ORCID Identifier(s)

0000-0002-5111-3414

Graduation Semester and Year

2019

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Electrical Engineering

Department

Electrical Engineering

First Advisor

Wei-Jen Lee

Abstract

With the increasing penetration of renewable generation resources, power grids have become more susceptible to sub-synchronous resonance phenomena, especially to sub-synchronous control interaction, which produces fast-growing oscillations. The power system operation requirements for a reliable, fast and accurate detection and monitoring system for protection and mitigation purposes are increasing. Besides, risk assessment analysis during grid planning and update studies can be extremely time-consuming due to a large number of possible grid configurations and small time-steps required for the simulation of detailed electromagnetic transient (EMT) models. The first part of this dissertation aims to provide an optimized tool for SSR risk assessment analysis based on frequency scanning that uses a multi-frequency signal to estimate the grid impedance at all frequencies with one simulation instead of one simulation per frequency of interest. The technique reduces the effects of nonlinearities normally present in power-electronic-based devices, is based on the harmonic injection method and can be used with black-box models. A case study based on the Texas synthetic grid and with two wind farms and a VSC-based STATCOM was used for the validation of the proposed method, which showed superior accuracy than other studied techniques while being 11.71 times faster than multiple single-frequency injections. The second part of this dissertation provides an SSR detection system based on the power spectrum of the input signal plus frequency, magnitude, and derivative-of-magnitude estimators. All the signal conditioning techniques were also discussed and optimized to enable the detection system to efficiently and accurately work throughout the whole sub-synchronous range (5-55 Hz for a 60 Hz system). Finally, a complete monitoring system from data acquisition to data logging was implemented for the detection system in an FPGA-CPU heterogeneous platform and tested in real-time devices. The system provides several mechanisms to ensure its own reliable operation with several self-monitoring schemes and a health indicator in a dual modular redundancy scheme (primary and backup controller-units). A software-implemented voting scheme then decides which unit will forward all information to the subsystems that will use the output of the detection system. The Texas synthetic grid case was applied to the monitoring/detection system and the detection of sub-synchronous control interaction was observed with pickup times within 10 ms to 40 ms depending on the system disturbance.

Keywords

Crest factor, Detection systems, Doubly-fed induction generator (DFIG), Dual modular redundancy, Fast Fourier transform (FFT), Field programmable gate arrays (FPGA), filters, Frequency scan, Harmonic injection, Impedance estimation, Monitoring systems, Multisine signals, Nonlinear systems, Power spectrum, Power system protection, Real-time systems, Redundancy, Reliability, Risk assessment, Series-compensated transmission lines, Signal conditioning, Small signal analysis, Sub-synchronous control interaction (SSCI), Sub-synchronous resonance (SSR), Sub-synchronous oscillation (SSO), Wind farms

Disciplines

Electrical and Computer Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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