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MODELING AND MULTI-OBJECTIVE OPTIMIZATION OF INDUCTIVE POWER COMPONENTS

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This thesis deals with the modeling and multi-objective optimization of
inductive power components, in order to improve the efficiency and/or
power density of power electronic systems.
The first part of the thesis introduces how to model magnetic circuits,
i.e. how to set up an accurate reluctance model of an inductive
component. A novel approach to accurately determine the reluctances
of air gaps is introduced. The approach is easy to handle as it is based
on a modular concept where a simple basic geometry is used as a building
block to describe different three dimensional air gap shapes.
The second part of the thesis deals with core loss modeling. The
applied core loss approach can be seen as a hybrid of an improved version
of the empirical Steinmetz equation and an approach based on a
material loss database (loss map). In order to build the material loss
database, core loss measurements must be made. Therefore, special
focus is placed on how core losses can be measured and what measurements
are necessary for an accurate core loss modeling.
Relaxation effects in magnetic materials are discussed. In modern
power electronic systems, voltages across inductors or transformers
generally show rectangular shapes, including periods of zero voltage. In
most core loss models, the phase where the voltage across the magnetic
component is zero (i.e. the flux remains constant) is not considered. It is
implicitly assumed that no losses occur when the flux remains constant.
However, as measurements show, this is not a valid simplification. In
phases of constant flux, losses still occur in the material. This is due
to relaxation processes. A new core loss modeling approach that takes
such relaxation effects into consideration is given.
Another aspect to be considered is the fact that core losses are influencedGraph (SPG) that shows the dependency of the Steinmetz parameters
(,  and k) on premagnetization is proposed. This permits the calculation
of core losses under DC bias conditions.
Power electronic engineers often work with circuit simulators in order
to validate their designs before building costly prototypes. It is
shown, how to calculate core losses from a simulated flux waveform. In
order to do this, the simulated flux waveform is divided into its fundamental
flux waveform and into piecewise linear flux waveform segments.
The loss energy is then calculated for the fundamental and all piecewise
linear segments, summed and divided by the fundamental period length
in order to determine the average core loss. Another aspect to be considered
in core loss calculation is the effect of the core shape and size.
By introducing a reluctance model of the core, and with it, calculating
the flux density in every core section of (approximately) homogenous
flux density, one can calculate the losses of each core section. The core
losses of each section are then summed to obtain the total core losses.
This generally leads to a high accuracy. However, under certain circumstances,
in tape wound cores a flux orthogonal to the tape layers
can lead to high eddy currents and thus to high core losses.
The second source of losses in inductive components is the ohmic
losses in the windings. The resistance of a conductor increases with
increasing frequency due to eddy currents. Self-induced eddy currents
inside a conductor lead to the skin-effect. Eddy currents due to an
external alternating magnetic field, e.g. the air gap fringing field or
the magnetic field from other conductors, lead to the proximity-effect.
The skin-effect and proximity-effect losses can be calculated for round,
litz, or foil windings; provided that the external field and the current is
known exactly. However, the calculation of the external magnetic field
strength, which has to be known when calculating the proximity losses,
is challenging. In the case of an un-gapped core and windings that are
fully-enclosed by core material, 1D approximations to determine the
magnetic field exist. However, in the case of gapped cores, such 1D
approximations are not applicable as the fringing field of the air gap
cannot be described in a 1D manner. The approach presented in the
thesis is a 2D approach in which the magnetic field at any position can
be calculated as the superposition of the fields of each of the conductors.
The impact of a magnetic conducting material can be modeled with
the method of images. The presence of an air gap can be modeled asForce (MMF) across the air gap.
Another important aspect in modeling inductive components is their
thermal behavior. This is not only important to avoid overheating;
it also has importance in modeling the losses correctly, as they are
influenced by the temperature. Formulae that allow heat conduction,
convection and radiation to be calculated are given.
The last part of the thesis is about the multi-objective optimization
of inductive power components. The optimization of inductive components
is illustrated using the example of LCL filters for three-phase PFC
rectifiers. The optimization procedure leads to different filter designs
depending on whether the aim of the optimization is more on reducing
the volume V or more on reducing the losses P. Furthermore, an overall
system optimization, i.e. an optimization of the complete three-phase
PFC rectifier, is given.
a fictitious conductor carrying a current equal to the Magneto-Motive
by a DC premagnetization. The Steinmetz Premagnetization

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Ketersediaan

EB200107

My Library

Tersedia

Informasi Detil

Judul Seri

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No. Panggil

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Penerbit

: Switzerland., 2012

Deskripsi Fisik

xvi, 2017 p.

Bahasa

English

ISBN/ISSN

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Klasifikasi

NONE

Tipe Isi

-

Tipe Media

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Tipe Pembawa

online resource

Edisi

-

Subyek

-

Info Detil Spesifik

Ebook

Pernyataan Tanggungjawab

-

Versi lain/terkait

Lampiran Berkas

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