![]() | Only 14 pages are availabe for public view |
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. |