ÇUKUROVA UNIVERSITY INSTITUTE OF NATURAL AND APPLIED ...

4. MODELING OF PROPOSED DVR Mustafa İNCİ
The voltage across L1 is Vo, resulting in a linearly decreasing current in L1.
The change in current while both switches are open is
∆I
∆t
L1
∆I
L1
V
= = −
T / 2 − DT L
O
1
(4.17)
State 3, Second on-period, T3: A second on-period similar to the first is initiated
when switches, S3 and S4, are turned on. Reflected inductor current flows from input
capacitor, C1, through switch, S3, transformer, T1, (in opposite direction compared
to first on-period) diode, D3, and inductor, L1, to the output. Current returns to input
through diode, D4, and switch, S4. The period ends when switches, S3 and S4, are
turned off again. Period time is equal to the first on-period, (Nymand et al.,
2010).
State 4, Second off-period, T4: Finally, a second off-period starts when switches,
S3 and S4, are turned off. All primary switches are off. Inductor current, iL1, is freewheeling
through the two parallel branches, D1-D4 and D3-D2, to output. Inductor
current is discharging. Transformer magnetizing current circulates in the transformer
secondary winding (in opposite direction to first off-period) and the diodes, D1-D3
and/or D2-D4. The period ends when switches, S1 and S2, are turned on. Period time
is equal to the first off-period time, T
4
= T 2
. Duration of the off-period is (Nymand et
al., 2010):
Since the net change in inductor current over one period must be zero for
steady-state operation,
( ∆ ) + ( ∆I
) 0
I (4.18)
L, closed L,
open
=
1
L
1
⎛ N
S
⎞ VO
⎜ Vin
−VO
⎟DT
+ ( T / 2 − DT ) = 0
(4.19)
⎝ N
P ⎠ L1
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