Lorenzo Codecasa

Politecnico di Milano | Polimi · Department of Electronics, Information, and Bioengineering

Lithium-ion batteries are widely used in a variety of applications. For effective battery management, accurate estimation of the state of charge (SOC) is essential. One of the most commonly employed methods for SOC estimation relies on the open circuit voltage (OCV) curve with respect to SOC. However, inverting the OCV-SOC function is not always st...

In this paper we introduce the use of several different Infinite Mapping Layers to model open boundaries in the 2-D Finite Element Method for the computation of transmission line parameters. The transformation maps a semi-infinite interval to a finite interval, thereby providing a simple and accurate description of open boundaries while keeping the...

Our goal is the efficient numerical approximation of solutions to the time-domain linear Max-well system. Methods like the classical finite difference time-domain method rely on the approximation of the electric and the magnetic field on two interlaced (Cartesian) grids respectively. Our method expands this idea to general triangular/tetrahedral me...

Currently, the urgent needs of sustainable mobility and green energy generation are driving governments and researchers to explore innovative energy storage systems. Concurrently, lithium-ion batteries are one of the most extensively employed technologies. The challenges of battery modeling and parameter estimation are crucial for building reliable...

Two different approaches for the linear-time solution of three-dimensional magnetostatic field problems encompassing large-scale linear systems with millions of degrees of freedom are presented. The φ–method is formulated in terms of nodal variables, i.e., magnetic scalar potentials, and involves the solution of a curl-curl linear system for pre-pr...

This paper presents a critical and detailed overview of experimental techniques for the extraction of the thermal resistance of bipolar transistors from simple DC current/voltage measurements. More specifically, this study focuses on techniques based on a thermometer, i.e., the relation between the base-emitter voltage and the junction temperature....

Thermal management of electronic devices and systems remains an active research domain, which is increasingly characterized by strong multidisciplinary collaborations, often involving both academic and industry researchers. The growing thermal and reliability demands, increased power density, and an evolving variety of platform and device types are...

In this paper, strategies to model thermo-electrochemical mechanisms occurring in Li-ion batteries are introduced. Two models are presented. The first consists in a numerical model suitable for finite-element method (FEM) simulations. The numerical model was validated by comparing simulation results with experimental data. The second model concerns...

This article presents an advanced modeling of substrate-integrated waveguide (SIW) structures by the 2-D vector finite element method (FEM). All types of losses are considered, together with input/output coupling by the rectangular waveguide and coaxial cable. Multiple dielectric regions can be defined, allowing the modeling of partially air-filled...

Multilevel Monte Carlo (MLMC) method, enhanced by a smoothing technique based on Kernel Density Estimation, is coupled with the Finite-Difference Time-Domain (FDTD) algorithm in order to estimate the probability distribution of any quantity of interest, for uncertainty quantification in electromagnetic problems. It is shown that such enhanced MLMC-...

In recent years, lithium-ion batteries (LiBs) have gained a lot of importance due to the increasing use of renewable energy sources and electric vehicles. To ensure that batteries work properly and limit their degradation, the battery management system needs accurate battery models capable of precisely predicting their parameters. Among them, the s...

We present a novel a,v-q hybrid method for solving large-scale time-harmonic eddy-current problems. This method combines a hybrid unsymmetric formulation based on the cell method and the boundary element method with a hierarchical matrix-compression technique based on randomized singular value decomposition. The main advantage is that the memory re...

The fast solution of three-dimensional eddy current problems is still an open problem, especially when real-size finite element models with millions of degrees of freedom are considered. In order to lower the number of degrees of freedom a magnetic scalar potential can be used in the insulating parts of the model. This may become difficult when the...

The recent multilevel Monte Carlo method is here proposed for uncertainty quantification in electromagnetic problems solved by the finite-difference time-domain (FDTD) method, when material parameters are modeled as random variables. It improves the estimations of the mean and variance of the quantities of interest computed on a FDTD spatial grid b...

This paper presents a comprehensive overview of nonlinear thermal effects in bipolar transistors under static conditions. The influence of these effects on the thermal resistance is theoretically explained and analytically modeled using the single-semiconductor assumption. A detailed review of experimental techniques to extract the thermal resistan...

We are concerned with a special class of discretizations of general linear transmission problems stated in the calculus of differential forms and posed on Rn. In the spirit of domain decomposition, we partition Rn=Ω∪Γ∪Ω+, Ω a bounded Lipschitz polyhedron, Γ:=∂Ω, and Ω+ unbounded. In Ω, we employ a mesh-based discrete co-chain model for differential...

This article presents a method to derive a compact model for the wideband analysis of multimode lossy (and lossless) microwave devices and antennas. The model is built from the generalized scattering matrix (GSM) of the structure computed at a set of arbitrarily chosen frequency points in the bandwidth of interest. The set of points can be increase...

A hybrid a—φ Cell Method formulation for solving eddy–current problems in 3–D multiply–connected regions is presented. By using the magnetic scalar potential the number of degrees of freedom in the exterior domain with respect to the A, V—A formulation, typically implemented in commercial software for electromagnetic design, can be almost halved. O...

A general Galerkin’s projection framework is proposed for the definition of Boundary Condition Independent (BCI) Compact Thermal Models (CTMs). First, it is shown how the proposals of BCI CTMs, deriving from the works of A. Bar-Cohen and M. N. Sabry, can be straightforwardly reinterpreted within this framework. Then, following such re-interpretatio...

In this paper, an advanced electrothermal simulation strategy is applied to a 3.3 kV silicon carbide MOSFET power module. The approach is based on a full circuital representation of the module, where use is made of the thermal equivalent of the Ohm’s law. The individual transistors are described with subcircuits, while the dynamic power-temperature...

A unified discretization framework, based on the concept of augmented dual grids, is proposed for devising hybrid formulations which combine the Cell Method and the Boundary Element Method for static and quasi-static electromagnetic field problems. It is shown that hybrid approaches, already proposed in literature, can be rigorously formulated with...

An accurate and efficient algorithm is presented, which allows deriving the structure function of a discretized 3-D heat conduction problem. In this approach, the partial thermal conductances and capacitances in the structure function are computed in terms of weighted spatial averages of thermal resistivity and volumetric heat capacity. As a result...

Abstract This study introduces the conic section arc elements in 2D and 2.5D finite element method (FEM). Elements are obtained by deforming an edge in a standard triangular element through a coordinate transformation. This allows to completely eliminate the geometrical error in structures composed of circular, elliptical, hyperbolic and parabolic...

In this paper, the dc electrothermal behavior of InGaP/GaAs HBT test devices and arrays for power amplifier output stages is extensively analyzed through an efficient simulation approach. The approach relies on a full circuit representation of the domains, which accounts for electrothermal effects through the thermal equivalent of the Ohm’s law and...

We introduce a new numerical method for the time-dependent Maxwell equations on unstructured meshes in two space dimensions. This relies on the introduction of a new mesh, which is the barycentric-dual cellular complex of the starting simplicial mesh, and on approximating two unknown fields with integral quantities on geometric entities of the two...

A novel mortar approach for the domain decomposition of field problems discretized in terms of nodal variables by the cell method is here proposed. This approach allows the use of both arbitrary polyhedral meshes and non–conforming discretizations, without limitations or complications due to the mesh type or the model geometry. Therefore, it provid...

The present work aims at quantifying how, and how much, the uncertainties on the components and material parameters of a wireless power transfer (WPT) system for the static charge of electric vehicles affect the overall efficiency and functionality of the final produced device. With the aim of considering the perspective of a possible industrial de...

A novel h-φ approach for solving 3-D time-harmonic eddy current problems is presented. It makes it possible to limit the number of degrees of freedom required for the discretization such as the T-Ω method, while overcoming topological issues related to it when multiply connected domains are considered. Global basis functions, needed for representin...

This paper discusses the benefits of an advanced highly-efficient approach to static and dynamic electrothermal simulations of multicellular silicon carbide (SiC) power MOSFETs. The strategy is based on a fully circuital representation of the device, which is discretized into an assigned number of individual cells, high enough to analyze temperatur...

This paper discusses the benefits of an advanced highly-efficient approach to static and dynamic electrothermal simulations of multicellular silicon carbide (SiC) power MOSFETs. The strategy is based on a fully circuital representation of the device, which is discretized into an assigned number of individual cells, high enough to analyze temperatur...

This paper presents the Thermal Resistance and Impedance Calculator (TRIC) tool devised for the automatic extraction of thermal metrics of package families of electronic components in both static and transient conditions. TRIC relies on a solution algorithm based on a novel projection-based approach, which—unlike previous techniques—allows (i) deal...

This chapter presents an innovative approach to the cell-level diagnosis of malfunctioning events in photovoltaic (PV) panels from the processing of temperature maps taken from low-flying drones. The application of a detailed power balance equation allows deriving the electrical power generated or dissipated by each cell with a reasonable degree of...

We introduce a new numerical method for the time-dependent Maxwell equations on unstructured meshes in two space dimensions. This relies on the introduction of a new mesh, which is the barycentric-dual cellular complex of the starting simplicial mesh, and on approximating two unknown fields with integral quantities on geometric entities of the two...

In order to couple external circuits to edge-element discretized electromagnetic models, with full field equations, global constraints involving voltages or currents need to be enforced. There is no canonical way to impose a voltage or a current without additional modeling information on the distribution of field sources that rely on topological co...

The cell method (CM) or discrete geometric approach (DGA) in the time domain, already introduced by Codecasa et al. in 2008 for the coupled Ampere–Maxwell and Faraday equations, is here recast as a Galerkin Method similar to the finite-element method (FEM). In particular, it is shown to be a mixed method comprising an explicit scheme and two disc...

This article presents a novel method for the wideband analysis of lossless arbitrary multimode waveguide junctions. The analysis is based on a compact model obtained by the frequency response at the ports only. The model makes use of the generalized scattering matrix (GSM) and its frequency derivative and is capable to deal with a large number of m...

A parametric model order reduction method combined with a polynomial spectral approximation is applied for the first time to a Volume Integral Equation method accelerated by a low–rank matrix compression technique. Such an approach allows for drastically reducing the computational cost required by uncertainty quantifications in electromagnetic prob...

This article focuses on the moment matching methodology for deriving dynamic compact thermal models (DCTMs) of electronic components. For the first time, an a priori error bound is theoretically established both in the time and frequency domains, which is suited to accurately estimate the approximation error introduced by DCTMs in practical elect...

Despite their growing adoption in a variety of applications, SiC MOSFETs are generally not available at high current rating. Therefore, there is a high demand for power modules exploiting configurations based on parallel devices. However, these products still need optimization in order to ensure long-term reliability. This paper presents a methodol...

Electronic designers continuously strive to supply more power in a smaller volume and obviously with the highest reliability performances. Emerging Planar Magnetic Components use a combination of a low-profile high-frequency magnetic core and a Printed Circuit Board, which allow a large reduction in terms of weight and size. As a drawback, power de...

The new stochastic partial element equivalent circuit (PEEC) method is proposed for uncertainty quantification in electromagnetic problems when material parameters are considered as random variables. The proposed formulation is derived using polynomial chaos expansion (PCE) and Galerkin projection. For the first time, the well-known advantages of P...

An accurate model describing the electro-thermal behavior of solar modules, subject to varying irradiance conditions, is presented. The model relies on an enhanced version of the popular one-diode model, implementing the temperature dependence of the parameters by means of a thermal feedback network. The feedback network is built by exploiting a ve...

Low-order discretization schemes are suitable for modeling 3-D multiphysics problems since a huge number of degrees of freedom (DoFs) is typically required by standard high-order Finite Element Method (FEM). On the other hand, polyhedral meshes ensure a great flexibility in the domain discretization and are thus suitable for complex model geometrie...

A novel 3-D hybrid formulation for time-harmonic eddy current problems in multiply connected domains is presented. The interior problem (in conductive regions) is discretized by the cell method (CM) in terms of magnetic vector potentials a, whereas the exterior problem (in the unbounded air domain) is discretized by the boundary element method (BEM...

Thermal Feedback Blocks represent an efficient means to perform thermal and electrothermal analyses of power converters, for which the adoption of strategies relying on 3-D numerical tools is too onerous or even impossible. In this work, we describe a RC-based thermal network extracted with a model-order reduction procedure improving the convention...