JP2013135030A - Power generation cell system circuit and power generation system using the circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a highly safe and reliable power generation system with a simple circuit configuration, with no requirement of a specific complex circuit structure with a large number of components.SOLUTION: A power generation cell system circuit includes: plural generation circuit parts each comprising a generation cell body constituted by one or two or more generation cells 1 and a first bypass diode 2, parallelly connected to the generation cell body, capable of bypassing a power feed thereto; and a current bypass circuit, comprising one or two or more second bypass diodes 3, being parallelly connected to a first diode string produced by serially connecting two or more of the first bypass diodes 2 of the generation circuit parts. Further, when the current bypass circuit applies power in a rectifying operation, a threshold voltage is higher than a value at the first bypass diode 2 itself and less than a total value of all the first bypass diodes 2.

Description

  The present invention includes a solar cell that converts light such as sunlight into electric power, a power generation cell system circuit using power generation cells such as a fuel cell and a thermoelectric conversion element, and a power generation array in which a plurality of the power generation cell system circuits are connected. It is related with the electric power generation system provided with.

  As the demand for energy saving technology and load leveling technology increases toward a low-carbon society, interest in power generation systems that can generate clean energy on-site is increasing.

  Among these systems, for example, when using a solar battery, a unit called a cell (solar battery cell) composed of a solar battery that generates power such as single crystal silicon, polycrystalline silicon, amorphous silicon, CIGS, and a plurality of these units. Modules (panels) configured as a single unit by connecting solar cells in series and parallel by wiring, and a plurality of modules in series and parallel by cables to form an assembly of modules called an array, which is necessary in the system It is designed to output voltage and current. When installing in a general residence, install the module unit on the roof and wire it, connect the cables that energize each module to a terminal called a connection box, consolidate them, and use a power control converter in the subsequent stage of the connection box. A certain power conditioner is installed to convert the voltage to DC or AC and link to the system, and it is used as stable power.

  Normally, it is often installed in a place such as a roof where it is not easily accessible, so it is not easy to remove flying objects such as fallen leaves and dust attached to the surface of the module. However, these projectiles not only become a factor that significantly impedes the power generation efficiency of each solar cell when generating solar power, but the amount of power generated by the solar cells in the area where the projectiles adhere greatly decreases between solar cells. It is known that an electric resistor is equivalent in the electric circuit constituted by

  There is only a power generation voltage of 0.6 to several V (volts) in units of solar cells, and in order to obtain a desired voltage, it is common to configure modules by connecting tens to hundreds of solar cells in series. However, the portion of the solar cell to which dust is attached has an increased electrical resistance value and generates Joule heat. This part is called a hot spot, etc. If left unattended, it will cause deterioration of the performance of the solar cell, poor connection due to melting of the solder connected to the wiring, deterioration of peripheral members, and in some cases to adjacent solar cells The influence of heat spread and the damage was spreading. In order to avoid such problems, bypass diodes are connected in parallel to individual solar cells or a series of a plurality of solar cells connected in series. When the resistance increases and exceeds the threshold voltage of the bypass diode, current flows around the bypass circuit. Thereby, since the electric current which flows into a high resistance photovoltaic cell decreases, heat_generation | fever can be suppressed. As the bypass diode, a silicon diode is generally used, and a pn junction diode or a Schottky barrier diode is used. In recent years, a case where a Schottky barrier diode with a low threshold voltage and a small loss during energization is used is increasing. In many cases, the diodes are concentrated and arranged in a terminal box on the back of the module in units of modules (see Non-Patent Document 1).

  Even if a current is diverted to these bypass diodes, the electrical resistance of the diodes themselves is present, so it is necessary to handle them with great care. In general, in a DC circuit, a power loss is a value obtained by multiplying a voltage drop at the time of forward energization of a diode and an energization current value.

  In some cases, the bypass diodes generate heat beyond the allowable range or the heat affects the members such as terminals and solder in the terminal box. In order to prevent these problems, as a conventional technique, Patent Document 1 reports a method of connecting a thermal switch connected in parallel to a bypass diode, detecting the heat generated by the diode, and short-circuiting both ends of the diode. . Patent Document 2 discloses a method of solving a problem of heat generation of a diode by suppressing a characteristic variation of each diode by arranging a plurality of bypass diodes in parallel and sealing the diodes with a resin.

JP 2005-175370 A Japanese Patent Laid-Open No. 11-298022

"Design and construction of solar power generation system" Ohm, July 25, 1996 1st edition

  In the method of providing bypass diodes in units of individual solar cells or in units of several tens of solar cells, in order to prevent heat generation due to power loss of the solar cells when a part of the surface of the module (panel) becomes dirty Although effective, when a power generation failure occurs in a larger-scale solar cell, adjacent bypass diodes in the terminal box generate heat and affect members in the terminal box. In addition, when a shadow covering the entire module is created on a larger scale, many bypass diodes related to the module may generate heat when viewed between the arrays. Specifically, this includes the growth of garden trees adjacent to the module, the thickening of seasonal trees, the shadow of newly built buildings, and the fluctuation of the sunlight incident path depending on the season.

  In order to prevent heat generation of the bypass diode, there is a method in which individual bypass diodes are arranged in parallel and the current value flowing individually is suppressed as a prior art. However, a large amount of bypass diodes are required, which is uneconomical. In addition, a method of detecting the heat generation of the diode and short-circuiting both ends of the bypass diode has been proposed, but the reliability is reduced due to the failure of the detection circuit and the switchgear under the condition that it is used outdoors, or many parts are required. It was uneconomical.

  In view of the above-described problems, the present invention does not require a special and complicated circuit configuration with a large number of parts, and suppresses heat generation of the bypass diode with a simple circuit configuration, thereby obtaining a highly reliable power generation system. For the purpose.

The present invention is summarized as follows in order to solve the above problems.
(1) A power generation circuit unit having a power generation cell body composed of one or more power generation cells, and a first bypass diode that is connected in parallel to the power generation cell body and can bypass energization to the power generation cell body A power generation cell system in which a plurality of current bypass circuits having one or more second bypass diodes are connected in parallel to a first diode row in which two or more first bypass diodes in a power generation circuit section are connected in series A circuit,
The threshold voltage V _th when the current bypass circuit is energized by rectification when the forward voltage drop in the first bypass diode alone is V _f satisfies the following relational expression (1): System circuit.
V _f × n> V _th > V _f (1)
(Where n represents the number of first bypass diodes forming the first diode row, and n ≧ 2.)
(2) The power generation cell system circuit according to (1), wherein the second bypass diode is a bipolar diode made of a wide band gap semiconductor material.
(3) A power generation system comprising a power generation array in which two or more power generation cell system circuits according to (1) or (2) are connected in series.

  According to the present invention, dust or the like adheres to a plurality of power generation cells, or the entire module is soiled or hidden in the shade with little reflected light, and other power generation cells and modules are exposed to sunlight. In order to avoid the occurrence of a malfunction due to the influence of heat generated by a plurality of first bypass diodes connected to a power generation cell that has stopped generating power at the same time (ON) during power generation. By forming the further bypass circuit by turning on the 2 bypass diode, the heat generation of the first bypass diode can be mitigated and prevented, and the safety of the system can be ensured. In addition, since it can be configured with only passive components such as diodes, control is unnecessary and reliability is high.

The figure concerning the 1st Embodiment of this invention. The figure concerning the module external appearance of the 1st Embodiment of this invention. The figure for demonstrating the whole system of the 1st Embodiment of this invention. The figure for demonstrating the operation | movement of the 1st Embodiment of this invention. The figure for demonstrating the structure of a prior art. The current voltage graph figure for demonstrating operation | movement of the 1st Embodiment of this invention. The figure concerning the 2nd Embodiment of this invention. The figure for demonstrating the whole system of the 2nd Embodiment of this invention. The figure for demonstrating operation | movement of the 2nd Embodiment of this invention. The figure in connection with the 3rd Embodiment of this invention. The figure in connection with the 4th Embodiment of this invention. The figure in connection with the 5th Embodiment of this invention. The figure in connection with the 5th Embodiment of this invention. The figure for demonstrating the 5th operation | movement of this invention.

Hereinafter, the present invention will be described in detail.
The present invention provides a power generation circuit unit having a power generation cell body composed of one or more power generation cells, and a first bypass diode that is connected in parallel to the power generation cell body and can bypass energization to the power generation cell body. A power generation cell in which a current bypass circuit having one or more second bypass diodes is connected in parallel to a first diode row in which two or more first bypass diodes in the power generation circuit unit are connected in series The system circuit. For example, when the power generation cell is a solar cell, a current bypass circuit with a small power generation failure such as a part of the power generation cell body where dust or the like adheres to it or is hidden in the shade When the second bypass diode that forms is turned on, all the solar cells related to the parallel connection of the second bypass diode are short-circuited, so that the solar cells that can generate power are wasted. In such a situation, it is not necessary to turn on the second bypass diode, and it is only necessary to form a bypass with only the first bypass diode. In the following description, the power generation cell is described as a solar cell, but the present invention can also be applied to a fuel cell, a thermoelectric conversion element, or the like. That is, in a power generation cell having a failure mode in which the internal resistance increases or becomes an open state, the power generation cell system circuit including the first bypass diode and the second bypass diode in the present invention is formed, thereby bypassing A highly reliable power generation system can be obtained while suppressing heat generation of the diode.

Therefore, in the present invention, the threshold voltage for turning on the current bypass circuit having one or more second bypass diodes is set as the forward threshold voltage of each first bypass diode constituting the first diode row to be connected in parallel. And determined according to the total. Specifically, in the assumed system power generation current value Ist, for example, the forward voltage drop of one first bypass diode is V _f , and at both ends of a first diode row in which n first bypass diodes are connected in series. When a current bypass circuit composed of one or more second bypass diodes is connected in parallel, the threshold voltage V _th when the current bypass circuit is energized by rectification is designed in the following relationship.
V _f × n> V _th > V _f (Formula 1)

  As apparent from (Equation 1), even if one first bypass diode is turned on and a forward voltage drop occurs, the voltage across the current bypass circuit is equal to or lower than the threshold voltage, so that a second current bypass circuit is formed. The bypass diode is not turned on. In a situation where all of the n first bypass diodes connected to the second bypass diode are turned on, the forward voltage of the first diode row exceeds the threshold voltage of the current bypass circuit, so that the first current bypass circuit is formed. (Equation 1) means that the 2 bypass diode is turned on to form a further bypass. It should be noted that even if the current bypass circuit forms a bypass, the case where a part of the current does not flow to the current bypass circuit but partially flows to the first diode row is also included.

The position of the current bypass circuit is determined by the arrangement and performance of the first bypass diode to be protected. Specifically, in the case of protecting several to several tens of solar cells, the second bypass diodes may be connected in parallel across the series circuit (first diode row) of the first bypass diodes related to them. Good. The group may be protected collectively by connecting in parallel to the first diode row in which the first bypass diodes corresponding to one module (panel) or a part of the array are bundled. That is, the number of power generation circuit units protected by the current bypass circuit can be arbitrarily selected. For example, the current bypass circuit is connected to the first diode row of the module unit, or the first diode row of the plurality of modules. The current bypass circuit may be connected so as to be managed collectively. When managing a plurality of modules collectively, the total threshold voltage of the first diode array in module units (V _f × m when the first diode array of each module is composed of m first bypass diodes) is calculated. If it exceeds, the current bypass circuit may be energized by rectification.

  The second bypass diode forming the current bypass circuit protects the first diode array in which a plurality of first bypass diodes are connected in series from the relationship of (Equation 1), and the threshold voltage is set to some extent in order to turn on at an appropriate value. For example, the threshold voltage of a silicon diode is usually about 0.2 to 1.0 V. In this case, a plurality of second bypass diodes are connected in series and the threshold voltage of the current bypass circuit is desired. It is necessary to configure so that the voltage is Specifically, the threshold voltage of the column of the second bypass diodes configured by serializing a plurality of diodes can be obtained by adding the threshold voltages of the individual diodes.

  The second bypass diode is preferably a PN junction type diode formed of a wide band gap semiconductor. When a pn-type diode is made of a wide band gap semiconductor made of silicon carbide, GaN, or the like, it is known that the threshold voltage is about 2.5 to 3.0 V, so a current bypass circuit is formed. When used as the second bypass diode, there is an advantage that a series circuit can be configured with a smaller number than the number of silicon diodes. Furthermore, wide bandgap semiconductors have excellent semiconductor characteristics such as operation at a high temperature of 500 ° C., so that they are hardly affected by heat generation and can form a highly reliable circuit.

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

FIG. 1 is a block diagram for explaining a first embodiment of the present invention.
Reference numeral 1 denotes a solar battery cell which is formed of approximately 150 mm square polycrystalline silicon, has a rated output operating voltage of about 0.6 V / sheet during solar power generation, and a rated current value of about 8.0 A. . Reference numeral 2 denotes a first bypass diode, which is a silicon Schottky barrier diode, and has a forward voltage (potential difference between both ends of the diode) of 0.4 V when the conduction current is 8A. In the example of FIG. 1, one solar battery cell 1 constitutes a power generation cell body, and each solar battery cell is connected in parallel with a first bypass diode to form a power generation circuit unit. ing. Reference numeral 3 denotes a second bypass diode composed of a silicon PN-type junction diode (bipolar diode) having a threshold voltage (V _th ) of 1.0 V, and a first diode array in which four first bypass diodes are connected in series. One is connected in parallel to form a current bypass circuit.

  Reference numeral 5 denotes a circuit group (power generation cell system circuit) including each of the solar battery cell 1, the first bypass diode 2, and the second bypass diode 3, and the circuit group 4 before and after 5 and the circuit group 6 are also shown in the drawing. Although omitted, the circuit configuration is the same as that of the circuit group 5. When each photovoltaic cell 1 is performing photovoltaic power generation, the generated current flows through the terminal 7 and each photovoltaic cell and flows to the terminal 10.

  An external view of a solar cell panel having these circuit configurations is shown in FIG. 1-1. One module M1 is formed of a matrix of solar cells 3 × 4. At the time of power generation by sunlight, current flows along the path of the dotted line 11. In forming the module, a publicly known method such as a panel formed by sandwiching solar cells between a protective substrate, a weather-resistant film or the like, or integration by a resin mold can be employed.

  FIG. 2 is a diagram showing the entire power generation system including the module M1, and the generated power is a power conditioner 13 that converts a DC voltage into an AC voltage via a connection box 12 in which wiring is aggregated through terminals 7 and 10. Connected to. Note that the first bypass diode and the second bypass diode described in FIG. 1 are collectively arranged in a terminal box installed on the back surface of the module.

  The operation of each first bypass diode in FIG. 1 will be described in detail with reference to FIG. FIG. 3B shows the circuit group 5 in FIG. 1, and in a situation where all the solar cells receive sunlight and generate a rated current of 8 A, the generated current is route 11. -Flows through B. The figure (B ') has shown the surface state where the sunlight of a module panel hits. In this case, since there is no obstacle to shade sunlight, the current flows to the solar cell without bypassing the circuit of the first bypass diode.

  FIG. 3C shows a case where one solar cell 1C-1 is intentionally covered with a black cloth with respect to the state of FIG. In this case, since the solar cell 1C-1 does not contribute to power generation and becomes a simple resistor on the circuit, the current flows around the 2C first bypass diode. At this time, the potential difference generated at both ends of the second bypass diode is a value obtained by adding a slight voltage drop due to the resistance of the wiring to the voltage 0.4V corresponding to the forward voltage of the first bypass diode at 8A. It does not reach the potential difference of voltage 1.0V or more and does not conduct.

  FIG. 3D shows a case where a black cloth is attached to all the rows of solar cells in the circuit group 5. In this state, while the circuit groups 4 and 6 are operating at the rated value, the solar cell group 1D-A of the circuit group 5 is an electric resistor in the entire system. FIG. 4 shows a conventional technique showing a case where the second bypass diode does not exist in the state of FIG. As indicated by 11E in FIG. 4, all the first bypass diodes 2E-A are turned ON, and the current is bypassed. If this state continues, the first bypass diode generates heat due to the power loss of the diode.

  However, in the circuit of FIG. 3D of the present invention, at the rated current of 8A, the total forward voltage of the first bypass diode connected in series exceeds the threshold voltage of the second bypass diode of 1.0V. In addition, the second bypass diode is also turned on at the same time, and the current is commutated. In this case, the current of the first bypass diode is reduced, the power loss is reduced, and the heat generation amount is also reduced.

  The above operation will now be described again on the graph of FIG. FIG. 5 is a diagram showing current-voltage characteristics (IV characteristics) of the diode at room temperature. In the figure, IV-1 is the IV characteristic of the Schottky barrier diode alone of the first bypass diode, IV-2 is the IV characteristic when four first bypass diodes are connected in series, and IV-3 is the second bypass diode PN This is the IV characteristic of a single type diode.

  In the rated operating current 8A in the state of FIG. 3C, the potential difference between both ends of the second bypass diode 3C is 0.4V which is a forward voltage of one first bypass diode that can be read from IV-1, and wiring However, the voltage does not exceed 1.0 V, which is the threshold voltage of the second bypass diode that can be read from IV-2. For this reason, the second bypass diode did not conduct.

  In the situation corresponding to FIG. 3D, the forward voltage at 8A of the four first bypass diodes is about 1.6 V so that it can be read from IV-2. Before reaching this voltage, the second bypass diode is turned on because the threshold voltage of 1.0 V across the second bypass diode is exceeded. As a result, current flows in parallel through the first bypass diode and the second bypass diode. As a result, the current of the first bypass diode is reduced and heat generation can be suppressed. Although the second bypass diode also generates heat, since it is bipolar, conduction modulation occurs due to minority carrier injection, and the current after ON rises rapidly as indicated by IV-3 in FIG. 5, resulting in the second bypass diode. This is smaller than the potential difference of the forward voltage of the first bypass diodes 4 rows not connected to each other. In principle, the potential difference in the forward direction of the entire bypass circuit in parallel is obtained in principle by combining 2D-A and 3D, but the current-voltage characteristics (IV characteristics) of semiconductors are temperature dependent. It is difficult to find exactly with simple calculations. Therefore, as a concrete design method, a realistic design method is to select a diode in the above (Equation 1), mount it, and check the operating point while observing the operation of the diode on the circuit.

  The power loss of the entire bypass diode circuit (first diode array) during the experiment with the configuration of FIG. 3 can be obtained from the voltage and current measurement between the terminals, and states 3.6 W and (D) in FIG. It was 10.4W in the state. In FIG. 4 corresponding to the conventional technique, it was 12 W.

  As in the above-described embodiment, the first bypass diode is operated against a failure that occurs partially in each of the solar cells, and the solar cells are bypassed to protect the solar cells from destruction. . By connecting a second bypass diode to a wide range of light blocking faults related to a plurality of first bypass diodes and forming a new detour, the power loss of the entire system can be reduced, and the first bypass diode By reducing the thermal burden of the circuit, it is possible to prevent the occurrence of circuit failure.

  FIG. 6 shows a second embodiment of the present invention. The solar battery cell 1F is formed of approximately 150 mm square polycrystalline silicon as in FIG. 1, has a rated operating voltage during power generation of 0.6 V / sheet, and a rated current value of approximately 8.0 A. 2F-1 is a first bypass diode, and a power generation circuit unit 4F is configured by connecting one first bypass diode in parallel to a power generation cell body composed of 16 solar cells. The configuration related to the first bypass diodes 2F-2 and 2F-3 is exactly the same as that of the power generation circuit unit 4F, and configures a power generation circuit unit 5F and a power generation circuit unit 6F, respectively. At the time of photovoltaic power generation, current flows from the terminal 14 to each solar battery cell, and is connected from the 17 terminal to the load ahead. The first and second bypass diodes used in this embodiment are all PN-type bipolar diodes of the same type of silicon. The basic characteristics are a threshold voltage of 1.0 V and individual forward directions when a current of 8 A is applied. The voltage is 1.2V.

  The second bypass diode in the above configuration is connected in parallel to the first diode row in which the first bypass diodes of the power generation circuit units 4F, 5F and 6F are connected in series to form a current bypass circuit. In order to comply with the above (Equation 1), the threshold voltage of the first bypass diode is larger than the forward voltage 1.2V when the current of each 8A is energized, and less than 3.6V, which is three times the forward voltage. There must be. In order to satisfy this condition, the second bypass diode has two diodes 3F-1 and 3F-2 having a threshold voltage of 1.0 V connected in series. As a result, the threshold value of the second bypass diode serialized is 2.0 V, which satisfies the above (Equation 1).

  FIG. 6 (F ′) is an external view of the above-described circuit of FIG. 6 (F) formed as a module. The total number of solar cells in the entire system is formed by 48 modules connected in series to form one module M2. doing. In addition, three modules having the same configuration as this module were prepared, and a system in which three modules M2, M3, and M4 were connected in series as shown in FIG. 7 was constructed. 18 is a junction box, and 19 is a power conditioner.

  In order to confirm the effectiveness of the present invention with the above system, as shown in FIG. 8 (F ′), it corresponds to eight solar cells in the power generation circuit units 6F and 5F and the power generation circuit unit 4F in the module M2. The part to be covered was covered with a black cloth (gray part in the figure), and solar power generation with a rated current of 8 A was performed as a whole system. Module M3 and module M4 have nothing to block sunlight. As a result, before covering the black cloth as in the state of FIG. 6, current did not flow through each of the first and second bypass diodes, but a part of the sun as shown in FIG. 8 (F ′). When the battery cell was covered with black cloth, the first bypass diode and the second bypass diode were turned on, and the current flowing in the solar battery cell started to commutate. In this state, the temperature of each individual bypass diode was measured. The first bypass diode was about 30 ° C., and the second bypass diode was 80 ° C. The difference in temperature is considered to be because most of the current commutated to the second bypass diode. In view of such a case, it is preferable from the viewpoint of reliability that the first bypass diode and the second bypass diode are installed in a thermally isolated place. In this embodiment, two terminal boxes are provided on the back surface of the module, and the first bypass diode and the second bypass diode are respectively stored.

  FIG. 9 is a block diagram showing the third embodiment. The arrangement of the solar cell and the first bypass diode in the figure is the same as that of the second embodiment, but the second bypass diode is changed to a SiC PN-type diode 3F-S. SiC has a higher threshold voltage than that of the silicon PN type diode, and 2.5 V is used in this embodiment. The conditions other than the change of the second bypass diode were the same as those in the second example, and a black cloth was placed on the solar cell as shown in FIG. As a result, the first bypass diode and the second bypass diode were turned on, and commutation of the current flowing in the solar battery cell was started. In this state, the temperatures of the individual bypass diodes were measured. The average of the first bypass diodes was about 50 ° C., and the second bypass diodes were 50 ° C. Unlike the second example, the temperature was almost the same. This is because the SiC diode is the second bypass diode, and the threshold voltage is 2.5 V higher than 2.0 V in the second embodiment, so that the rise of the current with respect to the voltage is delayed, and the current flows to both the first bypass diode and the second bypass diode. It is thought that it flowed.

  FIG. 10 is a block diagram showing the fourth embodiment. The arrangement of solar cells and second bypass diodes in the figure is the same as in the third embodiment, but the same types of diodes 2F-1 ′, 2F-2 ′, and 2F-3 ′ are used for the first bypass diodes. Connected in parallel. Even if the first bypass diodes are arranged in parallel as in this embodiment, the forward voltage characteristics when the 8A is energized between the terminals 14-17 as the first diode array are substantially the same, so that the operation is performed in the same manner as in the second embodiment. be able to. Actually, it was covered with a black cloth as shown in FIG. 8 (F ′), and the temperature of each diode was measured. As a result, the average of the first bypass diode was about 30 ° C., and the second bypass diode was 50 ° C. The reason why the temperature of the first bypass diode has decreased is considered to be that the energization current has been halved by parallelization.

FIG. 11 is a block diagram for explaining the fifth embodiment.
Eight modules M5-1 to M-8 are connected in series, and a current flows from the terminal 20 toward the terminal 21 during power generation. The circuit of each module is shown in FIG. Except for the arrangement of the second bypass diode described below, the configuration is the same as that shown in FIG. 6 (F ′) of the second embodiment.

  In this embodiment, the second bypass diodes 3F-S-1 and 3F-S-2 made of SiC diodes are serially connected and connected in parallel with two modules interposed therebetween. Based on such a combination, the same arrangement was made using the second bypass diodes 3F-S-4 to 8. That is, this embodiment manages the first diode array included in the two modules collectively, and since one module has three first bypass diodes connected as shown in FIG. In order to design the second bypass diode in accordance with the above (Equation 1), a forward voltage of 3.6 V (= 1.2 V × 3) at a rated current of 8 A of a total of three first bypass diodes for one module. ) Install a second diode with a threshold value less than 7.2V (= 1.2V x 6) in the rated current 8A of a total of six first bypass diodes, which is larger than two modules. There is a need to. For this reason, two SiC PN diodes with a threshold voltage of 2.5 V are serialized (as if 3F-S-1 and 3F-S-2 are connected in series to modules M5-1 and M5-2), respectively. A current bypass circuit having a threshold voltage of 5 V (= 2.5 V × 2) was formed.

  In order to confirm the operation of this embodiment, the entire surface of the modules M5-3 and M5-4 are covered with black cloth as shown in FIG. 13, and the other modules are tested in an environment where rated power generation is possible. Carried out. As a result, it can be confirmed that the second bypass diodes of 3F-S-1 and 3F-S-2, which were connected in parallel to the modules M5-3 and M5-4, are ON and current is commutated. It was. The individual average temperature of the first bypass diodes related to modules M5-3 and M5-4 was about 30 ° C. In order to know the effect of the second bypass diode in this state, 3F-S-1 and 3F-S-2 were removed and the temperature of the first bypass diode was measured. It was confirmed that most of the current was commutated.

  In the above embodiments, the polycrystalline silicon solar cells were used. However, in the present invention, single crystal silicon, amorphous silicon, CIGS, etc., are equivalently regarded as electric resistors when sunlight is cut off. It is applicable to a solar power generation element capable of In addition, as shown in the examples, by using the present invention, from a relatively small configuration that protects individual solar cells with dust attached to the surface, it is possible to change the daily changes to each module due to the shade of the building. The present invention can also be applied to a case where a plurality of single modules become electric resistors in the system, and can provide a highly safe and highly reliable photovoltaic power generation system. Furthermore, the present invention can also be applied to power generation cells other than solar cells, and the same effect can be obtained in the case of power generation cells such as fuel cells and thermoelectric conversion elements.

1, 1C-1, 1F Solar cell 2 First bypass diode 3 Second bypass diode 4, 5, 6 Circuit group 7, 8, 9, 10, 14, 15, 16, 17 Connection terminals 11, 11D, 11F, 11F 'Current path 12, 18, 20 Junction box 13, 19 Power conditioner M1, M2, M3, M4, M5-1-8 Module
2B-A, 2D-A, 2E-A First diode row
3B, 3C, 3D, 3F-1, 3F-2, 3F-S, 3F-S-1 to 8 Second bypass diode
2C, 2F-1, 2F-2, 2F-3 First bypass diode
11C current path
1D-A, 1E-A, 1F-A Solar cell group
IV-1 Current-voltage characteristics of Schottky barrier diodes
IV-2 Current-voltage characteristics of PN junction diodes
IV-3 Current-voltage characteristics of serialized Schottky barrier diodes

Claims (3)

A plurality of power generation circuit units having a power generation cell body composed of one or more power generation cells and a first bypass diode that is connected in parallel to the power generation cell body and can bypass the power supply to the power generation cell body. A power generation cell system circuit in which a current bypass circuit having one or more second bypass diodes is connected in parallel to a first diode row in which two or more first bypass diodes are connected in series in the power generation circuit unit. And
The threshold voltage V _th when the current bypass circuit is energized by rectification when the forward voltage drop in the first bypass diode alone is V _f satisfies the following relational expression (1): System circuit.
V _f × n> V _th > V _f (1)
(Where n represents the number of first bypass diodes forming the first diode row, and n ≧ 2.)   The power generation cell system circuit according to claim 1, wherein the second bypass diode is a bipolar diode made of a wide band gap semiconductor material.   A power generation system comprising a power generation array in which two or more power generation cell system circuits according to claim 1 or 2 are connected in series.

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