ÇUKUROVA UNIVERSITY INSTITUTE OF NATURAL AND APPLIED ...

3. FUNDAMENTALS OF DVR Mustafa İNCİ
V
V
load
inv
2
= 1/ L
f
C
f
ω f
=
2
2
s + sR / L + 1/ L C s + 2ξ
ω s + ω
(3.11)
f
f
f
f
f
f
2
f
Figure 3.10. Inverter-side filter in DVR
From (3.11), and can be written in (3.12):
ξ
f
=
R
C
f f
2 L
f
,
1
ω
f
=
(3.12)
C L
f
f
The resistance
R
f
is a sum of the series resistance of the filter inductor
and the equivalent resistance of the inverter switches. For a given filter cutoff
frequencyω , infinite combinations of the filter inductance and the filter capacitance
f
L
f
are possible. When the proportion of
C / L is designed large, the filter damping
f
f
coefficient
ξ
f
can be increased, and the disturbance rejection against the load
current may be also increased. However, the inverter current may contain high
ripples which results in larger inverter size. Therefore, the proportion of C / L has
certain limitation (Kim et al., 2004).
Figure 3.10 shows the single line equivalent circuit of inverter side LC filter
in DVR. V
inv
and V
load
represents the voltage on the output of inverter and load. Z
L
f
f
is equivalent impedance in section of load and its equivalent value is
R + jωL
.
L
L
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