JP2007059423A - Photovoltaic power generation controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance power generation efficiency of a photovoltaic power generation system while preventing deterioration of a solar cell in the early stage. <P>SOLUTION: When a sensor section 6 detects a fact that a potential difference across the switching portion 3 of a string 1 comprising a cluster group 2 constituting a solar cell array reversed the polarity, a control section 8 controls the switching portion 3 to interrupt a line 4. When the potential difference across each cluster 2 exceeds a predetermined threshold, a control section 16 controls a switching portion 12 to interrupt lines 11A and 11B, and controls the switching portion 12 to conduct the lines 11A and 11B when the potential difference is lower than that threshold. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photovoltaic power generation control device for suppressing loss and deterioration in a photovoltaic power generation system.

  As shown in FIG. 4, a conventional general photovoltaic power generation system includes a solar cell array (solar cell panel) A1 and a power conditioner A2 that convert sunlight energy into electric energy. The output of the array A1 is adjusted via the power conditioner A2 and supplied to the load A3.

Further, the load A3 can be supplied with electric power from the commercial power source A4 side when the required amount of power generation cannot be obtained from the solar cell array A1, such as during cloudy weather or at night.
The solar cell array A1 is configured, for example, by connecting strings (series connection) of a plurality of solar cell modules A5 in parallel via backflow prevention diodes A6 as shown in FIG.

  Further, each solar cell module A5 is configured by connecting a plurality of clusters A8 (two clusters in the case of FIG. 6) in series, each consisting of a plurality of cells A7 connected in series as shown in FIG. Yes. Further, bypass diodes A9 are connected in parallel to both ends of each cluster.

Here, when grasping the constituent elements of the solar cell array in units of clusters, the conventional solar cell array is configured such that a plurality of strings each composed of a plurality of cluster groups are connected in parallel via a backflow prevention diode, It can be considered that the bypass diodes are connected in parallel at both ends of each cluster. (For example, see Patent Document 1)
JP-A-5-343724

  In the solar cell array having such a series-parallel structure of a large number of clusters, when some clusters enter the shade, no electromotive force is generated in the shaded cluster, but a bypass diode is provided. As a result, the current flows through the bypass diode before and after the shaded cluster, thereby preventing the loss due to the internal resistance of the cluster and affecting the entire solar cell array due to the partially shaded part of the cluster. It tries to avoid the output drop.

  Further, a backflow prevention diode incorporated in each of the strings formed of the cluster group prevents the current from flowing back from the other strings to the string where the electromotive force is reduced, thereby preventing output loss.

  However, in the conventional photovoltaic power generation system as described above, since the bypass diodes used themselves have losses, when there are many shaded clusters, the total loss due to these bypass diodes There was a problem that would increase.

  Also, in the backflow prevention diode, a loss occurs in the same manner as the bypass diode. However, in the conventional photovoltaic power generation system, attention is paid only to the output decrease due to the shade. Since the output loss generated in this part was not considered in the design, it was difficult to increase the power generation efficiency.

  FIG. 7 shows a current-voltage characteristic for one string in a conventional photovoltaic power generation system, and a curve a in the figure shows a current-voltage characteristic when there is no backflow prevention diode. On the other hand, when a backflow prevention diode is incorporated, the current-voltage characteristic is as shown by the curve b in FIG. 5, and output loss is generated by the area indicated by hatching.

  On the other hand, FIG. 8 shows the current-voltage characteristics of the entire solar cell array in the conventional photovoltaic power generation system, and the curve a in the figure has no shaded part and no bypass diode is incorporated. The current-voltage characteristic is shown.

  On the other hand, when there is a shaded part and a bypass diode is incorporated, the current-voltage characteristics are as shown by curve b in the figure, and the output loss is shaded as shown by different types of hatching. This is the sum of the loss due to and the loss due to the bypass diode.

  In addition, the characteristic of the diode is that current starts to flow suddenly when the applied voltage (forward voltage) exceeds a predetermined threshold, and at a voltage below this threshold, current hardly flows and has a high resistance value. When some clusters of solar cell modules are in the shade, the current is limited by the cells that make up the cluster, and the line is bypassed via a bypass diode to avoid current limitation due to the shaded clusters. Current will flow through.

  However, until the forward voltage applied to the bypass diode exceeds the threshold value, current flows through the cluster that is not shaded and does not generate power, so the solar cells in this cluster generate a heat generation phenomenon (hot spot phenomenon). As a result, there is a problem in that heat loss occurs and cells constituting the cluster deteriorate early.

  Therefore, the present invention solves the problems caused by using the bypass diode and the backflow prevention diode in the conventional solar power generation system as described above, and can improve the power generation efficiency of the solar power generation system. An object of the present invention is to provide a solar power generation control device that can prevent early deterioration of solar cells.

  The first photovoltaic power generation control device of the present invention provided for the above purpose is inserted in the middle of a line that bypasses both ends of a cluster composed of single or multiple solar cells connected in series. A switching unit, a sensor unit for detecting a potential difference between both ends of the cluster, and a potential difference detected by the sensor unit exceeding a predetermined threshold, the switching unit is configured to interrupt the line, and the potential difference When the value is less than or equal to the threshold value, the switching unit includes a control unit that conducts the line.

  In addition, the second photovoltaic power generation control device of the present invention is inserted in the middle of a line connected in series with one end of a string composed of clusters of single or multiple solar cells connected in series. A switching unit, a sensor unit that detects a potential difference between both sides of the switching unit of the line, and the line that is blocked by the switching unit when the polarity of the potential difference detected by the sensor unit is opposite to the normal polarity. And a control unit to be operated.

  Furthermore, the third one of the photovoltaic power generation control devices of the present invention is in the middle of the first line connected in series with one end of the string composed of clusters composed of single or plural solar cells connected in series. A first switching unit interposed between the first switching unit, a first sensor unit that detects a potential difference between both sides of the first switching unit of the first line, and a polarity of the potential difference detected by the first sensor unit A first control unit that causes the first switching unit to cut off the first line when the polarity is opposite to normal, and a second line that bypasses both ends of each cluster constituting the string. A second switching unit inserted in the middle of the second switching unit, a second sensor unit for detecting a potential difference between both sides of the second switching unit of these second lines, and the second sensor unit. When the detected potential difference of the second line exceeds a predetermined threshold value, the second switching unit blocks the line, and when the potential difference is equal to or less than the threshold value, the second switching unit And a second control unit for conducting the line.

  Here, the term “cluster” is used to mean a structural unit of a power generation element composed of a single cell or a string (series connection) of a plurality of cells (solar power generation elements). Therefore, the term “solar cell module” that is generally used is a plurality of clusters connected in series.

  According to the photovoltaic power generation control device according to the first aspect of the present invention, it is possible to avoid the loss of generated power caused by the bypass diode used in the conventional photovoltaic power generation system, and to increase the power generation efficiency. . Moreover, since the problem of deterioration due to heat generation of the shaded solar battery cell as in the case of using the bypass diode does not occur, the performance of the photovoltaic power generation system can be maintained for a long time.

  Moreover, according to the photovoltaic power generation control apparatus according to the second aspect of the present invention, it is possible to avoid loss of generated power caused by the backflow prevention diode used in the conventional photovoltaic power generation system.

  Moreover, according to the photovoltaic power generation control apparatus of the invention of claim 3, since no diode that has been one of the causes of lowering the power generation efficiency of the conventional photovoltaic power generation system is used, loss of generated power Can be reduced as much as possible, and the performance of the photovoltaic power generation system can be maintained over a long period of time.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows one string in a solar cell module provided with the photovoltaic power generation control device of the present invention. The string 1 is composed of a group of a plurality of clusters 2 connected in series with each other. Although not shown in the figure, these clusters 2 are further composed of single or multiple solar cells connected in series.

  One end of the string 1 is connected in series with a line 4 having a switching unit 3 formed in the middle of the MOSFET (Metal Oxide Semiconductor Field Effect Transistor). A sensor unit 6 for detecting a potential difference on both sides of the switching unit 3 is connected in parallel to the line 4 via bypass lines 5A and 5B. The potential difference detected by the sensor unit 6 Via the control unit 8.

  In the present embodiment, the control unit 8 is configured by a microcomputer, and monitors potential difference data sent from the sensor unit 6 via the signal line 7 at predetermined time intervals, and the polarity of the potential difference is monitored. In a normal case, the switching unit 3 is ON, and the line 4 is in a conductive state.

  On the other hand, when the control unit 8 determines that the potential difference detected by the sensor unit 6 has a reverse polarity, the control unit 8 sends a control signal for turning OFF to the switching unit 3 via the signal line 9. As a result, the conduction of the line 4 is cut off.

  Here, the switching unit 3, the line 4, the bypass lines 5 </ b> A and 5 </ b> B, the sensor unit 6, the signal line 7, the control unit 8, and the signal line 9 constitute a first photovoltaic power generation control device 10. This solar power generation control device 10 serves as a backflow prevention diode incorporated in each string in a conventional solar power generation system.

  FIG. 2 is a diagram showing a flow of processing executed by the solar power generation control device 10, and when the solar power generation control device 10 is activated, the control unit 8 turns off the switching unit 3 (steps). S1).

  In this state, the sensor unit 6 detects a potential difference ΔV1 between both ends of the switching unit 3 (step S2). Next, the control unit 8 determines whether or not the potential difference ΔV1 is a negative value (reverse polarity) (step S3).

  As a result, when the control unit 8 determines that ΔV1 is not a negative value, that is, positive polarity, the control unit 8 switches the switching unit 4 to ON and makes the line 4 conductive (step S4). Thereafter, the control unit 8 determines whether or not a predetermined time has elapsed (step S5). When the predetermined time has elapsed, the control unit 8 switches the switching unit 4 to OFF again (step S1), and thereafter repeats the operations after step S2. .

  Here, the reason why the switching unit 4 is turned OFF after the predetermined time has elapsed is to detect whether or not the potential difference between both ends of the switching unit 3 has subsequently changed to a negative value by the sensor unit 6.

  On the other hand, when the control unit 8 determines that ΔV1 has a negative value, that is, a reverse polarity in step S3, the control unit 8 repeats step S2 and subsequent steps from the state where the switching unit 3 in step S1 is OFF.

  Further, bypass lines 11A and 11B are connected to both ends of each cluster 2, and a switching unit 12 is interposed between the bypass lines 11A and 11B.

  A sensor unit 13 for detecting a potential difference between both ends of the cluster 2 is provided between the bypass lines 11A and 11B in parallel with the switching unit 12. In the present embodiment, the switching unit 12 is configured by a MOSFET or the like, similar to the switching unit 3 described above.

  Further, the switching unit 12 and the sensor unit 13 connected to each cluster 2 are connected to the control unit 16 via the signal line 14 and the signal line 15. In the present embodiment, the control unit 16 is configured by a microcomputer similarly to the control unit 8 described above, and potential difference information between both ends of the cluster 2 output from the sensor unit 13 is transmitted via the signal line 14 to the control unit. 16 is sent.

  The control unit 16 monitors the potential difference information sent from the sensor unit 13 at predetermined time intervals, and when the potential difference between both ends of the cluster 2 exceeds a predetermined threshold, the switching unit 12 is turned off. The bypass line 3 is blocked.

  Then, when the cluster 2 decreases in power generation output due to shade or the like, and the potential difference decreases below the threshold value, the control unit 16 sends a command signal to turn on to the switching unit 12 via the signal line 15, Conduction is established between the bypass lines 11A and 11B.

  Here, the second solar power generation control device 17 is configured by the bypass lines 11A and 11B, the switching unit 12, the sensor unit 13, the signal lines 14 and 15, and the control unit 16 attached to each cluster 2.

  Next, FIG. 3 is a diagram illustrating a processing flow executed by the second photovoltaic power generation control device 17 described above. When the photovoltaic power generation control device 17 is activated, the control unit 16 is switched to a switching unit. 12 is turned OFF (step S1).

  In this state, the sensor unit 13 detects a potential difference ΔV2 between both ends of the switching unit 3 (step S2). Next, the control unit 16 determines whether or not the potential difference ΔV2 exceeds a predetermined potential difference ΔV0 (threshold value) (step S3).

  When the control unit 16 determines that the potential difference ΔV2 exceeds ΔV0, step S1 and subsequent steps are repeated again. On the other hand, when the potential difference ΔV2 becomes equal to or less than V0, the control unit 16 turns on the switching unit 12 to conduct between the bypass lines 11A and 11B (step S4).

  Thereafter, the control unit 16 determines whether or not a predetermined time has elapsed (step S5). When the predetermined time has elapsed, the control unit 16 switches the switching unit 12 to OFF again (step S1), and thereafter repeats the operations after step S2. .

  The reason why the switching unit 12 is turned off after a predetermined time has elapsed in step S <b> 1 is that the sensor unit 13 detects a potential difference between both ends of the switching unit 12.

  In the embodiment described above, the switching unit 3 and the switching unit 12 are provided with both the first photovoltaic power generation control device 10 and the second photovoltaic power generation control device 17 for each string 1, and such In the embodiment, since no diode is used, a decrease in power generation efficiency due to the diode can be completely avoided.

  However, although the effect is somewhat reduced, instead of incorporating only the first photovoltaic power generation control device 10 and incorporating the second photovoltaic power generation control device 17, each cluster 2 is provided with a bypass diode as in the past. It is good also as a form connected in parallel.

  In addition, a second photovoltaic power generation control device 17 is incorporated for each cluster 2, and a backflow prevention diode is connected in series to the string 1 consisting of the group of clusters 2 without incorporating the first photovoltaic power generation control device 10. It is good also as a connected form.

  In the present embodiment, the switching unit 3 and the switching unit 12 both use MOSFETs, but can be configured using other switching elements such as relays.

  The solar power generation control device of the present invention can be used for improving power generation efficiency by being incorporated in a solar cell array installed on the roof of a building or the like.

It is a schematic block diagram of the solar power generation control device as one embodiment of the present invention. It is a figure which shows the processing flow which the 1st photovoltaic power generation control apparatus in one Embodiment of this invention performs. It is a figure which shows the processing flow which the 2nd photovoltaic power generation control apparatus in one Embodiment of this invention performs. It is a schematic block diagram of the conventional common photovoltaic power generation system. It is a schematic block diagram of the solar cell array in the conventional solar power generation system. It is a schematic block diagram inside the solar cell module shown in FIG. It is a figure which shows the current-voltage characteristic regarding one string in the conventional photovoltaic power generation system. It is a figure which shows the current voltage characteristic of the whole solar cell array in the conventional solar power generation system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 String 2 Cluster 3 Switching part 4 Line 5A, 5B Bypass line 6 Sensor part 7 Signal line 8 Control part 9 Signal line 10 (1st) Photovoltaic power generation control apparatus 11A, 11B Bypass line 12 Switching part 13 Sensor part 14, 15 signal line 16 control unit 17 (second) photovoltaic power generation control device

Claims (3)

A switching unit inserted in the middle of a line that bypasses both ends of a cluster composed of single or multiple solar cells connected in series;
A sensor unit for detecting a potential difference between both ends of the cluster;
When the potential difference detected by the sensor unit exceeds a predetermined threshold value, the control unit causes the switching unit to block the line, and when the potential difference is equal to or less than the threshold value, the control unit causes the switching unit to conduct the line. And a photovoltaic power generation control device. A switching unit inserted in the middle of a line connected in series with one end of a string composed of clusters of single or multiple solar cells connected in series;
A sensor unit for detecting a potential difference on both sides of the switching unit of the line;
A photovoltaic power generation control apparatus comprising: a control unit that causes the switching unit to block the line when a polarity of a potential difference detected by the sensor unit is opposite to a normal polarity. A first switching unit interposed in the middle of a first line connected in series with one end of a string formed of clusters of single or multiple solar cells connected in series;
A first sensor unit for detecting a potential difference on both sides of the first switching unit of the first line;
A first control unit that causes the first switching unit to shut off the first line when the polarity of the potential difference detected by the first sensor unit is opposite to a normal polarity;
A second switching unit interposed in the middle of a second line that bypasses both ends of each cluster constituting the string;
A second sensor unit for detecting a potential difference between both sides of the second switching unit of the second line;
When the potential difference of the second line detected by the second sensor unit exceeds a predetermined threshold value, the second switching unit blocks the line, and when the potential difference is equal to or less than the threshold value, A solar power generation control device comprising: a second control unit that causes the second switching unit to conduct the line.

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