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Integration of fixed-speed wind Chapter | 14 383

THDV b , and THDV c deteriorated to 9.62%, 9.51%, and 13.72%, respectively,
when the optimal SC is inserted into the system.
On the other hand, optimal STF design is provided regarding the pro-
posed compensator’s problem formulation, except objectives and con-
straints related to voltage unbalance. It has impedance parameters as
X LFab 5 0.200 Ω, X CFab 5 5.052 Ω, X LFbc 5 0.062 Ω, X CFbc 5 5.450 Ω,
X LFca 5 0.079 Ω,and X CFca 5 3.978 Ω. Using the optimal STF design,
THDV Mean is mitigated to 5.15%, and DPF is increased to 98.11%. In addi-
tion, it achieves THDV a , THDV b ,and THDV c values as 3.57%, 5.40%, and
6.50%, respectively. However, voltage unbalance slightly worsens in the
system compensated with the optimal STF design (VUF 5 5.09%) when
compared to the uncompensated system (VUF 5 5.04%). Lastly, it attains
PPL value measured as 54.92%.

14.4.2 Sensitivity analysis of the proposed optimal compensator
design under variation of utility and load-side conditions

The proposed optimal compensator design is determined for the rated load-
ing level and utility voltage with VUF S 5 1.65% and THDV S 5 3.8% condi-
tions in the test system. However, the loading condition and utility voltage
may be changed in the practical systems. Accordingly, to analyze perfor-
mance of the proposed compensator, of which parameters are presented in
Table 14.2, under varying utility voltage and load-side conditions, it is tested
for three cases of the test system as follows:
Case 1: 50% loading level and the utility voltage with VUF S 5 1.65%
and THDV S 5 3.8%
Case 2: 100% loading level and the rated sinusoidal balanced utility
voltages
Case 3: 50% loading level and the rated sinusoidal balanced utility
voltages

For the abovementioned cases the power quality indices and PLL of the
FSWECSs, which are measured before and after the connection of the pro-
posed compensator in the system, are given in Tables 14.3 and 14.4.It is
seen from the same tables that, for all cases, the proposed compensator pro-
vides considerable improvement of THDV Mean , DPF, and PPL. In addition to
that, it achieves to keep THDV a , THDV b , THDV c , and V 1 within their
1
desired ranges.
Lastly, for Cases 1 and 2, VUF is also mitigated by the proposed com-
pensator. However, for Case 3, VUF is almost the same with and without the
compensator. Besides, it should be noted that values of the capacitors should
be readjusted in light loading conditions (Cases 1 and 3) to avoid over com-
pensation. This can be performed by capacitors switching.