Download Voltage Stability Assessment and Enhancement of a Large Power

School of Electrical, Computer and Energy Engineering
PhD Final Oral Defense
VOLTAGE STABILITY ASSESSMENT AND ENHANCEMENT OF A LARGE
POWER SYSTEM USING STATIC AND DYNAMIC
APPROACHES
by
Bishnu Prasad Sapkota
January 13, 2010
Time – (9:00 AM – 11:00 AM)
Room- ERC 490
Committee:
Dr. Vijay Vittal (chair)
Dr. Gerald Heydt
Dr. Daniel Tylavsky
Prof. Richard Farmer
Dr. Jennie Si
Abstract
Voltage instability initiated by induction motor dynamics has been an
important issue in power system operation. The voltage instability in a power system
having significant induction motor loads can be manifested either in the form of delayed
voltage recovery or in the form of voltage collapse. When a power system is subjected to
a disturbance in the presence of considerable induction motor loads, static analysis alone
is not sufficient to determine the control actions required to restore the system voltages.
Time domain simulations are required to obtain useful indications to deal with controls
depending on system time evolution. The present study focuses on the application of a
mix of various static and dynamic approaches to analyze and enhance the voltage
stability of power systems. Static analysis is used mainly to select critical contingencies
based on voltage stability margins whereas the dynamic analysis is used to find the
mechanism of voltage collapse. The propagation of impact of faults from the transmission
level to the distribution level is observed to examine the mechanism of voltage collapse
and to determine the corrective action to mitigate the detrimental effect of the voltage
collapse. The impact of induction motors on voltage stability is examined using trajectory
sensitivity analysis. A novel technique based on a trajectory sensitivity index that is
developed is proposed to find the suitable location for dynamic reactive power support. In
this regard, the viability of FACTs controllers such as SVC and STATCOM is examined.
Accordingly, the latter is found more effective for providing corrective action against
voltage collapse.