Power Density Optimization of EMI Filters for Power Electronic Converters

The switching power converters are used in a broad variety of applications, from the consumer electronics to the DC distribution systems, from the vehicle applications (road vehicles, marine vehicles, aircraft) to the industrial automation. In each of these application fields, the conversion systems which present more compact size and reduced weight, at the same power, are strongly required in relation to stringent design constraints. In this context, the optimization of the power density of the converter becomes an essential requirement. The increase of the switching frequency of the static devices allows an improvement of the power density, thanks to the possibility of reducing the sizes of the energy storage passive components (inductors and capacitors). On the other hand, the increase of the switching frequency determines, with high probability, the generation of more relevant conducted electromagnetic interferences (EMI) in the frequency range 150 kHz – 30 MHz. In particular, the high switching frequency is responsible for several serious problems affecting both the reliability and the electromagnetic compatibility of the systems of which the converter is part. For this reason, noise mitigationg is, more than ever, one of the major issues in power electronic system design, particularly when dealing with stringent standard regard the maximum emission limits, which however are mandatory for the marketing of these systems. EMI filters are the most efficient among the different possible solutions to mitigate the conducted electromagnetic interferences. On the other hand, EMI filters are part of the power electronic converters and they have significant impact on the overall converter volume and weight. In order to take on this issue, besides satisfying EMI limits, a further optimization in terms of filter size and weight during the design stage is advantageous to maximize the overall converter’s power density. The identification of the configuration leading to the best power density, in terms of minimum volume/weight, is a nontrivial task. The conventional design of EMI filters disregards the power density issue. The trial and error approach requires a significant effort in terms of time spent and it does not guarantee the optimal choice of filter configuration in order to obtain the maximum power density. For this reason, an automatic optimized design procedure of discrete EMI filters has been developed. Once the power electronic converter characteristics are known and based on databases, suitably set up, of commercially available devices for the realization of EMI filters, the optimized procedure enables EMI engineers or scientists to obtain the best EMI filter configuration in term of power density. On the basis of the developed automatic design procedure, an interactive software, ODEF (Optimized Design of EMI Filters), has been developed to make the new design procedure more accessible to EMI designer. Moreover, the developed application is provided of a graphical interface which allows to analyze and compare simultaneously different EMI filter designs. The optimization algorithm can be used as a EMI filter design tool but also as a tool for the analysis of the EMI filters performance

Design and Performance Evaluation of a High Power-Density EMI Filter for PWM Inverter-Fed Induction-Motor Drives

This paper presents the design of an electromagnetic interference (EMI) filter for a low-voltage high-current induction-motor drives supplied by dc power grids. In order to effectively design the EMI filter, a suitable common-mode/differential-mode (CM/DM) separation technique has been used. Due to the high operating currents, the software-based separation technique using time-domain measurements has been applied. The proposed technique allows the CM and DM sections of the EMI filter to be properly selected in a more economical way, i.e., without the need of a dedicated hardware or costly radio frequency (RF) instrumentation. The design has been done according to a power-density criterion. The effectiveness of the proposed CM/DM separation technique and the EMI filter features/performance has been assessed by experimental tests, carried out with an 1.1-kW pulsewidth modulation (PWM) inverter-fed induction-motor drive, supplied by a 48-V dc power grid

Automatic EMI filter design for power electronic converters oriented to high power density

In this paper, a complete computer aided procedure based on the power density concept and aimed at the automatic design of EMI filters for power electronic converters is presented. It is rule-based, and it uses suitable databases built-up by considering information on passive components available from commercial datasheets. The power density constraint is taken into consideration by imposing the minimization of the filter volume and/or weight; nevertheless, the system in which the automatically designed filter is included satisfies the electromagnetic compatibility standards limits. Experimental validations of the proposed procedure are presented for two real case studies, for which the performance and the size of the best filter design are compared with those related to a conventionally designed one

FILTRI EMI COMPATTI NEI CONVERTITORI ELETTRONICI DI POTENZA

The goal of the research recently started is to create efficient EMI filters compact that allow to obtain converters with low dimensions and economically competitive

PROGETTAZIONE OTTIMIZZATA DI FILTRI EMI AD ELEVATA POWER DENSITY PER CONVERTITORI ELETTRONICI DI POTENZA

In molti dei campi di impiego dei convertitori elettronici di potenza (aeronautico, aerospaziale, automotive, etc.) è richiesta la realizzazione di sistemi di conversione che, in relazione a stringenti vincoli di progetto, presentino, a parità di potenza, dimensioni sempre più compatte e pesi ridotti. In tale ottica, l’ottimizzazione della densità di potenza (power density) del convertitore diventa un obiettivo essenzial

Computational Issues of an Electromagnetics Transient Meshless Method

In this paper we refer to the computational issues in solving Maxwell’ s curl equations without using any connectivity among the points in which the problem domain is discretized. The adopted procedure is able to approximate the electric and magnetic vector fields making use of the derivatives of a kernel function at points arranged in the computational domain. In order to improve the numerical accuracy, dealing with irregular data distribution or data located near the boundary, a suitable strategy is considered. The computational core of the overall process requires elementary linear algebra operations. In the paper the method is presented and the discussion is revolved to the computational issues. Moreover, some numerical simulations are presented to validate the numerical process

On the Distribution of Lightning Current among Interconnected Grounding Systems in Medium Voltage Grids

This paper presents the results of a first investigation on the effects of lightning stroke on medium voltage installations’ grounding systems, interconnected with the metal shields of the Medium Voltage (MV) distribution grid cables or with bare buried copper ropes. The study enables us to evaluate the distribution of the lightning current among interconnected ground electrodes in order to estimate if the interconnection, usually created to reduce ground potential rise during a single-line-to-ground fault, can give place to dangerous situations far from the installation hit by the lightning stroke. Four different case studies of direct lightning stroke are presented and discussed: (1) two secondary substations interconnected by the cables’ shields; (2) two secondary substations interconnected by a bare buried conductor; (3) a high voltage/medium voltage station connected with a secondary substation by the medium voltage cables’ shields; (4) a high voltage/medium voltage station connected with a secondary substation by a bare buried conductor. The results of the simulations show that a higher peak-lowering action on the lighting-stroke current occurs due to the use of bare conductors as interconnection elements in comparison to the cables’ shields

Space charge accumulation in undersea HVDC cables as function of heat exchange conditions at the boundaries – water-air interface

Transmission lines with undersea HVDC cables are an interesting technological solution for the supply of electrical energy to islands. The accumulation of space charge inside the dielectric layer of a HVDC cable is one of the most important element to consider in its design and during operation. The formation of space charge is due to various factors including the high dependence on the temperature of the electrical conductivity of the insulation and the establishment of a thermal gradient under load conditions. This research is focused on the space charge accumulation phenomenon around a section of a HVDC cable half dipped in water and half in air. Due to the high difference in thermal conductivity between the conductor and the insulation, the axial conduction of heat near the interface can play an important role in locally increasing the thermal gradient. The main goal of this research is to evaluate the impact of this phenomenon in the alteration of the electric field distribution. This study has been carried out by means of a 2-D thermal and electrical model of a HVDC cable developed in time domain in Matlab®. The results show the establishment of an electrical field peak near the water-air interface due to an increased thermal gradient in this area