Enhanced Impedance Measurement to Predict Electromagnetic Interference Attenuation Provided by EMI Filters in Systems with AC/DC Converters

Abstract

Due to the widespread integration of renewable energy sources connected to AC and DC power systems by means of power electronics converters, electromagnetic noise propagates along lines, and metallic earth-return structures. EMI filters are commonly used to mitigate the common mode and differential mode noise at the interface of distribution lines, and their suppression characteristics are usually assessed in standard test setups, the impedances of which are, however, scarcely representative of real-world applications. In this paper, an online, inductively coupled impedance measurement method is proposed. A sensitivity analysis to highlight the benefits of the proposed setup and experimental verification is performed. The proposed method enables non-intrusive impedance measurement in energized systems, including power converters. These measures, in turn, allow the evaluation of modal insertion losses of EMI filters in real-world operating conditions. The three-phase example considered in this study shows significant deviations from manufacturer specifications, thus justifying the need for more advanced estimation techniques.

Keywords

• online impedance measurement
• power electronics
• electromagnetic interference
• common mode
• differential mode
• conducted emissions