Civil and Architectural Engineering
Electrical and Computer Engineering
Department-College of Engineering-Sultan Qaboos University
Voltage Stability Assessment of A micro-Grid
Case Study: Khasab Power System in Oman
Yousuf AL Jabri
Abstract
Voltage stability analysis of power system is a major requirement, particularly in the planning
phase of the development or expansion of a power network. Micro-grid is normally composed
of relatively small-distributed generators supplying islanded distribution network. Although a
micro-grid may not be a complex interconnected power system similar to a transmission
network, but it has some characteristics that makes it undergo stability problems when it is
exposed to disturbances. In this research, a study is being done to expand the power network of
the area of Musandam in the Sultanate of Oman. Since, this area is not connected to the main
interconnected system of Oman, it operates as a microgrid. The ultimate goal of this study is to
investigate the voltage stability of Musandam micro-grid during the expansion of the network.
In order to perform the voltage stability analysis, modal analysis as well as PV and QV curves
were evaluated based on load flow for selected scenarios. A MATLAB m-file has been
developed to carry out the static voltage stability analysis along with ETAP software. It was
found that MOD bus is the weakest bus in Khasab micro-grid that is participating in the voltage
instability more than others.
The dynamic voltage stability analysis has been performed by using time domain simulation
with PSAT software. In addition, since normally the micro-grid consists of more than one type
of source, then, Doubly Fed Induction Generator (DFIG) wind turbine was added to Musandam
micro grid for the purpose of testing its effect in the voltage stability. It was shown that DFIG
wind turbine generator improves the voltage profile and the voltage stability as well as the
frequency of the micro-grid under most types of disturbances. Under three phase short circuit, it
was found that the system was more stable in the lagging power factor case of the DFIG. When
the fault occurred at the terminals of the DFIG, it was found that the system stability was more
effected compare to the situation when the fault occurred at synchronous generators bus.