Current Electromagnetic Compatibility Problems of High-Power Industrial Electric Drives with Active Front-End Rectifiers Connected to a 6–35 kV Power Grid: A Comprehensive Overview

Abstract

Today, electric drive systems based on frequency converters with active front-end rectifiers (FC-AFEs) are widespread across industries. In the course of the upgrade of production facilities, such systems replace the conventional converters with thyristor- and diode-based rectifiers. FC-AFEs have the following advantages: the capacity to regenerate the power to the grid and the capacity to operate at the set power factor. The manufacturers of FC-AFEs also claim that their products have the best electromagnetic compatibility (EMC) with the power grid. The best EMC shall be achieved via a multilevel FC-AFE topology and specialized pulse-width modulation (PWM) algorithms for AFE rectifiers. However, the experience of operating mid-voltage high-power electric drives with an FC-AFE in 6–35 kV factory distribution grids with non-linear frequency response due to resonant phenomena refutes the claims of the FC-AFE manufacturers. Resonant phenomena in 6–35 kV grids are caused by the interaction of the inductance of grid components (transformers, reactors) and the capacitance of output cable lines. If the resonance frequency at a sufficient amplitude corresponds to the harmonic frequency of the current consumed by the FC-AFE, the distribution grid will feature high-frequency voltage distortions. This may lead to failures in voltage quality-sensitive electrical consumers. This problem recurred at various metallurgical companies. The purpose of this research is to make a comprehensive overview of the EMC problems during the operation of FC-AFEs at active production facilities, as well as the analysis of the technical solutions aimed at the improvement of the EMC of high-power FC-AFEs with the power grid.

Keywords

• frequency converter
• active front-end rectifier
• power quality
• electromagnetic compatibility
• PWM
• harmonics