METHOD OF OPERATING A WIND TURBINE

Abstract

A method of operating a wind turbine is provided. The method includes steps of monitoring the temperature of a component of the wind turbine to obtain a temperature progression for that component; determining the gradient of the temperature progression; and curtailing the power output of the wind turbine on the basis of the temperature progression gradient. The disclosed further describes a wind turbine including a curtailment module configured to curtail the power output of the wind turbine on the basis of a temperature progression gradient.

Claims

1. A method of operating a wind turbine, which method comprises: monitoring the temperature of a component of the wind turbine to obtain a temperature progression for that component; determining the gradient of the temperature progression; and curtailing the power output of the wind turbine on the basis of the temperature progression gradient, wherein the amount of curtailment is proportional to the gradient of a temperature progression.

2. The method according to claim 1, comprising: monitoring the ambient temperature for a component, and wherein the amount of curtailment is based also on the monitored ambient temperature.

3. The method according to claim 1, wherein curtailment is increased in response to an increase in gradient of a temperature progression.

4. The method according to claim 1, wherein curtailment is decreased in response to a decrease in gradient of a temperature progression.

5. The method according to claim 1, comprising: concluding the curtailment when the gradient of a temperature progression is less than a predetermined threshold gradient.

6. The method according to claim 1, wherein a threshold gradient is determined on the basis of empirical data.

7. The method according to claim 1, wherein a temperature progression is obtained for each of a plurality of components, and wherein a gradient is determined for each temperature progression.

8. The method according to claim 1, comprising: ranking the components according to temperature relevance, and wherein the power output of the wind turbine is curtailed on the basis of the temperature progression of the highest ranking component.

9. A wind turbine comprising a temperature monitoring arrangement configured to monitor the temperature of a component of the wind turbine; and a controller including a processing module configured to determine the temperature progression of the monitored temperature and to determine the gradient of the temperature progression; and a curtailment module configured to curtail the power output of the wind turbine on the basis of the temperature progression gradient, wherein the amount of curtailment is proportional to the gradient of a temperature progression.

10. The wind turbine according to 19, temperature monitoring arrangement comprises at least one temperature sensor arranged in proximity to a region of thermal significance of a component.

11. The wind turbine according to claim 9, wherein, for each of a plurality of temperature progressions, the controller is configured to compare its gradient to a threshold gradient.

12. The wind turbine according to claim 9, wherein a monitored temperature is the winding temperature of a generator.

13. The wind turbine according to claim 9, wherein a monitored temperature is the oil temperature of a bearing lubrication system.

14. The wind turbine according to claim 9, wherein a monitored temperature is the temperature in a converter unit.

15. A computer program product comprising a computer readable hardware storage device having computer readable program code stored therein, said program code executable by a processor of a computer system to implement a method according to claim 1 when the computer program is executed by the processor.

Description

BRIEF DESCRIPTION

[0025] Some embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

[0026] FIG. 1 is a block diagram of an embodiment of the wind turbine;

[0027] FIG. 2 shows exemplary curves to illustrate an embodiment;

[0028] FIG. 3 is a block diagram representing a further embodiment; and

[0029] FIG. 4 shows exemplary curves to illustrate a conventional art method.

DETAILED DESCRIPTION

[0030] FIG. 1 is a simplified block diagram representing an embodiment of the inventive wind turbine 1. The diagram indicates a number of components 10, 11, 12 that have temperature critical regions, and also a temperature monitoring arrangement with an exemplary arrangement of temperature sensors S placed to measure critical temperature(s). Here, a temperature sensor S is placed to monitor a temperature of the generator windings in the generator 10, a temperature sensor S is placed to monitor the oil temperature of a gearbox lubrication system 11, and a temperature sensor S is placed to monitor the temperature in a converter unit 12. Each temperature sensor can report a temperature reading 10T, 11T, 12T at favorably brief intervals, for example once per minute, once every 30 seconds, etc.

[0031] The diagram indicates a wind turbine controller 14 (this can be realized locally to the wind turbine, or at a remote location for example in the case of a wind farm), which receives temperature readings 10T, 11T, 12T from the various temperature sensors S. The controller 14 includes a processing module 141 configured to determine the gradient 10G, 11G, 12G of each monitored temperature 10T, 11T, 12T. This can be done by applying a suitable algorithm that derives the gradient of the temperature progression recorded in the temperature readings. The controller 14 further includes a curtailment module 142 that can generate an appropriate power reference P.sub.ref, depending on the behavior of the temperature progressions. To this end, the controller 14 receives a threshold rate of increase 10, 11, 12 for each of the monitored components 10, 11, 12.

[0032] FIG. 2 illustrates the outcome of a sharply rising temperature as reported for example by the temperature sensor of the gearbox lubrication system 11. At the top, the diagram shows a graph of temperature 11T against time (X-axis). The power output P.sub.out of the wind turbine is shown in the center of the diagram. The lower part of the diagram represents gradient-based curtailment C.sub.gradient, where 0% curtailment corresponds to maximum power output (under the momentary wind conditions), and 100% curtailment essentially corresponds to shutdown.

[0033] Between time t.sub.1 and time t.sub.2, the oil temperature 11T exhibits a steep increase. The temperature gradient over a time period (e.g., between time t1 and time t2) can be estimated from the temperature progression 11TP as the slope of the linethe hypotenuse of the inferred triangleconnecting a first coordinate pair (at time t1) and a second coordinate pair (at time t2). The processing module determines that the rate of increase as indicated by hypotenuse H.sub.12 exceeds the threshold rate of increase 11X for that component 11. In response to this steep increase, the curtailment module 142 issues a power reference to curtail the power output P.sub.out, in this case curtailment by 40% of the rated power output P.sub.rated as indicated from time t.sub.2 onwards.

[0034] Between time t.sub.2 and time t.sub.3, the oil temperature 11T is still increasing, in this case at a rate that corresponds to the threshold rate of increase 11X for that component 11, as indicated by hypotenuse H.sub.23. The curtailment module 142 responds by issuing a power reference to curtail the power output P.sub.out to a less severe degree, in this case curtailment by 20% of the rated power output P.sub.rated. This is indicated from time t.sub.3 onwards.

[0035] The temperature of the gearbox lubricant continues to increase between time t.sub.3 and time t.sub.4, but at a significantly lower rate indicated by hypotenuse H.sub.34, i.e., at a rate that is less than the critical gradient 11X. The newly computed gradient may therefore be regarded as insignificant, and the actual temperature 11T may be regarded as acceptable for that component. In response, the curtailment module 142 ceases curtailment at time t.sub.4 onwards.

[0036] As illustrated in the diagram, the amount of curtailment is determined based on the amount by which the gradient H.sub.12, H.sub.23, H.sub.34 differs from the threshold gradient 11X. With this gradient-focused control approach, the amount of curtailment is kept to a favorable minimum, and only a relatively small amount of revenue is sacrificed as indicated by the brief dip in output power P.sub.out.

[0037] The discrete nature of this exemplary control approach is exaggerated in the diagram. The intervals between temperature measurements can be small, i.e., the sampling rate can be high. The processing module 141 can continually update a gradient computation with each new temperature sample. In this way, the curtailment curve C.sub.gradient can be updated at a rate similar to the sampling rate.

[0038] Of course, the temperatures in the various components increase and decrease essentially independently of each other. The controller 14 is configured to curtail the power output on the basis of the most relevant monitored temperature. To this end, the processing module can determine the most relevant temperature behavior. For example, an increase in temperature in a first component 10 may be considered more relevant than an increase in temperature in a second component 11 if the gradient 10G of temperature progression for the first component 10 exceeds its threshold gradient 10X, even if the measured temperature 11T of the second component 11 might be considered more critical than the measured temperature 10T of the first component 10. The considered curtailment in response to the temperature gradient 10G of the first component will in any case have a beneficial effect on the temperature of the second component 11, since the temporary and relatively minor curtailment (until the gradient 10G has decreased to below its threshold 10X) can allow the temperature of the second component 11 to decrease also.

[0039] In an alternative approach to resuming uncurtailed operation, the wind turbine controller may apply an incremental approach to ramp the output power back up towards the higher output level P.sub.rated.

[0040] FIG. 3 is a simplified block diagram representing a further embodiment of the invention, based on the embodiment of FIG. 1. Here also, temperature readings 10T, 11T, 12T are reported for the components 10, 11, 12, and the processing module 141 of the wind turbine controller 14 determines the gradient 10G, 11G, 12G of each monitored temperature 10T, 11T, 12T.

[0041] In this embodiment, the curtailment module 142 also receives an ambient temperature reading 10T.sub.ambient, 11T.sub.ambient, 12T.sub.ambient for each component 10, 11, 12. The curtailment module 142 is configured to assess each gradient 10G, 11G, 12G in view of the corresponding ambient temperature reading 10T.sub.ambient, 11T.sub.ambient, 12T.sub.ambient. For example, for a specific component, a steep gradient in combination with a low ambient temperature would indicate the need for more severe curtailment in order to bring down the temperature of that component. Similarly, a mild gradient in combination with a low ambient temperature would indicate that curtailment is not necessarily required, since the low ambient temperature may be enough to keep the temperature of that component within safe limits. The curtailment module 142 can then generate an appropriate power reference P.sub.ref on the basis of the received information 10G, 11G, 12G, 10X, 11X, 12X, 10T.sub.ambient, 11T.sub.ambient, 12T.sub.ambient.

[0042] FIG. 4 shows a conventional art approach to power output curtailment in response to temperature. The diagram shows the temperature progression T.sub.comp of a wind turbine component. The wind turbine is generating its rated power output P.sub.rated. When the temperature exceeds a certain upper threshold T.sub.max at time t.sub.0, the wind turbine output power P.sub.out is curtailed as shown here, by 40% of the rated power output P.sub.rated. This state of reduced power output is maintained until the temperature decreases to a predetermined acceptable level T.sub.OK at time t.sub.OK, at which point the power output can be increased again. However, by simply waiting for the temperature to decrease to a pre-determined level, even though safe operation at a higher temperature is possible, significant revenue may be sacrificed.

[0043] Although the present invention has been disclosed in the form of embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0044] For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements.