System for connecting at least one direct current photovoltaic power plant to an electrical power distribution or transmission network
A backbone line system with DC/DC converters for direct current transmission addresses the inefficiencies of existing systems, reducing costs and energy losses, enabling efficient connection of distant photovoltaic power plants with minimal components.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- TSE CO LTD
- Filing Date
- 2024-12-06
- Publication Date
- 2026-06-12
AI Technical Summary
Existing systems for connecting photovoltaic power plants to electrical power distribution networks are expensive, complex, and inefficient due to the need for numerous electrical components, leading to high costs, significant reactive power management, and energy losses, especially when plants are far from the distribution network.
A system comprising a backbone line connected to multiple photovoltaic power plants via auxiliary lines, using DC/DC converters to increase voltage and directly transmit DC power, eliminating the need for AC conversion and bulky substations, allowing connection of distant power plants with minimal components.
The system reduces costs, maintenance, and energy losses while providing flexibility and efficient connection of dispersed photovoltaic power plants, with potential energy savings of 2-4% compared to prior art systems.
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Abstract
Description
Title of the invention: System for connecting at least one direct current photovoltaic power plant to an electrical power distribution or transmission network. Field of the invention
[0001] The invention relates to the connection of a plurality of individual photovoltaic power plants to an electrical power distribution or transmission network.
[0002] More particularly, the invention relates to the connection of several photovoltaic power plants to an electrical power distribution or transmission network using a system essentially having a main or backbone line to collect the electricity produced with a set of photovoltaic power plants. State of the art
[0003] In the prior art, it is known to connect power plants, more particularly photovoltaic power plants, to an electrical power distribution network.
[0004] In such an electrical power distribution network, high-voltage lines adapted for the transmission of high-voltage electrical power, generally between 10 and 35 kV, are generally found. For long distances of electrical distribution, it is known that increasing the voltage reduces losses during transmission.
[0005] In order to supply the electrical power distribution network, the energy produced by the photovoltaic power plants must ultimately be conveyed to these high-voltage lines.
[0006] The electricity produced by photovoltaic power plants is, as a rule, direct current (DC), while the electricity transported by the aforementioned high-voltage lines is generally alternating current (AC). This is one of the reasons why, in the prior art, a system with the following structure is generally used:
[0007] Each photovoltaic power plant is connected to a DC / AC converter which converts the direct current (DC) produced by the photovoltaic power plant into alternating current at a voltage below 1000 kV. Then, using a transformer, this voltage will be increased before being sent to a substation.
[0008] The final connection between the point of supply of electricity produced by the photovoltaic power plants and the distribution network is generally called a "substation". Such a substation typically includes transformers, monitoring, protection and remote control equipment, and other equipment. energy metering, or even automatic load shedding systems to contribute to the safety of the electrical system.
[0009] The aforementioned structure, known in the prior art, has several significant drawbacks and limitations. First, the structure known for connecting photovoltaic power plants to a distribution network is relatively expensive. One of the main reasons for this is the large number of costly and relatively complex electrical components required by the system. The cost of such a well-known system is particularly high when the distance between the various photovoltaic power plants and the point of connection to the distribution network is relatively large.
[0010] Moreover, in the technical field of power plants, the trend is clearly towards the construction of an increasing number of small power plants. This means that there is a growing demand for the electrical components mentioned above.
[0011] As alternating current power distribution networks manage numerous generating plants from renewable resources over long distances of power lines, they are subject to significant reactive power management costs and associated voltage plans.
[0012] Energy losses due to Joule effect are also not negligible over the distances of alternating current electrical distribution networks.
[0013] In view of the above, there is an obvious need for a new, relatively inexpensive system for collecting electrical energy produced by photovoltaic power plants, which on the one hand offers some flexibility to the user and on the other hand allows for the efficient connection to the distribution network of photovoltaic power plants which are relatively far from it. Object of the invention
[0014] The object of the present invention relates to a system for connecting photovoltaic power plants to an electrical power distribution or transmission network, in which said system comprises:
[0015] - a plurality of electrical power generation units comprising at least one first and second electricity generation units, each electricity generation unit comprising a photovoltaic power plant,
[0016] - a main line extending from a first end to a second end and connected to a high-voltage line at said second end,
[0017] wherein each electrical power generation unit of the plurality of electrical power generation units is connected by an auxiliary line to said main line such that the plurality of electrical power generation units is connected to the distribution or transmission network by means of a single connection,
[0018] wherein the system is adapted to transport electrical energy from the plurality of electrical power generation units in the form of direct current (DC) towards the distribution or transmission network, and
[0019] wherein the second end of the main line is provided with a DC connection element enabling said second end to be connected to a source substation connected to the distribution or transport network.
[0020] According to one embodiment of the invention, the connection of the electrical power production units via the auxiliary lines to the main line essentially has the structure of a backbone.
[0021] According to one embodiment of the invention, at least one of the energy production units is equipped with an electrical energy storage device, such as a battery.
[0022] According to one embodiment of the invention, each of the auxiliary lines is equipped with a DC / DC converter allowing the voltage of the direct current (DC) to be increased before it is supplied to the main line.
[0023] According to one embodiment of the invention, the system is adapted to supply a direct current to the high voltage line at a voltage of 5-20 kV, more particularly at a voltage of 10-20 kV. Brief description of the drawings
[0024] The purpose, object and features of the invention will become clearer upon reading the following description made with reference to the figures in which:
[0025] [Fig. 1] is a schematic representation of a system for connecting photovoltaic power plants to an electrical power distribution network, exhibiting an architecture according to the prior art, and
[0026] [Fig.2] is a schematic representation of a power plant connection system photovoltaic systems connected to an electrical power distribution network, featuring an architecture according to an embodiment of the invention, Detailed description of the invention
[0027] It should be noted that, in the following description, the standard terms DC (direct current) and AC (alternating current) known in the English language are used to refer respectively to a direct current and an alternating current.
[0028] In the description, the term "source substation" is used. It should be noted that this term refers to all the equipment used to connect a power supply line to a distribution or transmission network. Such a source substation typically includes transformers, monitoring, protection and remote control equipment, and metering equipment. energy, or even automatic load shedding systems to contribute to the security of the electrical system.
[0029] Fig. 1 shows a schematic representation of a system 1 for connecting photovoltaic power plants to an electricity distribution network, with an architecture according to the prior art.
[0030] In the example of [Fig. 1], system 1 comprises four photovoltaic power plants 10, 20, 30, 40. Photovoltaic power plant 10 produces direct current (DC) which is carried by a line to an inverter 11. The inverter 11 converts the direct current (DC) into alternating current (AC) at a voltage below 1000V. The power from the photovoltaic power plant is then carried to a transformer 12 to increase the voltage to a voltage compatible with the grid.
[0031] The photovoltaic power plants 20, 30, 40 are similarly equipped with an inverter 21, 31, 41 and a transformer 22, 32, 42 respectively.
[0032] From transformers 12, 22, 32, the high-voltage alternating current (AC) is optionally routed to a substation 70, which functions as a collection station. From substation 70, the collected alternating current (AC) is routed to a terminal station 50, which connects the incoming power line to a source substation 60, itself connected to the distribution network.
[0033] The transformer 42 of the fourth photovoltaic power plant 40 is directly connected to the terminal station 50. [Fig.1] further shows the presence of a battery 55, adapted to store a determined quantity of electricity at the terminal station 50 using respectively an inverter 51 and a transformer 52.
[0034] In the embodiment of [Fig.1], system 1 comprises a total of four photovoltaic power plants 10, 20, 30, 40. It is understood that the architecture of system 1 can also be used for a larger number of photovoltaic power plants.
[0035] One of the main drawbacks of system 1 in [Fig. 1] is that it contains a large number of electrical components, such as a large number of inverters 11, 21, 31, 41, 51, transformers 12, 22, 32, 42, 52, substations 40, 50, circuit breakers, disconnectors, etc. In addition, the implementation of system 1 requires many long cables.
[0036] These electrical components make system 1 relatively expensive and require a great deal of upkeep and maintenance. Furthermore, the installation of all the aforementioned electrical components, such as the substations 40, for example, requires a relatively large amount of space, resulting in high costs, for example, with regard to the necessary real estate.
[0037] Furthermore, due to the high cost and limited flexibility offered by the architecture of system 1, the system 1 illustrated in [Fig. 1] is not suitable for Connect the photovoltaic power plants to the distribution network as soon as the distance between the different photovoltaic power plants 10, 20, 30 and the distribution network becomes too great. In system 1 of [Fig. 1], the distance between the different photovoltaic power plants 10, 20, 30 and the distribution network is generally no more than 5 kilometers.
[0038] Fig. 2 shows a schematic representation of a system 100 for connecting the power production units 110, 120, 130 to an electrical power distribution network by means of the source substation 60, with an architecture according to the invention.
[0039] The system 100 includes a main line 170 which constitutes the backbone or dorsal core of the system 100. Said main line 170 extends between a first end 171 and a second end 172. The first end 171 is connected to the first electrical power generation unit 110. The connection between the first electrical power generation unit 110 and the first end 171 of the main line 170 includes a first connecting element 113 such as a DC connector.
[0040] The second end 172 of the main line 170 is connected to a DC / AC inverter 180 which provides the transformation into alternating current (AC) and which forms the connection of the system 100 to the source substation 60.
[0041] Each electrical power production unit 110, 120, 130 of the system includes at least one photovoltaic power plant 111, 121, 131 and a DC / DC converter 112, 122, 132.
[0042] Each electrical power generation unit 110, 120, 130 is connected to the main line 170 via a DC connector 113, 123, 133. Between the DC connector 113 and the rest of the main line 170, a circuit breaker 114 is present. Between the DC / DC converter 122 and the DC connector 123, a circuit breaker 124 is present. Between the DC / DC converter 132 and the DC connector 133, a circuit breaker 134 is present.
[0043] Figure 2 shows that the architecture of system 100 connects the photovoltaic power plants 111, 121, 131 to the main line 170 by means of auxiliary lines, the main line 170 functioning as a central or backbone collection line. This is why the structure of system 100 can be described as a "backbone".
[0044] A characteristic of system 100 according to [Fig. 2] is that the direct current produced by the photovoltaic power plants 111, 121, 131 is carried by the main line 170 to the substation 60 as direct current (DC). Unlike prior art systems, such as system 1 in the example of [Fig. 1], the direct current (DC) produced is not converted to alternating current (AC) using DC / AC inverters before being transported to the substation 60.
[0045] A large number of power generation units 110, 120, 130 can be connected between the first end 171 and the second end 172 of the main line 170. In the example in [Fig. 2], for practical reasons, only three power generation units 110, 120, 130 are shown. It is evident that the system 100 is suitable for connecting a large number of power generation units to the substation 60.
[0046] System 100 of [Fig. 2] is perfectly suited for the transmission of medium- to high-voltage direct current (DC). In English, the well-known term "medium voltage DC" or "MVDC" is used to designate this medium- to high-voltage direct current (DC).
[0047] The DC / DC converters 112, 122, and 132 are designed to step up the 1500Vdc voltage generated by the solar panels of the photovoltaic power plants 111, 121, and 131 to a voltage between + / - 5kV and + / - 30kV. This is intended to transmit the full power of the photovoltaic power plants 111, 121, and 131 to the main line 170, which operates as an MVDC bus. These converters 112, 122, and 132 are connected to the DC network via dedicated DC connectors 113, 123, and 133, respectively.
[0048] The role of the DC connectors 113, 123, 133 is to allow the connection and disconnection of each photovoltaic power plant 111, 121, 131 to the main line 170. The DC connectors 113, 123, 133 also offer the possibility of diverting power in the event of a direct connection of a DC load, without going through AC conversion, thus ensuring the protection of the equipment. This option is not shown in [Fig. 2], but implies that electrical loads are also connected to the main line 170 between the ends 171 and 172 of said main line.
[0049] The system 100 according to [Fig.2] aims to manage the connection, disconnection and diversion of power from the photovoltaic power plants 111, 121, 131, thus enabling the creation of a multi-terminal DC power production network and, possibly, the provision of DC power for applications such as data centers or the SNCF or any other electricity consumer, while ensuring the protection functionality of the upstream system's electrical equipment.
[0050] The system in [Fig. 2] is particularly suitable for collecting and supplying electricity with a voltage between + / -5kV and + / -20kV. System 100 is more particularly suited for conveying a direct current (DC) of 10 kV.
[0051] As shown by the comparison between Figures 1 and 2, the system according to [Fig. 2] is simple and comprises a minimal number of components. This means that, compared to system 1, system 100 is relatively inexpensive both in terms of materials and maintenance.
[0052] Figure 2 also shows that the system 100 according to Figure 2 is relatively compact. No bulky and expensive substation, no intermediate station, and no other structure is required to connect the various electrical power generation units 110, 120, 130 and the source substation 60.
[0053] Due to the system's simple architecture and small size, system 100 is ideally suited for collecting electrical energy produced by power generation units 110, 120, 130, even when these units are relatively far from the source substation. Power generation units typically located more than 8 kilometers from a distribution network can be conveniently connected to this distribution network thanks to the architecture of system 100 as shown in [Fig. 2].
[0054] Moreover, the system architecture according to [Fig.2] is particularly suitable for connecting a large number of photovoltaic power plants to the distribution network, using a single source substation 60.
[0055] This is an important advantage of system 100, considering that, in the technical field of power plants, a clear trend can be observed, namely that more and more relatively small photovoltaic power plants are being built, spaced far apart from each other. This means that there is a growing demand from distribution network operators to be able to connect photovoltaic power plants to the distribution network using such a substation 60.
[0056] It should be noted that, in addition to the advantages of the system 100 mentioned above, said system 100 allows a potential energy saving of about 2 to 4% compared to systems known in the prior art.
[0057] According to the example in [Fig.2], the power production unit 110 is equipped with a photovoltaic power plant 111, a DC / DC converter 112 and also a battery 190 and an associated DC / DC converter 191.
[0058] The battery 190 is used to temporarily store the electrical energy produced by the photovoltaic power plant 111. The battery 190 can typically be used to store excess electrical energy during the day, when the amount of electrical energy produced exceeds the instantaneous demand.
[0059] When needed, the electrical energy stored in the battery 190 can be routed to the distribution network via the associated DC / DC converter 191 and through the main line 170. This means that the presence of one or more batteries 190 in the system 100 can stabilize the energy supply to the distribution network during the day.
[0060] Figure 2 shows that the DC / AC inverter 180 is connected to the source substation 60 by means of a terminal station 150. According to the example in Figure 2, said station Terminal 150 is equipped with a battery 155 for temporarily storing the electrical energy transmitted to the source substation 60. The battery 155 can typically be used to store excess electrical energy during the day, when the amount of electrical energy produced exceeds the instantaneous demand. The battery 155 is connected to terminal station 150 by means of a DC / AC inverter 156 and a transformer 157.
Claims
Demands
1. A system (100) for connecting photovoltaic power plants to an electrical power distribution or transmission network, wherein said system comprises: - a plurality of electrical power generation units (110, 120, 130) comprising at least a first and a second electrical power generation unit (110, 120, 130), each electrical power generation unit (110, 120, 130) comprising a photovoltaic power plant (111, 121, 131), - a main line (170) extending from a first end (171) to a second end (172) and connected to a high-voltage line at said second end (172), wherein each electrical power generation unit (110, 120, 130) of the plurality of electrical power generation units (110, 120, 130) is connected by an auxiliary line to said main line (170) such that the plurality of electrical power generation units (110, 120,130) is connected to the distribution or transmission network by means of a single connection, wherein the system is adapted to transport the electrical energy from the plurality of electrical power generation units (110, 120, 130) in the form of direct current (DC) towards the distribution or transmission network, and wherein the second end (172) of the main line (170) is provided with a DC connecting element (113, 123, 133) enabling said second end (172) to be connected to a source substation (60) connected to the distribution or transmission network.
2. System (100) according to claim 1, wherein the connection of the electrical power generation units (110, 120, 130) via the auxiliary lines to the main line (170) essentially has the structure of a backbone.
3. System (100) according to claim 1 or 2, wherein at least one of the electrical power production units (110, 120, 130) is equipped with an electrical power storage device (190), such as a battery.
4. System (100) according to claim 1, 2 or 3, wherein each of the auxiliary lines is equipped with a DC / DC converter (112,
5. 122, 132) allowing the voltage of the direct current (DC) to be increased before it is supplied to the main line (170). System (100) according to any one of the preceding claims, wherein the system (100) is adapted to supply direct current to the high voltage line at a voltage of 5-20 kV, more particularly at a voltage of 10-20 kV.