Analysis and Planning of Power Transmission System Subject to Uncertainties in the Grid

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Virginia Tech

Power transmission systems frequently experience new power flow pattern due to several factors that increase uncertainties in the system. For instance, load shape uncertainty, uncertainty due to penetration of renewable sources, changing standards, and energy de-regulation threaten the reliability and security of power transmission systems. This demands for more rigorous analysis and planning of power transmission systems.

Stability issues in power transmission system are more pronounced with the penetration of utility-scale Photo-Voltaic (PV) sources. Synchronous generators provide inertia that helps in damping oscillations that arise due to fluctuations in the power system. Therefore, as PV generators replace the conventional synchronous generators, power transmission systems become vulnerable to these abnormalities. In this thesis, we study the effect of reduced inertia due to the penetration of utility-scale PV on the transient stability of power transmissions systems. In addition, the effect of increased PV penetration level in the system during normal operating condition is also analyzed. The later study illustrates that the PV penetration level and the placement of PV sources play crucial roles in determining the stability of power transmission systems.

Given increasing uncertainties in power transmission systems, there is a need to seek an alternative to deterministic planning approach because it inherently lacks capability to cover all the uncertainties. One practical alternative is the probabilistic planning approach. In probabilistic planning approach, an analysis is made with a wide variety of scenarios by considering the probability of occurrence of each scenario and the probability of contingencies. Then, the severity of the contingencies risk associated with each planning practice is calculated. However, due to the lack of techniques and tools to select wide varieties of scenarios along with their probability of occurrence, the probabilistic transmission planning approach has not been implemented in real-world power transmission systems. This thesis presents a technique that can select wide varieties of scenarios along with their probability of occurrence to facilitate probabilistic planning in Electricity Reliability Council of Texas (ERCOT) systems.

stability studies, probabilistic planning