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This dissertation presents a new alternative type of object-oriented load-flow called Segflow. Segment objects are used to support the modeling of individual types of power system equipment. Current and voltage trace techniques are used by Segflow to bind Segment models in support of Kirchoff’s laws. Affiliation objects and the Target Voltage method are used to bring the solution of the Segflow model to the solution of the power system network. An example for modeling a simple transformer is given along with the solution results for a collection of common power system models. ‘ Analysis of the Target Voltage method and simulation results show that Segflow is capable of consistently solving the nonlinear load-flow problem. The object-oriented layout of Segflow provides very distinct modeling advantages. Power system modeling is from the perspective of each equipment’s model. Rather than force all equipment models into large sets of equations to be solved simultaneously by an equation solver, Segflow allows component models to remain intact and independent as Segment objects. Each Segment has a one-to-one correspondence with some piece of equipment in the respective power system which is maintained in the system solution. The behavior of a Segment can be evaluated throughout the load-flow process. An important feature of Segflow is the object-oriented design enabling new equipment models to be added into the Segflow environment as autonomous objects. New models are created from the Segment class and their inputs and outputs are always relative to the same Segment attributes. Because all Segment objects are derived from a Segment modeling class and all Segments are treated the same by Segflow, many types and varieties of power system equipment models can be easily created. A Segflow application is a collection of interacting objects whose interactions lead to a load-flow solution. Segflow is an interesting alternative to classical approaches for solving the load-flow problem with large sets of simultaneous nonlinear equations. It also adds new aspects to the application of object-oriented design in load-flow analysis. / Ph. D.

Security analysis of a power system requires a process called contingency analysis that analyzes results from all possible single contingencies (i.e. outages) in the system. The process of contingency analysis requires the definition of a parameter that is used to monitor a certain aspect of the system, which is called a performance index. The performance index definitions used traditionally have been highly nonlinear, and the results have not accurately predicted the outcome of the performance index in some cases. These incorrect results are referred to as misrankings since the contingency results are usually placed in order of severity so that the most severe cases are evident. This thesis considers a new definition of contingency ranking using a more linearized definition of the performance index. The construction of both the new, proposed definition and the classic definition both consider the current loading of circuits in the system as compared to their rated values. Specifically, the parameter measured by the proposed definition measures the difference, while the more nonlinear definition uses a ratio of the two quantities, which is then raised to a higher power. A small, four bus test system is used to demonstrate the benefits of the new, more linearized definition. The average percent error for all single line contingencies of the system decreased by over 9.5% using the proposed definition as compared to the previous one. This decrease in error allows this performance index to monitor a similar parameter (comparing current loading and current rating of the lines) and achieve a higher degree of accuracy. Further linearization of this proposed definition also shows a reduction in the average percent error by an additional 22% so that when compared to the original, highly nonlinear definition, the average error is reduced by almost 30%. By linearizing the definition of the performance index, the results are more accurate and misrankings are less likely to occur from the security analysis process.

Thesis (Ph. D.)--Ohio State University, 2007. / Full text release at OhioLINK's ETD Center delayed at author's request