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UBC Theses and Dissertations

Dynamic and static voltage stability analysis of distribution systems in the presence of distributed generation Nikpour, Nafiseh


In this research, static and dynamic voltage stability of distribution systems are studied, with a focus on systems with distributed generation. A voltage dependent model is used for distribution loads, which converts the static voltage stability analysis into a linear problem and allows for real-time solutions. For static voltage stability studies, an index is defined that contains critical data on load and system characteristics. The static voltage behavior of distribution systems, either with or without DG, is studied by analyzing the P-V curves and the proposed voltage stability index at each node of the system. Besides identifying the weakest buses of the system in terms of voltage profile and voltage stability, this approach also allows the extension of the classical voltage stability solution to the increasingly important case of distributed generation placement - where the system is more likely to face voltage transients. The method can also be used in resilience studies. For dynamic voltage stability studies, the Shifted Frequency Analysis (SFA) method is used to evaluate the system transients and its dynamic voltage behavior during and right after being subjected to a change or disturbance in the system. Various scenarios are discussed, including scenarios in which the voltage transients due to DG cause voltage instabilities in the system. SFA and EMTP solutions are compared with each other, and with the static analysis results. SFA and EMTP results also verify the validity of the proposed voltage stability index. The proposed voltage assessment method facilitates real-time decision making, topological reconfiguration to strengthen voltage stability robustness, and DG placement. Different scenarios and distribution system topologies such as looped or meshed distribution systems, as well as microgrids and autonomous/islanded energy grids can be included in the solution.

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