Development, Modeling, and Applications of PMUs

HyoJong Lee

Integration of digital devices such as phasor measurement units (PMUs) at substations have been on the rise to provide efficiency, flexibility, reliability and economic benefits in power system operation and control. However, these devices may also bring additional challenges caused by inherent cyber vulnerabilities and bad data problems that in turn lead to the malfunction of these devices.% or incorrect decisions by the operator. These vulnerabilities can lead to system instability, inefficient, and power outages. The research work in this dissertation suggests possible solutions to these problems using the following approaches: improving phasor measurement quality, validating PMU performance, and decentralizing monitoring and control applications. Most commercial PMUs are designed with a Discrete Fourier Transform-based algorithm that can generate attenuated phasors with errors during dynamic system conditions. As a solution to this problem, the Wavelet Transform (WT)-based phasor estimation has been proposed for better accuracy during dynamic conditions. The developed WT-PMU has two different mother functions specifically designed for noisy and harmonics environment. A switching algorithm has also been developed to select the most suitable phasor estimation based on the system operating conditions. The developed PMU has been tested using a testbed in the lab following IEEE test suite specifications; the testbed is extended for remote testing using Erkios, a data delivery and management platform. The second part of the research presented in this dissertation relates to PMU-based model validation. Offline simulation tools are commonly used to simulate large power systems. There are mismatches between field measurements from PMUs and offline simulation results even if accurate power system models are used because of the internal features of PMUs. A PMU emulator for power system dynamic simulators has been developed to compensate the phasors of the dynamic simulator to match the response from PMUs. Finally, a decentralized voltage stability application using a distributed computing platform has been developed. The Laplacian-based Thevenin parameter estimation has been developed to mitigate errors in commonly used Thevenin-based voltage stability indices using PMUs. Simulation results indicate superior performance of adaptive PMU, PMU emulator, and Laplacian-based voltage stability, as well as satisfactory performance of the decentralized implementation of the voltage stability.

Development, Modeling, and Applications of PMUs

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