Analysis and Mitigation of Harmonics for a Wastewater Treatment Plant Electrical System

Abstract

Power quality has become a pressing issue that demands solutions as power electronic equipment has been increasingly used in industrial sectors. One critical problem is how to mitigate harmful harmonics generated by the power electronic equipment. This study investigates harmonic distortion issues in a wastewater treatment plant to verify compliance with IEEE standard 519 using simulation software ETAP and realistic data from the plant. Harmonic quantification shows that the plant harmonic situation violates IEEE Standard 519 where harmonic levels exceed its voltage and current limits. Different methods were used to mitigate the harmonic situation where the core is using passive harmonic filters. It is found that the biggest contributor to the harmonic distortion is the system variable frequency drives. Using high-pulse variable frequency drives, such as 18-pulse, is proven to be beneficial for harmonic reduction. Further, installing passive harmonic filters in appropriate locations helps lower voltage and current harmonics to meet IEEE Std. 519 limits. However, adding a passive harmonic filter higher up the power distribution or adding passive filters to the feeder buses is not effective in lowering the Total Harmonic Distortion (THD) of the system. This would have the drawback of increasing the rating of the system bus voltages. Other findings include a lack of medium voltage passive filters on the market and high costs. The study contributes some insight understanding, experience, and methods for engineers when developing solutions for controlling harmonics in similar plants or industrial applications.