Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Electrical Engineering

Major Professor

Kevin L. Tomsovic

Committee Members

Seddik M. Djouadi, Fangxing Li


Accurate load modeling is key to depicting realistic system behavior in power system simulations. In the past, the use of static load models resulted in overly optimistic results, which led to unforeseen outages and issues following faults. One common cause of these types of unforeseen issues is Fault Induced Delayed Voltage Recovery (FIDVR). FIDVR occurs due to the stalling of single-phase residential air conditioners (A/C), and causes the voltage recovery after a fault to be slow. Improvements in load models over time have resulted in the capability of modeling load dynamics, and therefore better FIDVR.

A composite load model based on real world composition data is applied to a 179 bus system representing the WECC system. Then through mathematical derivation and fault analysis, a method, Z Deviation, is proposed as a way to identify the occurrence of FIDVR. Z Deviation is then implemented in a control scheme used to improve voltage recovery following FIDVR, and its effectiveness is compared to a device level protection scheme.

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