JP6144583B2 - Solar power system - Google Patents

Description

  The present invention relates to a photovoltaic power generation system including a power generation device having at least one solar cell module and a power conversion device that inputs an output voltage of the power generation device.

  In recent years, in order to improve the power generation efficiency of solar cells, an electrode is not provided on the front surface which is the light receiving surface, and a P-type current collecting layer (electrode) and an N-type current collecting layer (electrode) are provided on the back surface opposite to the light receiving surface. A back electrode type solar cell has been developed in which both are provided to eliminate the shadow loss due to the electrodes (see, for example, Patent Document 1).

JP 2006-128258 A

  However, when generating power by irradiating a solar cell module including a back electrode type solar cell (hereinafter, also referred to as a back electrode type solar cell module) with sunlight, power generation efficiency may decrease with the passage of power generation time. May happen. As a result of analyzing this phenomenon, the present inventors have found that this phenomenon hardly occurs in a solar cell module including a solar cell in which electrodes are also provided on the light receiving surface side that has been used in the past. The larger the potential difference between the potential of the power generation part of the module and the potential of the part that does not contribute to the power generation of the back electrode type solar cell module such as the module frame, the lower the power generation efficiency, and the back electrode type solar cell module due to rainfall, etc. It has been found that the power generation efficiency tends to decrease when a water film is formed on the light receiving surface.

  From the above analysis results, the present inventors have estimated that the power generation efficiency of the back electrode type solar cell module is reduced by the following mechanism. Here, an example of a schematic cross section of the back electrode type solar cell module is shown in FIG. 4, and the mechanism estimated by the present inventors will be described with reference to FIG. 5 which is a partially enlarged view of FIG.

  The back electrode type solar cell module shown in FIG. 4 is opposite to the N-type silicon substrate 1, the passivation film 2 provided on the surface side which is the light-receiving surface of the N-type silicon substrate 1, and the light-receiving surface of the N-type silicon substrate 1. A plurality of back surface electrode type solar cells 5 each having a P type current collecting layer 3 and an N type current collecting layer 4 provided on the back surface on the side, and further adjacent two adjacent back surface electrode type solar cells 5 A connecting member 6 for connecting the P-type current collecting layer 3 and the N-type current collecting layer 4 is also provided. In the N-type silicon substrate 1, a P + layer 1A is formed so as to be in contact with the P-type current collecting layer 3, and an N + layer 1B is formed so as to be in contact with the N-type current collecting layer 4. In the back electrode type solar cell module shown in FIG. 4, the back electrode type solar cell 5 and the connection member 6 are sealed with a sealing material 7 such as ethylene vinyl acetate resin, and glass or the like is formed on the surface side of the sealing material 7. The translucent substrate 8 is provided, the back surface protection sheet 9 is provided on the back surface side of the sealing material 7, the side surfaces of the sealing material 7, the translucent substrate 8, and the back surface protection sheet 9, and the translucent substrate 8 is provided with an end surface sealing material 10 such as rubber covering the front surface side periphery of 8 and the back surface side periphery of the back surface protection sheet 9, and a conductive module frame 11 such as aluminum is provided outside the end surface sealing material 10. Yes.

(I) The electric field shown in FIG. 5 is sealed by the potential difference between the power generation unit (N-type silicon substrate 1) in the back electrode type solar cell module and the portion (module frame 11) that does not contribute to the power generation of the back electrode type solar cell module. When applied to the material 7, free electrons 12 contained in the sealing material 7 are collected on the light receiving surface side of the passivation film 2.
(Ii) The holes contained in the N-type silicon substrate 1 are attracted to the passivation film 2 side so as to form a pair with the free electrons 12 contained in the sealing material 7 collected on the light receiving surface side of the passivation film 2. The power to take.
(Iii) When light is irradiated into the N-type silicon substrate 1, a pair of electrons 13 and holes 14 is generated by photoexcitation. These can be extracted to the outside as generated power when the electrons 13 reach the N-type current collecting layer 4 and the holes 14 reach the P-type current collecting layer 3 due to the electric field at the pn junction. Due to the force described in ii), the probability that the holes 14 are directed toward the passivation film 2 increases. As shown in FIG. 5, when the substrate of the solar cell is an N-type silicon substrate, the holes 14 become minority carriers, so the rate at which the holes 14 generated by photoexcitation reach the P-type current collecting layer 3 decreases. If this happens, the generated power that can be taken out, that is, the power generation efficiency, will be reduced.

  In view of the above estimation mechanism, the electric field shown in FIG. 5 is not applied to the encapsulant 7 as a measure for preventing a decrease in power generation efficiency of the back electrode type solar cell module that may occur with the lapse of power generation time. Thus, it can be considered that electrons are not accumulated on the passivation film. However, since the potential difference between the power generation unit in the back electrode type solar cell module and the portion that does not contribute to the power generation of the back electrode type solar cell module is determined by the configuration of the entire solar power generation system, the back electrode type solar cell module itself There was a problem that it was difficult to solve.

  An object of this invention is to provide the solar power generation system which can suppress that power generation efficiency falls with progress of power generation time in view of said condition.

  In order to achieve the above object, a photovoltaic power generation system according to the present invention includes a circuit breaker, a power generation device having at least one solar cell module, a positive-side input terminal that inputs a positive-side of an output voltage of the power generation device, and the A power conversion device having a negative side input terminal for inputting a negative side of the output voltage of the power generation device, the positive side input terminal is grounded via the breaker, and when the breaker is in a cut-off state The connection between the positive input terminal and the ground is cut off.

  Further, when a ground fault current detector that detects a ground fault current generated when the negative input terminal has a ground fault, and a ground fault current detected by the ground fault current detector exceeds a first threshold, You may make it provide the control part which makes the said breaker the interruption | blocking state.

  The control unit may stop the operation of the power conversion device when a ground fault current detected by the ground fault current detector exceeds a second threshold value that is smaller than the first threshold value. .

  Further, the control unit may constantly monitor the state of the breaker, and stop the operation of the power converter when the breaker is in a cut-off state.

  The power generation device may include a plurality of the solar cell modules, and the output voltage of the power generation device may be a solar cell module string voltage obtained by serially adding at least two of the output voltages of the solar cell modules.

  The solar cell module has a back electrode type solar cell in which both a P-type current collecting layer and an N-type current collecting layer are provided on the back surface opposite to the light receiving surface of the N-type silicon substrate. Also good.

  Moreover, you may make it the said solar cell module have an electroconductive module frame which covers the edge part of the said solar cell module.

  The module frame may be grounded.

  According to the present invention, since the positive potential of the output voltage of the power generator can be set to the ground potential, it is possible to prevent the power generation unit in the solar cell module from being in a state where the potential is higher than the ground potential. It can suppress that power generation efficiency falls with progress of power generation time. In addition, since a breaker that can cut off the connection between the positive input terminal and the ground is provided, when a ground fault occurs in the negative input terminal, the ground fault is caused by putting the breaker into a cut-off state. The current can be cut off.

It is a figure which shows schematic structure of the solar energy power generation system which concerns on 1st embodiment. It is a figure which shows the electric power generating apparatus which concerns on 2nd embodiment. It is a figure which shows the electric power generating apparatus which concerns on 3rd embodiment. It is a figure which shows an example of the schematic cross section of a back electrode type solar cell module. It is the elements on larger scale of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the photovoltaic power generation system according to the first embodiment includes a power generation device 102 having four solar cell modules 101, a positive-side input terminal that inputs the positive side of the output voltage of the power generation device 102, and power generation. A power converter 103 having a negative input terminal for inputting a negative input side of the output voltage of the apparatus 102 and a DC ground fault detector 104, and a positive input of the power converter 103 when the breaker 105 is in a cut-off state. The connection between the terminal and the ground is cut off.

  Each connection between the solar cell module 101 and the solar cell module 101 and between the solar cell module 101 and the power converter 103 is performed using, for example, a cable.

  The four solar cell modules 101 in the power generation device 102 are connected in series, and the solar cell module string voltage obtained by adding the output voltages of the four solar cell modules 101 in series becomes the output voltage of the power generation device 102.

  As the solar cell module 101, for example, a back electrode type solar cell module shown in FIG. 4 is used, and the module frame 11 is grounded for safety. The structure of the back electrode type solar cell module is not limited to the structure shown in FIG. 4. For example, a passivation film may be provided on the back surface of the N-type silicon substrate 1. Further, in the back electrode type solar cell module, a P-type silicon substrate can be used instead of the N-type silicon substrate.

  Further, the solar cell module 101 is not limited to the illustrated back electrode type solar cell module. If the potential of the power generation unit in the solar cell module is higher than the potential of the portion that does not contribute to power generation, power generation occurs with the passage of power generation time. Any type of solar cell module that may reduce efficiency may be used.

  The power conversion device 103 may be a power conversion device that outputs a DC / AC converted voltage between a positive input terminal and a negative input terminal that is a DC voltage, and is a positive input terminal that is a DC voltage—a negative input side. A power conversion device that performs DC / DC conversion and outputs the voltage between the input terminals may be used. In addition, the power conversion device 103 has a maximum output operating point tracking (MPPT) function, and performs MPPT control so that the power supplied between the positive input terminal and the negative input terminal is maximized. It is preferable that the operation voltage and the operation current of each solar cell module 101 are determined. When at least one of the ground fault detection signal and the interruption detection signal is supplied from the DC ground fault detector 104, the power conversion device 103 stops the power conversion operation.

  In addition to the breaker 105 described above, the DC ground fault detector 104 is a DC ground fault detection in which a ground fault current detection current detector (for example, a current detector using a Hall element) 106, a control circuit, and the like are mounted. A circuit board 107, a trip coil 108, a trip coil drive circuit 109 that generates a trip coil drive voltage from a voltage of AC 200 [V] that is an output voltage of the AC power supply 111, and a relay 110 are provided.

  The DC ground fault detector 104 may be provided outside the power conversion device 103 as shown in FIG. 1, but since it is small in size and can be easily incorporated inside the power conversion device 103, the power conversion device 103. It is preferable to incorporate it in the inside. In the present embodiment, the ground fault current detection current detector 106 corresponds to the “ground fault current detector” recited in the claims, and includes a DC ground fault detector circuit board 107, a trip coil 108, a trip coil. The drive circuit 109 and the relay 110 correspond to a “control unit” recited in the claims.

  When the breaker 105 is not in the cut-off state, the positive input terminal of the power converter 103 is grounded, and the positive potential of the output voltage of the power generator 102 becomes the ground potential, so that the power generation unit in the solar cell module 101 is generating power. It is possible to prevent the potential from being higher than the ground potential, and it is possible to suppress a decrease in power generation efficiency as the power generation time elapses.

  If a ground fault occurs at the negative input terminal of the power conversion device 103 while the power generation device 102 is generating power, if the breaker 105 remains closed, the negative electrode to the negative electrode of the power generation device 102 through the ground line A ground fault current flows in

  Therefore, in the photovoltaic power generation system according to the first embodiment, the ground fault current detection current detector 106 detects the ground fault current, and the ground fault current detected by the ground fault current detection current detector 106 is the first. When the threshold value of 1 (for example, 5 [A]) is exceeded, the control circuit mounted on the DC ground fault detector circuit board 107 causes the trip coil 108 to be energized and causes the breaker 105 to trip (cut off). Thereby, the ground fault current exceeding the first threshold can be cut off. On the other hand, if the ground fault current detected by the ground fault current detection current detector 106 is equal to or less than the first threshold, the control circuit mounted on the DC ground fault detector circuit board 107 turns off the trip coil 108. Turn on the power. Here, the trip coil 108 being energized means that the trip coil drive voltage output from the trip coil drive circuit 109 is applied to the trip coil 108, and the trip coil 108 is not energized. That is, the trip coil driving voltage output from the trip coil driving circuit 109 is not applied to the trip coil 108.

  In addition, the control circuit mounted on the DC ground fault detector circuit board 107 has a second threshold (for example, 1 [ If A]) is exceeded, a ground fault detection signal is output to the power converter 103, and the power conversion operation of the power converter 103 is stopped.

  Relay 110 trips (opens) when trip coil 108 is energized. Further, the breaker 105 can be manually turned off, but when the breaker 105 is manually turned off, the relay 110 is opened in conjunction. Therefore, when the breaker 105 is in a cut-off state, the relay 110 is in an open state, and when the breaker 105 is in a non-cut-off state, the relay 110 is in a closed state. The control circuit mounted on the DC ground fault detector circuit board 107 constantly monitors the state of the breaker 105 by constantly monitoring the state of the relay 110. The control circuit mounted on the DC ground fault detector circuit board 107 outputs a cutoff detection signal to the power converter 103 when the breaker 105 is in the cutoff state, and the power conversion operation of the power converter 103 is performed. Stop. Thereby, it is possible to prevent the system from being operated in a state where the positive input terminal of the power conversion device 103 is not grounded.

  In addition, a notification means (for example, a lamp or a buzzer) for notifying that a ground fault has been detected using the ground fault detection signal described above, or that the breaker 105 is in a cutoff state using the cutoff detection signal described above. You may provide the alerting | reporting means (for example, a lamp | ramp, a buzzer, etc.) to alert | report. By providing such notification means, the system administrator can easily grasp that an abnormality has occurred in the positive electrode grounding of the system.

  Instead of the configuration of the power generation apparatus 102 shown in FIG. 1, a configuration in which a plurality of solar cell module strings in which a plurality of solar cell modules 101 are connected in series as shown in FIG. Good. Moreover, it may replace with the structure of the electric power generating apparatus 102 shown in FIG. 1, and you may make it the structure which has only one solar cell module 101 as shown in FIG. 3 as 3rd embodiment.

  However, in the configuration in which the power generation apparatus 102 has a solar cell module string in which a plurality of solar cell modules 101 are connected in series, when the potential of the module frame 11 is set to the ground potential, the solar cell located on the upper side of the paper in FIG. 1 or FIG. Since the power generation unit in the module 101 is in a higher potential than the power generation unit in the solar cell module 101 located on the lower side of the page, the breaker 105 and the like are installed so that the power generation efficiency decreases as the power generation time elapses. Otherwise, the power generation efficiency may be greatly reduced. Therefore, the configuration in which the power generation device 102 has a solar cell module string in which a plurality of solar cell modules 101 are connected in series (first embodiment, second embodiment) has the power generation device 102 connected in series with a plurality of solar cell modules 101. The effect is more conspicuous than the configuration without the connected solar cell module string (third embodiment).

DESCRIPTION OF SYMBOLS 1 N type silicon substrate 1A P + layer 1B N + layer 2 Passivation film 3 P type current collection layer 4 N type current collection layer 5 Back surface electrode type solar cell 6 Connection member 7 Sealing material 8 Translucent substrate 9 Back surface protection sheet 10 End face sealing material 11 Module frame 12 Free electron 13 Electron generated by photoexcitation 14 Hole generated by photoexcitation 101 Solar cell module 102 Power generation device 103 Power conversion device 104 DC ground fault detector 105 Breaker 106 Current detection for ground fault current detection 107 DC ground fault detector circuit board 108 Trip coil 109 Trip coil drive circuit 110 Relay 111 AC power supply

Claims (7)

With a breaker,
A power generation device having at least one solar cell module;
A power converter having a positive input terminal for inputting a positive polarity side of the output voltage of the power generator and a negative input terminal for inputting a negative polarity side of the output voltage of the power generator ;
A ground fault current detector for detecting a ground fault current that occurs when the negative input terminal has a ground fault;
When the ground fault current detected by the ground fault current detector exceeds a first threshold, a control unit that turns off the breaker ,
The positive input terminal is grounded via the breaker, and the connection between the positive input terminal and the ground is interrupted when the breaker is in an interrupted state ,
The said control part stops operation | movement of the said power converter device, when the ground fault current detected by the said ground fault current detector exceeds the 2nd threshold value smaller than a 1st threshold value, The sunlight characterized by the above-mentioned. Power generation system. With a breaker,
A power generation device having at least one solar cell module;
A power converter having a positive input terminal for inputting a positive polarity side of the output voltage of the power generator and a negative input terminal for inputting a negative polarity side of the output voltage of the power generator;
A ground fault current detector for detecting a ground fault current that occurs when the negative input terminal has a ground fault;
When the ground fault current detected by the ground fault current detector exceeds a first threshold, a control unit that turns off the breaker,
The positive input terminal is grounded via the breaker, and the connection between the positive input terminal and the ground is interrupted when the breaker is in an interrupted state,
The said control part always monitors the state of the said breaker, and stops the operation | movement of the said power converter device when the said breaker is a interruption | blocking state, The solar power generation system characterized by the above-mentioned.   The said control part stops operation | movement of the said power converter device, when the ground fault current detected by the said ground fault current detector exceeds the 2nd threshold value smaller than a 1st threshold value. 2. The solar power generation system according to 2. The power generator comprises a plurality of the solar cell modules,
The photovoltaic power generation according to any one of claims 1 to 3, wherein the output voltage of the power generation device is a solar cell module string voltage obtained by serially adding at least two of the output voltages of the solar cell modules. system. The solar cell module has a back electrode type solar cell in which both a P-type current collecting layer and an N-type current collecting layer are provided on the back surface opposite to the light receiving surface of the N-type silicon substrate. The solar power generation system of any one of Claims 1-4. 6. The solar power generation system according to claim 5, wherein the solar cell module has a conductive module frame that covers an edge of the solar cell module. The solar power generation system according to claim 6, wherein the module frame is grounded.