HSP NTG-3000, Руководство по эксплуатации

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NTG-3000 Operating Instructions Version 2.11
Page 12 of 18
12 Filter
For the filtered compensated frequency (f
comp filtered
) and the filtered effective power (P
filtered
)
there are three filters of second order integrated.
The layout of filter structures will be described in the following chapters.
12.1 Layout of filter structures
* depending to the filter parameters, e.g. Butterworth (see section 12.3)
12.2 Algorithm of second order filter
y = b
2
∙ x + b
1
∙ x
k−1
+ b
0
∙ x
k−2
− a
1
∙ y
k−1
− a
0
∙ y
k−2
x
filter Input
y filter Output
Z
-1
clock delay
x
k−1
value at filter input with delay of one clock
x
k−2
value at filter input with delay of two clocks
y
k−1
value at filter output with delay of one clock
y
k−2
value at filter output with delay of two clocks
b
0
...b
2
a
0
...a
1
filter parameters
+
+
+
b
2
b
1
b
0
Z
-1
Z
-1
x
Z
-1
Z
-1
y
-a
0
-a
1
2nd order filter
2nd order filter 2nd order filter
2nd order filter 2nd order filter
2nd order filter
f
comp filtered
P P
filtered
f
comp
1st filter level * 2nd filter level *
3rd filter level
notch filter