# US 8,487,464 B2 · Blade pitch control in a wind turbine installation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,487,464 B2 - Document ID: US8487464B2 - Status: Granted - Kind: B2 - Application number: 13/131,620 - Filed: 2009-12-23 - Published: 2011-12-29 - Granted: 2013-07-16 - Earliest claimed: 2008-12-30 - Assignees: Hywind AS - Applicants: Bjorn Skaare; Finn Gunnar Nielsen - Inventors: Bjorn Skaare; Finn Gunnar Nielsen - Web page: https://patentgrep.com/patent/US8487464B2 ## CPC - F03D 7/0276: {controlling rotor speed, e.g. variable speed} - F03D 7/0224: {Adjusting blade pitch} - F03D 7/0296: {to prevent, counteract or reduce noise emissions} - F03D 7/043: {characterised by the type of control logic} - F03D 13/25: specially adapted for offshore installation - F05B 2240/93: on a structure floating on a liquid surface - F05B 2260/96: Preventing, counteracting or reducing vibration or noise - F05B 2270/101: to control rotational speed (n) - F05B 2270/304: Spool rotational speed - F05B 2270/327: Rotor or generator speeds - Y02E 10/72: Wind turbines with rotation axis in wind direction - Y02E 10/727: Offshore wind turbines - F03D: WIND MOTORS - F05B: INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract The present invention relates to a blade pitch controller for a floating wind turbine structure, wherein the floating wind turbine structure may include a support structure supporting a rotor having a number of blades. The controller may include standard blade pitch control means and active damping means. The standard blade pitch control means is arranged to control a blade pitch using a transfer function between a rotor speed error and the blade pitch. The active damping means is arranged to further control the blade pitch on the basis of a speed of a point on the wind turbine structure by converting the speed of a point on the wind turbine structure into a rotor speed error and using the same transfer function that is used in the standard blade pitch control means to convert the rotor speed error into a correction to the blade pitch. ## Claims ### Claim 1 A blade pitch controller for a floating wind turbine structure comprising a support structure supporting a rotor having a plurality of blades, the controller comprising: standard blade pitch control means; and active damping means; wherein the standard blade pitch control means is arranged to control a blade pitch using a transfer function between a rotor speed error and the blade pitch; and the active damping means is arranged to further control the blade pitch on the basis of a speed of a point on the wind turbine structure by converting the speed of a point on the wind turbine structure into a rotor speed error and using the same transfer function that is used in the standard blade pitch control means to convert the rotor speed error into a correction to the blade pitch. ### Claim 2 (depends on 1) A blade pitch controller as claimed in claim 1, wherein controller parameters can be changed by remote operation. ### Claim 3 (depends on 1) A blade pitch controller as claimed in claim 1, wherein the active damping means comprises a low pass filter. ### Claim 4 (depends on 3) A blade pitch controller as claimed in claim 3, wherein the low pass filter is arranged to filter out changes in the speed of a point on the wind turbine structure with frequencies above the natural frequency of the rigid body oscillations of the wind turbine structure in pitch. ### Claim 5 (depends on 3) A blade pitch controller as claimed in claim 3, wherein the low pass filter is arranged to filter out changes in the speed of a point on the wind turbine structure with frequencies above 0.05 Hz. ### Claim 6 (depends on 3) A blade pitch controller as claimed in claim 3, wherein the low pass filter is arranged to filter out changes in the speed of a point on the wind turbine structure with frequencies above 0.04 Hz. ### Claim 7 (depends on 3) A blade pitch controller as claimed in claim 3, wherein the low pass filter is a sharp filter. ### Claim 8 (depends on 3) A blade pitch controller as claimed in claim 3, wherein the low pass filter is a second or third order Butterworth low pass filter. ### Claim 9 (depends on 1) A blade pitch controller as claimed in claim 1, wherein the active damping means comprises active damping gain means which converts the speed of a point on the wind turbine structure into a rotor speed error. ### Claim 10 (depends on 9) A blade pitch controller as claimed in claim 9, wherein the active damping gain means is arranged to reduce or prevent negative damping of rigid body oscillations of the wind turbine structure in pitch. ### Claim 11 (depends on 9) A blade pitch controller as claimed in claim 9, wherein the active damping gain means is arranged to provide net positive damping of rigid body oscillations of the wind turbine structure in pitch. ### Claim 12 (depends on 1) A blade pitch controller as claimed in claim 1, wherein the transfer function that is used in both the active damping means and the standard blade pitch control means is implemented in the form of a proportional integral controller. ### Claim 13 (depends on 11) A blade pitch controller as claimed in claim 11, wherein the controller comprises two proportional integral controllers, one in the active damping means and one in the standard blade pitch control means. ### Claim 14 (depends on 12) A blade pitch controller as claimed in claim 12, wherein the controller comprises a proportional integral controller that is arranged to be used by both the active damping means and the standard blade pitch control means. ### Claim 15 (depends on 1) A blade pitch controller as claimed in claim 1, wherein the blade pitch can be adjusted separately for each rotor blade. ### Claim 16 A method of controlling the blade pitch of a floating wind turbine structure comprising a support structure supporting a rotor having a plurality of blades, the method comprising: adjusting a blade pitch on the basis of the output of a transfer function between a rotor speed error and the blade pitch; and further adjusting the blade pitch on the basis of a horizontal speed of a point on the wind turbine structure; wherein the speed of a point on the wind turbine structure is converted into a rotor speed error which is then converted into a blade pitch using the same transfer function. ### Claim 17 (depends on 16) A method as claimed in claim 16, wherein the blade pitch is only further adjusted for changes in the speed of a point on the wind turbine structure with frequencies above a certain value. ### Claim 18 (depends on 17) A method as claimed in claim 17, wherein the certain value is above the natural frequency of the rigid body oscillations of the structure in pitch. ### Claim 19 (depends on 17) A method as claimed in claim 17, wherein the certain value is 0.05 Hz. ### Claim 20 (depends on 17) A method as claimed in claim 17, wherein the certain value is 0.04 Hz. ### Claim 21 (depends on 17) A method as claimed in claim 17, wherein the changes in the speed of a point on the wind turbine structure are filtered using a low pass filter. ### Claim 22 (depends on 21) A method as claimed claim 21, wherein the low pass filter is a second or third order Butterworth low pass filter. ### Claim 23 (depends on 16) A method as claimed in claim 16, wherein the speed of a point on the structure is converted into a rotor speed error using an active damping gain means. ### Claim 24 (depends on 23) A method as claimed in claim 23, wherein the active damping gain means is arranged to reduce or prevent negative damping of rigid body oscillations of the wind turbine structure in pitch. ### Claim 25 (depends on 23) A method as claimed in claim 23, wherein the active damping gain means is arranged to net provide positive damping of rigid body oscillations of the wind turbine structure in pitch. ### Claim 26 (depends on 16) A method as claimed in claim 16, wherein the transfer function that is used in both the active damping means and the standard blade pitch control means is implemented in the form of a proportional integral controller. ### Claim 27 (depends on 1, 16) A floating wind turbine installation comprising a blade pitch controller as claimed in claim 1 or controlled according to claim 16.