Auxiliary power supply system for a wind turbine

Abstract

The present invention relates to an auxiliary power supply system for a wind turbine, wherein the wind turbine comprises an auxiliary system comprising one or more auxiliary electrical components, the auxiliary power supply system comprising an auxiliary transformer being operatively connected on a primary side to the power grid, and to a primary side of a switchgear The auxiliary transformer is further operatively connected on a secondary side to the auxiliary system, and / or to an energy storage system. The auxiliary transformer being positioned in the vicinity of the switchgear. The present invention further relates to a wind turbine comprising an auxiliary power supply system and an auxiliary system. The present invention further relates to a method for powering at least part of an auxiliary system and / or an energy storage system of a wind turbine during at least part of an abnormal working condition.

Description

[0001] AUXILIARY POWER SUPPLY SYSTEM FOR A WIND TURBINE

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to an auxiliary power supply system for a wind turbine. The present invention relates, in particular, to an auxiliary power supply system comprising an auxiliary transformer being operatively connected on a primary side to a power grid and a primary side of a switchgear. The present invention further relates to wind turbine and an associated method for providing power to the auxiliary system during an abnormal working condition.

[0004] BACKGROUND OF THE INVENTION

[0005] Auxiliary systems of modern wind turbines contribute to controlling and operating the wind turbines. Auxiliary systems are thus responsible for handling one or more auxiliary functions performed by the wind turbines including for example yawing, pitching, heating, control of hydraulic systems, etc.

[0006] Auxiliary systems often receive supply power from a voltage node on a secondary side of a switchgear which is adapted to disconnect the wind turbine from the power grid during abnormal working conditions. Thus, with the switchgear in a disconnecting state, i.e. the wind turbine is disconnected from the power grid, no supply of power is provided to the auxiliary system . To solve this problem large and costly battery banks have been provided. Despite the large capacity of these battery banks they may inevitable run out of power in case of abnormal working conditions with a long duration. As a consequence service personal need to visit the wind turbine which is both costly as well as time consuming.

[0007] It may be seen as an object of embodiments of the present invention to provide a simple and reliable auxiliary power supply system for a wind turbine.

[0008] It may be seen as a further object of embodiments of the present invention to provide a method for providing power to an auxiliary system of a wind turbine during an abnormal working condition. BRIEF DESCRIPTION OF THE INVENTION

[0009] The above-mentioned objects are complied with by providing, in a first aspect, an auxiliary power supply system for a wind turbine adapted to provide power to a power grid, wherein the wind turbine comprises an auxiliary system comprising one or more auxiliary electrical components, the auxiliary power supply system comprising an auxiliary transformer being operatively connected on a primary side

[0010] - to the power grid, and

[0011] - to a primary side of a switchgear of the wind turbine, wherein the switchgear is adapted to disconnect the generator of the wind turbine from the power grid during at least part of an abnormal working condition, the auxiliary transformer further being operatively connected on a secondary side

[0012] - to the auxiliary system, and / or

[0013] - to an energy storage system being operatively connected to the auxiliary system, the auxiliary transformer being positioned in the vicinity of the switchgear.

[0014] Thus, the present invention relates, in a first aspect, to an auxiliary power supply system configured to power the auxiliary system of a wind turbine either directly and / or via an energy storage system. The energy storage system may in principle comprise any suitable energy reservoir or even a combination of identical or different energy reservoirs, including a battery bank comprising for example one or more solid state batteries, and / or a hydrogen -based storage system.

[0015] The generator of the wind turbine may be driven by a set of rotatably mounted rotor blades which may be pitched in and out of the wind depending on the operating conditions, such as the wind speed. A gearbox may be inserted between the rotor blades and the generator which may have a nominal power in the range 5-20 MW. In case of a plurality of generators the total nominal power may be even higher. Moreover, the generator may provide power to the power grid via a power converter, such as a full-scale power converter.

[0016] The generator of the wind turbine provides power to the power grid via a controllable switchgear which is a controllable power switch being capable of connecting and disconnecting the generator (and associated converters) to / from the power grid. The switchgear may be in a connecting state during normal working conditions (generator connected to power grid), and in a disconnecting state (generator disconnected from power grid) during abnormal working conditions. The switchgear may be rated so that it is capable of handling the nominal power of the generator.

[0017] In the present context the auxiliary system of the wind turbine is to be understood as any electrical component that may contribute to operating the wind turbine. Thus, the one or more auxiliary electrical components of the auxiliary system may be responsible for handling one or more auxiliary functions performed by the wind turbine including for example yawing, pitching, heating, control of hydraulic systems, etc. The auxiliary system may comprise one or more controllers adapted to control at least the switchgear of the wind turbine, i.e. bringing the switchgear into a connecting state during normal working conditions and / or bring the switchgear into a disconnecting state during abnormal working conditions.

[0018] In the present context an abnormal working condition may arise if the grid voltage deviates from its nominal value by more than a certain percentage. An abnormal working condition would also arise if the power grid collapses completely. Thus, an abnormal working condition may relate to both an overvoltage event and an undervoltage event although undervoltage events are the most common. An undervoltage event may arise if the grid voltage drops to for example 0.85-0.90 pu for a certain period of time, such as 0.85 for one 1 hour. It should though be noted that the voltage range may be different from 0.85-0.90 pu, and it may be dictated by grid codes at the site of the wind turbine. A power grid voltage of 0.85 pu corresponds to 85% of the nominal grid voltage, i.e. the grid voltage at normal operating conditions. Normal operating conditions may be considered to have been reached when the grid voltage exceeds 0.90 pu.

[0019] As stated above the auxiliary transformer is on its primary side operatively connected to both the power grid and the primary side of a switchgear of the wind turbine. In fact, the auxiliary transformer may on its primary side be connected to the high-voltage terminals of the switchgear to which the power grid may also be connected. The auxiliary transformer may thus on its primary side be permanently connected to the power grid. The auxiliary transformer may be a single-phase or a multi-phase transformer.

[0020] In general, the auxiliary transformer can be positioned in the vicinity of the switchgear. Thus, the auxiliary transformer can physically be located in the same electrical cabinet structure as the switchgear, or in a side cabinet to the switchgear, as the auxiliary transformer is connected to the terminals on the primary side of the switchgear. This implementation is advantageous for safety reasons.

[0021] Connecting the primary side of the auxiliary transformer to the high-voltage terminals of the switchgear is advantageous in that the auxiliary transformer is then permanently connected to the power grid. For example, when the power grid is re-established, or if the switchgear is tripped due to faults, the wind turbine will always have power available (via the auxiliary transformer) for the control system. The control system may wake up, clear faults, communicate to surveillance and provide to control the switchgear. This may also apply in scenarios where the wind turbine backup systems are faulty or depleted. Thus, according to the present invention remote support to the wind turbine is enabled whereby visiting the wind turbine can be avoided.

[0022] Connecting the primary side of the auxiliary transformer to the high-voltage terminals of the switchgear is also advantageous in that the auxiliary system can be powered without having the main transformer of the wind turbine energized. The fact that the main transformer is not energized saves a lot of energy losses while, at the same time, the auxiliary system is fully powered. As a consequence, the wind turbine is able to start up fairly quickly if requested to do so. For example, a wind turbine may not be in an operational mode due to lack of wind. In such a scenario it may be beneficial to open the switchgear, while still having the auxiliary system powered to a level where the wind turbine can be controlled according to its needs. Disconnecting a wind turbine from the power grid may also be performed in order to avoid the influence of inrush currents from other main transformers when being energized.

[0023] As stated above the auxiliary transformer is operatively connected on its secondary side to the auxiliary system, and / or to the energy storage system being operatively connected to the auxiliary system. Thus, the auxiliary system may be powered exclusively by the auxiliary transformer via an optional rectifier. In the event of available excess power from the auxiliary transformer this excess power may be used to charge the energy storage system.

[0024] Alternatively, the auxiliary system may be powered by the auxiliary transformer via an optional rectifier as well as powered by the energy storage system in combination. Finally, the auxiliary system may be powered exclusively by the energy storage system. Suitable rectifies and / or converters (AC / DC) may be arranged between the auxiliary transformer and the auxiliary system, and converters (DC / DC) may be arranged between the energy storage system and the auxiliary system.

[0025] The auxiliary transformer may on its primary side be configured to handle at least 20 kV, such as 33 kV, 66 kV, 132 kV or even higher voltages. On its secondary side the auxiliary transformer may be configured to deliver up to 1 kV, such as deliver a voltage in the range 24 V to IkV. The secondary voltage of the auxiliary transformer may be distributed to the one or more auxiliary electrical components of the auxiliary system via an auxiliary grid and optional rectifies and / or converters.

[0026] As already mentioned, the nominal power of the generator of the wind turbine may be in the range 5-20 MW. In case of a plurality of generators the total nominal power may be even higher. In comparison, the power rating of the auxiliary transformer may be in the range 5-20 kVA. In a second aspect the present invention relates to a wind turbine comprising

[0027] - a generator being operatively connected to a power grid,

[0028] - an auxiliary system comprising one or more auxiliary electrical components, and

[0029] - an auxiliary power supply system comprising an auxiliary transformer being operatively connected on a primary side o to the power grid, and o to a primary side of a switchgear of the wind turbine, wherein the switchgear is adapted to disconnect the generator of the wind turbine from the power grid during at least part of an abnormal working condition

[0030] - the auxiliary transformer further being operatively connected on a secondary side o to the auxiliary system, and / or o to an energy storage system being operatively connected to the auxiliary system.

[0031] Thus, the present invention relates, in a second aspect, to a wind turbine comprising a generator, and auxiliary system and an auxiliary power supply system according to the first aspect. The auxiliary power supply system is thus configured to power the auxiliary system of a wind turbine either directly and / or via an energy storage system. The energy storage system may in principle comprise any suitable energy reservoir or even a combination of identical or different energy reservoirs, including a battery bank comprising for example one or more solid state batteries, and / or a hydrogen-based storage system.

[0032] The auxiliary transformer, the auxiliary system, the energy storage system and the wind turbine may be implemented as disclosure in relation to the first aspect. Similarly, the definition of the abnormal working condition also applies in relation to the second aspect.

[0033] In a third aspect the present invention relates to a wind power plant comprising a plurality of wind turbines according to the second aspect.

[0034] In a fourth aspect the present invention relates to a method for powering at least part of an auxiliary system and / or an energy storage system of a wind turbine during at least part of an abnormal working condition, the method comprising the steps of

[0035] - providing power to at least part of the auxiliary system and / or the energy storage system via an auxiliary transformer being operatively connected on a primary side o to a power grid, and o to a primary side of a switchgear of the wind turbine, wherein the switchgear is adapted to disconnect the generator of the wind turbine from the power grid during at least part of an abnormal working condition

[0036] - the auxiliary transformer further being operatively connected on a secondary side o to the auxiliary system, and / or o to the energy storage system being operatively connected to the auxiliary system.

[0037] Thus, the fourth aspect of the present invention relates to a method for powering at least part of an auxiliary system and / or an energy storage system of a wind turbine during at least part of an abnormal working condition via an auxiliary transformer according to the first aspect.

[0038] The auxiliary transformer, the auxiliary system, the energy storage system and the wind turbine may be implemented as disclosure in relation to the first and second aspects. Similarly, the definition of the abnormal working condition also applies in relation to the fourth aspect.

[0039] During an abnormal working condition, the auxiliary system may be powered at least partly by the secondary side of auxiliary transformer and / or powered at least partly by the energy storage system during at least part of said abnormal working condition. Thus, the auxiliary system may be powered exclusively by the auxiliary transformer via an optional rectifier. In the event of available excess power from the auxiliary transformer this excess power may be used to charge the energy storage system. Alternatively, the auxiliary system may be powered by the auxiliary transformer via an optional rectifier as well as powered by the energy storage system in combination. Finally, the auxiliary system may be powered exclusively by the energy storage system. Suitable rectifies and / or converters (AC / DC) may be arranged between the auxiliary transformer and the auxiliary system, and converters (DC / DC) may be arranged between the energy storage system and the auxiliary system.

[0040] During an abnormal working condition an auxiliary power source of a substation of the power grid may provide auxiliary power to the power grid during at least part of the abnormal working condition. The auxiliary power may power at least part of the auxiliary system via the power grid and the auxiliary transformer. The frequency of the auxiliary power provided by the auxiliary power source may be shifted in frequency compared to the nominal grid frequency. Thus, if the nominal grid frequency is 50 Hz the frequency of the auxiliary power may be for example 55 Hz.

[0041] As already mentioned, the generator of the wind turbine provides power to the power grid via a controllable switchgear which is a controllable power switch being capable of connecting and disconnecting the generator to / from the power grid. The switchgear may be in a connecting state during normal working conditions (generator connected to power grid), and in a disconnecting state (generator disconnected from power grid) during abnormal working conditions. The switchgear may be rated so that it is capable of handling the nominal power of the generator. Thus, an abnormal working condition may at least involve that the switchgear is in a disconnecting state during at least part of said abnormal working condition.

[0042] The method according to the fourth aspect may further comprise the step of ensuring that one or more controllers of the auxiliary system may be powered via the auxiliary transformer and / or via the energy storage system during at least part of the abnormal working condition.

[0043] The method according to the fourth aspect may further comprise the step of ensuring that the one or more controllers may provide that the switchgear reconnects the wind turbine to the power grid when normal working conditions have been established.

[0044] The method according to the fourth aspect may even further comprise the step of ensuring that the one or more controllers further may provide that other auxiliary electrical components of the auxiliary system are powered in a predetermined order prior to reconnecting the wind turbine to the power grid. The predetermined order may depend on the wind turbine site, including whether the wind turbine is an onshore or offshore wind turbine. This approach is advantageous in that the wind turbine control system may be allowed to wake up, clear faults, communicate to surveillance and gain to control over the switchgear prior to reconnecting the wind turbine to the power grid.

[0045] The overall benefit of the above-mentioned aspects is that the auxiliary transformer is permanently connected to the power grid whereby the supply of power to the auxiliary system of the wind turbine becomes independent of the state of switchgear, i.e. independent of whether the switchgear is in a connecting state or disconnecting state. Further immediate benefits may involve reduced power management logic, "infinite" automatic wake up time, increased ride-through capability in case a wind turbine fault trips the switchgear, i.e. in case of grid fault, reduced capacity of energy storage system, and reduced risk for damage to energy storage system.

[0046] In general, the various aspects of the invention may be combined and coupled in any way possible within the scope of the invention. These and other aspects, features and / or advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention will now be described in further details with reference to the accompanying figures where

[0049] Fig. 1 shows an auxiliary power supply system according to the present invention, and

[0050] Fig. 2 shows a flow chart as to how to provide power to an auxiliary system of a wind turbine during an abnormal working condition.

[0051] DETAILED DESCRIPTION OF THE INVENTION

[0052] As already addressed the present invention relates to an auxiliary power supply system for a wind turbine. The auxiliary power supply system is adapted to provide power to an auxiliary system of the wind turbine and comprises an auxiliary transformer being operatively connected on a primary side to a power grid and a primary side of a switchgear. On a secondary side the auxiliary transformer is operatively connected to an auxiliary system and / or an energy storage system of the wind turbine. The energy storage system is adapted to provide power to the auxiliary system of the wind turbine either in combination with the auxiliary transformer or exclusively.

[0053] The present invention further relates to wind turbine, a wind power plant comprising a plurality of wind turbines and an associated method for providing power to the auxiliary system of the wind turbine during an abnormal working condition, such as when the generator of the wind turbine is disconnected from the power grid.

[0054] Fig. 1 depicts a schematic view of a wind turbine 100 comprising a power generator 101 operatively connected to a power converter 102 in a full-scale power configuration. Other configurations, such as DFIG configurations, may also be applicable. The power generator 101 is driven by a set of rotatable rotor blades typically via a gear box (not shown).

[0055] The power converter 102 provides AC power that matches the grid frequency which is typically 50 or 60 Hz. The AC power is provided to the power grid 106 via a main transformer 103 and a controllable switchgear 104 which is adapted to disconnect the wind turbine 100 from the power grid 106 in abnormal working conditions. As already discussed, an abnormal working condition may involve that the grid voltage deviates from its nominal value by more than a certain percentage. An abnormal working condition would also arise if the power grid collapses completely.

[0056] Thus, an abnormal working condition may be an undervoltage event where the grid voltage drops to for example 0.85-0.90 pu for a certain period of time, such as 0.85 for one 1 hour. It should though be noted that the voltage range may be different from 0.85-0.90 pu, and it may be dictated by grid codes at the site of the wind turbine. A power grid voltage of 0.85 pu corresponds to 85% of the nominal grid voltage, i.e. the grid voltage at normal operating conditions.

[0057] Normal operating conditions may be considered to have been reached when the grid voltage exceeds 0.90 pu.

[0058] During abnormal working conditions the switchgear 104 is open (disconnecting state), whereas in normal working conditions the switchgear 104 is closed (conducting state). A substation 105 may form part of or may be connected to the power grid 106.

[0059] As depicted in Fig. 1 an auxiliary transformer 107 is on its primary side operatively connected to both the power grid 106 (via substation 105) and the primary side of a switchgear 104 of the wind turbine. More particularly, the auxiliary transformer 107 may on its primary side be connected to the high- voltage terminals of the switchgear 104 to which the power grid 106 may also be connected, cf. the dotted lines in the switchgear 104. The auxiliary transformer 107 may thus on its primary side be permanently connected to the power grid 106. The fact that the auxiliary transformer 107 is permanently connected to the power grid 106 is advantageous in that the supply of power to the auxiliary system 108 becomes independent of the state of switchgear, i.e. independent of whether the switchgear is in a connecting state or disconnecting state.

[0060] As a consequence, one or more controllers of the auxiliary system 108 may be powered via the auxiliary transformer 107 and / or via the energy storage system 109 during at least part of the abnormal working condition. The one or more controllers of the auxiliary system 108 may facilitate that the switchgear 104 reconnects the wind turbine to the power grid 106 when normal working conditions have been established. The one or more controllers may even further facilitate that other auxiliary electrical components of the auxiliary system 108 are powered in a predetermined order prior to reconnecting the wind turbine to the power grid 106. The predetermined order may depend on the wind turbine site, including whether the wind turbine is an onshore or offshore wind turbine. This approach is advantageous in that the wind turbine control system may be allowed to wake up, clear faults, communicate to surveillance and gain to control over the switchgear prior to reconnecting the wind turbine to the power grid.

[0061] The auxiliary transformer 107 may be a single-phase or a multi-phase transformer having a power rating in the range of 2-20 kVA. For comparison the nominal power of the generator 101 of the wind turbine may be in the range of 5-20 MW. In case of a plurality of generators the total nominal power may be even higher. The auxiliary transformer 107 has, with its small power rating, a low short circuit current level. Safety protection on the auxiliary system 108 is thus straight forward to the skilled person.

[0062] In general, the auxiliary transformer 107 can be positioned in the vicinity of the switchgear 104. Thus, the auxiliary transformer 107 can physically be located in the same electrical cabinet structure as the switchgear 104, or in a side cabinet to the switchgear 104, as the auxiliary transformer 107 is connected to the terminals on the primary side of the switchgear 104. This implementation is advantageous for safety reasons. As already addressed the auxiliary transformer may on its primary side be configured to handle at least 20 kV, such as 33 kV, 66 kV, 132 kV or even higher voltages. On its secondary side the auxiliary transformer 107 may be configured to deliver up to 1 kV, such as deliver a voltage in the range 24 V to lkV. The secondary voltage of the auxiliary transformer 107 may be distributed to the one or more auxiliary electrical components of the auxiliary system 108 via an auxiliary grid and optional rectifies and / or converters. Alternative or in combination therewith, the secondary voltage of the auxiliary transformer 107 may, after being rectified, be provided to an energy storage system 109 which is adapted to provide power to the one or more auxiliary electrical components of the auxiliary system 108.

[0063] The auxiliary system 108 may be responsible for handling one or more auxiliary functions performed by the wind turbine including for example yawing, pitching, heating, control of hydraulic systems, etc.

[0064] The energy storage system may in principle comprise any suitable energy reservoir or even a combination of identical or different energy reservoirs, including a battery bank comprising for example one or more solid state batteries, and / or a hydrogen-based storage system. The use of the energy storage system 109 facilitates that the auxiliary system 108 is allowed to dissipate more power than can be provided by auxiliary transformer 107, as the energy storage system 109 provides the additional power required. In a wind turbine's auxiliary system 108 there are short term loads which require more power than the auxiliary transformer 107 is rated to deliver. Many of these short term loads are only operated in a small fraction of the time, so the energy storage system 109 can be charged most of the time and discharged in only a small fraction of time.

[0065] Fig. 2 depicts a simple and schematic flow chart of the method according to the present invention. Initially an abnormal working condition either in the power grid or in the wind turbine is detected which caused the switchgear to disconnect the power generator of the wind turbine from the power grid, i.e. the switchgear is brought into a disconnecting state. With the switchgear in the disconnecting state the method provides that power is provided to the wind turbine's auxiliary system via an auxiliary transformer being operatively connected on a primary side to the power grid, and a primary side of a switchgear. The auxiliary transformer is moreover operatively connected on a secondary side to the auxiliary system, and / or an energy storage system being operatively connected to the auxiliary system. Thus, although the switchgear is in a disconnecting state power may be provided to the auxiliary system and thus the control system of the wind turbine. As already addressed, this is advantageous in that it allows full control of the wind turbine prior to reconnecting the wind turbine to the power grid. When a normal working condition is detected the wind turbine, including the auxiliary system of the wind turbine, is prepared for reconnection to power grid. Preparation of the auxiliary system of the wind turbine typically involves that the auxiliary electrical components of the auxiliary system are powered in a predetermined order prior. The predetermined order may depend on the wind turbine site, including whether the wind turbine is an onshore or offshore wind turbine. It should be noted that preparation for reconnection to the power grid may also be initiated prior to the detection of a normal working condition.

[0066] Finally, the switchgear is brought into connecting state in order to reconnect the wind turbine to the power grid.

[0067] Although the invention has been discussed in the foregoing with reference to exemplary embodiments of the invention, the invention is not restricted to these particular embodiments which can be varied in many ways without departing from the invention. The discussed exemplary embodiments shall therefore not be used to construe the appended claims strictly in accordance therewith. On the contrary, the embodiments are merely intended to explain the wording of the appended claims, without intent to limit the claims to these exemplary embodiments. The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using these exemplary embodiments.

Claims

CLAIMS1. An auxiliary power supply system for a wind turbine adapted to provide power to a power grid, wherein the wind turbine comprises an auxiliary system comprising one or more auxiliary electrical components, the auxiliary power supply system comprising an auxiliary transformer being operatively connected on a primary side- to the power grid, and- to a primary side of a switchgear of the wind turbine, wherein the switchgear is adapted to disconnect the generator of the wind turbine from the power grid during at least part of an abnormal working condition, the auxiliary transformer further being operatively connected on a secondary side- to the auxiliary system, and / or- to an energy storage system being operatively connected to the auxiliary system, the auxiliary transformer being positioned in the vicinity of the switchgear.

2. An auxiliary power supply system according to claim 1, wherein the energy storage system comprises a battery bank comprising for example one or more solid state batteries, and / or a hydrogen-based storage system.

3. An auxiliary power supply system according to any of claims 1-2, wherein the auxiliary transformer on its primary side is configured to handle at least 20 kV, such as 33 kV, 66 kV, 132 kV or even higher voltages, and wherein the auxiliary transformer on its secondary side is configured to deliver up to 1 kV, such as deliver a voltage in the range 24 V to IkV.

4. An auxiliary power supply system according to any of claims 1-3, wherein the power rating of the auxiliary transformer is in the range 5-20 kVA.

5. An auxiliary power supply system according to any of claims 1-4, wherein the auxiliary transformer being located in the same electrical cabinet structure as the switchgear, or being in a side cabinet to the switchgear, as the auxiliary transformer is connected to the terminals on the primary side of the switchgear.

6. A wind turbine comprising- a generator being operatively connected to a power grid,- an auxiliary system comprising one or more auxiliary electrical components, and- an auxiliary power supply system comprising an auxiliary transformer being operatively connected on a primary side o to the power grid, and o to a primary side of a switchgear of the wind turbine, wherein the switchgear is adapted to disconnect the generator of the wind turbine from the power grid during at least part of an abnormal working condition- the auxiliary transformer further being operatively connected on a secondary side o to the auxiliary system, and / or o to an energy storage system being operatively connected to the auxiliary system, the auxiliary transformer being positioned in the vicinity of the switchgear7. A wind turbine according to claim 6, wherein the energy storage system comprises a battery bank comprising for example one or more solid state batteries, and / or a hydrogen-based storage system.

8. A wind turbine according to claim 6 or 7, wherein the auxiliary system comprises one or more controllers adapted to control at least the switchgear of the wind turbine.

9. A wind turbine according to any of claims 6-8, wherein the auxiliary transformer on its primary side is configured to handle at least 20 kV, such as 33 kV, 66 kV, 132 kV or even higher voltages., and wherein the auxiliary transformer on its secondary side is configured to deliver up to 1 kV, such as deliver a voltage in the range 24 V to IkV.

10. A wind turbine according to any of claims 6-9, wherein the power rating of the auxiliary transformer is in the range 5-20 kVA.

11. A wind turbine according to any of claims 6-10, wherein the auxiliary transformer being located in the same electrical cabinet structure as the switchgear, or being in a side cabinet to the switchgear, as the auxiliary transformer is connected to the terminals on the primary side of the switchgear.

12. A wind power plant comprising a plurality of wind turbines according to any of claims 6-11.

13. A method for powering at least part of an auxiliary system and / or an energy storage system of a wind turbine during at least part of an abnormal working condition, the method comprising the steps of- providing power to at least part of the auxiliary system and / or the energy storage system via an auxiliary transformer being operatively connected on a primary side o to a power grid, and o to a primary side of a switchgear of the wind turbine, wherein the switchgear is adapted to disconnect the generator of the wind turbine from the power grid during at least part of an abnormal working conditionthe auxiliary transformer further being operatively connected on a secondary side o to the auxiliary system, and / or o to the energy storage system being operatively connected to the auxiliary system,- the auxiliary transformer being positioned in the vicinity of the switchgear.

14. A method according to claim 13, wherein the auxiliary system is powered at least partly by the secondary side of auxiliary transformer and / or powered at least partly by the energy storage system during at least part of said abnormal working condition.

15. A method according to any of claims 13-14, wherein an auxiliary power source of a substation of the power grid provides auxiliary power to the power grid during at least part of the abnormal working condition, and wherein said auxiliary power powers at least part of the auxiliary system via the power grid and the auxiliary transformer.

16. A method according to any of claims 13-15, wherein the abnormal working condition at least involves that the switchgear is in a disconnecting state during at least part of said abnormal working condition.

17. A method according to claim 16, wherein one or more controllers of the auxiliary system is / are powered via the auxiliary transformer and / or via the energy storage system during at least part of the abnormal working condition.

18. A method according to claim 17, wherein the one or more controllers provides that the switchgear reconnects the wind turbine to the power grid when normal working conditions have been established.

19. A method according to any of claims 17-18, wherein the one or more controllers further provides that other auxiliary electrical components of theauxiliary system are powered in a predetermined order prior to reconnecting the wind turbine to the power grid.

Images