Inverter and photovoltaic apparatus

According to one embodiment, an inverter includes a housing having a corner, a DC terminal, an electronic component, an AC terminal, a wireless communication module, and a projection mechanism. The DC terminal inputs DC power. The electronic component converts the DC power input to the DC terminal into AC power. The AC terminal outputs the AC power from the electronic component to the outside of the housing. The wireless communication module includes an antenna which receives or transmits a signal for controlling the electronic component. The projection mechanism projects at least a part of the antenna into the outside of the housing. The projection mechanism is provided in a portion of the housing other than the corner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-091371, filed Apr. 28, 2015, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an inverter and a photovoltaic apparatus comprising the inverter.

BACKGROUND

For example, various systems configured to obtain power from power generators such as solar cells and fuel cells are known. One example of the systems is a centralized control system configured to integrally control a plurality of solar panels by a power conditioner. In a centralized control system, all the direct current (DC) power generated by a plurality of solar panels is collectively converted into alternating direct (AC) power by a single power conditioner.

These days, a new system such as a decentralized control system has been gathering attention as an alternative to the above-described centralized control system. In a decentralized control system, inverters are connected respectively to a plurality of solar panels. The inverters convert DC power into AC power individually for the respective solar panels.

Further, in the decentralized control system, there is demand for a technique to perform power generation control or monitoring of each solar panel using wireless communication. In response to the demand for the technique, a method of, for example, providing an inverter with a wireless communication module has been proposed. In this method, a wireless communication module is accommodated in a housing together with an inverter circuit.

In this case, the housing needs to be made of a metal material to maintain a certain strength (rigidity) for the entire housing. In a wireless communication module, a portion effective as an antenna (antenna portion) is required to achieve high antenna performance or wireless communication performance. Note that the antenna performance is degraded when the antenna portion approaches the housing (metal). The wireless communication performance is degraded when the antenna portion is influenced by noises produced by the inverter.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment, an inverter includes: a housing having a corner; a DC terminal, an electronic component; an AC terminal; a wireless communication module; and a projection mechanism. The DC terminal inputs DC power. The electronic component converts the DC power input to the DC terminal into AC power. The AC terminal outputs the AC power from the electronic component to the outside of the housing. The wireless communication module includes an antenna which receives or transmits a signal for controlling the electronic component. The projection mechanism projects at least a part of the antenna into the outside of the housing. The projection mechanism is provided in a portion of the housing other than the corner.

FIG. 1illustrates an inverter1of an embodiment.FIG. 2illustrates a photovoltaic apparatus2of an embodiment. The photovoltaic apparatus2comprises the inverter1and a solar panel3. The solar panel3has such a structure as to integrally support a plurality of solar cell elements called cells (not shown) by a frame4. Note that each solar cell element (in other words, photovoltaic power generator) is a semiconductor (in other words, semiconductor device) configured to output an electrical signal (DC power) based on the amount of light received when, for example, sun light enters. Further, note that the solar panel3comprises an entrance surface3aand a back surface3bon the side opposite to the entrance surface3a.FIG. 2illustrates a structure on the side of the back surface3bof the solar panel3.

Here, one solar panel3is, although not particularly shown in the drawing, formed of cells (solar cell elements) arranged for a necessary number, protected by resin, reinforced glass or the like, and fixed externally by, for example, a frame made of aluminum or the like.

The inverter1can be detachably fixed to the frame4. In this case, although the frame4is not limited to a particular structure, the frame4of the present embodiment is assumed to have a shape projecting to the side of the back surface3bof the solar panel3. The inverter1has such a structure as to be placed within a projection width of the frame4having a projecting shape. Note that the inverter1may be fixed to a stand instead. The stand may be provided, for example, as a scaffold for setting the solar panel3on a roof, in a field or the like.

In the solar panel3, the DC power generated by the plurality of solar cell elements is supplied to the inverter1through a terminal box5provided on the back surface of the solar panel3. The supplied DC power is input to the inverter1from a DC terminal17which will be described later. The inverter1comprises an electronic component which will be described later such as, for example, an inverter circuit7. The DC power input to the inverter1is converted into AC power by the inverter circuit7. The AC power is then output from an AC terminal18which will be described later.

As shown inFIGS. 1 to 4, the inverter1comprises a housing6, the inverter circuit7, the wireless communication module8, the projection mechanism9and a fixing mechanism. The entire housing6(or at least a corner16which will be described later) is made of a metal material. Here, a material such as aluminum or stainless steel can be applied as the metal material.

The inverter circuit7comprises an inverter unit7aand a control unit7b. The inverter unit7acomprises a circuit configured to convert DC power into AC power. The control unit7bis configured to control the inverter unit7a. The control unit7bcomprises a control circuit. Here, the control of the inverter unit7ais assumed to include, for example, routine control to convert DC power into AC power, control of power generation status (such as a power generation amount, a power generation timing and the like) of the inverter unit7aand the like.

The wireless communication module8comprises a wireless circuit10, an antenna11and a substrate12. The antenna11is configured to transmit or receive a signal to perform wireless control of the inverter circuit7(inverter unit7aand control unit7b). The wireless circuit10is configured, for example, to input a signal received from the antenna11to the control unit7bor to transmit a signal output from the control unit7bto the antenna11. The control unit7bis configured to control the operation of the inverter unit7abased on a signal input from the wireless circuit. Further, the control unit7boutputs a signal of the operation status of the inverter unit7ato the wireless circuit. The wireless circuit10and the antenna11are provided on the same substrate12. For example, the wireless circuit19and an antenna pattern are formed on the same substrate12.

Further, the wireless communication module8is conforming to a sub-gigahertz band wireless communication. The sub-gigahertz band wireless communication is a frequency band of 1 GHz or less. A frequency band available as the sub-gigahertz band varies from country to country. In Japan, a communication frequency band of 920-MHz is set as the sub-gigahertz band. In this case, the wireless communication module8can perform a 920-MHz band wireless communication with a gateway27which will be described later.

According to the 920-MHz band wireless communication, it is possible to improve the traveling distance of radio waves with lower power consumption as compared to a wireless communication in the 2.4-GHz band. In this way, a large-scale multi-hop network can be built. Further, the 920-MHz band wireless communication exhibits better wraparound characteristics of radio waves as compared to the 2.4-GHz band wireless communication, which ensures a stable communication, for example, even in a place where there are walls or obstacles.

The housing6accommodates the inverter circuit7and the wireless communication module8. The housing6comprises a lid6aand a container6b. The container6bcomprises an open portion (not shown). The inverter circuit7and the wireless communication module8can be accommodated in the container6bfrom the opening. The opening of the container6bcan be closed by the lid6a. In a state where the opening is closed by the lid6a, the internal space (internal space for accommodating the inverter circuit7and the wireless communication module8) is kept sealed off from the outside.

The housing6comprises two surfaces (for example, flat surfaces)13and14, and a plurality of side surfaces (for example, flat side surfaces)15. These two flat surfaces13and14are arranged in such a manner as to face each other. The side surfaces15are arranged in such a manner as to surround a space formed between these two surfaces13and14. Here, the flat surface14is assumed to be the outer surface of the lid6a, and the flat surface13is assumed to be the outer surface of the container6b. The side surfaces15are assumed to be a region including the side surfaces of the lid6aand the side surfaces of the container6b.

The housing6comprises a plurality of corners16. The corners16are formed between adjacent side surfaces15of the plurality of side surfaces15. According to the above-described structure, it is possible to define the housing6as a hexahedron having an outline of a polygon (such as a quadrangle, a pentagon, a hexagon or the like). In the drawing, the housing6assumed to be a hexahedron having a quadrangular outline is shown as an example. In this case, the corner16is formed by adjacent side surfaces15and having a right angle. Note that the corner16may have a curvature.

The housing6is provided with a pair of DC terminals17and an AC terminal18. The DC terminals17are configured to input DC power to the inverter circuit7. The AC terminal18is configured to output AC power from the inverter circuit7. The DC terminals17and the AC terminal18are provided on the side surfaces15of the housing6. The side surface15provided with the DC terminal17and the side surface15provided with the AC terminal are orthogonal to each other.

The DC terminals17and the AC terminal18are electrically connected to the inverter unit7aof the electronic component7. The DC terminals17are electrically connected to the above-described terminal box5via a pair of DC cables19. From the AC terminal18, an AC cable extends.

In this structure, DC power generated by the solar panel3is supplied from the terminal box5to the inverter unit7avia the DC cables19and the DC terminal17. In the inverter unit7a, the DC power is converted into AC power. The AC power is then supplied from the AC terminal18to the outside (for example, an AC collector29[FIG. 5]) via the AC cable20.

The housing6is provided with the projection mechanism9. The projection mechanism9is configured to project at least a part of the above-described antenna11into the outside of the housing6. A projection mechanism9is provided in a portion of the housing6other than the corners16. In this case, the portion other than the corners16may be, for example, the two flat surfaces13and14or the side surfaces15. In the drawing, a structure in which the projection mechanism9is provided on the side surface15is shown as an example. More specifically, the projection mechanism9is provided on the side surface15provided with the DC terminal17.

The projection mechanism9comprises an opening21and a cover22. The opening21is formed in such a manner as to penetrate through a part of the housing6(side surface15). The side surface (first side surface)15provided with the opening21is different from the side surface (second side surface)15provided with the AC terminal18. In this case, the first side surface15is orthogonal to the second side surface15. The opening21and the DC terminal17are provided on the same side surface (that is, first side surface). The distance between the opening21and the second surface15is shorter than the distance between the DC terminal17and the second surface.

Further, the opening21is set to be in such a shape or a size as to project at least a part of the antenna11into the outside of the housing6. Here, the part of the antenna11can be defined, for example, as a part of the antenna portion11bof the antenna pattern printed on the substrate12(portion configured to transmit and receive radio waves) extending from a feed point11a. In the drawing, a state in which a part of the antenna portion11bprinted on the substrate12projects together with the substrate12from the opening21is shown as an example.

Further, the cover22is provided in such a manner as to cover the opening21. The cover22covers at least the part of the antenna11projecting into the outside of the housing6through the opening21. The cover22is formed of a nonmetal material. Here, a material such as ABS, polycarbonate or the like can be applied as the nonmetal material.

More specifically, the cover22comprises a fixed portion22aand a cover body22b. The fixed portion22ais fixed to the housing6in such a manner as to surround the opening21. As a method of fixing the fixed portion22ato the housing6, for example, a method of affixing the fixed portion22aon the housing6, a method of screwing the fixed portion22aon the housing6, or the like can be applied. The cover body22bis formed continuously from the fixed portion22a. The cover body22bhas such an outline as to have the interior bulging outward.

In this structure, the fixed portion22ais fixed to the housing6in such a manner as to surround the opening21. In this way, a part of the antenna11projected into the outside of the housing6through the opening21can be accommodated in the cover body22b. Consequently, the antenna11can be kept under an environment sealed off from the outside. As a result, it is possible to prevent early deterioration of the antenna11or the wireless communication module8.

The housing6is provided with the fixing mechanism. The fixing mechanism is configured to detachably fix the inverter1to the frame4. The fixing mechanism comprises a plurality of fixed portions23and a plurality of fixing screws24. The fixed portions23are arranged along the side surfaces15of the housing6at intervals. The fixed portions23comprise screw holes25. The fixing screws24are screwed into the screw holes25.

The fixed portions23are provided on the side surfaces15not provided with the projection mechanism9, the DC terminals17and the AC terminal18. In the present embodiment, two fixed portions23are provided on the side surface15opposite to the side surface15provided with the projection mechanism9and the DC terminal17, and other two fixed portions23are provided on the side surface15opposite to the side surface15provided with the AC terminal18. These fixed portions23(screw holes25) are provided in such a manner as to correspond to the positions of a plurality of fixing holes4h(FIG. 4) formed in the frame4.

In this structure, for example, the fixed portions23are provided on the back surface side of the frame4provided with the fixing holes4h. In this state, the screw holes25are placed in such a manner as to face the fixing holes4h. The fixing screws24are inserted into the fixing holes4hfrom the front surface side of the frame4. The fixing screws24are then screwed into the screw holes25. In this way, the fixed portions23are fixed to the frame4. As a result, the inverter1can be fixed to the frame4.

In this state, the inverter1is placed within the projection width of the frame4. In this case, it becomes possible, for example, under such an environment as to accommodate and manage a plurality of photovoltaic apparatuses2in one place, to pile the photovoltaic apparatuses2(solar panels3) without a gap therebetween. In this way, it is possible to make an accommodation and management space compact.

Further, with the fixing mechanism, a gap26is formed between the inverter1and the solar panel3in a state where the inverter1is fixed to the frame4. It becomes possible by the gap26to prevent in advance such a situation where the inverter1contacts and thus damages the solar panel3. Still further, in a state where the inverter1is fixed to the frame4, the projection mechanism9can be provided in such a position as to avoid interference with the plurality of cables19and20connected to the DC terminals17and the AC terminal18.

Effect Produced by Embodiment

According to the present embodiment, (the entire or at least the corner16of) the housing6is formed of a metal material. Further, the projection mechanism (opening21) configured to project at least a part of the antenna11into the outside of the housing6is provided on a portion other than the corners16of the housing6, namely, on the side surface15. In this way, a certain strength (rigidity) of the housing6can be maintained. In particular, in the case of forming the opening21on the side surface15, the notch of the housing6can be made smaller as compared to the case of forming the opening21through the corner16. Therefore, the strength (rigidity) of the housing6can be ensured easily for the entire housing6.

Further, according to the present embodiment, it is possible by providing the projection mechanism (opening21) with the housing6to project at least a part of the antenna11into the outside of the housing6. In this case, at least a part of the antenna11is exposed to the outside of the metallic housing6. In this state, the exposed portion of the antenna11is less likely to be influenced by the housing6(metal). Further, the exposed portion of the antenna11is separated from the inverter circuit7(inverter unit7a). Therefore, the exposed portion of the antenna11is less likely to be influenced by noises produced by the inverter circuit7(inverter unit7a). As a result, it is possible to realize the inverter1(wireless communication module8) which can achieve excellent antenna performance and wireless performance.

Still further, according to the present embodiment, a 920-MHz band wireless communication can be established between the wireless communication module8and the gateway27via the antenna11which achieves excellent antenna performance and wireless performance. In this way, it is possible to control or monitor the power generation status (such as a power generation amount, a power generation timing and the like) of the inverter circuit7(inverter unit7a) with high accuracy.

Still further, according to the present embodiment, a wireless communication is directly performed between the wireless communication module8and the gateway27. Therefore, for example, in a power generation system comprising a plurality of photovoltaic apparatuses2(solar panels3) as shown inFIG. 5, the photovoltaic apparatuses2can be controlled individually by the single gateway27. For example, even if the power generation by one photovoltaic apparatus2(solar panel3) decreases, it is possible to compensate the decrease by individually controlling the power generation of the other photovoltaic apparatuses2(solar panels3). In this way, it is possible to stabilize the amount of power collected to the AC collector29from the AC cable20through a junction cable28.

Note that the above-described embodiment is in no way restrictive and the following modified examples also fall within the same technical scope.

First Modified Example

FIG. 6illustrates an inverter1of the first modified example.FIG. 7illustrates a photovoltaic apparatus2comprising the inverter1of the first modified example. In the inverter1of the first modified example, a pair of DC terminals17and an AC terminal18are provided side by side along one long side surface15. Based on the layout of the DC terminals17and the AC terminal18, an inverter circuit7(inverter unit7aand control unit7b) is provided.

A projection mechanism9is provided in a portion of a housing6other than corners16. Fixed portions23are provided on the side surfaces15not provided with the projection mechanism9, the DC terminals17and the AC terminal18. Note that structures other than those described above and effects are similar to the structures of and the effects produced by the above-described embodiment and thus descriptions thereof are omitted.

Second Modified Example

FIG. 8illustrates an inverter1of the second modified example.FIG. 9illustrates a photovoltaic apparatus2comprising the inverter1of the second modified example. In the inverter1of the second modified example, a pair of DC terminals17and an AC terminal18are provided side by side along one short side surface15. Based on the layout of the DC terminals17and the AC terminal18, an inverter circuit7(inverter unit7aand control unit7b) is provided.

A projection mechanism9is provided in a portion of a housing6other than corners16. Fixed portions23are provided on the side surfaces15not provided with the projection mechanism9, the DC terminals17and the AC terminal18. Note that structures other than those described above and effects are similar to the structures of and the effects produced by the above-described embodiment and thus descriptions thereof are omitted.

Third Modified Example

FIG. 10illustrates an inverter1of the third modified example.FIG. 11illustrates a photovoltaic apparatus2comprising the inverter1of the third modified example. In the inverter1of the third modified example, a pair of DC terminals17and an AC terminal are provided on short side surfaces15facing each other. Based on the layout of the DC terminals17and the AC terminal18, an inverter circuit7(inverter unit7aand control unit7b) is provided.

A projection mechanism9is provided in a portion of a housing6other than corners16. Fixed portions23are provided on the side surfaces15not provided with the projection mechanism9, the DC terminals17and the AC terminal18. Note that structures other than those described above and effects are similar to the structures of and the effects produced by the above-described embodiment and thus descriptions thereof are omitted.

Fourth Modified Example

FIG. 12illustrates an inverter1of the forth modified example.FIG. 13illustrates a photovoltaic apparatus2comprising the inverter1of the fourth modified example. In the inverter1of the fourth modified example, a pair of DC terminals17and an AC terminal18are provided on short sides15facing each other. Based on the layout of the DC terminals17and the AC terminal18, an inverter circuit7(inverter unit7aand control unit7b) is provided.

A projection mechanism9is provided in a portion of a housing6other than corners16. Fixed portions23are provided on the side surfaces15not provided with the projection mechanism9, the DC terminals17and the AC terminal18.

In the present modified example, a wireless circuit10and an antenna11are arranged separately from each other. In the drawing, a structure in which the wireless circuit10and the antenna11are provided on different substrates12aand12bis shown as an example. That is, the wireless circuit10is provided on one substrate12a, and the antenna11is provided on the other substrate12b. Both substrates12aand12b(that is, the wireless circuit10and the antenna11) are electrically connected to each other by a coaxial cable30. Note that structures other than those described above and effects are similar to the structures of and the effects produced by the above-described embodiment and thus descriptions thereof are omitted.

Fifth Modified Example

In the above-described embodiment and the first to fourth modified examples, the antenna11is preferably provided in such a manner as to prevent the antenna11from overlapping with the frame4in a state where the inverter1is detachably fixed to the frame4. That is, in the housing6, the antenna11is preferably projected from a portion (side surface15) other than a portion (side surface15) adjacent to the frame4. In other words, the antenna11is preferably projected from such a portion (side surface15) as to avoid the frame4. In this way, degradation of antenna performance by the influence of the frame4can be prevented.