| dc.description.abstract | It is widely known that solar Coronal Mass Ejections (CMEs) emanating from the sun’s surface
have the capacity to disturb the earth’s magnetic field. This leads to an event called a Geomagnetic
Disturbance (GMD). The varying magnetic field caused due to this disturbance could result in an
electric field over the earth’s surface. This electric field has the potential to eventually cause quasidc
currents called Geomagnetically Induced Currents (GICs) circulating through the grid. When
these quasi-dc currents flow through high-voltage transformers, they produce additional reactive
power losses in them.
Myriad research efforts have been taken to address the issue of circulating GICs from different
perspectives. Improved GIC modelling, electric field estimation, GIC monitoring, stability
analysis, and voltage study to list a few. But, none of the efforts have addressed the GMD problem
from a Power System State Estimator (PSSE) perspective. PSSE is a tool employed by utilities in
Energy Management Systems (EMS) and hence, is an important tool for making decisions pertaining
to the grid. The additional reactive losses caused by GICs, being unaccounted for, could result
in large deviations in the system states estimated. Therefore, my research is motivated by the lack
of an accurate PSSE available for the utilities to be used during GMD events. A GIC-inclusive
PSSE could greatly assist the utilities and system operators in taking operational decisions and
hence, help in better management of the grid.
The power grid is modelled as a dc system for GIC analysis and study. This is because GICs
are quasi-dc and hence the system can be modelled as dc. Various studies that need to be carried
out for GMD analysis require computation of transformer neutral GICs as well as other system
parameters. A considerable portion of these studies are usually performed on MATLABR . But,
there is no tool or package available on MATLAB that can provide easy and seamless calculations
of these necessary parameters. One direct example, relevant to my thesis, of an application of such
a tool, would be in the modified PSSE itself. The modified PSSE would require the calculation of
transformer neutral GICs. Therefore, another research motivation is the construction of an efficient tool for the calculation of such system values that could be utilized for various GMD studies.
For my research, the accuracy of the traditional state estimator was checked for GMD events.
This state estimator failed to produce accurate results during the GMD events and accumulated
noticeable results. To solve this problem, the GIC-Inclusive state estimator was constructed using
the GMD tool, MATGMD. This modified state estimator was successful in obtaining accurate
results for the EPRI 20 bus case and the UIUC bus case with the error in the voltage magnitude
states in the range of 10^-5 and for the neutral current states in the range of 10^-4. The results for
the EPRI 20 bus case using the GIC-Inclusive state estimator have been depicted and comparisons
with the traditional state estimator have been made. The GIC-Inclusive state estimator, though
computationally heavy, is very effective and the advantages of its applications outweighs the ease
of using the traditional state estimator during GMD events. | en |
