Method and apparatus for monitoring wind turbulence intensity
View Patent ↗A method of determining an estimate of the de-trended turbulence intensity TI in a proposed site for a wind farm including the steps of measuring the wind speed at a predetermined sampling frequency f s during a number of time periods p z ; calculating in each time interval p z wind speed statistical parameters V mean , σ v and a wind speed trend parameter k in real time for each new wind speed measure x j as a function of the values of said parameters V mean , σ v , k for the prior wind speed measure x j-1 and the new wind speed measure x j ; storing the parameters V mean , σ v , k obtained at the end of each time interval p z ; determining the de-trended turbulence intensity TI in said proposed site using said stored parameters V mean , σ v , k. The invention also refers to an apparatus for acquiring the data needed for the calculation of the de-trended turbulence intensity TI.
1. A method of determining an estimate of the de-trended turbulence intensity TI in a proposed site for a wind farm including the steps of:
measuring the wind speed at a predetermined sampling frequency f s during a number of time periods p z ;
calculating in each time interval p z wind speed statistical parameters V mean , σ v and a wind speed trend parameter k in real time for each new wind speed measure x j as a function of the values of said parameters V mean , σ v , k for the prior wind speed measure x j-1 and the new wind speed measure x j ;
storing the parameters V mean , σ v , k obtained at the end of each time interval p z ;
determining the de-trended turbulence intensity TI in said proposed site using said stored parameters V mean , σ v , k.
2. The method of claim 1 , wherein k is calculated by means of the formula k=C·H n , where
C
=
12
f
s
T
n
4
-
n
2
and H n is obtained by accumulation of the Hj values in real time from the previous H j-1 according to the formula:
H
j
=
j
(
x
j
j
+
B
j
-
1
)
-
j
(
j
+
1
)
2
(
x
j
+
S
xj
-
1
)
.
3. The method of claim 1 , wherein the step of determining the de-trended turbulence intensity TI includes the step of calculating the variance of the trending as
σ
trend
2
=
k
2
12
.
4. An apparatus for acquiring relevant data for determining an estimate of the de-trended turbulence intensity TI in a proposed site for a wind farm, the apparatus comprising:
sensor means that provides wind speed measures x j at a predetermined sampling frequency f s ;
processor means that calculates for a number of time periods p z wind speed statistical parameters V mean , σ v and a wind speed trend parameter k in real time for each new wind speed measure x j as a function of the values of said parameters V mean , σ v , k for the prior wind speed measure x j-1 and the new wind speed measure x j ;
a memory that stores said parameters V mean , σ v k for said time periods p z .
5. The apparatus of claim 4 , wherein k is calculated by means of the formula k=C·H n , where
C
=
12
f
s
T
n
4
-
n
2
and H n is obtained by accumulation of the Hj values in real time from the previous H j-1 according to the formula:
H
j
=
j
(
x
j
j
+
B
j
-
1
)
-
j
(
j
+
1
)
2
(
x
j
+
S
xj
-
1
)
.