ECE: Electrical & Computer Engineering
ECE News

Online Measurement of Three-phase AC Power System Impedance in Synchronous Coordinates

12:00 AM - 1:30 PM on Wednesday, January 23, 2013
Location: 140G Whittemore Hall

Ph.D., Dissertation, Defense for Shen, Zhiyu

Graduate Advisory Committee:

Dr. Dushan Boroyevich, Chair
Dr. Douglas Lindner
Dr. Guo-Quan Lu
Dr. Jack Lesko
Dr. Paolo Mattavelli


Small-signal analysis is a well accpeted approach in assess AC power distribution system stability. Literature investigates its use with system models, but the lack of equipment to measure such impedance prevents its use in practical systems. After reviewing the state-of-the-art development of impedance measurement systems, the dissertation analyzes several systematical error sources in the system, which include the signal processing and sampling circuits, the phase estimation for coordinate transformation and the injection device connection, and proposes the solution to reduce their influence. Improved algorithm and system architecture are proposed to increase the measurement speed and accuracy. Chirp signal is used as an excitation signal to extract impedances at a group of frequencies at one time. The use of both shunt current injection and series voltage injection improves the SNR of measured signal. Oversampling, cross-correlation and frequency domain averaging technique are used to further reduce the influence of noise. An instrument is built based on the proposed solution. The test result shows the validity of the proposed solution.