Publications of 2021 

Conference papers 2021  (accepted and to be published)

"Electromagnetic Fields on 3-Phase Induction Motor Using Finite Element Analysis"

Douglas Nascimento, Robert Smolenski, Hermes Loschi, Flavia Grassi, Lu Wan, Abduselam Hamid

Abstract: Electromagnetic fields of a 3-phase induction motor, i.e., electric and magnetic fields and current density, are highly influenced by its geometry, conductor material (conductivity, magnetic permeability, electric permittivity, and nonlinearity), and boundary conditions applied (interface between conductors and dielectrics). Through Finite Element Analysis (FEA), the behavior of electromagnetic fields can be predicted. Thus, favoring the electromagnetic interference mitigation techniques of the 3-phase induction motor. Therefore, this paper presents numerical modeling with FEA, based on COMSOL, as an early pre-compliance tool to investigate the current density distribution and electric and magnetic fields. The validation of the modeling approach will be presented and discussed considering a 3-phase induction motor. Furthermore, the CISPR 25 will be considered to evaluate the interactions between electric and magnetic fields, current density distribution, and skin effect on an increasing frequency.

"The Effect of Stray Capacitance to the Common Mode Current on Three-Phase System"

Muhammad Septian Alamsyah, Francinei Vieira, Sebastian Koj, Heyno Garbe

Abstract: The common-mode (CM) current phenomena is one of many problems in the EMC world due to the radiated magnetic field caused by it. A power transmission line with a delta-connection generator and load normally do not have a connection to ground to establish a line for the return current. To determine the CM current, finding the stray capacitances to the ground is highly important because they are used as the return path for the CM current. In this paper, the investigation of the CM current behavior with the stray capacitances will be investigated using a three-phase equivalent system of a wind turbine (WT). The wind turbine body is the place where the CM current flows, due to the stray capacitances between the power cables and the WT body around it. The CM current can be determined using the current magnitudes in a pointer-image method, which has a good agreement for CM current prediction and it might become a very useful tool applicable to measurements.

"Efficient Multichannel Time-domain Multiaxis Loop Antenna Measurement for Frequencies below 30 MHz"

Denys Pokotilov, Robert Voght-ardatjew, Frank Leferink.

Abstract: Conventional frequency-domain measurements are slow and are not able to grab time-varying effects, compared to time-domain measurements. Standard measurement procedures, for example CISPR 36 for electric vehicles, requires measurements at multiple positions around the equipment under test. Small resolution bandwidth in combination with long dwell time for every frequency step, results in a long measurement time. This is especially true in the lower frequency range as the bandwidths are small and thus need more measurement time. CISPR 36 requires also using only one antenna in parallel or perpendicular position to the equipment under test at once. Using time-domain measurements, the measurement speed can be already significantly improved. To effectiveness of measurements can be increased drastically if multiple antennas are posited at several locations around the equipment under test, and multiple digitiser channels are used in parallel. A new antenna construction for multidirectional measurements in combination with a cost-efficient multichannel digitizer for time-domain measurements in the frequency range below 30 MHz is proposed in this paper. Simulation results, theoretical background and initial measurements are shown, proving that such a method is indeed viable.

"Micro-Grid Inrush Current Stability Analysis"

Alexander Matthee, Niek Moonen, Frank Leferink

Abstract: Transient currents can severely impact the operation of weak or islanded grids. Inrush current electromagnetic compatibility challenges, due to their unpredictable and intermittent nature, are very difficult to identify. Using multi-point synchronised measurements, analysis is performed on an inverter. The supply powers various loads that are observed during cold start as well as under load switching conditions. Inrush event triggered failure probability is linked to non linear and average load levels.

"The Influence of Commercial PC Switched Mode Power Supply Interference on the PRIME PLC Performance"

Waseem El Sayed, Paolo Crovetti, Piotr Lezynski, Robert Smolenski, Amr Madi and Flavia Grassi

Abstract: In the last few decades, the use of power converters has become essential in the smart grid environment. Consequently, this leads to the presence of a high-level of conducted electromagnetic interference between the smart grid elements. This paper studies the effect of two power converter modulation techniques: conventional fixed-frequency modulation and spread-spectrum modulation, on the performance of the Power Line Communication (PLC) signal. The paper presents a practical implementation of the system and discusses the results for different operating scenarios.

"The Effect of Spread Spectrum Modulation for a Buck Converter Coupled with a Single Wired Communication Link"

A. Pena-Quintal, K. Niewiadomski, V. Muneeswaran, S. Greedy, M. Sumner, D.W.P. Thomas

Abstract: This paper demonstrates the effect of using a Simple Spread Spectrum modulation as an optimisation technique for an asynchronous Buck Converter with a communication cable coupled at the input voltage point. The EMI effect created by the switching nature of the converter generates damped oscillations on the data cable that can have great impact on the quality of the communication channel. Frequency domain analysis showed lower EMI levels in the power cable when compared to the standard deterministic modulation. However, there is no real improvement in the Time domain due to the increase of the Bit Error Rate.

"Conducted Emissions Measurements in DC Grids: Issues in Applying Existing LISN Topologies and Possible Solutions"

AD Khilnani, L Wan, M Sumner, D.W.P Thomas, A  Hamid, F Grassi

The reported increase of conducted emissions (CE) in the low frequency range (2-150 kHz) from power-electronic based devices in DC grids is deemed problematic. To assure Electromagnetic Compatibility (EMC), every device must be certified for an acceptable CE level in this frequency range. Further, the accurate characterisation of CE in the low frequency range for DC systems is challenging. To measure the CE from a device against a standard impedance, the use of a Line Impedance Stabilisation Network (LISN) is foreseen by the EMC standards. However, existing LISNs have a bandwidth that is not suitable for low frequency measurements. Furthermore, the standard LISN applied to AC systems may not be applicable to DC systems, which may have a predominantly capacitive impedance. Hence, ensuring accurate and repeatable measurements from the LISN cannot be guaranteed in DC systems. In this paper, possible issues in applying existing LISN topologies for measuring low frequency CE in DC grids are investigated. Also, solutions to adapt the existing LISN topology based on CISPR-16-1 standard are suggested, along with a novel LISN topology.

"Assessment of Validity Conditions for Black-Box EMI Modelling of DC/DC Converters"

Lu Wan, Abduselam Beshir, Xinglong Wu, Xiaokang Liu, Flavia Grassi, Giordano Spadacini, Sergio Pignari 

Abstract: Black-box modelling approaches, based on suitable sets of measurements at the output ports of the device, are often exploited for the modelling of power converters to predict their conducted emissions. However, these techniques can be effectively applied only if the device to be modelled can be approximately treated as a linear and time-invariant (LTI) system. This assumption is not necessarily satisfied by every power converter. In order to investigate suitable conditions assuring effectiveness of black-box modelling for a boost converter, this work investigates the role that the converter input capacitors and the functional inductor play in masking the inherent non-linear and time variant behavior of the switching modules, and their impact on the effectiveness of the proposed black-box model. It will be shown that preliminary measurements of the differential mode impedance of the converter can provide useful information on the feasibility of black-box modelling techniques, even in the absence of detailed information on the internal architecture of the converter.

Journal papers 2021

"Black-Box Modelling of Low-Switching-Frequency Power Inverters for EMC Analyses in Renewable Power Systems"

Lu Wan , Abduselam Hamid Beshir , Xinglong Wu , Xiaokang Liu , Flavia Grassi , Giordano Spadacini , Sergio Amedeo Pignari , Michele Zanoni , Liliana Tenti and Riccardo Chiumeo 

Abstract: Electromagnetic interference (EMI) from renewable power systems to the grid attracts more attention especially in the low-frequency range, due to the low switching frequency of high power inverters. It is significantly important to derive EMI models of power inverters as well as to develop strategies to suppress the related conducted emissions. In this work, black-box modelling is applied to a three-phase inverter system, by implementing an alternative procedure to identify the parameters describing the active part of the model. Besides, two limitations of black-box modelling are investigated. The first regards the need for the system to satisfy the linear and time-invariant (LTI) assumption. The influence of this assumption on prediction accuracy is analysed with reference to the zero, positive and negative sequence decomposition. It is showing that predictions for the positive/negative sequence are highly influenced by this assumption, unlike those for the zero sequence. The second limitation is related to the possible variation of the mains impedance which is not satisfactorily stabilized at a low frequency outside the operating frequency range of standard line impedance stabilization networks.

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