JP2002026356A - Snow melting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To melt snow by a solar cell system which has a smaller number of parts and a small-sized and inexpensive structure, and with small power consumption. SOLUTION: This snow melting device is provided with a solar cell 1B in which a plurality of modules 2 is arranged in a matrix and the modules 2 in the respective horizontal rows are serially connected per horizontal row to form strings 3a to 3x in the respective steps, and a power supply means for snow melting which supplies a d.c. reverse voltage only to the string 3x on the lowermost step when the solar cell 1B operates for snow melting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a solar cell in which a plurality of modules in each row are connected in series for each row to form a string in each stage. Snow melting equipment.

[0002]

2. Description of the Related Art Conventionally, a photovoltaic power generation device as a power facility usually operates a power conversion device such as an inverter in a system interconnected manner, and by this interconnection operation, direct current generation of a solar cell installed on a roof or the like is performed. The output is converted back to alternating current and fed to the grid.

[0003] Incidentally, a solar cell for electric power used in this power generation device is formed as shown in FIG.

That is, this type of solar cell _1A is formed by arranging a plurality of modules (solar cell modules) 2 in a matrix, and the modules 2 in each row are indicated by arrows in the drawing. .., 3x of each stage.

Furthermore, the solar power generator using the solar cell 1 _A is formed as shown in FIG. 6, the string 3
The output powers a to 3x are combined in parallel via respective backflow prevention diodes (blocking diodes) 4a, 4b,..., 4x, and supplied to a power converter 5 composed of a bidirectional converter or the like.

[0006] Normally, the power converter 5 is connected to the system power supply AC and operates as an inverter under the connection operation control of the control device 6 to operate as an inverter, and reversely convert each power generation output into an AC having a system frequency. Output to the grid side.

Next, when this type of photovoltaic power generator is used in an area where there is a lot of snowfall (snowfall), removal of snowfall on the surface of the solar cell is one of the important issues.

Then, each string 3a of the solar cell _1A
When a reverse voltage of DC is applied by supplying DC power to the strings 3a to 3x, each of the strings 3a to 3x operates as a heating element, and the snow can be removed by melting the snow due to the generated heat. Therefore, conventionally, as shown in FIG. , 7x in parallel with each of the diodes 4a to 4x, and including normally open snow melting switchgears 7a, 7b,... A series connection circuit is connected as the snow melting power supply paths 9a, 9b,..., 9x of each stage to form a snow melting device.

In this snow melting apparatus, when the control device 6 shifts to snow melting control by automatic or manual switching based on detection of snow cover, the power conversion device 5 is switched to a forward conversion device of system alternating current, and the power conversion device 5 Side is supplied with DC power for melting snow.

At this time, the control devices 6 close the switchgears 7a to 7x of the respective snow melting power supply paths 9a to 9x, and the DC power for the snow melting of the power converter 5 is supplied through the respective snow melting power supply paths 9a to 9x. The strings 3a to 3x of each stage are fed in parallel,
The strings 3a to 3x in each stage operate as heating elements by applying a DC reverse voltage, and the solar cells 1
Snow melting on the surface of _A is performed.

When the power output of the solar cell _1A recovers due to the snow melting, the terminal voltage of the solar cell _1A increases.
The control device 6 shifts from the constant voltage control of the DC power for snow melting to the constant current control, thereafter ends the snow melting operation control, and returns to the normal interconnection operation control again.

[0012]

For [0007] Conventional apparatus of FIG. 6, the opening and closing device for each row of stages of the solar cell 1 _A 7a~7x
It is necessary to provide the snow melting power supply paths 9a to 9x having the following. In addition, in order to equalize the current sharing among the strings 3a to 3x, it is necessary to provide the shunt resistors 6 in the respective snow melting power supply paths 9a to 9x.

[0013] Therefore, there is a problem that the number of parts is increased and miniaturization and cost reduction cannot be achieved.
Since DC power is supplied to all of the strings 3a to 3x, there is also a problem that power consumption during snow melting is large.

It is an object of the present invention to efficiently melt snow in a solar cell of this type of photovoltaic power generator with a small number of parts and a small and inexpensive configuration with low power consumption.

[0015]

In order to solve the above-mentioned problems, a snow melting apparatus according to the present invention comprises a plurality of solar cell modules arranged in a matrix, and each row of modules is connected in series for each row. A solar cell having a string of each stage, and a snow melting power supply unit for applying a DC reverse voltage only to the lowermost string during a snow melting operation of the solar cell.

Since the solar cell is installed on the roof or the like so as to be inclined so as to sufficiently receive the solar radiation, if a direct current reverse voltage is applied only to the lowermost string by the snow melting power supply means during the snow melting operation. The heat generated by the string melts the snow at the bottom of the solar cell, and the snow on the surface of the solar cell falls along the entire surface due to the melting of the snow. The snow melts.

In this case, it is sufficient to form and provide only the snow melting power supply path of the lowermost string by the snow melting power supply means, and this snow melting power supply path is connected to the string of another stage such as the shunt resistance of the conventional device. There is no need to provide a means for balancing current, and the number of components is small, and the device is small and inexpensive.

Further, since a DC reverse voltage needs to be applied only to the lowermost string, power consumption required for snow melting is reduced as compared with a case where a DC reverse voltage is applied to all strings.

Therefore, with a small and inexpensive configuration having fewer components than the conventional device, snow melting of the solar cell can be performed with low power consumption.

Then, the snow melting power supply means, when the snow melting operation,
A power conversion device that switches from reverse conversion of converting the output of the solar cell to AC to forward conversion of converting AC on the system side to DC,
It is practically and preferably provided that a normally open switching device is provided between the lowermost string of the solar cell and the power conversion device and is closed or opened only during the snow melting operation.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
This will be described with reference to FIGS. In these drawings, the same reference numerals as those in FIGS. 5 and 6 indicate the same or corresponding components. (First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. Figure 1 shows the overall structure of a photovoltaic device, a solar cell 1 _B is formed by arranging a plurality of modules 2 in a matrix as shown in FIG. 2, as in the conventional battery 1 _A in FIG. 5 Roof And a plurality of strings 3a to 3x arranged in rows from the uppermost row to the lowermost row.

Next, in the present invention as shown in the arrows of FIG. 2 during snow melting operation, the heating element is energized only the lowermost string 3x solar cell 1 _B.

Also, in this embodiment, during the snow melting operation,
A direct current reverse voltage for snow melting is applied from the power converter 5 to the string 3x. This reverse voltage is a voltage having a polarity such that the positive terminal and the negative terminal of the string 3x are positive and negative.

Therefore, as shown in FIG.
x only in parallel with the diode 4x, the switchgear 7a of FIG.
7x, a normally-open switchgear 10 is provided, and the switchgear 10 forms a snow melting power supply path 11.

During the snow melting operation, the power converter 5 is automatically or manually switched by the control unit 6 based on the detection of snow cover, and the power converter 5 is switched from the inverter for converting the power output of the solar cell 1 by the grid connection operation to the system conversion. It switched to forward conversion device, and outputs the DC power for snow melting on the solar cell 1 _B side.

Further, the switching device 10 is changed from the open state to the closed state or the open / closed state by the control device 6, and the DC power for snow melting of the power converter 5 is supplied via the switch device 10 to the lowermost stage of the solar cell 1. The string 3x is supplied only to the string 3x, and the string 3x generates heat by a reverse voltage of direct current.

[0027] snow of the lowermost surface of the solar cell 1 _B This heating is snow melting, dropped across snow of the solar cell 1 _B surface along its surface, snow that has moved to the lowest stage string 3x Snow is melted by the fever.

Then, due to the melting of the snow due to the heat generated by the strings 3x and the fall of the snow on the upper stage, the snow on the entire surface of the solar cell is generated by heating only the lowermost string 3x.

In this case, the other strings 3a, 3b,.
Since no DC voltage is applied at the time of snow melting, there is no need to provide a snow melting power supply path, and the current dividing resistors 8a to 8x of FIG. There is no need to provide such a resistor or the like.

Therefore, only for the lowermost string 3x, it is sufficient to provide the snow melting power supply path 11 of the switchgear 10 between the string 3x and the power converter 5, and the number of parts is small, and the configuration is simple and small. it can be carried out effectively snow melting of the solar cell 1 _B in power consumption.

The switching device 10 may be kept closed during the snow melting operation. However, when the switching device 10 is opened and closed (switched), the DC voltage and current supplied to the string 3x can be controlled, and the snow melting operation can be performed with high accuracy. DC power can be supplied.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a case where the voltage of the power output of the solar cell 1 _B is lower than the input voltage of the power converter 5, and a booster chopper circuit 12 is provided in a stage preceding the power converter 5.

On the input side of the chopper circuit 12, a series circuit of a chopper input capacitor 13 and a DC reactor 14 is provided.
A parallel circuit of a freewheel diode 16 is connected, and a capacitor 19 on the output side of the chopper circuit 12 is connected to the parallel circuit via a parallel circuit of a semiconductor switch 17 and a freewheel diode 18. The input side of the converter 5 is connected.

Under the control of a control device (not shown) similar to the control device 6 of FIG. 1, the semiconductor switch 17 is normally kept off (open) and the semiconductor switch 15 is switched (open / closed). Capacitor 19 is solar cell 1
Is charged to a DC voltage obtained by boosting the power generation output of the battery.

The charging energy of the capacitor 19 is supplied to the power converter 2 during the interconnection operation, converted into an AC synchronized with the system power supply 7, and supplied to the system side.

Next, during the snow melting operation, the opening and closing device 10 is closed by the control device and the semiconductor switch 15 is opened.
High-speed switching with KHZ.

Then, the DC power for snow melting generated by the forward conversion of the power converter 2 is controlled to a desired voltage by the high-speed switching of the semiconductor switch 17, and passes through the snow melting power supply line 11, and the string 3 x of the solar cell 1 _B. , And a reverse voltage of direct current is applied to the string 3x to perform the same snow melting as in the first embodiment.
The same effect as in the case of the embodiment can be obtained.

When the semiconductor switch 17 is on, a current flows through the loop of the capacitor 19, the switch 17, the reactor 14, the switching device 10, the string 3x, and the capacitor 19, and when the semiconductor switch 17 is off, the reactor 14, the switching Device 10, string 3x, diode 1
5, a current flows through the loop of the reactor 14.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. In the case of FIG. 4, it is applied to a photovoltaic device having a structure for boosting in an insulated state with the transformer power output of the solar cell 1 _B.

[0040] In this case, the power generation output of the solar cell 1 _B are accumulated is supplied to the common input capacitor 20 via the diode 4A～4x, DC energy semiconductor switch 21a of the capacitor 20, 21b, 21c, and 21d The high frequency power is converted into high frequency power by a high frequency inverter 21 having a bridge connection configuration.

Further, the high-frequency power is supplied to the diodes 23a, 23a via the high-frequency transformer 22 for insulation and boosting.
b, 23c and 23d are supplied to a full-wave rectification type rectification circuit 23, and a rectified output of the rectification circuit 23 is supplied to the smoothing reactor 2
4, an output-stage inverter 2 which is smoothed by the smoothing capacitor 25 and corresponds to the power converter 2 of the first or second embodiment.
6.

By the system interconnection operation of the inverter 26, the semiconductor switches 27a to 27f of the main circuit 27 of, for example, a three-phase bridge circuit of the inverter 26 are switched, and a three-phase AC synchronized with the system power supply 6 is supplied to the system. Output to the side.

Next, in the case of this power generation device, the opening / closing device 10 of the snow melting power supply line 11 of the string 3x is
It is provided between the positive terminal of x and the positive terminal of the rectifier circuit 23.

[0044] The inverter 26 is an inverter unit with a so-called brake output function has a brake circuit 30 which series circuit forms the semiconductor switch 28 and the diode 29, the negative terminal of the solar cell 1 _B and semiconductor switch 28 , The switching device 10 ′ is located between the connection point of the diode 29.

In this embodiment, since the brake output function is not used, the semiconductor switch 28 is normally turned off, and high frequency switching is performed only during the snow melting operation to control the applied voltage.

In addition, during the snow melting operation, the inverter 26 converts the system power supply in order to form DC power for snow melting, and the smoothing capacitor 25 is charged with the DC power.
The voltage is adjusted by opening and closing the semiconductor switch 28.

When the semiconductor switch 28 is turned on,
Based on the DC stored energy of the smoothing capacitor 25, a current flows through a loop returning to the smoothing capacitor 25 via the reactor 24, the switching device 10, the string 3x, the switching device 10 ', and the switch 28 of the snow melting power supply line 11, and the semiconductor switch 28 Is off, the reactor 24, the switchgear 10,
A current flows through a loop returning to the reactor 24 via the string 3x, the switching device 10 ', and the diode 29, and a reverse voltage controlled by the switching of the semiconductor switch 28 is applied to the string 3x. The same effects as in the first and second embodiments can be obtained.

By the way, the In the respective embodiments, the power converter 5, an inverter 26, forming a reverse conversion of the power output of the solar cell 1 _B, the DC power for snow-melting by performing the forward transform of the system power source It was way, the power converter 5, an inverter 26 and separately to provide a direct current power supply for generating a DC power for snow melting, and snow melting by supplying DC power of the power supply device to a string 3x of the solar cell 1 _B Is also good.

[0049] In addition, the solar cell 1 _B string 3a~3
It goes without saying that the number of stages of x and the like may be any.

In each of the above embodiments, the opening and closing device 10 is opened and closed during the snow melting operation, but may be kept open.

[0051]

The present invention has the following effects. Solar cells 1 _B is installed with a slope on the roof or the like, during the snow melting operation, a reverse voltage of the DC only the bottom of the string 3x solar cell 1 _B is applied from the snow melting power supply means, the solar cell at the heating outermost You can melt the snow in the lower section.

[0052] Then, the upper snow of the solar cell 1 _B This snow melting is entirely falls along the surface by the the fall and snow melting, the entire surface of the solar cell 1 _B snow and the bottom The snow can be melted by the heat generated by the string 3x.

Therefore, it is sufficient to provide only the snow melting power supply means such as the snow melting power supply path 11 of the lowermost string 3x. This snow melting power supply means balances the current balance with the strings of the other stages such as the shunt resistance of the conventional device. There is no need to provide a means for taking the same, the number of components is small, the device can be formed small and inexpensive, and the power consumption can be reduced as compared with the case where a DC reverse voltage is applied to all the strings 3a to 3x.

[0054] Therefore, the number of components is small size and inexpensive structure than a conventional device, it is possible to perform snow melting efficiently the solar cell 1 _B with less power consumption.

It is practical and preferable that the snow melting power supply means is formed by the power converter 5, the inverter 26 and the switchgear 10.

[Brief description of the drawings]

FIG. 1 is a single-line diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of energization during the snow melting operation of the solar cell of FIG.

FIG. 3 is a single-line diagram of a second embodiment of the present invention.

FIG. 4 is a single-line diagram of a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of energization during snow melting operation of a conventional solar cell.

FIG. 6 is a single-line diagram of a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 _A , 1 _B solar cell 2 module 3a-3x string 5 power converter 10 switchgear 11 snow melting power supply path

Claims (2)

[Claims] 1. A solar cell in which a plurality of modules are arranged in a matrix, and the modules in each row are connected in series for each row to form a string in each row; A snow melting power supply means for applying a DC reverse voltage only to the string. 2. A power converter that switches from a reverse conversion for converting an output of a solar cell to an AC to a forward conversion for converting an AC on a system side to a DC during a snow melting operation. A normally-open switchgear provided between the lower string and the power converter, and closed or opened only during a snow melting operation to supply the direct current to the lowermost string. Item 7. The snow melting device according to Item 1.