Voltage collapse contingency screening and power grid vulnerabilities

This dissertation mainly focuses on developing novel and fast techniques for contingency ranking based on voltage collapse. Techniques of ranking contingencies have been utilized finally to find out the vulnerability of electric grid to malicious attack. Contingency ranking has been done by estimating the post-contingency voltage collapse point (CP), given a power system operating point, a load demand forecast and a generation dispatch. The distinguished features are ability to directly estimate the post-contingency CP, consideration of breaking point, capability to handle a single event or multiple event contingency, ability to deal with an is-landing contingency, consideration of VAR limit of generators, and ability to rank contingencies quickly and accurately for a very large power system.; The proposed method has been tested for all 6689 single branch outages of a 3493 bus system, as well as for 1251 multi-terminal contingencies of a 19140 bus system for two possible transfer cases with promising results. The proposed method also has been tested for 97 generator contingencies of a 19140-bus system. Results obtained from the new algorithm were compared with results obtained from full continuation power flow and they show that the proposed algorithm is very accurate, robust, fast and efficient.; A ranking algorithm was also developed based on a severity index with the introduction of a contingency scope index (CSI) and a load loss index (LLI). The severity index depends upon "distance to collapse ", "CSI" and "LLI". The proposed ranking algorithm was tested for all 6689 single branch outages of a 3493 bus system for two possible transfer cases.; The vulnerability of an electric grid has been assessed by identifying a set of critical contingencies. The set of critical facilities could be attacked by terrorists to cause an immediate collapse. A new search technique has been developed based on a dot product of post-contingency eigenvector. The proposed algorithm has been tested on a 3493-bus system and results show that there are several combinations of contingencies that could bring down the electric grid and cause a widespread blackout. Results are also presented by using a conventional search technique. Combinations of contingencies have been considered up to nine simultaneous contingencies.; Improvements have been done in CMTRACE, a continuation based power flow solver, to identify breaking and bifurcation point in a more efficient and accurate way. Modeling of phase shifter and three-winding transformers has been done to match the actual device operation and to make CMTRACE more flexible in handling these devices.