CN106780155B - Method for evaluating output power of wind driven generator under intermittent wind speed - Google Patents

Method for evaluating output power of wind driven generator under intermittent wind speed Download PDF

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CN106780155B
CN106780155B CN201710057961.XA CN201710057961A CN106780155B CN 106780155 B CN106780155 B CN 106780155B CN 201710057961 A CN201710057961 A CN 201710057961A CN 106780155 B CN106780155 B CN 106780155B
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梁定康
王鹏
韩肖清
秦文萍
宋述勇
王金浩
贾燕冰
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Electric Power Research Institute of State Grid Shanxi Electric Power Co Ltd
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Abstract

The invention relates to evaluation of output power of a grid-connected wind driven generator, in particular to an evaluation method of the output power of the wind driven generator under intermittent wind speed. The problem that in the prior art, no research on an output model of the wind driven generator at the intermittent wind speed exists, namely an evaluation method of the output power of the wind driven generator at the intermittent wind speed is lacked is solved. The invention determines the intermittent wind speed interval by utilizing the fractal dimension in the chaos theory. The intermittent wind speed in the intermittent wind speed interval is determined by using the turbulence kinetic energy of the power spectral density function, so that the strong fluctuation wind speed in the wind speed data can be accurately positioned. According to the momentum-phyllotoxin theory, the wind energy absorbed by the blades is evaluated by utilizing the rotating speed and the wind speed of the blades, and the output power of the fan is evaluated according to the power conversion efficiency of the fan. And a theoretical basis is laid for planning a high wind power permeability power system. Compared with a classical wind driven generator power output model, the method can accurately evaluate the output power of the fan under the condition of strong wind speed fluctuation.

Description

Method for evaluating output power of wind driven generator under intermittent wind speed
Technical Field
The invention relates to evaluation of output power of a grid-connected wind driven generator, in particular to an evaluation method of the output power of the wind driven generator under intermittent wind speed.
Background
Due to the variability and uncontrollable nature of wind speed, wind generators (referred to as wind turbines for short) are subject to large disturbances almost all the time, and such disturbances will have a certain influence on the unit itself or on the power system connected with the unit. Therefore, when relevant problems such as operation, planning and dynamic characteristics of the grid-connected wind power plant are researched, a wind speed and wind power output model suitable for the problems needs to be established, so that the wind speed change characteristic is analyzed, and the wind power plant power output capacity under a certain wind speed condition is researched.
The wind speed model affects the resolution of the power system operation planning problem. In practical engineering application, the system operation planning problem is mostly researched on the basis of the average wind speed, and the influence of the strong fluctuation wind speed on the power system is not considered. The spatial and temporal distribution of the wind speed is very strong and intermittent, and the uncertainty and the chaotic characteristic of the wind speed are far stronger than the load. The intermittent wind speed refers to a wind speed which fluctuates sharply for a short time. An accurate intermittent wind speed model is established, and the wind speed with large fluctuation degree is determined, so that the method is of great importance to solving the planning and operation problems of the power system.
The accurate wind power generator power output model is the key for solving the planning and operation problems of the power system, and in order to analyze the influence of intermittent wind speed on the output power of the wind power plant, the wind power generator power output model considering the rotating speed and time lag of the blades is established. The influence of the hysteresis of the rotating speed of the blades on the output power of the fan when the wind speed changes is ignored by the traditional fan output model, the rotating speed of the blades is considered to be the optimal rotating speed corresponding to the current wind speed all the time, the output of the fan is the maximum output power corresponding to the current wind speed, namely the step change of the rotating speed of the blades is considered by the traditional fan output model, and the output power of a wind power plant when the wind speed changes rapidly is exaggerated. In practical engineering application, the influence of the output power of a wind power plant on system planning and operation is mostly researched based on stable wind speed according to a classical wind turbine model. An output model of the wind driven generator considering the intermittent wind speed is yet to be researched.
Disclosure of Invention
The invention solves the problem that the output model research of the wind driven generator under the intermittent wind speed is not available in the prior art, namely the problem that the method for evaluating the output power of the wind driven generator under the intermittent wind speed is lacked, and provides the method for evaluating the output power of the wind driven generator under the intermittent wind speed.
The invention is realized by adopting the following technical scheme: the method for evaluating the output power of the wind driven generator under the intermittent wind speed is realized by the following steps:
determination of intermittent wind speed interval
Decomposing historical wind speed data with a certain time length into N with the time length of tkAnalyzing the wind speed fluctuation degree of each wind speed interval one by one, and determining intermittent wind speed intervals;
the wind speed data curve of each wind speed interval is further decomposed into N equal divisions with the time length delta t, the larger the numerical value of N is, the higher the calculation accuracy is, each equal division is marked by a rectangular frame with the delta t as a short side, and N iskOne of the wind speed intervals, i.e. the sum V of the rectangular areas of all the rectangular frames of the ith wind speed intervaliComprises the following steps:
Figure BDA0001217093450000011
fractal dimension C of ith wind speed intervaliComprises the following steps:
Figure BDA0001217093450000012
in the formula: v. ofj,minAnd vj,maxWind speed minimum and maximum values for the jth Δ t, j ═ 1,2, 3 … … N, respectively;
according to the reference: study on fractal and chaotic characteristics of Chengxiang, Quanlihong, Hufei, etc. [ J ] gust]Climate and environmental study, 2007, 03: 256-rIf the fractal dimension C of the ith wind speed intervaliGreater than CrThe wind speed fluctuation is strong and is defined as an intermittent wind speed interval;
second, determination of intermittent wind speed
In the intermittent wind speed interval, the wind speeds at all time points are not the intermittent wind speeds, and the wind speed change intensity in the intermittent wind speed interval needs to be analyzed one by one, so that the wind speed with strong volatility is determined as the intermittent wind speed;
in the intermittent wind speed interval, the wind speed sampling time is taken as the basis, and the intermittent wind speed interval is divided into NmThe wind speed of each wind speed section is divided into a plurality of wind speed sections,method for analyzing turbulence characteristics of intermittent wind speed by utilizing Von Karman power spectrum density function in meteorological research[2]Decomposing each wind speed section by different frequency components according to a power spectral density function S (f),
Figure BDA0001217093450000021
Figure BDA0001217093450000022
Figure BDA0001217093450000023
in the formula: h 1,2, …, Nm；σhIs the standard deviation of the turbulent wind speed for the h wind speed segment; l is a turbulence scale, and the empirical value is 300 meters; v. ofh,m,、vh,mxAnd vh,mnAverage wind speed, maximum wind speed and minimum wind speed for the h wind speed section;
the wind speed fluctuation intensity is in direct proportion to the turbulence kinetic energy provided by high-frequency components in a wind speed spectrum density function; the percentage of the turbulent kinetic energy provided by the independent wind speed high-frequency component in the total kinetic energy is as follows:
Figure BDA0001217093450000024
in the formula: f. ofrIs a high frequency reference, according to the reference: colossal bin, sonelili, linshixing, etc. comparison of two analytical methods for turbulence characteristics of wind and use thereof [ J]University of college (nature science edition), 2006, 01: 27-32. determining the value; if P ishLess than reference value Pr，PrThe value is an empirical value, the value is 0.3, the fluctuation of the wind speed in the h-th wind speed section is weak, and the influence of the wind speed change on the system operation is ignored; if P ishGreater than PrThe wind speed fluctuation of the h-th wind speed section is strong, and the wind speed of the h-th wind speed section is defined as an intermittent wind speed;
third, determining the output power of the wind driven generator under the intermittent wind speed
Decomposing historical wind speed data with a certain time length into N with the time length of tkA plurality of wind speed intervals, wherein the number of the intermittent wind speed intervals is NP：
Figure BDA0001217093450000025
N is in intermittent wind speed intervalmA number of wind speed segments of intermittent wind speed NW：
Figure BDA0001217093450000026
When the wind speed changes, the blades are influenced by inertia, and the rotating speed of the blades gradually changes. The classical fan output model considers the step change of the rotating speed of the blades, and the output power of the wind power plant is exaggerated when the wind speed changes rapidly; according to Momentum-leaf Theory (BladeElement-Momentum Theory, BEMT)[3]Evaluating the wind energy absorbed by the blades by using the rotating speed and the wind speed of the blades, and evaluating the output power of the fan according to the power conversion efficiency of the fan;
according to momentum-phyllotoxin theory, dividing a fan blade with the length of D/2 into M phyllotoxins with the width of dr in the direction vertical to the length direction of the fan blade, wherein r is the distance between the phyllotoxins and a rotating shaft of the blade, c is the chord length of the phyllotoxins, and D is the diameter of the rotating track of the outermost end of the blade; at the moment, the chlorophyll with the chord length c and the position r works under the conditions of wind speed v and rotating speed n;
the rotation angular velocity of the phyllanthus element is omega, the inflow wind speed is v, an axial induction factor a and a tangential induction factor a 'are introduced, the horizontal axial velocity of the phyllanthus element is v (1-a), the tangential velocity is omega r (1+ a'), and the axial velocity and the tangential velocity are synthesized into a relative wind speed W; alpha is an attack angle; beta is the phylline pitch angle (known as the phylline pitch angle is the inherent parameter of the blade of the curved engine); the inflow angle phi of the phyllanthus is alpha + beta,
φ＝arctan[v(1-a)/Ωr(1+a′)](9)
under the action of the relative wind speed W, the aerodynamic force applied to the phyllotaxis can be decomposed into a lifting force dF vertical to the direction of the relative wind speed WLAnd a drag dF parallel to the direction of the relative wind speed WD：
Figure BDA0001217093450000031
Figure BDA0001217093450000032
In the formula: ρ is the air density. Inquiring the lift coefficient C of the blade element under different attack angles according to the airfoil aerodynamic characteristic curve provided by the wind driven generator manufacturerlAnd coefficient of resistance Cd；
Phylline lift force dFLAnd chlorophyll resistance dFDDecomposing along the directions parallel to and vertical to the rotating plane of the fan blade to finally obtain the thrust dF for driving the rotation of the luteinmAnd a thrust dF perpendicular to the plane of rotation of the fan bladest：
Figure BDA0001217093450000033
Figure BDA0001217093450000034
In the formula: ct＝(Clsinφ-Cdcos phi) and Cn＝(Clcosφ+Cdsin phi) are respectively a tangential force coefficient and a normal force coefficient;
Figure BDA0001217093450000035
in the formula: sigma is compactness, namely the volume of the solid matter part of the material accounts for the proportion of the total volume, wherein sigma is Bc/2 pi r, and B is the number of the fan blades;
by assuming initial values of the axial induction factor a and the tangential induction factor a ', the values of the axial induction factor a and the tangential induction factor a' are found according to the following method: 1) setting initial values a of an axial induction factor a and a tangential induction factor achAnd a'ch；2) Calculating the inflow angle phi of the phyllanthus, 3) calculating the attack angle α, 4) inquiring the lift coefficient C of the phyllanthus according to the determined attack anglelAnd coefficient of resistance Cd(ii) a 5) Calculating the tangential force coefficient CtAnd normal force coefficient Cn(ii) a 6) Calculating a new axial induction factor anewAnd tangential induction factor a'new(ii) a 7) If so: | ach－anew< | and | a'ch－a'newGiven an infinitesimal minimum, then a ═ ach，a'＝a'ch(ii) a 8) If not: | ach－anew< | and | a'ch－a'new< l, such that ach＝anew，a'ch＝a'newThe above process is repeated starting with the calculation of the inflow angle phi of the phyllanthus until | a is satisfiedch－anew< | and | a'ch－a'new< | until;
thrust dF to drive rotation of the phyllotaxismMultiplying the moment arm to calculate the torque dM of the kth leaf elementk，k＝1，2，……M，
Figure BDA0001217093450000036
Multiplying the torque and the angular speed to calculate the wind power dP absorbed by the kth leaf elementk，
Figure BDA0001217093450000037
Adding the wind power absorbed by each of the two folks to obtain the wind power P absorbed by the whole fanblade，
Figure BDA0001217093450000041
In the formula: m is the total number of the phyllanthus of one blade, and B is the number of the fan blades;
according to the power conversion efficiency of the wind driven generator, the output power P of the fan at the wind speed v and the rotating speed n is evaluatedBEMT，
PBEMT(v,n)＝η×Pblade(v,n) (18)
In the formula: eta is the power conversion efficiency of the fan.
[2] Colossan, sonelili, linshixing, et al. comparison of two analytical methods for turbulence characteristics of wind and its applications [ J ], university of peer (nature science edition), 2006, 01: 27-32.
[3] Great celebration, liuhao, LIM Che Wah, and the like, pneumatic performance of a horizontal axis wind turbine generator based on an improved leaf element momentum theory is calculated [ J ]. the chinese motor engineering report, 2011, 23: 129-134.
The invention determines the intermittent wind speed interval by utilizing the fractal dimension in the chaos theory. The intermittent wind speed in the intermittent wind speed interval is determined by using the turbulence kinetic energy of the power spectral density function, so that the strong fluctuation wind speed in the wind speed data can be accurately positioned. According to the momentum-phyllotoxin theory, the wind energy absorbed by the blades is evaluated by utilizing the rotating speed and the wind speed of the blades, and the output power of the fan is evaluated according to the power conversion efficiency of the fan. And a theoretical basis is laid for planning a high wind power permeability power system.
The evaluation method provided by the invention considers the influence of the wind speed and the rotating speed of the blades on the output power of the fan, and compared with a classical wind driven generator power output model, the evaluation method can accurately evaluate the output power of the fan under the condition of strong wind speed fluctuation. For the evaluation of the output power of the wind power plant under the condition of strong wind speed fluctuation, a monitoring device arranged on the wind power generator can be utilized to record the rotating speed of the blades and the real-time wind speed before and after the change of the wind speed.
Drawings
FIG. 1 is a schematic diagram of a fractal dimension of any wind speed interval covering a rectangular frame for estimating real-time wind speed;
FIG. 2 is a graphical representation of a wind speed power spectral density function;
FIG. 3 is a schematic diagram of lutein and parameters;
FIG. 4 is a schematic view of the analysis of the flow velocity component and the stress on a phyllo with the side of the wind turbine as the view angle
FIG. 5 is a flow chart of the calculation of the induction factor.
Detailed Description
The method for evaluating the output power of the wind driven generator under the intermittent wind speed is realized by the following steps:
determination of intermittent wind speed interval
Decomposing historical wind speed data of a certain time length (such as one year or one quarter or one month) into N with the time length t (such as 10 minutes)kAnalyzing the wind speed fluctuation degree of each wind speed interval one by one, and determining intermittent wind speed intervals;
the wind speed data curve of each wind speed interval is further decomposed into N equal divisions with the time length delta t, the larger the numerical value of N is, the higher the calculation accuracy is, each equal division is marked by a rectangular frame with the delta t as a short side, and N iskOne of the wind speed intervals, i.e. the sum V of the rectangular areas of all the rectangular frames of the ith wind speed intervaliComprises the following steps:
Figure BDA0001217093450000042
fractal dimension C of ith wind speed intervaliComprises the following steps:
Figure BDA0001217093450000043
in the formula: v. ofj,minAnd vj,maxWind speed minimum and maximum values for the jth Δ t, j ═ 1,2, 3 … … N, respectively;
according to the reference: study on fractal and chaotic characteristics of Chengxiang, Quanlihong, Hufei, etc. [ J ] gust]Climate and environmental study, 2007, 03: 256-rIf the fractal dimension C of the ith wind speed intervaliGreater than CrThe wind speed fluctuation is strong and is defined as an intermittent wind speed interval;
second, determination of intermittent wind speed
In the intermittent wind speed interval, the wind speeds at all time points are not the intermittent wind speeds, and the wind speed change intensity in the intermittent wind speed interval needs to be analyzed one by one, so that the wind speed with strong volatility is determined as the intermittent wind speed;
in the intermittent wind speed interval, the wind speed sampling time is taken as the basis, and the intermittent wind speed interval is divided into NmA wind speed section (shown in FIG. 1, N)m6), the turbulence characteristics of intermittent wind speed are analyzed by utilizing Von Karman power spectral density function in meteorological research[2]Each wind speed segment is decomposed by different frequency components according to a power spectral density function s (f), as shown in figure 2,
Figure BDA0001217093450000051
Figure BDA0001217093450000052
Figure BDA0001217093450000053
in the formula: h 1,2, …, Nm；σhIs the standard deviation of the turbulent wind speed for the h wind speed segment; l is a turbulence scale, and the empirical value is 300 meters; v. ofh,m,、vh,mxAnd vh,mnAverage wind speed, maximum wind speed and minimum wind speed for the h wind speed section;
the wind speed fluctuation intensity is in direct proportion to the turbulence kinetic energy provided by high-frequency components in a wind speed spectrum density function; the percentage of the turbulent kinetic energy provided by the independent wind speed high-frequency component in the total kinetic energy is as follows:
Figure BDA0001217093450000054
in the formula: f. ofrIs a high frequency reference, according to the reference: colossal bin, sonelili, linshixing, etc. comparison of two analytical methods for turbulence characteristics of wind and use thereof [ J]University of college (nature science edition), 2006, 01: 27-32. determining the value; if P ishLess than reference value Pr，PrThe value is an empirical value, the value is 0.3, the fluctuation of the wind speed in the h-th wind speed section is weak, and the influence of the wind speed change on the system operation is ignored; if P ishGreater than PrThe wind speed fluctuation of the h-th wind speed section is strong, and the wind speed of the h-th wind speed section is defined as an intermittent wind speed; in the illustration of fig. 1, the wind speed in the 1 st and 6 th sections is defined as an intermittent wind speed;
third, determining the output power of the wind driven generator under the intermittent wind speed
Decomposing historical wind speed data with a certain time length into N with the time length of tkA plurality of wind speed intervals, wherein the number of the intermittent wind speed intervals is NP：
Figure BDA0001217093450000055
N is in intermittent wind speed intervalmA number of wind speed segments of intermittent wind speed NW：
Figure BDA0001217093450000056
When the wind speed changes, the blades are influenced by inertia, and the rotating speed of the blades gradually changes. The classical fan output model considers the step change of the rotating speed of the blades, and the output power of the wind power plant is exaggerated when the wind speed changes rapidly; according to Momentum-leaf Theory (BladeElement-Momentum Theory, BEMT)[3]Evaluating the wind energy absorbed by the blades by using the rotating speed and the wind speed of the blades, and evaluating the output power of the fan according to the power conversion efficiency of the fan;
as shown in fig. 3, according to the momentum-phyll theory, a fan blade with a length of D/2 is divided into M phylls with a width dr in a direction perpendicular to the length direction of the fan blade, r is the distance between the phyll and the rotating shaft of the blade,cthe chord length of the phyllanthus is shown, and D is the diameter of the rotating track at the outermost end of the paddle; at the moment, the chlorophyll with the chord length c and the position r works under the conditions of wind speed v and rotating speed n;
taking the side surface of the wind driven generator as a visual angle, as shown in fig. 4, the rotation angular velocity of the phyllotaxin is Ω, the inflow wind speed is v, an axial induction factor a and a tangential induction factor a 'are introduced, the horizontal axial velocity of the phyllotaxin is v (1-a), the tangential velocity is Ω r (1+ a'), and the axial velocity and the tangential velocity are synthesized into a relative wind speed W; alpha is an attack angle; beta is the phylline pitch angle (the phylline pitch angle is the inherent parameter of the blade of the curved engine); the inflow angle phi of the phyllanthus is alpha + beta,
φ＝arctan[v(1-a)/Ωr(1+a′)](9)
under the action of the relative wind speed W, the aerodynamic force applied to the phyllotaxis can be decomposed into a lifting force dF vertical to the direction of the relative wind speed WLAnd a drag dF parallel to the direction of the relative wind speed WD：
Figure BDA0001217093450000061
Figure BDA0001217093450000062
In the formula: ρ is the air density. Inquiring the lift coefficient C of the blade element under different attack angles according to the airfoil aerodynamic characteristic curve provided by the wind driven generator manufacturerlAnd coefficient of resistance Cd；
Phylline lift force dFLAnd chlorophyll resistance dFDDecomposing along the directions parallel to and vertical to the rotating plane of the fan blade to finally obtain the thrust dF for driving the rotation of the luteinmAnd a thrust dF perpendicular to the plane of rotation of the fan bladest：
Figure BDA0001217093450000063
Figure BDA0001217093450000064
In the formula: ct＝(Clsinφ-Cdcos phi) and Cn＝(Clcosφ+Cdsin phi) are respectively a tangential force coefficient and a normal force coefficient;
Figure BDA0001217093450000065
in the formula: sigma is compactness, namely the volume of the solid matter part of the material accounts for the proportion of the total volume, wherein sigma is Bc/2 pi r, and B is the number of the fan blades;
by assuming initial values of the axial induction factor a and the tangential induction factor a ', the values of the axial induction factor a and the tangential induction factor a' are found according to the following method: 1) setting initial values a of an axial induction factor a and a tangential induction factor achAnd a'ch2) calculating the inflow angle phi of the phyllanthus, 3) calculating the attack angle α, 4) inquiring the lift coefficient C of the phyllanthus according to the determined attack anglelAnd coefficient of resistance Cd(ii) a 5) Calculating the tangential force coefficient CtAnd normal force coefficient Cn(ii) a 6) Calculating a new axial induction factor anewAnd tangential induction factor a'new(ii) a 7) If so: | ach－anew< | and | a'ch－a'newGiven an infinitesimal minimum, then a ═ ach，a'＝a'ch(ii) a 8) If not: | ach－anew< | and | a'ch－a'new< l, such that ach＝anew，a'ch＝a'newThe above process is repeated starting with the calculation of the inflow angle phi of the phyllanthus until | a is satisfiedch－anew< | and | a'ch－a'new< | until;
thrust dF to drive rotation of the phyllotaxismMultiplying the moment arm to calculate the torque dM of the kth leaf elementk，k＝1，2，……M，
Figure BDA0001217093450000071
Multiplying the torque and the angular speed to calculate the wind power dP absorbed by the kth leaf elementk，
Figure BDA0001217093450000072
Adding the wind power absorbed by each of the two folks to obtain the wind power P absorbed by the whole fanblade，
Figure BDA0001217093450000073
In the formula: m is the total number of the phyllanthus of one blade, and B is the number of the fan blades;
according to the power conversion efficiency of the wind driven generator, the output power P of the fan at the wind speed v and the rotating speed n is evaluatedBEMT，
PBEMT(v,n)＝η×Pblade(v,n) (18)
In the formula: eta is the power conversion efficiency of the fan.

Claims (1)

1. A method for evaluating the output power of a wind driven generator at intermittent wind speed is characterized by comprising the following steps:
determination of intermittent wind speed interval
Decomposing historical wind speed data with a certain time length into N with the time length of tkAnalyzing the wind speed fluctuation degree of each wind speed interval one by one, and determining intermittent wind speed intervals;
the wind speed data curve of each wind speed interval is further decomposed into N equal divisions with the time length delta t, the larger the numerical value of N is, the higher the calculation accuracy is, each equal division is marked by a rectangular frame with the delta t as a short side, and N iskOne of the wind speed intervals, i.e. the sum V of the rectangular areas of all the rectangular frames of the ith wind speed intervaliComprises the following steps:
Figure FDA0002588853090000011
fractal dimension C of ith wind speed intervaliComprises the following steps:
Figure FDA0002588853090000012
in the formula: v. ofj,minAnd vj,maxWind speed minimum and maximum values for the jth Δ t, j ═ 1,2, 3 … … N, respectively;
fractal dimension reference value Cr0.55 if the fractal dimension C of the ith wind speed intervaliGreater than CrThe wind speed fluctuation is strong and is defined as an intermittent wind speed interval;
second, determination of intermittent wind speed
In the intermittent wind speed interval, the wind speed sampling time is taken as the basis, and the intermittent wind speed interval is divided into NmWind speed segments, each wind speed segment being decomposed into different frequency components according to a power spectral density function S (f),
Figure FDA0002588853090000013
Figure FDA0002588853090000014
Figure FDA0002588853090000015
in the formula: h 1,2, …, Nm；σhIs the standard deviation of the turbulent wind speed for the h wind speed segment; l is a turbulence scale, and the empirical value is 300 meters; v. ofh,m、vh,mxAnd vh,mnAverage wind speed, maximum wind speed and minimum wind speed for the h wind speed section;
the wind speed fluctuation intensity is in direct proportion to the turbulence kinetic energy provided by high-frequency components in a wind speed spectrum density function; the percentage of the turbulent kinetic energy provided by the independent wind speed high-frequency component in the total kinetic energy is as follows:
Figure FDA0002588853090000016
in the formula: f. ofrIs a high frequency reference value with a value of 1/3; if P ishLess than reference value Pr，PrThe value is an empirical value, the value is 0.3, the fluctuation of the wind speed in the h-th wind speed section is weak, and the influence of the wind speed change on the system operation is ignored; if P ishGreater than PrDenotes the h-th wind speed regionThe wind speed fluctuation of the segment is strong, and the wind speed of the h wind speed section is defined as the intermittent wind speed;
third, determining the output power of the wind driven generator under the intermittent wind speed
Decomposing historical wind speed data with a certain time length into N with the time length of tkA plurality of wind speed intervals, wherein the number of the intermittent wind speed intervals is NP：
Figure FDA0002588853090000017
N is in intermittent wind speed intervalmA number of wind speed segments of intermittent wind speed NW：
Figure FDA0002588853090000021
According to momentum-phyllotoxin theory, dividing a fan blade with the length of D/2 into M phyllotoxins with the width of dr in the direction vertical to the length direction of the fan blade, wherein r is the distance between the phyllotoxins and a rotating shaft of the blade, c is the chord length of the phyllotoxins, and D is the diameter of the rotating track of the outermost end of the blade; at the moment, the chlorophyll with the chord length c and the position r works under the conditions of wind speed v and rotating speed n;
the rotation angular velocity of the phyllanthus element is omega, the inflow wind speed is v, an axial induction factor a and a tangential induction factor a 'are introduced, the horizontal axial velocity of the phyllanthus element is v (1-a), the tangential velocity is omega r (1+ a'), and the axial velocity and the tangential velocity are synthesized into a relative wind speed W; alpha is an attack angle; beta is the phylline pitch angle; the inflow angle phi of the phyllanthus is alpha + beta,
φ＝arctan[v(1-a)/Ωr(1+a′)](9)
under the action of the relative wind speed W, the aerodynamic force applied to the phyllotaxis can be decomposed into a lifting force dF vertical to the direction of the relative wind speed WLAnd a drag dF parallel to the direction of the relative wind speed WD：
Figure FDA0002588853090000022
Figure FDA0002588853090000023
In the formula: rho is air density, and the lift coefficient C of the blade element under different attack angles is inquired according to an airfoil aerodynamic characteristic curve provided by a wind driven generator manufacturerlAnd coefficient of resistance Cd；
Phylline lift force dFLAnd chlorophyll resistance dFDDecomposing along the directions parallel to and vertical to the rotating plane of the fan blade to finally obtain the thrust dF for driving the rotation of the luteinmAnd a thrust dF perpendicular to the plane of rotation of the fan bladest：
Figure FDA0002588853090000024
Figure FDA0002588853090000025
In the formula: ct＝(Clsinφ-Cdcos phi) and Cn＝(Clcosφ+Cdsin phi) are respectively a tangential force coefficient and a normal force coefficient;
Figure FDA0002588853090000026
in the formula: sigma is compactness, namely the volume of the solid matter part of the material accounts for the proportion of the total volume, wherein sigma is Bc/2 pi r, and B is the number of the fan blades;
by assuming initial values of the axial induction factor a and the tangential induction factor a ', the values of the axial induction factor a and the tangential induction factor a' are found according to the following method: 1) setting initial values a of an axial induction factor a and a tangential induction factor achAnd a'ch2) calculating the inflow angle phi of the phyllanthus, 3) calculating the attack angle α, 4) inquiring the lift coefficient C of the phyllanthus according to the determined attack anglelAnd coefficient of resistance Cd(ii) a 5) Calculating the tangential force coefficient CtAnd normal force coefficient Cn(ii) a 6) Calculating a new axial induction factor anewAnd tangential induction factor a'new(ii) a 7) If so: | ach－anew< | and | a'ch－a'newGiven an infinitesimal minimum, then a ═ ach，a'＝a'ch(ii) a 8) If not: | ach－anew< | and | a'ch－a'new< l, such that ach＝anew，a'ch＝a'newThe above process is repeated starting with the calculation of the inflow angle phi of the phyllanthus until | a is satisfiedch－anew< | and | a'ch－a'new< | until;
thrust dF to drive rotation of the phyllotaxismMultiplying the moment arm to calculate the torque dM of the kth leaf elementk，k＝1，2，……M，
Figure FDA0002588853090000031
Multiplying the torque and the angular speed to calculate the wind power dP absorbed by the kth leaf elementk，
Figure FDA0002588853090000032
Adding the wind power absorbed by each of the two folks to obtain the wind power P absorbed by the whole fanblade，
Figure FDA0002588853090000033
In the formula: m is the total number of the phyllanthus of one blade, and B is the number of the fan blades;
according to the power conversion efficiency of the wind driven generator, the output power P of the fan at the wind speed v and the rotating speed n is evaluatedBEMT，
PBEMT(v,n)＝η×Pblade(v,n) (18)
In the formula: eta is the power conversion efficiency of the fan.
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