Page 405 - Decision Making Applications in Modern Power Systems

Integration of fixed-speed wind Chapter | 14 367

Matlab/Simulink, where the well-known d q model of the SCIG [14] is uti-
lized. Second, a parallel combination of a Steinmetz compensator (SC) and a
single-tuned harmonic filter (STF) is proposed for minimization of the volt-
age unbalance factor (VUF) and average total voltage harmonic distortion
(THDV Mean ) and maximization of PPL and displacement power factor
(DPF). The VUF and individual voltage harmonic distortion and THDV lim-
its, stated in the standards and the desired DPF and rms bus voltage ranges,
are regarded as constraints of the optimal compensator design problem. And
then, for the nonsinusoidal and unbalanced test system, one of the widely
preferred and reliable metaheuristic optimization methods, particle swarm
optimization (PSO) algorithm [34 36], was chosen to employ the proposed
optimal compensator. Optimal STF, which has the problem formulation of
the proposed compensator except the voltage unbalance related objectives
and constraints, and optimal SC, which has the problem formulation of the
proposed compensator except the voltage harmonic distortion related objec-
tives and constraints, were employed using the same optimization algorithm.
Finally, the results of all three compensators were comparatively evaluated
regarding their performances on the PPL improvement, the unbalance and
harmonic distortion mitigation of the point of common coupling (PCC) volt-
age, and DPF correction.

14.2 Problem statement and description
Steinmetz circuit is a compensator that consists of passive elements as induc-
tors and capacitors to mitigate load unbalance and improve power factor in
three-phase systems with unbalanced linear loading and symmetric sinusoidal
supply voltage conditions [37]. For those systems, it has closed form of
design expressions to fully compensate power factor and unbalanced part of
the load current. However, these expressions are not valid for unbalanced or
asymmetrical voltage conditions [31 38]. In addition, an SC is not able to
mitigate harmonic distortion but may amplify it [39,40]. Therefore, in some
studies, it was designed using optimization algorithms to improve loads’
power factor and solve voltage unbalance problem [33]. In view of that, for
mitigation of both unbalance factors and harmonic distortion levels, SCs
should be supplemented by harmonic filters. But, to the best of the authors’
knowledge, no study on the optimal design of both shunt-connected compen-
sators exists in the literature.
Apart from that, a lot of studies have investigated the impacts of various
wind energy systems on power quality performance of DNs, and it was found
that the power quality performance of systems mainly depends on the type
of the wind system. As a result, in this study, the determination of PPL of
IGs in FSWECS is investigated in an unbalanced and nonsinusoidal system,
shown in Fig. 14.1. The system comprises distorted and unbalanced utility
side, which are represented by hth harmonic Thevenin three-phase voltage