
Filtering Techniques for Power Quality Improvement 38-31
In order to simplify the ltering of the load current i
Lh
, the fundamental component i
Lfa
is transformed
i
nto the dc component. Multiplying both sides of Equation 38.19 by sin θ
s
,
i
i i
i h
L s s
L L
s s Lh s h
θ θ φ θ φ θ θ φ
(
)
= − −
(
)
+ −sin cos cos sin sin
ˆ ˆ
ˆ
1
1
1
1
2 2
2
((
)
=
∞
∑
h 2
(38.23)
is equation shows the presence of a dc component and the ac components of which minimal frequency
is equal to twice the frequency network (120 Hz). A low-pass lter, with a relatively low cut-o frequency is
used to prevent the high-frequency component. However, it is indispensable to respect a good compromise ...