Available at: https://digitalcommons.calpoly.edu/theses/3257
Date of Award
6-2026
Degree Name
MS in Electrical Engineering
Department/Program
Electrical Engineering
College
College of Engineering
Advisor
Taufik
Advisor Department
Electrical Engineering
Advisor College
College of Engineering
Abstract
This thesis investigates how residential harmonic distortion influences distribution transformer performance and overall system health. As power electronic devices such as electric vehicle chargers, heat pumps, and modern household appliances, become increasingly common, the harmonic currents produced by nonlinear loads pose growing challenges for residential distribution networks. These harmonics elevate transformer losses, accelerate thermal aging, and reduce equipment lifespan, underscoring the need for detailed analysis to support safe and reliable grid operation. A MATLAB/Simulink model was developed to evaluate three transformer ratings (15 kVA, 75 kVA, and 150 kVA) supplying multiple houses at the point of common coupling (PCC) under a wide range of loading and harmonic conditions. Each house includes both linear and nonlinear load components as well as a rooftop photovoltaic (PV) system. Key performance metrics examined include voltage and current total harmonic distortions, total demand distortion, harmonic current magnitudes, transformer losses, and operating temperature. Simulation results show that nonlinear loads are the dominant source of harmonics, with higher nonlinearity producing increased current and voltage distortion and greater harmonic related losses. Transformer temperature is strongly influenced by both loading level and harmonic content, with smaller transformers exhibiting greater sensitivity due to higher per unit loading. Incorporating PV generation significantly reduces transformer loading, losses, and thermal stress across all cases.
Overall, the study demonstrates that managing residential nonlinear loading is essential for maintaining power quality and transformer longevity. It further highlights the important roles of transformer sizing and PV integration in improving system reliability in modern, electrified neighborhoods.