Heating a wind turbine facility

Abstract

A method for heating a wind turbine facility includes: charging a DC link of an electrical converter connected with a wind turbine of the wind turbine facility; heating air inside the wind turbine facility with heat generated by a voltage limiting unit interconnected with the DC link, which includes a resistor adapted for dissipating electrical energy into heat for reducing a voltage in the DC link, when the voltage is above a threshold voltage; wherein the voltage limiting unit is controlled, such that the voltage limiting unit generates heat according to settings defined in a controller of the voltage limiting unit. The heating settings are changed based upon commands from a user interface. Furthermore, the DC link is charged by a grid side converter of the wind turbine facility with power from an electrical grid.

Claims

1. A method for heating a wind turbine facility, the method comprising: charging a DC link of an electrical converter connected with a wind turbine of the wind turbine facility; heating air inside the wind turbine facility with heat generated by a voltage limiting unit interconnected with the DC ink, which comprises a resistor adapted for dissipating electrical energy into heat for reducing a voltage in the DC link, when the voltage is above a threshold voltage; wherein the voltage limiting unit is controlled, such that the voltage limiting unit generates heat according to heating settings defined in a controller of the voltage limiting unit; wherein heating settings are changed based upon commands from a user interface; wherein the DC link is charged by a grid side converter of the wind turbine facility with power from an electrical grid.

2. The method of claim 1, wherein the voltage limiting unit is controlled, such that the resistor is heated to a defined heating temperature.

3. The method of claim 2, wherein the heating temperature is lower than a maximal temperature, which maximal temperature is used for limiting a temperature of the resistor during reducing the voltage in the DC link, when the voltage is above a threshold voltage; and/or wherein the voltage limiting unit is controlled, such that the heating temperature of the resistor is between 10 C. and 80 C.

4. The method of claim 2, wherein the voltage limiting unit is controlled, such that the resistor generates heat with a defined heating power; and/or wherein the voltage limiting unit is controlled, such that the resistor has a constant heating power.

5. The method of claim 2, further comprising: controlling a blower for distributing the heated air inside the wind turbine facility.

6. The method of claim 1, wherein the heating temperature is lower than a maximal temperature, which maximal temperature is used for limiting a temperature of the resistor during reducing the voltage in the DC link, when the voltage is above a threshold voltage; and/or wherein the voltage limiting unit is controlled, such that the heating temperature of the resistor is between 10 C. and 80 C.

7. The method of claim 6, wherein the voltage limiting unit is controlled, such that the resistor generates heat with a defined heating power; and/or wherein the voltage limiting unit is controlled, such that the resistor has a constant heating power.

8. The method of claim 6, further comprising: controlling a blower for distributing the heated air inside the wind turbine facility.

9. The method of claim 1, wherein the voltage limiting unit is controlled, such that the resistor generates heat with a defined heating power; and/or wherein the voltage limiting unit is controlled, such that the resistor has a constant heating power.

10. The method of claim 9, wherein the voltage limiting unit is controlled, such that the resistor generates heat with a defined heating power; and/or wherein the voltage limiting unit is controlled, such that the resistor has a constant heating power.

11. The method of claim 9, further comprising: controlling a blower for distributing the heated air inside the wind turbine facility.

12. The method of claim 1, further comprising: controlling a blower for distributing the heated air inside the wind turbine facility.

13. The method of claim 12, further comprising: controlling a blower for distributing the heated air inside the wind turbine facility.

14. The method of claim 1, further comprising: estimating and/or measuring a temperature of the resistor and/or of the air heated by the resistor; controlling the voltage limiting unit such that the estimated and/or measured temperature of the resistor and/or the air heated by the resistor is equal to a desired temperature.

15. The method of claim 1, further comprising: when the voltage in the DC link is above a threshold voltage, controlling the voltage limiting unit such that electrical energy is dissipated into heat until the DC link voltage has fallen below the threshold voltage, independently of the heating settings.

16. The method of claim 1, wherein the DC link is charged by a generator side converter of the wind turbine facility.

17. A heating system for a wind turbine facility, the heating system comprising: a voltage limiting unit electrically interconnected to a DC link of an electric converter of the wind turbine facility with a resistor for dissipating electrical energy from the DC link into heat; a controller adapted for controlling the electrical converter and the voltage limiting unit, the controller operable to direct the heating system to: charge the DC link of the electrical converter connected with a wind turbine of the wind turbine facility; heat air inside the wind turbine facility with heat generated by the voltage limiting unit interconnected with the DC ink, which comprises the resistor adapted for dissipating electrical energy into heat for reducing a voltage in the DC link, when the voltage is above a threshold voltage; wherein the voltage limiting unit is controlled, such that the voltage limiting unit generates heat according to heating settings defined in the controller of the voltage limiting unit; wherein heating settings are changed based upon commands from a user interface; wherein the DC link is charged by a grid side converter of the wind turbine facility with power from an electrical grid.

18. A wind turbine facility, comprising: a wind turbine tower, in which the converter, the DC link and the voltage limiting unit are arranged; and a heating system according to claim 9.

19. The heating system of claim 18, further comprising: a pipe system interconnected with the voltage limiting unit, such that heated air from the voltage limiting unit is conducted by the pipe system within the wind turbine facility.

20. The wind turbine facility of claim 18, wherein the resistor of the voltage limiting unit is arranged on a lower level as the converter and/or the DC link in the wind turbine tower.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The subject-matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in the attached drawings.

(2) FIG. 1 schematically shows a circuit diagram for a wind turbine facility according to an embodiment of the invention.

(3) FIG. 2 shows a perspective view of a voltage limiting unit for a wind turbine facility according to an embodiment of the invention.

(4) FIG. 3 schematically shows a wind turbine facility according to an embodiment of the Invention.

(5) FIG. 4 shows a flow diagram for a method for heating of a wind turbine facility according to an embodiment of the invention.

(6) The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(7) FIG. 1 shows an electrical converter 10, which is adapted for converting electrical power from a generator 12, which is driven by a wind turbine 14, into electrical power supplied to an electrical grid 16. It may be possible that a transformer 18 is arranged between the converter 10 and the grid 16.

(8) The converter 10 comprises a grid side converter 20 and a generator side converter 22, which are interconnected by a DC link 24, which may comprise one or more DC link capacitors 26.

(9) During normal operation, the generator side converter 22 rectifies an AC voltage into a to DC voltage to be supplied to the DC link and the grid side converter 20 converts the voltage of the DC link into a further AC voltage to be supplied to the grid. In this case, power flows from the generator 12 to the grid 16. During a low voltage ride through, i.e. a voltage drop in the grid, it may be possible that the power flow inside the grid side converter 20 becomes lower or even may be reversed. In this case, the DC link voltage starts to rise and above a threshold voltage has to be limited.

(10) Therefore, a voltage limiting unit 28 is connected in parallel to the DC link capacitor 26. The voltage limiting unit 28 comprises a resistor 30 and a semiconductor switch 32 connected in series. When the semiconductor switch 32 (such as a thyristor) is opened, a current starts to flow though the resistor 30 which is supplied from the voltage in the DC link capacitor 26. In the resistor 30, the electrical energy is transformed into heat energy, which, for example, may be dissipated by cooling fins. In such a way, the DC link voltage may be lowered by switching on the voltage limiting unit 28.

(11) It may be possible that the DC link 24 is a split DC link with two DC link capacitors 26 connected in series. In this case, the voltage limiting unit 28 may comprise a series connection of a resistor 30 and a semiconductor switch 32 connected in parallel to each DC link capacitor 26. The voltage limiting unit 28 may have a positive and a negative half. Each half may be connected to a neutral point of the DC link 24 by the respective semiconductor switch 32.

(12) The converters 20, 22 and the voltage limiting unit 28 are controlled by a controller 34, which may comprise several subcontrollers, for example a subcontroller for the grid side converter 20 and a subcontroller for the generator side converter 22.

(13) The controller 34 may monitor the DC link voltage and may switch the voltage limiting unit 28 on to lower the DC link voltage, when it rises above a threshold voltage. If a voltage above the threshold voltage is detected, the semiconductor switch 32 is switched on and the resistor 30 may be interconnected to the capacitor 26 as long as the DC link voltage is above the threshold voltage. This may be seen as a protection mode of the voltage limiting unit 28.

(14) Furthermore, as will be explained in detail below, the controller 34 may control the voltage limiting unit 28 in such a way that the voltage limiting unit 28 generates heat according to defined heating settings that may be stored in the controller such that the voltage limiting unit may be used as a heating device. This may be seen as a heating mode of the voltage limiting unit 28.

(15) FIG. 2 shows a voltage protection unit 28, which comprises a housing 36 in which the one or more resistors 30 and one or more semiconductor switches 32 are accommodated. The one or more resistors 30 and one or more semiconductor switches 32 may be connected via connectors 38 provided by the housing with the DC link 24 and the controller 34.

(16) The one or more resistors 30 are thermally connected to cooling fins 40 inside the housing 36. The housing 36 has openings, which allow an air stream through the fins 40, which may be driven by thermal convection. The heat from the resistor(s) 30 may be dissipated into the air, which is heated while cooling the resistor(s) 30. When the resistor(s) 30 are constantly heated with a moderate temperature, the heated air may be used for heating rooms/spaces, in which the voltage limiting unit 28 is installed.

(17) FIG. 3 shows a wind turbine facility 42, which comprises a wind turbine tower 44 erected on a basement 46. The basement 46 may comprise a concrete block, while the wind turbine tower 44 may comprise a steel pipe or a concrete pipe, which on its tip carries a nacelle with the generator 12 and the wind turbine 14. The wind turbine facility 42 comprises several levels and/or floors 48, which may be accessed via a door 51 in the wind turbine tower 44 and/or which may separate the interior 50 of the wind turbine tower 44 into different spaces and/or rooms.

(18) For example, a level 48 may house the grid side converter 20, the generator side converter 22, which are connected via electrical cables 52 to the grid 16 and to the generator 12. Also the controller may be positioned at the same level 48.

(19) FIG. 3 shows two different possible positions for the voltage limiting unit 28. The voltage limiting unit 28 may be housed on the same level 48 or on a different level, in particular on a level below the level, in which other converter components 20, 22, 24 are installed. In both cases, the voltage limiting unit 28 may be connected via an electrical cable 54 with the DC link 24.

(20) When the voltage limiting unit 28 is operated in a heating mode, it may heat air in the wind turbine tower 44 to a temperature comfortable for persons commissioning the wind turbine facility 42 or maintaining the wind turbine facility 42. For example, the interior 50 of the wind turbine facility 42 or at least parts of it may be heated to a temperature about 20 C. It also may be possible that the heating mode of the voltage limiting unit 28 is used to prevent the interior 50 of the wind turbine facility 42 or at least parts of it from freezing. In such a case, the air may be heated to about 2.

(21) One possibility is to use the voltage limiting unit 28 for heating by thermal convection. In this case, only components already installed in a conventional wind turbine facility 42 may be used for heating. Only the programming of the controller 34 may be changed.

(22) When the voltage limiting unit 28 is placed on the basement and/or the lowest level 48, the complete interior 50 of the wind turbine tower 44 may be heated by convection.

(23) Another possibility is to install a pipe/ventilation system 56 in the wind turbine facility, which comprises pipes for distributing heated air inside the wind turbine tower 44. For example, heated air from the voltage limiting unit 28 may enter the pipe/ventilation system 56 by thermal convection and may be distributed to other levels 48.

(24) A blower 58 may be installed in the pipe/ventilation system 56 for actively distributing the heated air with the pipe/ventilation system 56. The blower 58 may be turned on, when the voltage limiting unit 28 is used in heating mode and/or protection mode. The blower 58 may be turned off, when the voltage limiting unit 28 is turned off.

(25) Furthermore, a temperature sensor 60 may be installed in the pipe/ventilation system 56 and/or at the resistor 30. The signal from the temperature sensor 60 may be evaluated by the controller 34 for controlling the voltage limiting unit 28 in the heating mode and/or the protection mode.

(26) The voltage limiting unit 28, the blower 58, the temperature sensor 50, the pipe/ventilation system 56 and the controller 34 may be seen as a heating system 62 of the wind turbine facility 42.

(27) FIG. 3 shows a flow diagram for a method that may be performed by the heating system 62 under the control of the controller 34.

(28) In step S10, a person inside the wind turbine tower 44 changes heating settings with commands from a user interface 64 that, for example, may be provided by the controller 34.

(29) For example, the person may simply switch on the heating system 62 or may change a temperature that should be produced by the heating system 62. The heating settings may comprise an operation state of the heating system 62 (on/off), a desired resistor temperature, a desired air temperature, a desired heating power, an operation state of the blower 58, etc.

(30) In step S12, the heating system 62 starts to heat air inside the wind turbine facility 42 with heat generated by the voltage limiting unit 28.

(31) Since the heat is generated from electrical energy, the DC link 24 has to be charged. The DC link may already be charged, when the converter 10 is operating, i.e. converting electrical energy from the generator 12 into electrical energy to be supplied to the grid 16. The DC link 24 is then charged by the generator side converter 22.

(32) Otherwise, when the DC link 24 is not charged, it has to be charged. This may be done with the grid side converter 22 with power from an electrical grid 16. In this context it has to be noted that the heating system 62 may be operated when the wind turbine 14 is not working and even in the case, when the wind turbine 14 and other parts of the wind turbine facility 42 are not yet installed.

(33) For example, it may be possible to heat the interior 50 of the wind turbine facility 42 during commissioning and/or maintenance.

(34) For controlling the heating system 62, the controller may estimate a temperature of the resistor 30 and/or of the air heated by the resistor 30. This may be performed with a model of the voltage limiting unit 28 and/or further components of the heating system 62.

(35) It also may be possible that the controller 34 measures the temperature of the resistor 30 and/or of the air heated by the resistor 30. This may be performed with aid of the sensor 60.

(36) Based on this estimated/measured temperature, the controller 34 may control a power supply of the voltage limiting unit 28 such that the estimated and/or measured temperature of the resistor 30 and/or the air heated by the resistor is equal to a desired temperature. For example, the controller may switch the semiconductor switch 32 on and off to limit the power dissipated by the resistor.

(37) Furthermore, it may be possible that the heating power of the resistor 30 is controlled to be a defined heating power (for example set in the heating settings). For example, this heating power may be set to a constant value.

(38) In step S12, also the blower 58 for distributing the heated air inside the wind turbine facility 42 may be controlled. For example, the blower 58 may be switched on, when demanded by the heating settings of the controller 34 and/or when an air temperature inside the pipe/ventilation system 56 is getting too high.

(39) In step S14, the controller 34 detects that the voltage in the DC link 24 is above a threshold voltage. In this case, the voltage limiting unit 28 is used in protection mode. To fast dissipate energy and to fast lower the DC link voltage, the heating power of the resistor and/or its temperature are not (or nearly not) limited any more. In protection mode it may be that the resistor 30 reaches a temperature of several 100 C. It may be that also in protection mode, the heat and/or temperature generated by the resistor 30 is controlled to protect the voltage limiting device 28. During the protection mode, the temperature of the resistor 30 may be estimated and/or measured by the sensor 60 and used for protecting the resistor 30 from a damage.

(40) However, the control settings of the protection mode may be much higher than in the heating mode. For example, the maximal temperature of the resistor during the protection mode may be 500 C., wherein the heating temperature during the heating mode may be between 10 C. and 80 C.

(41) While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practising the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. A single processor or controller or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

LIST OF REFERENCE SYMBOLS

(42) 10 converter 12 generator 14 wind turbine 16 electrical grid 18 transformer 20 grid side converter 22 generator side converter 24 DC link 26 DC link capacitor 28 voltage limiting unit 30 resistor 32 semiconductor switch 34 controller 36 housing 38 connectors 40 cooling fins 42 wind turbine facility 44 wind turbine tower 46 basement 48 level 50 interior of wind turbine facility 51 door 52 electrical cable 54 electrical cable 56 pipe/ventilation system 58 blower 60 temperature sensor 62 heating system