JPH11252803A - Photovoltaic power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent wasteful operation of a leakage breaker in the case of closing the linkage switch of an insulating type system linkage inverter by fitting a circuit fixing respective solar battery side circuits to a potential during running or a potential next to it in advance before making the linkage switch of the system linkage inverter. SOLUTION: A potential fixing circuit 31 is added, which makes the neutral potential of a system and the neutral potential of boosted DC potential the same potential. A resistor Z1=Z2=470 kΩ is used so that the neutral potential of boosting DC voltage may be obtained by resistive potential dividing, and its potential dividing point and a system side neutral line output point are connected. To adjust impedance of a solar battery input terminal and a system neutral line, a resistor of Z3=470 kΩ is provided. The potentials on both sides of the system linkage switch are equal to each other, and a potential difference in quantity of electricity passing through the system and be made zero, thus it is possible to prevent an earth leakage breaker from being tripped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generator for interconnecting a solar cell with an AC power system such as a commercial AC power system, and more particularly to an interconnection system for converting a DC output of a solar cell into AC power. The present invention relates to a photovoltaic power generator using a non-insulated inverter as an inverter.

[0002]

2. Description of the Related Art Residential photovoltaic power generation systems have also reached the stage of widespread use, and studies for cost reduction are being actively conducted. As this trump card, a roof-integrated solar cell module that does not require a mount and a non-insulated (so-called transformerless) inverter are being put into practical use.

FIG. 4 shows an example of a general grid-linked solar power generation apparatus. Electric power is transmitted from the solar cell array 61 to a commercial AC power system and a load 63 in a consumer via an inverter 62. A circuit breaker 64 with a leakage cutoff function is provided between the inverter and the commercial AC power system to completely disconnect the commercial AC power system when a leakage fault occurs in a customer.

[0004]

However, a solar cell has a relatively large area outdoors (for example, 30 KW at a capacity of 3 KW).
To be installed over m about ^2), and will have a stray capacitance which can not be ignored during the solar cell array 1 and the ground, is a minute leakage current for the resulting, earth leakage breaker 6
Furukawa et al. Pointed out that there is a danger that the F.4 may be operated unnecessarily in the paper No. 77 of the 1996 IEEJ National Conference on Industrial Applications.

[0005] If the earth leakage breaker actually operates, especially the earth leakage breaker for receiving power, the power is cut off to the customer. Further, even when a ground fault circuit breaker dedicated to a photovoltaic power generation inverter is installed, if a cutoff operation occurs, photovoltaic power generation is not performed and a power generation loss occurs.

This is a particular problem when the solar cell array 1 uses a transformerless inverter that is directly connected to the commercial AC power system or the load 63 without using an insulating transformer. Further, in a roof material integrated solar cell in which a solar cell element having a metal substrate is resin-sealed on a metal reinforcing plate (roof material), the metal reinforcing plate is grounded, and the space between the metal substrate and the metal reinforcing plate is increased. Because of the relatively large stray capacitance, unnecessary operation of the earth leakage breaker as described above is likely to occur.

[0007] For this reason, in the past, sufficient care was required in selecting the sizes of the earth leakage breaker and the solar cell array. In other words, the selection of the sizes of the earth leakage breaker and the solar cell array is greatly restricted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to prevent an unnecessary operation of an earth leakage breaker when an interconnection switch of an insulation type (transformerless) interconnection inverter is turned on. With the goal.

[0009]

In order to achieve the above-mentioned object, according to the present invention, prior to turning on the interconnection switch of the grid interconnection inverter, the potential of each part of the solar cell side circuit in operation or a potential close to it is previously determined. The circuit is provided with a circuit for fixing the circuit.

That is, a photovoltaic power generation device of the present invention comprises a photovoltaic array having a plurality of photovoltaic modules connected in series and in parallel, and an alternating current for connecting the output of the photovoltaic array to an alternating current power system. An insulated inverter that converts power, an interconnection switch and an earth leakage breaker connected between an AC output of the inverter and an AC power system, wherein at least the interconnection switch O
A potential fixing means for fixing the potential on the solar cell array side (DC side) from the interconnection switch to a predetermined potential at the time of FF (open circuit) is provided. This potential fixing means is provided, for example, on the DC side of the inverter.

In addition, the system interconnection inverter of the present invention converts DC power supplied from a solar cell array formed by connecting a plurality of solar cell modules in series and columns to AC power, and connects the interconnection switch and the earth leakage breaker. In a non-insulated system interconnection inverter for interconnecting with an AC power system via a switch, at least when the interconnection switch is opened, the solar cell array side (hereinafter, referred to as DC side) from the interconnection switch. A potential fixing means for fixing the potential to a predetermined potential is provided.

It is preferable that the DC side potential fixed by the potential fixing means is a neutral point potential of an interconnected AC power system. Further, it is desirable that the potential fixing means is connected only when the interconnection switch is opened, and is disconnected when the interconnection is performed.

[0013]

According to the above arrangement, when the interconnection switch is OFF,
The potential on the DC side is fixed to a predetermined potential (preferably the neutral point potential of the AC power system), and the potential difference between the DC side and the AC power system side when the interconnection switch is turned ON (closed) is compared. Limited to small. Therefore, the DC rush current determined by the product of this potential difference and the DC floating capacitance is limited to a relatively small value, and tripping of the earth leakage breaker due to the floating capacitance of the solar cell array to the ground can be prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The components of an example of a photovoltaic power generator to which the present invention is applied will be described below with reference to FIG. Numeral 61 in the figure denotes a roof material-integrated solar cell panel that generates DC power according to sunlight. Reference numeral 62 denotes a non-insulated inverter that converts DC power from a solar cell into commercial AC power and connects it to a commercial AC power system (hereinafter, referred to as a system). 63 is a domestic load, and 64 is an earth leakage breaker connected between the domestic load 63 and the interconnection inverter 62 and the system.

(Solar Cell Array 61) Solar Cell Array 6
Reference numeral 1 denotes a plurality of solar cell modules connected in series and in parallel. As the solar cell module, one obtained by sealing a solar cell element with a filler resin on a reinforcing plate is suitably used. Examples of the solar cell element include a crystalline silicon solar cell element, a polycrystalline silicon solar cell element, an amorphous silicon solar cell element, and a compound semiconductor solar cell element such as a copper indium selenide solar cell element.
Metal, glass, plastic, FRP as reinforcing plate
Etc. can be used.

As the filler, polyolefin resins such as ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), and butyral resin , Urethane resin, silicone resin and the like.
Further, a resin film such as a fluororesin or an acrylic resin is provided as a surface protection film.

In the case of a solar cell module using a metal plate as a reinforcing plate, the metal reinforcing plate can be bent to be a building material such as a wall material and a roof material. FIG.
Is an example of such a roofing integrated solar cell module,
FIG. 9A shows a roof material in which a ridge-side locking portion 81 and an eave-side locking portion 82 are assembled together, and FIG. 9B shows a locking member 83 fitted in a fixing member 84 fixed on a base plate 85. (C) is a roofing material that locks a locking portion 86 between adjacent roofing materials with a cap 87. A large number of photovoltaic devices (solar cell elements) 80 are provided on the light receiving surface of each roofing material. Is provided. In the case of a solar cell module using glass as a reinforcing plate, one whose periphery is reinforced with a metal frame is preferably used.

(Inverter 62) The inverter 62 is a transformerless inverter which does not use an insulating transformer between the DC side and the AC side, and has excellent conversion efficiency, light weight, and low cost because no transformer is used. There is. However, at the same time, there is a fate that the insulation from the commercial AC system (which is grounded) cannot be obtained. Further, in order to connect to a commercial AC system, it is necessary to provide a series of protection functions defined by the “Technical Guidelines for Interconnection”.

(Earth leakage breaker 64) An earth leakage breaker is a commercially available one, and has a zero-phase current (a sum of positive and negative currents).
Is detected, and when it becomes a certain value or more, the circuit breaker is operated. In the case of home use, a device having a leakage current sensitivity of 30 mA and an overcurrent protection function of about 30 A is often used. Of course, depending on the size of the building and the installation conditions, other sensitivities may be used.

[0020]

Embodiment 1 FIG. 6 shows a basic circuit of an interconnection inverter.
In the figure, reference numeral 21 denotes a positive input terminal for inputting power generated from the solar cell, and reference numeral 22 denotes a negative input terminal for inputting power generated from the solar cell. 23 is DC input from the solar cell
Booster circuit (DC-DC converter) for boosting the voltage, 2
Reference numeral 4 denotes an AC conversion circuit for converting the boosted DC voltage into alternating current by alternately rearranging the chopping polarity by semiconductor switching. 25 is an O between the inverter circuit and the system gun.
This is a system interconnection switch that performs N / OFF.

Here, in the circuit of FIG. 6, the potentials of the grid connection switch 25 on the solar cell side and the grid side are completely irrelevant and have different potential relationships. In other words, the grid connection side has a certain potential with respect to the earth because the neutral wire is subjected to the second-class grounding work, but the solar cell side has no electrical connection with the ground. Does not have a constant potential with respect to ground.

FIG. 7 shows an example of a potential relationship at each point of the inverter before the system interconnection switch is turned on (closed).
The potential of the solar cell output voltage indicated by 121 in FIG. 6 is indicated by 91 in FIG. The boosted DC voltage potential indicated by 122 in FIG. 6 is indicated by 92 in FIG. In this case, the AC potential on the solar cell side of the grid connection switch indicated by 123 in FIG. 6 is indicated by 96 in FIG. The AC potential on the system side of the system interconnection switch indicated by reference numeral 124 in FIG.
Indicated at 5. At that time, the neutral line potential 27 of the system is indicated by 94 in FIG.

In this state, the system interconnection switch 25 is turned on.
At the moment, the potential on the solar cell side becomes equal to the potential on the system side. At this time, the capacitance of the solar cell and 95, 96
The electric quantity Q = CV corresponding to the product of the potential difference 93 flows through the earth leakage breaker 64 in FIG. Where Q =
The amount of electric leakage pulse (C), C = capacitance (F) of the solar cell, and V = potential difference between the solar cell side and the system side before the interconnection switch is turned on.

This electric quantity Q = CV becomes a leakage pulse,
A difference current is generated in the breaker 64. The quantity of electricity (Q) at this time is determined by the capacitance value (C) of the solar cell and the potential difference (V) between the grid side and the solar cell side, and becomes a leakage pulse of leakage current average I and time t. The current value, pulse width, and waveform shape of the leakage pulse differ depending on the impedance of the system, the ground resistance value, and the like. When the leakage pulse exceeds the detection sensitivity of the leakage breaker, the breaker trips. Therefore, the tripping of the earth leakage breaker can be realized by eliminating the potential difference between the solar cell and the system before turning on the system interconnection switch 25.

Therefore, in the first embodiment of the present invention,
A circuit for making the midpoint potential of the system equal to the midpoint potential of the boosted DC voltage was added. This circuit is shown in FIG.

Reference numeral 31 in FIG. 1 is an example of such a potential fixing circuit. A resistor of の 中 1 = Z2 = 470 kΩ is used to obtain a midpoint potential of the step-up DC voltage by resistance voltage division. It was connected to the side neutral output point. Further, a resistance of Z3 = 470 kΩ was provided to adjust the impedance between the solar cell input terminal and the system neutral wire.

By adding this circuit 31, the potentials 95 and 96 on both sides of the system interconnection switch 25 in FIG. 7 become equal, and the quantity of electricity Q = CV flowing into the system through the earth leakage breaker (93 in FIG. 7). ) Can be set to 0,
The trip of the earth leakage breaker can be prevented.

[0028]

Embodiment 2 FIG. 2 is made for the same purpose as that of the first embodiment, and Z1 = Z so that the midpoint potential of the step-up DC circuit can be obtained.
A resistor of 2 = 470 kΩ was used and connected to the voltage dividing point equipment ground. Further, a resistance of Z3 = 470 kΩ was provided to adjust the impedance between the solar cell input terminal and the ground. Since the neutral line of the system is second-class grounded, even with this method, both sides of the system interconnection switch have the same potential before the switch is turned on, so that the earth leakage breaker can be prevented from tripping.

[0029]

Embodiment 3 FIG. 3 is made for the same purpose as the first embodiment, and Z1 = Z so that a midpoint potential of the step-up DC circuit can be obtained.
A resistor of 2 = 470 kΩ was used and connected to the voltage dividing point equipment ground. Further, a resistance of Z3 = 470 kΩ was provided to adjust the impedance between the solar cell input terminal and the ground.

In this embodiment, ON / OFF elements (switching elements) 52 and 53 are provided to disconnect Z1 and Z2 which become unnecessary and consume power after the start of system interconnection. ON / OFF element 52, 5
No. 3 makes the electric potential of the solar cell side of the interconnection switch equal to the electric potential of the system side by turning it on before the interconnection switch is turned on. After power generation is started after the connection switch is turned on, Z1,
In order to eliminate power consumption by Z2, the ON / OFF elements 52 and 53 are turned off.

The ON / OFF elements 52 and 53 can be constituted by semiconductor elements or mechanical switches such as relays. It is also possible to eliminate the Z1 and Z2 and control the point 54 in FIG. 3 to the same potential as the neutral potential by controlling the ON / OFF element itself using the semiconductor element.

[0032]

As described above, the use of the potential fixing means of the present invention makes it possible to prevent tripping of the earth leakage breaker when the system interconnection switch is turned on.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a grid interconnection inverter according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a grid interconnection inverter according to a second embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of a system interconnection inverter according to a third embodiment of the present invention.

FIG. 4 is a diagram illustrating a configuration of a photovoltaic power generation system as an example of an application target of the present invention.

FIG. 5 is a diagram showing an example of a roof material-integrated solar cell module in FIG. 4;

FIG. 6 is a diagram showing a configuration of a conventional general system interconnection inverter.

FIG. 7 is a diagram illustrating a relationship between potentials at respective points of an inverter before a system interconnection switch is turned on.

[Explanation of symbols]

21: + input terminal for inputting the generated power from the solar cell,
22: input power generated from the solar cell-side input terminal,
23: booster circuit, 24: AC converter circuit, 25: system interconnection switch, 27: neutral potential of commercial system, 31, 41,
51: potential fixing circuit, 52, 53: ON / OFF element,
61: roofing material integrated solar panel, 62: non-insulated inverter, 63: domestic load, 64: earth leakage breaker,
80: photovoltaic device, 81: ridge side locking part, 82: eave side locking part, 83: locking part, 84: fixing member, 85: field board, 86: locking part between adjacent roof materials , 87: cap, 91: potential of solar cell output voltage, 92: D after boost
Potential of C voltage, potential difference between 93:95 and 96, 94: neutral line potential of system, 95: AC on system side of system interconnection switch
Potential, 96: AC potential on the solar cell side of the system interconnection switch, 121: solar cell output voltage, 122: DC after boosting
Voltage, 123: AC potential on the solar cell side of the grid connection switch, 124: AC potential on the grid side of the grid connection switch.

Claims (10)

[Claims] 1. A solar cell array in which a plurality of solar cell modules are connected in series and in parallel, and a non-insulated inverter for converting an output of the solar cell array into AC power for connecting to an AC power system. A photovoltaic power generator comprising: an interconnection switch and an earth leakage breaker connected between an AC output of the inverter and an AC power system, wherein at least when the interconnection switch is opened, A photovoltaic power generation device comprising a potential fixing means for fixing a potential on a solar cell array side to a predetermined potential. 2. The photovoltaic power generator according to claim 1, wherein said potential fixing means is provided in said inverter. 3. The photovoltaic power generator according to claim 1, wherein the potential fixing means fixes the potential of the solar cell array to a neutral point potential of the AC power system. 4. The apparatus according to claim 1, further comprising switching means for disconnecting said potential fixing means from said solar cell array and said inverter when said interconnection switch is closed. Solar power generator. 5. The solar power generation device according to claim 1, wherein the solar cell module has a structure in which a solar cell element is resin-encapsulated on a reinforcing plate. 6. The photovoltaic power generator according to claim 5, wherein said reinforcing plate is made of metal. 7. The solar power generation device according to claim 1, wherein the solar cell has a metal substrate. 8. The photovoltaic power generator according to claim 1, wherein the solar cell element has a non-single-crystal semiconductor. 9. The solar power generation device according to claim 1, wherein the solar cell module is a building material. 10. A DC power supplied from a solar cell array comprising a plurality of solar cell modules connected in series and in parallel is converted into AC power, and connected to an AC power system via an interconnection switch and an earth leakage breaker. A non-insulating type system interconnection inverter for operating the system, wherein at least when the interconnection switch is opened, a potential fixing means for fixing a potential on the solar cell array side from the interconnection switch to a predetermined potential is provided. A non-insulated system interconnection inverter characterized by the following.