Susceptibility analysis of complex systems

A study of electromagnetic coupling effects on systems containing distributed elements and lumped linear components is presented. The structure is decomposed into sections containing multiconductor transmission lines and interconnection blocks holding lumped elements. The external field is assumed to interfere with line sections, but mutual influences among different sections are neglected. Both the sections and the blocks are treated as multiport components and characterized by their scattering parameters. The analysis is based on a correspondence matrix that accounts for the topology of connections between sections and blocks. Closed-form solutions are derived in the Laplace domain, and the temporal evolution of voltages and currents at any of the system ports is obtained by a numerical inversion. This method makes it possible to predict the susceptibility of complex systems and to verify the intra-system compatibility (especially crosstalk). The relative influence of circuit components and of line layouts on the severity of interferences is evidenced by simulation result

Scattering analysis of signal degradation and interferences on long and lossy interconnects

A time domain scattering formulation for low-loss nonlinearly loaded multiconductor transmission lines is presented. It is suitable for an efficient and accurate evaluation of crosstalk and field coupling. A simulation of the effects of interference on a long interconnect is give

Influence of the line characterization on the transient analysis of nonlinearly loaded lossy transmission lines

The analysis of nonlinearly terminated lossy transmission lines is addressed in this paper with a modified version of a method belonging to the class of mixed techniques, which characterize the line in the frequency domain and solve the nonlinear problem in the time domain via a convolution operation. This formulation is based on voltage wave variables defined in the load sections. The physical meaning of such quantities helps to explain the transient scattering process in the line and allows us to discover the importance (so far often overlooked) of the reference impedance used to define the scattering parameters. The complexity of the transient impulse responses, the efficiency of the algorithms, and the precision of the results are shown to be substantially conditioned by the choice of the reference impedance. The optimum value of the reference impedance depends on the amount of line losses. We show that a low-loss line can be effectively described if its characteristic impedance or the characteristic impedance of the associated LC line is chosen as the reference impedance. Based on the physical interpretation of our formulation, we are able to validate the numerical results, and to demonstrate that, despite claimed differences or improvements, the formulations of several mixed methods are fundamentally equivalen

Measurement-Based Equivalent Circuit Model for Time-Domain Simulation of EMI Filters

In this paper, a methodology to derive equivalent circuits of EMI filters from S-parameters is introduced and discussed. Starting from measured S-parameters and with no need for information on the internal structure of the filter, a rational approximation of the measured frequency responses is derived and equivalent circuits are directly synthesized. The proposed black-box filter models are compatible with SPICE solvers and can be used, in combination with component-level representations of power-electronic equipment, for the prediction of conducted emissions through time-domain simulation. As an example of usage, a CISPR-25 test setup where the EMI filter operates in the presence of an inverter is discussed

Efficient computation of transient responses of frequency-dependent nonlinearly loaded transmission lines

The authors address the combined time and frequency domain analysis of nonlinearly loaded low-loss transmission lines. They show that a variety of interconnects are characterized by transfer functions, whose impulse responses have a fast initial-time structure and a slow long-time component. A piecewise linear approximation of the transient functions with nonuniform sampling is proposed as an effective method to obtain high accuracy with low computational cost

Prediction of EMI Filter Attenuation in Power-Electronic Converters via Circuit Simulation

This article investigates the conducted-emission (CE) suppression characteristics of electromagnetic interference (EMI) filters used in power-electronic equipment by time-domain circuit simulation. An operational definition of insertion attenuation is introduced by comparing the CE in the absence and in the presence of the EMI filter. For the sake of exemplification, the analysis focuses on switched-mode dc-dc converters. It is shown that the EMI-filter attenuation behaves differently from the standard insertion loss (IL) and exhibits peculiar properties in these circuits. Namely, its response is known at discrete frequencies where the converter generates CE and may strongly depend on the harmonic index so to jump between quite different levels from a harmonic component to the next one, with a pseudoperiodic behavior, which can be related to the duty cycle. This effect is caused by circuit nonlinearity and is partially mitigated if the simulation accounts for two practically relevant aspects: random instability of the duty cycle and resolution bandwidth of the EMI receiver. The dependence of the common-mode (CM) and differential-mode attenuations on the loading conditions and duty cycle is analyzed, and it is shown that linear IL models provide reasonable predictions of CM attenuation only. Finally, experimental evidence of the unveiled phenomena is presented

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

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

Techniques and Challenges in Conducted EMI Analysis of Renewable Energy Systems

Renewable energy sources have been widely integrated into modern power systems, leading to the massive use of power converters, which represent the main sources of conducted electromagnetic (EM) noise. Furthermore, power grids employ interactive devices including smart meters that resort to powerline communication (PLC) technology and are usually more susceptible to EM noise than traditional electrical machinery. This paper provides a state-of-the-art overview of conducted EM interference (EMI) analysis in power systems, focusing on EMI prediction models, PLC coexistence issues, and measurement challenges. Insights into the use of various methods in different application scenarios are provided, and relevant future studies are foreseen