A connecting system for a weathervaning floating offshore wind turbine, a floating offshore wind turbine system, and an interconnected system

Abstract

A connecting system (100) for connecting a weathervaning floating offshore support structure (200) of a wind turbine (201) to a pre-laid mooring system (300), the connecting system (100) comprising: - a turret element (1) comprising: a base (2) for being solidly connected to the pre-laid mooring system (300); a support element (3) comprising a switchgear (31) connectable to one or more submarine cables (400) and connectable to receive a power generated by the wind turbine (201); a columnar body (4) extending from the base (2) to the support element (3), and comprising an inner passage (41); and a bearing system (5) configured to rotatably connect the turret element (1) to the weathervaning floating offshore support structure (200); and - a slip-ring connector (6) comprising a first connecting part (61) for receiving the power generated by the wind turbine (201), and a second connecting part (62) cable-connectable to the switchgear (31).

Description

[0001] A connecting system for a weathervaning floating offshore wind turbine, a floating offshore wind turbine system, and an interconnected system

[0002] TECHNICAL FIELD

[0003] The present invention relates to a connecting system for connecting a weathervaning floating offshore support structure of a wind turbine to a pre-laid mooring system. The invention further relates to a floating offshore wind turbine FOWT system comprising a weathervaning floating offshore support structure of a wind turbine, a pre-laid mooring system and a connecting system configured to connect the weathervaning floating offshore support structure of the wind turbine to the pre-laid mooring system. The invention also refers to an interconnected system comprising a floating offshore wind turbine FOWT system connected to a plurality of external electrical elements.

[0004] PRIOR ART

[0005] The invention belongs to the field of floating offshore structures and more specifically to the field of offshore floating wind turbines, but could be of application to the fields of wave energy converters and tidal stream turbines. Various prior art solutions have been explored in this domain, aiming to enhance the ease of installation and functionality of FOWT systems. The following overview highlights some of these prior art solutions along with their associated disadvantages.

[0006] Traditional floating offshore wind turbine (FOWT) systems of the prior art have a station-keeping mooring system that provides enough stability in all degrees of freedom to allow stable operation of a horizontal axis wind turbine (HAWT) nacelle mounted on top. The HAWT has an active yaw system that maintains the turbine rotor axis oriented to the incoming wind direction, to maximise energy production. This is equivalent to what is done with fixed-bottom wind turbines, offshore and offshore. In these conditions, the inter-array submarine electrical cables (generally operating at a voltage between 20 kV and 66 kV, but planned to go at even higher voltage in the future) that typically connect each FOWT to an electrical grid are routed into the FOWT floating support structure using a l-tube or J-tube that brings the cable (or cables) into the hull. Once inside the hull, these cables are connected to a switchgear. If several FOWTs are “daisy chained” to optimize the array layout, two or even three cables may be connecting to the switchgear, and typically one cable will exit the switchgear up towards a transformer, and further to the wind turbine converter.

[0007] Another approach in the prior art involves a class of FOWTs in which the entire floating support structure can weathervane to align itself to the incoming wind, waves and currents. For this type of FOWT, the conventional arrangement is no longer valid because there needs to be a way to accommodate the unrestricted yaw motion of the floater without damaging the electrical cable. Most proposed solutions include some variation of a yaw bearing system plus an external rotatable electrical connector (i.e. not being an integral part of the connecting system, but being configured as an element being external to the floating support structure) sometimes using a simple junction box as connection element for the submarine cables. In some designs, the combined electrical power of potentially 5 or 6 FOWT systems may be going through the rotatable electrical connector, so a failure of one of these systems may leave several FOWT units out of service for a prolonged time until the issue can be fixed, which in a worst-case scenario requires towing a FOWT to shore, which may then leave the downstream FOWT units also disconnected for a prolonged time, unable to produce electricity. Additionally, high-voltage, compact slip-rings working at 66 kV or more are relatively new technology with significant complexity and potential reliability issues (which would be exacerbated by having to operate below water level). It is possible to have a switchgear directly as the connection point for the submarine cable so that at least the slip-ring itself is electrically protected, but then the switchgear itself may become the reliability weak point, and again be in an inconvenient position for maintenance, to the point that substitution of a failed switchgear can be very complex, if at all possible.

[0008] In the prior art related to weathervaning offshore wind turbines, a critical challenge that remains suboptimally addressed is the efficient cooling of the transformer (e.g. voltage transformers), when they are arranged in the connection zone between a weathervaning floating support structure with a wind turbine and a pre-laid mooring system. Transformers are components of offshore wind turbine systems that are responsible for converting a generated electrical power to be transmitted through submarine cables. However, the harsh and corrosive marine environment presents unique challenges for maintaining the optimal operating temperature of these transformers.

[0009] Given the inherent disadvantages associated with these prior art solutions, an evident need remains for an improved connecting system that addresses these challenges, while concurrently providing a reduction of the structural complexity of the connecting systems, an improved accessibility of parts subject to maintenance operations, as well as an improvement in the reliability and robustness of the overall connecting system in the context of FOWT systems configurations.

[0010] SUMMARY OF THE INVENTION

[0011] The present invention aims to provide connecting system that eliminates the above-mentioned problems, reducing complexity, and greatly improving reliability and serviceability of the FOWT system / array. A first aspect of the invention refers to a connecting system for connecting a weathervaning floating offshore support structure of a wind turbine to a pre-laid mooring system (also referred to as prelaid mooring structure). A pre-laid mooring system, in the context of offshore wind turbines, is a set of anchors, chains, and other components that are installed on the seabed prior to the deployment of the wind turbine structure. This system is used to secure and stabilize floating offshore wind turbines in their designated locations, allowing them to generate electricity efficiently and safely, even in deepwater environments. A non-limiting example of pre-laid mooring system is represented by tension leg platforms TLP, wherein a plurality of mooring lines (e.g. three or more) are tensioned to provide the necessary stability and support for the weathervaning floating offshore support structure of a wind turbine, thereby the TLP being configured to remain in a static or quasi-static position. Proper tensioning ensures that the turbine remains in its intended position and can withstand the dynamic forces exerted by the marine environment. However, the pre-laid mooring system is also compatible with other configurations, such as with a catenary configuration.

[0012] The weathervaning floating offshore support structure according to the invention may comprise one or more wind turbines and may be configured according to a plurality of configurations. In a preferred configuration, the weathervaning floating offshore support structure comprises a pivot column configured to be connected to the pre-laid mooring system by means of a connecting system according to the first aspect of the invention. The weathervaning floating offshore support structure may be configured as a polygonal (e.g. triangular) floating base comprising a plurality of vertices (e.g. three vertices in the case of the triangular configuration), wherein the pivot column may be arranged at one of the vertices.

[0013] The connecting system of the first aspect of the invention comprises a turret element and a slipring connector. The turret element comprises: a base, a support element, a columnar body and a bearing system. The base and the columnar body may be connected such that there is no relative rotation between them (i.e. they may be rigidly / solidly connected to each other).

[0014] The base is configured to be solidly (also referred to as “statically” or “rigidly”, i.e. such that the base -and preferably also the rest of the turret element- is configured to remain static relative to the pre-laid mooring system) connected to the pre-laid mooring system. The term solidly / statically is to be interpreted in the context of the present invention as defining a connection between the base and the pre-laid mooring system configured to prevent relative rotations between the base and the pre-laid mooring system (e.g. as a result of any relative rotation of the weathervaning floating offshore support structure of a wind turbine with respect to the pre-laid mooring system). This solid connection is also compatible with providing one or more elastic elements (optional) in the connection between the base and the pre-laid mooring system to improve the adjustment between these two elements, and also with configuring the base to be selectively connected to and disconnected from the pre-laid mooring system. In this regard, the base of the turret element may be configured to selectively interact with a connecting part of the pre-laid mooring system, such that the base may be configured to be selectively connected to and disconnected from the connecting part of the pre-laid mooring system.

[0015] The support element comprises a switchgear supported by the support element, wherein the switchgear is configured to be connected to one or more submarine cables and to receive by cable connection a power generated by a generator of the wind turbine. The support element may comprise (or may be configured as) a table or platform on which the switchgear may be arranged.

[0016] The one or more submarine cables are external to the connecting system (also referred to as connecting device). These submarine cables may be used to transmit the electrical power generated by offshore wind turbines to the shore or to substations, to interconnect multiple wind turbines located at a distance from each other or to import power from the mainland to the offshore facilities, especially in cases where energy storage or backup power is needed. Thus, at least some these submarine cables are configured to carry the electricity produced by the wind turbines, allowing it to be integrated into the electrical grid for distribution. Accordingly, the one or more submarine cables configured to be connected to the switchgear may comprise at least one submarine cable configured to receive (e.g. through an indirect connection with an intermediate connecting interface(s) - e.g. going through the slip-ring) the power generated by the generator of the at least one wind turbine of the weathervaning floating offshore support structure (this cable is often referred to as export cable and may comprise three phases, each with a respective terminal). The one or more submarine cables may also comprise other submarine cables for interconnection with other external electrical elements such as substations or other wind turbines.

[0017] The switchgear may be configured to provide high-voltage protection to the entire FOWT system comprising the connecting system according to the first aspect of the invention. Further, the switchgear may be configured to provide the protection while maintaining electrical continuity to any downstream external electrical unit connected to the switchgear by means of the one or more submarine cables. Thus, in case of having, for example, one or more external FOWT systems connected to the switchgear, then even when the wind turbine of the FOWT system in which the connecting system of the first invention is installed has to be serviced for maintenance, the switchgear is configured to ensure said electrical continuity for the external FOWT systems (e.g. connected in series to each other by means of the switchgear of the connecting system). The columnar body is configured to extend (e.g. longitudinally along a vertical direction when the turret element is in an operating position, i.e. when the turret element is arranged to effectively connect the weathervaning floating offshore support structure to the pre-laid mooring system) from the base to the support element. The columnar body comprises an inner passage configured to house the one or more submarine electrical cables intended to be connected to the switchgear of the support element. Preferably, the columnar body may be configured to be solidly connected to the base of the turret element, such that the columnar body remains in a static position relative to the base of the turret element.

[0018] The bearing system is configured to connect the turret element (preferably the columnar body of the turret element) to the weathervaning floating offshore support structure, such that the weathervaning floating offshore support structure is rotatable relative to the pre-laid mooring system to align the wind turbine to an incoming wind.

[0019] It should be noted that the support element may be configured to be an integral part of the columnar body or may be configured to be connectable to the columnar body. The support element may be connected to the columnar body, e.g. solidly connected, such that the support element remains in a same predetermined position (i.e. static) relative to the columnar body when the weathervaning floating offshore support structure rotates relative to the pre-laid mooring system (i.e. the support element is static relative to the pre-laid mooring system).

[0020] A problem related to bearing systems in the context of offshore wind turbines is that undesired frictions in the bearing system may end up causing a "stick-slip" phenomenon, which refers to a type of friction-induced motion that can occur in the bearing system. Stick-slip is a phenomenon that occurs when two surfaces are in contact, and they tend to stick together due to friction. When an external force, such as an incoming wind, tries to overcome this static friction and move one surface relative to the other (e.g. the weathervaning floating offshore support structure relative to the pre-laid mooring system), the surfaces suddenly "slip" and may move in ajerky or discontinuous manner. This jerky motion can result in vibrations, noise, and increased wear and tear on the components of the bearing system.

[0021] To solve this problem, the support element may further comprise an energy dissipation system comprising one or more spring-damper elements (e.g. elastomers and / or dampening elements), wherein the support element may be connected to the columnar body by means of the energy dissipation system, wherein the energy dissipation system may be configured as a filter of mechanical torsional vibration between the columnar body and the support element. Thus, the energy dissipation system may be interpreted as a device configured to filter mechanical torsional vibrations (e.g. vibrations or accelerations resulting from a stick-slip phenomenon in the bearing system) between the turret element (i.e. the columnar body of the turret element) and the weathervaning floating offshore support structure to protect the support element (i.e. such that said torsional accelerations / vibrations are minimised before reaching the support element).

[0022] Accordingly, the energy dissipation system may comprise one or more spring-damper elements and may be configured such that, when rotation of the weathervane floating offshore support structure relative to the pre-laid mooring system causes a mechanical torsional vibration to be transmitted to the columnar body (e.g. as a result of a stick-slip phenomenon) by the bearing system, then the mechanical torsional vibration causes the one or more spring-damper elements to momentarily deform absorbing at least a part of said mechanical torsional vibration, thereby reducing the mechanical torsional vibration received by the support element. After said momentary elastic deformation, the one or more spring-damper elements recover their original shape such that the support element recovers its initial predetermined relative position with respect to the columnar body.

[0023] Therefore, the energy dissipation system may be configured to connect the support element to the columnar body such that both element remain in a same static position relative to each other (e.g. when the weathervane floating offshore support structure rotates with respect to the pre-laid mooring system), but wherein the one or more spring-damper elements provide an elastic (e.g. temporal) torsional deformation in the connection between the support element and the columnar body in response to mechanical torsional vibration caused by the rotation of the weathervane floating offshore support structure with respect to the pre-laid mooring system. The one or more spring-damper elements may be configured to have an elastic deformation that is proportional to the mechanical torsional vibration received by the columnar body. In this configuration, the springdamper elements may be configured to have low deformation when the torsional acceleration of the columnar body is low, but significant deformation and energy absorption would occur in the spring-damper elements when the columnar body experiences high mechanical torsional vibrations (e.g. high torsional accelerations), thereby protecting any equipment mounted on the support element, and recovering its initial predetermined relative position with respect to the columnar body in the absence of torsional acceleration therein. All the above-described configurations for the support element are broadly compatible with all the embodiments of the invention.

[0024] The slip-ring connector comprises a first connecting part and a second connecting part (e.g. the two parts may be configured to slide relative to each other while maintaining electric contact between them; e.g. by each connecting part being respectively configured as a sliding ring, both sliding rings of them being in contact to each other and allowed to slip relative to each other). The first connecting part is configured to be connected to one or more cables configured to carry the power generated by the generator of the wind turbine, wherein these cables may be configured to be directly (i.e. without intermediate elements) or indirectly (i.e. with intermediate elements, such as a voltage transformer) connected to the generator of the wind turbine (it should be noted that the weathervaning floating offshore support structure may comprise a plurality of wind turbines each of which may comprise a respective generator, so that the slip-ring may also be configured to be connected to all the generators of the plurality of wind turbines). The second connecting part is configured to be cable-connected to the switchgear (i.e. such that the switchgear receives the power generated by the generator of the wind turbine (e.g. to then export it to at least one of the one or more submarine cables). The first part is also configured to be rotatable relative to the prelaid mooring system together with the weathervaning floating offshore support structure, while the second connecting part is configured to remain in a same position relative to the pre-laid mooring system. Further, the slip-ring connector is configured such that the first connecting part and the second connecting part are in electric contact. Thus, electric contact between the first connecting part and the second connecting part is maintained when there is no relative rotation between said parts, but also even when there is a relative rotation between said first and second connecting parts. Preferably, the slip-ring connector is configured such that the relative rotation between the first and second connecting parts is relative to the same longitudinal axis about which the bearing system allows a relative rotation between the weathervaning floating offshore support structure and the pre-laid mooring system (i.e. the slip-ring may be aligned with the turret element)

[0025] The connecting system may be further configured such that, when the connecting system is effectively connecting (i.e. when the connecting system is in an operative position) the weathervaning floating offshore support structure of the wind turbine to the pre-laid mooring system, the support element is configured to be positioned / arranged substantially above a water level over which the weathervaning floating offshore support structure is arranged to float. This prevents electrical equipment from getting in contact with water in case of leaks. The bearing system may be configured to be watertight, however it is difficult to ensure that this feature is maintained throughout the lifetime of the connecting system. Preferably, the slip-ring connector may also be configured to be arranged above said water level when the connecting system is arranged in its operative position. More preferably, the slip-ring may be configured such that the distance from the slip-ring connector to the water level is greater than the distance from the support element and the water level (i.e. the slip-ring connector may be configured to be arranged farther from the water level than the support element; e.g. the slip-ring may be arranged above the location of the support element when the connecting system is arranged such that the turret element is vertically arranged).

[0026] In some embodiments, when the connecting system is arranged effectively connecting the weathervaning floating offshore support structure of the wind turbine to the pre-laid mooring system (i. when the connecting system in its operative position), the turret element may be arranged in a vertical position, such that the turret element extends vertically from the base to the support element (e.g. with the columnar body being also vertically disposed). Preferably, the columnar body may extend at least partially between the base and the support element; and / or the slip-ring connector may be configured to be arranged in a position being arranged above the turret element in a vertical direction.

[0027] The slip-ring connector may be configured to be movable aside from its position such that the support elements becomes accessible from above (i.e. from the top), so that any device / element (e.g. the switchgear and / or the voltage transformer) that is arranged at the support element may be removed by on-board or external lifting equipment such as a port r vessel crane, so that they can be substituted in case of failure.

[0028] The support element may comprise (or may be configured as) at least one walkable platform configured to support the switchgear. Preferably, the at least one walkable platform may be configured to be at least partially surrounded by an external walkable platform of the weathervaning floating offshore support structure (e.g. the external walkable platform may be integrated in the pivot column of the weathervaning floating offshore support structure) such that a person is allowed to walk between them. The external platform may be configured such that, when the weathervaning floating offshore support structure rotates relative to the pre-laid mooring system to align the wind turbine to an incoming wind, the external platform rotates together with the offshore support structure relative to the pre-laid mooring system and to the walkable platform of the support element.

[0029] The turret element may further comprise a junction box configured to connect the one or more submarine cables to the switchgear, wherein preferably the junction box may be arranged at the support element, e.g. close to the switchgear (e.g. the junction box may be configured to be preconnected to the switchgear). The fact of having a junction box (e.g. as an interface) for connecting the one or more submarine cables (e.g. such that they may be indirectly connected to the switchgear) makes it easier to the operation of connecting said cables, since the connectors on the switchgear itself might not be in a convenient position and the submarine cables are not easy to handle and it is better to keep them relatively straight. This is especially advantageous when the support element comprises at least one walkable platform, as previously described, since it is easier for an operator (i.e. a human worker) to established said connection.

[0030] According to some embodiments, the switchgear may be configured (e.g. dimensioned) to receive at least one submarine cable from each of a plurality of external electrical elements (i.e. external to the connecting system, to the weathervaning floating offshore support structure, to the pre-laid mooring system - i.e. external to the respective floating offshore wind turbine FOWT system). Further, the switchgear may be configured to maintain electrical continuity to any downstream external electrical element / unit connected to the switchgear by means of the respective submarine cables (such that this continuity can be maintained even when servicing / disconnecting for maintenance purposes the at least one wind turbine of the of the weathervaning floating offshore support structure). The plurality of external electrical elements may comprise: one or more external wind turbines (e.g. two); and / or one or more electrical external substations; and / or an external electrical connection hub; and / or one or more external electricity-consuming elements. In some embodiments, the switchgear may be configured as a connecting node (e.g. a common connecting node) between said different external electrical elements. More particularly, the plurality of external electrical elements may comprise any combination of two external electrical elements, namely: at least one external floating offshore wind turbine (also referred to as external wind turbine) and at least one electrical substation; at least one external floating offshore wind turbine and at least one electrical connection hub; at least one external floating offshore wind turbine and at least one electricity-consuming element; at least one electrical substation and at least one external electrical connection hub; at least one electrical substation and at least one electricity-consuming element; or at least one electrical connection hub and at least one electricity-consuming element.

[0031] This configuration of the switchgear is especially advantageous to use the connecting system for connecting several external electrical elements (e.g. several external wind turbines) in a “daisy chained” configuration (i.e. in a series configuration). In the context of offshore wind turbines, a "daisy chain" typically refers to a method of connecting multiple wind turbines or other electrical components together in a sequential manner to form a continuous electrical circuit. This term is often used in the context of interconnecting the electrical systems of offshore wind turbines within a wind farm or between the turbines and an offshore substation (or other external electrical element(s) connected thereto).

[0032] The connecting system may further comprise a voltage transformer configured to adapt the power generated by the generator of the wind turbine to a higher voltage going through the one or more submarine cables. Thus, the voltage transformer may be configured to be arranged at position of the connecting system between the generator and the switchgear, such that the switchgear receives the power generated by the generator of the wind turbine conveniently adapted to the higher voltage going through the one or more submarine cables. Preferably, the connecting system further comprises a housing configured to house the voltage transformer. The housing may be configured to be air-tight and / or water-tight, i.e. may be configured as a weather protective housing.

[0033] According to some embodiment, the voltage transformer may be arranged at the weathervaning floating offshore support structure so that the voltage transformer may be configured to be rotatable together with the weathervaning floating offshore support structure relative to the pre-laid mooring system. Further, the voltage transformer may also be configured to receive (e.g. by cableconnection) the power generated by the generator of the wind turbine, to adapt its voltage, and to provide (e.g. by cable-connection) said power with an adapted voltage to the first connecting part of the slip-ring connector. In other words, the voltage transformer may be configured to be connected between the generator of the wind turbine and the first connecting part of the slip-ring, such that the switchgear may be cable-connected to the second connecting part of the slip-ring connector to receive the adapted power.

[0034] In other embodiments, the voltage transformer may be arranged at the turret element (preferably, at the support element of the turret element - i.e. together with the switchgear) and may be cable- connected between the second connecting part of the slip-ring connector and the switchgear, such that the cable connection of the switchgear to the second connecting part of the slip-ring connector is provided / goes through the voltage transformer. Having the voltage transformer on the support element (so, on the turret element) means that the slip-ring connector would operate at a much lower voltage. Since slip-rings in the range of 400 to 10 kV or 20 kV (the typical range of generator voltages used for wind turbines) are very standard, well proven equipment, and also much smaller in size due to much lower electrical isolation requirements, this provides a big advantage in terms of reliability and equipment handling.

[0035] The housing may be configured as a fluid-cooled housing comprising a plurality of ducts / conduits, said plurality of ducts comprising a plurality of fluid ducts (configured to allow fluid circulation through the housing for cooling of the voltage transformer) and at least one further duct (e.g. a cable duct) for voltage transformer cables for cable-connecting the voltage transformer. Voltage transformer cables refers to any electric cable connecting the transformer with any other element of the connecting system (e.g. those cables connecting the voltage transformer to the switchgear and either to the second connecting part of the slip-ring connector or to the swivel assembly described below). The fluid ducts may comprise at least one fluid inlet and at least on fluid outlet. Note that in the case of a liquid-cooled transformer (as opposed to air-cooled) it may not be needed to have and additional housing enclosure for the transformer, since the transformer casing would already include the functionality provided by the housing in terms of facilitating and containing the flow of coolant fluid through the heat-exchanging surfaces of the transformer.

[0036] Preferably, the connecting system may further comprise a swivel stack assembly. The swivel stack assembly may be configured to be connected as a top element of the connecting system (e.g. together with the slip-ring connector). Thus, the swivel stack assembly may be connected to the support element or to any element being arranged at the support element (e.g. the voltage transformer and / or the housing of the voltage transformer). The swivel stack assembly may comprise a plurality of swivel sections stacked on top of each other, wherein the plurality of swivel sections are configured such that, when the weathervaning floating offshore support structure rotates relative to the pre-laid mooring system to align the wind turbine to an incoming wind, the swivel sections swivel relative (e.g. with unlimited rotation) to each other to provide a fluid passage (e.g. a continuous passage; also referred to as fluid / flow path or fluid / flow channel) for allowing a cooling fluid (e.g. a gas, such as air, or a liquid, such as water) for cooling the voltage transformer to go through the swivel stack assembly (e.g. to circulate from a fluid-cooling system towards the fluid-cooled housing).

[0037] In some embodiments, the connecting system may be configured such that the cooling fluid going through the swivel stack assembly is then directly circulated through the fluid-cooled housing of the voltage transformer. In other embodiments, the connecting system may be configured such that a first cooling fluid circulates through the swivel stack assembly and a second cooling fluid circulates through the fluid-cooled housing, such that the connecting system further comprises an intermediate heat exchanger (e.g. which may be regarded as a fluid-cooling system) configured to transmit heat between the second and the first cooling fluids.

[0038] The fluid-cooling system (.e. the device from which the cooling fluid passing through the swivel stack assembly is supplied) may be configured as a general heat exchanger system (e.g. arranged at the weathervaning offshore support structure). In some embodiments, the fluid-cooling system may be configured to renew the air inside the housing of the voltage transformer by means of an exchange with the outside (e.g. by the fluid cooling system comprising a forced air system, such as one or more fans configured to cause a circulation of air between the inner of the housing and an outside - i.e. air being from outside the weathervaning floating offshore wind turbine 200 and outside the pre-laid mooring system 300). Preferably, the swivel sections may also be configured to swivel relative to each other to additionally provide a passage for at least a part of the voltage transformer cables configured to receive by cable-connection the power generated by the generator of the wind turbine (e.g. from the second connecting part of the slip-ring connector).

[0039] The swivel stack assembly may be configured to be substantially coaxial with the bearing system of the turret element and with the slip-ring connector (e.g. with a central axis of the turret element, which is also a central axis of the columnar body). This facilitates servicing these units. In some cases also this will allow pulling-in the submarine electrical cables, if this is done using a winch that can be conveniently pulling from an upper deck. The swivel stack assembly and / or the slip-ring connector may be configured to be movable aside (out of the central axis) through an adequate auxiliary structural system. Accordingly, the swivel stack assembly and / or the slip-ring connector may be configured to interact with an auxiliary structural system of the connecting system and / or of the weathervaning floating offshore support structure, such that the swivel stack assembly and / or the slip-ring connector become movable aside the central axis of the columnar body. Preferably, the auxiliary structural system may comprise (or may be configured as) one or more rails and / or one or more hinges and / or one or more flexible joints configured to interact with the swivel stack assembly and / or with the slip-ring connector. Thus, the support element may be configured, such that when the swivel stack assembly and / or the slip-ring are moved aside, the support element is accessible from the top, so that any device / element (e.g. the switchgear and / or the voltage transformer) that is arranged at the support element may be removed by on-board or external lifting equipment such as a port or vessel crane, so that they can be substituted in case of failure. It should be noted that in those embodiments not having any swivel stack assembly, the slip-ring connector may be configured to be movable aside from the central axis of the columnar body according to the description provided. In those embodiments in which both the swivel stack assembly and the slip-ring connector are movable aside, the auxiliary structural system may be configured as a single system common for both devices.

[0040] The slip-ring connector may preferably be configured as an integral part of the swivel stack assembly. However, in some embodiments, the slip-ring connector and the swivel stack may be configured as independent elements, both of them arranged above the position of the support element.

[0041] A second aspect of the invention refers to a floating offshore wind turbine FOWT system comprising: a pre-laid mooring system, a weathervaning floating offshore support structure comprising at least one wind turbine, one or more submarine cables, and a connecting system according to any of the preceding described embodiments, wherein the connecting system is configured to connect the weathervaning floating offshore support structure to the pre-laid mooring system, such that the weathervaning floating offshore support structure is rotatable relative to the pre-laid mooring system to align the wind turbine to an incoming wind.

[0042] The pre-laid mooring system may be configured as a tension leg platform TLP, wherein a plurality of mooring lines (e.g. three or more) are tensioned to provide the necessary stability and support for the weathervaning floating offshore support structure of a wind turbine, thereby the TLP being configured to remain in a static or quasi-static position. In preferred embodiments.

[0043] The weathervaning floating offshore support structure may comprise one or more wind turbines and may be configured according to a plurality of configurations. In a preferred configuration, the weathervaning floating offshore support structure comprises a pivot column configured to be connected to the pre-laid mooring system by means of the connecting system according to the first aspect of the invention. Thus, the pivot column may be configured to have an inner space to receive the connecting system. The weathervaning floating offshore support structure may be configured as a polygonal (e.g. triangular) floating base comprising a plurality of vertices (e.g. three vertices in the case of the triangular configuration), wherein the pivot column may be arranged at one of the vertices.

[0044] The one or more submarine cables may be configured to be connected to the switchgear and may comprise at least one submarine cable to receive the power generated by the generator of the at least one wind turbine of the weathervaning floating offshore support structure (this cable may comprise three phases, each with a respective terminal). The one or more submarine cables may also comprise other submarine cables for interconnection with other external electrical elements such as substations or other wind turbines.

[0045] The connecting system according to the first aspect of the invention is configured to provide both a mechanical and an electrical connection between the weathervaning floating offshore support structure and the pre-laid mooring structure, according to the above-provided description for the first aspect of the invention.

[0046] The support element may comprise (or may be configured as) at least one walkable platform configured to support the switchgear of the connecting system. Preferably, the at least one walkable platform may be configured to be at least partially surrounded by an external walkable platform of the weathervaning floating offshore support structure (e.g. the external walkable platform may be integrated in the pivot column of the weathervaning floating offshore support structure) such that a person is allowed to walk between them. Thus, the weathervaning floating offshore support structure may comprise an external platform configured such that, when the weathervaning floating offshore support structure rotates relative to the pre-laid mooring system to align the wind turbine to an incoming wind, the external platform rotates together with the offshore support structure relative to the pre-laid mooring system and to the walkable platform of the support element.

[0047] A third aspect of the invention refers to an interconnected system comprising: a floating offshore wind turbine FOWT system according to the second aspect of the invention (i.e. comprising a connecting system according to the first aspect of the invention); and a plurality of external electrical elements configured to be connected by means of respective submarine cables to the switchgear of the connecting system of the floating offshore wind turbine FOWT system.

[0048] The plurality of external electrical elements may comprise: one or more external wind turbines (e.g. two); and / or one or more electrical external substations; and / or an external electrical connection hub; and / or one or more external electricity-consuming elements. In some embodiments, the switchgear may be configured as a connecting node (e.g. a common connecting node) between said different external electrical elements (e.g. for connecting one or more external FOWT system to the FOWT system of the second aspect of the invention, wherein preferably this connection may be configured as a “daisy chained” configuration). More particularly, the plurality of external electrical elements may comprise any combination of two external electrical elements according to the above provided list of combinations.

[0049] The plurality of external electrical elements may be configured to be connected in series or in parallel or in a combination thereof.

[0050] BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Fig. 1 depicts a general view of a generic floating offshore wind turbine (FOWT) system 500 according to a second aspect of the invention comprising: a pre-laid mooring system 300, a weathervaning floating offshore support structure 200 comprising a wind turbine 201 and a connecting system 100 according to any of the embodiments of the first aspect of the invention.

[0052] Fig. 2 shows a connecting system 100 of the first aspect of the invention according to a first embodiment.

[0053] Fig. 3 shows a connecting system 100 of the first aspect of the invention according to a second embodiment. Fig. 4. Shows a connecting system 100 of the first aspect of the invention according to a third embodiment.

[0054] Fig. 5 depicts a connecting system 100 of the first aspect of the invention according to a fourth embodiment.

[0055] Figs. 6A-6C shows three single-line wiring diagrams of the electrical connections of the embodiments depicted in Figs. 2-5.

[0056] Fig. 7 shows an interconnected system according to a third aspect of the invention.

[0057] DETAILED DESCRIPTION OF THE DRAWINGS

[0058] Fig. 1 depicts a general view of a generic floating offshore wind turbine (FOWT) system 500 comprising: a pre-laid mooring system 300, a weathervaning floating offshore support structure 200 comprising a wind turbine 201 , and a connecting system 100 according to any of the embodiments of the first aspect of the invention, wherein the connecting system 100 is configured to connect the weathervaning floating offshore support structure 200 to the pre-laid mooring system 300, such that the weathervaning floating offshore support structure 200 is rotatable relative to the pre-laid mooring system 300 to align the wind turbine 201 to an incoming wind. The FOWT system 500 of Fig. 1 is broadly compatible with any of the arrangements shown in any of Figs. 2-5 below.

[0059] Fig. 1 represents the pre-laid mooring system 300 as a tension leg platform. However, this pre-laid mooring system 300 is also compatible with other configurations, such as with a catenary configuration. The weathervaning floating offshore support structure 200 is also compatible with a plurality of configurations. In a preferred embodiment, the weathervaning floating offshore support structure 200 comprises a wind turbine 201 connected to the rest of the weathervaning floating offshore support structure 200 by means of a tripod structure which is connected to a base of the weathervaning floating offshore support structure 200, said base being configured as a triangular base (i.e. a horizontally arranged triangular base structure). The weathervaning floating offshore support structure 200 may also comprise a plurality of wind turbines 201.

[0060] The connecting system 100 provides a mechanical connection between the weathervaning floating offshore support structure 200 and the pre-laid mooring system 300, but also an electrical connection between one or more submarine cables 400 and the weathervaning floating offshore support structure 200, such that a power generated by a generator of the wind turbine 201 is allowed to be transmitted outside the FOWT system 500. The weathervaning floating offshore support structure 200 is configured to float on water such that at least a part of said structure 200 is above a water level W. With illustrative purposes, the part of the weathervaning floating offshore support structure 200 that is configured to be connected to the pre-laid system 300 by means of the connecting system 100 has been identified as a pivot column 204.

[0061] Fig. 2 depicts a first embodiment of the connecting system 100 of the first aspect of the invention which is compatible with the FOWT system of Fig. 1. The connecting system 100 of Fig. 2 comprises a turret element 1 and a slip-ring 6. The turret element 1 comprises: a base 2, a support element 3, a columnar body 4 and a bearing system 5.

[0062] The base 2 is configured to be solidly connected to the pre-laid mooring system 300, i.e. such that the base 2 (and therefore the turret element 1) remains in a static (or quasi-static) position relative to the pre-laid mooring system 300. Although not shown in Fig. 1 , this solid connection is also compatible with providing one or more elastic elements (optional) in the connection between the base 2 and the pre-laid mooring system 300 to improve the adjustment between these two elements. Thus, the base 2 of Fig. 2 is also configured (optional feature) to be selectively connect to and disconnected from the pre-laid mooring system 300. In this regard, the base 2 of the turret element 1 may be configured to selectively interact with a connecting part 301 of the pre-laid mooring system 300, such that the base 2 may be configured to be selectively connected to and disconnected from the connecting part 301 of the pre-laid mooring system 300.

[0063] The support element 3 comprises a switchgear 31 supported by the support element 3, wherein the switchgear 31 is configured to be connected to the one or more submarine cables 400 and to receive by cable connection a power generated by a generator of the wind turbine 201 . The support element 3 of Fig. 2 is shown (optional feature) as comprising (or being configured as) a walkable platform configured to support the switchgear 31.

[0064] The columnar body 4 is configured to extend from the base 2 to the support element 3. The columnar body 4 comprises an inner passage 41 configured to house the one or more submarine cables 400 to allow the connection of said one or more submarine cables 400 to the switchgear 31 of the support element 3.

[0065] The bearing system 5 is configured to connect the turret element 1 (preferably the columnar body 4 of the turret element 1) to the weathervaning floating offshore support structure 200, such that the weathervaning floating offshore support structure 200 is rotatable relative to the pre-laid mooring system 300 to align the wind turbine 201 to an incoming wind. In Fig. 2, the part of the weathervaning floating offshore support structure 200 that is configured to be connected to the turret element 1 by means of the bearing system 5 is represented as the pivot column 204.

[0066] Although is not visible in Fig. 2, the support element 3 is compatible with a plurality of configurations. Thus, the support element 3 may be configured as an integral part of the columnar body 4 or may be configured to be connectable to the columnar body 4. The support element 3 may be connected to the columnar body 4 such that the support element 3 remains in a same predetermined position (i.e. static) relative to the columnar body 4 when the weathervaning floating offshore support structure 200 rotates relative to the pre-laid mooring system 300. The support element may further comprise the energy dissipation system comprising one or more springdamper elements described in the summary of the invention.

[0067] The slip-ring connector 6 comprises a first connecting part 61 and a second connecting part 62 (the two parts may be configured to slide relative to each other while maintaining electric contact between them). In Fig. 2 (and also in Figs. 3-5), the slip-ring is schematically represented such that the first connecting part 61 is represented as a first sliding ring and the second connecting part 62 is represented as a second sliding ring (the sliding condition is represented by schematic bearing - see X-marked area - between the two connecting parts 61 , 62). The first connecting part 61 is configured to be connected to one or more cables 202 configured to carry the power generated by the generator of the wind turbine 201. In Fig. 2, since the generator of the wind turbine 201 is not shown, these cables 202 are represented as comprising three terminals intended to receive (i.e. by stablishing a proper connection) the power generated by the generator of the wind turbine 201. These cables 202 may be configured to be directly (i.e. without intermediate elements) or indirectly (i.e. with intermediate elements, such as a voltage transformer) connected to the generator of the wind turbine 201 (it should be noted that the weathervaning floating offshore support structure may comprise a plurality of wind turbines each of which may comprise a respective generator, so that the slip-ring 6 may also be configured to be connected to all the generators of the plurality of wind turbines). The second connecting part 61 is configured to be cable-connected to the switchgear 31 (i.e. such that the switchgear 31 receives the power generated by the generator of the wind turbine). The first part 61 is also configured to be rotatable relative to the pre-laid mooring system 300 together with the weathervaning floating offshore support structure 200, while the second connecting part 62 is configured to remain in a same position relative to the pre-laid mooring system 300. Further, the slip-ring connector 6 is configured such that the first connecting part 61 and the second connecting part 62 are in electric contact. Thus, electric contact between the first connecting part 61 and the second connecting part 62 is maintained when there is no relative rotation between said parts, but also even when there is a relative rotation between said first 61 and second 62 connecting parts.

[0068] The connecting system 100 is also configured such that, when the connecting system 100 is effectively connecting (i.e. when the connecting system is in an operative position as shown in Fig. 2) the weathervaning floating offshore support structure 200 of the wind turbine 201 to the pre-laid mooring system 300, the support element 3 is configured to be positioned / arranged above a water level (see W in Fig. 1) over which the weathervaning floating offshore support structure 200 is arranged to float. This is an optional feature of the invention. Fig. 2 shows the preferred configuration in which, the slip-ring connector 6 is also configured to be arranged above said water level W when the connecting system 100 is arranged in its operative position. In particular, in Fig. 2, the slip-ring connector 6 is configured such that the distance from the slip-ring connector 6 to the water level W is greater than the distance from the support element 3 and the water level W (i.e. the slip-ring connector 6 is configured to be arranged farther from the water level W than the support element 3). In the configuration shown in Fig. 2, the turret element 1 is vertically arranged, and the slip-ring connector 6 in arranged above the position support element 3 of the turret element 1 (i.e. the slip-ring connector 6 is not supported by the support element 3, but it is arranged at a higher position).

[0069] Further, the turret element 1 of Fig. 2 is configured to be arranged in a vertical position (i.e. vertically) in its operative position. The turret element 1 extends vertically from the base 2 to the support element 3 (e.g. with the columnar 4 body being also vertically disposed).

[0070] Although it is not visible in Fig. 2, the turret element 1 may further comprise a junction box configured to connect the one or more submarine cables 400 to the switchgear 31 , wherein preferably the junction box may be arranged at the support element.

[0071] The switchgear 31 of Fig. 2 may optionally be configured to (e.g. dimensioned) to receive at least one submarine cable 400 from each of a plurality of external electrical elements (not visible in Fig. 2). The plurality of external electrical elements may comprise: one or more external wind turbines (e.g. two); and / or one or more electrical external substations; and / or an external electrical connection hub; and / or one or more external electricity-consuming elements. In some embodiments, the switchgear may be configured as a connecting node (e.g. a common connecting node) between said different external electrical elements.

[0072] Fig. 3 depicts a second embodiment of the connecting system 100 of the first aspect of the invention which is compatible with the FOWT system of Fig. 1. The embodiment depicted in Fig. 3 is based on the first embodiment of Fig. 2 but further comprises a voltage transformer. It should be noted that those features that have been described as optional features of Fig. 2 are also optional features for the embodiment of Fig. 3. Further, Fig. 3 is shown as showing an optional configuration in which the walkable platform 32 (i.e. the at least one walkable platform 32) is configured to be at least partially surrounded by an external walkable platform 203 of the weathervaning floating offshore support structure 200 (e.g. the external walkable platform may be integrated in the pivot column 204) such that a person is allowed to walk between them. This feature is also compatible with any of the embodiments of Figs. 2, 4 and 5.

[0073] Thus, in the of Fig. 3, the connecting system 100 further comprises a voltage transformer 7 configured to adapt the power generated by the generator of the wind turbine 201 (visible in Fig. 1 but not in Fig. 3) to a higher voltage going through the one or more submarine cables 400. Thus, the voltage transformer 7 may be configured to be arranged at position of the connecting system 100 between the generator (i.e. the generator of the wind turbine 201 , which is not a part of the connecting system 100) and the switchgear 31 , such that the switchgear 31 receives the power generated by the generator of the wind turbine 201 conveniently adapted to the higher voltage going through the one or more submarine cables 400. Preferably and optionally, the connecting system 100 further comprises a housing configured to house the voltage transformer 7, wherein said housing may be configured to be air-tight and / or water-tight.

[0074] Fig. 3 shows an optional configuration in which the voltage transformer 7 is arranged at the weathervaning floating offshore support structure 200 (in Fig. 3 the voltage transformer 7 is more particularly arranged within the optional pivot column 204 of the weathervaning floating offshore support structure 200) so that the voltage transformer 7 is configured to be rotatable together with the weathervaning floating offshore support structure 200 relative to the pre-laid mooring system 300. Further, the voltage transformer 7 is configured to receive by cable-connection the power generated by the generator of the wind turbine 201 of the weathervaning floating offshore support structure 200, to adapt its voltage, and to provide by cable-connection said power with an adapted voltage to the first connecting part 61 of the slip-ring connector 6. Thus, the voltage transformer 7 of Fig. 3 is configured to be connected between the generator of the wind turbine 201 and the first connecting part 61 of the slip-ring 6, while the switchgear 31 is cable-connected to the second connecting part 62 of the slip-ring connector 6 to receive said adapted power.

[0075] Fig. 4 depicts a third embodiment of the connecting system 100 of the first aspect of the invention which is compatible with the FOWT system of Fig. 1. The embodiment depicted in Fig. 4 is based on the first embodiment and second embodiments, but the voltage transformer 7 is arranged at a different position with respect to the second embodiment. It should be noted that those features that have been described as optional features of Figs. 2 and / or 3 are also optional features for the embodiment of Fig. 4.

[0076] In the embodiment of Fig. 4, the voltage transformer 7 is arranged at the turret element 1 (in particular, Fig. 4 depicts the optional configuration in which the voltage transformer 7 is arranged at the support element 3 of the turret element 1 - i.e. together with the switchgear 31) and is cable- connected between the second connecting part 62 of the slip-ring connector 6 and the switchgear 31. Thus, the cable connection of the switchgear 31 to the second connecting part 62 of the slipring connector 6 is provided (i.e. goes through) the voltage transformer 7. Therefore, according to this configuration, the power generated by the generator of the wind turbine 201 (not visible in Fig. 4, but visible in Fig. 1) reaches (e.g. through the one or more cables 202) the first connecting part 61 of the slip-ring connector 6, then said power is transmitted to the second connecting part 62 of the slip-ring connector 6 and is then transmitted to the voltage transformer 7 which adapts / transform its voltage to the higher voltage going through the one or more submarine cables 400. The power adapted by the voltage transformer 7 is then transmitted to the switchgear 31 , and from the switchgear 31 to at least one of the one or more submarine cables 400 (it should be noted that each of the one or more submarine cables may comprise several cables - e.g. three cables each with a phase). Having the voltage transformer 7 on the support element 3 (so, on the turret element) means that the slip-ring connector would operate at a much lower voltage. As previously disclosed, the connecting system 100 may optionally comprise a housing configured to house the voltage transformer 7.

[0077] Fig. 5 represents a fourth embodiment of the connecting system 100 of the first aspect of the invention which is compatible with the FOWT system of Fig. 1. The embodiment depicted in Fig. 5 is based on the third embodiment, but the voltage transformer 7 do have a housing (not visible in Fig. 5 due to the fact that Fig. 5 is a simplified schematic representation) and the connecting system 100 further comprises a swivel stack assembly 8. It should be noted that those features that have been described as optional features of Fig. 2 are also compatible optional features for the embodiment of Fig. 5.

[0078] The housing of the voltage converter 7 is configured as a fluid-cooled housing comprising a plurality of ducts / conduits 71 , said plurality of ducts 71 comprising a plurality of fluid ducts (configured to allow fluid circulation through the housing for cooling of the voltage transformer - e.g. at least one fluid inlet duct and at least one fluid outlet duct) and at least one further duct for voltage transformer cables for cable-connecting the voltage transformer (e.g. those cables for connecting the voltage transformer 7 to the switchgear 31 and to the second connecting part 62 of the slip-ring connector 6).

[0079] The swivel stack assembly 8 is configured to be connected as a top element of the connecting system 100. The swivel stack assembly 8 may comprise a plurality of swivel sections stacked on top of each other, wherein the plurality of swivel sections are configured such that, when the weathervaning floating offshore support structure 200 rotates relative to the pre-laid mooring system 300 to align the wind turbine 201 to an incoming wind, the swivel sections swivel relative to each other to provide a fluid passage towards for allowing a colling fluid for cooling the voltage transformer 7 to go through the swivel stack assembly 8. In this regard, Fig. 5 represents a schematic view of the inlet duct and the outlet duct arranged at the upper part of the block representing the voltage transformer 7 (in this case, this block may be interpreted as representing the housing of the voltage transformer 7). These two ducts are then connected to the swivel stack assembly 8 which, as previously described provide a respective path for each duct (e.g. a continuous path) irrespectively of the relative position of the weathervaning floating offshore support structure 200 with respect to the pre-laid mooring system 300.

[0080] Fig. 5 shows an optional configuration in which two respective auxiliary ducts 205 are connected to the swivel stack assembly 8 as a continuation towards an outside of the weathervaning floating offshore support structure 200 (represented, in Fig. 5, by the pivot column 204) of said respective paths provided by the swivel stack assembly 8. The auxiliary ducts 205 are regarded as being static relative to the weathervaning floating offshore support structure 200 (i.e. the auxiliary ducts 205 are configured to rotate together with the weathervaning floating offshore support structure 200 relative to the pre-laid mooring system 300). It should be noted that this particular embodiment shows only one of the solutions described in the summary of the invention, namely the one in which air is forced (the vents are not shown) to circulate from outside the weathervaning floating offshore support structure to the voltage converter. However, the rest of the solutions described are also compatible with the embodiment of the figures (e.g. the use of an intermediate heat exchanger as previously described).

[0081] Although not visible in the figures, the swivel stack assembly 8 and / or the slip-ring 6 connector may be configured to interact with an auxiliary structural system of the connecting system 100 and / or of the weathervaning floating offshore support structure 200, such that the swivel stack assembly 8 and / or the slip-ring connector 6 become movable aside a central axis of the columnar body 4. Preferably, the auxiliary structural system may comprise (or may be configured as) one or more rails and / or one or more hinges and / or one or more flexible joints configured to interact with the swivel stack assembly 8 and / or with the slip-ring connector 6. This configuration is compatible with any of the embodiments of Figs. 2-4 (i.e. for those embodiments not having any swivel stack assembly 8, the system is applicable only to the slip-ring connector 6).

[0082] The slip-ring connector 6 of Fig. 5 may preferably be configured as an integral part of the swivel stack assembly 8. In an alternative embodiment, the slip-ring connector 6 and the swivel stack 8 may be configured as independent elements, both of them arranged above the position of the support element 3.

[0083] Figs. 6A-6C shows three single-line wiring diagrams of the electrical cable-connections of the embodiments depicted in Figs. 2-5. In all three Figs. 6A-6C a doted line separates a part A from a part B. Part A represents those elements that are configured to be fixed, i.e. to remain in a same relative position with respect to the pre-laid mooring system 300 (i.e. to be statically arranged relative to the pre-laid mooring structure 300). Part B represents those elements that are configured to be movable together with the weathervaning floating offshore structure 200 relative to the prelaid mooring structure 300. In this regard, it is noted that the slip-ring 6 comprises a first connecting portion 61 which belongs to part A, and a second connecting part 62 which belongs to part B.

[0084] The elements depicted in Figs. 6A-6C are compatible with being operated at a plurality of voltages. Thus, for example, the one or more submarine cables and the switchgear 31 are normally configured to operate at voltages in the range 20 to 127 kV, wherein 33 and 66 kV are specific compatible values within said range (this is often expressed as a 20 / 33 / 66 / 127 kV). The generator of the wind turbine 201 normally produces power in the range 0.4 to 20 kV, wherein the range 3.3 to 10 kV is also common.

[0085] Fig. 6A represents a single-line wiring diagram of the embodiment depicted in Fig. 2. In particular, Fig. 6A shows that the one or more submarine cables 400 are connected to the switchgear 31 , which is then connected to the first connecting part 61 of the slip-ring connector 6. Then the second connecting part 62 of the slip-ring connector 6 is connected to receive the power generated by the generator of the wind turbine 201. In this embodiment there is no voltage transformer, so that the voltage of the power generated by the generator of the wind turbine 201 is not adapted to the voltage going through the one or more the submarine cables 400. Therefore, this configuration is useful when there is no need to adapt the voltage because the voltage of the power generated by the generator of the wind turbine 201 is already compatible with the voltage going through the one or more submarine cables 400. Fig. 6B shows a single-line wiring diagram of the embodiment of Fig. 3. In this embodiment, the one or more submarine cables 400 are connected to the switchgear 31 , which is in turn connected to the first connecting part 61 of the slip-ring connector 6. Then, the second connecting part 62 of the slip-ring connector 6 is connected to the voltage transformer 7, which is in turn connected to receive the power generated by the generator of the wind turbine 201. Thus, the voltage transformer 7 is arranged / connected between the slip-ring connector 6 and the generator of the wind turbine 201 , so that the voltage transformer 7 is configured to adapt the voltage of the power generated by the generator of the wind turbine 201 to the higher voltage going through the submarine cables 400. It should be noted that, in this configuration the slip-ring connector 6 is required to work in the higher voltage of the one or more submarine cables 400, so that it has to be sized to withstand said voltage. Accordingly, the voltage transformer 7 comprises a first winding (connected to the second connecting part 62 of the slip-ring connector 6, and configured to operate as the secondary of the voltage transformer 7) configured to operate at the voltage of the one or more submarine cables (e.g. 20 / 33 / 66 / 127 kV, i.e. in the range 20 to 127 kV, such as at 33 or 66 kV) and a second winding (connected to receive the voltage of the power generated by the generator of the wind turbine 201 , and configured to operate as the primary of the voltage transformer 7) configured to operate at a voltage corresponding with that of the power generated by the generator of the wind turbine 201 (e.g. in the range 0.4 to 20 kV, such as at 0.4 or 3.3 or 10 kV).

[0086] Fig. 6C represents a single-line wiring diagram compatible with the embodiments depicted in Figs. 4 and 5 (the presence of the swivel stack assembly 8 in the embodiment of Fig. 5 does not affect the electrical connection of the slip-ring connector 6). In these two embodiments, the one or more submarine cables 400 are connected to the switchgear 31 , which is in turn connected to the voltage transformer 7. The voltage transformer 7 is also connected to the first connecting part 61 of the slip-ring connector 6, while the second connecting part 62 of the slip-ring connector 6 is then connected to receive the power generated by the generator of the wind turbine 201. It should be noted that this configuration is especially advantageous because the arrangement of the transformer in part A (e.g. on the support element 3) reduces the voltage at which the slip-ring connector 6 is required to operate, so that the slip-ring connector 6 is configured to operate at a much lower voltage (the voltage of the power generated by the generator of a wind turbine 201 is usually lower than the voltage going through the submarine cables 400). Thus, the slip-ring connector 6 requires much lower isolation requirements and is therefore much smaller in size, which is especially advantageous in offshore applications due to the required transport of all the elements to the location of the FOWT system and the necessary handling during installation of the system. In the diagram of Fig. 6C, the voltage transformer 7 comprises a first winding (connected to the switchgear 31 , and configured to operate as the secondary of the voltage transformer 7) configured to operate at the voltage of the one or more submarine cables (e.g. 20 / 33 / 66 / 127 kV, i.e. in the range 20 to 127 kV, such as at 33 or 66 kV) and a second winding (connected to the first connecting part 61 of the slip-ring connector 6 to receive the voltage of the power generated by the generator of the wind turbine 201 , and configured to operate as the primary of the voltage transformer 7) configured to operate at a voltage corresponding with that of the power generated by the generator of the wind turbine 201 (e.g. in the range 0.4 to 20 kV, such as at 0.4 or 3.3 or 10 kV).

[0087] Fig. 7 shows an interconnected system according to a third aspect of the invention comprising: a floating offshore wind turbine FOWT system 500 according to the second aspect of the invention; and a plurality of external electrical elements configured to be connected by means of respective submarine cables 400 to the switchgear 31 of the connecting system 100 of the floating offshore wind turbine system 500.

[0088] It should be noted that the floating offshore wind turbine FOWT system 500 of Fig. 7 is a FOWT system according to Fig. 1 , i.e. comprising: a pre-laid mooring system 300, a weathervaning floating offshore support structure 200 comprising a wind turbine 201 , and a connecting system 100 according to any of the embodiments of the first aspect of the invention. Therefore, the FOWT system 500 is compatible with a connecting system 100 of any of Figs. 2 to 5.

[0089] The plurality of external electrical elements is represented in Fig. 7 as a plurality (the plurality is optionally represented by two units, but in other cases the number of units may be greater) of external floating offshore wind turbines FOWT systems 500’, 500”. The three FOWT systems 500, 500’ and 500 are shown as being optionally connected in a “daisy chained” configuration / arrangement. However, it should be noted the invention is also compatible with other configuration such that configuring the switchgear 31 of the connecting system 100 of the FOWT system 500 as a common node for connecting at least a part of the external electrical elements in parallel.

[0090] Further, it should be noted that the plurality of external electrical elements may be configured to comprise (alternatively or complementarily to the external FOWT systems) one or more of: an electrical substation and / or an electrical connection hub and / or an electricity-consuming element.

[0091] In some embodiments, the plurality of external electrical elements may comprise any combination of two external electrical elements as previously listed in the summary of the invention.

Claims

CLAIMS1. A connecting system (100) for connecting a weathervaning floating offshore support structure (200) of a wind turbine (201) to a pre-laid mooring system (300), the connecting system (100) comprising: a turret element (1) comprising: a base (2) configured to be solidly connected to the pre-laid mooring system (300); a support element (3) comprising a switchgear (31) supported by the support element (3), wherein the switchgear (31) is configured to be connected to one or more submarine cables (400) and to receive by cable connection a power generated by a generator of the wind turbine (201); a columnar body (4) extending from the base (2) to the support element (3), the columnar body (4) comprising an inner passage (41) configured to house the one or more submarine electrical cables (400); and a bearing system (5) configured to connect the turret element (1), preferably the columnar body (4) of the turret element (1), to the weathervaning floating offshore support structure (200), such that the weathervaning floating offshore support structure (200) is rotatable relative to the pre-laid mooring system (300) to align the wind turbine to an incoming wind; and a slip-ring connector (6) comprising a first connecting part (61) and a second connecting part (62), wherein the first connecting part (61) is configured to be connected to one or more cables (202) configured to carry the power generated by the generator of the wind turbine (201), and the second connecting part (62) is configured to be cable-connected to the switchgear (31) such that the switchgear (31) receives the power generated by the generator of the wind turbine (201), wherein the first part (61) is configured to be rotatable relative to the pre-laid mooring system (300) together with the weathervaning floating offshore support structure (200), while the second connecting part (62) is configured to remain in a same position relative to the pre-laid mooring system (300), wherein electric contact between the first connecting part (61) and the second connecting part (62) is maintained when there is a relative rotation between the first (61) and the second (62) connecting parts.

2. The connecting system (100) of claim 1 , further configured such that, when the connecting system (100) is arranged effectively connecting the weathervaning floating offshore support structure (200) of the wind turbine to the pre-laid mooring system (300), the support element (3) is arranged above a water level (W) over which the weathervaning floating offshore support structurewherein preferably the slip-ring connector (6) is also configured to be arranged above said water level, wherein more preferably the slip-ring connector is arranged farther from the water level than the support element (3).

3. The connecting system (100) of any of the preceding claims, wherein: wherein the support element (3) is configured such that, when the weathervaning floating offshore support structure (200) rotates relative to the pre-laid mooring system (300) to align the wind turbine to an incoming wind, the support element (3) remains in a same predetermined position relative to the pre-laid structure (300); and / or wherein the support element (3) further comprises an energy dissipation system, wherein the support element (4) is connected to the columnar body (4) by means of the energy dissipation system, wherein the energy dissipation system comprises one or more spring-damper elements and is configured such that, when the rotation of the weathervane floating offshore support structure (200) relative to the pre-laid mooring system (300) causes a mechanical torsional vibration to be transmitted to the columnar body (4) by the bearing system (5), then the mechanical torsional vibration causes the one or more spring-damper elements to momentarily deform, thereby reducing the mechanical torsional vibration received by the support element (3).

4. The connecting system (100) of any of the preceding claims, wherein the support element(3) comprises at least one walkable platform (32) configured to support the switchgear (31); wherein preferably the at least one walkable platform (32) is configured to be at least partially surrounded by an external walkable platform (203) of the weathervaning floating offshore support structure (200) such that a person is allowed to walk between them, and wherein the external platform (203) is configured such that, when the weathervaning floating offshore support structure (200) rotates relative to the pre-laid mooring system (300) to align the wind turbine to an incoming wind, the external platform (203) rotates together with the offshore support structure (200) relative to the pre-laid mooring system and to the walkable platform (32) of the support element(4).

5. The connecting system (100) of any of the preceding claims, when the connecting system (100) is arranged effectively connecting the weathervaning floating offshore support structure (200) of the wind turbine to the pre-laid mooring system (300), the turret element (1) is arranged in a vertical position, such that the turret element (1) extends vertically from the base (2) to the support element (3), wherein preferably:the column body (4) extends at least partially between the base (2) and the support element (3); and / or wherein the slip-ring connector (6) is configured to be arranged in a position being arranged above the turret element (1) in a vertical direction.

6. The connecting system (100) of any of the preceding claims, wherein the turret element (1) further comprises a junction box configured to connect the one or more submarine cables to the switchgear (31); wherein preferably the junction box is arranged at the support element (3).

7. The connecting system (100) of any of the preceding claims, wherein the switchgear (31) is configured to receive at least one submarine cable from each of a plurality of external electrical elements such that the switchgear (31) is configured as a connecting node between the plurality of external electrical elements, wherein the plurality of external electrical elements are external to the connecting system, to the weathervaning floating offshore support structure and to the pre-laid mooring system; wherein preferably the plurality of external electrical elements comprises: one or more external wind turbines (500’, 500”), and / or one or more electrical substations, and / or an electrical connection hub and / or one or more electricity-consuming elements.

8. The connecting system (100) of any of the preceding claims, further comprising a voltage transformer (7) configured to adapt the power generated by the generator of the wind turbine to a higher voltage going through the one or more submarine cables.

9. The connecting system (100) of claim 8, wherein the connecting system (100) further comprises a housing configured to house the voltage transformer (7).

10. The connecting system (100) of claim 8 or 9, wherein the voltage transformer (7) is arranged at the weathervaning floating offshore support structure (200) so that the voltage transformer (7) is configured to be rotatable together with the weathervaning floating offshore support structure (200) relative to the pre-laid mooring system (300), wherein the voltage transformer (7) is configured to be cable-connected to receive the power generated by the generator of the wind turbine, to adapt its voltage, and to provide said power with an adapted voltage to the first connecting part (61) of the slip-ring connector (6).

11. The connecting system (100) of claim 8 or 9, wherein the voltage transformer (7) is arranged at the turret element (1) and is cable-connected between the second connecting part (62) of the slip-ring connector (6) and the switchgear (31), such that the cable connection of the switchgear (41) to the second connecting part (62) of the slip-ring connector (6) goes through the voltage transformer (7); wherein preferably the voltage transformer (7) is arranged at the support element (3) of the turret element (1).

12. The connecting system (100) of claims 9 and 11 , wherein the housing is configured as a fluid-cooled housing comprising a plurality of ducts (71), said plurality of ducts comprising a plurality of fluid ducts configured to allow fluid circulation through the housing for fluid-cooling of the voltage transformer (7) and at least one further duct for voltage transformer cables for cable-connecting the voltage transformer (7); wherein the connecting system (100) further comprises a swivel stack assembly (8) connected as a top element of the turret element (1), wherein the swivel stack assembly (8) comprises a plurality of swivel sections (81) stacked on top of each other, wherein the plurality of swivel sections (81) are configured such that, when the weathervaning floating offshore support structure (200) rotates relative to the pre-laid mooring system (300) to align the wind turbine to an incoming wind, the swivel sections (81) swivel relative to each other to provide a fluid passage for allowing a cooling fluid for cooling the voltage transformer (7) to go through the swivel stack assembly (8); wherein preferably the swivel sections (81) also swivel relative to each other to provide a respective passage for at least a part of the voltage transformer cables configured to receive by cable-connection the power generated by the generator of the wind turbine.

13. The connecting system (100) of claim 12, wherein the swivel stack assembly (8) and / or the slip-ring connector (6) are configured to interact with an auxiliary structural system of the connecting system (100) and / or of the weathervaning floating offshore support structure (200), such that the swivel stack assembly (8) and / or the slip-ring connector (6) are movable aside from a central axis of the columnar body (4).

14. The connecting system (100) of claims 12 or 13, wherein the slip-ring connector (6) is an integral part of the swivel stack assembly.

15. A floating offshore wind turbine FOWT system (500) comprising:a weathervaning floating offshore support structure (200) comprising at least one wind turbine (201); a pre-laid mooring system (300), preferably configured as a tension-leg platform TLP; one or more submarine cables (400) configured to receive a power generated by the at least one wind turbine (201); a connecting system (100) according to any of the preceding claims, and configured to connect the weathervaning floating offshore support structure (200) to the pre-laid mooring system (300), such that the one or more submarine cables are connected to the switchgear (31) of the connecting system (100), and such that the weathervaning floating offshore support structure (200) is rotatable relative to the pre-laid mooring system (300) to align the wind turbine to an incoming wind.

16. An interconnected system comprising: a floating offshore wind turbine FOWT system (500) according to claim 15; and a plurality of external electrical elements configured to be connected by means of respective submarine cables (400) to the switchgear (31) of the connecting system (100) of the floating offshore wind turbine system (500), wherein preferably the plurality of external electrical elements comprises one or more external floating offshore wind turbines FOWT systems (500’, 500”) and / or at least one of: an electrical substation, an electrical connection hub or an electricity-consuming elements.

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