Power quality improvement for distribution systems under non-linear conditions

Abstract

The proliferation of non-linear and electronically switched devices has increased the presence of nonsinusoidal currents and voltages in electrical distribution systems. The analysis of harmonics on the distribution systems has been described as being essential to understanding the nature of harmonic performance. One of the basic reasons for conducting a harmonic study is to analyze the effectiveness of proposed remedies to any existing harmonic problem. The analysis and design of any mitigation equipment requires precise calculation of both voltage and current waveforms. Moreover, the parameters that affect the harmonic performance have to be accurately identified and examined.

This thesis offers a new time-domain based approach for the determination of both voltage and current waveforms in non-linear distribution systems taking into account the interaction between both voltage and current harmonics (attenuation effect). In addition, the parameters that control the generation and propagation of harmonics into the distribution systems have been identified and investigated. A simple but efficient time-domain based technique has been developed and employed in order to estimate the combined non-linear load susceptance at different harmonic frequencies based on the previously calculated voltage and current waveforms and with the attenuation phenomenon considered. A novel design and implementation of reactance one-port compensators has been applied to reduce both voltage and current harmonic distortion levels in non-linear distribution systems. This application represents a significant contribution to distribution systems analysis as it successfully limits the system distortion. The performance of the proposed compensator is assessed by both simulation and experimental testing.