Improved single-phase line-interactive UPS
Bong-Hwan Kwon; Jin-Ha Choi; Tae-Won Kim
Industrial Electronics, IEEE Transactions on
Volume 48, Issue 4, Aug 2001 Page(s):804 - 811
Digital Object Identifier 10.1109/41.937413
Summary:An improved single-phase line-interactive uninterruptible power
supply (UPS) is proposed for low-power applications with low cost. The
proposed UPS is comprised of two push-pull converters based on a
low-voltage battery for reduced cost: one in series with the input and
the other in parallel with the load. In the presence of input power, the
UPS acts as an output voltage regulator and at the same time as an
active filter while charging the battery. In case of loss of input
power, the UPS supplies a regulated sinusoidal voltage to the load,
drawing power from the battery. The series converter compensates only a
small percentage of the input voltage carrying the input current and,
therefore, a reduced rating is made. The parallel converter always
supplies a nominal voltage and makes a seamless transition to backup
mode. In the voltage determination of the parallel converter, the
nominal voltage is derived using the feedback linearization concept and
then a perturbed voltage is determined for the reactive power control or
output voltage regulation. Experimental results obtained from a 1-kVA
prototype are discussed
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