Z. De Grève

Multiobjective optimization of a power supply for space application using a flexible CAD tool

This paper presents the adaptation of a previously published CAD tool that was initially conceived for high power isolated dc-dc converters, to the multiobjective optimal design of a switch-mode power supply for space application. The main changes to the existing tool concern the magnetic elements (transformer and inductor), the reduction of voltage and current ratings of the semiconductor devices, the cooling aspects, and the input filter design. The database of the tool is also enriched with silicon carbide devices in order to highlight, for the considered application, the benefits of using this new technology. The Pareto fronts in terms of power loss and mass are shown for two sets of electrical specifications of the power supply. Several solutions are analyzed in detail through the values of the optimization variables.

Fast computation of R, L parameters of high frequency multi‐winding magnetic components

Purpose – The purpose of this paper is to propose a numerical procedure for the extraction of RL equivalent circuits of high frequency multi‐winding transformers with a low computational time.Design/methodology/approach – Rigorous RL equivalent circuits of multi‐winding transformers can be obtained by performing open and short‐circuit tests. In this work, the finite element method (FEM) is employed as a virtual laboratory in order to derive such circuits. However, an accurate modeling of skin and proximity effects in the windings requires extremely dense meshes at high frequencies. Therefore, a 2D frequency‐domain homogenization of the windings, which conducts to coarser meshes, is applied in order to decrease the computational burden. The fine and homogenized models are compared in terms of simulation time as well as accuracy.Findings – A significant decrease in simulation times is observed with the homogenized model (one order of magnitude at high frequencies for 2D models), while keeping acceptable rel...

Evaluation of power loss and mass gains of SiC versus Si-based switch-mode power supplies using a multiobjective optimization CAD tool

In this paper, the power losses and mass of multiobjective optimal designed isolated dc-dc converters are compared, based on Si and SiC technologies. To that end, a computer-aided design (CAD) tool, previously published by the authors, is used. The database of the existing tool is enriched with wide band gap semiconductor devices currently available from manufacturers. The results are presented for two switchmode power supplies operating at very different power levels. The gains in terms of power losses and mass from one technology to the other are quantified thanks to the CAD tool, which is an asset.

Analyzing and reducing error in 2-D frequency domain homogenization of windings for R, L parameters FE computation

In this work, the error made by frequency domain homogenization of windings in 2-D magnetodynamics is quantified. To that end, the homogenized fields are combined with the analytical solutions (a) of eddy currents flowing in a circular conductor placed in a uniform alternating magnetic induction (proximity effect) and (b) of current density in conductors with non-zero net current (skin effect). They are then compared to the fields from the fine model, taken as reference. It is shown that error on resistance can reach 10% at high frequencies for magnetic components with a limited number of turns. Procedures to improve winding R, L parameters estimation from homogenized solution are introduced.

Comparing partial element equivalent circuit and finite element methods for the resonant wireless power transfer 3D modeling

In this paper, the unstructured Partial Element Equivalent Circuit (PEEC) method is applied in 3D magnetodynamics to resonant Wireless Power Transfer (WPT) coils modeling. A particular attention is paid on the coupling with circuit equations in order to model the resonant conditions at the circuit and field levels. A preliminary comparison with 3D finite element method highlights the high potential of the PEEC method for the modeling of WPT coils.

An original method for measuring the stator leakage reactance of synchronous machines

This paper proposes an original method for accurately measuring the stator leakage reactance of synchronous machines. The approach relies on an experimental equivalence of resulting fluxes between the unsaturated open-circuited and permanent short-circuited tests. This requires the presence of measurement turns in the air gap of the machine. A complete comparison with existing methods (Potier, El-Serafi & Wu, rotor removed test and geometric calculation) is moreover proposed. A critical analysis is performed, and pros and cons of each method are highlighted.

A virtual laboratory for the modeling of Wireless Power Transfer systems

In this work, a virtual laboratory for modeling Wireless Power Transfer systems is presented. It is based on the Finite Element Method and is fully parametrized, so as to analyze various coil configurations. A 3D FE formulation is moreover considered in order to model coil misalignments. The numerical results are compared with analytical formula and experimental measurements.

Impact of the geographical correlation between wind speed time series on reliability indices in power system studies

In order to help system (transmission and/or distribution) operators to account for the stochastic nature of wind during the grid planning phase, univariate AutoRegressive Moving Average (ARMA) time series models for the long term modeling of wind speed are generally considered. Practically, different geographical correlation levels are observed in the bibliography when sampling wind generation in the framework of long-term analysis tools (e.g. sequential Monte Carlo algorithms). The traditional approach is to assess extreme correlation scenarios (entire independence, entire correlation). Some recent works try to better capture the correlation patterns of real data by using matrix methods, like the Cholesky decomposition. In this work, two methods for reproducing the actual correlation are compared on a statistical basis on the one hand, and in the framework of a Monte-Carlo reliability analysis on the other hand. It is shown that a good correlation model is mandatory for obtaining correct reliability indices.

Influence of the geometrical uncertainties on the RLC parameters of wound inductors modeled using the finite element method

In this work, we highlight the influence of geometrical uncertainties (winding pattern and wire diameter) on the RLC parameters of wound magnetic components. To that end, the finite element method is embedded in a Monte Carlo simulation in order to compute probability distributions of the parameters. An algorithm to randomly generate realistic winding configurations is also proposed.

Multiobjective optimal design of wireless power transfer devices using a Genetic Algorithm and accurate analytical formulae

In this work, the Non-dominated Sorting Genetic Algorithm (NSGA) is employed for the multiobjective optimal design of Resonant Inductive Power Transfer (RIPT) devices. A thorough review of the literature has been performed in order to propose accurate analytical formulae for computing the lumped parameters of the system equivalent circuit. A particular attention is paid on the representation of the skin and proximity effects, and on the consideration of any relative position between the coils. The tool permits to observe design trends by comparing optimal individuals in the Pareto front, and is illustrated on an electric vehicle battery charging application. In that case, a design able to transfer 3 kW at 60 kHz, with 93.53 % efficiency through 25 cm air with a fixed radial space footprint of 25 cm, and capable to support a lateral misalignment of 10 cm, was obtained.