Page 168 - Power Quality in Electrical Systems

150 Chapter Ten

series converter is activated; it injects the missing component of the
source voltage waveform. In the circuit shown in Figure 10-3b, the energy
comes from the shunt transformer on the load side, not from the dc-link
capacitors. However, the line current increases to maintain the power
to the load constant. As a result, the time duration of the compensation
does not depend upon the energy stored in the capacitors but on the
short-time thermal capabilities of the components.
Figure 10.4 shows an experimental result of dynamic voltage com-
pensation for a single-phase voltage sag with a depth of 50 percent
using the circuit of Figure 10.3b [10.3]. The voltage sag lasts 110 ms. The
waveform v is the series transformer voltage, which is added to the
C
source voltage v to produce the load voltage v .
L
S

200
100
u [V] 0
S
–100
–200
200
100
u [V] 0
L
–100
–200
100
50
[V]
u C 0
–50
–100
50
25
[A]
i S 0
25
–50
300
280
260
[V]
u dc
240
220
200
10 ms
Figure 10.4 Experimental result under a single-phase source voltage
sag of 50% for 110 ms source voltage; v L load voltage; v C cor-
rection voltage; i s source current; v dC capacitor voltage [10.3].
[© 2005, IEEE, reprinted with permission]