TECHNICAL FIELD The present invention generally relates to the field of wind power. In particular, the invention relates to a method and a control unit for controlling one or several of warning lights in a wind turbine site.

Background

Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electrical power. Large wind farms consist of several of individual wind turbines which are connected to the electric power transmission network. For new constructions, onshore wind is an inexpensive source of electricity, competitive with or in many places cheaper than fossil fuel plants.

According to authority regulation high wind turbines should be provided with warning lights that prevent air traffic from colliding with the wind turbines. A significant problem with warning lights on wind turbines are that if the wind turbines are located close to residential blocks, the warning lights may disturb those living in the area.

Another problem is that these lights often require high amount of power, since the lights need to have high output power in order appropriately warn approaching air craft's.

It is therefore conceivable to assume that a market incentive exists to remove the mentioned limitations one way or the other. However, despite this incentive, and despite prior attempts to overcome problems relating to warning lights on wind turbines there is still a need for an improved solution for warning lights on wind turbines which solution solves or at least mitigates at least one of the above mentioned problems. SUMMARY OF THE INVENTION

It is therefore an object of the present invention to alleviate the above limitations and to provide arrangements and methods that reduces the problem of light pollution from warning lights in a wind turbine site.

According to a first aspect, the present invention relates to a method in a control unit for controlling one or several of warning lights in a wind turbine site, the one or several of warning lights, lights up an air territory of the wind turbine site. The method comprising the following steps: receiving RADAR, Radio Detection and Ranging, information from one or several RADAR units observing said air territory; determining on and/or off decisions for one or several of the warning lights in the set based on objects positions and movements in the air territory from the RADAR information; wherein the on and/or off decisions are determined such as to minimize the number of on decision and maximize the number of off decision in order to minimize light pollution from the warning lights, and turning on and/or off the warning lights according to the on and/or off decisions.

Thus, an object of the present invention is achieved by not turning on all warning lights every time there is an approaching object in the air territory of the wind turbine site. According to an idea of the present invention is only one or a subset of the warning lights, required to warn an approaching object in the air territory, turned on when there is an approaching object in the air territory. This significantly reduces the light pollution from the waning lights in the wind turbine site.

According to a second aspect, the present invention relates to a control unit for controlling one or several of warning lights in a wind turbine site. The one or several of warning lights, lights up an air territory of the wind turbine site, the control unit comprising: receiving means 210 configured to receive RADAR, Radio Detection and Ranging, information from one or several RADAR units observing said air territory. Processing means 220 configured to determine on and/or off decisions for one or several of the warning lights based on objects positions and movements in the air territory from the RADAR information, wherein the on and/or off decisions are determined such as to minimize the number of on decision and maximize the number of off decision in order to minimize light pollution from the warning lights. The control unit further comprises control means configured to turn on and/or off the warning lights according to the on and/or off decisions.

One of the main advantages of the present invention is that the solution reduces the problem of light pollution in urban areas. In many cases light pollution prevents the planning and permission for wind turbine sites. Thus, it is desirable to try to reduce the use of warning lighting as much as possible, without compromising flight safety.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects, advantages and effects as well as features of the invention will be more readily understood from the following detailed description of exemplary embodiments of the invention when read together with the accompanying drawings, in which:

Figure 1 illustrates a wind turbine site in which an exemplary embodiment of the present invention is implemented.

Figure 2 illustrates a control unit 200 according to an exemplary embodiment.

Figure 3 illustrates a flowchart of a method in a control unit 200 according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like reference signs refer to like elements.

Figure 1 illustrates a wind turbine site in which an exemplary embodiment of the present invention is implemented. In this exemplary embodiment the wind turbine site comprises 6 wind turbines 10. A warning light system 100 according to an exemplary embodiment of the present invention consists mainly of one or several RADARs 110, one or several control units 200 (not shown) and the warning lights (not shown). The RADARs 110 and the warning lights are known to a person skilled in the art and will not be described in detail. The RADARs 110 measure different types of properties about objects in the air territory and creates RADAR information. In one exemplary embodiment of the present invention the RADARs 110 measure position and speed of object in the air territory and from those measurements creates the RADAR information. The invention is however not limited to RADAR information containing only position and speed. The RADAR information can also contain other types of information about objects in the air territory. In this example of the wind turbine site there are six RADAR 110 that each covers different sub volumes of the air territory. In wind turbine sites consisting of several wind turbines the RADARs are preferably positioned in the site's periphery so that 360 degree coverage of the wind turbine site is obtained.

The Radar information is then received by a control unit 200 via a CAN bus or such. Communication between the RADARS and the control unit 200 can either be by means of a wired standard bus (Ethernet, CAN, or the like). Alternatively, can a wireless connection be used. Figure 2 illustrates a control unit 200 for controlling one or several of warning lights in a wind turbine site. The control unit 200 can for instance be used to control one or several warning lights in the wind turbine site illustrated in figure 1. The one or several warning lights, which are controlled by the control unit 200, light up an air territory of the wind turbine site. In exemplary embodiments of the control unit 200 according to present invention is the air territory the outside volume domain of the wind turbine site. In other exempla ry embodiment of the control unit 200 is the air territory both the outside volume domain of the wind turbine site and the inside volume domain of the wind turbine site.

According to an idea of the present invention it is not necessary to turn on all warning lights every time there is an approaching object in the air territory of the wind turbine site. According to an exemplary embodiment of the present invention is only one or a subset of the warning lights turned on if there is an approaching object in the air territory illuminated by the warning lights of the wind turbine site. An advantage with this solution is that the light pollution from the warning lights is significantly reduced since only the warning light that are required to warn the approaching object are turned on.

The control unit 200 comprises receiving means 210 configured to receive RADAR, Radio Detection and Ranging, information from one or several RADAR units observing the air territory. If only one RADAR is used that RADAR is preferably observing the entire air territory of the wind turbine site. In an exemplary embodiment of the control unit 200 is the receiving means 210 further configured to receive RADAR information from several RADAR units each observing different sub volumes of said air territory. In a preferred embodiment of the control unit 200 are the sub volumes overlapping. An advantage with using several RADARs is that a RADAR that only observes a sub volume of the air territory is much cheaper and simpler RADAR than a RADAR that is capable of observing the entire air territory. The warning lights system can when using several RADARs each observing sub volumes of the air territory be produced at a lower cost compared to if only one RADAR that observers the entire air territory is used. Another advantage with using several RADARs that each only observes a sub volume of the air territory is that such solution requires less maintenance. This since these RADARs do not comprises any moving parts. The receiving means 210 can be configured to receive the RADAR information via a wired connection or via a wireless connection. The RADAR information can be directly received via a wired or wireless communication link from the one or several RADARs or received via a wired or wireless communication link from another control unit 200 to other unit in the system. The RADAR information comprises in an exemplary embodiment of the control unit 200 distances to the objects, speed to the objects, but the RADAR information can in other exemplary embodiments also contain other information such as the direction of the speed, the strength of the eco which can give information about the size of the object.

The control unit 200 further comprises processing means 220 configured to determine on and/or off decisions for one or several of the warning lights based on objects positions and movements in the air territory from the RADAR information. The on and/or off decisions are determined in order to minimize the number of on decision and maximize the number of off decision in order to minimize light pollution from the warning lights. The Radar information that is received by the receiving means 210 comprises information about objects in the air territory of the wind turbine site. The RADAR information is used by the processing means 220 to determine which warning lights that should be turned on and which warning lights that should be turned off. As mentioned earlier, it is not necessary to turn on all warning lights when an aircraft approaches the wind turbine site. In an exemplary embodiment where each RADAR has a fixed coverage in the form of a sector, the processing means 220 can from the RADAR information determine which direction the object is coming from and based on this determine which warning lights that should be turned on and/or off.

As mentioned before in an exemplary embodiment of the control unit 200, the receiving means 210 receives RADAR information from the several RADARs observing overlapping sub volumes of the air territory. In this exemplary embodiment the processing means 220 determines on and/or off decisions for one or several of the warning lights in the set based on objects positions and movements in the air territory from the RADAR information from the several RADARs. As in other exemplary embodiment the on and/or off decisions are determined in order to minimize the number of on decision and maximize the number of off decision in order to minimize light pollution from the warning lights. An advantage with this embodiment is that the accuracy of the determination made by the processing means 220 are improved since RADAR information from several RADARs is used. Since each RADAR is observing overlapping sub volumes information about an object is received from several RADARs, which improves the objects positioning and determination of movements made by the processing means 220.

Referring back to the example in figure 1 and assume that an object comes in from left in figure 1. In this case, the object is detected by RADAR 2 and 3. Depending on exactly how the wind turbine site looks like, the processing means 220 determines that it may be sufficient to turn the warning lights on in wind turbine 3.

In yet another exemplary embodiment of the control unit 200 the processing means 220 is further configured to determine the on decisions based on if time to impact for objects in the RADAR information fall below a threshold. In this exemplary embodiment the processing means 220 determines the distance and speed for objects in the RADAR information and based on this information calculates the time it will take before the object collides with one or several wind turbines or an arbitrary closed surface enclosing one or several wind turbines in the site. If the time falls below a threshold the processing means 220 determines that one or several warning lights should be turned on.

In another exemplary embodiment of the control unit 200 the processing means 220 is further configured to determine the on decisions based on if the distance between objects in the RADAR information and one or several wind turbines or an arbitrary closed surface enclosing one or several wind turbines in the site fall below a threshold. In this exemplary embodiment the processing means 220 determines the distance for objects in the RADAR information and if the distance falls below a threshold the processing means 220 determines that one or several warning lights should be turned on.

In yet another exemplary embodiment of the control unit 200 the processing means 220 is further configured to determine said off decisions based on if objects in the RADAR information move away from the wind turbine site. In this exemplary embodiment the processing means 220 determines if the objects in the RADAR information moves away from the wind turbines site and if they do the processing means 220 determines that one or several warning lights should be turned off.

In another exemplary embodiment of the control unit 200 the processing means 220 is further configured to determine the off decisions based on if distances to the wind turbine site for objects in the RADAR information rise above a threshold. In this exemplary embodiment the processing means 220 determines the distance for objects in the RADAR information and if the distances rise above a threshold the processing means 220 determines that one or several warning lights should be turned off.

In a further exemplary embodiment of the control unit 200 the processing means 220 is further configured to determine intersection object volumes and their movement in the air territory for objects in the RADAR information and determining the on/off decisions bases on the object volumes position and movement in the air territory.

The intersection object volumes and their movement are determined by the processing means 220 from the RADAR information. The object volume is a sub volume of the total airspace where a detected object must be located with respect to the accuracy of the RADAR sensor. Each detected object of each RADAR has an associated object volume. If the control unit 200 receives RADAR information from several RADAR units each observing overlapping sub volumes of the air territory, the accuracy of the object position and their movement can be improved, since object volumes from several RADARs are used. In an exemplary embodiment of the control unit 200, where the control unit 200 receives RADAR information from several RADARs can the intersection object volume be calculated as the intersection of the object volume from each RADAR. The intersection object volume is a sub volume of the total object volumes from the different RADARs, where a detected object must be located with respect to the different object volumes. But the processing means 220 can determine the intersection object volumes in many different ways. Consider a case where the processing means 220 has determined that no warning lights should be turned on since there are no objects in the RADAR information received by the control unit 200. When the processing means 220 later determines that there are object in the air territory, the processing means 220 can use the object volumes and their movements. In a case where the objects volumes are small compared to a case where the object volume is larger the numbers of on decisions for the warning lights would be smaller since the processing means 220 more precisely can determine which warning lights that are required in order to warn the objects.

In a further exemplary embodiment of the control unit 200 each object volume and each intersection object volume is associated with a three dimensional velocity vector. In an exemplary embodiment may the velocity vector associated with the object volume point in a radial direction from the RADAR. The velocity vector associated with intersection object volume may point in an arbitrary direction. The velocity vectors follows directly from the Doppler shift of the received radar signal, but can also be obtained by comparing the position of the object at different times. The velocity vectors is used for the decision based on speed described previously. The information about the movements of the object can also be used to match the object data from one or several radars.

The control unit 200 further comprises control means 230 configured to turn on and/or off the warning lights according to the on and/or off decisions determined by the processing means 220. In an exemplary embodiment of the control unit 200 is the processing means 220 implemented as software which when run on a processor in the control unit 200 causes the control unit 200 to perform the functions according to previously described embodiments. In exemplary embodiments of the control unit 200 is the control means 230 part of the processing means 220. In this embodiment may the control means 230 also be implemented as software which when run on the processor in the control unit 200 causes the control unit 200 to perform the functions described above for the control unit 200. Referring to figure 3 there is illustrated a flowchart of a method in a control unit 200 for controlling one or several of warning lights in a wind turbine site, where the one or several of the warning lights, lights up an air territory of the wind turbine site, in accordance with previously described embodiments of the present invention. As shown in figure 3, the method comprises:

300 receiving RADAR, Radio Detection and Ranging, information from one or several RADAR units observing said air territory;

310 determining on and/or off decisions for one or several of the warning lights in the set based on objects positions and movements in the air territory from the RADAR information, wherein the on and/or off decisions are determined in order to minimize the number of on decision and maximize the number of off decision in order to minimize light pollution from the warning lights;

320 turning on and/or off said warning lights according to said on and/or off decisions.

As previously described, in an exemplary embodiment of the present invention, can in the step of receiving 300, RADAR information, be received from several RADAR units each observing different sub volumes of the air territory.

In another exemplary embodiment of the method according to the present invention, the step of determining further comprising determining the on decisions based on if time to impact for objects in the RADAR information fall below a threshold.

In yet another exemplary embodiment of the method according to the present invention, the step of determining further comprising determining the on decisions based on if distances to the wind turbine site for objects in the RADAR information fall below a threshold. Further, in another exemplary embodiment of the method according to the present invention, the step of determining further comprising determining the off decisions based on if objects in the RADAR information move away from the wind turbine site.

In another exemplary embodiment of the method according to the present invention, the step of determining further comprising determining the off decisions based on if distances to the wind turbine site for objects in the RADAR information rise above a threshold.

In another exemplary embodiment of the method according to the present invention, the step of determining further comprising determining object volumes and their movement in the air territory for objects from the RADAR information, and determining the on/off decisions bases on the object volumes position and movement in the air territory.

Yet further, in another exemplary embodiment of the method according to the present invention, the RADAR information comprises distance from the respective RADAR units to the object and speed for the objects.

The present invention also relates to a computer program, stored on a computer readable storage medium, which when run on the processing means 220 in the control unit 200 causes the control unit 200 to perform the method according to any of the previously described embodiments.

The detailed description is of the best mode presently contemplated for practicing the present invention. It is not intended to be taken in a limiting sense, but is made merely for the purpose of describing general principles. The scope of the invention is to be ascertained with reference to the issued claims.