Abstract:
A system and method is provided for ground testing of a yaw system of a nacelle ( 3 ) prior to erection of a wind turbine ( 1 ). A portable transformer box ( 10 ) is provided which will allow the nacelle preparation team to operate the yaw and hydraulic systems while the nacelle is grounded prior to erection.

Description:
FIELD OF THE INVENTION 
     The disclosure generally relates to wind turbines and, more particularly to ground testing of a yawing system of a wind turbine prior to erection. 
     BACKGROUND OF THE INVENTION 
     A wind turbine comprises several components including a tower, a nacelle, a generator, a rotor comprising a hub and rotor blades and so on. Yaw systems are conventionally used in wind power stations to yaw the turbine nacelle to the required angle against the wind. When a wind turbine is erected, the blades, the hub, the tower and the nacelle are transported to the site of erection. The tower is erected, the nacelle is mounted on the tower, the hub is mounted on the nacelle and the rotor blades are attached to the hub by means of at least one crane. When erected on land, normally mobile cranes are used to position, orient and arrange the components relatively to each other so that the components are able to be mounted together. During this erection phase in wind turbine construction, it is also necessary to yaw the nacelle while mounting the rotor and again, post lifting, to allow the crane to track unobstructed to the next site. As in any other physical systems, faults/failures may occur in the system. Specifically, if there are any failures with the yaw system during the erection phase, costly standstills of manpower and equipment will result. 
     In order to operate and test the yaw and hydraulic systems, specific voltages must be supplied to the nacelle. Unfortunately, yaw failures can only be detected after the nacelle is erected on the tower because the required voltages are not available on the ground. 
     Wind turbines, yaw controls, and testing systems are well known in the art, including those described in US Patent and Application Nos. 2009/0100918, 2009/0016227, 2008/0266400, 2008/0307647, 2009/0004009, 2009/0039651, 2009/0129931, each of which is incorporated herein by reference. 
     SUMMARY OF THE INVENTION 
     Systems and methods for ground testing yaw systems of wind turbines are provided. In this regard, an exemplary embodiment of system for ground testing yaw systems of wind turbines, a portable transformer box is provided which will allow the nacelle preparation team to operate the yaw and hydraulic systems while the nacelle is grounded prior to erection. 
     In a first embodiment, the invention is a system for ground testing a yaw system of a wind turbine, comprising: a portable transformer device comprising a step down transformer, a case for enclosing the step down transformer, a first input voltage connection for receiving a first input voltage from a generator, a second output voltage connection for providing a second output voltage equal to the first input voltage of the generator, and a third stepped down output voltage connection for providing a third stepped down output voltage, wherein the step down transformer converts the first input voltage of the generator to the third stepped down output voltage, wherein the second output voltage connection and the third stepped down output voltage connection are adapted to be connected to a nacelle of a wind turbine for providing the necessary power for testing the yaw system while the nacelle is grounded prior to erection. 
     In a further embodiment, the first input voltage is approximately 690 VAC, the second output voltage is approximately 690 VAC, and the third stepped down output voltage is approximately 400 VAC. The generator for provides 690 VAC. In a further embodiment, a controller is provided that has a communication link adapted for connection to the nacelle to control the yaw system. The case may include ventilation and one or more handles for transporting the portable transformer device. The yaw system has status lights that indicate the yaw system is operational. 
     In a second embodiment, the invention is a system for ground testing a yaw system of a wind turbine that also includes the controller. This embodiment has a portable transformer device comprising a step down transformer, a controller having a communication link adapted for connection to a nacelle of a wind turbine to control a yaw system, a case for enclosing the step down transformer and the controller, a first input voltage connection for receiving a first input voltage from a generator, a second output voltage connection for providing a second output voltage substantially equal to the first input voltage of the generator, and a third stepped down output voltage connection for providing a third stepped down output voltage, wherein the step down transformer converts the first input voltage of the generator to the third stepped down output voltage, wherein the second output voltage connection and the third stepped down output voltage connection are adapted to be connected to the nacelle of the wind turbine for providing the necessary power for testing the yaw system while the nacelle is grounded prior to erection. 
     The invention also includes a method for ground testing a yaw system of a wind turbine, comprising the following steps: (a) connecting a portable transformer device to a generator having a first output voltage provided by a first output voltage connection, wherein an input voltage connection of the portable transformer device is connected to the first output voltage connection of the generator, and wherein the portable transformer device provides a second output voltage by a second output voltage connection equal to the first output voltage of the generator and a third stepped down output voltage by a third stepped down output voltage connection; (b) connecting the second output voltage connection of the portable transformer device and the third stepped down output voltage connection to a nacelle of the wind turbine; (c) connecting a controller to the nacelle for controlling a yaw system of the nacelle; (d) powering on the generator to provide the first output voltage from the generator; (e) receiving by the portable transformer device the output voltage from the generator, providing the output voltage of the generator to the second output voltage connection and stepping down the output voltage from the generator to provide the third stepped down output voltage connection to the nacelle of the wind turbine; (f) energizing the yaw system, such that the yaw system receives the second output voltage and the third stepped down output voltage from the portable transformer device; and (g) outputting an indication to status lights of the yaw system to indicate that the yaw system is operational. 
     In an embodiment, the first input voltage is approximately 690 VAC, the second output voltage is approximately 690 VAC, and the third stepped down output voltage is approximately 400 VAC and the generator provides 690 VAC. The method may further include connecting an output signal that indicates that the yaw system is operational to a reporting device or an alarm device. The method may further include visually inspecting the status lights to confirm that the yaw system is operational, visually inspecting the nacelle for movement to confirm that the yaw system is operational, and/or receiving an indication of movement of the nacelle to confirm that the yaw system is operational. 
     Other systems, methods, features and/or advantages of this disclosure will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be within the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in the following description in view of the drawings that show: 
         FIG. 1  is a schematic drawing depicting a typical assembled wind turbine. 
         FIG. 2  is a schematic diagram depicting an exemplary embodiment of a system for ground testing a yaw system of a wind turbine. 
         FIG. 3  is a circuit diagram of the transformer of  FIG. 2 . 
         FIG. 4  is a schematic diagram depicting an exemplary embodiment of a system for ground testing a yaw system of a wind turbine of  FIG. 2  in use. 
         FIG. 5  is a schematic diagram depicting another exemplary embodiment of a system for ground testing a yaw system of a wind turbine. 
         FIG. 6  is a circuit diagram of the transformer of  FIG. 5 . 
         FIG. 7  is a schematic diagram depicting an exemplary embodiment of a system for ground testing a yaw system of a wind turbine of  FIG. 5  in use. 
         FIG. 8  is a flow diagram illustrating the steps of the testing method of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Systems and methods for testing a yaw system of a wind turbine are provided, several exemplary embodiments of which will be described in detail. In a conventional manner, as shown in  FIG. 1 , an assembled wind turbine  1  comprises a tower  2 , a nacelle  3  and a rotor including a hub  4  with rotor blades  5 . The nacelle  3  is rotatably mounted on the tower  2  around a yawing axle (not shown). A yaw control motor (not shown) is located between the tower  2  and the nacelle  3  to yaw the nacelle. 
     Referring now in more detail to the drawings,  FIG. 2  is a schematic diagram illustrating an exemplary embodiment of a system for ground testing a yaw system of a wind turbine. As shown in  FIG. 2 , the system comprises a portable transformer device  10  having a case  12 , input voltage connection  14  (e.g., 690 VAC), output voltage connection  16  (e.g., 690 VAC), and stepped down output voltage connection  18  (e.g., 400 VAC). 
     Turning now to  FIG. 3 , an illustration of the transformer circuitry in an exemplary embodiment is shown, having input voltage connection  14  (e.g., 690 VAC/IN), output voltage connection  16  (e.g., 690 VAC/OUT), and stepped down output voltage connection  18  (e.g., 400 VAC/OUT). Stepdown transformer  20  steps down the input voltage from input voltage connection  14  to stepped down output voltage at output voltage connection  18 . 
       FIG. 4  is a schematic diagram depicting an exemplary embodiment of a system for ground testing a yaw system of a wind turbine of  FIG. 2  in use. During the yawing process the turbine nacelle  3  is turned around a vertical axis until the rotor axis is, except for a possible vertical tilt angle, parallel to the wind direction. Usually the yaw axis is concentric with the wind turbine tower axis. Yawing is normally carried out by electrical or hydraulic means. The yaw drive unit control is based on a measurement of the wind direction by one or more wind direction sensors placed on the turbine nacelle. A generator  30  (usually 690 VAC trailer) may be on site to supply 690 VAC. It may also supply 110 VAC output voltage  15  for controller devices  32  which control communication through communication link  34  with the nacelle  3 . However, the necessary 400 VAC is not provided by the generator  30 . The portable transformer device  10  receives input voltage  14  from generator  30 . It provides output voltage 690 VAC to the nacelle  3  from connection  16  (e.g., 690 VAC/OUT), and stepped down output voltage 400 VAC to the nacelle  3  from connection  18  (e.g., 400 VAC/OUT). With this portable transformer device  10 , all the necessary voltage is now available on the ground for operation/ground testing of the yaw and hydraulic systems while the nacelle  3  is grounded. 
     Although while on the ground, the nacelle  3  would not necessarily be physically yawed due to the restraints of the nacelle stand, the ground test will provide the ability to visually check the yaw system status lights upon energizing. The portable transformer device  10  also allows verification that the crane is operational. 
       FIG. 5  is a schematic diagram depicting another exemplary embodiment of a system for ground testing a yaw system of a wind turbine. As shown in  FIG. 5 , the system comprises a portable transformer device  10  having a case  12 , input voltage connection  14  (e.g., 690 VAC), input voltage connection  15  (e.g., 110 VAC), output voltage connection  16  (e.g., 690 VAC), and stepped down output voltage connection  18  (e.g., 400 VAC), and communication link  34  (COM/OUT) from an internal controller (not shown). The case  12  preferably include ventilation  40 , a handle for carrying the device  42 , and input controls  44  for the yaw controller. The case may further include a locking mechanism (not shown) and any necessary warning labels and the like. Outputs that indicate the yaw is operational may be provided for connection to further devices such as an alarm, a computer, a reporting tool, and the like. 
       FIG. 6  is a circuit diagram of the transformer of  FIG. 5 , having input voltage connection  14  (e.g., 690 VAC/IN), input voltage connection  15  (e.g., 110 VAC/IN), output voltage connection  16  (e.g., 690 VAC/OUT), and stepped down output voltage connection  18  (e.g., 400 VAC/OUT). Stepdown transformer  20  steps down the input voltage from input voltage connection  14  to stepped down output voltage at output voltage connection  18 . A controller  32  is provided in the device  10  which receives 110 VAC and provides the communication link  34  (COM/OUT). 
       FIG. 7  is a schematic diagram depicting an exemplary embodiment of a system for ground testing a yaw system of a wind turbine of  FIG. 4  in use. A generator  30  (usually 690 VAC trailer) may be on site to supply 690 VAC. It may also supply 110 VAC output voltage  15  for controller devices  32  which control communication through communication link  34  with the nacelle  3 . However, the necessary 400 VAC is not provided by the generator  30 . The portable transformer device  10  receives input voltage  14  from generator  30 . It provides output voltage 690 VAC to the nacelle  3  from connection  16  (e.g., 690 VAC/OUT), and stepped down output voltage 400 VAC to the nacelle  3  from connection  18  (e.g., 400 VAC/OUT). A controller  32  is provided in the device  10  which receives 110 VAC and provides the communication link  34  (COM/OUT). With this portable transformer device  10 , all the necessary voltage is now available on the ground for operation/ground testing of the yaw and hydraulic systems while the nacelle  3  is grounded. 
     With reference to  FIG. 8 , a ground testing method for a yaw system of a wind turbine  1  according to an embodiment of the invention is shown. In this embodiment, the yaw system is used in a wind turbine system  1 . The testing method includes the following steps  100  to  140 . 
     The nacelle prep team provides a generator trailer with 690 VAC. The portable transformer device  10  is connected to the generator  30  and the nacelle  3  in step  100 . A controller  32  is provided separate from or as part of the device  10  which receives 110 VAC and provides the communication link  34  (COM/OUT) for the nacelle  3  in step  102 . The generator is powered on and the portable transformer device  10  receives input voltage  14  from generator  30 . It provides output voltage 690 VAC to the nacelle  3  from connection  16  (e.g., 690 VAC/OUT), and stepped down output voltage 400 VAC to the nacelle  3  from connection  18  (e.g., 400 VAC/OUT) in step  104 . With this portable transformer device  10 , all the necessary voltage is now available on the ground for operation/ground testing of the yaw and hydraulic systems while the nacelle  3  is grounded. Upon energizing in step  106 , the yaw system can be tested by a visual inspection of the status lights in step  108 . The nacelle attempting to yaw with slight movement may also be observed in step  108 . This is sufficient to confirm operation of the device before erection. 
     While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.