JP2014011428A - Failure detection device, failure detection system, and failure detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect failure of a by-pass diode built in a solar cell module with high accuracy by a simple device configuration.SOLUTION: A failure detection device 5 comprises: a solar cell; and at least one by-pass diode connected in parallel therewith, and detects failure of a by-pass diode in a solar cell string 130 which is in parallel off state for the load. The failure detection device comprises: a voltage source circuit 51 for applying a reverse voltage of a specified value, with reference to the negative electrode, to the positive electrode of the solar cell string 130; a current measurement unit 52 for measuring the value of a current flowing from the negative electrode toward the positive electrode of the solar cell string 130 when a reverse voltage is applied by the voltage source circuit 51; and a control/determination unit 53 for determining failure of a by-pass diode based on the current value measured by the current measurement unit 52.

Description

  The present invention relates to a failure detection device, a failure detection system, and a failure detection method for a bypass diode attached to a solar cell.

  In general, in a solar cell module that generates power using sunlight, a reverse voltage may be applied to the solar cell due to, for example, variations in characteristics, fluctuations in solar radiation intensity, and the like, and this reverse voltage increases. In such a case, there is a risk that the solar cell may generate heat and be damaged. Therefore, as a conventional solar cell module, there is known a module in which a bypass diode is connected in parallel to a solar cell and an excessive reverse voltage is prevented from being applied to the solar cell.

  In such a solar cell module, as described in Patent Document 1 below, for example, a failure detection device that detects an open mode (also referred to as an open mode) failure of a bypass diode has been developed. In the inspection apparatus described in Patent Document 1, the solar cell is shielded from light by the shielding plate, and the temperature of the light shielding portion of the solar cell is detected by the thermal paper integrated with the shielding plate. And when generation | occurrence | production of hot spot heat | fever (abnormal heat_generation | fever) is detected in the shielding part of a solar cell, it determines with the electric current not flowing into a bypass diode, and, thereby, determines with the bypass diode having an open mode failure.

  Patent Document 2 below discloses a technique for finding a failure of a bypass diode based on the electrical characteristics of a solar cell module. In detail, in this diagnostic method, a charged capacitor is connected to a measurement target part excluding the blocking diode of the solar cell string and discharged, and the voltage and current of the measurement target part are measured at the time of discharging. -Diagnose the failure of the measurement target part based on the change of the V characteristic.

JP 2001-024204 A JP 2011-66320 A

  However, in the diagnostic method according to Patent Document 1, it is necessary to shield the solar cell in order to detect an open mode failure of the bypass diode. However, since the solar cell is usually installed at a high place such as a roof, it is shielded from light. There is a problem that the work is complicated and not suitable for daily inspection from the viewpoint of safety and cost. In addition, when this technology is applied, it is difficult to determine whether or not the bypass diode has failed for the following reason. That is, even when the bypass diode does not have an open mode failure, when the solar cell is shielded from light, a certain amount of reverse voltage is applied to the solar cell, and heat generation of the solar cell may be observed. The degree of heat generation depends on the solar radiation intensity at that time, the light shielding state, the solar cell current density, the solar cell heat dissipation state, and the shunt resistance component of the solar cell. It is extremely difficult to distinguish between heat generation and heat generation due to a failure of the bypass diode. Therefore, there is a possibility that an open mode failure of the bypass diode cannot be accurately detected.

  Further, in the diagnostic method according to Patent Document 2, when there is no defect in the measurement target part, a large current corresponding to the voltage of the capacitor instantaneously flows to the measurement target part. It is not preferable also in terms of safety during measurement. Although it is conceivable to reduce the capacitance of the capacitor in order to reduce the large current at the measurement target portion, in this case, since the measurement time of the IV characteristic cannot be made long, accurate measurement of the IV characteristic is possible. In some cases, the accuracy of failure diagnosis may be reduced.

  Therefore, the present invention has been made in view of such problems, a failure detection device capable of accurately and easily detecting a failure of a bypass diode built in a solar cell module with a simple device configuration, failure An object is to provide a detection system and a failure detection method.

  In order to solve the above-described problem, a failure detection device according to one aspect of the present invention includes a solar cell that generates power using sunlight and at least one bypass diode connected in parallel to the solar cell, and is provided in a load. On the other hand, it is a failure detection device that detects a failure of a bypass diode for a solar cell module that is in a disconnected state, with a negative specified reverse voltage with respect to the positive electrode of the solar cell module as a reference. A voltage source to be applied, a current measuring unit for measuring a current value flowing from the negative electrode of the solar cell module toward the positive electrode when a reverse voltage is applied by the voltage source, and a bypass diode based on the current value measured by the current measuring unit. A determination unit for determining failure.

  Alternatively, a failure detection method according to another aspect of the present invention includes a solar cell that generates power using sunlight and at least one bypass diode connected in parallel to the solar cell, and is disconnected from the load. A failure detection method for detecting a failure of a bypass diode for a solar cell module in a state, in which a voltage application for applying a negative specified reverse voltage with respect to the negative electrode to the positive electrode of the solar cell module A current measurement step for measuring a current value flowing from the negative electrode of the solar cell module toward the positive electrode when a reverse voltage is applied in the voltage application step, and a failure of the bypass diode based on the current value measured in the current measurement step. A determination step for determining.

  According to such a failure detection device or failure detection method, a reverse voltage of a specified value is applied to a solar cell module that includes at least one bypass diode and is in a disconnected state with respect to a load. A current value flowing from the negative electrode of the module to the positive electrode is measured, and a failure of the bypass diode is detected based on the current value. That is, if the bypass diode is normal, a large current flows in the forward direction of the bypass diode in the solar cell module, and if the bypass diode has an open mode failure, only a small current flows in the solar cell module. Therefore, according to the above-described failure detection device or failure detection method, the presence or absence of a failure of the bypass diode can be determined with high accuracy by detecting the difference in the current value. Accordingly, since there is no need to trace the IV characteristic unlike the failure detection method using the capacitor, it is possible to accurately detect the failure of the bypass diode with a simple device configuration.

  In the failure detection apparatus described above, the determination unit has a current value measured in a state where the voltage of the first value is applied to the solar cell module as the prescribed value of the reverse voltage, which is smaller than the first threshold value. In some cases, it is preferable to detect a failure of the bypass diode. In this way, by comparing the measured current value with the threshold value, a failure of the bypass diode can be detected with a simple process and circuit configuration.

  Furthermore, the determination unit applies the reverse voltage to the solar cell module when the current value measured in a state where the reverse voltage of the specified value is applied to the solar cell module is equal to or greater than the second threshold value. It is also preferable to stop the operation. If such a determination unit is provided, it is possible to prevent a failure of the solar cell module caused by applying a high voltage to the solar cell module at the time of failure inspection. That is, if a constant current larger than the short-circuit current is passed through the solar cell module, there is a risk of generating a high voltage in the opposite direction to the voltage generated during power generation in the solar cell module. The generation of such a high voltage can be prevented by stopping the supply of current when the threshold value is 2 or more.

  Alternatively, the failure detection system according to another aspect of the present invention includes a plurality of solar cells connected in series that generate power using sunlight and at least one bypass diode connected in parallel to the plurality of solar cells. Failure detection for detecting a failure of a bypass diode in a solar cell system including a solar cell string including a plurality of solar cell modules connected in series and a load device connected to the solar cell string A switching unit that switches a connection between a solar cell string and a load device to a disconnected state, and a solar cell string that is switched to a disconnected state by the switching unit as a detection target string with respect to the positive electrode of the detection target string A voltage source that applies a negative specified reverse voltage with respect to the negative electrode, and Comprising a current measuring unit for measuring a current flowing from the negative electrode of the detection target string toward the positive electrode upon application, a determination unit failure of the bypass diode on the basis of the current value measured by the current measuring unit.

  Alternatively, the failure detection method according to another aspect of the present invention includes a plurality of solar cells connected in series that generate power using sunlight and at least one bypass diode connected in parallel to the plurality of solar cells. Failure detection for detecting a failure of a bypass diode in a solar cell system including a solar cell string including a plurality of solar cell modules connected in series and a load device connected to the solar cell string A switching step of switching a connection between a solar cell string and a load device to a disconnected state, and a solar cell string switched to a disconnected state by the switching step as a detection target string with respect to a positive electrode of the detection target string A voltage applying step for applying a negative specified reverse voltage with respect to the negative electrode, A current measurement step for measuring a current value flowing from the negative electrode to the positive electrode of the detection target string when a reverse voltage is applied in the application step, and a determination step for determining a failure of the bypass diode based on the current value measured in the current measurement step And comprising.

  According to such a failure detection system or failure detection method, a specified reverse voltage is applied to a solar cell string that includes at least one bypass diode and is switched in a disconnected state with respect to a load. A current value flowing from the negative electrode to the positive electrode of the solar cell string is measured, and a failure of the bypass diode is detected based on the current value. That is, if the bypass diode is normal, a large current flows in the forward direction of the bypass diode in the solar cell string, and if the bypass diode has an open mode failure, only a small current flows in the solar cell string. Therefore, according to the above-described failure detection system or failure detection method, the presence or absence of a failure of the bypass diode can be determined with high accuracy by detecting the difference in the current value. Accordingly, since there is no need to trace the IV characteristic unlike the failure detection method using the capacitor, it is possible to accurately detect the failure of the bypass diode with a simple device configuration.

  ADVANTAGE OF THE INVENTION According to this invention, the failure of the bypass diode built in the solar cell module with a simple apparatus structure can be detected with high accuracy.

It is a block diagram which shows the solar energy power generation system containing the failure detection system which concerns on 1st Embodiment of this invention. It is a figure which shows the detailed structure of the solar cell string contained in the solar energy power generation system of FIG. It is a figure which shows the equivalent circuit of the photovoltaic cell 140 of FIG. It is a graph which shows the current-voltage characteristic of the solar cell string of FIG. It is a graph which shows the current-voltage characteristic of the solar cell string of FIG.

  Hereinafter, embodiments of a failure detection device, a failure detection system, and a failure detection method according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is a configuration diagram of a solar power generation system according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a detailed configuration of a solar cell string included in the solar power generation system of FIG. A solar power generation system 1 shown in FIG. 1 is a power generation system that uses solar energy to generate power. For example, the solar power generation system 1 is installed in a high place such as a roof and has a grid connection type having an output voltage of 200 V or more. Has been. The solar power generation system 1 includes a solar cell array 100 and a power conditioner 110.
Note that it is not necessary to limit to a grid-connected system, and an independent system independent (independent) from the power system may be used.

  The solar cell array 100 converts solar energy into electric energy and supplies it to the power conditioner 110 as a DC output. As shown in FIG. 2, the solar cell array 100 includes at least one solar cell string 130 in which a plurality of solar cell modules 120 are connected in series. Here, the solar cell array 100 is configured by connecting three solar cell strings 130 to each other in parallel. These solar cell strings 130 are connected to the power conditioner 110 via a switch group of the failure detection system 2 described later.

  The power conditioner 110 converts the direct current output supplied from the solar cell array 100 into an alternating current output, and supplies the alternating current output to an electric power system (for example, a commercial electric power system) connected to the load device at the subsequent stage. The power conditioner 110 has an operating voltage control function for controlling the operating voltage of the solar cell array 100 so that the maximum output of the solar cell array 100 can be obtained, and the system is safely stopped when an abnormality in the power system is detected. System protection function. The power conditioner 110 may be a transformer insulation type having an insulation transformer or a transformerless (non-insulation) type.

  The solar cell module 120 is configured in a panel shape, and includes a plurality (six in this case) of solar cells 140 connected in series with each other as shown in FIG. Moreover, the solar cell module 120 includes a bypass diode 150 connected in parallel to the plurality of solar cells 140 connected in series. That is, the anode terminal of the bypass diode 150 is connected to the negative electrode side of the solar cell module 120, and the cathode terminal of the bypass diode is connected to the positive electrode side of the solar cell module. Note that the solar cell module 120 may include a plurality of solar cell clusters including a plurality of solar cells 140 and bypass diodes 150 connected in parallel to them.

  The plurality of solar cells 140 generate power using sunlight, and are fixed to the aluminum frame in a state of being arranged in a matrix, and the light receiving surface side is covered with tempered glass. As the solar cell 140, for example, a crystalline solar cell having an output voltage of 0.5V is used.

  The bypass diode 150 is connected to the plurality of solar cells 140 in parallel. As the bypass diode 150, for example, a Schottky barrier diode is used in order to reduce the forward voltage and shorten the reverse recovery time. The bypass diode 150 is provided such that a current flows when a reverse voltage is applied to the solar cell module 120, and its forward direction is the forward direction of the equivalent parasitic diode of the solar cell 140 in the solar cell module 120. On the other hand, it is the opposite direction. Specifically, the cathode side of the bypass diode 150 is connected to the positive electrode side of the solar cell module 120 on the electric circuit connecting the solar cell modules 120 in series. The anode side of the bypass diode 150 is connected to the negative electrode side of the solar cell module 120 on the electric circuit.

  FIG. 3 shows an equivalent circuit diagram of the solar battery cell 140. As shown in the figure, the solar cell 140 can be considered equivalent to a parallel circuit of a current source 141, a parasitic diode 142, and a shunt resistor 143. That is, the solar cell 140 has a current source 141 that generates a current corresponding to the solar radiation intensity from the negative electrode to the positive electrode inside the cell 140, and a direction from the positive electrode to the negative electrode inside the cell 140 as a forward direction. This is equivalent to a parasitic diode 142 and a shunt resistor 143 having a resistance value of several hundred to 1 kΩ (ideally infinite Ω). Due to the presence of the parasitic diode 142, a reverse current is generated in the solar cell 140 regardless of the solar radiation state. Further, when a current equal to or greater than the current generated by the current source 141 is generated in the solar cell 140 from the negative electrode to the positive electrode, the current flows through the shunt resistor 143 or the parasitic diode 142 breakdown. Either.

  Returning to FIG. 1, the configuration of the failure detection system 2 included in the solar power generation system 1 will be described. The failure detection system 2 is for detecting a failure of the bypass diode 150 incorporated in the solar cell string 130 for the solar cell string 130 that is switched to a disconnected state with respect to a load device such as the power conditioner 110. It is a device group. Specifically, the failure detection system 2 includes switch groups (switching units) 3 and 4 and a failure detection device 5.

  The switch group 3 is provided to switch the connection between the three solar cell strings 130 and the power conditioner 110 to the disconnected state when the bypass diode is inspected, and has six switching elements 31A and 31B corresponding to the number of the solar cell strings 130. , 32A, 32B, 33A, 33B. The switching elements 31 </ b> A, 31 </ b> B, 32 </ b> A, 32 </ b> B, 33 </ b> A, 33 </ b> B are switches that control the electrical connection between the solar cell string 130 and the power conditioner 110. As the switching elements 31A, 31B, 32A, 32B, 33A, and 33B, any configuration can be used as long as it cuts off the current. An electromagnetic switch such as a semiconductor switch or a mechanical relay can be used. The switching elements 31A, 31B, 32A, 32B, 33A, and 33B are closed during normal operation (during power generation), and connect the solar cell string 130 and the power conditioner 110 to each other, while being open during bypass diode inspection. And let them be disconnected from each other.

  Specifically, the switching elements 31A, 32A, and 33A are provided on an electric circuit that connects between the positive electrode of each solar cell string 130 and one input terminal of the power conditioner 110, and the switching elements 31B, 32B, and 33B. Is provided on an electric circuit that connects between the negative electrode of each solar cell string 130 and the other input terminal of the power conditioner 110. In addition, although the switch group 3 is provided on both electric circuits connected to the positive electrode and the negative electrode of the solar cell string 130, it may be provided only on one of the electric circuits. For example, the switch group 3 may be composed of only the switching elements 31A, 32A, and 33A. Even in such a configuration, the solar cell string 130 and the power conditioner 110 can be disconnected from each other during the bypass diode inspection.

  The switch group 4 is provided to electrically connect the three solar cell strings 130 and the failure detection device 5 during the bypass diode inspection, and includes six switching elements 41A corresponding to the number of the solar cell strings 130. , 41B, 42A, 42B, 43A, 43B. The switching elements 41A, 41B, 42A, 42B, 43A, and 43B are switches that control the electrical connection between the solar cell string 130 and the failure detection device 5, and are the same semiconductor switches and electromagnetic switches as the switch group 3. Can be adopted. The switching elements 41A, 41B, 42A, 42B, 43A, and 43B are normally opened (during power generation), and the failure detection device 5 is electrically disconnected from the solar cell string 130 while bypass diode inspection is performed. Sometimes they are closed and they are connected to each other.

  Specifically, the switching elements 41A, 42A, 43A are provided on an electric circuit that connects between the positive electrode of each solar cell string 130 and one connection terminal of the failure detection device 5, and the switching elements 41B, 42B, 43B. Are provided on the electric circuit connecting between the negative electrode of each solar cell string 130 and the other connection terminal of the failure detection device 5. In addition, although the switch group 4 is provided on both the electric circuits connected to the positive electrode and the negative electrode of the solar cell string 130, it may be provided only on one of the electric circuits. For example, the switch group 4 may be configured only from the switching elements 41A, 42A, and 43A. Even with such a configuration, the solar cell string 130 and the failure detection device 5 can be disconnected from each other at normal times.

  A backflow prevention diode (not shown) that prevents a reverse current from flowing through the solar cell string 130 is provided between the solar cell string 130 and the power conditioner 110. (Both poles) are connected in series on the electric circuit. The backflow prevention diode may be configured to be located in the electric circuit to be measured by the failure detection device 5 or may be configured to be located outside the electric circuit to be measured. That is, regardless of the position of the switch group 3 or the position of the connection points 61 to 66 with the failure detection device 5, it is located anywhere on the electric circuit connecting the positive electrode (or negative electrode) of the solar cell string and the power conditioner 110. (However, it is necessary to be located closer to the solar cell string 130 than the parallel connection point with the other solar cell strings 130).

  The failure detection device 5 includes a voltage source circuit 51, a current measurement unit 52, and a control / determination unit 53. The voltage source circuit 51 is a circuit that generates a constant voltage having a specified value. Here, the specified value of the voltage generated by the voltage source circuit 51 can be adjusted by control by the control / determination unit 53.

  The current measuring unit 52 is a circuit unit for measuring a current value flowing from the negative electrode of the solar cell string 130 toward the positive electrode. Here, the measurement timing of the current value by the current measurement unit 52 can be controlled by the control / determination unit 53, and a signal indicating the current value measured by the current measurement unit 52 is acquired by the control / determination unit 53. Has been made possible.

  The voltage source circuit 51 and the current measurement unit 52 are configured to be connected in series to the positive and negative electrodes of the three solar cell strings 130 via the switching elements 41A, 42A, 43A and the switching elements 41B, 42B, 43B. Has been. With such a configuration, the voltage source circuit 51 can apply a reverse voltage having a negative specified value with respect to the positive electrode with respect to the positive electrode to any one of the three solar cell strings 130, and the current measuring unit By 52, the current value in any one of the three solar cell strings 130 when the reverse voltage is applied can be measured.

  The control / determination unit 53 performs control so that the open / close state of the switch groups 3 and 4 is switched during a failure inspection of the bypass diode, and acquires a current value measured by the current measurement unit 52. Then, the control / determination unit 53 detects a failure of the bypass diode 150 built in any one of the solar cell strings 130 based on the acquired current value, and outputs a detection result. Such a control / determination unit 53 may be configured by a circuit unit such as an analog circuit or a digital circuit, or may be configured by an information processing apparatus such as a microcomputer.

  Here, before describing the details of the function of the control / determination unit 53, current-voltage characteristics (hereinafter referred to as "IV characteristics") when the solar cell string 130 is normal and when the bypass diode is faulty will be described.

  FIG. 4A is a graph showing the IV characteristic of the solar cell string 130 at night (at low solar radiation intensity), and FIG. 4B is one of the IV characteristics of FIG. 4A. It is a graph which shows a part in detail. In the figure, L1 indicates the IV characteristic of the solar cell string 130 when it is normal, and L2 indicates the IV characteristic of the solar cell string 130 when the bypass diode fails. In these characteristics, when the potential of the positive electrode of the solar cell string 130 is higher than the potential of the negative electrode, a positive voltage (V> 0) is indicated, and the current from the negative electrode to the positive electrode is positive in the solar cell string 130. Current (I> 0) is shown. Since the solar cell string 130 includes a plurality of bypass diodes 150 with the direction from the negative electrode to the positive electrode in the forward direction, when a reverse voltage (V <0) is generated at normal time, Almost no current flows through the shunt resistor 143 (FIG. 3) of the solar battery cell 140, and most of the current flows through the bypass diode 150 in the forward direction. As a result, the current I flowing from the negative electrode to the positive electrode in the solar cell string 130 increases rapidly (non-linearly).

On the other hand, when an open mode failure (failure in a state of not energizing) occurs in any of the bypass diodes 150 included in the solar cell string 130 and a reverse voltage (V <0) is generated at night, Since almost no current flows through the failed bypass diode 150 and current flows into the shunt resistor 143 of the solar cell 140 connected in parallel to the bypass diode 150, the current I in the solar cell string 130 is the magnitude of the voltage V. Increases almost linearly as the value increases. Here, since the shunt resistor 143 has a higher resistance than that of the normal bypass diode 150, the rate of increase of the current value is extremely small compared to the characteristic L1. Further, in the solar cell string 130, when short-circuited at both ends even (V = 0), the short-circuit current I _SC which changes according to the solar radiation condition occurs.

  The control / determination unit 53 determines a failure of the bypass diode 150 included in the solar cell string 130 using the IV characteristics of the solar cell string described above. Specifically, the control / determination unit 53 controls the switch group 3 so that the gap between any one of the solar cell strings 130 to be inspected (hereinafter also referred to as detection target strings) and the power conditioner 110. At the same time as setting the disconnected state, the switch group 4 is controlled to connect the detection target string 130 to the voltage source circuit 51 and the current measurement unit 52 of the failure detection device 5. For example, the control / determination unit 53 controls the pair of switching elements 31A and 31B, the pair of switching elements 32A and 32B, or the pair of switching elements 33A and 33B to be in an open state, and correspondingly The pair of switching elements 41A and 41B, the pair of switching elements 42A and 42B, or the pair of switching elements 43A and 43B is controlled to be closed.

In this state, the control / determination unit 53 controls the voltage source circuit 51 to apply the reverse voltage of the negative specified value V ₁ with respect to the negative electrode to the positive electrode of the detection target string 130. The specified value V ₁ is a value that is not significantly larger than the total forward voltage VF of the bypass diode 150 included in the detection target string 130, and is an appropriate value that can distinguish the characteristics L 1 and L 2 shown in FIG. It is set in advance. Further, the control / determination unit 53 determines whether or not the current value of the detection target string 130 measured by the current measurement unit 52 is smaller than a predetermined threshold value I _TH0, and when the current value is smaller than the threshold value I _TH0. The failure of any bypass diode 150 included in the detection target string 130 is detected. With such a function of the control / determination unit 53, it is possible to determine which of the characteristics L1 and L2 shown in FIG. 4 the IV characteristic of the detection target string 130 is, and the IV characteristic is the characteristic. A failure of the bypass diode 150 can be detected when it is determined as L2. That is, since the current value measured by the current measuring unit 52 corresponds to the magnitude of the current I with respect to the voltage V = −V ₁ on the characteristics L1 and L2, the current value and the threshold value I _TH0 are compared. Thus, it is possible to determine whether the IV characteristic of the detection target string 130 is in the characteristic L1 or L2.

The threshold value control / determination section 53, the current value of the detection target string 130 measured by the current measurement unit 52 when obtained by applying a reverse voltage of defined value V ₁ to the detection target string 130, which is defined in advance When it becomes equal to or higher than I _TH1 (> threshold I _TH0 ), control is performed so that the application of the reverse voltage to the detection target string 130 by the voltage source circuit 51 is stopped. At this time, the control / determination unit 53 starts monitoring the current value of the detection target string 130 at the timing when the open / close state of the switch groups 3 and 4 is switched in order to check the failure of the bypass diode. Accordingly, it is continuously determined whether or not to stop applying the reverse voltage to the detection target string 130.

  Next, the failure inspection procedure for the bypass diode 150 targeting the above-described photovoltaic power generation system 1 will be described, and the failure detection method according to the present embodiment will be described in detail.

First, the control / determination unit 53 of the failure detection device 5 determines whether or not a predetermined time has arrived by using a built-in timing function, and checks for a failure of the bypass diode at the timing when the arrival of the predetermined time is detected. Processing begins. For example, since the very small the I-V characteristic short-circuit current value I _SC of the solar cell string 130 at the timing of arrival of night time is detected is stable, bypassed by the fault test process is started at this timing False detection of a diode failure is prevented.

  Next, the switch groups 3 and 4 are controlled by the control / determination unit 53 to set the disconnection state between any one of the detection target strings 130 and the power conditioner 110, and at the same time, the detection target string 130. Are connected to the failure detection device 5 (first switching step). Here, when set to the disconnected state, both poles of the detection target string 130 may be cut, or only the direction pole side of the detection target string 130 may be cut.

Thereafter, the detection target string 130 from the voltage source circuit 51 of the failure detection device 5, a reverse voltage of defined value V ₁ is applied between the negative electrode and the positive electrode (voltage application step). At this timing, the current measurement unit 52 measures the current value flowing from the negative electrode of the detection target string 130 toward the positive electrode, and passes the measurement value to the control / determination unit 53 (current measurement step). On the other hand, the control / determination unit 53 determines whether or not the current value is smaller than a predetermined threshold value I _TH0, and based on the determination result, any of the bypass diodes 150 included in the detection target string 130 is determined. A failure is detected (judgment step). Then, the control / determination unit 53 outputs the detection result to an output device such as a display or an LED (output step). Finally, when a failure of the bypass diode is not detected (when the bypass diode is determined to be normal), the control / determination unit 53 controls the switch groups 3 and 4 to detect the detection target string 130 and the failure detection. At the same time as the connection with the device 5 is released, the connection between the detection target string 130 and the power conditioner 110 is set to the connected state (second switching step).

According to the failure detection system 2 and the bypass diode failure detection method using the failure detection system 2 described above, the reverse voltage of the specified value V ₁ is applied to the solar cell string 130 in the disconnected state with respect to the load device. At that time, the current value flowing from the negative electrode to the positive electrode of the solar cell string 130 is measured, and a failure of the bypass diode 150 is detected based on the current value. That is, if bypass diode 150 is normal, a forward current flows through bypass diode 150 in solar cell string 130 according to the IV characteristics of the bypass diode. On the other hand, if the bypass diode 150 fails in the open mode, only the shunt resistor in the solar cell string 130 allows current to pass. The latter current value is significantly smaller than the former. Therefore, according to the failure detection method using the failure detection system 2 described above, the presence or absence of a failure of the bypass diode 150 can be determined with high accuracy by detecting the difference in the magnitude of the current value. Thus, since there is no need to trace the IV characteristic unlike the failure detection method using a capacitor, the failure of the bypass diode 150 can be accurately detected with a simple device configuration.

In the failure detection system 2 described above, a failure of the bypass diode 150 is detected when the current value measured with respect to the solar cell string 130 is smaller than the threshold value _ITH0. Can be detected.

Further, when the current value measured with respect to the solar cell string 130 becomes equal to or greater than the threshold value _ITH1 , the application of the reverse voltage to the solar cell string 130 is stopped, so that an overcurrent is passed through the solar cell string 130 at the time of failure inspection. The failure of the solar cell string 130 due to this can be prevented. That is, when the bypass diode applies a reverse voltage to the normal solar cell string 130, an overcurrent larger than the short-circuit current may be generated. However, if the current value of the solar cell string 130 becomes too large, the reverse current is reversed. By stopping the application of voltage, the occurrence of such overcurrent can be prevented.

  In addition, this invention is not limited to embodiment mentioned above. For example, the control / determination unit 53 applies two or more kinds of specified value voltages to the detection target string 130, and detects based on the current value measured by the current measuring unit 52 for each specified value. A failure of the bypass diode may be detected by determining whether the IV characteristic of the target string 130 is linear.

Specifically, in order to determine the IV characteristics L1 and L2 of the detection target string 130 as illustrated in FIG. 5, the control / determination unit 53 sets a positive prescription based on the negative electrode to the positive electrode of the detection target string 130. obtains the current value -I2 measured voltage value V ₂ when supplied, to obtain a current value I1 measured at the time of applying a reverse voltage of negative prescribed value V ₂ to the detection target string 130 . The control / determination unit 53 also acquires a current (short-circuit current) I _SC (> 0) generated in the detection target string 130 when the applied voltage is 0. Then, the control / judging unit 53 refers to the acquired potential difference _{I2, I1, I SC, I2} + compared to the value of _{I SC I1-I SC} value is the specified value or higher is greater if the bypass diode are determined to be normal . On the other hand, the control / judging unit 53, as I2 _{+ I SC} value and the absolute value of the I-V characteristic of the detection target string 130 is less than the specified value of the difference between the value of _{I1-I SC} is linear, bypass diode Is determined to be abnormal.

  However, when the measurement that generates the reverse current is included in this manner, it is necessary to exclude the backflow prevention diode from the detection target string 130 and detect it.

  As described above, a failure of the bypass diode may be detected by measuring currents corresponding to the three voltages and determining linearity.

The control / determination unit 53 may determine whether or not the detection target string 130 is actually generating power when determining the start timing of the failure inspection process for the bypass diode. That is, the control / determination unit 53 acquires the short-circuit current value I _SC measured by the current measurement unit 52 immediately after the first switching step, and compares the short-circuit current value I _SC with the specified value. It is determined whether or not the detection target string is generating power. If the detection target string is not generating power, a failure inspection process for the bypass diode is started. For example, the control / determination unit 53 determines that the detection target string 130 is not generating power when the measured short-circuit current value _ISC is smaller than a specified value. Further, the control / determination unit 53 may determine whether or not the detection target string 130 is generating power based on the ratio of the measured short-circuit current value _{ISC to} the specified value.

  Furthermore, as another embodiment, only the failure detection device 5 in FIG. 1 may be prepared as an independent portable device and connected to a solar cell string, a solar cell module, or a solar cell cluster for detection.

  In the above embodiment, the method of performing detection at night has been described. However, by setting the current detection threshold value to a value larger than the short-circuit current of the solar cell, the applied voltage uses the same value as in the case of performing detection at night. However, it can also be detected in the daytime.

  DESCRIPTION OF SYMBOLS 1 ... Solar power generation system (solar cell system), 2 ... Failure detection system, 3 ... Switch group (switching part), 5 ... Failure detection apparatus, 51 ... Voltage source circuit, 52 ... Current measurement part, 53 ... Control / determination Part, 61-66 ... connection point, 100 ... solar cell array, 110 ... power conditioner (load device), 120 ... solar cell module, 140 ... solar cell, 150 ... bypass diode.

Claims (6)

The bypass diode includes a solar cell that generates power using sunlight and at least one bypass diode connected in parallel to the solar cell, the solar cell module being in a disconnected state with respect to a load. A failure detection device for detecting a failure of
A voltage source for applying a negative specified negative voltage with respect to the negative electrode with respect to the positive electrode of the solar cell module;
A current measuring unit that measures a current value flowing from the negative electrode of the solar cell module toward the positive electrode when a reverse voltage is applied by the voltage source;
A determination unit that determines a failure of the bypass diode based on the current value measured by the current measurement unit;
A failure detection apparatus comprising: The determination unit is configured when the current value measured in a state where a voltage having a first value is applied as the specified value of the reverse voltage to the solar cell module is smaller than a first threshold value. Detecting bypass diode failure,
The failure detection device according to claim 1. When the current value measured in a state in which the reverse voltage of the specified value is applied to the solar cell module is equal to or greater than a second threshold, the determination unit reverse voltage to the solar cell module The application of
The failure detection device according to claim 1, wherein A plurality of solar cell modules including a plurality of solar cells connected in series that generate power using sunlight and at least one bypass diode connected in parallel to the plurality of solar cells are connected in series. A failure detection system for detecting a failure of the bypass diode for a solar cell system comprising a solar cell string and a load device connected to the solar cell string,
A switching unit that switches the connection between the solar cell string and the load device to a disconnected state;
A voltage source that applies a reverse voltage of a negative specified value with a negative electrode as a reference to a positive electrode of the detection target string, with the solar cell string switched to a disconnected state by the switching unit as a detection target string;
A current measuring unit that measures a current value flowing from the negative electrode to the positive electrode of the detection target string when a reverse voltage is applied by the voltage source;
A determination unit that determines a failure of the bypass diode based on the current value measured by the current measurement unit;
A failure detection system comprising: The bypass diode includes a solar cell that generates power using sunlight and at least one bypass diode connected in parallel to the solar cell, the solar cell module being in a disconnected state with respect to a load. A failure detection method for detecting a failure of
A voltage application step of applying a reverse voltage of a negative specified value with reference to the negative electrode to the positive electrode of the solar cell module;
A current measurement step of measuring a current value flowing from the negative electrode to the positive electrode of the solar cell module when applying a reverse voltage in the voltage application step;
A determination step of determining a failure of the bypass diode based on the current value measured by the current measurement step;
A failure detection method comprising: A plurality of solar cell modules including a plurality of solar cells connected in series that generate power using sunlight and at least one bypass diode connected in parallel to the plurality of solar cells are connected in series. A failure detection method for detecting a failure of the bypass diode targeting a solar cell system comprising a solar cell string and a load device connected to the solar cell string,
A switching step of switching the connection between the solar cell string and the load device to a disconnected state;
A voltage application step of applying a negative specified negative voltage with a negative polarity as a reference to a positive electrode of the detection target string, with the solar cell string switched to a disconnected state by the switching step as a detection target string;
A current measurement step of measuring a current value flowing from the negative electrode to the positive electrode of the detection target string when a reverse voltage is applied by the voltage application step;
A determination step of determining a failure of the bypass diode based on the current value measured by the current measurement step;
A failure detection method comprising:

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