Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03D—WIND MOTORS
  • F03D80/00—Details, components or accessories not provided for in groups F03D1/00 - F03D17/00
  • F03D80/50—Maintenance or repair
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03D—WIND MOTORS
  • F03D15/00—Transmission of mechanical power
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03D—WIND MOTORS
  • F03D17/00—Monitoring or testing of wind motors, e.g. diagnostics
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03D—WIND MOTORS
  • F03D15/00—Transmission of mechanical power
  • F03D15/10—Transmission of mechanical power using gearing not limited to rotary motion, e.g. with oscillating or reciprocating members
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • 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
  • F05B2270/00—Control
  • F05B2270/10—Purpose of the control system
  • F05B2270/109—Purpose of the control system to prolong engine life
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • 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
  • F05B2270/00—Control
  • F05B2270/30—Control parameters, e.g. input parameters
  • F05B2270/332—Maximum loads or fatigue criteria
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/70—Wind energy
  • Y02E10/72—Wind turbines with rotation axis in wind direction

Definitions

• the present invention relates to a method for determining the evolution of torque of at least one rotatable shaft and the resulting fatigue damage to different power train components.
• the invention is particularly useful for design and/or maintenance operations in wind turbines having a power train that includes a high speed shaft and a low speed shaft.
• a power train that includes a high speed shaft and a low speed shaft.
• said high and low speed shafts rotate at different speeds which are related by a speed ratio.
• a wind turbine power train has to transmit an input torque at a speed from a low speed shaft (associated with rotor and blades) to a high speed shaft (associated with a generator that converts said input torque at a given speed into electric power).
• the invention makes it possible to precisely assess torque oscillations in the low speed shaft of the wind turbine rotor. Having this low speed shaft torque value together with the fatigue behaviour of the material of the component being analyzed, as well as the annual wind speed distribution, then the fatigue damage can be accurately known and consequently service lifetime of the wind turbine.
• an operating control and data log system may provide accurate values concerning electric power in the generator and angular velocity in the generator (i.e. the high speed shaft).
• input torque values in the rotor (low speed shaft) and angular velocity values in said low speed shaft are difficult to be accurately obtained. Due to this lack of input torque values at the low speed shaft, it is not possible at present to directly and readily obtain the values for the torque to which the wind turbine power train is subjected.
• Low speed shaft torque values are typically obtained by experimental methods in combination with mechanical measurements through strain gauge means by directly measuring stress values at the low speed shaft. This is capital intensive, specially taking into consideration the fact that this has to be done for each power train.
• the present invention provides a method through which the fatigue damage due to torque oscillations in the wind turbine power train can be accurately estimated from the electric torque and the angular velocity at the wind turbine generator.
• the method of the invention provides a possibility of knowing at all times the state of the parts in the power train of the wind turbine.
• the method of the invention makes therefore possible to determine for each wind turbine whether it is necessary to replace some parts when design fatigue limit has been exceeded so that it is possible to carry out suitable operations of maintenance.
• the method of the invention further permits design hypotheses to be validated referred to produced fatigue loads through software simulation and which have been taken into account in the design of the parts.
• This validation is usually carried out by means of a series of measurements in a prototype machine.
• the method according to the invention will permit to such validation to be carried out from available values causing fatigue.
• the present invention provides a method for determining the evolution of torque of at least one rotatable shaft and the resulting fatigue damage to different power train components for design and/or maintenance operations in a wind turbine.
• the invention makes it possible to know the evolution of the fatigue in a power train of a single wind turbine or a complete wind farm, with the power train comprising a high speed shaft and a low speed shaft.
• the method of the invention comprises the steps of determining torque, moment of inertia and angular acceleration at the high speed shaft of the wind turbine. These determinations are carried out by directly measuring such values at the generator. For determining the angular acceleration at the high speed shaft a time-derivative of the angular velocity at the high speed shaft may be used.
• the method of the invention further includes the step of determining torque at the low speed shaft of the wind turbine by multiplying the speed ratio of the speeds at the respective shafts by the result of subtracting the torque at the high speed shaft from the product of moment of inertia by the angular acceleration at the high speed shaft.
• a rainflow-counting algorithm procedure For determining torque value variations at the low speed shaft of the wind turbine power train a rainflow-counting algorithm procedure may be applied. This step of applying a rainflow-counting algorithm to the value of the torque at the low speed shaft may be performed at least for one torque mean value.
• the result of this rainflow-counting procedure would be a data matrix including number of cycles for every torque range at every torque mean value. This makes possible to store service measurements in a form suitable for a fatigue analysis of the components in a wind turbine, e.g. fatigue life prediction and simulation testing.
• the method may comprise a further step of determining the relationship between the torque and the stress in the material at every point of every component to be analysed. This relationship may be given by a factor or a non linear equation applied to the torque value to obtain cycles at stress ranges for every mean stress value.
• said further step may be carried out relative to strain values instead of stress values so that the equation giving the relationship between the torque and the strain in the material at every point of every component to be analysed can be determined.
• the equation is linear it can be simply a factor.
• the relationship between torque and strain is determined by analytical calculation or by FEM.
• Torque value variations can be then transformed into stress or strain variations by applying the corresponding equation to the torque values, i.e. a stress range - mean stress value matrix or strain range - mean strain value matrix is made available for every component analysis point.
• the method may also comprise a further step consisting in determining the accumulated fatigue damage during a period of time in any of the parts of the power train by comparing the number of cycles performed with a predetermined limit established by an SN (stress/number of cycles) curve for each stress range.
• SN stress/number of cycles
• the method can be carried out using strain values.
• number of cycles performed would be compared with a predetermined limit established by an ⁇ N (strain/number of cycles) curve for each strain range.
• This can be preferably carried out by applying the Miner's rule for assessing the fatigue life of the wind turbine subject to complex loading. This rule is applied by comparing for each stress or strain range the number of cycles undergone by the system with the limit established by an SN/ ⁇ N curve.
• the SN curves can be defined by different methods (Leitfaden, FKM or SWL99).
• SN and ⁇ N curves can be obtained by experimental methods. In any case, the curve will be varied according the average stress/strain.
• the average stress or strain value is obtained from the above defined matrix.
• Fig.1 is a diagrammatic view of a wind turbine power train
• Fig.2 is a graph of time versus torque resulting from an example in which speed and power of the generator as well as estimated and measured torque at the low speed shaft is shown.
• a wind turbine power train denoted as a whole with reference numeral 10 is diagrammatically shown in Figure 1.
• Power train 10 serves the purpose of transmitting the input torque Tr from a low speed shaft 15 of the rotor 20 to a high speed shaft 35 in the generator 30 of the wind turbine through a gearbox 40 such that input torque Tr is converted into electric power.
• the angular velocity ⁇ r of the low speed shaft 15 and the angular velocity ⁇ g of the high speed shaft 35 are related by a speed ratio i.
• the method of the invention allows fatigue damage to be accurately assessed by determining the oscillations in the input torque Tr at a given angular velocity ⁇ r of the wind turbine rotor 20. Assessment of fatigue damage will be useful for design and/or maintenance operations in the wind turbine.
• Torque value Tr at the rotor 20 is first determined from values at the generator, that is torque Tg, moment of inertia Ig, and angular velocity ⁇ g. Said values are available directly from the main power supply of the generator 30, that is, at the high speed shaft 35.
• angular acceleration ⁇ g at the high speed shaft 35 can be then obtained through the time-derivative of the angular velocity ⁇ g at the high speed shaft 35.
• a rainflow-counting algorithm procedure can be applied in order to assess variations in said torque value Tr.
• Data obtained through the rainflow- counting algorithm procedure can be in the form of a data matrix (such as a Markov's matrix), including the number of torque cycles for every torque range at every mean torque.
• This rainflow counting matrix must be stored and updated every certain period of time, adding the new torque cycles to the previous ones in order to know the total number of cycles that have been applied to the power train. Having that, it is possible to obtain anytime a matrix that is representative of the fatigue loads applied to the system during its working life.
• the relationship between the torque and the stress at every point of every component that is needed has to be calculated whether by analytical calculation or by finite element methods.
• This calculation has to take into account the geometry of the part and the mechanical characteristics of the material from which said part is made.
• This relationship can be as simple as a unitary factor (linear relationship) or any non linear equation that relates the torque with local stress or strain. Said factor or non linear equation is previously obtained whether by an analytical calculation or by finite element method (FEM).
• the damage produced to the power train components by the torque cycles can be calculated. Particularly, this is carried out by comparing the sum of the cycles of all of the data obtained through the rainflow-counting algorithm procedure including stress or strain cycle values at different ranges and with different cycle mean value levels to SN/ ⁇ N curves of the corresponding materials of the components being analyzed.
• a further step of the method of the invention may exist consisting in determining accumulated fatigue damage during a period of time in any of the parts of the power train 10 by comparing the number of cycles performed with a predetermined limit for a SN curve for each load range, for example by applying the Miner's rule.
• a warning signal may be sent to a control unit when accumulated fatigue damage during a period of time exceeds a predetermined value for being able to investigate about what it has happened on a wind turbine or a wind farm so that appropriate measures can be taken accordingly.
• the curve obtained by the estimator follows the real values with a high degree of accuracy.
• a constant delay is observed on the estimated torque value due to the calculation of the angular acceleration ⁇ g at the high speed shaft 35 (the generator 30).
• time-derivative of the angular velocity ⁇ g at the high speed shaft 35 is calculated and noise at high frequencies in the obtained signal is to be removed.
• a filter is applied that provides a sharper but somewhat delayed signal. This is not a problem to the aim of the present invention which is to obtain the most approximated data to reality for monitoring fatigue in the wind turbine power train.
• the method of the invention can be suitably implemented in each of the wind turbines or at least in one representative wind turbine in each wind farm, whereby the accumulated damage for specific loads in each wind turbine or wind farm can be monitored. This is feasible since the method of the present invention makes use of two parameters for calculation, that is, the electric torque at the generator (available from the generated electric power) and the angular velocity ⁇ g at the generator.
• 64x64 data matrix 64x64 data matrix. These data may be passed once a week so that damage accumulation can be performed on a monitoring and recording data system. Data in the form of a table would be stored, e.g. in a database of the recording data system. Thus, the sum of the cycles of all the matrices that the wind turbine has been passing over its working life will be the cycles to be compared to SN/ ⁇ N curves corresponding to the material of the component about which the remaining life is desired to ascertain. An accumulated cycle matrix is therefore constructed.

Landscapes

• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Wind Motors (AREA)
• Testing Of Devices, Machine Parts, Or Other Structures Thereof (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (1)

Family

ID=39423675

Family Applications (1)

Country Status (8)

Cited By (2)

Families Citing this family (37)

Citations (4)

Family Cites Families (3)

• 2007
  • 2007-10-24 EP EP07119225A patent/EP2053241A1/en not_active Withdrawn
• 2008
  • 2008-10-21 CN CN2008801129440A patent/CN101835974B/zh not_active Expired - Fee Related
  • 2008-10-21 CA CA2701979A patent/CA2701979A1/en not_active Abandoned
  • 2008-10-21 US US12/739,499 patent/US8332164B2/en active Active
  • 2008-10-21 WO PCT/EP2008/064221 patent/WO2009053365A1/en not_active Ceased
  • 2008-10-21 AU AU2008314694A patent/AU2008314694B2/en not_active Ceased
  • 2008-10-21 BR BRPI0818383A patent/BRPI0818383A8/pt not_active IP Right Cessation
  • 2008-10-21 JP JP2010530431A patent/JP5242694B2/ja not_active Expired - Fee Related
  • 2008-10-21 EP EP08841271A patent/EP2212552A1/en not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (4)

Also Published As

Similar Documents

Legal Events