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.

Inductively Coupled In-Circuit Measurement of Multiport Admittance Parameters

“…In the framework of a general N-port formulation, the two-port case (13) assumes special relevance by the properties of the admittance matrix and fully justifies the preference in this work for admittance parameters instead of the impedance used in [2][3][4][5]. Namely, an N 3 N admittance matrix Y x can be identified by a number N(N À 1)/2 of repeated two-port evaluations.…”

“…which is the same formulation of the SPS [4,5] in a slightly different but equivalent form. Hence, the proposed MPS includes past methods as special cases.…”

“…which represent an alternative formulation of the equations of the SPS [4,5] at each port. Hence, one can adapt the same SPS calibration procedure [5].…”

“…Of note, both monitor and bulk current injection probes normally exploited in electromagnetic compatibility laboratories for quite different purposes can be conveniently reused in this context. However, well-established methodsthat is, the two-probe setup [2,3] and the single-probe setup (SPS) [4,5]-are both limited to a single measurement port. Recently, a different two-probe setup has been proposed in [6] to characterize both the self and mutual admittances in a two-port system.…”

“…In this letter, the rationale of inductively coupled measurements is fully generalized for N ports and N probes (i.e., just one probe per port), thus defining a multiple-probe setup (MPS), which reduces to [6] for N ¼ 2 and to [4,5] for N ¼ 1. Furthermore, the special two-port case is shown here to be of particular importance because it enables the characterization of N-port networks at the expense of multiple measurements by the properties of the admittance matrix.…”