CN105545591A - Method for inhibiting turbulence effect on wind generating set - Google Patents
Method for inhibiting turbulence effect on wind generating set Download PDFInfo
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- CN105545591A CN105545591A CN201511020424.5A CN201511020424A CN105545591A CN 105545591 A CN105545591 A CN 105545591A CN 201511020424 A CN201511020424 A CN 201511020424A CN 105545591 A CN105545591 A CN 105545591A
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- generating set
- wind speed
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- 238000000034 method Methods 0.000 title claims abstract description 21
- 230000000694 effects Effects 0.000 title claims abstract description 10
- 230000002401 inhibitory effect Effects 0.000 title abstract 2
- 238000005259 measurement Methods 0.000 claims description 15
- 230000001629 suppression Effects 0.000 claims description 5
- 238000011217 control strategy Methods 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 238000010248 power generation Methods 0.000 description 4
- 238000012937 correction Methods 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 206010008190 Cerebrovascular accident Diseases 0.000 description 1
- 208000006011 Stroke Diseases 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
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
- F03D7/00—Controlling wind motors
-
- 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
- F05B2270/32—Wind speeds
-
- 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
- F05B2270/321—Wind directions
-
- 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
Abstract
The invention relates to a method for inhibiting the turbulence effect on a wind generating set. When the wind generating set is in operation, the real-time wind speed is measured through an anemometer, the real-time wind direction is measured through a wind vane, the turbulence factor under the real-time wind condition is calculated by a wind generator controller according to the real-time wind speed and the real-time wind direction, and the wind generating set is controlled by taking the turbulence factor as the control target during the yaw control process of the wind generating set, so as to inhibit the influence of the turbulence intensity on the wind generating set, and ensure the generating efficiency and the service life of the wind generating set.
Description
Technical field
The present invention relates to a kind of wind power generating set suppresses Turbulent Flow Effects method when the complicated wind regime such as high turbulent flow run.
Background technique
Wind power generating set absorbs wind energy by blade rotary, be the kinetic energy of vane rotary by wind energy transformation, by gear-box, kinetic energy is carried out transmitting (for direct-drive permanent magnet wind power generator group, then there is no this link), be electric energy by generator by kinetic transformation, go out finally by the power delivery of power transmission network by generation.
The change of nature apoplexy is very complicated, and its size, direction are at every moment occurring to change, and this absorbs wind energy safely and effectively to wind power generating set and bring very large challenge.First be that can wind power generating set possess real-time and accuracy to the measurement by its wind speed and wind direction; Next be wind power generating set to wind regime, as wind speed size and wind vector, can make and responding in time and accurately; Be finally that can wind power generating set make prediction to the change of wind regime, this prediction is considering from control strategy angle of short-term, and a consideration anemoscope is the wind power generating set of lower wind direction design here.The wind speed that anemoscope obtains is by the wind speed of blade, and the wind direction that wind vane records also has been subject to the impact of vane rotary wake flow, also namely this anemoscope can not measure wind speed and the wind speed variance ratio in wind power generating set front, also can not record the wind direction of subsequent time by blower fan in advance, certain wind vector is more unknowable.
Turbulence intensity (turbulenceintensity, be abbreviated as TI) refer to the amplitude of 10 minutes wind speed change at random, be 10 minutes mean wind velocitys standard deviation and the same period mean wind velocity ratio, being the usual fatigue load of bearing during wind power generating set is run, is one of important parameter of IEC61400-1 fan safe grade classification.Turbulent flow Producing reason mainly contains two, and one is when air current flow, and air-flow can be subject to friction or the retardation of surface roughness, and Another reason is the air-flow vertical motion because air density difference and atmospheric temperature difference cause.Under normal circumstances, above-mentioned two reasons often cause the generation of turbulent flow simultaneously.In neutral atmosphere, can there is adiabatic cooling in air, and reach thermal equilibrium with ambient temperature along with the rising of self, therefore in neutral atmosphere, turbulence intensity size depends on roughness of ground surface situation completely.
In earlier stage, the turbulence intensity local according to the observation data assessment of anemometer tower, in this, as one of wind power generating set type selecting index for Construction of Wind Power.Turbulence intensity being included in type selecting index is more consider from wind power generating set fatigue load aspect, and chosen wind power generating set can meet the impact of the usual fatigue load that turbulence intensity produces.
Suppressing method at present for wind power generating set turbulivity does not clearly propose, and mainly tackles from two aspects for turbulence intensity.On the one hand, turbulence intensity is considered as one of design objective when overall design by wind power generating set, but this is a kind of way of passive reply turbulence intensity, and it reduces high Turbulent Flow Effects to increase wind power generating set cost for cost reaches; On the other hand, wind power generating set performance parameter such as power curve under the impact of high turbulence intensity cannot reach unit design power curve, is how the direction instantly studied by new algorithm correction turbulence intensity on impacts such as power curve.Above two kinds of ways or be increase the cost of wind power generating set to strengthen the adaptability of high turbulence, or be the theoretical correction not good to wind power generating set operational effect, all there is no the high turbulence intensity of reply of active to the impact of wind power generating set.
Summary of the invention
The object of the invention is to overcome prior art and initiatively cannot tackle the shortcoming that high turbulence intensity affects wind power generating set power generation performance, propose a kind of method suppressing wind power generating set Turbulent Flow Effects.
The present invention according to wind speed, the information such as wind direction, adopt corresponding control strategy to suppress high turbulent flow on wind power generating set power generation performance impact.
When wind power generating set is run, real-time wind speed is measured by anemoscope, real-time wind direction measured by wind vane, wind driven generator controller is according to information such as real-time wind speed and real-time wind directions, calculate the turbulent flow factor under real-time wind regime, in wind generating set yaw control procedure with the turbulent flow factor for control objectives controls wind power generating set, suppress turbulence intensity on the impact of wind power generating set.
The inventive method step is specific as follows:
(1) wind speed is divided into some wind speed territory WSR by wind turbine generator system controller, is expressed as WSR{S
1, S
2, S
3, S
4..., S
n, wherein S
1, S
2, S
3, S
4..., S
nrepresent wind speed, and n is less than or equal to 10;
(2) according to the wind speed territory that step 1 divides, time constant corresponding for wind speed territory is defined as time-domain TCR, is expressed as TCR{T
1, T
2, T
3, T
4..., T
m, wherein T
1, T
2, T
3, T
4..., T
mthe expression time, wind speed territory WSR and time-domain TCR one_to_one corresponding;
(3) the actual measurement wind speed that anemoscope records is denoted as S
real, actual measurement wind speed S is determined by tabling look-up
realvalue S in the WSR of wind speed territory, and meet S ∈ WSR, in time-domain TCR, find the time T that is corresponding with S, and meet T ∈ TCR;
(4) the actual measurement wind direction that wind vane records is denoted as D
real, and actual measurement wind direction D
realwith actual measurement wind speed S
realfor the measured value of synchronization;
(5) the time T using step 3 to obtain, the actual measurement wind direction D that step 4 obtains
real, obtain turbulent flow factor E according to formula (1)
real:
E
Real＝(D
Real-E
Real-1)/T+E
Real-1(1)
Wherein E
real-1for the turbulent flow factor that a upper computation of Period obtains;
(6) in wind power generating set running, wind turbine generator system controller controls wind wheel and follows the tracks of wind direction, makes the augular offset of wind wheel and wind direction level off to 0, namely makes the angle of control wind wheel level off to the turbulent flow factor.
Wind speed characteristics is incorporated in the control of wind power generating set by above controlling method, in realization accurately on the basis of wind, weakens the impact of turbulence intensity on wind power generating set fatigue load.
The present invention is without the need to introducing new sensor external equipment, cost of production or device hardware upgrade cost can not be increased, just can realize the suppression to Turbulent Flow Effects by the integration process to existing wind power generating set operation information and the optimization to unit allocation algorithm.
Accompanying drawing explanation
Fig. 1 is that the present invention suppresses wind power generating set turbulence intensity schematic diagram;
Fig. 2 is schematic flow sheet of the present invention;
Fig. 3 is the corresponding relation figure of wind speed territory of the present invention and time-domain.
Embodiment
The present invention is further illustrated below in conjunction with the drawings and specific embodiments.
Wind power generating set is run in the area of high turbulence intensity, its power generation performance and life-span are all affected, the method of the suppression turbulence intensity proposed by the present invention, weakens the impact of high turbulence intensity on generator set, thus ensures power generation performance and the life-span of generator set.
As shown in Figure 1, the present invention measures real-time wind speed by the anemoscope on wind turbine cabin, real-time wind direction measured by wind vane, wind driven generator controller is according to information such as real-time wind speed and real-time wind directions, calculate the turbulent flow factor under real-time wind regime, determine that this wind energy turbine set unit is positioned at high turbulence intensity area, definition wind speed territory and time-domain, the turbulent flow factor is calculated according to real-time wind speed and direction data, the turbulent flow factor is incorporated in wind driven generator yaw control strategy, controls active suppression turbulent flow to the impact of wind-driven generator with the driftage of reality.
As shown in Figure 2, the flow process of the inventive method is as follows:
Step 01, definition wind speed territory WSR, for step 03 T computing time prepares.
Step 02, definition time territory TCR, and wind speed territory WSR and time-domain TCR one_to_one corresponding, its corresponding relation is as shown in Figure 3;
Step 03, calculates time T corresponding to Wind turbines actual measurement wind speed according to the corresponding relation of actual measurement wind speed, step 01 and step 02;
Step 04, obtains the real-time wind direction that real-time wind speed is corresponding;
Step 05, calculates the turbulent flow factor;
Step 06, using the target that the turbulent flow factor that calculates in step 05 controls as driftage, wind turbine generator system controller controls wind wheel and follows the tracks of wind direction, makes the augular offset of wind wheel and wind direction level off to 0, and control yaw angle levels off to the turbulent flow factor;
Step 07, the deviation of Real-Time Monitoring driftage to wind, makes the deviation of driftage to wind level off to 0;
Step 08, realizes the suppression of During yaw to turbulence intensity.
Just turbulence intensity is incorporated in the middle of wind power generating set control strategy by above flow process, the influence factor of turbulence intensity to wind power generating set participates in wind power generating set control, the impact of turbulence intensity on wind power generating set is suppressed by yaw system.
Claims (2)
1. one kind is suppressed the method for wind power generating set Turbulent Flow Effects, it is characterized in that: described method is when wind power generating set is run, real-time wind speed is measured by anemoscope, real-time wind direction measured by wind vane, wind driven generator controller is according to information such as real-time wind speed and real-time wind directions, calculate the turbulent flow factor under real-time wind regime, in wind generating set yaw control procedure with the turbulent flow factor for control objectives controls wind power generating set, suppress turbulence intensity on the impact of wind power generating set.
2., according to the method for suppression wind power generating set Turbulent Flow Effects according to claim 1, it is characterized in that: described method step is as follows:
(1) wind speed is divided into some wind speed territory WSR by wind turbine generator system controller, is expressed as WSR{S
1, S
2, S
3, S
4..., S
n, wherein S
1, S
2, S
3, S
4..., S
nrepresent wind speed, and n is less than or equal to 10;
(2) according to the wind speed territory that step (1) divides, time constant corresponding for wind speed territory is defined as time-domain TCR, is expressed as TCR{T
1, T
2, T
3, T
4..., T
m, wherein T
1, T
2, T
3, T
4..., T
mthe expression time, wind speed territory WSR and time-domain TCR one_to_one corresponding;
(3) the actual measurement wind speed that anemoscope records is denoted as S
real, actual measurement wind speed S is determined by tabling look-up
realvalue S in the WSR of wind speed territory, and meet S ∈ WSR, in time-domain TCR, find the time T that is corresponding with S, and meet T ∈ TCR;
(4) the actual measurement wind direction that wind vane records is denoted as D
real, and actual measurement wind direction D
realwith actual measurement wind speed S
realfor the measured value of synchronization;
(5) the time T using step (3) to obtain, the actual measurement wind direction D that step (4) obtains
real, obtain turbulent flow factor E according to formula (1)
real:
E
Real＝(D
Real-E
Real-1)/T+E
Real-1(1)
Wherein E
real-1for the turbulent flow factor that a upper computation of Period obtains, T is the time corresponding with S in time-domain TCR;
In wind power generating set running, wind turbine generator system controller controls wind wheel and follows the tracks of wind direction, makes the augular offset of wind wheel and wind direction level off to 0, namely makes the angle of control wind wheel level off to turbulent flow factor E
real.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201511020424.5A CN105545591B (en) | 2015-12-30 | 2015-12-30 | A kind of method for suppressing wind power generating set Turbulent Flow Effects |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201511020424.5A CN105545591B (en) | 2015-12-30 | 2015-12-30 | A kind of method for suppressing wind power generating set Turbulent Flow Effects |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN105545591A true CN105545591A (en) | 2016-05-04 |
| CN105545591B CN105545591B (en) | 2018-04-06 |
Family
ID=55825046
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201511020424.5A Expired - Fee Related CN105545591B (en) | 2015-12-30 | 2015-12-30 | A kind of method for suppressing wind power generating set Turbulent Flow Effects |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN105545591B (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108105030A (en) * | 2017-12-28 | 2018-06-01 | 中国船舶重工集团海装风电股份有限公司 | A kind of yaw calibration method based on wind turbine sensor |
| CN109958574A (en) * | 2017-12-22 | 2019-07-02 | 北京金风科创风电设备有限公司 | Load reduction control method and device for wind generating set |
| CN111120202A (en) * | 2018-10-31 | 2020-05-08 | 北京金风科创风电设备有限公司 | Yaw angle adjusting method, device, medium and equipment of wind generating set |
| CN111120219A (en) * | 2018-10-31 | 2020-05-08 | 北京金风科创风电设备有限公司 | Method and device for determining fatigue load of wind generating set |
| CN111828247A (en) * | 2020-07-28 | 2020-10-27 | 中国华能集团清洁能源技术研究院有限公司 | Method, system and device for standardized correction of turbulence power curve |
| CN113469526A (en) * | 2021-06-30 | 2021-10-01 | 华能国际电力股份有限公司广西清洁能源分公司 | Wind power plant sensing system suitable for complex wind area |
| CN113586336A (en) * | 2021-08-10 | 2021-11-02 | 上海电气风电集团股份有限公司 | Control method and control device of wind generating set and computer readable storage medium |
| CN113883009A (en) * | 2021-09-27 | 2022-01-04 | 太原重工股份有限公司 | Wind turbine generator system anemometer angle self-optimization method |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1182282A (en) * | 1997-09-11 | 1999-03-26 | Mitsubishi Heavy Ind Ltd | Power control of wind power generator |
| CN102011692A (en) * | 2010-11-26 | 2011-04-13 | 浙江运达风电股份有限公司 | Method for controlling stable operation of wind-powered generator set under different turbulence terrains |
| GB2475865A (en) * | 2009-12-02 | 2011-06-08 | Vestas Wind Sys As | Anti-Oscillation Apparatus And Technique For Securing Wind Turbine Blades Against Oscillations |
| CN102251926A (en) * | 2010-07-15 | 2011-11-23 | 大唐南京自动化有限公司 | Turbulence suppression method of wind driven generator |
-
2015
- 2015-12-30 CN CN201511020424.5A patent/CN105545591B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1182282A (en) * | 1997-09-11 | 1999-03-26 | Mitsubishi Heavy Ind Ltd | Power control of wind power generator |
| GB2475865A (en) * | 2009-12-02 | 2011-06-08 | Vestas Wind Sys As | Anti-Oscillation Apparatus And Technique For Securing Wind Turbine Blades Against Oscillations |
| CN102251926A (en) * | 2010-07-15 | 2011-11-23 | 大唐南京自动化有限公司 | Turbulence suppression method of wind driven generator |
| CN102011692A (en) * | 2010-11-26 | 2011-04-13 | 浙江运达风电股份有限公司 | Method for controlling stable operation of wind-powered generator set under different turbulence terrains |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109958574A (en) * | 2017-12-22 | 2019-07-02 | 北京金风科创风电设备有限公司 | Load reduction control method and device for wind generating set |
| CN108105030A (en) * | 2017-12-28 | 2018-06-01 | 中国船舶重工集团海装风电股份有限公司 | A kind of yaw calibration method based on wind turbine sensor |
| CN108105030B (en) * | 2017-12-28 | 2019-10-18 | 中国船舶重工集团海装风电股份有限公司 | A kind of yaw calibration method based on blower sensor |
| CN111120202A (en) * | 2018-10-31 | 2020-05-08 | 北京金风科创风电设备有限公司 | Yaw angle adjusting method, device, medium and equipment of wind generating set |
| CN111120219A (en) * | 2018-10-31 | 2020-05-08 | 北京金风科创风电设备有限公司 | Method and device for determining fatigue load of wind generating set |
| CN111120202B (en) * | 2018-10-31 | 2021-07-20 | 北京金风科创风电设备有限公司 | Yaw angle adjusting method, device, medium and equipment of wind generating set |
| CN111828247A (en) * | 2020-07-28 | 2020-10-27 | 中国华能集团清洁能源技术研究院有限公司 | Method, system and device for standardized correction of turbulence power curve |
| CN111828247B (en) * | 2020-07-28 | 2021-06-29 | 中国华能集团清洁能源技术研究院有限公司 | Method, system and device for standardized correction of turbulence power curve |
| CN113469526A (en) * | 2021-06-30 | 2021-10-01 | 华能国际电力股份有限公司广西清洁能源分公司 | Wind power plant sensing system suitable for complex wind area |
| CN113586336A (en) * | 2021-08-10 | 2021-11-02 | 上海电气风电集团股份有限公司 | Control method and control device of wind generating set and computer readable storage medium |
| CN113883009A (en) * | 2021-09-27 | 2022-01-04 | 太原重工股份有限公司 | Wind turbine generator system anemometer angle self-optimization method |
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