according to the present embodiment, the presence or absence of the deterioration of the cluster 4d of the solar cell module 4 and the number of the deteriorated clusters 4d based on the potential difference ΔV1 which is the determination index are determined in the following procedure. It can be carried out.

  That is, when the potential difference ΔV1 as the determination index takes a value close to the above-mentioned 2Vc + 2Vd, it is possible to determine that one cluster 4d in the solar cell module 4 has deteriorated. Further, when the potential difference ΔV1 as the determination index takes a value close to the above-described Vc + Vd, it is possible to determine that the two clusters 4d in the solar cell module 4 are deteriorated. Furthermore, when the potential difference ΔV1 as the determination index takes a value close to 0, it is possible to determine that the three clusters 4d in the solar cell module 4 have deteriorated.

  As described above, according to the present embodiment, the voltage value V1s on the linear region extending from the operating point Ps of the bypass diode 4c having the light-shielded IV characteristic to the low voltage side and the reference at the same current value as the voltage value V1s A potential difference ΔV1 as a determination index is extracted from the voltage value V1r on the linear region of the IV characteristic, and based on the potential difference ΔV1, the deterioration determination unit 12 selects the cluster deterioration of the selected solar cell module 4 to be determined. And the number of deteriorated clusters can be obtained.

  Further, for the plurality of solar cell modules 4 constituting the solar cell string 5, all the solar cell modules 4 constituting the solar cell string 5 are selected by sequentially selecting the solar cell modules 4 to be determined and performing the same procedure as described above. It is possible to determine the presence or absence of cluster deterioration and the number of deteriorated clusters for the solar cell module 4.

  Here, Vc is a value obtained by dividing the open-circuit voltage value Voc of the reference IV characteristic by the number of all clusters 4 d constituting the solar cell string 5, which is apparent from the IV characteristic of the solar cell module 4. As described above, the open-circuit voltage value Voc is affected by solar radiation fluctuation. On the other hand, since the potential difference ΔV1 for determining the number of deteriorated clusters is a discrete value, the range of the potential difference ΔV1 can be set so that the number of deteriorated clusters can be correctly determined. For example, in order to be able to determine that the number of degraded clusters is 1, even if the potential difference ΔV1 = 2Vc + 2Vd fluctuates within a range not exceeding the width of one cluster voltage Vc, the number of degraded clusters is erroneously determined to be 0 or 2. Can be avoided.

  Therefore, in the present embodiment, as shown in FIG. 6, when the potential difference ΔV1 is in the range of ± Vc / 2 from Vd + 2Vc, that is, when Vd + 5Vc / 2> ΔV1 ≧ Vd + 3Vc / 2, the number of cluster deterioration is one. When the potential difference ΔV1 is within the range of ± Vc / 2 from Vd + Vc, that is, when Vd + 3Vc / 2> ΔV1 ≧ Vd + Vc / 2, it is determined that the cluster deterioration number is 2, and the potential difference ΔV1 is reduced from Vd. Is determined to be within the range of ± Vc / 2, that is, when Vd + Vc / 2> ΔV1 ≧ Vd−Vc / 2, the number of deteriorated clusters is determined to be 3. When the potential difference ΔV1 satisfies ΔV1 ≧ Vd + 5Vc / 2, the deterioration is determined. It is determined that the number of clusters is zero. Thereby, even if the IV characteristic of the solar cell module 4 is affected by the solar radiation fluctuation or the like, the number of deteriorated clusters can be accurately determined.

  In the present embodiment, when it is determined that the solar cell module 4 has not deteriorated (the number of deteriorated clusters is 0) based on the potential difference ΔV1 as the determination index, the linear region of the light-shielding IV characteristic is determined. Also, based on the potential difference ΔV2 between the voltage value V2s corresponding to the predetermined current value on the low voltage side and the voltage value V2r corresponding to the predetermined current value of the reference IV characteristic, it is determined whether the current of the solar cell string 5 has decreased. The decision is made. By determining the presence or absence of a decrease in the current of the photovoltaic string 5, it is possible to identify a photovoltaic module 4 that includes a cluster 4d having a reduced photoelectric conversion efficiency (power generation efficiency), which is different from the above-described cluster degradation.

  As shown in FIG. 6, when the solar cell string 5 includes clusters 4 d whose photoelectric conversion efficiency is reduced in a state where the cluster is not deteriorated, the horizontal additivity of the voltage with respect to the same current point of each cluster 4 d is used. Since the added voltage is smaller than that in the case of the normal cluster, the IV characteristic of the solar cell string 5 has the same deformation as in the case where the shadow is applied to the high current-high voltage region as shown in FIG. (Inflection point p) occurs. The position of the inflection point p is on the lower current side (higher voltage side) of the IV characteristic as the decrease in photoelectric conversion efficiency is larger.

  In the present embodiment, when it is determined that the solar cell module 4 has not deteriorated (the number of deteriorated clusters is 0) based on the potential difference ΔV1, that is, the potential difference ΔV1 is a value close to 3Vd + 3Vd, and the reference I− In the current range from the inflection point p of the maximum current value in the inflection point of the V characteristic to the short-circuit current value Isc, the voltage at the same current value (measurement point) of the reference IV characteristic and the shading IV characteristic When the potential difference ΔV2 between the values V2s and V2r is smaller than the potential difference ΔV1, it is determined that there is a cluster 4d having a reduced photoelectric conversion efficiency in the light-shielded solar cell module 4. That is, when ΔV1> Vd + 5Vc / 2 and ΔV2 <(Vd + 3Vc) × α (0 <α <1) are satisfied, it is determined that there is a cluster 4d having a reduced photoelectric conversion efficiency in the light-shielded solar cell module 4. I do.

  In the present embodiment, the current range from the inflection point p of the maximum current value in the inflection point of the reference IV characteristic to the short-circuit current value Isc, more specifically, 80% of the short-circuit current value Isc Although the potential difference ΔV2 between the voltage values V2s and V2r is obtained using the current value as a measurement point, the measurement point may be any current value that is lower than the linear region of the light-shielded IV characteristic.

  Summarizing the above, as shown in FIG. 7, the forward voltage Vd of the bypass diode 4c is input as a pre-measurement setting, and the reference IV characteristic and the light-shielded IV characteristic are measured. From the forward voltage Vd and the open-circuit voltage value (Voc) in the reference IV characteristic, a determination area boundary of cluster deterioration is derived, a potential difference ΔV1 is derived from the voltage values V1r, V1s, and a potential difference is derived from the voltage values V2r, V2s. ΔV2 is derived, these are collated with the determination region boundaries, and a deterioration determination is performed. The presence or absence of cluster deterioration and the number of deteriorated clusters are determined, and the presence or absence of a current decrease in the solar cell string 5 is determined. If not, it is determined that the solar cell string 5 is normal. The above determination result is displayed on the display unit 12d.

  A more specific procedure will be described with reference to FIGS. 8 and 9. When the operator performs an operation to start the measurement of the reference IV characteristic on the operation unit 12 e, the control related to the measurement of the reference IV characteristic is performed. The information is transmitted from the control unit 12a of the deterioration determination unit 12 to the IV characteristic measuring unit 11, and the control unit 11d of the IV characteristic measuring unit 11 measures the reference IV characteristic. The measurement result of the reference IV characteristic is transmitted to the control unit 12a of the deterioration determination unit 12, subjected to data display processing, and displayed on the display unit 12d (FIG. 4). In addition, the control unit 12a extracts the discrimination parameter based on the measurement result of the reference IV characteristic and derives the determination region boundary, and thereafter, displays on the display unit 12d that the preparation for the measurement of the light-shielded IV characteristic is completed. I do.

  When the operator recognizes from the display on the display unit 12d that the preparation for the measurement of the light-shielded IV characteristic is completed, the operator selects the solar cell module 4 to be measured, and performs the light-shielding operation on the solar cell module 4. By operating the operation unit 12e, measurement of the light-shielded IV characteristic is started. When the measurement of the light-shielded IV characteristic is started, control information on the measurement of the light-shielded IV characteristic is transmitted from the control unit 12a of the deterioration determination unit 12 to the IV characteristic measurement unit 11, and the IV characteristic measurement unit The 11 control unit 11d measures the light-shielded IV characteristics. The measurement result of the light-shielded IV characteristic is transmitted to the control unit 12a of the deterioration determination unit 12, subjected to data display processing, and displayed on the display unit 12d together with the reference IV characteristic (FIG. 6). Further, the control unit 12a extracts the discrimination parameter based on the measurement result of the light-shielded IV characteristic, derives the potential differences ΔV1, ΔV2, compares them with the boundary of the determination area, determines the deterioration, and determines the determination result. It is displayed on the display unit 12d.

  Thereafter, the same procedure is repeated for all the solar cell modules 4 constituting the solar cell string 5 to determine the deterioration of all the solar cell modules 4.

  Next, a second embodiment of the present invention will be described. Also according to the second embodiment, the solar cell module is made using the linear region extending from the operating point Ps of the bypass diode 4c of the light-shielded IV curve to the low voltage side and the linear region of the reference IV characteristic corresponding to the linear region. , And the number of deteriorated clusters can be determined.

  In the first embodiment of the present invention, a voltage value V1s corresponding to a predetermined current value on the linear region of the light-shielded IV characteristic and a voltage value V1r corresponding to a predetermined current value on the linear region of the reference IV characteristic are provided. The presence / absence of cluster deterioration is determined using the potential difference ΔV1 between the two as a determination index.

  On the other hand, in the second embodiment, as shown in FIG. 10, when the reference IV characteristic has an operation region of the bypass diode 4c, that is, at least one cluster 4d constituting the solar cell string 5 is deteriorated. When the bypass diode 4c of the cluster 4d is operating, the voltage value V3s at the point where the extrapolated line Ls extrapolated from the operating point Ps of the bypass diode 4c of the light-shielded IV characteristic intersects with the voltage axis, The potential difference ΔV3 from the voltage value V3r at the point where the extrapolation line Lr extrapolated from the operating point Pr of the IV characteristic bypass diode 4c intersects the voltage axis is used as a determination index, and the potential of the solar cell module 4 is determined based on the potential difference ΔV3. The presence or absence of deterioration is determined.

  Since the potential difference ΔV3 in the second embodiment is an index for determining the number of deteriorated clusters equivalent to the potential difference ΔV2 in the first embodiment, the number of deteriorated clusters is determined based on the potential difference ΔV3 using the same cluster degradation number determination method as the potential difference ΔV2. Can be determined. That is, as shown in FIG. 10, when the potential difference ΔV3 is within the range of ± Vc / 2 from Vd + 2Vc, that is, when Vd + 5Vc / 2> ΔV3 ≧ Vd + 3Vc / 2, the cluster deterioration number is determined to be 1, and the potential difference is determined. When ΔV3 is in the range of Vd + Vc to ± Vc / 2, that is, when Vd + 3Vc / 2> ΔV3 ≧ Vd + Vc / 2, the cluster deterioration number is determined to be 2, and the potential difference ΔV3 is in the range of Vd to ± Vc / 2. When Vd + Vc / 2> ΔV3 ≧ Vd−Vc / 2, the number of deteriorated clusters is determined to be 3. When the potential difference ΔV3 satisfies ΔV3 ≧ Vd + 5Vc / 2, the number of deteriorated clusters is 0. Can be determined.

  Here, the extrapolation line Ls is a determination point determination straight line extrapolated from the operating point Ps in a direction along the linear region of the light-shielding IV characteristic, and more specifically, the light-shielding I- passing through the operating point Ps. It is a tangent line of the V characteristic. The extrapolation line Lr is a determination point determination straight line extrapolated from the operating point Pr in a direction along the linear region of the reference IV characteristic, and more specifically, the reference IV passing through the operating point Pr. This is the tangent of the characteristic. The extrapolation line Ls may be obtained by the least square method using the voltage value and the current value of at least two measurement points belonging to the linear region of the light-shielded IV characteristic. Similarly, the extrapolation line Lr may be obtained by the least squares method using the voltage value and the current value of at least two measurement points belonging to the linear region of the reference IV characteristic.

  If the operating area of the bypass diode 4c does not appear in the reference IV characteristic, a straight line that is in contact with the reference IV characteristic on the low voltage side at the point where the open voltage value Voc of the reference IV characteristic is given is referred to as the reference I-V characteristic. The extrapolation line Lr of the −V characteristic or the determination point determination line can be used.

  In summary, as shown in FIG. 11, the forward voltage Vd of the bypass diode 4c is input as a pre-measurement setting, and the reference IV characteristic and the light-shielded IV characteristic are measured. From the forward voltage Vd and the open-circuit voltage value Voc in the reference IV characteristic, a determination region boundary for cluster deterioration is derived, and a potential difference ΔV3 is derived from the voltage values V3r and V3s. A determination is made to determine the presence or absence of cluster deterioration and the number of deteriorated clusters.

  A more specific procedure will be described with reference to FIGS. 12 and 13. When the operator performs an operation to start the measurement of the reference IV characteristic on the operation unit 12 e, the control related to the measurement of the reference IV characteristic is performed. The information is transmitted from the control unit 12a of the deterioration determination unit 12 to the IV characteristic measurement unit 11, and the control unit 11d of the IV characteristic measurement unit 11 measures the reference IV characteristic. The measurement result of the reference IV characteristic is transmitted to the control unit 12a of the deterioration determination unit 12, subjected to data display processing, and displayed on the display unit 12d. In addition, the control unit 12a extracts the voltage value V3r based on the measurement result of the reference IV characteristic and derives the determination region boundary, and then notifies the display unit 12d that the preparation for the measurement of the light-shielded IV characteristic is completed. indicate.

  When the operator recognizes from the display on the display unit 12d that the preparation for the measurement of the light-shielded IV characteristic is completed, the operator selects the solar cell module 4 to be measured, and performs the light-shielding operation on the solar cell module 4. By operating the operation unit 12e, measurement of the light-shielded IV characteristic is started. When the measurement of the light-shielded IV characteristic is started, control information on the measurement of the light-shielded IV characteristic is transmitted from the control unit 12a of the deterioration determination unit 12 to the IV characteristic measurement unit 11, and the IV characteristic measurement unit The 11 control unit 11d measures the light-shielded IV characteristics. The measurement result of the light-shielded IV characteristics is transmitted to the control unit 12a of the deterioration determination unit 12, subjected to data display processing, and displayed on the display unit 12d together with the reference IV characteristics (FIG. 10). In addition, the control unit 12a extracts the voltage value V3s based on the measurement result of the light-shielded IV characteristic, derives the potential difference ΔV3 from the voltage value V3r and the voltage value V3s, and compares this with the determination area boundary to determine the deterioration. A determination is made and the result of the determination is displayed on the display unit 12d.

  Thereafter, the same procedure is repeated for all the solar cell modules 4 constituting the solar cell string 5 to determine the deterioration of all the solar cell modules 4.

  As described above, according to the solar cell module deterioration determination method or deterioration determination device 10 of the present embodiment, the voltage value in the linear region extending from the operating point Ps of the bypass diode 4c having the light-shielded IV characteristic to the low voltage side, A potential difference ΔV1 or ΔV3 is extracted as a judgment index from the voltage value and a voltage value in the linear region of the reference IV characteristic at the same measurement point, and deterioration of the solar cell module 4 is determined based on these potential differences ΔV1 or ΔV3. Is determined, the following effects can be obtained.

  That is, the cluster deterioration includes three cluster deterioration modes of increasing the resistance of the cluster, disconnection of the cluster, and short-circuit failure of the bypass diode 4c, and the solar cell module 4 including three clusters has 27 different cluster deterioration patterns. However, regardless of the deterioration pattern, it is necessary to replace the solar cell module 4 as soon as possible, so that it is possible to specify whether or not the replacement of the solar cell module 4 is necessary with a single index. It is valid. In response to such a demand, the deterioration determination method or deterioration determination device 10 of the solar cell module according to the present embodiment uses a low voltage from the operating points Ps and Pr of the bypass diode 4c of the light-shielded IV characteristic and the reference IV characteristic. The potential difference ΔV1 or the potential difference ΔV3 is extracted as a single discriminant index using the linear region of the both IV characteristics extending to the side, and the presence or absence of the deterioration of the solar cell module 4 is determined based on this discriminant index. By utilizing the discreteness of the determination index, it is possible to simultaneously identify the solar cell module 4 including the cluster deterioration and the number of the deteriorated clusters.

  The solar cell module deterioration determination device 10 can also determine an open failure of the bypass diode 4c included in the solar cell module 4 to be determined.

  As described above, the bypass diode 4c is a portion where the power generation amount of the cell string 4b inside the cluster 4d is relatively reduced due to uneven irradiation of sunlight to the cell string 4b due to a shadow or a failure. Operates when the voltage between both ends of the cell string 4b becomes higher than the voltage generated by the normally generating portion of the cell string 4b inside the same cluster 4d and becomes equal to the forward voltage Vd of the bypass diode 4c. This is to avoid generation of a hot spot in the cell string 4b by bypassing the generated current so as to bypass the current. Accordingly, when the entire normal solar cell module 4 is uniformly irradiated with sunlight, the sum of the electromotive forces generated by the power generation of each solar cell 4a becomes equal to or higher than the forward voltage Vd of the bypass diode 4c. Flows through each cell string 4b in order without passing through the bypass diode 4c.

  As shown in FIG. 14A, when the bypass diode 4c of a certain cluster 4d has an open failure, the cell string 4b of the solar cell module 4 does not deteriorate in a non-light-shielded state in which the solar cell module 4 is not shielded from light. Alternatively, when the solar cell module 4 is not shaded and has no surface dirt, as shown by the thick line in FIG. 14A, the generated current flows through each cell string 4b in order without passing through the bypass diode 4c. It is not possible to detect the presence or absence of the open failure of 4c. The IV characteristic at this time is a reference IV indicated by a solid line in FIG.

  On the other hand, as shown in FIG. 14B, the light-shielding plate 20 causes the conductive path of the solar cell module 4 to pass through the bypass diode 4c provided in each of the plurality of clusters 4d constituting the solar cell module 4. When only a part of the solar cell module 4 is shielded from light, the current bypasses the path passing through the bypass diode 4c in the cluster 4d in which the bypass diode 4c operates normally, but the cluster in which the bypass diode 4c has an open failure. The generated current is forced to flow through the cell string 4b of 4d. When the generated current is forcibly applied to the cell string 4b of the cluster 4d in which the bypass diode 4c has an open failure, the solar cell 4a in the light-shielded portion on the path becomes a resistor and serves as a light-shielded IV in FIG. As shown by the broken line, the IV characteristic has a shape in which the amount of power generation is significantly reduced with respect to the reference IV.

  Subsequently, the light-shielding plate 20 is removed, and the IV characteristic is measured with the solar cell module 4 in the state shown in FIG. At this time, the IV characteristic has a shape substantially equal to the reference IV, as shown by a chain line in FIG.

Therefore, assuming that the current values for the predetermined voltage value Vbp are I ₁ , I ₂ , and I _{3 in} the three IV characteristics of the reference IV, the light-shielded IV, and the non-light-shielded IV, respectively, I ₂ / I ₁ ≦ β (determination Constant) and I ₁ ＩI ₃ or I ₁ = I ₃ holds, it can be determined that the solar cell module 4 has an open failure of the bypass diode 4c.

  The discrimination constant β for discriminating the open failure of the bypass diode 4c is a constant determined by a light-shielding region necessary for diverting a generated current by a light-shielding operation to a path passing through the bypass diode 4c. As shown in FIG. 14B, the light-shielding plate 20 has a width L1 in the horizontal direction of the rectangular shape, which is the width in the direction in which the clusters 4d of the solar cell modules 4 are arranged, that is, the short side of each cluster 4d. The length is set to be substantially equal to the width dimension CL × the number of clusters, and the length L2 of the rectangular shape in the vertical direction passes through the bypass diode 4c provided in each cluster 4d by the light shielding operation by the light shielding plate 20. The length is set to a light-shielding area capable of diverting the generated current to the path. Therefore, in this case, the discrimination constant β can be determined by appropriately setting L2 as a function of L2.

  FIG. 16 shows the IV characteristics of a solar cell string including 14 solar cell modules in the case where an open fault of a bypass diode is not included, and one open fault of a bypass diode (one cluster). Here, it is an example of a simulation showing an IV characteristic when one solar cell module 4 is entirely shielded from light. In this simulation, numerical values of commercially available modules having an open-circuit voltage of 36.8 V, a short-circuit current of 8.75 A, a maximum output operation voltage of 29.7 V, and a maximum output operation current of 8.17 A were used.

According to the simulation results, in the case of the open failure of the bypass diode, the string current decreases in almost all the voltage region when the entire solar cell module is shielded from light, and the short-circuit current value It can be seen that Isc drops to about 50%. Therefore, when the current values I ₁ , I ₂ , and I ₃ are taken as the short-circuit current value Isc (Vbp = 0 V), one solar cell module is set to be entirely light-shielded (L2 is substantially equal to the long side of the cluster). Then, the discrimination constant β may be set to 0.5 <β <1. When Vbp = 300 V, the discrimination constant β may be set to 0.3 <β <0.5.

A more specific procedure of the method for determining the open failure of the bypass diode by the solar cell module deterioration determining apparatus 10 will be described with reference to FIGS. 17 and 18. When the operator measures the reference IV characteristic with respect to the operation unit 12e. When the start operation is performed, control information on the measurement of the reference IV characteristic is transmitted from the control unit 12a of the deterioration determination unit 12 to the IV characteristic measurement unit 11, and the control unit 11d of the IV characteristic measurement unit 11 The reference IV characteristic (reference IV in FIG. 15) is measured at. The measurement result of the reference IV characteristic is transmitted to the control unit 12a of the deterioration determination unit 12, subjected to data display processing, and displayed on the display unit 12d. The control unit 12a extracts the current value I ₁ in Vbp based on the measurement result of the reference the I-V characteristic, then, the display unit 12d that the measurement preparation for shielding the I-V characteristic has been completed.

When the operator recognizes from the display on the display unit 12d that the preparation for the measurement of the light-shielded IV characteristic is completed, the operator selects the solar cell module 4 to be measured, and performs the light-shielding operation on the solar cell module 4. By operating the operation unit 12e, measurement of the light-shielded IV characteristic is started. When the measurement of the light-shielded IV characteristic is started, control information on the measurement of the light-shielded IV characteristic is transmitted from the control unit 12a of the deterioration determination unit 12 to the IV characteristic measurement unit 11, and the IV characteristic measurement unit The measurement of the light-shielded IV characteristic (light-shielded IV in FIG. 15) is performed by the eleventh control unit 11d. The measurement result of the light-shielded IV characteristic is transmitted to the control unit 12a of the deterioration determination unit 12, subjected to data display processing, and displayed on the display unit 12d together with the reference IV characteristic. The control unit 12a, when the extracted current values _{I 2} at Vbp based on the measurement result of the light-shielding the I-V _{characteristic,} it _is judged whether satisfy I 2 / _{I 1} ≦ beta, satisfying (YES), the An instruction to perform the measurement again in the non-light-shielded state is displayed on the display unit 12d together with the determination result.

When the operator recognizes from the display on the display unit 12d that measurement is to be performed again in the non-light-shielded state, the operator sets the solar cell module 4 in the light-shielded state, and then operates the operation unit 12e to operate the non-light-shielded IV. Start measuring characteristics. When the measurement of the non-shielded IV characteristic is started, control information on the measurement of the non-shielded IV characteristic is transmitted from the control unit 12a of the deterioration determination unit 12 to the IV characteristic measurement unit 11, and the IV characteristic is measured. The non-light-shielded IV characteristic (non-light-shielded IV in FIG. 15) is measured by the control part 11d of the measurement part 11. The measurement result of the non-light-shielded IV characteristic is transmitted to the control unit 12a of the deterioration determination unit 12, subjected to data display processing, and displayed on the display unit 12d together with the reference IV characteristic and the light-shielded IV characteristic. The control unit 12a extracts the current value _{I 3} in Vbp based on the measurement result of the non-shaded the I-V characteristic, _{I 3} is equal to or comparable with _{I 1,} the same degree (YES) In the case of, it is determined that an open fault has occurred in the bypass diode, and the determination result is displayed on the display unit 12d.

It can be said that the above-described method of determining the open failure of the bypass diode in the solar cell module has the following configuration.
`` From a solar cell string in which a plurality of solar cell modules are connected in series, a bypass diode open failure determination method in a solar cell module for determining a solar cell module in which a bypass diode has an open failure,
Measuring a first current value at a predetermined voltage value of the solar cell string in a state where all the plurality of solar cell modules are not shaded;
Next, all or only a part of the solar cell module is shielded from light so that a conductive path of one solar cell module selected from a plurality of the solar cell modules passes through the bypass diode. Measuring a second current value of the solar cell string at the predetermined voltage value,
Next, a third current value at the predetermined voltage value of the solar cell string is measured in a state where all of the plurality of solar cell modules are not shaded again,
If the second current value is equal to or less than a predetermined ratio with respect to the first current value, and the third current value is substantially the same as the first current value, the bypass diode may cause an open failure. And determining whether there is an open fault in the bypass diode in the solar cell module. "

In addition, the solar cell module deterioration determination device 10 that performs the above-described method of determining the open failure of the bypass diode in the solar cell module can be said to be an open failure determination device of the bypass diode in the solar cell module, and has the following configuration. It is.
`` From a solar cell string in which a plurality of solar cell modules are connected in series, a bypass diode open failure determination device in a solar cell module that determines a solar cell module in which a bypass diode has an open failure,
A first current value at a predetermined voltage value of the solar cell string in a state where all of the plurality of solar cell modules are not shielded from light is measured, and then the conductivity of one of the solar cell modules selected from the plurality of solar cell modules is measured. Light shielding all or only a part of the solar cell module so that the path is a path passing through the bypass diode, measuring a second current value at the predetermined voltage value of the solar cell string in the light shielding state, Next, a current measurement unit that measures a third current value at the predetermined voltage value of the solar cell string in a state where all of the plurality of solar cell modules are not shaded again,
If the second current value is equal to or less than a predetermined ratio with respect to the first current value, and the third current value is substantially the same as the first current value, the bypass diode may cause an open failure. An open failure determination device for a bypass diode in a solar cell module, comprising: "

  The present invention is not limited to the above embodiment, and it goes without saying that various changes can be made without departing from the spirit of the present invention.

REFERENCE SIGNS LIST 1 solar power generation system 2 solar cell panel 3 power conditioner 4 solar cell module 4 a solar cell 4 b cell string 4 c bypass diode 4 d cluster 5 solar cell string 5 a conductive wire 5 b conductive wire 6 junction box 6 a disconnector 6 b backflow prevention diode Reference Signs List 10 Solar cell module deterioration determination device 11 IV characteristic measurement unit 11a Variable load resistance 11b Current measurement unit 11c Voltage measurement unit 11d Control unit 11e Wireless interface 12 Deterioration determination unit 12a Control unit 12b Wireless interface 12c Data storage unit 12d Display unit 12e Operation part 20 Light shield plate A region B region Ps Operating point Voc of bypass diode Open voltage value Pr Operating point Vd of bypass diode Forward voltage Isc of bypass diode Short circuit current value V1s Voltage value V1r Voltage value ΔV1 Potential difference V2s Voltage value V2r Voltage value ΔV2 Voltage difference p Inflection point Ls Extrapolation line V3s Voltage value Lr Extrapolation line V3r Voltage value ΔV3 Voltage difference β Discrimination constant L1 Length CL Width L2 Length

Claims (4)

A solar cell module deterioration determination method for determining the deteriorated solar cell module from a solar cell string in which a plurality of solar cell modules are connected in series,
Measuring a reference IV characteristic of the solar cell string in a state where all of the plurality of solar cell modules are not shaded,
One of the solar cell modules selected from the plurality of solar cell modules is set so that the conductive path of the solar cell module becomes a path via a bypass diode provided in each of the plurality of clusters constituting the solar cell module. To measure light-shielding IV characteristics of the solar cell string in the light-shielded state,
When the reference IV characteristic has an operation region of the bypass diode,
A point where a straight line obtained by the least square method using the voltage value and the current value of at least two measurement points belonging to a linear region extending from the operating point of the bypass diode to the low voltage side of the light-shielding IV characteristic intersects the voltage axis. And a straight line obtained by the least squares method using the voltage value and the current value of at least two measurement points belonging to a linear region extending from the operating point of the bypass diode of the reference IV characteristic to the low voltage side from the operating point of the reference IV characteristic. Extract the potential difference from the voltage value at the point where the axis intersects as a judgment index,
When the reference IV characteristic does not have an operation region of the bypass diode,
A point where a straight line obtained by the least square method using the voltage value and the current value of at least two measurement points belonging to a linear region extending from the operating point of the bypass diode to the low voltage side of the light-shielding IV characteristic intersects the voltage axis. And the potential difference between the voltage value at the point intersecting the voltage axis of the reference IV characteristic is extracted as a determination index,
For each of the voltage values corresponding to the number of deteriorated clusters of the solar cell module on a one-to-one basis, a voltage range having a voltage value width equal to one cluster voltage value is calculated as a determination area, and the potential difference serving as the determination index is calculated. And determining that the solar cell module is deteriorated when is within the determination region. When it is determined that the solar cell module is not deteriorated based on the determination index,
Based on a potential difference between a voltage value corresponding to a predetermined current value on the low voltage side of the linear region of the light-shielding IV characteristic and a voltage value corresponding to the predetermined current value of the reference IV characteristic, The method for determining deterioration of a solar cell module according to claim 1, wherein the presence or absence of a decrease in current of the solar cell string is determined. A solar cell module deterioration judging device for judging the deteriorated solar cell module from a solar cell string in which a plurality of solar cell modules are connected in series,
A variable load resistor connected to both ends of the solar cell string, a current measuring unit for measuring a current value flowing through the solar cell string, and a voltage value at a connection portion of the solar cell string with the variable load resistor. A voltage measuring unit, the reference IV characteristic of the solar cell string in a state where all of the plurality of solar cell modules are not shielded from light, and one solar cell module selected from the plurality of solar cell modules. Measure the light-shielded IV characteristics of the solar cell string in a state where light is shielded such that the conductive path of the battery module is a path via bypass diodes provided in each of the plurality of clusters constituting the solar cell module. A possible IV characteristic measuring unit;
When the reference IV characteristic has an operation region of the bypass diode, the voltage value of at least two measurement points belonging to a linear region extending from the operation point of the bypass diode to the low voltage side of the light-shielding IV characteristic A voltage value at a point where a straight line obtained by a least square method using a current value intersects a voltage axis, and at least two measurements belonging to a linear region extending from the operating point of the bypass diode of the reference IV characteristic to a low voltage side. The potential difference between the voltage value at the point where the straight line obtained by the least squares method using the voltage value and the current value at the point intersects the voltage axis is extracted as a judgment index, and the reference IV characteristic is the operating area of the bypass diode. In the case where there is no measurement, at least two measurement points belonging to a linear region extending from the operating point of the bypass diode of the light-shielded IV characteristic to the low voltage side. The potential difference between the voltage value at the point where the straight line obtained by the least squares method using the voltage value and the current value at the point intersects the voltage axis and the voltage value at the point where the voltage axis intersects the voltage axis of the reference IV characteristic is determined. For each of the voltage values corresponding to the number of deteriorated clusters of the solar cell module in a one-to-one correspondence, a voltage range having a voltage value width equal to one cluster voltage value is calculated as a determination region, and the determination is made as an index. A deterioration determining unit that determines that the solar cell module is deteriorated when the potential difference serving as an index is within the determination region. The deterioration determination unit,
When it is determined that the solar cell module is not deteriorated based on the determination index,
Based on a potential difference between a voltage value corresponding to a predetermined current value on the low voltage side of the linear region of the light-shielding IV characteristic and a voltage value corresponding to the predetermined current value of the reference IV characteristic, The deterioration judging device for a solar cell module according to claim 3, wherein whether the current of the solar cell string is reduced is determined.

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