Photovoltaic facility architecture

Abstract

A photovoltaic system comprising an output inverter (11) for connection to a third party network (1000), and at least one string, each string comprising at least one module (1) of tandem photovoltaic cells, each module having a first and a second pair of connectors. The modules of the string are connected in series by means of their first pair of connectors. A plurality of strings are connected to the output inverter in parallel with each other by means of connectors among the first pair of connectors of each string. A plurality of modules are connected in parallel via their second pair of connectors to form a first group, the first group being connected upstream of the output inverter via the second pair of connectors to a second group of modules, the second group of modules consisting of a single module or a series of modules connected in series with each other via their first pair of connectors.

Description

Technical Field

[0001] The invention belongs to the field of energy generation by means of a set of at least one photovoltaic module. Background Art

[0002] Photovoltaic modules (or panels) include a number of photovoltaic cells, for example 60 or 72 cells. Recently, a new type of photovoltaic cell has emerged: tandem cells. The theoretical efficiency of tandem cells exceeds 30%, while conventional industrial PERC cells (PERC stands for "Passivated Emitter and Rear Cell") are only 22%.

[0003] Tandem cells consist of a stack of various semiconductor material layers, each PN junction forming a subcell and thus exhibiting different properties. The optimal operating conditions for energy conversion vary depending on the properties of the layers. In other words, tandem cells allow the cell as a whole to be effective under a wider variety of operating conditions, making the facility more flexible in terms of weather conditions (specifically, spectral range, lighting intensity, and temperature).

[0004] When there are several types of PN junctions, each cell may have two terminals (or electrical terminals). The sub-cells are connected in series. These cells can then be connected to the rest of the facility in a conventional manner, replacing conventional cells such as PERC cells. However, in practice, the efficiency of each cell is limited by the lowest current of all junctions. In other cases, each cell may have a number of terminals equal to twice the number of junction types. For example, each cell has four independent electrical terminals (one pair for each junction). As indicated in US 2017 / 0040557, and like other elements of a photovoltaic facility, it is theoretically possible to associate a converter with each sub-cell. This makes it possible to decouple the operation of the sub-cells and therefore make their efficiencies independent of each other. In practice, it is still necessary to (at least) double the other components of the facility (connectors, wiring, inverters, etc.), which significantly increases the risk of failure and cost. In addition, the converters are bulky and sensitive to heat due to sunlight exposure, which further reduces the practical significance of this system in practice. Summary of the invention

[0005] The present disclosure improves this situation.

[0006] A photovoltaic system is provided, comprising an output inverter for connecting to a third party network, and at least one string, each string comprising at least one module of tandem photovoltaic cells, each module having a first pair of connectors and a second pair of connectors,

[0007] The modules of the string are connected in series with each other by means of their first pair of connectors, and a plurality of strings are connected in parallel with each other to the output inverter by means of connectors among the first pair of connectors of each string,

[0008] A plurality of modules are further connected in parallel via their second pair of connectors to form a first group, the first group being further connected to a second group of modules via the second pair of connectors upstream of the output inverter, the second group of modules consisting of a single module or a series of modules connected in series to each other via their first pair of connectors.

[0009] The features set out in the following paragraphs may be optionally implemented. They may be implemented independently of each other or in combination with each other:

[0010] Each module comprises a converter. Each first pair of connectors of the module is connected to a second pair of connectors of the module by means of the converter. The converter is controlled by means of a maximum power point tracker algorithm MPPT so that the power deducted via the second pair of connectors is independent of the operating conditions of the first pair of connectors.

[0011] The converter is mounted on the face of the module opposite to the operating face of the photovoltaic cells, so that the converter is protected from sunlight.

[0012] The first group and the second group each comprise a different number of modules, so that the ratio between these two numbers can be chosen to correspond at least approximately to the ratio of the unit operating voltages or currents of each of the two subcells constituting the tandem photovoltaic cell.

[0013] The first group and the second group comprise identical modules. The modules of the string are assembled in series via their first pair of connectors on the one hand and their second pair of connectors on the other hand. Each string further comprises a converter arranged in series or in parallel between the string formed via the first pair of connectors and the string formed via the second pair of connectors. Each converter is controlled by means of a maximum power point tracker algorithm MPPT so that the power deducted via the second pair of connectors is independent of the operating conditions of the first pair of connectors.

[0014] The converter arranged in series or in parallel between the string formed via the first pair of connectors and the string formed via the second pair of connectors is composed of two power switches.

[0015] The output inverter comprises a modular multi-input inverter controlled by means of an independent maximum power point MPP tracker algorithm on each input, making the power deducted via the second pair of connectors independent of the operating conditions of the first pair of connectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features, details and advantages of the present invention will become apparent after reading the following detailed description and after analyzing the accompanying drawings, in which:

[0017] Figure 1

[0018] [ Figure 1] shows that the current or power characteristics of a conventional module vary with voltage for different operating conditions.

[0019] Figure 2

[0020] [ Figure 2 ] shows a string of two-terminal tandem photovoltaic cells.

[0021] Figure 3

[0022] [ Figure 3 ] shows the details of a two-terminal tandem photovoltaic cell.

[0023] Figure 4

[0024] [ Figure 4 ] shows a string of four-terminal tandem photovoltaic cells.

[0025] Figure 5

[0026] [ Figure 5 ] shows details of a four-terminal tandem photovoltaic cell.

[0027] Figure 6

[0028] [ Figure 6 ] shows a string of three-terminal stacked photovoltaic cells.

[0029] Figure 7

[0030] [ Figure 7 ] shows the details of a three-terminal tandem photovoltaic cell.

[0031] Figure 8

[0032] [ Figure 8 ] indicates a two-terminal photovoltaic module.

[0033] Fig. 9

[0034] [ Fig. 9 ] shows that the characteristics of the current of the module of the previous figure vary with voltage.

[0035] Fig.10

[0036] [ Fig.10 ] indicates a four-terminal photovoltaic module.

[0037] Fig.11

[0038] [ Fig.11 ] shows that the characteristics of the current of the module of the previous figure vary with voltage.

[0039] Fig.12

[0040] [ Fig.12 ] represents a photovoltaic system with a two-terminal module.

[0041] Fig.13

[0042] [ Fig.13 ] indicates a PV system with a four-terminal module (dual connector, cable and inverter).

[0043] Fig.14

[0044] [ Fig.14 ] indicates a four-terminal photovoltaic module whose output is connected in series.

[0045] Fig.15

[0046] [ Fig.15 ] shows that the characteristics of the current of the module of the previous figure vary with voltage.

[0047] Fig.16

[0048] [ Fig.16 ] indicates that the output of a four-terminal photovoltaic module is connected in parallel.

[0049] Fig.17

[0050] [ Fig.17 ] shows that the characteristics of the current of the module of the previous figure vary with voltage.

[0051] Fig.18

[0052] [ Fig.18 ] represents an output-connected four-terminal photovoltaic module according to an example of embodiment A.

[0053] Fig.19

[0054] [ Fig.19 ] shows that the characteristics of the current of the module of the previous figure vary with voltage.

[0055] Fig. 20

[0056] [ Fig. 20 ] represents a photovoltaic system with four-terminal modules with connected outputs according to an example of embodiment B.

[0057] Fig.21

[0058] [ Fig.21] represents a photovoltaic system with four-terminal modules with connected outputs according to an example of embodiment C1.

[0059] Fig. 22

[0060] [ Fig. 22 ] represents a photovoltaic system with four-terminal modules with connected outputs according to an example of embodiment C2.

[0061] Fig.23

[0062] [ Fig.23 ] represents a photovoltaic system with four-terminal modules with connected outputs according to an example of embodiment D.

[0063] The drawings and the following description mainly contain elements that are specific in nature. Therefore, they serve not only to provide a better understanding of the present disclosure but also to facilitate the definition of the present disclosure when appropriate.

[0064] In the following, we consider:

[0065] - "system" means a photovoltaic facility as a whole, such as a power plant consisting of multiple photovoltaic "modules";

[0066] - "Module" means an object commonly referred to as a photovoltaic panel and comprising a plurality of photovoltaic "cells" (here tandem cells; typically 60 or 72 cells per module);

[0067] - a tandem "cell" means an assembly of a plurality of "subcells" usually in the form of a stack of layers;

[0068] - "Subcell" refers to a combination of two layers of different materials that form a PN junction and that give rise to the physical phenomenon of electricity generation under the effect of light.

[0069] Physical Principles

[0070] To achieve good performance of a photovoltaic system (usually a power station or "solar farm"), the efficiency of the basic components is critical. Tandem cells theoretically have good efficiency.

[0071] Specifically, just like conventional (non-tandem) photovoltaic cells, the characteristics (voltage and current) of the subcells are different from each other. Each subcell, each cell, each photovoltaic module, each string and each system has a theoretical maximum power point (or MPP) defined by the current and voltage operating conditions. The MPP of different components will vary. The MPP depends on:

[0072] - the intrinsic properties of the components, which may differ even between two theoretically identical models due to manufacturing conditions and which are deliberately sought to differ between the two subcells of a tandem cell,

[0073] -aging,

[0074] -pollute,

[0075] - lighting (exposed to daylight or in the shade),

[0076] -temperature.

[0077] Now refer to [ Figure 1 ]. As an example, it shows the dependence of current, voltage, power, temperature and illumination characteristics of a module based on non-tandem cells (one PN junction per cell). Generally speaking, it can be considered that light irradiation mainly affects the generated current, and the voltage changes are minimal in comparison. In contrast, the temperature has a greater impact on the voltage - the difference in current is small.

[0078] In conventional installations, the characteristics of certain elements are managed via inverters controlled by means of an MPPT (“Maximum Power Point Tracker”) algorithm, which makes it possible to approach the maximum power point as closely as possible by imposing a current or a voltage.

[0079] Replacing conventional cells with tandem cells in existing systems limits the efficiency of each tandem cell to the lowest efficiency of its constituent subcells. Similarly, this limits the efficiency of each module of the tandem cell to the lowest efficiency of its constituent cells. Thereby, the actual overall efficiency of the system is limited. When the power of the spectrum is reduced, or when the average photon energy (or APE) is low (e.g., less than 1.78 eV, which corresponds to winter sunshine conditions common in mainland France), the difference between the actual efficiency and the theoretical efficiency degrades more.

[0080] Combined with the use of tandem cells, it is therefore preferred to exploit the energy available in each subcell, independently of weather conditions, by decoupling the heterogeneous subcells from each other. Optimizing the immediate environment of the cell is therefore also important for good energy performance: the entire conversion string must be adapted in order to maintain the efficiency gains that tandem cells are able to achieve, from the PN layer of the subcell to the node connected to the transmission or distribution network.

[0081] Each element of the system has its own MPP at each moment. It is therefore possible to provide a controlled converter which allows to vary the operating conditions (current and voltage) of the elements associated therewith.

[0082] In theory, it is possible to operate each element under individually controlled current and voltage conditions by equipping each element with an inverter controlled by means of an MPPT algorithm. However, the number of optimizers suitable for high power conditions and the nature of the optimizers make the installation and maintenance costs prohibitive, especially for high power facilities. DETAILED DESCRIPTION

[0083] In the following, a photovoltaic cell is a tandem cell, which means that it comprises a plurality of subcells (two subcells in the example shown). Within a tandem cell (referenced 1 below), the two subcells are of different physical types, which gives them different behaviors and properties under the effects of light. Therefore, when operating under similar illumination, the voltage and current at the terminals of each subcell are usually different for each subcell.

[0084] Now refer to [ Figure 2 ]and[ Figure 3 ]. A string 101 of cells 1 connected in series with one another is shown. In this example, the subcells are connected in series. The cell 1 thus has only two terminals T1 and T2 (or connection terminals). In this simplified example, a single string 101 can be considered individually as a module. This module thus has only two terminals T1 and T2 (in [ Figure 2 ] at the top. These cells are thus compatible with the existing infrastructure of modules that supply two connectors for cells. These modules are thus compatible with the existing infrastructure of systems that supply two connectors for modules. This simplifies and improves backward compatibility at the expense of energy efficiency, which is limited to a lower current between two subcells (or between two PN junctions).

[0085] Each string and / or module may further comprise a diode arranged between the two terminals T1 and T2. This prevents the current from being reversed and therefore prevents the string and / or module from consuming power from the external network to which it is connected.

[0086] Now refer to [ Figure 4 ]and[ Figure 5 ]. The sub-battery is similar to [ Figure 2 ]and[ Figure 3 ] subcells. On the other hand, the subcells are not connected in series with one another, but remain independent of one another. Cell 1 thus has four terminals, namely two pairs: T1 and T2 on the one hand, and T3 and T4 on the other hand. In this simplified example, similar to [ Figure 2 ]and[ Figure 3 ] corresponds to the first string 101 of the battery 1 connected in series via its first pair of terminals T1 and T2. The string 101 thus also has two terminals T1 and T2 (in [ Figure 4 ] at the top. Moreover, a second string 102 similar to the first string corresponds to the battery 1 connected in series via its second pair of terminals T3 and T4. String 102 thus also has two terminals T3 and T4 (at [ Figure 4 ] at the bottom. Although the two sub-cells are physically integrated with each other in each battery 1, the current from each of the two types of sub-cells is separated from the battery 1 at the output. Two sets of dedicated connectors are used for each of the two types of sub-cells.

[0087] Electrically, Figure 4 Each of the two outputs T1-T2 and T3-T4 of the assembly represented in ] can be regarded as an independent photovoltaic sub-module. It is therefore at least theoretically possible to extract the maximum power for each sub-cell according to the properties of each sub-cell (each junction) and in particular the semiconductor material used. For this purpose, independent networks (electrically isolated from each other) can be provided downstream. This means that for a tandem battery with two sub-cells, compared to existing facilities with conventional cells (non-tandem type), double cables, double contacts, double inverters and double control components are required. This further increases the risk of failure and the cost of installation and maintenance. In addition, these batteries are often incompatible with the existing infrastructure of two connector modules and systems. At the expense of backward compatibility and reliability, the theoretical efficiency is improved and is no longer limited by the lower current between the two sub-cells (or between the two PN junctions).

[0088] Now refer to [ Figure 6 ]and[ Figure 7 ]. This example can be considered as a hybrid solution of the previous two examples. Compared to [ Figure 4 ]and[ Figure 5 ] example, a common potential is formed between the two subcells. A current extraction line is formed on one of the two subcells to prevent the current through the two subcells (two junctions) from being equal. This theoretically makes it possible to achieve a similar architecture to the previous one ([ Figure 4 ]and[ Figure 5 ]) efficiency. This architecture is particularly suitable for silicon-based cells with an interdigitated back contact (IBC) structure, especially because their contacts are completely moved into one of their faces. However, these cells are still relatively complex (and therefore expensive) to manufacture.

[0089] The embodiments described below are compared to [ Figure 2 ] embodiments can improve this situation. These embodiments, in particular, are related to [ Figure 4 ] four-terminal (or 4T) architecture and / or [ Figure 6 ]'s three-terminal (or 3T) architecture combination allows the sub-cells to be decoupled from the tandem cells downstream of the cell itself, so as to exploit the good theoretical efficiency of the tandem cells in practice while avoiding the proliferation of connections, wiring and electrical components.

[0090] In a tandem module, the performance of each junction is different due to the different properties of the semiconductor materials. Furthermore, these physical properties (eg bandgap energy or temperature coefficient) evolve differently with respect to sunlight irradiation and temperature.

[0091] Now refer to [ Figure 8 ]、[ Fig. 9 ]、[ Fig.10 ]and[ Fig.11 ]. Figure 8 ] shows a two-terminal module having terminals T1 and T2, while [ Fig. 9 ] shows the characteristic curve of a two-terminal module with terminals T1 and T2. The "wider" the curve (constant current for a wide range of voltages), the greater the power developed by the module. [ Fig.10 ] shows a four-terminal module with terminals T1 to T4, while [ Fig.11 ] shows the characteristics of a four-terminal module with terminals T1 to T4. The current-voltage characteristic curve of a two-terminal module with terminals T1-T2 is unique, while each pair T1-T2 and T3-T4 of a four-terminal module has its own independent current-voltage characteristic curve, which depends on the architecture of the module (bandgap energy and intermediate transmission) and also on the climatic conditions (temperature and light) in which the module is located.

[0092] Now refer to [ Fig.12 ]. Fig.12 ] represents a photovoltaic system 10. The system 10 includes an output inverter 11. The output of the system 10 is connected to a third-party network 1000 via the output inverter 11. The system 10 further includes a plurality of strings, each string having an index i, i being a positive integer in the range of 1 to 1, where I is the number of strings. Each string includes a plurality of modules 1 of tandem photovoltaic cells. Each module 1 i,j With the index i of the string to which it belongs and the index j identifying it within the string, j being a positive integer in the range 1 to J, where J is the number of modules 1 of the string.

[0093] In an installation having a module 1 with a single pair of connectors T1-T2 (e.g., as in [ Figure 2 ]、[ Figure 3 ]、[ Figure 8 ]and[ Fig. 9 ]), the modules are connected in series in order to reach a voltage level available for medium power converters, for example between 800V and 1,500V. The strings are connected in parallel with each other in order to increase their current and achieve high power levels. The simplest architecture comprises a single output inverter 11 to which all the strings of modules are connected. The output of the output inverter 11 is connected to a third party network 1000. This architecture is particularly suitable for very high power plants because it is particularly reliable and economical: a single converter is sufficient and not so expensive compared to the amount of energy supplied to the third party network 1000. A set of sensors and a distributed control and monitoring subsystem are sufficient.

[0094] Now refer to [ Fig.13 ] Each module 1 i,j With the first pair of connectors T1 i,j 、T2 i,jand the second pair of connectors T3 i,j 、T4 i,j , index corresponds to module 1 i,j Module 1 i,j Through its first pair of connectors T1 i,j 、T2 i,j In line with the above Fig.12 ] are connected in the same manner as described above. Module 1 i,j Also through its second pair of connectors T3 i,j 、T4 i,j As mentioned above, Fig.12 ] are connected in the same manner as described above, but with the aid of the connector T1 used for the first pair i,j 、T2 i,j Similarly, the second output inverter 11 is arranged between the second wiring and the third party network 1000 .

[0095] This architecture is thus obtained by doubling the connection and conversion equipment. Although the modules are based on tandem cells, each pair of terminals behaves as an independent module: precisely, if it is necessary to use the same type of inverter for both networks, the same type of terminals are connected in series in order to reach a usable voltage level (for example, between 800V and 1500V). Alternatively, the two types of terminals can correspond to different voltages. Then different output inverters can be used.

[0096] In this architecture, the two networks have been doubled compared to [ Fig.12 ] architecture, which doubles the complexity, risk of failure, and costs of equipment, installation, and maintenance.

[0097] Example A

[0098] Now refer to [ Fig.14 ]and[ Fig.15 ]. Terminals T2 and T3 are connected together, so that the module changes from four terminals to two terminals (series connection). Fig.15 ], connecting the outputs in series means that the current flowing through the two outputs is limited to the lowest current. The resulting characteristic curve is less than the sum of the characteristic curves of the two independent outputs (T1-T2 and T3-T4). In addition, when the current of the T3-T4 characteristic curve decreases (due to poor performance, specifically due to reduced illumination), the resulting T1-T4 characteristic curve will also pull down.

[0099] Now refer to [ Fig.16 ]and[ Fig.17 ]. Terminals T2 and T4 are connected to each other so as to be at the same potential, and terminals T1 and T3 are also connected to each other for the same reason, and the module changes from four terminals to two terminals (parallel connection). Fig.17], the parallel connection means that the resulting characteristic curve is less than the sum of the characteristic curves of the two independent outputs. In addition, once the T3-T4 characteristic curve is pulled to the left, that is, the current is maintained for the reduced voltage range (due to poor performance, specifically due to increased temperature), the resulting characteristic curve will also be pulled to the left.

[0100] Now refer to [ Fig.18 ]and[ Fig.19 ]. A DC-DC (direct current to direct current) converter 12 is arranged between the first pair of connectors T1-T2 and the second pair of connectors T3-T4. The converter 12 may be, for example, a simple "boost" converter (or a parallel DC-DC converter). Specifically, it may consist of two semiconductor switches: a transistor and a diode. The control of the converter 12 may include the implementation of an MPPT algorithm to optimize the power deducted from the second pair of connectors T3-T4 independently of the operating point of the first pair of connectors T1-T2. Thus, by means of the converter 12, electrical decoupling of the two series-stacked outputs may be ensured, and the output characteristic curve of the series-stacked module is wider.

[0101] Structurally, the converter 12 can be integrated into a string-stacked module so that the output from the module downstream of the converter 12 is equivalent to a module with two connectors, which makes it possible to adapt this module to existing conventional architectures.

[0102] This solution allows continuous optimization of the power generated, regardless of the operating conditions (sunlight exposure and temperature). This requires one converter 12 per module (rather than one converter per cell). Compared to a module in which one converter is provided for each cell, the costs and the risk of failure are significantly reduced: one converter per module is sufficient, instead of 60 or 72 converters as in known modules.

[0103] Preferably, the converter 12 is arranged on the back of the module (on the side of the module not exposed to sunlight). By protecting against direct sunlight and high temperatures, the risk of overheating of the converter is reduced.

[0104] Example B

[0105] Now refer to the corresponding embodiment B [ Fig. 20 ].

[0106] In embodiment B, multiple modules 1 are connected in parallel via their second pair T3-T4 to achieve a current range equivalent to the current range of a single module 1 via its first pair T1-T2. In order to avoid overly complex drawings, in [ Fig. 20 ] shows a single parallel connection. In practice, several parallel connections are applied to the system 10. In order to determine the number of modules to be connected in parallel via the second pair of connectors T3-T4, the ratio b(IT1-T2 / I T3-T4 = b), b is the integer number (rounded) of modules 1 to be connected in parallel. Fig. 20 ], an example is shown with b=3.

[0107] Embodiment B and its variants make it possible to connect connector pairs with different characteristics at relatively low cost (connections and cables). The operating point is still limited by the minimum voltage, which limits the yield from each pair, especially when the operating point changes due to changes in sunlight exposure or temperature.

[0108] Example C

[0109] Reference is now made to [ Fig.21 ]and[ Fig. 22 ]. In both embodiments, the converter 12 is shared compared to embodiment A. The second pair of connectors T3-T4 are each connected to the first pair of connectors T1-T2 in a group by means of a common converter 12. This is appropriate because the cascade outputs of the same string are usually in the same operating conditions. For modules of the same type, their characteristics when leaving the factory are very similar and remain so during their service life. Therefore, it is reasonable to assume that their MPPs are similar during operation.

[0110] In Example C1([ Fig.21 ]), the second connectors T3-T4 are connected to the main bus in parallel with the first connectors T1-T2 via the converter 12. The second connectors T3-T4 form a secondary bus, while the first connectors T1-T2 form a main bus. The two buses are each connected in parallel to each other via the output inverter 11. In embodiment C2 ([ Fig. 22 ]), the second connector T3-T4 is connected in series with the first connector T1-T2 to the main bus by means of a converter 12. The two buses are each connected in series to each other via an output inverter 11 and a converter 12.

[0111] A combination of embodiments B and C may achieve a good trade-off between cost and complexity. For example, embodiments C1 or C2 (sharing the converter across multiple modules) make it possible to even out any remaining differences at the output.

[0112] Example D

[0113] Now refer to [ Fig.23]. In this embodiment, the converter 13 is unique. The converter 13 comprises a modular central inverter of the CHB or MMC type (CHB stands for "cascaded H-bridge", MMC stands for "multi-level modular converter"). The converter 13 makes it possible to connect the second pair T3-T4 directly at one or more submodules (connected in series and / or in parallel). The optimization function of the second pair T3-T4 can thus be integrated into the controller of the converter 13, where the central inverter is formed. The modular central inverter then also implements the decoupling function between the first pair T1-T2 and the second pair T3-T4 with different characteristics. No additional DC-DC converter is required.

[0114] Industrial Applications

[0115] Embodiment A is applicable to all photovoltaic installations. The four-connector module according to embodiment A behaves like a conventional module, with good efficiency. Therefore, it can be used in small household installations, on the roof of a building, and in photovoltaic power plants. Therefore, the solution can be applied to new installations as well as the renovation of existing installations.

[0116] Embodiments B and C are applicable to all photovoltaic installations having at least one module string.

[0117] Embodiment D is particularly suitable for large installations and may advantageously replace existing solutions based on "string" or "hub" type inverters.

[0118] The present disclosure is not limited to the exemplary system described above by way of example, but covers all variations that can be thought of by a person skilled in the art within the framework structure for which protection is sought. Specifically, different embodiments can be combined with each other at different levels of the system (battery, submodule, module, string, bus, system).

[0119] Reference numerals list

[0120] -1: module;

[0121] -10: system;

[0122] -11: output inverter;

[0123] -12: Converter;

[0124] -13: Converter + output inverter;

[0125] -101, 102: string;

[0126] -1000: Third-party network.

Claims

1. A photovoltaic system comprising an output inverter (11, 13) for connecting to a third party network (1000), and at least one string (i), each string comprising at least one module (11) of a tandem photovoltaic cell. i,j ), each module has a first pair of connectors (T1 i,j 、T2 i,j ) and the second pair of connectors (T3 i,j 、T4 i,j ), The modules of a string are connected in series with each other by means of at least the first pair of connectors thereof, and the plurality of strings are connected in series by means of a connector (T1 i,1 、T2 i,J ) are connected in parallel to each other to the output inverter, A plurality of modules are further connected in parallel via their second pair of connectors to form a first group, the first group being further connected to a second group of modules via the second pair of connectors upstream of the output inverter, the second group of modules consisting of a single module or a series of modules connected in series to each other via their first pair of connectors.

2. The system according to claim 1, characterized in that Each module includes a converter, each first pair of connectors (T1 i,j 、T2 i,j ) and each second pair of connectors (T3 i,j 、T4 i,j ) is connected to the converter, and the converter is controlled by means of a maximum power point tracker algorithm MPPT, so that the second pair of connectors (T3 i,j 、T4 i,j ) is independent of the first pair of connectors (T1 i,j 、T2 i,j ) operating conditions.

3. The system according to claim 2, characterized in that The converter is mounted on the face of the module opposite to the operating face of the photovoltaic cells, so that the converter is protected from sunlight.

4. The system according to claim 1, characterized in that The first group and the second group each comprise a different number of modules, so that the ratio between these two numbers can be chosen to correspond at least approximately to the ratio of the unit operating voltages or currents of each of the two subcells constituting the tandem photovoltaic cell.

5. The system according to claim 1, characterized in that The first group and the second group include identical modules, the modules of the string being connected via their first pair of connectors (T1 i,j 、T2 i,j ), and on the other hand, through its second pair of connectors (T3 i,j 、T4 i,j ) are assembled in series, resulting in the first pair of connectors (T1 i,j 、T2 i,j ) and through the second pair of connectors (T3 i,j 、T4 i,j ), each string further comprising a converter, the converters are arranged in series or in parallel via the first pair of connectors (T1 i,j 、T2 i,j ) and through the second pair of connectors (T3 i,j 、T4 i,j ) between the strings formed by each converter by means of a maximum power point tracker algorithm MPPT control, so that the second pair of connectors (T3 i,j 、T4 i,j ) is independent of the first pair of connectors (T1 i,j 、T2 i,j ) operating conditions.

6. The system according to claim 5, characterized in that Arranged in series or in parallel via the first pair of connectors (T1 i,j 、T2 i,j ) and through the second pair of connectors (T3 i,j 、T4 i,j )The converter between the strings formed consists of two power switches.

7. The system according to claim 1, characterized in that The output inverter comprises a modular multi-input inverter, which is controlled by means of an independent maximum power point MPP tracker algorithm on each input, so that the output inverter is connected to the second pair of connectors (T3 i,j 、T4 i,j ) is independent of the first pair of connectors (T1 i,j 、T2 i,j ) operating conditions.

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