Method for operating a wind turbine and wind turbine

Abstract

A method (1000, 2000, 3000) for operating a wind turbine (100-100d) is disclosed. The wind turbine comprises a power conversion system (114, 118, 210, 234, 410, 420, 430) configured to provide an electrical output power (P) to an electrical grid (242), and an air cooling system (450) configured to cool ambient air (28a) in a cooling mode and to provide the cooled ambient air as cooled air (28c) to the power conversion system (114, 118, 210, 234, 410, 420, 430). The method (1000, 2000, 3000) comprises operating (1100, 2100, 3100) the air cooling system (450) in the cooling mode if at least one operating parameter (APD, RPD, TGB, TBS) of the power conversion system (114, 118, 210, 234, 410, 420, 430) is equal to or greater than a respective threshold value (Th1_APD, Th1_RPD, Th1_TGB, Th1_TBS).

Description

TECHNICAL FIELD

[0001] The present subject matter relates generally to wind turbines with power conversion systems, and in particular, operating wind turbines under hot climate conditions. BACKGROUND

[0002] Wind power is considered one of the cleanest and most environmentally friendly energy sources currently available, and wind turbines have been receiving increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and a rotor with one or more rotor blades. The rotor blades capture kinetic energy from the wind using known airfoil principles and transfer the kinetic energy through rotational energy to turn a shaft that couples the rotor blades to a gearbox, or if no gearbox is used, directly to the generator. The generator then converts the mechanical energy to electrical energy, which can be deployed to a utility grid.

[0003] As the rated power of wind turbines increases, the heat generated by the power conversion system during operation can also rise. For example, the total heat generated can amount to about 5% or even 7% of the generated electric power. In particular, the generator can generate a relatively large amount of heat during the conversion of mechanical energy to electrical energy. Furthermore, the gearbox of the power conversion system, which is optionally arranged between the rotor and the generator, can require to be lubricated and cooled to operate efficiently. Moreover, the frequency converter that converts the electric power from the variable speed generator to electric power matching the grid frequency and voltage can also generate a large amount of heat during this conversion. Other components that can provide heat used in the electric drive train of a wind turbine are the MV transformer and the power cables.

[0004] To cool one or more components in the nacelle, an external air can be provided to an internal heat exchanger using a fan, and the heated air can be discharged from the nacelle via an exhaust duct. Alternatively, a passive heat exchanger mounted on the outer surface of the nacelle can be used to provide liquid cooling.

[0005] Since wind turbines are typically designed to their limits to reduce costs and environmental footprint during manufacturing of the wind turbine, a wind turbine provided with a cooling system as described above can not be able to deliver its rated output power during high temperature conditions and / or adverse grid conditions. In this case, the turbine controller starts to curtail the active and / or reactive power of the turbine. However, to comply with grid specifications during these normally rare conditions where the ambient temperature is high, expensive VAR (reactive power) compensation devices for providing fast acting reactive power can be added to the wind turbine and wind farm level, respectively.

[0006] In view of the above, the present disclosure provides a method for operating a wind turbine according to claim 1, a wind turbine according to claim 9, and a computer program product or computer readable storage medium according to claim 15. SUMMARY

[0007] Aspects and advantages of the application will be set forth in part in the following description, or can be obvious from the description, or can be learned through practice of the application.

[0008] In one aspect, the present disclosure relates to a method for operating a wind turbine. The wind turbine comprises a power conversion system configured to provide electrical output power to an electrical grid, and an air cooling system configured to cool ambient air in a cooling mode and to provide the cooled ambient air as cooling air to the power conversion system. The method comprises operating the air cooling system in the cooling mode if at least one operating parameter of the power conversion system is equal to or larger than a respective threshold value.

[0009] Thus, the power conversion system can be effectively cooled even if the ambient temperature, and thus the temperature of the ambient air received from outside the wind turbine, in particular from outside the wind turbine nacelle, is relatively high, e.g. above 30°C, above 35°C or even above 40°C.

[0010] The additional cooling of the ambient air allows to avoid power curtailment and thus to provide the required active and / or reactive power according to grid code requirements at higher ambient temperatures without the need for VAR compensation devices, such as STATCOMs (static synchronous compensators) and capacitor banks, respectively. In particular, the grid can be supported under adverse grid conditions, such as a weak grid.

[0011] This applies both for operating the wind turbine under normal operating conditions, i.e. in the rated wind speed range, and for operating the wind turbine at lower wind speeds or even at no wind speed. It is noted that using an air conditioning system will allow the converter of the power conversion system to be operated at higher VAR levels also without wind, compared to using passive coolers, e.g. at the top of the turbine.

[0012] The air cooling system is typically configured to remove heat from the ambient air with a cooling efficiency of at least 2, more typically at least 3.

[0013] The air cooling system can in particular be provided by an air conditioning system.

[0014] For example, the air conditioning system can be configured to generate about 3 kW of cooling power per 1 kW of electrical energy consumed.

[0015] Since the wind turbine generator has a very high efficiency of e.g. about 97% as well, if the temperature of the coolant air is reduced by an air cooling system, e.g. an air conditioning system, there is a great impact on the output power (the generated power of the generator minus the consumed power of the additional air cooling system which is usually received via an internal electrical power distribution system).

[0016] For example, assuming a wind turbine has a 6 MW rated power, using a 20 kW air conditioning system (at 6 kW input power) would allow to reduce the cooling temperature by at least 5 K, e.g. up to 6° K, which would allow for at least about 150 kW of additional active power in case the thermal limit (cooling without air additional regulation system) is reached. Similar numbers apply for reactive power.

[0017] This shows that using a comparably low level of electrical power from the generator to feed an additional air cooling system, which is usually implemented as an air conditioning system, allows the wind turbine generator to provide up to 25 times more active / reactive power once the system reaches the thermal limit, without the additional air cooling system, because the ambient temperature is high.

[0018] Therefore, the need for investment infrastructure as VAR compensation device is no longer expected, because the power conversion system of the wind turbine can still provide the necessary VAR compensation at higher ambient temperatures when provided with the additional air cooling system.

[0019] Furthermore, the annual energy production (AEP) can be increased. This is because at least the curtailment at higher ambient temperatures can be reduced.

[0020] Alternatively or in addition, if desired, the cooling air provided by the additional air cooling system is used to cool other power conversion components of the power conversion system than the generator, in particular a gearbox arranged between the rotor and the generator, such as a power conversion assembly connected to the power converter of the generator, and / or a transformer connected to the generator and / or the power conversion assembly. Furthermore, if desired, the cooling air provided by the additional air cooling system can be used to cool an electrical cabinet connected to one or more power conversion components of the power conversion system.

[0021] However, this usually results in similar advantages, usually a smaller scope, compared to cooling the generator based on the cooling air provided by the additional air cooling system.

[0022] It is noted that the power conversion system usually comprises several power conversion components which are configured to facilitate a conversion of an input power received from a rotor of the wind turbine into an electrical output power to be provided to an electrical grid, in particular a utility grid, if the input power is received from the rotor of the wind turbine.

[0023] The air cooling system can be operated in the cooling mode independently of the actual temperature of the power conversion system and of the power conversion component(s) of the power conversion system, respectively, or depending on the respective temperature(s). The latter allows to operate the air cooling system (and thus to consume electrical power) in the cooling mode only if actually required for thermal reasons.

[0024] However, it is also possible to operate the air cooling system in the cooling mode independently of the temperature(s) of the power conversion system, but for example based on the ambient temperature, more specifically if the temperature of the ambient air is equal to or greater than an ambient temperature threshold. This control scheme can be simpler compared to operating the air cooling system in the cooling mode depending on the temperature(s) of the power conversion system, but can result in a slightly lower AEP (still higher compared to using uncooled ambient air for cooling).

[0025] For efficiency reasons, the air cooling system is operated in the cooling mode only when the reactive power demand of the power conversion system is equal to or greater than a reactive power demand threshold, and / or if the active power demand of the power conversion system is equal to or greater than an active power demand threshold.

[0026] Otherwise, the (uncooled) ambient air can be sufficient to remove heat from the power conversion system and to cool the power conversion system, respectively.

[0027] The air cooling system can specifically (only) be operated in the cooling mode if at least one of the following conditions is met:

[0028] • the temperature of the cooling air is equal to or greater than a cooling air temperature threshold;

[0029] • the temperature of at least one power conversion component of the power conversion system is equal to or greater than a respective first temperature threshold; and

[0030] • the temperature of the at least one of the power conversion components is equal to or greater than a respective second temperature threshold that is smaller than the respective first temperature threshold.

[0031] The cooling mode of the air cooling system can even depend on the respective temperature(s).

[0032] In particular, the cooling power of the air cooling system can depend on at least one of the temperature of the ambient air, the temperature of the cooling air, and the temperature(s) of the power conversion system.

[0033] In one embodiment of the method for operating a wind turbine comprising a power conversion system and an air cooling system, the method comprises controlling the air cooling system to cool ambient air and to provide the cooled ambient air as cooling air to the power conversion system depending on at least one operating parameter of the wind turbine, in particular depending on at least one operating parameter of the power conversion system.

[0034] The term "operating parameter of the power conversion system" as used herein means any parameter which can influence and / or be used for controlling the operation of the power conversion system during the conversion of the input prime mover power into the electrical output power. The term "operating parameter of the power conversion system" typically comprises the reactive power demand, the active power demand, the active power production of the power conversion system, the reactive power production of the power conversion system, the output current of the power conversion system, the output voltage of the power conversion system, the temperature of the power conversion system as well as the coolant temperature of the coolant used in the internal cooling circuit of any component of the power conversion system and / or the respective component(s) of the power conversion system, and the temperature of the ambient air and the temperature of the provided cooling air, and any combination or function thereof, respectively.

[0035] The air cooling system can in particular be operated in the cooling mode depending on at least one of the following: the temperature of the ambient air, the coolant temperature, the temperature of the gearbox, the temperature of the power converter, the temperature of the transformer and the temperature of the generator, in particular the temperature of the bearings of the generator and / or the temperature of the stator of the generator.

[0036] The respective temperature is typically measured.

[0037] In contrast, the reactive power demand and / or the active power demand are typically received, for example, from a wind farm controller of a wind farm to which the wind turbine belongs.

[0038] The cooling mode can be activated based on at least one of the (measured) temperature(s), the received reactive power demand and the received active power demand.

[0039] Furthermore, the cooling mode can be deactivated (later) based on at least one of the (later) (measured) temperature(s), the (later) received reactive power demand and the (later) received active power demand.

[0040] As mentioned above, the cooling air can be used to remove heat from the power conversion system.

[0041] This is typically achieved using a cooling system which receives the cooling air, and / or can comprise operating three or even four cooling circuits in cascade which are thermally coupled to each other.

[0042] The method can further comprise reducing at least one of the reactive output power of the power conversion system and the reactive output power of the power conversion system, if the temperature of the power conversion system and the temperature of the at least one power conversion component of the power conversion system are equal to or greater than a respective third temperature threshold, respectively.

[0043] The third temperature threshold is typically greater than at least one of the respective first temperature threshold and the respective second temperature threshold, more typically greater than both the respective first temperature threshold and the respective second temperature threshold.

[0044] According to embodiments of the method for manufacturing and / or updating (retrofitting) a wind turbine, the method comprises providing a power conversion system of a wind turbine with an air cooling system configured to cool ambient air such that the air cooling system can provide cooled ambient air as cooling air to the power conversion system of the wind turbine, in particular to the cooling system of the power conversion system and its power conversion components, respectively.

[0045] The method can in particular comprise thermally connecting the air cooling system with the power conversion system for removing heat. For example, an outlet for the cooled ambient air of the air cooling system can be connected with a cooling air inlet and / or a fan of the cooling system of the power conversion system, such as a heat exchanger. Further, the method typically comprises electrically connecting the air cooling system with an internal electrical power distribution system of the wind turbine. Further, the method can comprise updating control software of a control system of the wind turbine according to the control method as explained herein, in particular updating software of a wind turbine controller.

[0046] According to embodiments of the method, the method comprises retrofitting an existing cooling system of a power conversion system of a wind turbine with an additional air cooling system, such as an air conditioning system.

[0047] The steps of the method for operating a wind turbine as explained herein are typically performed by a control system for the wind turbine or even the wind turbine. The control system is communicatively coupled with the power conversion system and the air cooling system and is typically implemented as a controller, such as a respective turbine controller.

[0048] Note that the internal electrical power distribution system of the wind turbine can be connected with the power conversion system for receiving electrical power to be distributed to the air cooling system. In this embodiment, the power conversion system can be considered as an electrical power source, respectively, and the air cooling system can be considered as an electrical power consumer and an electrical load, respectively.

[0049] In another aspect, the present disclosure relates to a computer program product or a non-transitory computer-readable storage medium comprising instructions that, when executed by one or more processors of a system, in particular by a wind turbine having a control system providing one or more processors as described herein, cause the system to perform a method as described herein.

[0050] In yet another aspect, the present invention relates to a wind turbine comprising: a rotor comprising rotor blades; an air cooling system configured to receive ambient air, cool the ambient air, and provide the cooled ambient air as cooling air; and a power conversion system in mechanical connection with the rotor, electrically connectable to a utility grid, and configured to convert input power into electrical output power. The cooling system of the wind turbine is configured to receive cooling air and use the cooling air to remove heat from the power conversion system.

[0051] The power conversion system can be implemented as a DFIG system.

[0052] The cooling system can be a cooling system of the power conversion system, in particular a cooling system sufficient to reliably cool the power conversion system (one or more components) (without receiving cooling from the air cooling system as air) at lower ambient air temperatures (below a second temperature threshold of the ambient air temperature).

[0053] The air cooling system and the cooling system can be considered as two thermally coupled cooling systems in cascade.

[0054] As the air cooling system can only operate under specific conditions (high ambient temperature and high power requirement), the cooling system and the air cooling system can also be considered as a primary cooling system of the power conversion system and a supplemental cooling system of the power conversion system, respectively.

[0055] The (cascaded) air cooling system and the cooling system typically implement a cascade of (at least) three cooling circuits thermally coupled to each other, for example a cascade of (at least) four cooling circuits thermally coupled to each other.

[0056] The cooling system can comprise one or more closed internal cooling circuits in thermal connection with the power conversion system for removing heat (from the respective power conversion components), an open cooling circuit thermally coupled with the respective closed internal cooling circuits and configured to receive cooling air from the air cooling system, a heat exchanger arranged between the open cooling circuit and the closed internal cooling circuits, and a main cooler configured to receive cooling air and typically comprising a heat exchanger and / or an implemented air-liquid cooler, in particular an oil-air cooler. However, the latter can depend on the particular components to be cooled. For example, the outlet of the cooling ambient air of the air cooling system can be connected with an oil cooler of a gearbox of the power conversion system, directly or via a liquid / liquid heat exchanger.

[0057] Typically, the air cooling system is provided by an air conditioning system.

[0058] The air cooling system can be configured to remove heat from the ambient air at a rate of at least up to about 15 kW, more typically at least up to about 20 kW, even more typically at least up to about 23 kW.

[0059] Further, the air cooling system can be configured to remove heat from the ambient air at a cooling efficiency of at least 2, more typically at least 2.5 or even at least 3.

[0060] The power conversion system typically comprises one or more power conversion components configured to facilitate conversion of input power received from the rotor into electrical output power.

[0061] More specifically, the power conversion system can comprise a gearbox, a generator, power conversion components typically comprising a power converter (e.g. a rotor-side power converter and a line-side power converter), and a transformer as a respective power conversion component.

[0062] Typically, the cooling system is configured to remove heat from at least one of the power conversion components.

[0063] The power conversion component(s) can be arranged in a nacelle of the wind turbine.

[0064] The air cooling system can be arranged at least partially in or at the nacelle.

[0065] Typically, the power conversion system is connectable with an internal electrical power distribution system (internal electrical grid) for providing electrical power to the air cooling system and the cooling system.

[0066] Hence, electrical power can flow from the power conversion system through the internal electrical power distribution system and to the air cooling system as well as the cooling system.

[0067] Generally, the wind turbine comprises at least one temperature sensor for measuring a respective temperature, in particular a temperature of the surrounding air, a temperature of the cooling air, a temperature of the power conversion system and a temperature of a respective power conversion component of the power conversion system.

[0068] Further, a controller of the wind turbine is generally communicatively coupled with the air cooling system, the power conversion system and the temperature sensor(s) and is configured to control the wind turbine according to the methods explained herein.

[0069] The present invention provides a set of technical solutions, as follows.

[0070] Technical solution 1. A method (1000, 2000, 3000) for operating a wind turbine (100, 400, 400') comprising a power conversion system configured to provide an electrical output power (P) to an electrical grid and an air cooling system (450) configured to cool surrounding air (28a) in a cooling mode and to provide the cooled surrounding air as cooling air (28c) to the power conversion system, the method (1000, 2000, 3000) comprising:

[0071] • operating the air cooling system (450) in the cooling mode if at least one operating parameter (APD, RPD, TBS) of the power conversion system is equal to or greater than a respective threshold value (Th1_APD, Th1_RPD, Th1_TGB, Th1_TBS).

[0072] Technical solution 2. The method (1000, 2000, 3000) according to technical solution 1, wherein the air cooling system (450) is operated in the cooling mode if at least one of the following conditions is fulfilled:

[0073] • a reactive power demand (RPD) of the power conversion system is equal to or greater than a reactive power demand threshold value (Th1_RPD);

[0074] • an active power demand (APD) of the power conversion system is equal to or greater than an active power demand threshold value (Th1_APD);

[0075] • an air temperature (Ta) of the surrounding air (28a) is equal to or greater than a surrounding temperature threshold value (Th_Ta);

[0076] • a temperature (Tc) of the cooling air (28c) is equal to or greater than a cooling air temperature threshold value (Th1_Tc);

[0077] • the temperature (TGS, TGB, Tc) of at least one power conversion component of the power conversion system is equal to or greater than a respective first temperature threshold (Thl_TGS, Thl_TGB, Thl_Tc), the power conversion system generally comprising several power conversion components configured to facilitate conversion of an input power received from a rotor (106) of the wind turbine (100, 400, 400') into the electrical output power (P), the rotor (106) comprising rotor blades (108); and

[0078] • the temperature (TGS, TGB, Tc) of the at least one of the power conversion components is equal to or greater than a respective second temperature threshold (Th2_GS, Th2_TGB, Th2_Tc) that is smaller than the respective first temperature threshold (Thl_TGS, Thl_TGB, Thl_Tc).

[0079] Technical solution 3. The method (1000, 3000) of technical solution 2, wherein the air cooling system (450) is operated in the cooling mode in dependence of the temperature of the at least one power conversion component.

[0080] Technical solution 4. The method (1000, 3000) of technical solution 2 or 3, wherein the air cooling system (450) is operated in the cooling mode in dependence of at least one of a temperature of a gearbox, a temperature of a power converter (220, 222), a temperature of a transformer, and a temperature of a generator, in particular at least one of a temperature (TGB) of a bearing of the generator and a temperature (TGS) of a stator (120) of the generator.

[0081] Technical solution 5. The method (1000, 2000) of technical solution 2, wherein the air cooling system (450) is operated in the cooling mode irrespective of the temperature of the at least one power conversion component of the power conversion system.

[0082] Technical solution 6. The method (1000, 2000, 3000) of any one of technical solutions 2-4, further comprising reducing at least one of a reactive output power of the power conversion system and a reactive output power of the power conversion system if the temperature of the at least one power conversion component of the power conversion system is equal to or greater than a respective third temperature threshold (Th3_GS, Th3_TGB, Th3_Tc), the third temperature threshold (Th3_GS, Th3_TGB, Th3_Tc) being greater than at least one of the respective first temperature threshold (Thl_TGS, Thl_TGB, Thl_Tc) and the respective second temperature threshold (Th2_GS, Th2_TGB, Th2_Tc).

[0083] Technical Solution 7. The method (1000, 2000, 3000) according to any preceding technical solution, comprising at least one of:

[0084] • measuring a respective temperature;

[0085] • receiving the reactive power demand (RPD);

[0086] • receiving the active power demand (APD);

[0087] • activating the cooling mode based on at least one of the measured temperature, the received reactive power demand (RPD), and the received active power demand (APD);

[0088] • deactivating the cooling mode based on at least one of the measured temperature, the received reactive power demand (RPD), and the received active power demand (APD); and

[0089] • removing heat (Q) from the power conversion system using the cooling air, in particular via a cooling system of the power conversion system, the cooling system being configured to receive the cooling air;

[0090] • operating a cascade of three cooling circuits (C1-C3) that are thermally coupled to each other; and

[0091] • operating a cascade of four cooling circuits (C1-C4) that are thermally coupled to each other.

[0092] Technical Solution 8. A wind turbine (100, 400, 400’), comprising:

[0093] • a rotor (106) comprising rotor blades (108);

[0094] • an air cooling system (450) configured to receive ambient air (28a), cool the ambient air (28a), and provide the cooled ambient air as cooling air (28c);

[0095] • a power conversion system mechanically connected to the rotor (106), electrically connectable to a utility grid, configured to convert an input power into an electrical output power (P); and

[0096] • a cooling system configured to receive the cooling air (28) and remove heat (Q) from the power conversion system using the cooling air.

[0097] Technical Solution 9. The wind turbine (100, 400, 400') of Technical Solution 8, wherein the air cooling system (450) and the cooling system implement at least one of: three cooling circuits (C1-C3) in cascade thermally coupled to each other and four cooling circuits (C1-C4) in cascade thermally coupled to each other, wherein the air cooling system (450) is provided by an air conditioning system, wherein the air cooling system (450) is configured to remove heat from the ambient air at a rate of at least up to about 15 kW, more typically at least up to about 20 kW, even more typically at least up to about 23 kW, and / or wherein the air cooling system (450) is configured to remove heat from the ambient air at a cooling efficiency of at least 2, more typically at least 3.

[0098] Technical Solution 10. The wind turbine (100, 400, 400') of Technical Solution 8 or 9, wherein the power conversion system includes at least one power conversion component configured to facilitate conversion of input power received from the rotor (106) into the electrical output power (P), wherein the power conversion system includes at least one of: a gearbox, a generator, a power conversion component, and a transformer as respective power conversion components, wherein the cooling system is configured to remove heat from at least one of the power conversion components, wherein at least one of the power conversion components is arranged in a nacelle (102) of the wind turbine, wherein the air cooling system (450) is at least partially arranged in or at the nacelle, wherein the cooling system (430) includes at least one of: a closed internal cooling circuit (C4) fluidically connected with the power conversion system to remove the heat; an open cooling circuit (C3) thermally coupled with the closed internal cooling circuit (C4) and configured to receive the cooling air (28c); a heat exchanger (H34) arranged between the open cooling circuit (C3) and the closed internal cooling circuit (C4); and a main cooler configured to receive the cooling air (28c), the main cooler typically including the heat exchanger and / or being implemented as a liquid-liquid heat exchanger or an air-liquid cooler, in particular an oil-gas cooler, wherein the power conversion system is configured to convert the input power into active output power and reactive output power, and / or wherein the power conversion system is a DFIG system.

[0099] Technical Solution 11. The wind turbine (100, 400, 400') as described in any one of Technical Solutions 8-10 further includes a controller communicatively coupled to at least one of the air cooling system (450), the power conversion system and at least one temperature sensor, the control system being generally configured to perform the method (1000, 2000, 3000) according to any one of claims 1 to 7.

[0100] Technical Solution 12. The wind turbine (100, 400, 400') as described in Technical Solution 11, wherein the at least one temperature sensor is configured to measure the temperature of at least one of the following: the ambient air, the cooling air, the power conversion system, and at least one power conversion component of the power conversion system.

[0101] Technical Solution 13. A wind turbine (100, 400, 400') as described in any one of Technical Solutions 8-12, wherein the cooling system includes at least one of a fan (F) and a heat exchanger (H34) of the power conversion system that can provide the cooling air (28c), particularly for a corresponding fan and / or heat exchanger for at least one power conversion component of the power conversion system, such as the generator.

[0102] Technical Solution 14. A wind turbine (100, 400, 400') as described in any of Technical Solutions 8-13, wherein the power conversion system and the air cooling system (450) are connectable to an internal electrical power distribution system, and / or wherein the air cooling system (450) can provide electrical power (Pi) from the power conversion system.

[0103] Technical Solution 15. A computer program product or non-transitory computer-readable storage medium comprising instructions that, when executed by one or more processors (204) of a system, particularly by a control system of a wind turbine (100, 400, 400') as claimed in any one of claims 8 to 14, cause the system to perform the method (1000, 2000, 3000) as claimed in any one of claims 1 to 7.

[0104] These and other features, aspects, and advantages of the present invention will be further supported and described with reference to the following description and the appended claims. Embodiments of the invention are illustrated in conjunction with the accompanying drawings, which are incorporated in and form a part of this specification, and together with the specification serve to explain the principles of the invention. Attached Figure Description

[0105] The invention concept (including its best mode) is fully disclosed and can be implemented by one of ordinary skill in the art in the description with reference to the accompanying drawings, in which:

[0106] Figure 1 A perspective view showing one embodiment of a wind turbine according to the present disclosure;

[0107] Figure 2 Showing suitable for supply Figure 1 A schematic diagram of one embodiment of an electric power system and control system used in conjunction with a wind turbine.

[0108] Figure 3 Showing suitable for supply Figure 1 A block diagram of one embodiment of a controller used in conjunction with a wind turbine is shown.

[0109] Figure 4A A block diagram illustrating one embodiment of a wind turbine according to the present disclosure is shown;

[0110] Figure 4B A block diagram illustrating one embodiment of a wind turbine according to the present disclosure is shown;

[0111] Figure 4C A flowchart illustrating a method according to an embodiment of the present disclosure;

[0112] Figure 5A A flowchart illustrating a method according to an embodiment of the present disclosure; and

[0113] Figure 5B A flowchart illustrating a method according to an embodiment of the present disclosure is shown.

[0114] Individual features depicted in the figures are shown relative to each other and therefore do not need to be drawn to scale. Even when shown in different embodiments, similar or identical elements in the figures are indicated by the same reference numerals. Detailed Implementation

[0115] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each embodiment is provided by way of explanation, which does not limit the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made to the invention without departing from the scope or spirit thereof; for example, features shown or described as part of one embodiment may be used with another embodiment to produce yet another embodiment. Therefore, the invention is intended to cover these modifications and variations that fall within the scope of the appended claims and their equivalents.

[0116] Figure 1 This is a perspective view of a portion of an exemplary wind turbine 100. In an exemplary embodiment, the wind turbine 100 is a horizontal-axis wind turbine. Alternatively, the wind turbine 100 may be a vertical-axis wind turbine. The wind turbine 100 includes a generator housing ( Figure 1nacelle 102 (not shown) is mounted on a tower 104 (a portion of which is shown in Figure 1 The tower 104 can have any suitable height to facilitate operation of the wind turbine 100 as described herein. The wind turbine 100 also includes a rotor 106 including three blades 108 attached to a rotating hub. Alternatively, the wind turbine 100 includes any number of blades 108 that facilitate operation of the wind turbine 100 as described herein. In an exemplary embodiment, the wind turbine 100 includes a gearbox (not shown in Figure 1 and a generator (not shown in Figure 1 ).

[0117] The rotor blades 108 are spaced around the hub 110 to facilitate rotating the rotor 106 to enable kinetic energy to be transferred from the wind into usable mechanical energy and subsequently into electrical energy.

[0118] In one embodiment, the rotor blades 108 have a length ranging from about 15 meters (m) to about 91 m. Alternatively, the rotor blades 108 can have any suitable length that enables the wind turbine 100 to function as described herein. For example, other non-limiting examples of blade lengths include a length of 20 m or less, 37 m, 48.7 m, 50.2 m, 52.2 m, or greater than 91 m. As the wind impinges on the rotor blades 100 from the wind direction 28, the rotor 106 rotates about an axis of rotation 30. As the rotor blades 108 rotate and are subjected to centrifugal forces, the rotor blades 108 are also subjected to various forces and moments. As a result, the rotor blades 108 can be deflected and / or rotated from a neutral or non-deflected position to a deflected position.

[0119] Further, the pitch angle of the rotor blades 100, i.e., the angle that determines the rotor blades' 100 view of the wind direction, can be changed by a pitch system 109 to control the load and power generated by the wind turbine 100 by adjusting the angular position of at least one rotor blade 108 relative to the wind vector. During operation of the wind turbine 100, the pitch system 109 can change the pitch angle of the rotor blades 109 such that the rotor blades are moved to a feathered position such that the view of the wind vector by the at least one rotor blade 100 provides a minimum surface area of the rotor blades 100 oriented toward the wind vector, which facilitates reducing the rotational speed and / or facilitating stalling of the rotor 18.

[0120] The blade pitch of each rotor blade 108 can be individually controlled by a wind turbine controller or pitch control system. Alternatively, the blade pitch of all rotor blades 108 can be simultaneously controlled by the control system.

[0121] Furthermore, in an exemplary embodiment, when the wind direction 28 changes, the yaw direction of the nacelle 102 can be rotated about the yaw axis 38 by the yaw system 105 to position the rotor 106 relative to the wind direction 28.

[0122] The yaw system 105 may include a yaw drive mechanism provided by the cabin 102.

[0123] In addition, the yaw system 105 can also be controlled by a wind turbine controller.

[0124] To properly position the cabin 102 relative to wind direction 28, the cabin 102 may also include at least one meteorological mast 107, which may include a wind vane and an anemometer. Figure 2 (Not shown in the image). Mast 107 can provide information about ambient conditions to the wind turbine controller. This may include wind direction and / or wind speed, as well as ambient temperature, ambient humidity, and type and / or amount of precipitation (if any).

[0125] In an exemplary embodiment, the wind turbine controller 102 is shown as being centralized within the nacelle 102; however, the wind turbine controller could also be distributed throughout the wind turbine 100, within the support system ( Figure 1 (Not shown in the image) A distributed system located within a wind farm and / or at a remote control center. The wind turbine controller includes a processor configured to perform the methods and / or steps described herein.

[0126] See now Figure 2 The diagram illustrates one embodiment of an electric (power) and control system 200 that can be used with a wind turbine 100. During operation, wind impacts blades 108, and blades 108 convert wind energy into mechanical rotational torque, which rotatably drives a low-speed shaft 112 via a hub 110.

[0127] In an exemplary embodiment, the low-speed shaft 112 is configured to drive a gearbox 114, which then progressively increases the low rotational speed of the low-speed shaft 112 to drive the high-speed shaft 116 at the increased rotational speed. The high-speed shaft 116 is typically rotatably coupled to a generator 118 to rotatably drive a generator rotor 122 having an excitation winding (not shown).

[0128] More specifically, in one embodiment, the generator 118 can be a wound rotor, three-phase, doubly-fed induction (asynchronous) generator (DFIG) that includes a generator stator 120 magnetically coupled to a generator rotor 122. Thus, a rotating magnetic field can be induced by the generator rotor 122 and a voltage can be induced within the generator stator 120 magnetically coupled to the generator rotor 122. In such an embodiment, the generator 118 is configured to convert rotational mechanical energy into a sinusoidal, three-phase alternating current (AC) electrical energy signal in the generator stator 120. The associated electrical power can be transmitted to the main transformer via the stator bus 208, the stator synchronization switch 206, the system bus 216, the main transformer circuit breaker 214, and the generator side bus 236. The main transformer incrementally increases the voltage magnitude of the electrical power such that the transformed electrical power can be further transmitted to the grid via the grid circuit breaker 238, the breaker side bus 240, and the grid bus.

[0129] Additionally, the electrical power and control system 200 can include a wind turbine controller configured to control any of the components of the wind turbine 100 and / or implement any of the method steps as described herein. For example, as shown particularly in Figure 3 the controller can include one or more processors 204 and associated memory devices configured to perform various computer-implemented functions (e.g., perform methods, steps, calculations, etc. as disclosed herein and store relevant data). Additionally, the controller 202 can also include a communication module to facilitate communication between the controller and various components of the wind turbine 100 (e.g. Figure 2 any of the components thereof).

[0130] Further, as shown in Figure 3 the communication module 209 can include a sensor interface 211 (e.g., one or more analog-to-digital converters) to allow signals transmitted from one or more sensors to be converted into signals that can be understood and processed by the processor 204. It should be appreciated that the sensors (e.g., sensors 252, 254, 256, 257, 258) can be communicatively coupled to the communication module 209 using any suitable means. For example, as shown in Figure 3 the sensors 252, 254, 256, 257, 258 can be coupled to the sensor interface 211 via a wired connection. However, in other embodiments, the sensors 252, 254, 256, 257, 258 can be coupled to the sensor interface 211 via a wireless connection (e.g., by using any suitable wireless communication protocol known in the art). Thus, the processor 204 can be configured to receive one or more signals from the sensors.

[0131] The sensors 252, 254, 256 can be sensors for controlling the current and / or voltage required for the power conversion of the wind turbine 100. This is explained in more detail below.

[0132] Furthermore, at least one sensor 258 can be provided for sensor data of reference weather data, for example provided by the weather mast 107 as shown. In particular, an ambient air temperature sensor 258 can be provided by the weather mast 107. Figure 1

[0133] Furthermore, at least one temperature sensor 257 can be provided for measuring the temperature within the nacelle, in particular for measuring the temperature of the power conversion system as explained above with respect to Figure 2 and components thereof, respectively, and / or for measuring the temperature of the internal air flow and the respective sensors of the cooling circuit as explained in more detail below with respect to Figure 4A

[0134] As used herein, the term "processor" refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic circuit (PLC), an application specific integrated circuit, and other programmable circuits. The processor 204 is further configured to compute advanced control algorithms and communicate with various Ethernet or serial based protocols (Modbus, OPC, CAN, etc.). Additionally, the memory device(s) can generally include memory element(s) including, but not limited to, computer readable medium, for example, random access memory (RAM), such as synchronous dynamic random access memory (SDRAM), computer readable nonvolatile memory (e.g., flash memory), floppy disks, optical disks, (e.g., compact disc read only memory (CD-ROM), digital versatile disks (DVD), and / or other suitable memory elements. Such memory device(s) can generally be configured to store suitable computer-readable instructions that, when implemented by the processor 204, configure the controller to perform various functions described herein.

[0135] Referring again to Figure 2 The generator stator 120 can be electrically coupled to the stator synchronous switch 206 via a stator bus 208. In the exemplary embodiment, to facilitate a DFIG configuration, the generator rotor 122 is electrically coupled to a bi-directional power conversion assembly 210 via a rotor bus 212. Alternatively, the generator rotor 122 is electrically coupled to the rotor bus 212 via any other means that facilitates operation of the electrical and control system 200 as described herein. As a further alternative, the electrical and control system 200 is configured as a full power conversion system (not shown) that includes a full power conversion assembly (not shown) similar in design and operation to the power conversion assembly 210 and electrically coupled to the generator stator 120. Figure 2 ​​The full power conversion assembly facilitates the directing of electrical power between the generator stator 120 and an electrical power transmission and distribution grid (not shown). In an exemplary embodiment, the stator bus 208 carries three-phase power from the generator stator 120 to the stator synchronous switch 206. The rotor bus 212 carries three-phase power from the generator rotor 122 to the power conversion assembly 210. In an exemplary embodiment, the stator synchronous switch 206 is electrically coupled to the main transformer circuit breaker 214 via a system bus 216. In an alternative embodiment, one or more fuses (not shown) are used in place of the main transformer circuit breaker 214. In another embodiment, neither fuses nor the main transformer circuit breaker 214 are used.

[0136] The power conversion assembly 210 includes a rotor filter 218 electrically coupled to the generator rotor 122 via the rotor bus 212. A rotor filter bus 219 electrically couples the rotor filter 218 to a rotor-side power converter 220, and the rotor-side power converter 220 is electrically coupled to a line-side power converter 222. The rotor-side power converter 220 and the line-side power converter 222 are power converter bridges including power semiconductors (not shown). In an exemplary embodiment, the rotor-side power converter 220 and the line-side power converter 222 are configured in a three-phase pulse width modulation (PWM) configuration, including insulated gate bipolar transistor (IGBT) switching devices (not shown) operating as known in the art Figure 2 (not shown). Alternatively, the rotor-side power converter 220 and the line-side power converter 222 have any configuration using any switching devices that facilitate the operation of the electrical and control system 200 as described herein. The power conversion assembly 210 is coupled with an electronic data communication with a turbine controller to control the operation of the rotor-side power converter 220 and the line-side power converter 222.

[0137] In the exemplary embodiment, a line side power converter bus 223 electrically couples the line side power converter 222 to a line filter 224. Also, a line bus 225 electrically couples the line filter 224 to a line contactor 226. Further, the line contactor 226 is electrically coupled to a transfer circuit breaker 228 via a transfer circuit breaker bus 230. Additionally, the transfer circuit breaker 228 is electrically coupled to the main transformer circuit breaker 214 via the system bus 216 and a connection bus 232. Alternatively, the line filter 224 is directly electrically coupled to the system bus 216 via the connection bus 232 and includes any appropriate protection scheme (not shown) configured to account for the removal of the line contactor 226 and the transfer circuit breaker 228 from the electrical and control system 200. The main transformer circuit breaker 214 is electrically coupled to an electrical power main transformer via a generator side bus 236. The main transformer is electrically coupled to a grid circuit breaker 238 via a circuit breaker side bus 240. The grid circuit breaker 238 is connected to an electrical power transmission and distribution grid via a grid bus. In an alternative embodiment, the main transformer is electrically coupled to one or more fuses (not shown) via the circuit breaker side bus 240, rather than to the grid circuit breaker 238. In another embodiment, neither fuses nor the grid circuit breaker 238 are used, and instead the main transformer is coupled to the electrical power transmission and distribution grid via the circuit breaker side bus 240 and the grid bus.

[0138] In the exemplary embodiment, the rotor side power converter 220 is electrically communicatively coupled with the line side power converter 222 via a single direct current (DC) link 244. Alternatively, the rotor side power converter 220 and the line side power converter 222 are electrically coupled via individual and separate DC links (not shown). Figure 2 The DC link 244 includes a positive rail 246, a negative rail 248, and at least one capacitor 250 coupled between the positive rail 246 and the negative rail 248. Alternatively, the capacitor 250 includes one or more capacitors configured in series and / or parallel between the positive rail 246 and the negative rail 248.

[0139] The turbine controller 202 is configured to receive a plurality of voltage and current measurement signals from the first set of voltage and current sensors 252. In addition, the turbine controller 202 is configured to monitor and control at least some of the operating variables (also referred to herein as operating parameters) associated with the wind turbine 100. In the exemplary embodiment, each of the three voltage and current sensors 252 is electrically coupled to each of the three phases of the grid bus. Thus, the current frequency of the grid can be determined by the controller. Alternatively or additionally, the turbine controller can be functionally coupled with a frequency sensor that can be connected with the grid. In addition, it is possible that the controller 202 receives the current frequency of the grid or at least a signal representative of the current frequency of the grid via a master device controller, such as a wind farm controller, that is functionally coupled with the respective sensor.

[0140] As Figure 2 The electrical and control system 200 also includes a converter controller 262 configured to receive a plurality of voltage and current measurement signals, as shown in FIG. 2. For example, in one embodiment, the converter controller 262 receives voltage and current measurement signals from a second set of voltage and current sensors 254 that are coupled in electronic data communication with the stator bus 208. The converter controller 262 receives a third set of voltage and current measurement signals from a third set of voltage and current sensors 256 that are coupled in electronic data communication with the rotor bus 212. The converter controller 262 also receives a fourth set of voltage and current measurement signals from a fourth set of voltage and current sensors 264 that are coupled in electronic data communication with the converter circuit breaker bus 230. The second set of voltage and current sensors 254 are substantially similar to the first set of voltage and current sensors 252, and the fourth set of voltage and current sensors 264 are substantially similar to the third set of voltage and current sensors 256. The converter controller 262 is substantially similar to the turbine controller 202 and is in electronic data communication connection with the turbine controller 202. In addition, in the exemplary embodiment, the converter controller 262 is physically integrated within the power conversion assembly 210. Alternatively, the converter controller 262 has any configuration that facilitates the operation of the electrical and control system 200 as described herein.

[0141] During operation, wind impinges on the blades 108 and the blades 108 convert the wind energy into mechanical rotational torque that rotatably drives the low speed shaft 112 via the hub 110. The low speed shaft 112 drives the gearbox 114, which subsequently steps up the low rotational speed of the low speed shaft 112 to drive the high speed shaft 116 at an increased rotational speed. The high speed shaft 116 rotatably drives the generator rotor 122. A rotating magnetic field is induced by the generator rotor 122 and a voltage is induced within the generator stator 120 that is magnetically coupled to the generator rotor 122. The generator 118 converts the rotational mechanical energy into a sinusoidal, three-phase alternating current (AC) electrical energy signal in the generator stator 120. In the exemplary embodiment, the associated electrical power is transmitted to the main transformer via the stator bus 208, the stator synchronizing switch 206, the system bus 216, the main transformer circuit breaker 214, and the generator side bus 236. The main transformer steps up the voltage magnitude of the electrical power and the transformed electrical power is further transmitted to the grid via the breaker side bus 240, the grid circuit breaker 238, and the grid bus.

[0142] In the exemplary embodiment, a second electrical power transmission path is provided. Electrical, three-phase, sinusoidal AC power is generated within the generator rotor 122 and transmitted to the power conversion assembly 210 via the rotor bus 212. Within the power conversion assembly 210, the electrical power is transmitted to the rotor filter 218 and the electrical power is modified for a rate of change of a PWM signal associated with the rotor side power converter 220. The rotor side power converter 220 functions as a rectifier and rectifies the sinusoidal, three-phase AC power to DC power. The DC power is transmitted to the DC link 244. The capacitor 250 facilitates mitigating DC link 244 voltage magnitude variations by facilitating mitigating DC ripple associated with AC rectification.

[0143] The DC power is then transmitted from the DC link 244 to the line side power converter 222 and the line side power converter 222 functions as an inverter configured to convert the DC power from the DC link 244 to three-phase, sinusoidal AC electrical power having a predetermined voltage, current, and frequency. The conversion is monitored and controlled via the converter controller 262. The converted AC power is transmitted from the line side power converter 222 to the system bus 216 via the line side power converter bus 223 and the line bus 225, the line contactor 226, the conversion circuit breaker bus 230, the conversion circuit breaker 228, and the junction bus 232. The line filter 224 compensates for or adjusts for harmonic currents in the electrical power transmitted from the line side power converter 222. The stator synchronizing switch 206 is configured to close to facilitate connecting the three-phase power from the generator stator 120 with the three-phase power from the power conversion assembly 210.

[0144] The converter circuit breakers 228, the main transformer circuit breakers 214, and the grid circuit breakers 238 are configured to open the respective bus bars, for example, when excessive current flow can damage the electrical and control system 200. Additional protection components including the line contactors 226 are also provided, which can be controlled by opening switches (not shown in FIG. 2) corresponding to each line of the line bus bar 225 to form an open circuit. Figure 2

[0145] The power conversion assembly 210 compensates or regulates the frequency of the three-phase power from the generator rotor 122 to vary, for example, the wind speed at the hub 110 and the blades 108. Thus, in this manner, the mechanical and electrical rotor frequencies are decoupled from the stator frequency.

[0146] Under some conditions, the bi-directional nature of the power conversion assembly 210, and specifically the bi-directional nature of the rotor-side power converter 220 and the line-side power converter 222, facilitates feeding at least some of the generated electrical power back into the generator rotor 122. More specifically, electrical power is transferred from the system bus bar 216 to the connection bus bar 232, and then through the converter circuit breakers 228 and the converter circuit breaker bus bar 230 to the power conversion assembly 210. Within the power conversion assembly 210, the electrical power is transferred through the line contactors 226, the line bus bar 225, and the line-side power converter bus bar 223 to the line-side power converter 222. The line-side power converter 222 functions as a rectifier and rectifies the sinusoidal three-phase AC power to DC power. The DC power is transferred to the DC link 244. The capacitor 250 facilitates mitigating DC link 244 voltage amplitude variations by facilitating mitigating DC ripple sometimes associated with three-phase AC rectification.

[0147] The DC power is then transferred from the DC link 244 to the rotor-side power converter 220, and the rotor-side power converter 220 functions as an inverter configured to convert the DC electrical power transferred from the DC link 244 to three-phase sinusoidal AC electrical power having a predetermined voltage, current, and frequency. This conversion is monitored and controlled via the converter controller 262. The converted AC power is transferred from the rotor-side power converter 220 to the rotor filter 218 via the rotor filter bus bar 219, and then to the generator rotor 122 via the rotor bus bar 212, thereby facilitating subsynchronous operation.

[0148] ​The power conversion assembly 210 is configured to receive control signals from the turbine controller 202. The control signals are based on sensed conditions or operating characteristics of the wind turbine 100 and the electrical and control system 200. The control signals are received by the turbine controller 202 and used to control the operation of the power conversion assembly 210. Feedback from one or more sensors can be used by the electrical and control system 200 to control the power conversion assembly 210 via the converter controller 262, including, for example, the conversion circuit breaker bus 230, stator bus and rotor bus voltages or current feedback via the second, third and fourth sets of voltage and current sensors 254, 256 and 264. Using this feedback information, and for example, switching control signals, stator synchronization switching control signals and system circuit breaker control (tripping) signals can be generated in any known manner. For example, for a grid voltage transient having predetermined characteristics, the converter controller 262 will at least temporarily substantially suspend conduction of the IGBTs within the line side power converter 222. This operational suspension of the line side power converter 222 will substantially reduce the electrical power being directed through the power conversion assembly 210 to approximately zero.

[0149] In an exemplary embodiment, the generator 118, the power conversion assembly 210 electrically coupled to the generator 118 and the step-up transformer form a power conversion system of the wind turbine 100.

[0150] Figure 4A A block diagram of a wind turbine 400 is shown. The wind turbine 400 is generally similar to the wind turbine 100 explained above with respect to Figures 1-3 and further has a nacelle 402, a power conversion system 410 arranged in the nacelle 402, the power conversion system 410 being mechanically connected to the rotor and being electrically connectable to a utility grid for feeding electrical output power P to the utility grid, typically via the grid circuit breaker 238 and optionally via a further transformer (outside the nacelle 402), for example a wind farm transformer.

[0151] In an exemplary embodiment, an air conditioning system 450, typically implemented as and / or provided by an air cooling system of the air conditioning system, is arranged on and / or at the nacelle 402.

[0152] In cooling mode, the air cooling system 450 cools the ambient air 28a received from the outside nacelle 401 from an ambient air temperature Ta to a lower temperature Tc and, in particular, via an air supply duct arranged between the outlet of the air cooling system 450 for the cooled ambient air and the cooling air inlet of the cooling system 430 for removing excess heat Q from the power conversion system 420, supplies or discharges the cooled ambient air as cooling air 28c to the interior of the nacelle 402, more specifically towards or even towards the cooling system 430 of the power conversion system 410. In the process, the cooling air 28c is reheated and discharged as exhaust air 28d of a higher temperature Td from the nacelle 402, typically via an exhaust air duct.

[0153] As Figure 4A Further shown, the air cooling system 450 can be provided with electrical power PI from the power conversion system 420 via an internal power distribution system.

[0154] Generally, at least the generator of the power conversion system 410 can be cooled using the cooling system 430 provided with cooled ambient air by the air cooling system 430, if needed, in particular at higher ambient air temperatures Ta, if high exhaust heat Q is to be removed and / or if the power conversion system 410 is to deliver a significant amount of (active and / or reactive) power P to the electrical grid.

[0155] Alternatively or additionally, the gearboxes, power converters, transformers and / or electrical cabinets of the power conversion system 410 can be cooled in this way to keep the respective components below respective threshold temperatures. For example, the air conditioning system can be connected to the gearbox coolers via liquid-liquid heat exchangers.

[0156] The temperature Tc and / or the temperature difference Ta-Tc of the respectively cooled ambient air and cooling air 28c can even be controllable.

[0157] Generally, the temperature of one or more of the components of the power conversion system 410 is controlled by the turbine controller communicatively coupled with the air cooling system 450, the cooling system 430, the power conversion system 410, the power conversion components of the power conversion system 410 and / or respective temperature sensors via a data bus and / or respective data lines.

[0158] For cooling the power conversion system 410 and its power conversion components, respectively, the cooling system 430 can have one or more closed cooling circuits for removing heat Q, which circulate with a respective coolant that can be cooled by the cooling air 28c, for example one (or even multiple) respective closed cooling circuit for each power conversion component.

[0159] In Figure 4Bsuch a closed cooling circuit is shown in Fig. 6, Figure 4B a block diagram of a wind turbine 400 is shown, which is generally similar to and can even correspond to the above explained wind turbine 400. Figure 4A

[0160] In the exemplary embodiment, the air cooling system 450 comprises a first open cooling circuit Cl for receiving ambient air 28' at a first inlet and a second open cooling circuit C2 for receiving ambient air 28 at a second inlet. The open cooling circuits Cl, C2 are thermally coupled to each other via a heat exchanger H12 of the air cooling system 450, such that in the cooling mode heat is transferred from the ambient air 28a received at the second inlet to the ambient air 28a' received at the first inlet. In the cooling mode, when the heated air of the first open cooling circuit Cl is discharged at a first outlet as first discharge air 28d' of a higher temperature Te > Ta, the cooled ambient air of the second open cooling circuit C2 is discharged at a second outlet as cooled air 28c of a lower temperature Tc < Ta and is conveyed to an exemplary fan F of the cooling system 430 for pumping the cooled air 28c through an open cooling circuit C3 of the cooling system 430. The open cooling circuit C3 is thermally coupled via a heat exchanger H34 of the cooling system 430 with one exemplary closed cooling circuit C4 for removing heat Q from the power conversion system 410.

[0161] Thus, the four cooling circuits Cl - C4 in cascade, which are thermally coupled to each other, can be used for cooling the power conversion system 410.

[0162] However, it is also possible to cool the power conversion system 410 using only three cooling circuits thermally coupled to each other.

[0163] For example, the first open cooling circuit Cl can be omitted, e.g. in embodiments in which the heat exchanger H12 is implemented as a thermoelectric cooler, i.e. based on thermoelectric cooling of the ambient air 28 in the open cooling circuit C2 and transferred heat discharged via cooling fins or the like.

[0164] However, due to higher efficiency, the heat exchanger H12 is typically implemented as a vapor compression system (even with an additional internal closed cooling circuit).

[0165] This can also apply to the heat exchanger H34.

[0166] Figure 4C a flow chart of a method 1000 of operating a wind turbine is shown, in particular as explained above with respect to Figures 1-4B ​The wind turbine 100, 400, 400' is explained above. Thus, the wind turbine has a power conversion system for providing electrical output power to an electrical grid, in particular a utility grid, and an air cooling system for providing (in cooling mode) cooled ambient air as cooling air to the power conversion system.

[0167] Generally, during operation of the wind turbine in normal operation mode, in which the power conversion system converts input power received from the rotor into electrical output power and provides at least a major part of the electrical output power to the utility grid, the method 1000 comprises a block (step) 1100 of operating the air cooling system in cooling mode and providing cooled ambient air as cooling air to the power conversion system, respectively.

[0168] According to embodiments, the block 1100 is performed depending on at least one operating parameter of the power conversion system and / or when said at least one operating parameter is equal to or greater than a respective threshold value.

[0169] Thus, the block 1100 is generally performed depending on determining the at least one operating parameter, e.g. comprising measuring one or more respective temperatures, or receiving the at least one operating parameter in the previous block 1050.

[0170] As indicated by the dashed arrow in Figure 4C , the method 1000 can return from the block 1100 to the block 1050 at a later time to start a new control cycle.

[0171] Further, only in case the temperature of the power conversion system, e.g. of at least one power component thereof, is equal to or greater than a respective upper temperature threshold (third temperature threshold) although the power conversion system is cooled using cooled ambient air as cooling air, the reactive output power of the power conversion system and / or the reactive output power of the power conversion system can be reduced in the subsequent block 1200.

[0172] Figure 5A A flow chart illustrating a method 2000 of operating a wind turbine, in particular a wind turbine 100, 400, 400' as explained above with respect to Figures 1-4B .

[0173] The method 2000 is generally similar to the method 1000 explained above with respect to Figure 4C . However, the method 2000 is more specific.

[0174] In an exemplary embodiment, the air cooling system is operated in the cooling mode only if the temperature Ta of the surrounding air is equal to or greater than a surrounding temperature threshold value Th Ta, for example 30°C or 35°C, and at least one of the following conditions is fulfilled: (a) the reactive power demand RPD of the power conversion system is equal to or greater than a reactive power demand threshold value Thl RPD, and (b) the active power demand APD of the power conversion system is equal to or greater than an active power demand threshold value Thl APD.

[0175] Otherwise, in block 2300 the active power production and usually also the reactive power production of the power conversion system is controlled without using the cooling mode of the air cooling system to increase the heat removal from the power conversion system, which is not desirable under such conditions.

[0176] The method 2000 can be considered to actively increase the heat removal from the power conversion system at high power demands and high surrounding temperatures, which otherwise can lead to high thermal loads of components of the power conversion system.

[0177] To reduce control-induced fluctuations and / or to save energy, the air cooling system can also be operated only in the cooling mode if the above conditions (Ta≥Th Ta and (RPD>Thl RPD or APD≥Thl APD) are fulfilled, for example for a respective predetermined time period of one or a few seconds.

[0178] Figure 5B A flow chart of a method 3000 of operating a wind turbine is shown, in particular a wind turbine 100, 400, 400’ as explained above with respect to Figures 1-4B the method 1000 explained above with respect to the method 1000 explained above with respect to

[0179] the method 1000 explained above with respect to Figure 4C the method 1000 explained above with respect to

[0180] In an exemplary embodiment, the cooling mode is activated in block 3100 if the temperature Tc of the cooling air is equal to or greater than a first cooling air temperature threshold value Thl Tc, if the temperature TGS of the generator stator is equal to or greater than a first generator stator temperature threshold value Thl TGS, or if the temperature TGB of the generator bearing is equal to or greater than a first generator bearing temperature threshold value Thl TGB.

[0181] The temperatures Tc, TGS and TGB are usually monitored in block 3050.

[0182] After the cooling mode is activated, it can be checked whether the temperature Tc still exceeds or at least reaches a respective higher third temperature threshold value Th3 Tc.

[0183] If yes, then in block 3050, power reduction can be activated for the power conversion system to avoid overheating.

[0184] Otherwise, it can be checked whether all temperatures Tc, TGS and TGB are below the respective second temperature threshold Th2_Tc.

[0185] If yes, then the cooling mode can be deactivated and the method 3000 can return to block 3050. Otherwise, the cooling mode is maintained.

[0186] In contrast to the method 2000 described above with reference to Figure 5A The air cooling system is operated in the cooling mode depending on the monitored generator temperature. Thus, the cooling mode is only used when actually needed.

[0187] Alternatively or additionally, the temperature of other power conversion components can be considered for controlling (activating / deactivating) the cooling mode.

[0188] Further, for controlling the cooling mode (operating the air cooling system), one or more thermal properties of the wind turbine and its components, in particular the power conversion components, such as the respective thermal time constant, can be considered, respectively.

[0189] Although specific features of various embodiments of the present application can be shown in some of the drawings and not in others, this is for convenience only. In accordance with the principles of the present application, any of the features of a drawing can be incorporated into any other of the drawings and / or claimed with respect to any other of the drawings.

[0190] Embodiments of the present application have been described above with reference to block and flow diagrams of methods, apparatuses (i.e. systems) and computer program products. It will be understood that each block of the block diagrams and flow diagrams, and combinations of blocks in the block diagrams and flow diagrams, can be implemented by various means, including computer program instructions. These computer program instructions can be loaded into a general purpose computer, special purpose computer, or other programmable data processing apparatus (such as the processor 204 discussed above with reference to Figure 3 to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functions specified in the flow diagram block or blocks.

[0191] These computer program instructions can also be stored in a non-transitory computer-readable memory that can direct a computer or other programmable data processing apparatus (e.g., the processor 204 discussed above with reference to Figure 3The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks.

[0192] Accordingly, blocks of the block diagrams and flowchart illustrations support combinations of means for performing the specified functions, combinations of steps for performing the specified functions, and program instruction means for performing the specified functions. It will also be understood that each block of the block diagrams and flowchart illustrations, and combinations thereof, can be implemented by special purpose hardware-based computer systems which perform the specified functions or steps, or combinations of special purpose hardware and computer instructions.

[0193] It is never intended to limit the steps of a method to the order in which such steps are presented unless expressly stated in the method claim. Thus, no inference should be drawn that implies an order to steps or flow of operations is implied by their presentation in any claim or in the specification. This applies regardless of any non-expressive basis for interpretation, including: logical problems with the arrangement of steps or operations; ordinary meanings derived from grammatical organization or punctuation; the number or type of embodiments described in the specification.

[0194] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. While various specific embodiments have been disclosed in the foregoing, one skilled in the art will understand that the spirit and scope of the claims allow for equivalent modifications. In particular, features of the above-described embodiments that are not mutually exclusive can be combined with each other. The patentable scope of the present disclosure is defined by the claims, and can include other examples that occur to those skilled in the art. For example, at least one of the power conversion components, such as a transformer, can be located at least partially in the tower or base rather than the nacelle. Such other examples are intended to fall within the scope of the claims if they have structural elements identically the same as the literal language of the claims, or if they contain equivalent structural elements with insubstantial differences from the literal language of the claims.

[0195] Reference numerals

[0196] Wind turbine 100, 400, 400'

[0197] nacelle 102, 402

[0198] tower 104

[0199] yaw system 105

[0200] rotor 106

[0201] weather mast 107

[0202] blade 108

[0203] pitch system 109

[0204] hub 110

[0205] low speed shaft 112

[0206] gearbox 114

[0207] generator 118

[0208] generator stator 120

[0209] generator rotor 122

[0210] control system 200

[0211] turbine controller 202

[0212] processor 204

[0213] synchronization switch 206

[0214] memory 207

[0215] stator bus 208

[0216] communication module 209

[0217] power conversion assembly 210, 410

[0218] sensor interface 211

[0219] rotor bus 212

[0220] transformer circuit breaker 214

[0221] system bus 216

[0222] rotor filter 218

[0223] filter bus 219

[0224] rotor side power converter 220

[0225] line side power converter 222

[0226] line side power converter bus 223

[0227] Line filter 224

[0228] Line bus 225

[0229] Line contactor 226

[0230] Conversion circuit breaker 228

[0231] Conversion circuit breaker bus 230

[0232] Connection bus 232

[0233] Electric power main transformer 234

[0234] Generator side bus 236

[0235] Grid circuit breaker 238

[0236] Breaker side bus 240

[0237] Distribution grid via grid bus 242

[0238] DC link 244

[0239] Positive rail 246

[0240] Negative rail 248

[0241] Capacitor 250

[0242] Current sensor 252

[0243] Current sensor 254

[0244] Current sensor 256

[0245] Temperature sensors 257, 258

[0246] Converter controller 262

[0247] Current sensor 264

[0248] Cooling system 430

[0249] Air cooling system 450

[0250] Internal grid 470

[0251] Method, method steps 1000-3200

[0252] Reactive power demand RPD

[0253] Active power demand APD

[0254] Stator temperature TGS

[0255] Bearing temperature TGB

[0256] temperature Ta-Td

[0257] parameter threshold Th*_parameter

[0258] cooling circuits C1-C4

[0259] fan F

[0260] heat exchangers H12, H34

[0261] power P

[0262] heat Q

Claims

1. A method (1000, 2000, 3000) for operating a wind turbine (100, 400, 400') comprising a power conversion system configured to provide an electrical output power (P) to an electrical grid and an air cooling system (450) configured to cool ambient air (28a) in a cooling mode and to provide the cooled ambient air as cooled air (28c) to the power conversion system, the method (1000, 2000, 3000) comprising: • operating the air cooling system (450) in the cooling mode if at least one operating parameter (APD, RPD, TBS) of the power conversion system is equal to or greater than a respective threshold value (Th1_APD, Th1_RPD, Th1_TGB, Th1_TBS), • the air cooling system reducing a temperature of the ambient air to a cooled temperature of the ambient air in the cooling mode, the cooled temperature being lower than the temperature of the ambient air before the cooled ambient air is introduced into the power conversion system, the method being characterized in that the ambient air is received from outside the wind turbine.

2. The method (1000, 2000, 3000) of claim 1, wherein, The air cooling system (450) is operated in the cooling mode if at least one of the following conditions is met: • a reactive power demand (RPD) of the power conversion system is equal to or greater than a reactive power demand threshold value (Th1_RPD); • an active power demand (APD) of the power conversion system is equal to or greater than an active power demand threshold value (Th1_APD); • a temperature (Ta) of the ambient air (28a) is equal to or greater than an ambient temperature threshold value (Th_Ta); • a temperature (Tc) of the cooled air (28c) is equal to or greater than a cooled air temperature threshold value (Th1_Tc); • a temperature (TGS, TGB, Tc) of at least one power conversion component of the power conversion system is equal to or greater than a respective first temperature threshold value (Th1_TGS, Th1_TGB, Th1_Tc), the power conversion system generally comprising several power conversion components configured to facilitate a conversion of an input power into the electrical output power (P) if the input power is received from a rotor (106) of the wind turbine (100, 400, 400'), the rotor (106) comprising rotor blades (108); and • the temperature (TGS, TGB, Tc) of the at least one of the power conversion components is equal to or greater than a respective second temperature threshold value (Th2_GS, Th2_TGB, Th2_Tc) that is smaller than the respective first temperature threshold value (Th1_TGS, Th1_TGB, Th1_Tc).

3. The method (1000, 3000) of claim 2, wherein, The air cooling system (450) is operated in the cooling mode depending on the temperature of the at least one power conversion component.

4. The method (1000, 3000) of claim 2 or 3, wherein, The air cooling system (450) is operated in a cooling mode depending on at least one of a temperature of a gear box, a temperature of a power converter (220, 222), a temperature of a transformer and a temperature of a generator, in particular at least one of a temperature of a bearing of the generator (TGB) and a temperature of a stator of the generator (TGS).

5. The method (1000, 2000) of claim 2, wherein, The air cooling system (450) is operated in a cooling mode independent of a temperature of the at least one power conversion component of the power conversion system.

6. The method (1000, 2000, 3000) of any one of claims 2-3, further comprising reducing at least one of a reactive output power of the power conversion system and an active output power of the power conversion system if the temperature of the at least one power conversion component of the power conversion system is equal to or greater than a respective third temperature threshold (Th3_GS, Th3_TGB, Th3_Tc), the third temperature threshold (Th3_GS, Th3_TGB, Th3_Tc) being greater than at least one of the respective first temperature threshold (Thl_TGS, Thl_TGB, Thl_Tc) and the respective second temperature threshold (Th2_GS, Th2_TGB, Th2_Tc).

7. The method (1000, 2000, 3000) of any one of claims 2-3, comprising at least one of: • measuring a respective temperature; • receiving the reactive power demand (RPD); • receiving the active power demand (APD); • activating the cooling mode based on at least one of the measured temperature, the received reactive power demand (RPD) and the received active power demand (APD); • deactivating the cooling mode based on at least one of the measured temperature, the received reactive power demand (RPD) and the received active power demand (APD); and • removing heat (Q) from the power conversion system using the cooling air, in particular via a cooling system of the power conversion system, the cooling system being configured to receive the cooling air; • operating a cascade of three cooling circuits (Cl-C3) thermally coupled to each other; and • operating a cascade of four cooling circuits (Cl-C4) thermally coupled to each other.

8. A wind turbine (100, 400, 400’), comprising: • a rotor (106) comprising rotor blades (108); • an air cooling system (450) configured to receive ambient air (28a), cool the ambient air (28a) to below ambient air temperature and provide the cooled ambient air as cooling air (28c); • a power conversion system mechanically connected to the rotor (106), electrically connectable to a utility grid, configured to convert input power into electrical output power (P); and • a cooling system configured to receive the cooling air (28) and introduce the cooling air into the power conversion system in order to remove heat (Q) from the power conversion system, characterized in that the air cooling system (450) is configured to receive the ambient air (28a) from outside the wind turbine.

9. The wind turbine (100, 400, 400') according to claim 8, wherein The air cooling system (450) and the cooling system implement at least one of: three cooling circuits (C1-C3) in cascade thermally coupled to each other and four cooling circuits (C1-C4) in cascade thermally coupled to each other, wherein the air cooling system (450) is provided by an air conditioning system, wherein the air cooling system (450) is configured to remove heat from the ambient air at a rate of at least up to 15 kW, and / or wherein the air cooling system (450) is configured to remove heat from the ambient air at a cooling efficiency of at least 2.

10. The wind turbine (100, 400, 400') according to claim 8, wherein, The air cooling system (450) and the cooling system implement at least one of: three cooling circuits (C1-C3) in cascade thermally coupled to each other and four cooling circuits (C1-C4) in cascade thermally coupled to each other, wherein the air cooling system (450) is provided by an air conditioning system, wherein the air cooling system (450) is configured to remove heat from the ambient air at a rate of at least up to 20 kW, and / or wherein the air cooling system (450) is configured to remove heat from the ambient air at a cooling efficiency of at least 2.

11. The wind turbine (100, 400, 400') according to claim 8, wherein The air cooling system (450) and the cooling system implement at least one of: three cooling circuits (C1-C3) in cascade thermally coupled to each other and four cooling circuits (C1-C4) in cascade thermally coupled to each other, wherein the air cooling system (450) is provided by an air conditioning system, wherein the air cooling system (450) is configured to remove heat from the ambient air at a rate of at least up to 23 kW, and / or wherein the air cooling system (450) is configured to remove heat from the ambient air at a cooling efficiency of at least 2.

12. The wind turbine (100, 400, 400') according to claim 9, wherein, wherein the air cooling system (450) is configured to remove heat from the ambient air at a cooling efficiency of at least 3.

13. The wind turbine (100, 400, 400') according to any of claims 8-11, wherein, The power conversion system comprises at least one power conversion component configured to facilitate conversion of an input power received from the rotor (106) into the electrical output power (P), wherein the power conversion system comprises at least one of a gearbox, a generator, a power conversion assembly and a transformer as respective power conversion components, wherein the cooling system is configured to remove heat from at least one of the power conversion components, wherein at least one of the power conversion components is arranged in a nacelle (102) of the wind turbine, wherein the air cooling system (450) is at least partially arranged in or at the nacelle, wherein the cooling system comprises at least one of a closed internal cooling circuit (C4) fluidly connected with the power conversion system to remove the heat, an open cooling circuit (C3) thermally coupled with the closed internal cooling circuit (C4) and configured to receive the cooling air (28c), a heat exchanger (H34) arranged between the open cooling circuit (C3) and the closed internal cooling circuit (C4), and a main cooler configured to receive the cooling air (28c), the main cooler typically comprising the heat exchanger and / or being implemented as a liquid-liquid heat exchanger or an air-liquid cooler, wherein the power conversion system is configured to convert the input power into active output power and reactive output power, and / or wherein the power conversion system is a DFIG system.

14. The wind turbine (100, 400, 400') according to claim 13, wherein The air-liquid cooler is an oil-gas cooler.

15. The wind turbine (100, 400, 400') of any one of claims 8-11, further comprising a controller communicatively coupled with at least one of the air cooling system (450), the power conversion system and at least one temperature sensor, the controller typically configured to perform the method (1000, 2000, 3000) according to any one of claims 1 to 7.

16. The wind turbine (100, 400, 400') according to claim 15, wherein The at least one temperature sensor is configured to measure a respective temperature of at least one of the ambient air, the cooling air, the power conversion system and at least one power conversion component of the power conversion system.

17. The wind turbine (100, 400, 400') according to claim 13, wherein The cooling system comprises at least one of a fan (F) and a heat exchanger (H34) of the power conversion system which can be provided with the cooling air (28c).

18. The wind turbine (100, 400, 400') of any one of claims 17, wherein, The cooling system comprises a respective fan and / or heat exchanger for at least one power conversion component of the power conversion system.

19. The wind turbine (100, 400, 400') of any one of claims 18, wherein, The at least one power conversion component comprises the generator.

20. The wind turbine (100, 400, 400') according to any of claims 8-11, wherein, The power conversion system and the air cooling system (450) can be connected with an internal electrical power distribution system, and / or wherein the air cooling system (450) can be provided with electrical power (Pi) from the power conversion system.

21. A computer program product or a non-transitory computer readable storage medium comprising instructions which, when executed by one or more processors (204) of a system, cause the system to perform the method (1000, 2000, 3000) of any one of claims 1-7.

22. The computer program product or the non-transitory computer readable storage medium of claim 21, wherein the system comprises a controller of a wind turbine (100, 400, 400') of any one of claims 8 to 20.

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