WO2012147058A1

WO2012147058A1 - High power photovoltaic plant for generating energy

Info

Publication number: WO2012147058A1
Application number: PCT/IB2012/052122
Authority: WO
Inventors: Ezio Bertotto; Simone GRIGGIO; Giancarlo VERLATO
Original assignee: Reel S.R.L.
Priority date: 2011-04-29
Filing date: 2012-04-27
Publication date: 2012-11-01
Also published as: EP2710702A1; ITVI20110112A1; CN103703644A

Abstract

A photovoltaic plant for comprises a plurality of strings (2, 2', 2",...) each having two or more photovoltaic panels (3, 3', 3",...) connected in series, at least one junction box (4, 4', 4",...) connected to one or more strings (2, 2', 2",...) and housing at least one current converter (5, 5', 5",...) 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",...); at least one inverter (7, 7', 7",...) connected to each converter (5, 5', 5",...) for injecting into the net (R) the electrical energy produced by the strings (2, 2', 2",...), a central control unit (8) connected to the inverter (7, 7', 7",...) to control the energy generate by said plurality of strings (2, 2', 2",...) and to each periphery unit (6, 6', 6",...) to control the output electric power from each junction box (4, 4', 4",...). The central control unit (8) comprises sensor means (18) associated with the inverter (7, 7', 7",...) to detect the electric parameters associated with the energy injected into the net (R) and to control the converters (5, 5', 5",...), the central control unit (8) being housed into a casing (9) different and spatially spaced apart with respect to each junction box (4, 4', 4",...) and from the inverter (7, 7', 7",...) to allow separate and independent operation on each between the central control unit (8) and at least one inverter (7, 7', 7",...).

Description

HIGH POWER PHOTOVOLTAIC PLANT FOR GENERATING ENERGY

Field of application

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.

State of the Art

As is known, 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.

The output terminals of each string are 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.

Typically, inside one or more junction boxes are 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.

In addition, inside 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.

According to a known configuration, 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.

In this manner, 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.

Indeed, in this case 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.

In addition, 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.

Consequently, 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.

In addition, 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.

Finally, 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).

Nobody of those prior documents clearly shows at least one current converter adapted to vary the electric energy generated by each single string and a system for detecting parameters of the total energy injected into the net in such a manner to control the operation of the converter.

Presentation of the invention

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.

Such objectives, as well as others which will appear clearer below, are achieved by 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.

Due to this particular configuration of the finding, the photovoltaic plant will allow generating electrical energy with high efficiency and will provide for an easy installation and easy maintenance.

Advantageous embodiments of the finding are obtained in accordance with the dependent claims.

Brief description of the drawings

Further characteristics and advantages of the finding will be clearer in light of the detailed description of a preferred but not exclusive embodiment of a photovoltaic plant for producing electrical energy, illustrated as a non- limiting example with the aid of the drawing table set, in which:

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.

Detailed description of a preferred embodiment With reference to the mentioned figures, 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.

In a known manner, 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.

As illustrated in Fig. 1 , the plant 1 according to the finding 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",....

In addition, 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",....

According to a particular characteristic of the finding, 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"

In this manner, it will be possible to allow operator access to the central control unit 8 and to the inverters 7, 7', 7" independently from each other.

In addition, in this manner, it will be possible to separately and independently intervene on each between the central control unit 8 and the inverters 7, 7', 7".

Advantageously, 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.

In the configuration of the finding illustrated in Fig. 1 , the plant 1 has fifteen strings 2, 2', 2", ... of photovoltaic panels 3, 3', 3", ... and three junction boxes 4, 4', 4".

Each 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.

In addition, the number of strings 2, 2', 2", ... connected to 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".

Suitably, according to a preferred but not exclusive configuration of the finding, 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.

In addition, as is illustrated in Figs. 1 and 2, the output of 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".

In addition, the 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.

Suitably, 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.

Typically, 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.

Advantageously, 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.

Typically, the strings 2, 2', 2", ... can be sized for producing electric power comprised between several dozen kilowatts and a few megawatts.

Suitably, 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".

In addition, 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.

Alternatively, 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", ...

In this manner, 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.

One such configuration will allow reducing the losses due to Joule effect of the electrical connections 10, 10', 10", ... which connect each junction box 4, 4', 4" to the inverters 7, 7', 7".

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.

Suitably, 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.

As illustrated in Fig. 4, 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.

In addition, the first elaboration means 13, 13', 13" comprise a memory portion 15, 15', 15",... adapted to store such first data D-i .

According a first configuration of the finding, 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".

In addition, the 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.

Advantageously, 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.

In addition, 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 D₂ 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 D₂ 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.

In addition, 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.

Advantageously, 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.

In this manner, 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 D₂ given to the actual instantaneous functioning of the plant 1.

In addition, as illustrated in Fig. 6, 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 D₂ 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 D₂.

Suitably, 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 D₂ data and to the electrical parameters associated with each string 2, 2', 2", ... or with the energy injected in the network R.

In addition, 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.

Suitably, 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 D₂, 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.

In this manner, it will be possible to detect possible malfunctioning that occurred at one or more strings 2, 2', 2", ... and to operate in a manner so as to temporarily disconnect the strings from the plant 1 , making them accessible and safe for the maintenance operations.

In addition, 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", ...

According to a particularly advantageous aspect of the finding, 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"

In this manner, 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.

In this manner, 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.

In addition, 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.

Indeed, if one or more panels 3, 3', 3",... of a string 2, 2', 2",... should be partially covered or be shaded by objects placed close to the plant 1 , the instantaneous electric power supplied by the corresponding string 2, 2', 2",... will be less than the reference value present in the reference data D_rif.

In addition, such instantaneous electric power supplied in such conditions by the string 2, 2', 2",... might not coincide with the maximum instantaneous power that the same could supply in the same cover or shade conditions.

For such purpose, if the first data D-i sent by the peripheral control unit 6, 6', 6", ... contains information associated with the power generated by one or more strings 2, 2', 2",.-- not corresponding with the information present in the reference data D_rif, the central control unit 8 can send second data D₂ to the peripheral control unit 6, 6', 6" adapted to achieve the temporary disconnection of the string 2, 2', 2",... from the plant 1.

During such disconnection, 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", ...

Subsequently, 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.

In addition, the reference data D_rif can be updated in accordance with the new electrical parameters detected during the detection cycle.

According to a particularly advantageous aspect of the finding, each junction box 4, 4', 4" can be electrically supplied only by the strings 2, 2', 2",... connected thereto.

In this manner, 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.

Following its activation, the 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".

If the value of the power generated by the strings 2, 2', 2",... exceeds such value, the plant 1 will start operating by injecting electric power in the network R.

According to this configuration, one will avoid supplying power to the junction boxes 4, 4', 4", absorbing energy from the net R, and additionally the plant 1 will autonomously start operating when it is capable of producing energy, in this manner allowing the increase of its overall efficiency.

Suitably, the elaboration means 13, 13', 13" of 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".

Thus, if 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.

The photovoltaic plant according to the finding is susceptible to numerous modifications and variants, all falling within the inventive concept expressed in the enclosed claims. All details can be substituted by other technically equivalent elements, and the materials can be different according to needs, without departing from the scope of the finding.

Even if the photovoltaic plant was described with particular reference to the enclosed figures, the reference numbers are used for improving the comprehension of the finding and do not constitute any limitation of the claimed protective scope.

Claims

1 . A photovoltaic plant for generating and injecting high power energy into a local and/or remote distribution net (R), wherein the plant comprises:

- a plurality of strings (2, 2', 2", ...) each having two or more photovoltaic panels (3, 3', 3", ...) connected in series;

- at least one junction box (4, 4', 4", ...) connected to one or more strings (2, 2', 2", ...) of said plurality, wherein each junction box (4, 4', 4", ...) houses internally thereof at least one current converter (5, 5', 5", ...) adapted to vary the power energy generated by each single string (2, 2', 2", ...) and a peripheral control unit (6, 6', 6", ...) for controlling said converter (5, 5', 5", ...);

- at least one inverter (7, 7', 7", ...) electrically connected to each converter (5, 5', 5", ...) for injecting into the net (R) the power energy produced by the strings (2, 2', 2", ...);

- a central control unit (8) connected to said at least one inverter

(7, 7', 7", ...) for controlling the energy generate by said plurality of strings (2, 2', 2", ...) and to each of said peripheral units (6, 6', 6", ...) for controlling the output electric power from each of said junction boxes (4, 4', 4", ...);

characterized in that said central control unit (8) comprises sensor means (18) associated with said at least one inverter (7, 7', 7", ...) to detect the electric parameters associated with the energy injected into the net (R) and to control said converters (5, 5', 5", ...), said central control unit (8) being housed into a casing (9) different and spatially spaced apart with respect to each of said junction boxes (4, 4', 4"', ...) and said to said at least one inverter (7, 7', 7", ...) to allow separate and independent operation on each between said central control unit (8) and said at least one inverter (7, 7', 7", ..)-

2. Plant as claimed in claim 1 , characterized in that said plurality of strings (2, 2', 2", ...) is sized to produce power energy with predetermined parameters and with electric power higher or equal to 20 kilowatt.

3. Plant as claimed in claim 1 or 2, characterized in that said converter (5, 5', 5", ...) is designed to draw from each string (2, 2', 2", ...) the available maximum electric power and transfer it to said at least one inverter (7, 7', 7", ...).

4. Plant as claimed in any preceding claim, characterized in that said casing (9) is designed to be placed in a different environment with respect of that of said least one inverter (7, 7', 7", ...).

5. Plant as claimed in any preceding claim, characterized in that said converter (5, 5', 5", ...) is designed to provide said at least one inverter (7, 7', 7", ...) with a power energy having a predetermined voltage higher than that produced by each string (2, 2', 2", ...).

6. Plant as claimed in any preceding claims, characterized in that said at least one peripheral control unit (6, 6', 6", ...) comprises first elaboration means (1 3, 1 3', 1 3", ...) adapted to detect the electric parameters of each string (2, 2', 2", ...) for processing them and generating first data (D-i) to be sent toward said central control unit (8).

7. Plant as claimed in claim 6, characterized in that said central control unit (8) comprises second elaboration means (16) designed to receive and process respectively, said first data (D-i) and said total electric parameters of the power energy fed into the net (R) for generating second data (D₂) to be sent toward said first elaboration means (1 3, 1 3', 1 3", ...) and for controlling the operation of said converter (5, 5', 5", ...).

8. Plant as claimed in claim 7, characterized in that said central control unit (8) comprises a memory circuit (1 9) designed to memorize identification data (D_id) and reference data (D_rif) of each string (2, 2', 2", ...), said first (D-,) and said second (D₂) data and said string (2, 2', 2", ...) electric parameter and total electric parameters.

9. Plant as claimed in claim 8, characterized in that each peripheral control unit (6, 6', 6", ...) is programmed to selectively disconnect each string (2, 2', 2", ...) from said converter (5, 5, 5", ...) in response to said second data (D₂) for short-circuiting the terminals (1 1 , 12; 1 1 ', 1 2', ...) in such a manner to zero set the output voltage and intervening thereon in a safety conditions.

1 0. Plant as claimed in any claim 6 to 8, characterized in that each peripheral control unit (6, 6', 6", ...) is programmed to selectively send toward each single string (2, 2', 2", ...) a predetermined reference impulsive signal and for controlling the electric response to said reference signal for detecting through said central control unit (8) the possible removal and/or theft of one or more panels (3, 3', 3", ...) from each string (2, 2', 2", ...).