Investigation of Grid Distortion Effects on Motor Drives with Various Filter Topologies

Abstract

Variable frequency drives employing a three-phase diode rectifier front-end are widely used across various industrial networks due to their reliability and cost efficiency. Different filter topologies are implemented in these rectifiers to reduce current harmonics. Typically, these filters are designed for normal grid conditions without distortions. However, in the presence of grid distortion, their behavior can change significantly. This article examines how grid distortion affects current harmonic emission in motor drives with various filter topologies. First, a mathematical model of the rectified voltage is developed considering the presence of PCC voltage harmonics. Subsequently, simulation results are presented to assess the effect of distorted grids on different filter configurations. The results indicate that some filters, such as the AC and DC chokes, show substantial variations in current harmonics under grid distortion, primarily influenced by the phase angle of voltage harmonics. In contrast, the Electronic Inductor consistently maintained a stable THDi across various distorted grid scenarios, demonstrating its potential as an effective solution for VFDs operating in environments with grid distortion.