Method for Predicting Wind Power Density

• US 20150204922A1
• Filed: 08/06/2013
• Published: 07/23/2015
• Est. Priority Date: 08/07/2012
• Status: Abandoned Application

• Current Assignee: Korea Institute of Energy Research
• Original Assignee: Korea Institute of Energy Research
• Inventors: Kim, Hyun-Goo, Lee, Yung-Seop
• Application Number:
  US14/420,190
• Publication Number:
  US 20150204922A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F05B 2260/821 Parameter estimation or prediction
• CPC Class Codes: G01R 21/133 by using digital technique
• CPC Class Codes: G01W 1/00 Meteorology
• CPC Class Codes: G01W 1/10 Devices for predicting weather conditions computers per se G06; display devices G09
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects

Abstract

Provided is a method for predicting a wind power density. More particularly, provided are a method for predicting a wind power density using a stepwise regression analysis technique capable of estimating a wind power density at any point using a regression analysis technique by a stepwise variable selection method of performing an analysis while adding statistically important terms or removing statistically meaningless terms.

Claims

1. A method for predicting a wind power density using a stepwise regression analysis technique, configured in a form of a program executed by an execution processing means including a computer, comprising:

a variable inputting step (S1) of inputting the wind power density, which is an output variable, and one or more input variables selected among ground roughnesses (r1 to r6), an elevation, a relative elevation difference, a terrain openness, a wide region terrain openness, aspects (a1 to a7), a slope, a relative slope, a mean elevation, a maximum elevation, a minimum elevation, a relative relief, a distance from a coast, and reinterpretation meteorology data;

a stepwise regression analyzing step (S2) of receiving the output variable and the input variables input in the variable inputting step (S1) and performing a regression analysis method by a stepwise variable selection method; and

a multiple regression equation estimating step (S3) of estimating a multiple regression equation having the highest Coefficient of determination (R²) value using regression coefficients calculated in the stepwise regression analyzing step (S2).

2. The method for predicting a wind power density of claim 1, wherein the ground roughnesses (r1 to r6) indicate types of grounds depending on utilization of a land,

the aspects (a1 to a7) indicate directions of inclined surfaces,

the elevation (DEM) indicates an elevation value of a lattice divided from a terrain and having a predetermined size,

the relative elevation difference indicates a comparison value between an elevation of a target region and elevations of surrounding regions,

the mean elevation indicates a mean of elevations of the target region,

the maximum elevation indicates a maximum value of the elevations of the target region,

the minimum elevation indicates a minimum value of the elevations of the target region,

the relative relief indicates a difference between the maximum elevation and the minimum elevation,

the terrain openness indicates a value obtained by measuring how much the target region is not topologically closed when the target region and the surrounding regions are compared with each other,

the wide region terrain openness indicates a value obtained by measuring how much the target region is not topologically closed when the target region is compared with surrounding regions wider than the surrounding regions of the terrain openness,

the slope indicates the most rapid descent surface of the target region,

the relative slope indicates a difference between a first mean slope of the target region and the surrounding regions and a second mean slope of surrounding regions wider than the surrounding regions of the first mean slope,

the distance from the coast indicates linear distances from each of the East Sea, the West Sea, and the South Sea of Korea to the target region, and

the reinterpretation meteorology data correspond to global weather observation data and numerical analysis data re-processed at a spatial resolution of several tens of kilometers or more and distributed for free for a weather forecast, and is any one selected among NCEP/NCAR (National Center for Environmental Prediction-National Center for Atmospheric Research), MERRA (NASA'"'"'s Modern-Era Retrospective Analysis for Research and Applications), ECMWF (European Center for Medium-range Weather Forecasts) of Europe, and JRA-25 (The 25-year Japanese ReAnalysis) of Japan.

3. The method for predicting a wind power density of claim 1, wherein the stepwise regression analyzing step (S2) includes:

a variable transforming step (S21) of performing one or more of variable transformations of the output variable and the input variables input in the variable inputting step (S1) and performing a variable standardization in order to solve a unit difference between the output variable and the input variables;

a normality deciding step (S22) of deciding normality of each of the output variable and the input variables transformed in the variable transforming step (S21);

an output variable inputting step (S23) of inputting any one selected from the output variable input in the variable inputting step (S1) and the transformed output variable decided to have the normality in the normality deciding step (S22);

an input variable inputting step (S24) of inputting input variables obtained by transforming input variables using nominal variables into dummy variables in the variable transforming step (S21) and inputting any one selected among input variables of the same components of input variables that are not the nominal variables input in the variable inputting step (S1) and the transformed input variables decided to have the normality in the normality deciding step (S22) per input variable input in the variable inputting step (S1);

a stepwise regression analysis multiple performing step (S25) of receiving the output variable input in the output variable inputting step (S23) and the input variables input in the input variable inputting step (S24), respectively, and performing the regression analysis method by the stepwise variable selection method once or more; and

an optimal stepwise regression analysis data selecting step (S26) of selecting a regression analysis result by the stepwise variable selection method having the highest Coefficient of determination (R²) value among resultant values of each stepwise regression analysis derived by performing the stepwise regression analysis multiple performing step (S25).

4. The method for predicting a wind power density of claim 3, wherein the variable transformation of the variable transforming step (S21) is any one selected among an original variable, a log transformation, and a square root transformation.

5. The method for predicting a wind power density of claim 1, wherein the multiple regression equation predicting an onshore wind power density of a terrain of South Korea is log(wind power density)=3.79969+(0.05551×

√

{square root over (reinterpretation wind power density)})+(0.04374×

√

{square root over (elevation)})+(−

0.00260×

√

{square root over (distance from coast)})+(−

0.01867×

√

{square root over (minimum elevation)})+(0.09367×

√

{square root over (slope)})+(0.00446×

wide region terrain openness)+(0.02753×

√

{square root over (mean elevation)})+(−

0.00569×

terrain openness)+(0.00075229×

relative elevation)+(−

0.02608×

relative slope)+(0.01661×

√

{square root over (relative relief)})+(−

0.02137×

√

{square root over (maximum elevation)})+(0.24603×

r1)+(0.12644×

r2)+(0.10458×

r3)+(0.12340×

r4)+(0.15980×

r5)+(0.00345×

r6)+(0.05231×

a1)+(0.08932×

a2)+(0.05164×

a3)+(−

0.00168×

a4)+(−

0.03096×

a5)+(−

0.06323×

a6)+(−

0.04673×

a7),

where r1 to r6 are dummy variables of the ground roughnesses and a1 to a7 are dummy variables of the aspects.

6. The method for predicting a wind power density of claim 5, wherein an Coefficient of determination (R²) value of the multiple regression equation predicting the onshore wind power density of the terrain of the South Korea is 0.6267.

7. A method for predicting a wind power density using a main component analysis technique, configured in a form of a program executed by an execution processing means including a computer, comprising:

a variable inputting step (S1) of inputting the wind power density, which is an output variable, dummy variables, which are aspects (a1 to a7) and ground roughnesses (r1 to r6), and one or more input variables selected among an elevation, a relative elevation difference, a terrain openness, a wide region terrain openness, a slope, a relative slope, a mean elevation, a maximum elevation, a minimum elevation, a relative relief, a distance from a coast, and reinterpretation meteorology data;

a main component analyzing step (S20) of analyzing the input variables input in the variable inputting step (S10) as a plurality of main components through a main component analysis using eigenvalues and cumulative values;

a regression analyzing step (S30) of performing a regression analysis by a stepwise variable selection method using the output variable and the dummy variables input in the variable inputting step (S10) and the input variables analyzed as the plurality of main components in the main component analyzing step (S20); and

a multiple regression equation estimating step (S40) of estimating a multiple regression equation having the highest Coefficient of determination (R²) value using regression coefficients calculated in the regression analyzing step (S30).

8. The method for predicting a wind power density of claim 7, wherein

the ground roughnesses (r1 to r6) indicate types of grounds depending on utilization of a land,

the aspects (a1 to a7) indicate directions of inclined surfaces,

the elevation (DEM) indicates an elevation value of a lattice divided from a terrain and having a predetermined size,

the relative elevation difference indicates a comparison value between an elevation of a target region and elevations of surrounding regions,

the mean elevation indicates a mean of elevations of the target region,

the maximum elevation indicates a maximum value of the elevations of the target region,

the minimum elevation indicates a minimum value of the elevations of the target region,

the relative relief indicates a difference between the maximum elevation and the minimum elevation,

the terrain openness indicates a value obtained by measuring how much the target region is not topologically closed when the target region and the surrounding regions are compared with each other,

the wide region terrain openness indicates a value obtained by measuring how much the target region is not topologically closed when the target region is compared with surrounding regions wider than the surrounding regions of the terrain openness,

the slope indicates the most rapid descent surface of the target region,

the relative slope indicates a difference between a first mean slope of the target region and the surrounding regions and a second mean slope of surrounding regions wider than the surrounding regions of the first mean slope,

the distance from the coast indicates linear distances from each of the East Sea, the West Sea, and the South Sea of Korea to the target region, and

the reinterpretation meteorology data correspond to global weather observation data and numerical analysis data re-processed at a spatial resolution of several tens of kilometers or more and distributed for free for a weather forecast, and is any one selected among NCEP/NCAR (National Center for Environmental Prediction-National Center for Atmospheric Research), MERRA (NASA'"'"'s Modern-Era Retrospective Analysis for Research and Applications), ECMWF (European Center for Medium-range Weather Forecasts) of Europe, and JRA-25 (The 25-year Japanese ReAnalysis) of Japan.

9. The method for predicting a wind power density of claim 7, wherein the regression analyzing step (S30) includes:

a variable selecting step (S31) of selecting one or more main component of which the eigenvalue is a pre-input first predetermined value or more or the cumulative value is smaller than a pre-input second predetermined value among the plurality of main components analyzed in the main component analyzing step (S20);

a variable transforming step (S32) of performing variable transformations on the output variable input in the variable inputting step (S10);

a normality deciding step (S33) of deciding normality of the output variable transformed in the variable transforming step (S32);

an output variable inputting step (S34) of inputting any one selected from the output variable input in the variable inputting step (S10) and the standardized output variable decided to have the normality in the normality deciding step (S33);

an input variable inputting step (S35) of inputting one or more selected among the input variables configuring the main components selected in the variable selecting step (S31); and

a regression analysis multiple performing step (S36) of receiving the output variable input in the output variable inputting step (S34), the input variable input in the input variable inputting step (S35), and the dummy variables input in the variable inputting step (S10), respectively, and performing the regression analysis by the stepwise variable selection method once or more.

10. The method for predicting a wind power density of claim 9, wherein the variable transformation of the variable transforming step (S32) is any one selected from a log transformation and a square root transformation.

11. The method for predicting a wind power density of claim 7, wherein the main component multiple regression equation predicting an onshore wind power density of a terrain of South Korea is log(wind power density)=4.87579+(0.11583×

first main component input variable)+(0.06275×

second main component input variable)+(0.13119×

third main component input variable)+(−

0.17187×

fourth main component input variable)+(0.40142×

r1)+(0.24001×

r2)+(0.20801×

r3)+(0.25655×

r4)+(0.26863×

r5)+(0.08658×

r6)+(−

0.11419×

a1)+(−

0.05256×

a2)+(−

0.06328×

a3)+(−

0.09685×

a4)+(−

0.10314×

a5)+(−

0.11079×

a6)+(−

0.06658×

a7),

where r1 to r6 are dummy variables of the ground roughnesses and a1 to a7 are dummy variables of the aspects.

12. The method for predicting a wind power density of claim 11, wherein an Coefficient of determination (R²) value of the main component regression equation predicting the onshore wind power density of the terrain of the South Korea is 0.5838.

13. A method for predicting a wind power density using a neural network analysis technique, configured in a form of a program executed by an execution processing means including a computer, comprising:

a variable inputting step (S100) of inputting a wind power density, which is an output variable, and one or more input variables selected among ground roughnesses (r1 to r6), an elevation, a relative elevation difference, a terrain openness, a wide region terrain openness, aspects (a1 to a7), a slope, a relative slope, a mean elevation, a maximum elevation, a minimum elevation, a relative relief, a distance from a coast, and reinterpretation meteorology data;

a neural network analyzing step (S200) of performing a neural network analysis using the output variable input in the variable inputting step (S100) and the input variables selected through a stepwise variable selection method; and

a neural network model estimating step (S300) of estimating a neural network analysis model through a coefficient of correlation value using the number of hidden nodes depending on a root mean square error (RMSE) value calculated in the neural network analyzing step (S200).

14. The method for predicting a wind power density of claim 13, wherein the ground roughnesses (r1 to r6) of the variable inputting step (S100) indicate types of grounds depending on utilization of a land,

the aspects (a1 to a7) indicate directions of inclined surfaces, and

the ground roughnesses and the aspects are transformed into dummy variables.

15. The method for predicting a wind power density of claim 13,

wherein the neural network analyzing step (S200) includes a first analyzing step (S210) of performing the neural network analysis using the output variable log-transformed and the input variable using the stepwise variable selection method.

16. The method for predicting a wind power density of claim 13, wherein the neural network analyzing step (S200) includes a second analyzing step (S220) of performing the neural network analysis using the output variable in an original data form and the input variable using the stepwise variable selection method.

17. The method for predicting a wind power density of claim 13,

wherein the neural network analyzing step (S200) includes a third analyzing step (S230) of performing the neural network analysis using the output variable square-root-transformed and the input variable using the stepwise variable selection method.

18. The method for predicting a wind power density of claim 13,

wherein the neural network analyzing step (S200) includes a fourth analyzing step (S240) of performing the neural network analysis using the output variable log-transformed and the input variable using the stepwise variable selection method, and

the elevation, the slope, the distance from the coast, the maximum elevation, the mean elevation, the minimum elevation, the relative relief, and the reinterpretation meteorology data are square-root-transformed.

19. The method for predicting a wind power density of claim 13,

wherein the neural network analyzing step (S200) includes a fifth analyzing step (S250) of performing the neural network analysis using the output variable square-root-transformed and the input variable using the stepwise variable selection method, and

the elevation, the slope, the distance from the coast, the maximum elevation, the mean elevation, the minimum elevation, the relative relief, and the reinterpretation meteorology data are square-root-transformed.