Robust GPS-Based Timing for Phasor Measurement Units Based on Single-Receiver and Multi-Receiver Position-Information-Aided Vector Tracking

Chou, D.

M.S. Thesis, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, May 2015.

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In recent years there has been a major push by the power industry to utilize phasor measurement units (PMUs) for wide area monitoring and control. PMUs are considered to be one of the most critical technologies for the future and modernization of the power grid. This technology produces time-stamped voltage and current phasor measurements, allowing measurements from any point in the power infrastructure to be synchronized. Widely regarded as one of the most vital devices in monitoring and control for the future of power systems, PMUs rely on the Global Positioning System (GPS) to provide the absolute time reference necessary to synchronize phasor mea-surements. The security and reliability of PMUs are essential to the future of the power grid and so in this work we aim to provide robust GPS timing for PMUs.

Since power systems are considered part of the civil sector, PMUs must utilize the civil GPS signals to obtain the time reference. However, the low received signal strength and unencrypted nature of the civil GPS signal leaves PMU reliability susceptible to both non-malicious and malicious interference. Most notably, jamming and spoofing attacks on PMU GPS receivers can pose a risk to the position, velocity, and timing (PVT) solutions.

Our goals are to provide robust GPS time transfer for PMUs and to rapidly detect malicious spoofing attacks. We achieve these goals by leveraging the inherent properties of PMU GPS receivers. We propose and implement the position-information-aided (PIA) vector tracking loop and the multi-receiver PIA vector tracking loop. To evaluate the effectiveness of the algorithms presented in this thesis, we also conduct field experiments which showed improve tracking capabilities and continued operation through various at-tacks of both algorithms. Our experiments show that the proposed PIA and multi-receiver PIA vector tracking approaches 1) improve the robustness of GPS receivers used in PMUs against jamming and interference; 2) are robust against spoofing attacks; and 3) can detect various spoofing attacks. Finally, we conducted tests using a real-time digital simulator (RTDS) which demonstrate the impacts of an attack on a PMU’s time source.

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