Civil Engineering Reference
In-Depth Information
FIGURE 11-10
Buck-boost converter circuit (general DC to DC converter for pv systems).
FIGURE 11-11
Buck-boost converter output to input ratio versus duty ratio.
other hand, the buck converter presented in the preceding section can only
step down the input voltage. Combining the two converters in cascade,
therefore, give a buck-boost converter, which can step down or step up the
input voltage. A modified buck-boost converter often used for this purpose
is shown in
Figure 11-10
.
The voltage relation is obtained by cascading the
buck and boost converter voltage relations. That is as follows:
VD
D
⋅
V
=
in
(11-11)
out
1
−
Equation 11-11 for the buck-boost converter shows that the output voltage
can be higher or lower than the input voltage depending on the duty ratio D
(
Figure 11-11
)
.
In addition to its use in the battery charging and discharging, the buck-
boost circuit is capable of four-quadrant operation with the DC machine
