DE102014116765A1 - PHOTOVOLTAIC POWER PLANT AND INVERTER FOR A PHOTOVOLTAIC POWER PLANT - Google Patents

Abstract

A photovoltaic power plant (1) for feeding electrical energy from a plurality of PV fields (2) into a power grid (31) is disclosed. The individual PV fields (2) are each connected via DC lines (12) to a DC input (21) of an inverter (20) assigned to the PV field (2), the inverter (20) being connected on the output side via a transformer (40) connected to the power grid (31). Each PV array (2) is formed of a plurality of module arrays (3), each module array (3) comprising a plurality of PV modules (4). The transformer (40) is designed as a power transformer, which feeds directly into overhead lines (32) of a high-voltage power supply network (30). The DC lines (12) are directly to module junction boxes (16) of the individual PV modules (4) or by means of electrically insulating brackets (10) attached to elevations (5) on which the PV modules (4) are mounted , An inverter (20) as part of the photovoltaic power plant (1) is also described in detail.

Description

Technical field of the invention

The invention relates to a photovoltaic power plant for feeding electrical energy from a plurality of PV fields in a power grid preferably directly into a high-voltage network. Furthermore, the invention comprises a concept for guiding the DC lines in the PV field and for connecting them to the inverter.

State of the art

In recent years, ever larger photovoltaic power plants have been built worldwide. These power plants can make a significant contribution to the generation of electricity from renewable energies, especially in sunny regions. Photovoltaic power plants of some 100 MW (for example Agua Caliente Solar Project) have already been built, those with more than 1 GW are planned (for example Westlands Solar Park). However, the price pressure on the operators of such photovoltaic power plants, which are in direct competition with conventional coal, gas and nuclear power plants, is steadily rising.

Since such high-performance photovoltaic power plants have a correspondingly high space requirement, in particular the cost of DC cabling within the photovoltaic panels increases and also the DC connection area in the inverters for connection to the photovoltaic panels increases correspondingly with increasing photovoltaic power. In addition, problems arise here in terms of due to the correspondingly high DC voltages necessary in comparison to small systems more complex insulation of the cable, which in addition to higher material costs also negative influences on the mechanical properties of the cable and thus on their handling during installation result. This is especially in the case of the prior art (eg DE 10 2011 053 523 A1 ) commonly described inverters is a problem because here due to the laying of the cables in the ground corresponding radii of curvature of the cable to connect these to the DC input of the inverter are needed.

From the DE 10 2009 004 679 B3 For example, a power supply system with a photovoltaic device is known which comprises a plurality of DC-generating PV modules, where the photovoltaic modules are connected in parallel and / or series connection with one another and exceed the dielectric strength of the photovoltaic modules and the high-voltage DC transmission generate suitable DC voltage. The power supply system has a forming station which can be connected to a power supply network arranged for consumers and comprises a high-voltage direct-current transmission link (HVDC) in order to transmit the DC voltage generated by the photovoltaic device in the high-voltage region to the forming station. The HVDC route can be designed both for long distances, preferably over overhead lines, as well as for short distances, preferably via cables. At the end of the HVDC line, only conversion from the transmitted DC voltage to a desired AC voltage is required. In particular, the inverters and HVDC rectifier stations required in the conventional systems on the generator side are saved.

Object of the invention

The invention has for its object an apparatus with the features of the preamble of independent claim 1 and an inverter for such a device to show that both reduces the cost of building particular large photovoltaic power plants, as well as facilitates the maintenance of such power plants.

solution

The object of the invention is achieved by a photovoltaic power plant with the features of independent claim 1. The dependent claims 2 to 10 are directed to preferred embodiments of a photovoltaic power plant according to the invention. The claim 11 relates to an inverter for a photovoltaic power plant according to the invention.

Description of the invention

The invention relates to a photovoltaic power plant for feeding electrical energy from a plurality of photovoltaic panels (hereinafter referred to as PV fields) in a power grid, wherein the individual PV fields via DC lines (hereinafter DC lines) each with a DC voltage input (hereinafter short DC input) of the PV array associated inverter are connected, the output side is connected via a transformer to the power grid. Each PV field is made up of a plurality of module fields, each of which has a multiplicity of photovoltaic modules (in the following abbreviated to PV modules). The PV modules are installed within the module fields such that a system voltage greater than 1 kV DC, preferably greater than 5 kV based on the voltage difference between the DC lines is obtained. These compared to the system voltages of 600 V usually used in large plants Up to 1000 V high DC voltages allow the use of appropriate inverters that implement correspondingly higher power at the same DC current. In this way, compared to existing systems, the number of inverters and other system components related to the power plant performance can be reduced. This reduces in particular the cost and the cost of installation and maintenance of photovoltaic power plants. Between the transformer and the power grid is usually still a substation or high voltage switchgear. Such a substation or such a high-voltage switchgear includes, for example, a separator that allows separation of the power plant from the power grid, a grounding device that grounds the separated part of the system, a circuit breaker, one or more transducers for measuring eg current and voltage and possibly also other measuring and switching devices, which are well known from the prior art.

In an embodiment according to the invention, the individual module fields are connected via overhead lines directly or via safety devices to the DC line. The cables are routed by means of electrically insulating brackets, which are attached to supports on which the PV modules are mounted or to additionally installed DC power poles. In this case, the individual PV modules can be interconnected by means of DC overhead lines.

In another embodiment, the support of the DC lines is carried out directly without additional electrically insulating brackets on the respective module junction boxes, which are mounted on the underside of the PV modules in such a way that the largest possible clearance and creepage distances to all conductive components of the elevation observed become. In both cases, lines without insulation can be used instead of electrically insulated lines, if appropriate electrically insulating brackets used and creepage distances and clearances are met.

In an embodiment according to the invention, the DC lines between the PV array and the respective inverter are constructed above ground as DC overhead lines. These cables can be dispensed with, unlike cables laid in the ground on an electrical insulation of the lines. In this way, material costs can be saved compared to insulated cables. In addition, the lack of electrical insulation of the lines leads to better heat dissipation and thus to a lower thermal load on the lines. In this way, the use of cables with cables of smaller cross-sections and / or cables made of materials with a poorer electrical conductivity, which are laid in the ground, can further save costs. The DC overhead lines, if this should be necessary due to the distance to be bridged, can be guided by means of DC power pylons having corresponding electrically insulating holders.

In a preferred embodiment, a corresponding DC power pole, e.g. the central DC power pole and the inverter housing a unit to save additional earthworks, such as a corresponding foundation. The DC overhead lines are connected via taps directly to insulator feedthroughs, which are preferably located on the roof or on the sidewalls of the inverter. In this way, the otherwise customary DC connection region in the inverter housing can be dispensed with, since according to the invention it is now routed to the outside. Small radii of curvature when connecting the lines can be avoided when using overhead lines by suitable guidance of these lines. Due to the lack of insulation of the cables they are also mechanically more flexible compared to corresponding underground cables.

In a further embodiment of the invention, the transformer has two primary windings and a secondary winding, wherein in each case exactly one inverter is connected on the output side to a primary winding of the transformer. Furthermore, the transformer can be designed as a power transformer which feeds directly into overhead lines of a high-voltage power supply network (high voltage = voltage> 50 kV, usually 110 kV).

In a further embodiment according to the invention, it is preferred that the inverters, their associated transformers and also the overhead lines of the power supply network, e.g. may also be a high voltage power supply network to arrange along a central, drivable path. In this way, in particular the heavy components, e.g. Substation, high-voltage switchgear, transformers and inverters during the installation of the PV power plant by means of appropriate transporters via the central, accessible way, as well as in the case of maintenance can be achieved easily about this. It is advantageous if an expansion of the PV fields perpendicular to the central, drivable path by at least a factor of 5, preferably by at least a factor 10 is greater than an extension parallel to the central, drivable path. But according to the invention other geometries of the PV fields are also conceivable.

Furthermore, the invention relates to an inverter for a photovoltaic power plant according to the invention, as described above. In one embodiment of the invention, such an inverter is characterized in that it comprises a housing, on whose top and / or side walls insulator bushings are mounted, which electrically insulates against the housing electrical connection of the above-ground DC lines from the outside into the Inside of the inverter. In this way, the DC connection area located in the housing of the inverter, which is customary in the state of the art, can be omitted and shifted outwards. This makes it possible to make the housing of the inverter smaller and subsequently cheaper. In addition, the connection of the AC output of the inverter to the transformer can be made in a similar manner by means of overhead lines. In this case, the inverter has further insulator bushings for connecting the AC cables. Depending on the distance between the inverter and the transformer, it may also be preferable to realize the electrical connection of the inverter to the transformer by means of ground lines, busbars or in a similar manner.

Brief description of the figures

The invention will be described in more detail by means of exemplary embodiments with reference to the drawing. Show it:

1 a schematic structure of a photovoltaic power plant,

2 a detailed view (schematically) of the connection of a PV string to DC power poles,

3 a detailed view (schematically) of the leadership of the DC lines,

4 a side view (schematic) of the elevation of a module array with several superposed PV modules and the associated module junction box and

5 a detailed view (schematic) of the connection of the module fields to the inverter via DC overhead lines.

figure description

The 1 schematically shows a section of a structure of a photovoltaic power plant according to the invention 1 , Shown here are only relevant for the invention components of such a photovoltaic power plant. Other components, such as filters, separation and safety devices are not shown for the sake of clarity. The individual PV modules 4 a module field 3 are connected in series here. Such an interconnection is also called a PV string 3 designated. A large number of PV strings connected in parallel form a PV field 2 , where the PV strings of a PV field 2 in each case the same number of PV modules 3 exhibit. This can be the photovoltaic power plant 1 a variety of PV fields 2 exhibit.

The spatial extent of the PV fields 2 is determined by the length of the associated PV strings 3 as well as the number of PV strings connected in parallel. In the following, let L be a PV field 2 , the spatial extent of the PV field 2 due to the length of the PV strings and width B of the PV field, the spatial extent due to the parallel arrangement of a plurality of PV strings referred to. In this case, the width B of the PV field 2 for example, by a factor of 5 to 20 greater than the length L of the PV field. For the sake of clarity are in the 1 only a few PV modules (indicated by corresponding circuit symbols) within the individual strings and also only a few PV strings are shown. The dots illustrate the omitted components.

The number and arrangement of DC power poles 14 is to be adapted to the specific requirements of a real photovoltaic power plant and in the 1 only indicated by way of example. The elevation 5 the PV modules is not shown here.

About the DC lines 12 that are here as DC overhead lines 13 executed, the connection of the PV fields 2 to the respective DC inputs 21 the PV fields 2 associated inverter 20 , The AC outputs 22 the inverter 20 are over a transformer 40 with the power supply network 31 connected. In the 1 points the transformer 40 two primary windings 41 for connection of one inverter each 20 and a secondary winding 42 for connection to the power supply network 31 on. It should be mentioned that, of course, other transformers, for example, each with two primary and secondary windings can be used. Or that each inverter is connected directly via a transformer only associated with each having a primary and secondary winding to the power grid.

The arrangement of the transformers 40 and the inverter 20 takes place along a central, paved path 33 and are therefore also accessible with correspondingly heavier vehicles, such as a truck or a crane car. Parallel to this way 33 are masts 34 of the power supply network 31 for the management of overhead lines 32 an energy supply network 31 arranged. The power supply network 31 Can also be used as a high voltage power supply 30 be educated. The PV fields 2 are on both sides of the way 33 with its shorter side designated L parallel to the path 33 is aligned. Between the transformer 40 and the power grid 31 is usually still a substation or a high voltage switchgear, which is not shown in the figure.

2 schematically shows a possible inventive variant of the connection of a PV string 3 on DC power poles 14 , The PV modules 4 are on an elevation 5 , which is indicated in the figure by the corresponding support posts and each have a module junction box 16 , where the positive pole of a PV module 4 with the negative pole of the adjacent PV module 4 connected is. The positive pole of the first PV module 4 ' of the PV string is by means of a positive DC connection cable 17 and a safety device 11 with the DC line 12 ' connected in the 2 runs perpendicular to the drawing plane. The negative pole of the last PV module 4 '' of the PV string is by means of a negative DC connection line 18 and another (optional) security device 11 with the DC line 12 '' connected. The two DC lines 12 ' and 12 '' be by means of insulating bracket 10 on DC power pylons along side B on both sides of the PV array 2 guided. In an embodiment, in the DC connection lines 17 / 18 and the DC lines between the module junction boxes 16 to be dispensed with electrical insulation of the lines, if appropriate distances, for example, to the elevation 5 be respected.

Alternatively to the in 2 shown leadership of the DC line is in 3 schematically another variant of the holder of the DC cables 12 shown where the DC lines on both sides of the PV strings 3 directly via the module junction boxes 16 each outer PV modules 4 ' . 4 '' the other PV strings 3 of the PV field 2 connected to each other. Alternatively, additionally or solely further electrically insulating holder 10 to guide the DC cables 12 directly at the elevations 5 the PV modules 4 be provided.

In the 4 is a schematic side view of an elevation of PV modules 4 shown at the multiple PV modules 4 - here 3 PV modules - arranged one above the other. In this embodiment, there are three stacked PV strings 3 , wherein the positive and the negative DC connection line 17 / 18 individual PV strings directly via the module junction boxes 16 the respective outer PV modules are connected to each other. Here too, an additional electrically insulating holder 10 at the elevation 5 to guide the DC cables 12 be provided. The connection of the DC lines 12 The PV strings on these elevations with PV strings on further elevations can be logged in the in 2 or 3 manner described done.

Like in the 5 indicated, be on the way 33 facing side of the PV field 2 the two DC lines (positive and negative lines) 13 on a central DC power pole 15 merged and from there via other DC power poles to the inverter 20 guided. 5 shows the central DC power pole 15 and another at the inverter 20 arranged power pole 25 for guiding the lines. At the top of the inverter housing 24 There are isolator bushings 23 , the one electrically insulated against the inverter housing electrical connection of the above-ground DC overhead lines 13 from the outside into the interior of the inverter 20 enable. The connection lines 26 between the DC overhead line 13 and the inverter 20 can, as in the 5 shown in the area or on special brackets of the mast 25 , with the DC overhead line 13 be connected.

In the 5 are next to the DC side insulator bushings 23 also further isolator bushings 23 ' provided that the AC output 22 of the inverter 20 with the primary windings 41 of the transformer 40 also connect by overhead line. This is not shown in the figure. Depending on the distance between the inverter and the transformer, it may also be preferable to realize the electrical connection of the inverter to the transformer by means of ground lines, busbars or in a similar manner.

LIST OF REFERENCE NUMBERS

1

 Photovoltaic power plant

2

 PV field

3

 Module Field / PV strings

4

 PV module

5

 elevation

10

 insulating bracket

11

 safety device

12

 DC line

13

 DC overhead line

14

 DC power pole

15

 Central DC power pole

16

 Module Wall Outlet

17

 Positive DC connection cable

18

 Negative DC connection cable

20

 inverter

21

 DC input

22

 AC output

23

 Insulator bushing

24

 Inverter case

25

 power pole

26

 connecting line

30

 High voltage power supply network

31

 Power grid

32

 Overhead lines

33

 path

34

 masts

40

 transformer

41

 primary

42

 secondary winding

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011053523 A1 [0003]
• DE 102009004679 B3 [0004]

Claims (12)

Photovoltaic power plant ( 1 ) for feeding electrical energy from a plurality of PV fields ( 2 ) into a power grid ( 31 ), whereby the individual PV fields ( 2 ) via DC lines ( 12 ) each with a DC input ( 21 ) of a PV field ( 2 ) associated inverter ( 20 ), the inverter ( 20 ) on the output side via a transformer ( 40 ) to the power grid ( 31 ), each PV field ( 2 ) from a plurality of module fields ( 3 ), each module field ( 3 ) a variety of PV modules ( 4 ), wherein the transformer ( 40 ) is designed as a power transformer directly in overhead lines ( 32 ) of a high voltage power grid ( 30 ), the DC lines ( 12 ) directly to module junction boxes ( 16 ) of the individual PV modules ( 4 ) or by means of electrically insulating holders ( 10 ), which were raised 5 ) on which the PV modules ( 4 ) are attached, are attached. Photovoltaic power plant ( 1 ) according to claim 1, characterized in that the DC lines ( 12 ) between the PV field ( 2 ) and the respective inverter ( 20 above ground as DC overhead lines ( 13 ) are executed. Photovoltaic power plant ( 1 ) according to claim 2, characterized in that a DC power pole ( 25 ) with the inverter housing ( 24 ) forms a unit. Photovoltaic power plant ( 1 ) according to claim 1, characterized in that the individual module fields ( 3 ) via overhead lines ( 17 . 18 ) directly or via safety devices ( 11 ) with the DC lines ( 12 ) are connected. Photovoltaic power plant ( 1 ) according to claim 1, characterized in that the transformer ( 40 ) two primary windings ( 41 ) and a secondary winding ( 42 ), wherein in each case exactly one inverter ( 20 . 20 ' ) on the output side with a primary winding ( 41 ) of the transformer ( 40 ) connected is. Photovoltaic power plant ( 1 ) according to claim 1, characterized in that the PV modules ( 4 ) within the module fields ( 3 ) are installed such that a system voltage greater than 5 kV DC with respect to the voltage difference between the DC lines ( 12 ). Photovoltaic power plant ( 1 ) according to claim 6, characterized in that the inverters ( 20 ) and the associated power transformers along a central, drivable path ( 33 ) and that also overhead lines ( 32 ) of the energy supply network ( 31 ) parallel to this path ( 33 ). Photovoltaic power plant ( 1 ) according to claim 7, characterized in that the inverters ( 20 ), the transformers ( 40 ), the overhead lines ( 32 ) and a high-voltage switchgear ( 33 ) extend perpendicular to the path on both sides. Photovoltaic power plant ( 1 ) according to claim 7, characterized in that an extension of the PV fields perpendicular to the path ( 33 ) by at least a factor of 5, preferably at least a factor of 10 greater than an extent parallel to the path ( 33 ). Inverter ( 20 ) for a photovoltaic power plant ( 1 ) according to one of the preceding claims, characterized in that the inverter ( 20 ) a housing ( 24 ), on whose upper side insulator passages ( 23 ), one against the housing ( 24 ) electrically insulating electrical connection of the above-ground DC lines ( 13 ) from the outside into the interior of the inverter ( 20 ) enable. Inverter ( 20 ) for a photovoltaic power plant ( 1 ) according to one of the preceding claims, characterized in that the inverter ( 20 ) a housing ( 24 ), on whose side walls insulator bushings ( 23 ), one against the housing ( 24 ) electrically insulating electrical connection of the above-ground DC lines ( 13 ) from the outside into the interior of the inverter ( 20 ) enable. Inverter ( 20 ) according to claim 10, characterized in that on its housing a power pole ( 25 ) is attached.

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