Patent Publication Number: US-2010109334-A1

Title: Wind turbine fluid filtering system

Description:
FIELD OF THE INVENTION 
     The present disclosure relates generally to wind power fluid systems, and more particularly to a method and system for removing fluid contamination in fluid systems of wind plants. 
     BACKGROUND 
     Recently, wind turbines have received increased attention as an environmentally safe and relatively inexpensive alternative energy source. With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient. 
     Generally, a wind turbine includes a plurality of blades coupled to a rotor through a hub. The rotor is mounted within a housing or nacelle, which is positioned on top of a tubular tower or base. Utility grade wind turbines (i.e. wind turbines designed to provide electrical power to a utility grid) can have large rotors (e.g., thirty or more meters in diameter). Blades on these rotors transform wind energy into a rotational torque or force that drives the rotor. The rotor is rotationally coupled to one or more generators or hydraulic systems, which are components in the main power conversion system that converts the mechanical energy into electricity. In the case where the wind turbine uses hydraulic systems for power conversion, the hydraulic system includes oil circuits for driving motors and auxiliary equipment. The wind turbine may also include additional systems such as a gearbox, main bearing, auxiliary power conversion and brake systems that may also include oil circuits for lubrication and cooling. 
     Wind turbine oil circuits have used filters to remove contaminants such as dirt and particles from the oil. These filters require replacement after determined periods of use in order for the filters to remain effective and also to prevent increased oil circuit pressure from filters as they trap particles. Additionally, the filter media and screens of these filters degrade over use and often require circuits to be shut down for maintenance and/or replacement. 
     Therefore, what is needed is a method and system for filtering fluids, such as oil in the oil circuits of a wind plant that reduces maintenance and operational costs. 
     SUMMARY 
     The object of the present disclosure is to provide a wind turbine backflushing system that permits fluid systems in a wind turbine power generation system to operate within a predetermined pressure drop range. 
     According to a first embodiment of the disclosure, a wind turbine power generation system is disclosed that includes a backflushing filter system. 
     According to a second embodiment of the disclosure, a method of cleaning a fluid of a wind turbine power generation system is disclosed that includes circulating a fluid through a backflushing filter system of an oil circuit of the wind turbine power generation system. 
     Further aspects of the method and system are disclosed herein. The features as discussed above, as well as other features and advantages of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side view of an exemplary wind turbine. 
         FIG. 2  is a schematic illustration of an exemplary embodiment of a wind turbine power generation system according to the disclosure. 
         FIG. 3  is a schematic illustration of an exemplary embodiment of the pumping subsystem shown in  FIG. 2 . 
         FIG. 4  is an illustration of an exemplary backflushing filter system according to the disclosure. 
     
    
    
     Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     DETAILED DESCRIPTION 
     The present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which a preferred embodiment of the disclosure is shown. This disclosure 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 disclosure to those skilled in the art. 
       FIG. 1  shows an exemplary wind turbine  100  according to the disclosure. The wind turbine  100  includes a nacelle  102  mounted atop a tower  104  and a rotor  106 . The nacelle  102  houses a wind turbine power generation system  105  ( FIG. 2 ) for converting wind energy captured by the rotor  106  to electricity. The nacelle  102  may further house other equipment for controlling and operating the wind turbine  100 . The rotor  106  includes rotor blades  108  attached to a rotating hub  110 . The rotating hub  110  is connected to the wind turbine power generation system  105  and configured to provide mechanical energy thereto. In this exemplary embodiment, the wind turbine  100  includes three rotor blades  108 . In another embodiment, the wind turbine may contain one or more rotor blades  108 . The height of the tower  104  is selected on the basis of factors and conditions known in the art, and may extend to heights up to 60 meters or more. The wind turbine  100  may be installed on any terrain providing access to areas having desirable wind conditions. The terrain may vary greatly and may include, but is not limited to, mountainous terrain or offshore locations. 
     In some configurations and referring to  FIG. 2 , an exemplary schematic configuration of the wind turbine power generation system  105  is disclosed. The wind power generation system  105  is housed in nacelle  102  ( FIG. 1 ). As can be seen in  FIG. 2 , the rotor  106  is coupled by a shaft  112  to a hydraulic pumping system  120 . The rotation of the rotor  106  rotationally drives shaft  112  to provide mechanical energy to hydraulic pumping system  120  to circulate high pressure hydraulic fluid within the hydraulic pumping system  120 . The hydraulic pumping system  120  is coupled to a motor  136  via a hydraulic fluid circulation system  125 . The motor  136  converts energy from the circulating high pressure fluid into mechanical energy. The motor  136  may be any hydraulic motor suitable for this purpose that is known in the art. The motor  136  is coupled by a transfer device  138  to a generator  140 . The generator  140  converts the mechanical energy into electricity. The generator  140  provides the generated electricity to a power grid  150  via a transmission line  142 . In another embodiment, the motor  136  and generator  140  may be combined in a single device. In yet another embodiment, the pumping system  120  and the motor  136  may each consist of one or several independent pumping systems  120  or motors  136 , respectively. 
       FIG. 3  shows an exemplary schematic arrangement of the hydraulic pumping system  120  within the wind turbine power generation system  105  of  FIG. 2 . As can be seen in  FIG. 3 , the hydraulic pumping system  120  includes a pumping subsystem  160 . The pumping subsystem  160  includes a hydraulic pump (not shown) that is driven by shaft  112 . The pump provides a high pressure fluid to motor  135  via a high pressure fluid line  121  that is in fluid communication between the pumping subsystem  160  and the motor  135 . The high pressure fluid line  121  is in fluid communication with a high pressure reservoir  138 . At the motor  136 , some energy is removed from the high pressure fluid and a low pressure fluid is returned to the pumping subsystem  160  via a low pressure fluid line  122  that is fluid communication therebetween. The low pressure fluid line  122  is in fluid communication with a low pressure reservoir  134 . 
     The hydraulic pumping system  120  further includes a secondary subsystem  142  in fluid communication between the high pressure fluid line  121  and the low pressure fluid line  122 , a pressure release line  123  in fluid communication between the high pressure fluid line  121  and the low pressure fluid line  122 , and a low pressure fluid bypass line  124  in fluid communication bypassing the low pressure reservoir  134 . 
     The secondary subsystem  142  performs one or more secondary functions. Secondary functions refers to functions served by the high-pressure flow of operating fluid that are indirectly related to the generation of electricity, i.e., functions that do not require the flow of such fluid to the generator  140 . For example, the high-pressure flow of operating fluid in the secondary subsystem  142  can be used to lubricate bearings and/or the shaft  112 . In this exemplary embodiment, the hydraulic pumping system  120  includes one secondary subsystem  142 , however, in another embodiment, the hydraulic pumping system  120  may include one or more secondary subsystems  142 . In yet another embodiment, the hydraulic pumping system  120  may have he secondary subsystem  142  omitted. 
     The pressure release line  123  includes a first flow control device  146  to adjust the flow of high pressure fluid from the pumping subsystem  160  among the high pressure reservoir  138  and the secondary subsystem  142  by controlling the flow through pressure release line  123 . The flow control device  146  may additionally control and/or release fluid pressure between the high pressure fluid line  121  and the low pressure fluid line  122 . Additionally, the first flow-control device  144  is able to control flow from the pumping subsystem  160  within the predetermined operation parameters and/or thresholds, which can vary depending on the application. The hydraulic pumping system  120  may include other flow-control devices and sensors (not shown) to control flow within the hydraulic pumping system  120 . For example, a second flow control device (not shown) may control flow from the high-pressure reservoir  138  to the motor  136 . The first flow control device  146 , as well as the other flow-control devices, may be valves (e.g., check valves) or other devices known in the art to be suitable for such purposes. 
     The hydraulic pumping system  120  also includes one or more backflushing filter systems  200  in fluid communication with the low pressure fluid line  127 . The backflushing filter systems provide filtration to hydraulically driven auxiliary power consumers such as, but not limited to pitch, yaw and fan drive hydraulic systems. As can be seen in  FIG. 3 , in this exemplary embodiment, the hydraulic pumping system  120  includes five backflushing filter systems  200  disposed at various possible positions throughout the low pressure fluid line  122 . 
       FIG. 4  illustrates an exemplary arrangement of a backflushing filter system  200  according to the disclosure. As can be seen in  FIG. 4 , the backflushing filter system  200  includes a backflushing filter  210 , a containing filter  230 , a lubricated device  240 , a low pressure reservoir  250 , and a pump  260 . The backflushing filter  210  is in fluid communication with lubricated device  240  via a clean oil supply line  227 . Used oil is returned to the backflushing filter via an oil return line  228 . The low pressure reservoir and pump  260  are in fluid communication between the lubricated device  240  and the backflushing filter  240 . A backflushing return line  220  is in fluid communication between the backflushing filter  210  and the containing filter  210 . The containing filter  230  may be powered by a electrical power system, a hydraulic power system, or both. An optional fluid power supply line  229  is in fluid communication between the oil return line  228  and the containing filter  230 . The optional fluid power supply line  229  provides additional power to the containing filter  230  to perform the filtering function. The backflushing filter system  200  may be a backflushing filter system as disclosed in U.S. Pat. No. 5,906,733, which is incorporated herein by reference in its entirety. 
     The backflushing filter  210  may be selected from any backflushing filter as provided for by the fluid and particle size limitations of the particular application. The backflushing filter  210  may be a backflushing filter as disclosed in U.S. Pat. No. 6,890,434, which is incorporated herein by reference in its entirety. The backflushing filter  210  is disposed in the hydraulic flow line to filter particulate contamination from the hydraulic fluid. Backflushing filters are able to filter the total fluid flow always using 100% of the filter mesh contained within the backflushing filter  210 , whereas traditional filters need to be chosen for capacity on an almost-clogged condition so as not to create a high pressure drop in the low pressure line. 
     The circulation system  220  and containing filter  230  are arranged and configured to permit the backflushing filter  210  to be backflushed to remove particulate contamination that has been entrained in the backflushing filter  210 . By backflushing the backflushing filter  210 , mesh or other particulate entrapment structure or material of the backflushing filter may be cleaned so that the backflushing filter  210  may perform within a predetermined pressure drop over the lifetime of the backflushing filter  210 . 
     The containing filter  230  may be a centrifugal filter or other filter selected to entrain particulate contamination of a predetermined particle size range for a fluid for a particular application. For example, the circulation system  220  and containing filter  230  may be selected from the liquid cleaning system as disclosed in U.S. Pat. No. 5,906,733. 
     The wind turbine power generation system  105  may include additional backflushing filter systems  200  in fluid communication with the gearbox, mainbearing, brake oil circuits and/or any other auxiliary systems. Any of the backflushing filter systems  200  of the wind turbine power generation system  105  may commonly use circulation system  200  and containing filter  230  components. In one embodiment, one backflushing filter  210  may be disposed in the gearbox oil circuit, a second backflushing filter  210  may be disposed in the mainbearing oil circuit, and a single containing filter  230  is used to backflush both backflushing filters  210 . 
     The wind turbine power generation system  105  further includes valves, controls, and fluid systems to operate the backflushing filter systems  200 . In one embodiment, the backflushing filter system  200  includes controls to automate the scheduled backflushing of the backflushing filters  210  as determined by a predetermined schedule. In another embodiment, the backflushing process is a continuous process within a backflushing filtering system in the sense that there is a continuous routine of backflushing parts of the filtering system in a sequence. 
       FIG. 5  shows an exemplary configuration of a lubricating system  500  circulating a lubricating fluid in fluid communication at least one component of a drivetrain system  510 . The drivetrain system  510  includes a transmission  510  driven by a shaft  520  that is supported by a first bearing  530 , a second bearing  540  and a third bearing  550 . The shaft  520  is driven by a rotor  106  ( FIG. 2 ). The second bearing  540  and/or the third bearing  550  may optionally be integrated into the transmission  510 . Transmission  510  may be a gearbox. In this exemplary embodiment, the first bearing  530  and at least on of the second bearing  540 , third bearing  550  and transmission  510  are in fluid communication with lubricating system  500 . 
     As further shown in  FIG. 5 , the lubricating system  500  includes a backflusing filter system  200 . The backflushing filter system  200  includes a backflusing filter  210 , a containing filter  230  and a pump  260 . The backflushing filter  210  provides a part of the lubricating fluid to containing filter  230 . The containing filter  230  collects contamination such as, but not limited to dirt and metal particulates, from the lubricating fluid. The containing filter  230  may be a centrifugal filter. The rotation in the centrifugal filter may partially driven by lubricating fluid from the backflushing fluid line  220  and partially by a fluid stream (not shown) tapped from upstream the backflushing filter. 
     While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.