WO2025040223A1

WO2025040223A1 - Control of a renewable energy power plant for safety-related functionality

Info

Publication number: WO2025040223A1
Application number: PCT/DK2024/050131
Authority: WO
Inventors: John Bengtson; David Steele; Jesper Nielsen
Original assignee: Vestas Wind Systems A/S
Priority date: 2023-08-24
Filing date: 2024-05-31
Publication date: 2025-02-27

Abstract

According to an aspect of the present invention, there is provided a switchgear control node for a switchgear device of a connection station The connection station comprises a plurality of switchgear devices connected to a substation of a renewable energy power plant via a distribution line. The power plant comprises a plurality of energy assets and each switchgear device is operable to selectively disconnect a power cable, connected to a respective one of the energy assets, from the distribution line. The switchgear control node is configured for hard real-time communication with a respective energy asset controller, associated with one of the plurality of energy assets, for controlling the switchgear device connecting that energy asset to the distribution line in hard real-time. The switchgear control node is configured to: receive a signal from the respective energy asset controller indicative of a disconnection request; and output a corresponding control signal to the switchgear device connecting the associated energy asset to the distribution line. The control signal is configured to cause said switchgear device to interrupt the connection of the associated energy asset to the distribution line.

Description

CONTROL OF A RENEWABLE ENERGY POWER PLANT FOR SAFETY-RELATED FUNCTIONALITY

TECHNICAL FIELD

The present invention relates to a system for controlling the safety-related functionality of a renewable energy power plant. Aspects of the invention relate to a switchgear control node, to a connection station control unit, to a connection station control system, to an energy asset controller, to a power plant control system and to a method of controlling a renewable energy power plant.

BACKGROUND

Renewable energy power plants with distributed energy assets, such as the wind turbines of an off-shore wind power plant, may typically be connected to each other by a power cable array in a string configuration. The string configuration connects the energy assets together in series leading to a downstream distribution line or grid transmission. Each energy asset typically includes a switchgear device or circuit breaker panel for isolating faults from the remaining energy assets. However, the string configuration leads to overspecification of power cables, duplication of equipment, and increased costs associated with the power plant equipment, its commissioning, and ongoing maintenance.

It is an aim of the present invention to improve upon such conventional solutions.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a switchgear control node for a switchgear device of a connection station. The connection station comprises a plurality of switchgear devices connected to a substation of a renewable energy power plant via a distribution line. The power plant comprises a plurality of energy assets and each switchgear device is operable to selectively disconnect a power cable, connected to a respective one of the energy assets, from the distribution line. The switchgear control node is configured for hard real-time communication with a respective energy asset controller, associated with one of the plurality of energy assets, for controlling the switchgear device connecting that energy asset to the distribution line in hard real-time. The switchgear control node is configured to: receive a signal from the respective energy asset controller indicative of a disconnection request; and output a corresponding control signal to the switchgear device connecting the associated energy asset to the distribution line. The control signal is configured to cause said switchgear device to interrupt the connection of the associated energy asset to the distribution line.

In this manner, the safety-related functionality of a conventional renewable energy power plant configuration can be replicated in a parallel arrangement of power cables, where the hard real-time properties of the switchgear control node, and the connection to the respective energy asset, serve to guarantee timely execution of the safety-related functions. For example, the switchgear device can be operated in response to a fault being detected at the respective energy asset with a maximum latency in the order of milliseconds (e.g. approximately 35 milliseconds or sooner).

In the context of the present invention it shall be appreciated that safety-related information is therefore exchanged and acted upon in hard real-time to operate the switchgear device in a manner that ensures the safety integrity of the power plant. The references to ‘hard real-time’ are therefore intended to refer to the operating system configurations that execute respective operations by a prescribed time limit, which may be in the order of milliseconds or tens of milliseconds. Failure to execute the operation(s) in the prescribed time limit results in failure of the system.

However, it is envisaged that the hard real-time operating systems may include an error recovery mechanism, in some examples. That is, the individual or combined hard realtime domains may implement a form of error tolerance in the real-time aspects, allowing a limited number of failures to deliver information or execute an operation within the required time (using the error recovery mechanism) before finally failing.

In each case, the hard real-time domain is contrasted with a soft real-time domain, in which the operating systems are configured to execute respective operations within a prescribed short time window, rather than a precise moment (as specified in a hard realtime system). In this manner, the soft real-time definition allows for timely execution of operations within a period that ensures the operations retain value. For example, operations may have increasing value up to a start point of the prescribed window and then decrease in value to an end point of the window, where the end point marks the last useful point for completing the operation, before the operation fails. To give an example, set points may be dispatched from a power plant controller in soft real-time to an energy asset controller in order to control a power level of an associated energy asset. Here the information can be communicated in soft real-time as the set points are not safety critical, but the timeliness of their delivery will affect the value associated with the energy asset operation.

Optionally, the switchgear control node may be further configured, during the interruption, to: receive a further signal indicative of a reconnection request; and in dependence on receiving the further signal, output another control signal to the switchgear device connecting the associated energy asset to the distribution line. The control signal is configured to cause that switchgear device to reconnect that energy asset to the distribution line. In this manner, the switchgear control node is configured to selectively disconnect and reconnect the associated energy asset once the fault or cause for interruption has been resolved.

The switchgear control node may be configured to convert signals received from the respective energy asset controller to corresponding control signals output to the switchgear device. For example, the switchgear control node may be configured to convert optical fibre signals, sent by the energy asset controller for high-speed transmission, to electronic control signals for controlling the switchgear device. This facilitates hard real-time capabilities even when the switchgear control node and the energy asset controller are separated by large distances.

In an example, the switchgear control node may be further configured for hard real-time communication with one or more safety modules of a connection station control unit for said switchgear device. The switchgear control node may be further configured to: receive a signal from the one or more safety modules indicative of a disconnection request; and in dependence on receiving the signal from the one or more safety modules: output a corresponding control signal to the switchgear device connecting the associated energy asset to the distribution line, thereby interrupting the connection of that energy asset to the distribution line; and output a corresponding notification signal to the respective energy asset controller to notify that energy asset controller of the disconnection. In this manner, the switchgear control node is advantageously further configured to provide a hard real-time response to disconnection requests originating elsewhere in the power plant, for example due to faults at the connection(s) of the power cable(s) to the substation, isolating the respective energy asset. In addition, the switchgear control node is able to communicate the disconnection, by way of the notification signal, to the energy asset controller, in hard real-time, such that the operation of the associated energy asset can be adapted accordingly. Optionally, the notification signal may further comprise information that is indicative of a reason for the disconnection.

In an example, the control node may be further configured to convert signals received from the one or more safety modules to corresponding notification signals output to the respective energy asset controller. This provides for relatively high speed transmission of the notification signals.

In an example, the one or more safety modules of the connection station control unit may comprise a trip module configured to monitor for safety-critical events at the connection station. The switchgear control node may be configured to receive the signal indicative of the disconnection request from the trip module in response to a safety- critical event being detected at the connection station.

Optionally, the one or more safety modules of the connection station may comprise a power plant operator module configured to receive inputs from a power plant operator and determine disconnection requests based thereon. The switchgear control node may be configured to: receive the signal indicative of the disconnection request from the power plant operating module in response to an input from the power plant operator. In this manner, the power plant operator has the ability to interrupt the connection at their discretion.

Optionally, the switchgear control node is configured to receive the further signal from the respective energy asset controller or the one or more safety modules of the connection station control unit. Optionally, the signals indicative of the disconnection request and the reconnection request may be received from the same source, the source being one of the respective energy asset controller or the one or more safety module of the connection station control unit. In this manner, it may be ensured that connection requests from one system do not override the other. According to another aspect of the invention, there is provided a connection station control unit for a switchgear device of a connection station. The connection station comprises a plurality of switchgear devices connected to a substation of a renewable energy power plant via a distribution line. The connection station control unit comprises the switchgear control node described in a previous aspect of the invention.

In this manner, the connection station control unit may include additional processing functionality for processing the signals received at the switchgear control node and determining corresponding signals to output. Optionally, the connection station control unit further comprises the one or more safety modules connected to the switchgear control node. For example, the connection station control unit may include additional processing functions for determining corresponding actions based on the signals received from the one or more safety modules.

According to another aspect of the invention there is provided a connection station control system for controlling a plurality of switchgear devices of a connection station. The plurality of switchgear devices is connected to a substation of a renewable energy power plant via a distribution line. The control system comprises: one or more switchgear control nodes as described in a previous aspect of the invention; and/or one or more switchgear control units as described in a previous aspect of the invention. Optionally, the one or more switchgear control nodes may comprise a respective switchgear control node for each of the plurality of switchgear devices. Optionally, the one or more switchgear control units may comprise a respective switchgear control unit for each of the plurality of switchgear devices. In this manner, the control system provides independent control of the switchgear devices, for example on a one-to-one basis.

In an example, the connection station may further comprise a primary switchgear device connecting the plurality of switchgear devices to the distribution line. The control system may also comprise a primary switchgear control unit configured for hard real-time communication with each switchgear control node. The primary switchgear control node is further configured to: selectively operate the primary switchgear device to disconnect all of the energy assets from the distribution line, and in dependence on said operation, output a signal to each switchgear control node indicative of the disconnection of the associated energy asset from the distribution line. Each switchgear control node is configured to output a corresponding notification signal to the respective energy asset controller in dependence on receiving the signal form the primary switchgear control unit. In this manner, the control system is operable to isolate all of the energy assets, for example in the event of grid loss.

According to yet another aspect of the invention, there is provided an energy asset controller for an associated energy asset of a renewable energy power plant. The associated energy asset is one of a plurality of energy assets connected to a distribution line by a respective one of a plurality of switchgear devices at a connection station of the power plant. The energy asset controller is configured for hard real-time communication with a switchgear control node connected to the respective switchgear device at the connection station. The energy asset controller is configured to execute machine-readable instructions in hard real-time to: receive a sensor signal from a sensor of the associated energy asset; determine a disconnection request based on the received sensor signal; and output a signal indicative of the disconnection request to the switchgear control node so as to operate the respective switchgear device and thereby interrupt the connection of the associated energy asset to the distribution line. In this manner, the energy asset control is able to sense faults at the energy asset and output a disconnection request to the switchgear control node, which may be arranged distally from the energy asset, to operate the respective switchgear device and thereby isolate the energy asset in hard real-time.

Optionally, the energy asset controller is further configured to: receive a notification signal from the connected switchgear control node notifying the energy asset controller of the interruption of the connection of the associated energy asset to the distribution line; and in dependence on receiving the notification signal, output one or more control signals to the associated energy asset for controlling the associated energy asset in a disconnected mode of operation, such as an idling mode of operation. In this manner, the operation of the energy asset may be adapted in response to notification of the disconnection, ensuring safety integrity.

Optionally, the energy asset controller is configured to execute the machine-readable instructions to: receive a further sensor signal from the sensor of the associated energy asset, while the connection of the associated energy asset to the distribution line is interrupted; determine a connection request based on the further sensor signal; and output a further signal to the switchgear control node indicative of the connection request, so as to operate the respective switchgear device and thereby reconnect the associated energy asset to the distribution line; and wherein the energy asset controller is further configured to output one or more control signals to the associated energy asset prior to outputting the further signal, said one or more control signals being configured to prepare the associated energy asset for connection to the distribution line. In this manner the energy asset controller is configured to selectively request disconnect and request

In an example, the energy asset controller may be further configured to: output signals to the switchgear control node over a first communication channel, optionally being a first fibre optic communication channel; and receive dispatch signals from a power plant controller over a second communication channel, each dispatch signal comprising one or more power setpoints. Here, the first and second communication channels allow for different operating systems and time domains, reflecting the relative safety criticality of the information being communicated. For example, the first communication channel may be configured for the hard real-time domain, while the second communication channel may be configured for the soft real-time domain. The energy asset controller may also be configured to output one or more control signals to control the energy asset according to the received one or more power setpoints.

According to a further aspect of the invention, there is provided a power plant control system for a renewable energy power plant comprising: a plurality of energy assets, and a plurality of switchgear devices at a connection station. The plurality of switchgear devices are connected to a substation of the renewable energy power plant via a distribution line. Each switchgear device is operable to selectively disconnect a power cable, connected to a respective one of the energy assets, from the distribution line. The power plant control system comprises: a connection station control system as described in a previous aspect of the invention; and one or more energy asset controllers as described in another previous aspect of the invention. The connection station control system and the energy asset controller(s) therefore exchange safety-related information in the hard real-time domain to ensure the safety integrity of the energy assets and the power plant. In examples, each energy asset controller may be connected to a respective switchgear control node of the connection station control system. Said energy asset controller may be arranged proximally to the associated energy asset and the respective switchgear control node may be arranged distally from the associated energy asset, for example at the connection station. Optionally, a distance between each energy asset controller and the respective switchgear control node is greater than or equal to 100 metres, optionally greater than or equal to 1 kilometres, optionally greater than or equal to 10 kilometres.

In an example, the power plant control system may further comprise: a power plant controller for determining and dispatching active power set points to the one or more energy asset controllers for controlling the associated energy assets. Each energy asset controller may be connected to a respective switchgear control node of the connection station control system by a first communication channel. Each energy asset controller may be connected to the power plant controller by a second communication channel.

According to yet another aspect of the present invention there is provided a method of controlling a renewable energy power plant comprising a plurality of energy assets and a connection station comprising a plurality of switchgear devices connected to a substation of the power plant via a distribution line. Each switchgear device connects a power cable from a respective one of the energy assets to the distribution line. The method comprises, in hard real-time: receiving, at an energy asset controller associated with one of the plurality of energy assets, a sensor signal from a sensor of the associated energy asset; determining a disconnection request based on the received sensor signal; outputting a signal indicative of the disconnection request from the energy asset controller to a respective switchgear control node for controlling the switchgear device connecting the associated energy asset to the distribution line; receiving the signal output from the energy asset controller at the respective switchgear control node; and outputting a corresponding control signal from the switchgear control node to the switchgear device connecting the associated energy asset to the distribution line. The control signal is output to cause said switchgear device to interrupt the connection of the associated energy asset to the distribution line.

Within the scope of this invention it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a known wind turbine;

Figure 2 is a schematic view of a power generation system for use in the wind turbine of Figure 1;

Figure 3 is a schematic architecture of a power network including a wind power plant and a main grid, in accordance with an embodiment of the invention;

Figure 4 is a schematic view of a switchgear device used in the wind power plant of Figure 3;

Figure 5 is a schematic view of a control system architecture, in accordance with an embodiment of the invention, for controlling the wind power plant of Figure 1 ; and

Figure 6 is a flow chart illustrating a method of operating the wind power plant of Figure 5, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

Embodiments of the present invention relate to methods, nodes, controllers and systems for controlling a renewable energy power plant, such as an off-shore wind power plant, comprising a plurality of energy assets.

The present invention is concerned with power plants that include a parallel arrangement of power cables leading from the energy assets. This contrasts with the conventional arrangement of power cables in a string array. Each power cable in the parallel arrangement connects a single energy asset to a respective switchgear device at a connection station. The connection station further connects to a substation of the power plant via a distribution line. In this manner, the switchgear devices are separated from the energy assets and housed at a common location at the connection station. This arrangement makes the process of constructing the power plant more straightforward. Additionally, the energy assets and/or their support structures can be made comparatively smaller and/or lighter, making their transportation easier. The common location of the switchgear devices also provides for ease of maintenance or repair, amongst other advantages.

Typically though, in a conventional arrangement, a critical event I fault at one of the energy assets is detected by a respective energy asset controller at the energy asset, which is further configured to disconnect the energy asset by controlling a directly connected high-voltage circuit breaker (HVCB). For example, a HVCB may ordinarily be disposed in the transition piece of a wind turbine (WTG) for such purposes. In this context, the direct connection between the energy asset controller and the HVCB allowed for functional intervention in hard real-time, typically in the order of tens of milliseconds. This preserves the safety integrity of the energy assets and the power plant substation.

However, in embodiments of the present invention, the switchgear devices are colocated at the connection station, and may be located several kilometres from the energy assets. A different control architecture is therefore required to control the safety-related functions of the power plant. Accordingly, in embodiments of the present invention, the control system architecture is configured to provide a network for communicating safety-related signals between the individual energy asset controllers, arranged in close proximity to the respective energy assets, and the plurality of switchgear devices at the connection station.

For this purpose, each energy asset controller is connected to a respective switchgear control node for controlling a respective switchgear device at the connection station. The safety-related functions are therefore controlled in hard real-time by communicating safety-related information between the individual energy asset controllers and the switchgear control nodes to selectively connect I disconnect the associated energy assets from the distribution line. The safety- related functions may be specified as safety- related with a defined safety integrity level, for example.

To give an example, each energy asset controller may be configured to monitor the respective energy asset in a conventional manner and, amongst other functions, receives sensor signals from a sensor, such as a trip detector, of the energy asset. Each energy asset controller may be configured to determine connection or disconnection requests based on such sensor signals and to output corresponding signals to the respective switchgear control node in hard real-time. The switchgear control node is configured, in turn, to output a corresponding control signal to the switchgear device connecting the associated energy asset to the distribution line. Accordingly, in response to a disconnection request, that energy asset is disconnected from the distribution line, for example within a matter of milliseconds or a guaranteed maximum latency, to ensure the safety integrity of the power plant. The timely execution of the safety-related function is therefore guaranteed by the hard real-time properties of the control system.

The benefit of this is that the safety-related functionality can be replicated in a parallel arrangement of power cables. It is envisaged that the control system architecture will therefore lead to reduced costs and equipment specifications, as well as improved revenue generation.

In the following, aspects of the invention are described in the context of a wind power plant comprising a plurality of wind turbines. However, it shall be appreciated that these examples are not intended to be limiting on the scope of the invention. In other examples, embodiments of the invention are applicable to a renewable energy power plant having other types of energy assets, from which power can be supplied and/or to which power can be transferred. Such energy assets may include renewable energy generators and/or energy storage systems, for example including a photovoltaic system, a power-to-X system (where X may be Hydrogen for example), a grid battery system, and/or other power producing or consuming systems in a power plant that require high- voltage circuit-breakers for safety integrity.

As will be understood by the skilled reader, a wind power plant (WPP) comprises a plurality of wind turbine generators (WTGs), more typically referred to as a ‘wind turbines’. WPPs are also known as wind parks or wind farms. The examples shown are representative only and the skilled reader will appreciate that other specific architectures are possible, in relation to both wind power plants and power plants for other renewable energy sources. Thus, this disclosure relates to renewable energy power plants having a plurality of energy assets in general, rather than being specific to wind power plants and WTGs as in the Figures. In addition, the skilled reader will appreciate that the methods, systems and techniques described below may be applicable to many different configurations of power network. Moreover, the components of the wind power plant and power network are conventional and as such would be familiar to the skilled reader. It is expected that other known components may be incorporated in addition to or as alternatives to the components shown and described in the Figures. Such changes would be within the capabilities of the skilled person.

Figure 1 shows a wind turbine 10 of a known configuration. In this example, the wind turbine 10 is an off-shore wind turbine, but the skilled reader will understand that the general arrangement of a wind turbine is the same regardless of whether it is an offshore or an on-shore wind turbine. The wind turbine 10 is a three-bladed upwind horizontal-axis wind turbine in this example, which is the most common type of wind turbine in use. The wind turbine 10 comprises a tower 12 supporting a nacelle 14, to which a rotor 16 is mounted. The rotor 16 comprises a plurality of rotor blades 18 extending radially from a central hub 20. In this example, the rotor 16 comprises three rotor blades 18, although only two are visible because of the orientation of the wind turbine 10. However, it will be apparent to the skilled reader that other rotor 16 configurations are possible. The rotor 16 is operatively coupled to a power generation system, represented schematically by box 22, housed inside the nacelle 14. The power generation system 22 comprises a generator, arranged to be driven by the rotor 16 to produce electrical power, and a power converter system, which converts the electrical power outputted from the generator into a form suitable for delivery to an electrical grid (not shown in Figure 1). In addition to the power generation system 22, the nacelle 14 and the tower 12 house miscellaneous components required for converting wind energy into electrical energy, along with various other components needed to operate, control and optimise the performance of the wind turbine 10.

The wind turbine 10 is located on an offshore foundation in the form of a monopile 24 in this example. The monopile 24 includes a platform 26 that is supported on a pillar piled into the seabed. A transition piece 30 is provided on the platform 26, positioned below and arranged to carry the wind turbine 10.

A coupling transformer 32, which acts to suitably couple the power generation system 22 to a grid transmission or distribution line (not shown in Figure 1), is located inside the transition piece 30. The coupling transformer 32 is operatively connected to the power generation system 22 via a set of conductor lines 34 that extend inside the tower 12. In this conventional wind turbine 10, a switchgear device 36 is also located in the transition piece 30 and the switchgear device 36 comprises a circuit breaker panel for isolating the electrical equipment inside the wind turbine 10 in safety-related scenarios, including in the event of a fault condition. The switchgear device 36 is connected to the coupling transformer 32 via a set of power cables or busbar 38.

In addition to the circuit breaker panel, the switchgear device 36 comprises a high- voltage joint associated with an incoming array cable 40 and an outgoing array cable 42. The busbar 38, power generation system 22, set of conductor lines 34, coupling transformer 32 and switchgear device 36 all form part of the power equipment of the wind turbine 10, together with any other miscellaneous components required for converting wind energy into electrical energy.

Figure 2 shows the components of the power generation system 22 of the wind turbine 10 in more detail. The components are conventional and, as such, will be familiar to the skilled reader, and so will only be described in overview. Moreover, it should be noted that the example of the power generation system 22 shown in Figure 2 is representative only, and the skilled reader will appreciate that the invention may be applicable to many different configurations and is not limited to a particular convertor architecture. As already noted, the power generation system 22 comprises the generator 23, driven by the rotor 16 (not shown in Figure 2) to produce electrical power, along with a low voltage link defined by the set of conductor lines 34 terminating at the coupling transformer 32. The power generation system 22 also includes a power converter system 25, together with a filter 27, disposed between the generator 23 and the coupling transformer 32, to process the output of the generator 23 into a waveform having a suitable frequency and an appropriate phase angle. The power converter system 25 provides AC to AC conversion by feeding electrical current through a generator side converter 29 followed by a line side converter 31 in series for converting AC to DC and DC to AC respectively. The generator side converter 29 is connected to the line side converter 31 by a DC link 33, providing smoothing for the DC output of the generator side converter 29. The smoothed DC output of the generator side converter 29 is received as a DC input by the line side converter 31 , which creates a three-phase AC output for delivery to the coupling transformer 32. The filter 27 provides low-pass filtering for removing switching harmonics from the AC waveform.

Although the wind turbine 10 has been described individually up to this point, it would typically form part of an offshore wind power plant comprising a plurality of wind turbines connected to each other by a power cable array in a string configuration.

In such a configuration, an entire serial array of power cables, connecting the turbines, may be sized for the combined power of all turbines. This leads to increased costs associated with designing the wind power plant, as well as the materials and equipment used in the wind power plant. The string array also leads to greater costs associated with commissioning the wind power plant and increases ongoing costs of maintaining the wind power plant.

Figure 3 therefore illustrates an exemplary architecture in accordance with embodiments of the invention for mitigating such overspecification of equipment and reducing costs.

The diagram of Figure 3 should only be taken as a representation of a power network. Alternative configurations of power network and power plants are known and it is expected that other known components may be incorporated in addition to or as alternatives to the components shown and described in Figure 3. Such changes would be within the capabilities of the skilled person. For example, additional substations or extra transformers would be expected to be incorporated into the power plant depending upon the number of energy assets, and the WPP may also be considered to comprise STATCOM equipment and other componentry required to connect the WPP to a main grid.

For reasons of consistency with the preceding figures, Figure 3 illustrates an off-shore wind power plant. However, the skilled reader will understand that the invention, as set out by the appended claims, is not limited only to off-shore wind power plants but could also be used for on-shore wind power plants and other types of renewable energy power plants.

The wind power plant 55 comprises a plurality of wind turbines that are represented, in this embodiment, by four wind turbines 56a-d, along with their respective transition pieces 58a-d and monopiles 60a-d. The skilled reader will appreciate that, in practice, the wind power plant 55 of this embodiment could comprise many more wind turbines, for example ranging from tens to hundreds of wind turbines, though such turbines are not shown here for the sake of simplicity. The wind turbines 56a-d are the same as the known wind turbine 10, shown in Figure 1 , in most aspects. In particular, although not shown here, the wind turbines 56a-d comprise a rotor operatively coupled to a power generation system housed with a nacelle. The power generation system comprises a generator driven by the rotor and a power converter system for converting electrical power outputted from the generator into a form suitable for delivery to an electrical grid. The transition pieces 58a-d may each include a coupling transformer 32a-d, and the various miscellaneous components required for converting wind energy into electrical energy, along with other components required to operate, control and optimise the performances of the wind turbines 56a-d are of course also included. However, the wind turbines 56a-d of this embodiment of the invention differ from the known wind turbine 10, shown in Figure 1 , in that they do not include a switchgear device with a circuit breaker panel.

Instead, the wind power plant 55 comprises a shared connection station, generally designated by reference numeral 64, comprising a plurality of switchgear devices 36a-d connected to a substation 52 by a distribution line 62. In this embodiment, the connection station 64 includes four switchgear devices 36a-d, one for each wind turbine 56a-d, providing one-to-one relationship between the wind turbines 56a-d and switchgear devices 36a-d. Not having switchgear devices in the wind turbines 56a-d is advantageous because it can make the process of constructing the wind power plant 55 more straightforward insofar that, in the absence of any switchgear, the transition pieces 58a-d can be made as single pieces being comparatively smaller and lighter, making their transportation easier. As this embodiment relates to an off-shore wind power plant 55, the connection station 64 may be located on a monopile or a jacket comprising three or four anchoring points which has been vacated by a wind turbine, making use of existing infrastructure, or on a floating platform, providing straightforward transportation of the connection station 64 for reasons of maintenance or repair, or any other reason.

The wind power plant 55 comprises a plurality of power cables arranged in a parallel configuration to electrically connect the switchgear devices 36a-d and coupling transformers 32a-d. In this embodiment of the invention, the plurality of power cables comprises four power cables 68a-d, each one of which connecting one of the switchgear devices 36a-d to one of the coupling transformers 32a-d. The switchgear devices 36a-d each comprises respective outgoing power cables 70a-d that are connected to each other by a busbar 72, which is itself connected to the distribution line 62. In examples, the connection between the busbar 72 and distribution line 62 may be a direct connection or alternatively the connection station 64 may comprise a primary switchgear device 74, as shown in Figure 3. The primary switchgear device 74 provides an indirect connection between the switchgear devices 36a-d and distribution line 62. The primary switchgear device 74 enables all of the wind turbines 56a- 56d that are coupled to the connection station 64 to be simultaneously connected or disconnected from the wind power plant 55.

Figure 4 is a schematic view of one of the switchgear devices 36a-d shown in Figure 3. In this instance, only switchgear device 36a is shown but it should be understood that, in this embodiment of the invention, the remaining switchgear devices 36b-d and the primary switchgear device 74 have the same configuration. The switchgear device 36a includes a high-voltage joint, generally designated by 76, comprising a switch assembly 78 associated with the outgoing power cable 70a, together with a circuit breaker panel 80 for protecting the one or more coupling transformers 32a to which the switchgear device 36a is connected. This arrangement, in addition to facilitating the testing of the outgoing power cables 70a prior to installation of the wind turbine 56a, also enables the wind turbine 56a to be de-energised by disconnecting it from the rest of the wind power plant 55, for example when service operations on the wind turbine 56a are undertaken. In situations in which the wind turbine 56a needs to be altogether removed or electrically disconnected from the wind power plant 55, for example in the event of a fault, the parallel configuration of power cables 68a-d (connecting switchgear devices 36a-d to the wind turbine 56a-d on a one-to-one basis) ensures that the wind turbine 56a can be disconnected from the connection station 64 without shutting down other wind turbines 56b-d. Accordingly, the wind power plant 55 does not bear a disproportionate loss in energy production compared to the number of wind turbines 56a-d being faulty or disconnected therefrom.

Returning to Figure 3, the parallel configuration of the power cables 68a-d, connecting a switchgear device 36a-d and a respective wind turbine 56a-d in a one-to-one relationship, also means that each power cable 68a-d is only required to carry an electric current from a single wind turbine 56a-d. This is opposed to the situation in a conventional string array, where an array cable is required to carry electric current from multiple wind turbines connected serially, and so has to be rated accordingly, typically requiring a cross-sectional area of approximately 630mm². However, because each power cable 68a-d in this and other embodiments of the invention is required to carry an electric current from a single wind turbine 56a-d, their respective cross-sectional areas can be comparatively smaller at around 240mm². Alternatively, each power cable 68a- d comprises three cores having cross-sectional areas of around 95mm² (0.00095m²), 120mm² (0.00012m²) or 115mm² (0.00015m²), any one of which might be used to carry an electric current from a single wind turbine 56a-d. This affords the opportunity not only to reduce the overall cost of the wind power plant 55, through using less material, but also reduces the complexity of the network of power cables 68a-d, making the processes of commissioning and maintaining the wind power plant 55 comparatively more straightforward.

In other embodiments, it shall be appreciated that the wind turbines 56a-d may further comprise a connection box (not shown) housed within their transition pieces 58a-d. The connection boxes may comprise a high-voltage joint between respective coupling transformers 32a-d and power cables 68a-d, and may provide a ground or earthing point for the wind power plant 55 within the wind turbines 56a-d. Moreover, the inclusion of connection boxes is also beneficial as a connection point when commissioning and/or testing the wind power plant 55, during which the wind turbines 56a-d are often not present and are mounted only after the commissioning and/or testing is complete. Additionally, or alternatively, in other examples, the connection station 64 may further comprise a step-up transformer (not shown) connected to the substation 52 via the distribution line 62. In one example, the step-up transformer is rated at 66kV or greater. For example, the step-up transformer may be rated at 132kV or greater, meaning that the power equipment within the wind turbines 56a-d themselves does not need to be equivalently rated, but can instead have a low rating, such as for example 36kV or lower, reducing the cost, size and/or complexity of the power equipment. For example, the power equipment within the wind turbines 56a-d may be rated at 1 kV, 3.3kV, 7.4kV, 10kV, 112a-dkV, 16kV, 24kV or 33kV. Reducing the size of the power equipment is particularly advantageous as it enables the size of the tower door, which provides access to the interior of the tower, to be reduced which, in turn, improves its structural response to loads acting on the tower. Reducing the size of the power equipment also provides the additional advantage of increasing the available space within the tower, meaning that it could be repurposed as, for example, storage space. In particular, lower rated power equipment is far cheaper than higher rated power equipment. Further, centralizing higher rated power equipment means lowering a number of such higher rated power equipment. In a further example, the power cables 68a-d may connect the generators 23a-d of the wind turbines 56a-d to respective switchgear devices 36a-d on the connection station 64 such that an AC output from the generator is transferred untransformed to the step-up transformer. This arrangement removes the need for separate transformations and/or power converters 25 within each wind turbine 56a-d, but replaces them with centralised versions of these functional components. Alternatively, the wind turbines 56a-d each may have respective power converters 25 positioned between the generators 23a-d and respective switchgear devices 36a-d on the connection station 64.

In Figure 3, the WPP 55 is further shown to include a connecting network 100 for connecting the WPP 55, and the substation 52 thereof, to the main grid 102. Connecting networks are known in the art and may comprise a combination of on-shore stations, transmission lines, buses and/or transformers for coupling the WPP 55 to the main grid 102. Other components such as circuit breakers, reclosers, and other systems known in the art may also be incorporated into the connecting network. In this example, the WPP 55 and the main grid 102 are connected at a Point of Interconnection (Pol) 104, which is an interface between the WPP 55 and the main grid 102. The Pol 104 may also be referred to as the Point of Common Coupling, which may be abbreviated to ‘PCC’ or ‘PoCC’.

The WTGs 56a-d generate both active power and reactive power and the main grid 102 often has specific active and reactive power level requirements with which the WPP 55 is required to comply. The output of the WTGs 56a-d can be changed to match the specified active and reactive power requirements in real time, for example being executed in a small window of time for program completion. Other grid requirements may be specified for reactive and active current levels and for voltage levels at specific points within the power network.

For this purpose, the WPP 55 may include a substation or power plant controller (PPC) 110, as shown in this example, and each of the WTGs 56a-d may be associated with a respective WTG controller 112a-d. That is, each energy asset, or WTG 56a-d in this example, is provided with an associated individualised controller, in the form of the WTG controllers 112a-d, and a shared controller is provided for centralised control of the energy assets or WTGs 56a-d, in the form of the PPC 110. In some examples, a set of WTGs may share a single, semi-centralised WTG controller, such that there are fewer WTG controllers than WTGs. As would be understood by the skilled person, WTG controllers 112a-d can be considered to be computer systems capable of operating a WTG 56a-d in the manner prescribed herein, and may comprise multiple modules that control individual components of the WTG or just a single controller. The computer system of the WTG controller 112a-d may operate according to software downloaded via a communications network or programmed onto it from a computer-readable storage medium. The PPC 110 is similarly a suitable computer system for carrying out the controls and commands as described herein.

During normal operation of the WPP 55, the WTG controllers 112a-d operate to implement active and reactive current, and/or power, requests received from the PPC 110 to provide frequency and voltage support to the main grid 102. In particular, the Power Plant Controller (PPC) 110 may be connected to the main grid 102 at a Point of Measurement (PoM) 114, as shown in this example, and the PPC 110 is configured to receive one or more measurement signals from the PoM 114. The measurement signals are indicative of characteristics of the power supply from the WPP 55 to the main grid 102, and the measurement signals are used in order to ensure the power demands are satisfied. Such power characteristics may include a frequency level, a power factor, a voltage level, a reactive current level and/or a reactive power level exchanged between the WPP 55 and the main grid 102. As the PoM 114 is not at the Pol 104 in this example, parameters measured at the PoM 114 are only considered to be representative values of the power supply, since losses in the lines between the PoM 114 and Pol 104, and between the PoM 114 and the PPG 110, may have an effect on the measurements. Accordingly, the measurements may be suitably compensated to account for the losses and ensure that the measurements used by the PPG 110 are accurate.

The role of the PPG 110 is therefore to act as a command and control interface between the WPP 55 and the grid 102, and more specifically, between the WPP 55 and a grid operator 116, such as a transmission system operator (TSO) or a distribution system operator (DSO).

In its role as command and control interface, the PPG 110 interprets the power delivery demands requested of it by the grid operator 116 and monitors the measured power characteristics to manage the WTGs 56a-d in order to satisfy the power demands.

The WTGs 56a-d, in turn, alter their current or power output in reaction to the commands received from the PPG 110. In particular, as part of its operation, the PPG 110 generates and sends dispatch signals to the WTG controllers 112a-d and the main role of the WTG controllers 112a-d is to control the WTGs 56a-d according to set points contained within the dispatch signals. In this manner, the WPP 55 is controlled according to a normal mode of operation.

The dispatch signal communication and the resulting power adjustments are not safety- critical and so the power level control may be operated by a soft real-time system. That is, the program(s) or instruction(s) executed by the PPG 110 and the WTG controllers 112a-d for communicating the power set points and adjusting the power levels of the respective WTGs 56a-d accordingly may be performed within a prescribed short time window, rather than a precise moment (as specified in a hard real-time system). However, the soft real-time operating system is not sufficient for providing safety-critical control of the WPP 55. In a conventional arrangement, each WTG controller 112a-d would therefore typically have been further configured to determine a critical event or fault at the associated WTG 56a-d and to execute an intervention in hard real-time by controlling a respective high- voltage circuit breaker (HVCB) disposed at that WTG 56a-d.

Embodiments of the present invention reduce costs by removing the need for a switchgear device at each WTG 56a-d and, instead, the switchgear devices 36a-d are moved to a common remote location at the connection station 64. The connection station 64 may be located several kilometres from the WTGs 56a-d and a different control architecture is therefore required to control the safety-related functions of the WPP 55.

In embodiments of the invention, the safety-related functions are therefore handled by communicating safety-related signals between the individual WTG controllers 112a-d, arranged in close proximity to the respective WTGs 56a-d, and the plurality of switchgear devices 36a-d at the connection station 64.

For this purpose, each WTG controller 112a-d is communicatively coupled to a respective switchgear control node (not shown in Figure 3) that may collectively form part of a connection station control system 150. The WTG controllers 112a-d are connected to the switchgear control nodes for controlling respective switchgear devices 36a-d at the connection station 64 in hard real-time, as shall be described in more detail with reference to Figure 5.

Figure 5 shows an exemplary control system architecture in accordance with embodiments of the invention.

In this example, the system includes the plurality of WTG controllers 112a-d, the connection station control system 150, and the PPG 110. Each WTG controller 112a-d is connected to the connection station control system 150 and the PPG 110 separately by respective first and second communication channels 114a,b.

The first communication channel 114a serves to communicate safety-related information between the WTG controller 112a-d and the connection station control system 150 in hard real-time. The second communication channel 114b connects the WTG controller 112a-d to the PPC 110 and is used to execute the conventional power-related control of the respective WTG 56a-d. For example, the second communication channel 114b is used to communicate dispatch signals from the PPC 110 to the WTG controller 112a-d for controlling the power levels of the respective WTG 56a-d, substantially as described previously.

The first and second communication channels 114a,b may each be provided by fibre optic cables, for example, to ensure high-speed communication and real-time control. However, the first and second communication channels 114a,b may be separated in order to provide independent communication channels configured for distinct real-time operating systems. For example, the WTG controllers 112a-d and the connection station control system 150 are configured to exchange safety-related information in hard realtime to operate the switchgear devices 36a-d in a manner that ensures the safety integrity of the WPP 55. That is, the connection station control units 152a-d and the WTG controllers 56a-d are configured to execute program(s) or instruction(s) for communicating the safety-related information and controlling the switchgear devices 36a-d by a prescribed time limit, which may be in the order of milliseconds or tens of milliseconds, to ensure the safety integrity of the WPP 55. However, minor delays in the transmission of set points from the PPC 110 to the WTG controllers 112a-d are not critical to the function or safety of the WPP 55 and so the PPC 110 may be configured to communicate the dispatch signals to the WTG controllers 112a-d in soft real-time.

The safety-related functionality of the WPP 55 shall now be described in more detail with reference to the specific features of the connection station control system 150 and the WTG controllers 112a-d.

In this example, the connection station control system 150 is defined by a collection of hardware components and/or software modules at, or in close proximity to, the connection station 64.

The connection station control system 150 is shown to include a plurality of connection station control units 152a-d, providing a respective connection station control unit 152a- d for each of the WTGs 56a-d (on a one-to-one basis). Figure 5 only shows a first one of the connection station control units 152a-d for communication with a first one of the WTG controllers 112a. However, the presence of further connections to the remaining WTG controllers 112b-d is implied, each being connected to a corresponding connection station control unit 152a-d in a one-to-one basis for controlling the respective switchgear devices 36a-d in a substantially identical manner.

Accordingly although the following description relates to the first connection station control unit 152a, it shall be appreciated that the remaining connection station control units 152b-d are substantially identical and communicate with the respective WTG controller 112b-d and switchgear devices 36b-d in a corresponding manner.

Each connection station control unit 152a-d is connected to a respective (off-grid) auxiliary power source, as is the connection station control system 150, which provides an auxiliary power supply in the absence of a grid connection, the first control unit 152a is therefore shown to include a connection to a first auxiliary power source 156a and the connection station control system 150 is shown to include a connection to another auxiliary power source 158. Each control unit 152a-d further includes one of the switchgear control nodes for controlling the connected switchgear device 36a-d and so the first control unit 152a is shown to include a first switchgear control node 120a. in examples, each connection station control unit 152a-d may further include one or more safety module(s) that obtain indications of faults and operations downstream of the WTGs 56a-d, for example at the connection station 64 or the substation 52. The first control unit 152a is therefore shown to include two safety modules 154a-b in this example.

In each connection station control unit 152a-d, the switchgear control node 120a is configured to provide hard real-time conversion of safety-related information received from, and transmitted to, the respective WTG controller 112a-d. For example, the first switchgear control node 120a is configured to receive connection I disconnection requests from the first WTG controller 112a and to output corresponding control signals to operate the respective circuit breaker 36a in hard real-time, connecting I disconnecting the associated WTG 56a from the distribution line 62. It shall be appreciated that this may involve conversion of signals between communication protocols and formats, for example converting an optic signal received via the first communication channel 114a to an electrical control signal for operating the switchgear device 36a. The safety module(s) 154a-b are configured to obtain indications of downstream faults and operations. That is, the safety modules 154a-b are configured to receive or otherwise determine indications of faults at the connection station 64 (e.g. relating to the connection of a respective power cable 68a-d thereto), or other downstream faults (e.g. at the substation 52) and safety-related information of the grid. The safety modules 154a-b may therefore include: (i) a trip module 154a configured to monitor for safety- critical events and faults occurring at or downstream of the connection station 64; and (ii) a power plant operator module 154b configured to receive inputs from a power plant operator or TSO 116, indicating connection and/or disconnection requests. The trip module 154a may be configured to detect faults at the connection station 64, for example by monitoring one or more power characteristics of the power cables 68a-d connected thereto. The power plant operator module 154b may be configured to receive or determine instructions to connect or disconnect one or more of the WTGs 56a-d from the distribution line 62. For example, such instructions may be received based on inputs from the TSO or grid operator 116, as may be provided via a push button located at any station or substation of the WPP 55 for example.

The safety modules 154a-b are connected to the first switchgear control node 120a so as to provide the node 120a with safety-related information in the forms of signal(s) indicative of connection I disconnection requests. The first switchgear control node 120a is configured to receive such signals and to output respective signals to the respective switchgear device 36a in hard real-time. For example, the node 120a may be configured to output corresponding control signal(s) to the respective switchgear device 36a, thereby connecting I disconnecting the associated WTG 56a from the distribution line 62. Additionally, the node 120a may be configured to output corresponding notification signal(s) to the respective WTG controller 112a for notifying that WTG controller 112a of the disconnection and, in some examples, a reason for the disconnection. It shall be appreciated that this may similarly involve the reverse conversion of signals between communication protocols and formats, for example converting an electrical signal received from the safety modules 154a-b to an optical signal for transmission to the WTG controller 112a via the first communication channel 114a.

In this manner, individual switchgear control devices 36a-d are operated in dependence on the detection of downstream faults and the respective WTG controllers 112a-d are notified to adjust the operation of the respective WTGs 56a-d. For example, the WTG controllers 112a may operate the respective WTG 56a to enter an idling mode of operation following notification of the disconnection from the distribution line 62.

In examples, the connection station control system 150 may also be configured to determine that all of the WTGs 56a-d should be connected or disconnected from the distribution line 62. For example, in the event of a substation fault or a grid fault, the connection station control system 150 may be configured to output a control signal, additionally or alternatively, to the primary switchgear device 74 to interrupt or restore the connection of each WTG 56a-d to the distribution line 62. Again, in this scenario, the connection station control system 150 may be further configured to output notification signals to each of the WTG controllers 112a-d, via the respective switchgear control nodes 120a, to update the control of the WTGs 56a-d accordingly. That is, the WTG controllers 112a-d may include power management functions that are utilized in case of high-voltage grid loss with the purpose of significantly reducing the required power backup capacity in off-grid scenarios. The power management functions may enable the control system to automatically resume operation and reconnect the primary switchgear device 74 when the high-voltage grid returns after a grid outage.

Turning to the WTG controllers 112a-d, and considering the first WTG controller 112a as an example.

Each WTG controller 112a-d includes, amongst other features, one or more modules or sub-modules for receiving the set point signals, dispatched from the PPG 110, and controlling the WTG 56a in a conventional manner, as well as various modules or submodules configured for hard real-time communication of safety-related information with the connection station control system 150.

By way of example, the first WTG controller 112a is shown to include a control module 124 configured to receive signals dispatched by the PPG 110 and to control the WTG 56a according to the set points contained therein, for example by adjusting an active and/or reactive power output from the WTG 56. For this purpose, the PPG 110 and the WTG controllers 112a-d may each include respective communication network switches, illustrated by the module 136 at the WTG controller 112a in Figure 5, for transmitting and receiving the dispatch signals over the second communication channel 114b. The modules that form part of the hard real-time operating system of each WTG controller 112a-d may include one or more safety modules and one or more communication modules, each being connected to the WTG control module, or one or more processors thereof, for hard real-time operation. In Figure 5, the first WTG controller 112a is therefore shown to include: (i) two safety modules 126a-b that obtain information indicative of faults and connection I disconnection requests arising at the WTGs 56a-d and provide corresponding signals to the control module 124, and (ii) a communication module 128 for communicating safety-related information to the connection station control unit 152a.

In this example, the safety modules 126a-b include a trip module 126a connected to one or more sensors (not shown) configured to monitor the first WTG 56a and to output corresponding sensor signals to the control module 124. The one or more sensors may, for example, be configured to monitor the WTG 56 for faults, such as an electric arc or a fire. Such sensors are well-known in the art and shall not be described in detail here to avoid obscuring the invention. The safety modules 126a-b are also shown to include an operator input module 126b configured to receive inputs from an operator, for example from a trip pushbutton, indicating connection and/or disconnection requests received from an operator. The control module 124 is therefore configured to receive sensor signals indicative of such faults, their absence, and/or connection or disconnection requests, from the safety modules 126a, b. The control module 124 is further configured to process such signals and to generate corresponding signals for transmission to the connection station control system 150.

The communication module 128 is configured to exchange communication signals in hard real-time with the corresponding switchgear control node 120a of the connection station control system 150. For example, the control module 124 may receive a sensor signal indicative of a fault from the trip module 126a and generate a signal, indicative of a disconnection request, for transmission to the respective switchgear control node 120a via the communication module 128. The switchgear control node 120a then converts the signal to a corresponding control signal for operating the switchgear device 36a connecting that WTG 56a to the distribution line 62. Similarly, once the fault has been resolved, the sensor(s) may subsequently output sensor signals indicative of the fault correction. In response, the control module 124 may generate another signal indicative of a connection request for transmission to the connection station control system 150, causing the WTG 56a to be reconnected to the distribution line 62 for power output. In examples, it shall be appreciated that, prior to outputting a fault-correction signal or a connection request signal, the WTG controllers 112a may be further configured to output one or more control signals to the respective WTG 56a to prepare the WTG 56a for co nnection/reconn ection to the distribution line 62.

In examples, the communication module 128 may comprise a hard real-time communication network switch 130 and a media converter 132 (such as an advanced media converter) for this purpose, as shown in Figure 5. The communication network switch 130 connects to one or more real-time sub-modules or nodes inside the WTG 56a, which form part of the control model 124, and further connects to the switchgear control node 120a via the media converter 132. The media converter 132 is configured to convert signals received from the control module 124 from a multi-mode network for controlling the WTG 112a to a single-mode network for transmission (for example, converting from a multi-mode optical fibre network to a single-mode optical fibre connection). The media converter 132 transmits signals, for example in the form of optical signals, received from the control module 124, via the network switch 130, in hard real-time to the connection station control system 150, and vice versa. In examples, the media converter 132 of the WTG controller 112a may further serve as a switch or a sensor for detecting activation signals received from the connection station control system 150. In this manner, the WTG controller 112a may be configured to enter a low power mode following disconnection of the associated WTG 56a from the distribution line 62. In the low power mode, the WTG controller 112a stops communicating safety- related information to the connection station control system 150. However, the media converter 132 of the WTG controller 112a may be configured to receive an activation signal from the connection station control system 150, for example signaling a connection request for the WTG 56a, and convey the activation signal to the control module 124 to cause the WTG controller 112a to exit the low power mode. Upon exiting the low power mode, the WTG controller 112a may be configured to output one or more control signals to prepare the associated WTG 56a for power generation, prior to reconnecting the WTG 56a to the distribution line 62.

In examples, each connection station control unit 152a-d and/or each of the WTG controllers 112a-d may be further operable to enable or disable operations of the switchgear devices 36a-d based on user inputs. For example, the connection station control units 152a-d may include an operator input module 140 for this purpose, as shown in Figure 5. The operator input module 140 may be connected to an operator input device (not shown) arranged at the substation 52 or at an on-shore station. The operator input device may therefore be operated by an operator to enable or disable operations of the switchgear devices 36a-d to connect or disconnect the WTGs 56a-d from the distribution line 62. In this manner, the inputs from the operator may supersede other signals received or determined at the connection station control unit 152a-d and control the operation of the switchgear devices 36a-d.

The operation of the WPP 55 shall now be described with additional reference to Figure 6. Figure 6 shows an example method 200 of controlling the WPP 55 in accordance with an embodiment of the invention.

It shall be appreciated that, during normal power generating operation of the WPP 55, the PPG 110 monitors the measured power characteristics at the Pol 104 and the PPG 110 determines and dispatches corresponding power set points to control the power output of the WTGs 56a-d in order to satisfy the power demands of the main grid 102.

However, during such operation, a fault may occur at one of the WTGs 56a-d, such as the first WTG 56a, presenting a reason to disconnect that WTG 56a from the distribution line 62 within a matter of milliseconds (in order to ensure the safety integrity of the WPP 55).

Accordingly, the steps 202 to 210 of the method 200, described below, may be executed in hard real-time to control an appropriate response to the fault.

Initially, in step 202, the first WTG controller 112a may therefore receive a sensor signal, indicative of the fault, from the trip module 126a monitoring the first WTG 56a. For example, a fault detector of the first WTG 56a may detect a fault at the WTG 56a, such as an electrical arc, and output a sensor signal, indicative of the fault, to the control module 124 of the first WTG controller 112a.

In step 204, the control module 124 of the first WTG controller 112a may process the sensor signal and determine, for example by comparison to one or more reference conditions, that it is necessary to isolate the first WTG 56a from the rest of the WPP 55. The control module 124 of the first WTG controller 112a may therefore determine a signal indicative of a disconnection request for transmission to the connection station control system 150.

In step 206, the first WTG controller 112a is configured to output the signal over the first communication channel 114a to the connection station control system 150. For example, the control module 124 may provide the signal to the communication network switch 130 and the media converter 132, in turn, which convert the signal for high-speed transmission over the first communication channel 114a. The signal may therefore be output via the media converter 132 as an optical signal and indicate the request to disconnect the first WTG 56a from the distribution line 62.

In step 208, the signal is received at the first connection station control unit 152a of the connection station control system 150. In particular, the signal is received from the WTG controller 112a at the switchgear control node 120a of the first connection station control unit 152a.

In step 210, the switchgear control node 120a is configured to output a corresponding control signal to the switchgear device 36a connecting the associated WTG 56a to the distribution line 62. For example, the signal may be received at the switchgear control node 120a as an optical signal comprising the disconnection request and the switchgear control node 120a is configured to convert the received signal to an electrical control signal for operating the respective switchgear device 36a. The control signal is therefore output from the switchgear control node 120a, in step 210, in order to cause said switchgear device 36a to interrupt the connection between the first WTG 56a and the distribution line 62.

In this manner, the fault is detected and isolated from the rest of the WPP 55 within milliseconds, complying with the hard real-time requirements of the system and ensuring the safety integrity of the WPP 55.

In examples, the method 200 may include further steps of outputting notification signal(s) from the connection station control system 150 to one or more of the WTG controllers 112a-d, using the respective switchgear control nodes 120a-d, to notify those WTG controllers 112a-d of the disconnection and updating their operation accordingly. For example, upon receiving the notification of the disconnection of the first WTG 56a from the distribution line, the first WTG controller 112a may be configured to update the control of the first WTG 56a accordingly, for example to stop generating power and enter an idling mode or otherwise to shut-down, irrespective of any further power set points received from the PPG 110. The remaining WTGs 56a-d may therefore be controlled to increase their power output to compensate for the loss of power from the first WTG 56a. For example, the PPG 110 may be configured to increase the power set points dispatched to the remaining WTG controller 56b-d in order to maintain the necessary power supply to the main grid 102.

As discussed previously, in order to reconnect the WTG 56a to the distribution line, the WTG controller 112a may continue to monitor the WTG 56a and the trip module 126a may subsequently determine that the fault has been resolved. In response to determining that the fault has been resolved, the WTG controller 112a may be configured to control the WTG 56a for reconnection to the distribution line 62, performing one or more preparatory actions to start generating power, before outputting a further signal, this time indicative of a connection request, to the connection station control system, 150. In turn, the connection station control system 150 may receive the further signal and convert the signal into an electrical control signal output to the switchgear device 36a to reconnect the first WTG 56a to the distribution line 62. The control of the remaining WTGs 56b-d may be updated by the PPG 110 accordingly.

It shall also be appreciated that the connection station control system 150 may, at any time, receive system information indicative of a detected fault at the substation 62 and/or instructions to connect or disconnect one or more of the WTGs 56a-d from the distribution line, for example based on inputs to one or more safety modules of individual connection station control units 152a-d. For example, if the first connection station control unit 152a receives such an input at the safety module 154b, a corresponding signal (indicative of a disconnection request) may be provided to the switchgear control node 120a. In turn, the switchgear control node 120a outputs a corresponding control signal to the respective switchgear device 36a, disconnecting the associated WTG 56a from the distribution line 62. The switchgear control node 120a also converts the received signal into a corresponding notification signal, which is output over the first communication channel 114a to the first WTG controller 112a, indicating the disconnection and a reason for such disconnection, such that the control module 124 can update the operation of the WTG 56a accordingly. Similarly, if all of the WTGs 56a- d are to be disconnected, the connection station control system 150 may output a control signal to the primary switchgear device 74 to disconnect all of the WTGs 56a-d from the distribution line 62 and output corresponding notification signals to the WTG controllers 56a-d, via the respective switchgear control nodes, such that the operations of the

WTGs 56a-d can be updated accordingly.

It is expected that embodiments of the invention will therefore provide for performance of the safety-related functions in hard real-time, ensuring the safety integrity of the power plant whilst also providing the benefits of reduced costs and duplication of equipment brought about by the parallel configuration of power cables.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.

Claims

1 . A switchgear control node for a switchgear device of a connection station, the connection station comprising a plurality of switchgear devices connected to a substation of a renewable energy power plant via a distribution line, the power plant comprising a plurality of energy assets and each switchgear device being operable to selectively disconnect a power cable, connected to a respective one of the energy assets, from the distribution line, the switchgear control node being configured for hard real-time communication with a respective energy asset controller, associated with one of the plurality of energy assets, for controlling the switchgear device connecting that energy asset to the distribution line in hard real-time, the switchgear control node being configured to: receive a signal from the respective energy asset controller indicative of a disconnection request; and output a corresponding control signal to the switchgear device connecting the associated energy asset to the distribution line, the control signal being configured to cause said switchgear device to interrupt the connection of the associated energy asset to the distribution line.

2. A switchgear control node according to claim 1 , wherein the switchgear control node is further configured, during the interruption, to: receive a further signal indicative of a reconnection request; and in dependence on receiving the further signal, output another control signal to the switchgear device connecting the associated energy asset to the distribution line, the control signal being configured to cause that switchgear device to reconnect that energy asset to the distribution line.

3. A switchgear control node according to claim 1 or claim 2, wherein the switchgear control node is configured to convert signals received from the respective energy asset controller to corresponding control signals output to the switchgear device.

4. A switchgear control node according to any preceding claim, wherein the switchgear control node is further configured for hard real-time communication with one or more safety modules of a connection station control unit for said switchgear device, and wherein the switchgear control node is further configured to: receive a signal from the one or more safety modules indicative of a disconnection request; and in dependence on receiving the signal from the one or more safety modules: output a corresponding control signal to the switchgear device connecting the associated energy asset to the distribution line, thereby interrupting the connection of that energy asset to the distribution line; and output a corresponding notification signal to the respective energy asset controller to notify that energy asset controller of the disconnection, optionally, wherein the notification signal further comprises information that is indicative of a reason for the disconnection.

5. A switchgear control node according to claim 4, when dependent on claim 3, wherein the control node is further configured to convert signals received from the one or more safety modules to corresponding notification signals output to the respective energy asset controller.

6. A switchgear control node according to claim 4 or claim 5, wherein the one or more safety modules of the connection station control unit comprise a trip module configured to monitor for safety-critical events at the connection station, the switchgear control node being configured to receive the signal indicative of the disconnection request from the trip module in response to a safety-critical event being detected at the connection station.

7. A switchgear control node according to any of claims 4 to 6, wherein the one or more safety modules of the connection station comprise a power plant operator module configured to receive inputs from a power plant operator and determine disconnection requests based thereon, the switchgear control node being configured to: receive the signal indicative of the disconnection request from the power plant operating module in response to an input from the power plant operator.

8. A switchgear control node according to any of claims 4 to 7, when dependant on claim 3, wherein the switchgear control node is configured to receive the further signal from the respective energy asset controller or the one or more safety modules of the connection station control unit, optionally, wherein the signals indicative of the disconnection request and the reconnection request are received from the same source, the source being one of the respective energy asset controller or the one or more safety module of the connection station control unit.

9. A connection station control unit for a switchgear device of a connection station comprising a plurality of switchgear devices connected to a substation of a renewable energy power plant via a distribution line, the connection station control unit comprising the switchgear control node of any preceding claim.

10. A connection station control unit according to claim 9, when dependant on claim 4, wherein the connection station control unit further comprises the one or more safety modules connected to the switchgear control node.

11. A connection station control system for controlling a plurality of switchgear devices of a connection station, the plurality of switchgear devices being connected to a substation of a renewable energy power plant via a distribution line, the control system comprising: one or more switchgear control nodes according to any of claims 1 to 8, optionally, wherein the one or more switchgear control nodes comprise a respective switchgear control node for each of the plurality of switchgear devices; and/or one or more switchgear control units according to claim 9 or claim 10, optionally, wherein the one or more switchgear control units comprise a respective switchgear control unit for each of the plurality of switchgear devices.

12. A connection station control system according to claim 11 , wherein the connection station further comprises a primary switchgear device connecting the plurality of switchgear devices to the distribution line, and the control system further comprises a primary switchgear control unit configured for hard real-time communication with each switchgear control node; and wherein the primary switchgear control node is further configured to: selectively operate the primary switchgear device to disconnect all of the energy assets from the distribution line, and in dependence on said operation, output a signal to each switchgear control node indicative of the disconnection of the associated energy asset from the distribution line; and wherein each switchgear control node is configured to output a corresponding notification signal to the respective energy asset controller in dependence on receiving the signal form the primary switchgear control unit.

13. An energy asset controller for an associated energy asset of a renewable energy power plant, the associated energy asset being one of a plurality of energy assets connected to a distribution line by a respective one of a plurality of switchgear devices at a connection station of the power plant, the energy asset controller being configured for hard real-time communication with a switchgear control node connected to the respective switchgear device at the connection station; the energy asset controller being configured to execute machine-readable instructions in hard real-time to: receive a sensor signal from a sensor of the associated energy asset; determine a disconnection request based on the received sensor signal; and output a signal indicative of the disconnection request to the switchgear control node so as to operate the respective switchgear device and thereby interrupt the connection of the associated energy asset to the distribution line.

14. An energy asset controller according to claim 13, wherein the energy asset controller is further configured to: receive a notification signal from the connected switchgear control node notifying the energy asset controller of the interruption of the connection of the associated energy asset to the distribution line; and in dependence on receiving the notification signal, output one or more control signals to the associated energy asset for controlling the associated energy asset in a disconnected mode of operation, such as an idling mode of operation.

15. An energy asset controller according to claim 13 or claim 14, wherein the energy asset controller is configured to execute the machine-readable instructions to: receive a further sensor signal from the sensor of the associated energy asset, while the connection of the associated energy asset to the distribution line is interrupted; determine a connection request based on the further sensor signal; and output a further signal to the switchgear control node indicative of the connection request, so as to operate the respective switchgear device and thereby reconnect the associated energy asset to the distribution line; and wherein the energy asset controller is further configured to output one or more control signals to the associated energy asset prior to outputting the further signal, said one or more control signals being configured to prepare the associated energy asset for connection to the distribution line.

16. An energy asset controller according to any of claims 13 to 15, wherein the energy asset controller is further configured to: output signals to the switchgear control node over a first communication channel, optionally being a first fibre optic communication channel; receive dispatch signals from a power plant controller over a second communication channel, each dispatch signal comprising one or more power setpoints; and output one or more control signals to control the energy asset according to the received one or more power setpoints.

17. A power plant control system for a renewable energy power plant comprising: a plurality of energy assets, and a plurality of switchgear devices at a connection station, the plurality of switchgear devices being connected to a substation of the renewable energy power plant via a distribution line, each switchgear device being operable to selectively disconnect a power cable, connected to a respective one of the energy assets, from the distribution line, the power plant control system comprising: a connection station control system according to claim 11 or claim 12; and one or more energy asset controllers according to any of claims 9 to 13.

18. A power plant control system according to claim 17, wherein each energy asset controller is connected to a respective switchgear control node of the connection station control system, said energy asset controller being arranged proximally to the associated energy asset and the respective switchgear control node being arranged distally from the associated energy asset, for example at the connection station; optionally, wherein a distance between each energy asset controller and the respective switchgear control node is greater than or equal to 100 metres, optionally greater than or equal to 1 kilometres, optionally great than or equal to 10 kilometres.

19. A power plant control system according to claim 17 or claim 18, further comprising: a power plant controller for determining and dispatching active power set points to the one or more energy asset controllers for controlling the associated energy assets; wherein each energy asset controller is connected to a respective switchgear control node of the connection station control system by a first communication channel; and wherein each energy asset controller is connected to the power plant controller by a second communication channel.

20. A method of controlling a renewable energy power plant comprising a plurality of energy assets and a connection station comprising a plurality of switchgear devices connected to a substation of the power plant via a distribution line, each switchgear device connecting a power cable from a respective one of the energy assets to the distribution line, the method comprising, in hard real-time: receiving, at an energy asset controller associated with one of the plurality of energy assets, a sensor signal from a sensor of the associated energy asset; determining a disconnection request based on the received sensor signal; outputting a signal indicative of the disconnection request from the energy asset controller to a respective switchgear control node for controlling the switchgear device connecting the associated energy asset to the distribution line; receiving the signal output from the energy asset controller at the respective switchgear control node; and outputting a corresponding control signal from the switchgear control node to the switchgear device connecting the associated energy asset to the distribution line, the control signal being output to cause said switchgear device to interrupt the connection of the associated energy asset to the distribution line.