
Filtering Techniques for Power Quality Improvement 38-21
high cost and complexity of control, interest in UPQC is growing due to its superior performance.
It can compensate signicant power quality issues, such as, voltage harmonics, voltage sag, voltage
swell, voltage unbalance, voltage icker, current harmonics, load reactive power, current unbalance,
and neutral current. A single-phase voltage-fed and current-fed UPQC are shown in Figures 38.33
and 38.34. Figures 38.35 and 38.36 show the schematic of a three-phase three-wire and a three-phase
four-wire UPQC.
1
2
Single-phase voltage-source type
of nonlinear load
Single-phase
ac mains
e
s
L
s
i
s
V
c
C