Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Electrical Engineering

First Advisor

S.M. Hietpas


The proliferation of nonlinear loads such as static power converters and arc furnaces has produced a variety of undesirable phenomena in the operation of power systems. Often, the most important among these are harmonic distortion, increased reactive power demand and power system voltage oscillations. Harmonic distortion has become a major concern for power system experts due to its effects on sensitive loads and on the power distribution system. Many loads draw significant harmonic currents that cause voltage distortion at points of common coupling. Historically, passive LC filters followed by shunt active filters using PWM inverters have been developed and studied for reduction of harmonic components and to improve the power factor. However, certain problems, particularly resonance, instability and sensitivity to noise and temperature, have persisted. This thesis addresses the problem of line voltage distortion at a point of common coupling (PCC) by installing an AC-AC voltage converter between the PCC and the sensitive equipment. The AC-AC buck converter was considered. Sinusoidal PWM of the duty ratio of the AC-AC buck converter isolated the sensitive equipment from the harmonic components of the line voltage at the PCC. The influence of varying the switching frequency on the efficiency of the buck converter as a harmonic isolator was also studied. The validity of applying the AC-AC voltage converters for isolating the harmonic components of the line voltage at the PCC from the sensitive equipment has been established through MATLAB simulation.

Library of Congress Subject Headings

Harmonics (Electric waves)
Electric distortion
Pulse-duration modulation
Electric power system stability




South Dakota State University



Rights Statement

In Copyright