Electro-hydraulic actuator for controlling the pitch of a blade of a wind turbine

Abstract

The present invention provides an improvement for use in a wind turbine ( 20 ) having a plurality of variable-pitch blades ( 24 ) mounted on a hub ( 23 ) for rotation relative to a nacelle ( 22 ). The improvement broadly includes: a electro-hydraulic actuator ( 25 ) for controlling the pitch of one of the blades, the actuator including: a motor ( 26 ) adapted to be supplied with a current; a pump ( 27 ) driven by the motor and arranged to provide a hydraulic output as a function of the current supplied to the motor; and a hydraulic actuator ( 28 ) operatively arranged to selectively vary the pitch of the associated blade as a function of the hydraulic output of the pump; and wherein the motor, pump and actuator are physically arranged within the hub of the wind turbine.

1 . In a wind turbine having a plurality of variable-pitch blades mounted on a hub for rotation relative to a nacelle, the improvement comprising:
 a electro-hydraulic actuator for controlling the pitch of one of said blades, said actuator including:   a motor adapted to be supplied with a current;   a pump driven by said motor and arranged to provide a hydraulic output as a function of the current supplied to said motor; and   a hydraulic actuator operatively arranged to selectively vary the pitch of the associated blade as a function of the hydraulic output of said pump; and   wherein said motor, pump and actuator are physically arranged within the hub of said wind turbine.   
     
     
         2 . The improvement as set forth in  claim 1  wherein said wind turbine has three of said variable-pitch blades mounted on said hub, and wherein one of said electro-hydraulic actuators is provided for each of said blades. 
     
     
         3 . The improvement as set forth in  claim 1  wherein said motor is a d.c. brushless motor. 
     
     
         4 . The improvement as set forth in  claim 1  wherein said pump is a fixed displacement pump. 
     
     
         5 . The improvement as set forth in  claim 1  wherein the polarity of the hydraulic output from said pump is a function of the polarity of the current supplied to said motor. 
     
     
         6 . The improvement as set forth in  claim 1  wherein said actuator has a piston slidably mounted within a cylinder and sealingly separating a first chamber on one side of said piston from a second chamber on the other side of said piston, and wherein a rod is mounted on said piston and extends through one of said chambers and penetrates and end wall of said cylinder such that said piston has unequal-area surfaces facing into said chambers. 
     
     
         7 . The improvement as set forth in  claim 6  and further comprising a hydraulic reservoir and an anti-cavitation valve operatively arranged between said tank and said actuator such that hydraulic fluid will flow from said reservoir to the chamber facing said larger-area piston face when such chamber is expanding, and will flow to said reservoir from the chamber facing said larger-area piston face when such chamber is contracting. 
     
     
         8 . The improvement as set forth in  claim 7  wherein said hydraulic reservoir is pressurized. 
     
     
         9 . The improvement as set forth in  claim 7  wherein said anti-cavitation valve operates automatically as a function of the polarity of the hydraulic output of said pump. 
     
     
         10 . The improvement as set forth in  claim 1  and further comprising a pressure relief valve operatively arranged to limit the maximum pressure of said pump hydraulic output. 
     
     
         11 . The improvement as set forth in  claim 7  wherein said pump has a high-pressure side and a low-pressure side, and a case drain. 
     
     
         12 . The improvement as set forth in  claim 1 , and further comprising a bypass valve positioned selectively operable to communicate said high- and low-pressure sides. 
     
     
         13 . The improvement as set forth in  claim 11 , wherein said case drain communicates with said reservoir through a filter. 
     
     
         14 . The improvement as set forth in  claim 11 , and further comprising a restricted orifice in series with said bypass valve. 
     
     
         15 . The improvement as set forth in  claim 1 , and further comprising:
 a source of pressurized hydraulic fluid communicating via a conduit with the chamber into which said small-area piston surface faces, and   a normally-open solenoid valve arranged in said conduit, and   wherein said solenoid valve is arranged to be opened in the event of a power failure to permit hydraulic fluid to flow from said source through said conduit and into the chamber into which said small-area piston surface faces to cause such chamber to expand and to urge said piston to move toward a position relative to said cylinder at which said blade is feathered.   
     
     
         16 . The improvement as set forth in  claim 15  and further comprising blocking valves operatively arranged to selectively isolate said pump from said small- and large-area actuator chambers. 
     
     
         17 . The improvement as set forth in  claim 1  wherein power from said nacelle is provided to said motor through a contactless rotary transformer. 
     
     
         18 . The improvement as set forth in  claim 1  and further comprising a motor controller and a power stage, and wherein said motor controller and said power stage are also physically arranged within the hub of said turbine. 
     
     
         19 . The improvement as set forth in  claim 18  wherein said motor controller and said power stage are mounted on said electro-hydraulic actuator.