الفهرس 
Power System Terminology
Voltage Stability Assessment Considering The Power System Contingencies Using Continuation Power Flow MethodOnly 14 pages are availabe for public view
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Abstract
Voltage stability has been identified as a crucial issue in power system study
and one of the causes that lead to cascading power system blackout in many
parts of the world. This phenomenon has made this subject a very relevant
issue in power system planning and operation.
The first major part of the work in this research describes the effect of single
level contingencies on the static voltage stability of power systems. A
ranking scheme is proposed for screening contingencies based on the Mega
Watt Margin (MWM), which is the distance measured in MW from the base
load operating point to the point of voltage collapse (nose point of P-V
curve). The MWM corresponding to each contingency case is compared with
the MWM of the system at base case. The proposed method is applied on
two different test systems (IEEE-14 and IEEE-30) in order to identify critical
buses, lines and generators in these systems and rank all contingencies
according to their impact on the voltage stability margin. Then Fast Voltage
StabiJity Index (FVSI) was utilized as the measurement to indicate the
voltage stability condition in the maximum loadabi~ity identification at
several load buses. The results of contingency analysis and maximum
loadability for these systems can be used as a guide for controUing and
planning of power systems.
The thesis also presents the fuzzy approach for ranking the contingencies
using Composite-Index. The fuzzy approach uses post-contingent bus
voltage profiles and Line Flow index (L.F) as static voltage collapse
proximity indicator to compute voltage stability margin. Further they are
evaluated usmg fuzzy rules to compute Criticality Index. The Criticality
Index based on severity of bus voltage profiles and line flow index is used to
evaluate contingency ranking and results obtained verified by FVSl to
validate the proposed algorithm.
The second major phase presents the load shedding technique as a corrective
action for avoiding the existence of voltage collapse in power systems. The
load shedding strategy for power systems with location and quantity of load
to be shed is presented. Two methods are used for this purpose. The first
method is based on a mathematical calculation of an indicator of risk of
voltage instability. The second method is based on a fuzzy load shedding
based algorithm that uses a voltage stability indicator for averting voltage
collapse.
A comparison between the two load shedding algorithms have been
presented. In spite of the fact that both schemes facilitate to improve the bus
voltage profile, in addition to enhance voltage stability, still the second
formulation offers an added weight in terms of direct prediction to the
amount of load to be shed at the most appropriate locations and lower value
of sheddable loads. Applications to the standard IEEE 14 and 30 bus test
systems are presented to validate the applicability of the two proposed
methods.