Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
  • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
  • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
  • H02J3/381—Dispersed generators
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
  • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
  • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
  • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
  • H02J2300/20—The dispersed energy generation being of renewable origin
  • H02J2300/22—The renewable source being solar energy
  • H02J2300/24—The renewable source being solar energy of photovoltaic origin
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Definitions

• the present invention is generally applicable to the technical field of plants for generating electrical energy starting from energy sources of renewable type and in particular has as object a photovoltaic plant for generating high-power electrical energy.
• photovoltaic plants generate electrical energy through the use of a plurality of strings of photovoltaic panels, in which each string is formed by two or more panels connected to each other in series.
• each string is connected to one or more junction boxes, which in turn are connected to one or more inverters configured for adapting the electrical parameters of the energy produced by the plant to a network for local and/or remote use.
• junction boxes typically housed one or more devices for protecting against overvoltages and/or overcurrents which would be produced in possible accidental malfunctioning of one or more strings.
• each junction box one or more converters are usually housed that are configured for controlling and modifying the electrical magnitudes present in the output terminals of each string.
• the converters are also configured for supplying the inverters an electric voltage signal greater than that the voltage present in the single output terminals of the strings and with overall power substantially equal to the sum of the electric power supplied by each string connected thereto.
• the inverters comprise a logical control unit connected to each converter and adapted to control the single string of panels as a function of the electric power instantaneously requested by the net.
• the logical unit controls the functioning of the single string in a manner such that the same constantly generates the maximum electric power or, alternatively, it can disconnect the string from the plant for safety grounds or in case of malfunctioning.
• One drawback of such solution is represented by the fact that the joint housing of the logical control unit inside the inverter considerably limits the flexibility of the plant and renders the inverters especially costly.
• the logical control unit is difficult to access, both by a user who intends to monitor the functioning status of the plant and by an operator who must execute maintenance operations on the same.
• the power circuits of the inverter require large spaces for their housing inside the casing and for such reason the spaces reserved to the logical unit are particularly limited.
• the reduced size of the logical control unit makes a particularly accurate design of its circuits necessary, and consequently introduces limitations on the number of the electrical and electronic functions that the same can execute on the converters and on the strings.
• the housing of the logical control unit inside the inverter makes the possible substitution of the single device particularly costly, since according to the failure type, it is often necessary to substitute the inverter or the logical control unit as well that is not damaged.
• the housing of the logical control unit and the inverter in a single structure forces the temporary disconnection of the inverter from the plant, even when maintenance operations are carried out on the logical control unit alone.
• US2010/139734 on which the preamble of the claim 1 is based, discloses a method and a system to make a photovoltaic plant safe during emergency or maintenance through an automatic and remote control of the disconnection of one or more photovoltaic panels with a sentinel unit.
• US2008/0097655 discloses a system and a method for supplying a local distribution of electric energy with a high DC voltage bus.
• WO03/098703 deals with a photovoltaic plant having a control circuit of the photovoltaic panels adapted to reduce the energetic losses of the plant making not all the panels work in a maximum power condition (MPPT).
• MPPT maximum power condition
• the object of the present invention is to overcome the drawbacks of the prior art mentioned above, by providing a high-power photovoltaic plant that is particularly efficient and relatively inexpensive.
• a particular object of the finding is to provide a photovoltaic plant that allows a particularly flexible installation of the devices that constitute it in such a manner to facilitate the access of a user and/or operator, particularly in maintenance operations.
• a further object of the present finding is to provide a photovoltaic plant that allows reducing the design and producing costs of the inverters.
• a further object of the present finding is to provide a photovoltaic plant that allows carrying out a wide set of controls and functions on the converters and on the strings.
• a further object of the present finding is to provide a photovoltaic plant that allows maintaining high functionality, even during maintenance operations.
• a high power photovoltaic plant in accordance with claim 1 , comprising a plurality of strings, each having two or more photovoltaic panels connected in series, at least one junction box connected to one or more strings of said plurality wherein each junction box houses internally thereof at least one current converter designed to vary the power energy generated by each single string and a peripheral control unit for controlling said converter, at least one inverter electrically connected to each converter for injecting into the net the power energy produced by the strings and a central control unit connected to said at least one inverter for controlling the energy generated by said plurality of strings and to each of said peripheral units for controlling the electric power in output from each of said junction boxes.
• the plant is characterized in that said central control unit comprises sensor means associated to said at least one inverter to detect the electric parameter associated of the energy injected into the net and to control said converters, said central control unit being housed into a casing different and spatially spaced apart with respect to each of said junction boxes and said at least one inverter to allow separate and independent operation on each between said central control unit and said at least one inverter.
• the photovoltaic plant will allow generating electrical energy with high efficiency and will provide for an easy installation and easy maintenance.
• FIG. 1 is a schematic block diagram of a photovoltaic plant according to the finding
• FIG. 2 is a schematic view of the plant schematized in Fig. 1 , with several details in section.
• FIG. 3 is a perspective view of a first detail of a plant according to the finding
• FIG. 4 is a sectioned front view of the first detail of Fig. 3;
• FIG. 5 is a sectioned front view of a second detail of a plant according to the finding.
• FIG. 6 is a front view of one element of the detail of Fig. 5.
• a high-power photovoltaic plant indicated with 1 overall, will be configured for producing and injecting electrical energy into an electrical network R for local and/or remote distribution.
• the plant 1 can be configured to be installed on particularly wide and regular surfaces, such as for example large lots of land or photovoltaic parks, and on irregular, smaller surfaces such as the roofs of one or more buildings.
• the plant 1 comprises a plurality of strings 2, 2', 2", ... each having two or more photovoltaic panels 3, 3', 3", ... connected in series and at least one junction box 4, 4', 4",... connected to one or more strings 2, 2', 2",....
• Each junction box 4, 4', 4",... houses internally at least one current converter 5, 5', 5"... designed to vary the power energy generated by each single string 2, 2', 2",... and a peripheral control unit 6, 6', 6",... for controlling the converter 5, 5', 5",....
• the plant 1 comprises at least one inverter 7, 7', 7", ... electrically connected to each converter 5, 5', 5",... for injecting into the net the power energy produced by the strings 2, 2', 2",... and a central control unit 8 connected to at least one inverter 7, 7', 7",... for controlling the electrical parameters of the total energy injected into the net R, and to each of the peripheral units 6, 6', 6",... for controlling the electric power in output from each of the junction boxes 4, 4', 4",....
• the central control unit 8 is housed in a casing 9 different and spatially spaced apart with respect to each of the junction boxes 4, 4', 4",... and from the inverters 7, 7', 7"
• the central control unit 8 can be arranged in a different environment with respect to that where the inverters 7, 7', 7" are housed, in a manner such that the same can be easily accessible by an operator.
• the plant 1 has fifteen strings 2, 2', 2", ... of photovoltaic panels 3, 3', 3", ... and three junction boxes 4, 4', 4".
• junction box 4, 4', 4" is respectively connected to separate groups, each formed by five strings 2, 2', 2",...
• Such configuration is merely exemplifying and the plant 1 can provide for a total number of strings 2, 2', 2", ... and a total number of junction boxes 4, 4', 4", ... different from those indicated in the figures without departing from the protective scope of the finding.
• each junction box 4, 4', 4" can be the same for all the boxes 4, 4', 4" present in the plant 1 , as is illustrated in the figures, or they can differ between two or more junction boxes 4, 4', 4".
• each junction box 4, 4', 4" can be connected to a maximum of six strings 2, 2', 2", ... of panels 3, 3', 3",... in a manner such that the same has reduced size and is easily connectable and/or disconnectable to the plant 1 if maintenance operations must be carried out.
• each junction box 4, 4', 4" can have an electrical connection 10, 10', 10" adapted to connect it in parallel to the inverters 7, 7', 7" in a manner such that the same receive electric power in input that is substantially equal to the sum of the electric power present at the output of each box 4, 4', 4".
• peripheral control units 6, 6', 6" can be integrated inside the respective converter 5, 5', 5" or, alternatively, they can be distinct and separate from the same and connected through a dedicated electrical connection, not illustrated in the figures.
• the plurality of strings 2, 2', 2",... can be sized for producing electrical energy with predetermined parameters and with power greater than or equal to 20 kilowatts.
• the maximum electric power produced by the plant 1 can be sized starting from the total number of strings 2, 2', 2",... present in the same and from the total number of photovoltaic panels 3, 3', 3",... present in each string 2, 2', 2",... and connected to each other in series.
• the plant 1 can comprise strings 2, 2', 2", ... of photovoltaic panels having the same number of photovoltaic panels 3, 3', 3" with respect to each other, ... connected in series or, alternatively, having a different number of photovoltaic panels 2, 2', 2",... connected in series.
• the strings 2, 2', 2", ... can be sized for producing electric power comprised between several dozen kilowatts and a few megawatts.
• each converter 5, 5', 5" can be adapted to draw the maximum electric power available from each string 2, 2', 2",... and to transfer such power to a corresponding inverter 7, 7', 7".
• each converter 5, 5', 5" can be configured for simultaneously drawing the maximum electric power from the respective strings 2, 2', 2",... during the functioning of the plant 1.
• each converter 5, 5', 5" will be able to select at least one string 2, 2', 2",... of the corresponding group from which the maximum electric power is drawn.
• Each converter 5, 5', 5" can also be configured to supply, to the corresponding inverter 7, 7', 7", electrical energy with predetermined voltage greater than that produced by each string 2, 2', 2", ...
• each converter 5, 5', 5" will increase the electric voltage present at the output terminals 11 , 12; 11 ', 12', ... of the single string 2, 2', 2", ... in a manner such that the electric current circulated therein can have a variable value less than a predetermined maximum value.
• the increase the electric voltage present at the output terminals 11 , 12; 11 ', 12';... of the strings 2, 2', 2" can also allow the use in the electrical connections 10, 10', 10", ... of electrical cables having relatively reduced section.
• the peripheral control units 6, 6', 6" can comprise respective first elaboration means 13, 13', 13" adapted to detect the electrical parameters of each string 2, 2', 2" in order to process them and generate the first data D-i to send to the central control unit 8.
• the first elaboration means 13, 13', 13" comprise a first processor 14, 14', 14" configured for processing the electrical signals coming from the respective converter 5, 5', 5" and generating first data D-i of digital type.
• first elaboration means 13, 13', 13" comprise a memory portion 15, 15', 15",... adapted to store such first data D-i .
• the first data D-i can contain information relative to electrical parameters of each string 2, 2', 2", for instance, such as the electric voltage present at the output terminals 11 , 12; 11 ', 12', the current circulating in the same and the instantaneous power supplied by the string 2, 2', 2".
• first data D-i can also contain information relative to quantities associated with the string 2, 2', 2", which are not electrical type, such as the working temperature or other functioning quantities.
• the first elaboration means 13, 13', 13" can be configured for generating and storing the first data D-i periodically, at regular and predetermined time intervals, in a manner such to maintain the information contained therein relatively updated during the functioning of the plant 1.
• the central control unit 8 can comprise second elaboration means 16 adapted to respectively receive and process the first data D-i and the total electrical parameters of the energy injected in the network R in order to generate second data D 2 to send to the first elaboration means 13, 13', 13" and control the functioning of the converters 5, 5', 5".
• the second elaboration means 16 can comprise at least one second processor 17 adapted to receive and process the first digital data D-i and the electrical parameters associated with the energy injected in the net R and generate second data D 2 of digital type adapted to be detected and stored by the first elaboration means 13, 13', 13".
• the electrical parameters associated with the energy injected in the net R can be detected by sensor means 18 connected to the output of the inverters 7, 7', 7" and which can comprise analog-digital conversion means, not illustrated in the figures, adapted for transforming such electrical parameters into a numeric signal recognizable by the second elaboration means 16.
• the sensor means 18 can be configured for detecting the total electrical parameters of the energy injected in the net R at periodic and predetermined time intervals.
• the time instants in which the first elaboration means 13, 13', 13" generate the first data D-i can be substantially coinciding with the time instants in which the sensor means 18 detect and send the total electrical parameters of the energy to the second elaboration means 16.
• the second elaboration means 16 can receive and process the first data D-i and the electrical parameters detected by the sensor means 18 in a synchronized manner in order to produce second data D 2 given to the actual instantaneous functioning of the plant 1.
• the central control unit 8 can comprise a memory circuit 19 adapted to store identification data D id and reference data D rif for each string 2, 2', 2",... in addition to the first D-i and second D 2 data and the electrical parameters of string 2, 2', 2", ... and total electrical parameters.
• the memory circuit 19 can be connected to the second processor 17 and can also be configured for containing one or more programming routines of the same and for storing all the temporary and volatile data generated thereby during processing, such data necessary for producing the second data D 2 .
• the central control unit 8 can comprise display means, not illustrated in the figure, adapted to display information relative to the first D-i and second D 2 data and to the electrical parameters associated with each string 2, 2', 2", ... or with the energy injected in the network R.
• the second processing means 16 can also comprise interface means, not illustrated in the figures, actuatable by a user, e.g. of alphanumeric keyboard type or the like, in a manner such to allow the selection of the displayed information by the display means.
• the interface means can also be actuated by a user to modify the programming routines of the second processor 17 or the identification data Did present in the memory circuit 19.
• the peripheral electronic units 6, 6', 6" can be programmed to selectively disconnect each string 2, 2', 2",... from the respective converter 5, 5', 5" in response to the second data D 2 , by short-circuiting the string terminals 11 , 12; 11 ', 12' ;... in a manner so to set at zero the output voltage and be able to intervene on the string under safe conditions.
• the disconnection of the strings 2, 2', 2",... from the plant 1 can be controlled by the second elaboration means 16 and can occur when the first data D-i associated with the same is different from the reference data D rif associated with the same and stored in the memory circuit 19.
• each peripheral control unit 6, 6', 6" can be programmed for selectively sending a predetermined impulsive reference signal to each single string 2, 2', 2", ... and for controlling the electrical response to the reference signal in a manner so as to detect, by means of the central control unit 8, the possible removal and/or theft of one or more panels 3, 3', 3", ... from each string 2, 2', 2", ...
• the electrical response to the reference signal can be a signal associated with the current present at the terminals of 11 , 12; 11 ', 12'; ... of the strings 2, 2', 2"
• the second elaboration means 16 can detect such signal and generate first data D-i containing information relative to the total electrical resistance of the string 2, 2', 2",....
• the second elaboration means 16 can be configured for detecting the first data D-i containing information associated with the string electrical resistance and comparing the same with the reference data D rif of the same string stored in the memory circuit 19.
• the central control unit 8 can signal a possible removal or disconnection of one or more photovoltaic panels 3, 3', 3",... if the first data D-i comprises information associated with a value of the string electrical resistance 2, 2', 2",... lower than the value present in the reference data D rif .
• the central control unit 8 can be configured for containing reference data D rif associated with the theoretical maximum power supplied by each string 2, 2', 2",... present in the plant 1.
• the central control unit 8 can send second data D 2 to the peripheral control unit 6, 6', 6" adapted to achieve the temporary disconnection of the string 2, 2', 2",... from the plant 1.
• the peripheral control unit 6, 6', 6" can control the respective converter 5, 5', 5" by achieving, on the string 2, 2', 2",... a complete cycle of detection of the produced power and by detecting the new electrical parameters corresponding with the supply of the maximum instantaneous power associated with the string 2, 2', 2", ...
• the string 2, 2', 2", ... can be connected to the plant 1 and the peripheral control unit 6, 6', 6" can control the respective converter 5, 5', 5" in a manner such that the string 2, 2', 2",... supplies a power substantially equal to the maximum power detected during the detection cycle.
• reference data D rif can be updated in accordance with the new electrical parameters detected during the detection cycle.
• each junction box 4, 4', 4" can be electrically supplied only by the strings 2, 2', 2",... connected thereto.
• each converter 5, 5', 5" and the respective peripheral control unit 6, 6', 6" can be configured to be activated when the strings 2, 2', 2",... connected to the junction box 4, 4', 4" produce an electric power greater than a predetermined minimum value.
• peripheral control unit 6, 6', 6" can send to the central control unit 8 first data D-i containing the value of the instantaneous power generated by the strings 2, 2', 2", ...
• the central control unit 8 will receive and process the first data D-i by comparing the value of the power generated by the strings 2, 2', 2", ... with that present in the reference data D rif and associated with the minimum value of electric power necessary for actuating the inverters 7, 7', 7".
• the plant 1 will start operating by injecting electric power in the network R.
• each peripheral control unit 6, 6', 6" can be configured for periodically detecting, with a predetermined detection frequency, the values of the voltage and electric current present at the output terminals 11 , 12; 11 ', 12', ... of each string 2, 2', 2".
• the voltage values and/or current values comprise oscillatory overvoltage and/or overcurrent components such to indicate the presence of one or more electrical arcs present in the electrical connections of one or more strings 2, 2', 2",...
• the elaboration means 13, 13', 13", ... can selectively disconnect the string from the corresponding converter 5, 5', 5" and send, to the central control unit 8, first data D-i containing an alarm signal.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Control Of Electrical Variables (AREA)
• Photovoltaic Devices (AREA)
• Hybrid Cells (AREA)
• Inverter Devices (AREA)
• Supply And Distribution Of Alternating Current (AREA)

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• 2011
  • 2011-04-29 IT IT000112A patent/ITVI20110112A1/it unknown
• 2012
  • 2012-04-27 CN CN201280027355.9A patent/CN103703644A/zh active Pending
  • 2012-04-27 EP EP12726190.7A patent/EP2710702A1/en not_active Withdrawn
  • 2012-04-27 WO PCT/IB2012/052122 patent/WO2012147058A1/en active Application Filing

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