Method for operating a wind turbine

Abstract

A method for operating a wind turbine comprising an aerodynamic rotor with an approximately horizontal axis of rotation, an electrical generator and operating devices is disclosed, wherein the wind turbine is intended for feeding electrical energy into an electrical supply grid, and is kept in a starting state for starting the generator while the wind turbine cannot be completely put into operation, in particular the generator cannot be started.

Claims

1. A method for operating a wind turbine comprising an aerodynamic rotor with an approximately horizontal axis of rotation, an electrical generator and power-consuming devices, the method comprising: configuring the wind turbine for feeding electrical energy into an electrical supply grid; and keeping the wind turbine in a starting state for starting the generator while the wind turbine cannot be put into operation, wherein keeping the wind turbine in the starting state includes aligning the wind turbine into the wind by: setting at least one of a tolerance angle to a first tolerance angle, and a waiting time to a first waiting time when the generator is in operation, and setting at least one of: the tolerance angle to a second tolerance angle, and the waiting time to a second waiting time when the generator is not in operation; and adjusting an azimuth angle of the wind turbine when an azimuth alignment at least one of: deviates from an optimum alignment into the wind by more than the tolerance angle, and deviates from the optimum alignment into the wind for longer than the waiting time.

2. The method according to claim 1, wherein the wind turbine cannot be put into operation when the wind turbine cannot be started because of at least one of: sufficient wind is not available; feeding into the electrical supply grid is not possible or permissible; and local regulations temporarily prohibit starting of the generator to avoid a disruptive shadow that is being cast or development of disruptive noise.

3. The method according to claim 1, wherein: keeping the wind turbine in the starting state for starting the generator comprises using energy from at least one energy storage.

4. The method according to claim 1, wherein keeping the wind turbine in the starting state includes: heating rotor blades of the aerodynamic rotor of the wind turbine to avoid a formation of ice or to thaw ice.

5. The method according to claim 4, wherein the tolerance angle and the waiting time depend on at least one of: whether the generator is in operation, and a wind speed.

6. The method according to claim 1, comprising: when there is no wind or when a measurement of wind direction is not available at the wind turbine, adjusting an azimuth position based on a wind direction measurement transmitted from a measuring mast or a weather station.

7. The method according to claim 1, comprising: starting a heating device of rotor blades when, based on a weather forecast, sufficient wind for operating the wind turbine, including the generator, is expected within a preparation time period, wherein the sufficient wind is strong and persistent enough that energy required for heating the rotor blades can be generated.

8. The method according to claim 1, comprising: operating a control system for at least one of preventing a formation of ice and removing ice that has formed when the generator is not being operated.

9. The method according to claim 1, comprising: calculating or predicting a starting time when the generator is expected to be started; bringing the wind turbine into the starting state for starting the generator a predetermined lead time before the starting time; and keeping the wind turbine ready in the starting state until the generator is started.

10. A wind turbine configured to perform the method according to claim 1.

11. The wind turbine according to claim 10, wherein at least one of the wind turbine or an electrical system network connected to the at least one of the wind turbine has at least one energy storage for storing energy and for delivering electrical energy, wherein the at least one energy storage is dimensioned such that it is able to store sufficient energy for heating rotor blades of the wind turbine.

12. The wind turbine according to claim 11, wherein the at least one energy storage is able to store enough energy to at least one of: allow rotor blades that are completely iced to be thawed, and allow the rotor blades to be heated with a maximum heating power for a predetermined heating time period.

13. The wind turbine according to claim 12, wherein the heating time period is at least one hour.

14. The wind turbine according to claim 13, wherein the heating time period is at least three hours.

15. A wind farm comprising at least two wind turbines according to claim 10.

16. The wind farm according to claim 15, comprising at least one energy storage dimensioned such that in the wind farm altogether sufficient energy for heating rotor blades of the wind turbines can be stored, wherein the sufficient energy allows the rotor blades of all the wind turbines of the wind farm that are completely iced to be thawed, allows the rotor blades of all the wind turbines of the wind farm to be heated with a maximum heating power for a predetermined time period that is at least one hour.

17. The method according to claim 1, wherein at least one of the tolerance angle and the waiting time are inversely proportional to the wind speed.

18. The method according to claim 1, further comprising: selecting at least one of a third tolerance angle and a third waiting time when the generator is not in operation when a wind direction measurement is obtained from a measuring mast or a weather station.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention is explained more precisely below by way of example on the basis of embodiments with reference to the accompanying figures.

(2) FIG. 1 schematically shows a wind turbine.

(3) FIG. 2 schematically shows a wind farm.

(4) FIG. 3 shows four time diagrams for illustrating a heating process by way of example according to an embodiment of the invention.

DETAILED DESCRIPTION

(5) FIG. 1 shows a wind turbine 100 comprising a tower 102 and a nacelle 104. Arranged on the nacelle 104 is a rotor 106 with three rotor blades 108 and a spinner 110. During operation, the rotor 106 is set in a rotating motion by the wind and thereby drives a generator in the nacelle 104.

(6) FIG. 2 shows a wind farm 112 comprising by way of example three wind turbines 100, which may be identical or different. The three wind turbines 100 are consequently representative of in principle any number of wind turbines of a wind farm 112. The wind turbines 100 provide their power, that is in particular the electricity generated, by way of an electrical farm system 114. In this case, the respectively generated electricity or power of the individual wind turbines 100 is added together and there is usually a transformer 116, which steps up the voltage in the farm to then feed it into the supply grid 120 at the feeding-in point 118, which is also generally referred to as the PCC. FIG. 2 is only a simplified representation of a wind farm 112, which, for example, does not show any control system, although of course there is a control system. Also, for example, the farm system 114 may be differently designed, in that, for example, there is also a transformer at the output of each wind turbine 100, just to mention one other exemplary embodiment.

(7) FIG. 3 schematically shows in the lowermost diagram a possible profile of a wind speed. Accordingly, for the first 180 minutes, that is to say three hours, the wind speed V.sub.W lies below a depicted starting wind speed, which for simplicity is entered here as two meters per second. Exact values of the wind speed are immaterial herein. The diagrams of FIG. 3 nevertheless attempt to show a curve that is also realistic in terms of the numerical values. However, the representations are schematic and the interrelationships that are shown and explained should be also understood as schematic interrelationships, and there may particularly also be drawing inaccuracies.

(8) At 180 minutes, the wind speed V.sub.W then increases such that it exceeds the starting wind speed V.sub.WStart. At approximately 240 minutes, that is to say one hour later, the wind speed has then settled at a value of approximately 10 meters per second. In the case of this representation, a nominal wind speed is set at 12 meters per second, and therefore even after 240 minutes the wind speed still remains below the nominal wind speed. The representation therefore shows an entirely realistic case, in which the wind speed increases from very light, that is so light that the wind turbine cannot be operated at all, to a higher value, which however still lies below the nominal wind speed V.sub.WN.

(9) The diagram additionally shows the power P.sub.G generated by the generator of the wind turbine. Here, the index G has been chosen to make clear the difference from the heating power P.sub.H in the diagram above it.

(10) The generator may therefore not generate any power for the first three hours, because the wind is too light. After three hours, the wind speed is then strong enough that the generator can be started, which was not possible before. The generator is therefore then started and generates a power corresponding to the wind speed V.sub.W. This diagram shows by way of example the generated power in MW and here a wind turbine with a nominal power P.sub.N of 2 MW is assumed, which nowadays is equivalent to a wind turbine of a medium or even relatively small size. Because the wind speed V.sub.W does not reach its nominal wind speed V.sub.WN, the power P.sub.G generated by the generator also does not reach its nominal power value P.sub.N of 2 MW.

(11) It can also already be seen from these two lower diagrams that, at that particular time where the wind speed V.sub.W exceeds the starting wind speed V.sub.WStart of two meters per second, the generator is also immediately started and can generate power P.sub.G.

(12) This power P.sub.G is at first low, because the wind speed is also still very low. The linear increase in the power P.sub.G is in this case idealized. The profile could also look somewhat different, but would probably take a similar course if the wind speed V.sub.W were to behave as described.

(13) The third diagram from the bottom shows an exemplary profile of a heating power P.sub.H, which is likewise indicated in MW, the same dimensioning having been chosen as for the representation of the generator power P.sub.G. This diagram of the heating power P.sub.H shows an increase in the heating power P.sub.H at 30 minutes from zero to 0.2 MW, that is to say 200 kW. For the exemplary example, these 200 kW are the nominal value for the heating power P.sub.HN. This diagram is based on the idea that the wind turbine has determined after the depicted 30 minutes that the rotor blades are to be deiced, because the formation of ice has been detected. The control system therefore then carries out a deicing operation, in which the rotor blades are heated, which in the example assumed requires 200 kW of heating power.

(14) This heating of the rotor blades is consequently carried out even though the wind turbine is not in operation at all and, on account of the low wind speed, also cannot be put into operation at all. The generator therefore cannot be put into operation, and also cannot provide the heating power.

(15) The representation then assumes that this heating power is required for one and a half hours, that is to say from 30 to 120 minutes. At 120 minutes, the deicing is then successfully completed and the heating of the rotor blades is switched off, so that the heating power P.sub.H again assumes the value zero. The wind speed is thus still at a value at which the generator cannot be started.

(16) The uppermost diagram is intended to represent the energy balance of the wind turbine, but for simplicity takes into account here only the power P.sub.G generated by the generator and the heating power P.sub.H consumed by the heating device. It is assumed that at 30 minutes as the starting value the energy balance is zero. The energy consumption is identified by E.

(17) At 30 minutes, the heating operation therefore begins and continues for one and a half hours. Correspondingly, 300 kWh are consumed. At 120 minutes, therefore, the energy balance is negative with these 300 kW. This value persists for a further hour, that is until 180 minutes, because in this time no heating power P.sub.H is consumed nor generator power P.sub.G generated.

(18) At 180 minutes, the generator can then be started because the wind speed has just exceeded the starting wind speed V.sub.WStart. The rotor blades have been deiced and what is more the wind turbine is also otherwise ready to start, and the power can consequently be generated immediately in a way corresponding to the prevailing wind speed. This has already been described further above.

(19) As from 180 minutes, therefore, the energy E or energy balance then increases. After somewhat more than 40 minutes, the generator has then generated as much energy as has been consumed by the heating of the rotor blades. At the same time, the power continues to increase and the energy, as an integral of the power over time, correspondingly increases even more strongly. At 270 minutes, that is to say one and a half hours after the start of the generator, the energy is then approximately at 900 kWh.

(20) It should be noted that then, one and a half hours after the wind speed was sufficiently high to operate the wind turbine, the energy balance is a distinctly positive energy balance. One and a half hours is also the time that the rotor blades have been heated, that is from 30 to 120 minutes, so that in this representation one and a half hours was therefore required to deice the blades, and consequently make the wind turbine ready to start. If the heating, and consequently deicing, of the rotor blades had not already taken place, the wind turbine would have had to begin initially at 180 minutes. Since the shown heating operation has already heated with nominal power, that is to say nominal power P.sub.HN of the heating device, deicing, which starts at 180 minutes, would also not have been any quicker. In other words, the wind turbine would then have been ready to start at the earliest at 270 minutes. It would therefore have been able to generate power at the earliest at 270 minutes, and then at the earliest would have been able to contribute to a positive energy balance.

(21) In fact however it would also have initially required heating power, and consequently would have initially also consumed energy itself. For the sake of overall clarity, this variant is not depicted, but it should be immediately evident that, if the heating is only started at 180 minutes, by 270 minutes the energy would have dropped to 300 kWh. Therefore, in this example the proposed solution leads to an energy advantage of 1.2 MWh.

(22) This schematically illustrated process of FIG. 3 is particularly efficient whenever the energy required for heating can be taken from an energy store 101 (FIG. 1) that the wind turbine has initially charged itself with electrical energy. This is so because in this case expensive energy from the grid would not have to be bought in for the heating operation. What is more, it would also not necessarily be helpful when there are low wind speeds, with which therefore little wind power is fed into the grid in any case, also to take energy from the grid for heating. This would of course nevertheless be an option in the event that no energy store is available or the energy store is not filled.