electrical architecture including at least one linear photovoltaic installation consisting of several groups of photovoltaic panels and a direct current (DC) network, connected to an alternating current (AC) transmission and / or distribution network with arbitration of the power injected from the DC network to the AC network.

Abstract

An electrical architecture comprising at least one linear photovoltaic installation consisting of several groups of photovoltaic panels and a direct current (DC) network, connected to an alternating current (AC) transmission and / or distribution network with arbitration of the injected power from the DC network to the AC network. The invention essentially consists of setting up an architecture with at least one linear PV installation with a DC network and interconnecting this subset at at least two distinct interconnection points with a preferably existing AC electrical network. Each interconnection point to a node of the AC network is a voltage source converter (VSC) that can inject from 0 to 100% of the maximum power P of the linear PV installations. Figure for the abstract: Fig. 2

Description

Title of the invention: Electrical architecture comprising at least one linear photovoltaic installation made up of several groups of photovoltaic panels and a direct current (DC) network, connected to an alternating current (AC) transport and / or distribution network with arbitration of the power injected from the DC network to the AC network. Technical field

[0001] The present invention relates to the general field of electrical networks.

[0002] The invention relates more particularly to the interconnection between an alternating current (AC) transport and / or distribution network and at least one linear photovoltaic installation.

[0003] By "linear PV installation" is meant here and within the scope of the invention, photovoltaic panels arranged in groups along a surface which extends mainly along a line and preferably on or along ground already built / developed by man, such as cycle paths, highway edges, railway lines, etc. or natural, for example not usable for agricultural purposes.

[0004] Throughout the application the following acronyms are used for simplicity:

[0005] AC: Anglo-Saxon acronym for “Alternative Current” which designates alternating current (AC);

[0006] DC: Anglo-Saxon acronym for “Direct Current” which designates direct current (DC);

[0007] MVDC: Anglo-Saxon acronym for “Medium Voltage Direct Current” which designates medium voltage direct current, typically in the range of 30 to 150 kilo volts (kV);

[0008] HVDC: Anglo-Saxon acronym for “High Voltage Direct Current” which designates high voltage direct current, typically above 150 kilo volts (kV);

[0009] VSC: Anglo-Saxon acronym for “Voltage Source Converter” which designates a converter operating as a voltage source;

[0010] MMC: Anglo-Saxon acronym for “Modular Multi-Level Converter” which designates a converter with multi-stage modules. Prior art

[0011] The context of strong demand for renewable energy (RE) with the need for a dedicated electricity network, typically up to 30% in 2030 in France and expansion of the share of solar energy in renewable energy requires the installation of numerous ground-based photovoltaic (PV) solar power plants, with large capacities, typically in the order of several hundred MW each.

[0012] The question of land available for this PV technology therefore becomes crucial. Indeed, given the surface area required, the deployment of large ground-mounted PV solar power plants can create conflicts of use with agricultural land and affect biodiversity. For example, the most powerful PV solar power plant in France to date, with a capacity of 300 MW, is located in Cestas, near Bordeaux, on 260 hectares.

[0013] Finding new land to develop PV solar power plant projects has therefore become the main concern of renewable energy developers.

[0014] Furthermore, given the desire of public authorities to limit the use of large agricultural areas for the construction of such ground-based PV power plants, ecologically acceptable alternatives must be found.

[0015] A solution that addresses this problem consists of taking advantage of so-called linear surfaces, in the form of land already developed / constructed by man, such as cycle paths, highway edges, railways... or natural surfaces, not usable for agricultural purposes, such as along waterways and which extend over tens, even hundreds of kilometers, to install high-power PV systems. These potential surfaces have the advantage of already being very present, directly usable as is to install PV panels and inexpensive since they do not require the acquisition of land.

[0016] The implementation of new types of linear PV installations / power plants will therefore open up new opportunities in the PV development strategy. There are already a few linear PV installation projects in the world, but these are a priori of small power, typically a few kW. In addition, very few articles on the design of these linear PV installations have been published.

[0017] However, moving from PV power plants occupying tens or hundreds of hectares to linear PV installations extending over tens of hectometres or kilometres requires rethinking the entire architecture of the related electricity network.

[0018] Generally speaking, the European Union's strategies for the development of large-scale renewable energy sources highlight the important roles of electricity infrastructure and sector coupling, i.e. the interconnection between gas and electricity, in achieving deep decarbonisation of the economy.

[0019] There is therefore a need to propose an optimized technical solution for electrical architecture which allows the massive connection of linear PV installations to the existing electrical infrastructure.

[0020] The aim of the invention is therefore to respond at least in part to this need. Statement of the invention

[0021] To do this, the invention relates, in one of its aspects, to an electrical architecture comprising:

[0022] - at least one linear installation comprising at least one group of panels photovoltaic (PV), suitable for producing a maximum total power P, and

[0023] a direct current (DC) network comprising at least one bus to which the groups of PV panels are connected in electrical parallel via each of a DC / DC converter,

[0024] - an alternative transport and / or distribution network (AC),

[0025] - at least two voltage source converters (VSC), one of the two converters weavers connecting the DC bus to a first node of the AC network, the other of the two converters connecting the DC bus to a second node of the AC network, distinct from the first node, each of the VSC converters being adapted to inject from 0 to 100% of the power P into the AC network,

[0026] - a control system adapted to distribute the power injection between the VSC converters according to the needs and / or operating regimes of the AC network, so as to reduce the total losses of the latter and / or improve the quality of service of the AC network, i.e. improve the capacity to meet the needs of the AC network.

[0027] The possible control modes of VSC converters are:

[0028] - Vac / f: Control of the voltage at the connection point and the frequency of the AC network - Vac-phi: Control of the voltage at the AC network connection point and the phase shift - Vdc-phi: Control of the DC bus voltage and phase shift - Vdc-Q: Control of DC bus voltage and reactive power - PWM-phi: Control of the PWM modulation of the VSC inverter and the phase shift - P-Vac: Control of injected power and voltage at the AC network connection point - PQ: Control of active and reactive power injected into the AC network - Vdc-Vac: Control of the DC bus voltage and the voltage at the connected point of the AC network - P-cos(f): Control of active power injected into the AC network and of the power factor - Vdc-cos(f): Control of the DC bus voltage and the power factor...

[0029] Among all these control modes, the PQ; P-Vac control modes are pri- revered for the power injection distribution function according to the invention.

[0030] Advantageously, the VSC converters are modular multilevel converters (MMC).

[0031] According to an advantageous configuration, the bus to which the group(s) of PV panels are directly connected in electrical parallel is a medium voltage direct current (MVDC) bus.

[0032] According to an advantageous embodiment variant, the architecture comprises several geographically distributed loads, such as high-power electric vehicle charging stations or electrolysers for powering hydrogen-powered vehicles, each connected via a DC / DC converter to the MVDC bus.

[0033] According to another advantageous embodiment variant, the architecture comprises several geographically distributed electrical storage means, such as batteries, each connected via a DC / DC converter to the MVDC bus.

[0034] According to another advantageous variant embodiment, the architecture comprises other geographically distributed current sources, such as wind turbines, each connected via a DC / DC converter to the MVDC bus.

[0035] According to an advantageous embodiment, the DC network of the linear installation comprises at least one high voltage direct current (HVDC) bus connected to the medium voltage direct current (MVDC) bus and to a voltage source converter (VSC) connected to a node of the AC network.

[0036] The control system can advantageously be connected to the real-time control and data acquisition (SCADA) system of the AC network. This makes it possible to identify the needs and / or operating regimes of the AC network, so as to differentiate the injection power to be distributed between the at least two injection nodes in order to reduce the total losses of the AC network or contribute to its quality of service.

[0037] According to another advantageous embodiment, the architecture comprises means for measuring voltage and / or frequency at the first and second nodes, connected to the control system so that it distributes the power injection between the VSC converters according to the measurements carried out.

[0038] Thus, the invention essentially consists of setting up an architecture with at least one linear PV installation with a DC network and interconnecting this subassembly at at least two separate interconnection points with a preferably existing AC electrical network. Each interconnection point at a node of the AC network is a voltage source converter VSC which can inject from 0 to 100% of the maximum power P of the linear PV installations.

[0039] The invention therefore consists of arbitrating the injection of electricity produced by the ins-

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[0048] linear PV connections between these two (or more) VSC interconnection points which therefore constitute injection points at the nodes of the AC network in order to reduce the total losses of the AC network, taking into account the needs and / or operating regimes of the latter. Unlike a state-of-the-art PV power plant which is located at a specific point on the electricity grid and therefore capable of injecting only at that point, the architecture according to the invention with a linear PV installation distributed over a large geographical area allows interconnection at several distant points on the electricity grid. The architecture of the invention allows maintaining high reliability and resilience of the existing electricity network while expanding its capacity to integrate large quantities of renewable energy (RE) in the future through linear PV installations. Ultimately, an architecture according to the invention has many advantages, including: - due to the choice of linear installations, a significant reduction in land use as well as a reduction in the construction of HVAC lines; an increase in the penetration capacity of PV systems into the existing AC electricity grid; a reduction in PV production variation due to intermittency thanks to the aggregation of linear installations over a long distance; - improving network flexibility, through the possibility of exchanging energy in both directions between a DC network and an AC network; - high reliability and resilience; - an improvement in the stability of the AC network; - the possibility of maintaining continuity of service in the event of a fault or separation of the AC network; - a simplification of energy management; - ease of connecting DC systems such as storage and / or high-power fast charging stations for EVs and / or electrolyzers and fuel cells to the DC network of linear installations; - the possibility of coupling with offshore or on-shore wind farms... - the possibility of effective protection between an AC network and a DC network; - the reduction of total losses of the AC network by the optimal distribution of power. Other advantages and characteristics of the invention will become more apparent upon reading the detailed description of examples of implementation of the invention given as illustrative and not limiting with reference to the following figures. Brief description of the drawings

[0049] [Fig. 1] [Fig.l] schematically illustrates an electrical architecture according to the invention as it could be implemented in the south-eastern region of France.

[0050] [Fig.2] [Fig.2] is a synoptic view of the electrical architecture according to the invention.

[0051] [Fig.3] [Fig.3] is a schematic view illustrating an architecture according to the invention restricted to two connections by VSC converters between the DC network and the AC network.

[0052] [Fig.4] [Fig.4] is a schematic view of the “New-England IEEE 39 nodes” test network on which the DC network power injection tests according to the electrical architecture of the invention were carried out. Detailed description

[0053] [Fig.l] shows an architecture according to the invention as it could be implemented in the south-eastern region of France.

[0054] As illustrated, this electrical architecture comprises a plurality 1 of groups of photovoltaic (PV) panels 10, adapted to produce a maximum total power P. These groups of panels 10 are distributed over hundreds of kilometers in this region by being arranged on elongated ground surfaces on land already built by man, such as along railway edges, highways, etc.

[0055] All these groups of panels are connected in electrical parallel by at least one bus 20, 21 of a direct current (DC) network 2, to form a single linear PV installation. This linear PV installation is itself connected to the transmission network 3 and / or distribution network 4 already existing in this region. All the groups of PV panels are therefore connected to each other by at least one DC bus 20, 21. [Fig. 2] shows in more detail the components and the possible connection modes according to an embodiment of such an architecture.

[0056] In this [Fig.2], the groups of PV panels are distributed along a line L on the ground. The plurality 1 of these PV groups can produce a maximum total power P.

[0057] The linear PV installation comprises the plurality of panel groups 10 as well as the DC network 2, which here comprises several MVDC buses 20 to which the panel groups 10 are connected in electrical parallel, each via a DC / DC converter 11.

[0058] The DC network also includes several HVDC buses 21 within the linear PV installation, each connected to one or more of the MVDC buses 20. The HVDC buses 21 can carry direct current throughout the DC network.

[0059] Each MVDC bus 20 or HVDC bus 21 of the linear installation is connected to a node of an AC transport network 3 or to that of an AC distribution network via a voltage source converter 22.

[0060] Preferably, the VSC converters 22 are modular multilevel converters (MMC).

[0061] According to the invention, each of the VSC converters 22 is adapted to inject from 0 to 100% of the power P into the AC network.

[0062] According to the invention also, an architecture control system can distribute the power injection between all the VSC converters 22 according to the needs and / or operating regimes of the AC network, so as to reduce the total losses of the latter and improve the quality of service on the latter.

[0063] As also illustrated in this [Fig.2], the DC network of the architecture includes several geographically distributed loads, such as high-power electric vehicle (EV) charging stations or electrolyzers (H2) for hydrogen vehicles. Each of these loads is connected directly to the MVDC bus 20 via a DC / DC converter 23.

[0064] The DC network can also support several geographically distributed electrical storage means, such as batteries. Each storage means is also directly connected to the MVDC bus 20 via a DC / DC converter 23.

[0065] To illustrate the operation of the architecture according to the invention, [Fig. 3] shows only two VSC converters 22 which carry out the coupling between the DC network of the linear installation, connected to the plurality 1 of PV groups 10 and the AC network 3, 4. More precisely, the AC network schematically comprises four nodes N1 to N4, the node NI being the coupling node of the VSC converter 21, the node N2 being the coupling node of the VSC converter 22.

[0066] In this configuration, the power injected by each of the converters VSC1 and VSC2 is based on the need of the AC network. The transit power P12 between NI and N2 is in the direction of the arrow indicated in [Fig.3]. If the line between NI and N2 is very loaded, there is a risk of overload.

[0067] In this case, according to the invention, the architecture control system can reduce the injected power PI at the level of VSC1 and increase the injected power P2 at the level of VSC2 in order to reduce the overload of the line N1-N2. This control system is preferably the one integrated into the linear PV installation and which controls the operation of the linear PV installation. This has the advantage of local autonomy of arbitration of the injected powers PI and P2.

[0068] Alternatively, it could be a control system external to the linear PV installation, for example linked to the SCADA system for regulating the AC network.

[0069] Generally, the power between PI and P2 can be adjusted, in order to reduce the total losses of the AC network, or improve its quality of service.

[0070] Validations of the architecture proposed according to the invention were carried out on the IEEE New-England 39-node test AC transport network. This AC network, shown diagrammatically in [Fig.4], is a simplification of the New-England network in the American northeast. It comprises 39 nodes, including 10 production nodes (numbered from 30 to 39) and 46 lines. In particular, at node 29, there is a generator G9.

[0071] The total production and consumption of the New-England AC network are respectively 6147 MW and 6097 MW.

[0072] The validations carried out on this New-England network are done with the software marketed under the name “Powerfactory” by the company Digsilent.

[0073] The validation test hypotheses are made by considering a number of six groups of PV panels all connected in electrical parallel to a DC bus of the linear PV installation. The maximum power of each PV group is 50 MW, i.e. a maximum total power P of 300 MW of the linear installation.

[0074] The DC bus is connected to two VSC converters which are connected to the New-England AC network at nodes 26 and 29, referenced VSC_26 and VSC_29 respectively.

[0075] In other words, in the tests, these two VSC converters, VSC_26 and VSC_29, ensure the injection of production from the six PV groups into the New-England AC network.

[0076] The block diagram of the test configuration is shown in [Fig.4].

[0077] For the tests, the power of these two VSCs is variable like an ar injection bitrate, depending on needs and / or operating regime of the AC network.

[0078] More precisely, to see the impact of optimal power distribution between the two VSC_26 and VSC_29, 5 cases were tested depending on the production power of the generator G9.

[0079] For each of these 5 cases, the two VSC_26 and VSC_29 together ensure the injection of the maximum total power P. For each of the cases, to reduce the power transit on lines 29-26 and 29-28, all or part of the power P is injected into the two VSC_26 and VSC_29 and the total losses of the AC network are evaluated.

[0080] From one case to another, we therefore change the power injected into each of the two VSC_26 and VSC_29, respectively noted P_VSC_26 and P_VSC_29 as a function of the production power of the generator G9 (P_G9).

[0081] Table 1 below summarizes all cases, numbered 1 to 5, the powers and losses evaluated, with a total power of the linear PV system of 300 MW.

[0082] [Tables 1] Case P_G9 (MW) P_VSC_26 (MW) P_VSC_29 (MW) Losses (MW) Case 1 730 300 0 57.53 Case 2 630 200 100 51.26 Case 3 530 100 200 48.7 Case 4 430 0 300 50.2 Case 5 430 270 30 44.16

[0083] From this table 1, it appears that:

[0084] - case 5 is the one where the total losses are minimal; - total losses are reduced by approximately 23% from case 1 to case 5; - with an optimal distribution of injected power between the two VSCs, P_VSC_26 and P_VSC_29, losses on the AC network can be optimally reduced.

[0085] Consequently, these tests show that if the distribution of power injected on the different VSC coupling points between the DC network of the linear PV installation, connected to a plurality of groups of PV panels in electrical parallel and an AC network is optimal, the total losses on the AC network reduce.

[0086] The invention is not limited to the examples which have just been described; in particular, it is possible to combine characteristics of the illustrated examples within non-illustrated variants.

[0087] Other variants and embodiments may be envisaged without departing from the scope of the invention. List of cited references

[0088] [1]: T. Athay, R. Podmore, and S. Virmani. “A Practical Method for the Direct Analysis ofTransient Stability”. In: IEEE Transactions on Power Apparatus and Systems PAS-98 (2 Mar. 1979), pp. 573-584.

[0089] [2]: MA Pai. “Energy function analysis for power system stability”. The Kluwer in international series in engineering and computer science. Power electronics and power systems. Boston: Kluwer Academy Publishers, 1989.

Claims

Claims

1. Electrical architecture comprising: - at least one linear installation comprising at least one group of photovoltaic (PV) panels (10) adapted to produce a maximum total power P, and a direct current (DC) network (2) comprising at least one bus (20, 21) to which the group(s) of PV panels are connected in electrical parallel via each of a DC / DC converter (11), - an alternating current (AC) transmission (3) and / or distribution (4) network, - at least two voltage source converters (22) (VSC), one of the two converters connecting the DC bus to a first node of the AC network, the other of the two converters connecting the DC bus to a second node of the AC network, distinct from the first node, each of the VSC converters being adapted to inject from 0 to 100% of the power P into the AC network,- a control system adapted to distribute the power injection between the VSC converters according to the needs and / or operating regimes of the AC network, so as to reduce the total losses of the latter and / or to improve the quality of service of the AC network.,

2. Architecture according to claim 1, the VSC converters being modular multilevel converters (MMC).

3. Architecture according to claim 1 or 2, the converters being controlled according to a mode of control of injected power and voltage at the network connection point (P-Vac: AC) or according to a mode of control of active and reactive power injected into the AC network (PQ).

4. Architecture according to one of the preceding claims, the bus (20) to which the group(s) of PV panels are directly connected in electrical parallel being a medium voltage direct current (MVDC) bus.

5. Architecture according to claim 4, comprising several geographically distributed loads, such as high-power electric vehicle charging stations or electrolysers for powering hydrogen-powered vehicles, each connected via a DC / DC converter (23) to the MVDC bus.

6. Architecture according to claim 4 or 5, comprising several geographically distributed electrical storage means, such as batteries, each connected via a DC / DC converter. (23) to the MVDC bus.

7. Architecture according to one of claims 4 to 6, comprising other geographically distributed current sources, such as wind turbines, each connected via a DC / DC converter (23) to the MVDC bus.

8. Architecture according to one of claims 4 to 7, the DC network of the linear installation comprising at least one high voltage direct current (HVDC) bus connected to the medium voltage direct current (MVDC) bus and to a voltage source converter (22) (VSC) connected to a node of the AC network.

9. Architecture according to one of the preceding claims, the control system being connected to the real-time control and data acquisition (SCADA) system of the AC network.

10. Architecture according to one of the preceding claims, comprising means for measuring voltage and / or frequency at the first and second nodes, connected to the control system so that it distributes the power injection between the VSC converters according to the measurements carried out.

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