ENHANCE POWER -QUALITY THROUGH VERSATILE CONTROL SYSTEM FOR A DYNAMIC VOLTAGE RESTORER
Abstract
This paper presents a control system based on a repetitive controller to compensate
for key power-quality disturbances, namely voltage sags, harmonic voltages, and
voltage imbalances, using a dynamic voltage restorer (DVR). The control scheme
deals with all three disturbances simultaneously within a bandwidth. The control
structure is quite simple and yet very robust; it contains a feed forward term to
improve the transient response and a feedback term to enable zero error in steady
state. The well- developed graphical facilities available in PSCAD/EMTDC are used
to carry out all modeling aspects of the repetitive controller and test system.
Simulation results show that the control approach performs very effectively and
yields excellent voltage regulation. Therefore, in this paper, a new simplified control
algorithm which utilizes the strengths of synchronous rotating frame (SRF) and
phase-locked loop (PLL) concepts, is proposed to better manage operation of DVR.
The DVR system is modelled and simulated by using MATLAB/Simulink platform.
Performance of the newly proposed algorithm for DVR is tested in three-phase system
with voltage sags, swells, harmonics and unbalances conditions. From the findings, it
can be concluded that the proposed algorithm for DVR which installed in a three
phase power distribution system effectively mitigated the voltage sags, swells and
unbalances conditions and, for harmonics condition, it is found to be able to minimize
and contain the harmonic contents within the acceptable level.
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