Harmonic generation of variable speed drive under complex-voltage unbalance conditions

Abstract

Efficiency in the industrial sector is a priority when seeking to minimize production costs and reduction in losses. Harmonic generation and associated losses need to be treated carefully with broad implementation of variable speed induction motor applications. The effect of these induced losses can add up to a significant loss. This study uses statistical tools alongside synthesized models to deduce and compare outcomes from regulated and unregulated converters in which harmonics may be triggered by switching algorithm of modern switch-mode power supplies and other inductive loads attached to supply bus system. These harmonics accumulate over time due to losses propagating through connected equipment when changes occur on the bus system. In this regard, results obtained from investigating and comparing three original equipment manufacturer variable speed drives that were exposed to voltage unbalance and complex harmonic conditions are presented in this study. A conclusion accomplished from the investigation and comparison suggests that generation of 6-pulse uncontrolled rectifier losses is negligible. Experimental validation confirms that unregulated 6-pulse converter produces on average more harmonics compared to the regulated converter of standard as recommended in guideline to permissible harmonic tolerance.