# US 11,078,886 B2 · Wind turbine generator and method of controlling wind turbine generator

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- Number: US 11,078,886 B2
- Document ID: US11078886B2
- Status: Granted
- Kind: B2
- Application number: 17/040,371
- Filed: 2019-03-25
- Published: 2021-02-25
- Granted: 2021-08-03
- Earliest claimed: 2018-03-29
- Assignees: Vestas Offshore Wind A/S
- Applicants: Mhi Vestas Offshore Wind A/S
- Inventors: Keita Ishimitsu
- Web page: https://patentgrep.com/patent/US11078886B2

## CPC

- F03D 7/0292: {to reduce fatigue}
- F03D 7/04: Automatic control; Regulation
- F03D 17/00: Monitoring or testing of wind motors, e.g. diagnostics (testing during commissioning of wind motors F03D13/30)
- H02P 9/006: {Means for protecting the generator by using control (control effected upon generator excitation circuit to reduce harmful effects of overloads or transients H02P9/10)}
- F03D 7/0296: {to prevent, counteract or reduce noise emissions}
- F05B 2270/309: Rate of change of parameters
- F05B 2270/332: Maximum loads or fatigue criteria
- F05B 2270/333: Noise or sound levels
- F05B 2270/802: Calibration thereof
- H02P 2101/15: for wind-driven turbines
- Y02E 10/72: Wind turbines with rotation axis in wind direction
- F03D: WIND MOTORS
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- 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

A method of controlling a wind turbine includes: accumulating a cumulative damage degree Du of each evaluation point of the wind turbine in a unit period over an entire evaluation period, to calculate a total cumulative damage degree Dt of the entire evaluation period at each evaluation point; comparing the Dt at each of the evaluation points with a first threshold value (P*Q) and comparing an increase rate dDt/dt of Dt at each evaluation point with a second threshold value to evaluate fatigue of a part to which each evaluation point belongs; and determining an operation mode based on an evaluation result into a normal operation mode or a low-load operation mode in which an output is suppressed compared with the normal operation mode.

## Claims

### Claim 1

A method of controlling a wind turbine generator, comprising:
accumulating a cumulative damage degree Du of each evaluation point of the wind turbine generator in a unit period over an entire evaluation period, to calculate a total cumulative damage degree Dt of the entire evaluation period at each evaluation point;
comparing the total cumulative damage degree Dt at each of the evaluation points calculated by the calculation step with a predetermined first threshold value (P*Q) and comparing an increase rate dDt/dt of the total cumulative damage degree Dt at each evaluation point with a second threshold value to evaluate fatigue of a part to which each evaluation point belongs in the wind turbine generator; and
determining an operation mode of the wind turbine generator based on an evaluation result of the evaluation step into a normal operation mode when the total cumulative damage degree Dt is less than the first threshold value (P*Q) and the increase rate dDt/dt is less than the second threshold value, and determining the operation mode into a low-load operation mode in which an output is suppressed as compared with the normal operation mode if the total cumulative damage degree Dt is equal to or larger than the first threshold value (P*Q) or the increase rate dDt/dt is equal to or larger than the second threshold value,
wherein the step of determining the operation mode is performed repeatedly at a determination interval that varies between 1 day and 6 months,
wherein after the total cumulative damage degree Dt increases above the first threshold value (P*Q) and the operation mode is changed to the low-load operation mode, the operation mode returns from the low-load operation mode to the normal operation mode when it is determined that the total cumulative damage degree Dt again is below the first threshold value (P*Q) in an upcoming operation-mode determination in which the step of determining the operation mode is performed after the determination interval.

### Claim 2 (depends on 1)

The method of controlling a wind turbine generator according to claim 1,
wherein, in the operation mode determination step, a pitch angle of a wind turbine blade is set to be a feather side compared to the normal operation mode when the evaluation point belongs to any one of a top portion of a tower, a bottom portion of the tower, a rotor hub or a rotor blade of the wind turbine generator.

### Claim 3 (depends on 1)

The method of controlling a wind turbine generator according to claim 1,
wherein, when the evaluation point belongs to a drive train in the wind turbine generator, the rotation speed of a rotor is limited to be lower compared to the normal operation mode.

### Claim 4 (depends on 1)

The method of controlling a wind turbine generator according to claim 1, further comprising:
an acquisition step of acquiring stress change information indicating a time-series change of stress occurring at each evaluation point within the unit period;
a first calculation step of calculating a stress amplitude Fi of stress generated in each evaluation point in the unit period and a repetition number ni of the stress amplitude Fi based on the stress change information acquired in the acquisition step; and
a second calculation step of calculating the cumulative damage degree Du of each evaluation point in the unit period based on a calculation result of the first calculation step and the information of the SN diagram corresponding to the material of each evaluation point.

### Claim 5 (depends on 4)

The method of controlling a wind turbine generator according to claim 4,
wherein the cumulative damage degree Du in the second calculation step is calculated based on the following equation (i);
D
u
=
Σ
⁢
n
i
N
i
(
i
)
wherein, Ni is a breaking repetition number corresponding to the stress amplitude Fi.

### Claim 6 (depends on 1)

The method of controlling a wind turbine generator according claim 1,
wherein in the predetermined first threshold value (P*Q), P is the fraction of service life at the time of evaluation of the wind turbine generator, and Q increases in the range of 0.05 to 0.95 depending on the cumulative operation of the wind power generation equipment.

### Claim 7 (depends on 1)

The method of controlling a wind turbine generator according claim 1, further comprising
a rotation speed determination step of setting the operation mode of the wind turbine generator as the normal operation mode when the rotor rotation speed (rpm) is within a noise request level range, and reduce the rotor rotation speed as the rotor rotation speed which falls within the range of the noise request level when the rotor rotation speed exceeds the noise request level range.

### Claim 8 (depends on 1)

The method of controlling a wind turbine generator according claim 1,
wherein the cumulative damage degree Du is accumulated for each range of the stress amplitude in the SN diagram corresponding to the material of each evaluation point.

### Claim 9 (depends on 1)

The method of controlling a wind turbine generator according claim 1, further comprising the step of
determining an operation mode of the wind turbine generator based on an evaluation result of the evaluation step into an enhanced operation mode when the total cumulative damage degree Dt is less than 95% of the first threshold value (P*Q) in which the second threshold value is increased by at least 10%; preferably the enhanced operation mode is entered when the total cumulative damage degree Dt is less than 90% of the first threshold value, more preferably less than 80% of the first threshold value; preferably the second threshold value is increased by at least 20% and more preferably the second threshold value is increased by at least 50%.

### Claim 10 (depends on 1)

The method of controlling a wind turbine generator according claim 1, further comprising the step of calibrating the total cumulative damage degree Dt by
measuring the actual total cumulative damage of the wind turbine generator by a non-destructive technique, and
adjusting the total cumulative damage degree Dt to the actual cumulative damage.

### Claim 11 (depends on 1)

A wind turbine generator, comprising:
a rotor configured to receive wind energy and rotate,
a generator to which the rotational force of the rotor is transmitted, and
a control system for realizing the control method according to claim 1.