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The purpose of this paper is to optimize and improve a bipolar charge transport (BCT) model used to simulate charge dynamics in insulating polymer materials, specifically low-density polyethylene (LDPE).

An optimization algorithm is applied to optimize the BCT model by comparing the model outputs with experimental data obtained using two kinds of measurements: space charge distribution using the pulsed electroacoustic (PEA) method and current measurements in nonstationary conditions.

The study provides an optimal set of parameters that offers a good correlation between model outputs and several experiments conducted under varying applied fields. The study evaluates the quantity of charges remaining inside the dielectric even after 24 h of short circuit. Moreover, the effects of increasing the electric field on charge trapping and detrapping rates are addressed.

This study only examined experiments with different applied electric fields, and thus the obtained parameters may not suit the experimental outputs if the experimental temperature varies. Further improvement may be achieved by introducing additional experiments or another source of measurements.

This work provides a unique set of optimal parameters that best match both current and charge density measurements for a BCT model in LDPE and demonstrates the use of trust region reflective algorithm for parameter optimization. The study also attempts to evaluate the equations used to describe charge trapping and detrapping phenomena, providing a deeper understanding of the physics behind the model.

The purpose of this paper is numerical calculation of total electric field in oil-paper insulation. Now, there is no effective method to consider the influence of space charges when calculating the total electric field distribution in the main insulation system of the valve-side winding of an ultra-high-voltage direct current converter transformer.

To calculate the total electric field in an oil-paper insulation system, a new simulation method in single-layer oil-paper insulation based on the transient upstream finite element method (TUFEM) is proposed, in which the time variable is considered. The TUFEM is used to calculate the total electric field in an oil-paper insulation system by considering the move law of space charges. The simulation method is verified by comparing the simulation results to the test data. The move law of space charges and distribution characteristics of the electric field under difference voltage values in single-layer oil-paper insulation were presented.

The results show that the TUFEM has an excellent accuracy compared with the test data. When carrier mobility is a constant, the time to reach the steady state is inversely correlated with the initial electric field intensity, and the distortion rate of the internal total electric field is positively correlated with the initial electric field intensity.

This paper provides an exploratory research on the simulation of space charge transport phenomenon in oil-paper and has guiding significance to the design of oil-paper insulation.

The purpose of this paper is to develop a numerical simulation method based on the transient upstream finite element method (FEM) and Schottky emission theory to reveal the distribution characteristics of space charge in oil-paper insulation.

The main insulation medium of the converter transformer in high voltage direct current transmission is oil-paper insulation. However, the influence of space charge is difficult to be fully considered in the insulation design and simulation of converter transformers. To reveal the influence characteristics of the space charge, this paper proposes a numerical simulation method based on Schottky emission theory and the transient upstream FEM. This method considers the influence of factors, such as carrier mobility, carrier recombination coefficient, trap capture coefficient and diffusion coefficient on the basis of multi-physics field coupling calculation of the electric field and fluid field.

A numerical simulation method considering multiple charge states is proposed for the space charge problem in oil-paper insulation. Meanwhile, a space charge measurement platform based on the electrostatic capacitance probe method for oil-paper insulation structure is built, and the effectiveness and accuracy of the numerical simulation method is verified.

A variety of models are calculated and analyzed by the numerical simulation method in this paper, and the distribution characteristics of the space charge and total electric field in oil-paper insulation medium with single-layer, polarity reversal of plate voltage and double-layer are obtained. The research results of this paper have the guiding significance for the engineering application of oil-paper insulation and the optimal design of converter transformer insulation.

The purpose of this paper is to describe a rapid and robust axisymmetric hybrid algorithm to create dynamic temporal and spatial charge distributions, or charge map, in the simulation of bipolar charge injection using Schottky emission and Fowler-Nordheim tunneling, field-dependent transport, recombination, and bulk and interfacial trapping/de-trapping for layered polymer films spanning the range from initial injection to near breakdown.

This hybrid algorithm uses a source distribution technique based on an axisymmetric boundary integral equation method (BIEM) to solve the Poisson equation and a fourth-order Runge-Kutta (RK4) method with an upwind scheme for time integration. Iterative stability is assured by satisfying the Courant-Friedrichs-Levy (CFL) stability criterion. Dynamic charge mapping is achieved by allowing conducting and insulating boundaries and material interfaces to be intuitively represented by equivalent free and bound charge distributions that collectively satisfy all local and far-field conditions.

Charge packets cause substantial increase of electric stress and could accelerate the breakdown of polymeric capacitors. Conditions for the creation of charge packets are identified and numerically demonstrated for a combination of impulsive step excitation, high charge injection, and discontinuous interface.

Metallized bi-axially oriented polypropylene (BOPP) dielectric thin film capacitor with self-clearing and enhanced current carrying capability offer an inexpensive and lightweight alternative for efficient power conditioning, energy storage, energy conversion, and pulsed power. The originality is the comprehensive physics and multi-dimensional modeling which span the dynamic range from initial injection to near breakdown. This model has been validated against some empirical data and may be used to identify failure mechanisms such as charge packets, gaseous voids, and electroluminescence. The value lies in the use of this model to develop mitigation strategies, including re-designs and materials matching, to avoid these failure mechanisms.

The package CURRY offers a wide range of built‐in facilities for 2D device modelling of a large variety of structures such as MOS, bipolar and charge coupled devices. These capabilities will be illustrated on the transport of a charge package in a charge coupled device and on the simulation of the ESD ( Electro‐Static Discharge) in an MOS transistor. The CURRY package can also be used as a high quality kernel to which the user may add his own extensions by adding small pieces of Fortran code. The flexibility of this setup will be shown in the computation of the threshold voltage of an MOS transistor, in the computation of the I‐V curve of a diode in avalanche breakdown and in the computation of the open collector voltage of a bipolar transistor.

This paper intends to present a hydrodynamical model which describes the hole motion in silicon and couples holes and electrons.

The model is based on the moment method and the closure of the system of moment equations is obtained by using the maximum entropy principle (hereafter MEP). The heavy, light and split‐off valence bands are considered. The first two are described by taking into account their warped shape, while for the split‐off band a parabolic approximation is used.

The model for holes is coupled with an analogous one for electrons, so obtaining a complete description of charge transport in silicon. Numerical simulations are performed both for bulk silicon and a p‐n junction.

The model uses a linear approximation of the maximum entropy distribution in order to close the system of moment equations. Furthermore, the non‐parabolicity of the heavy and light bands is neglected. This implies an approximation on the high field results. This issue is under current investigation.

The paper improves the previous hydrodynamical models on holes and furnishes a complete model which couples electrons and holes. It can be useful in simulations of bipolar devices.

The results of the paper are new since a better approximation of the band structure is used and a description of both electron and hole behavior is present, therefore the results are of a certain relevance for the theory of charge transport in semiconductors.

An energy transport model has been numerically implemented in the device simulator HFIELDS. The transport parameters for the standard hydrodynamic model and the energy transport model are calibrated by means of DAMOCLES, a two‐dimensional Monte Carlo Boltzmann equation solver. We analyse the relative merits of these two models by comparing their predictions of the energy and velocity distributions for a bipolar transistor and a ballistic diode. In the cases presented, the hydrodynamic model is found to agree with the Monte Carlo results more closely than the energy transport model.

With decreasing vertical dimensions of the bipolar transistor (BJT), non‐local effects of nonuniform electron temperature should have a significant effect on the BJT characteristics. These effects can be simulated using a hydrodynamic (HD) model of the BJT, in which the equation of energy balance is added to the set of Poisson's and continuity equations.

An efficient numerical model of heterojunction bipolar transistor high frequency performance is proposed. The developed model is based on the ensemble Monte Carlo particle simulator. The validity and accuracy of the model are verified by comparing of the results of the model prediction with the experimental dates. The role of the thickness of the collector junction on the transistor cut‐off frequency is investigated and it is found that transistor cut‐off frequency as a function of the collector thickness has a maximum.

The effects of polysilicon emitter on the high frequency performance of bipolar transistors have been investigated numerically. The presence of polysilicon grain boundaries was found to slow down the response of the device. This resulted in a lower fT for polysilicon emitter bipolar transistors with a clean polysilicon/ mono‐crystalline silicon interface compared to conventional transistors with an identical emitter‐base junction depth. The interfacial oxide layer that could exist at the polysilicon/mono‐crystalline silicon interface can, depending on the relative thickness of the polysilicon and mono‐crystalline silicon emitter regions, either improve or deteriorate the high frequency performance of the device. For a mono‐crystalline silicon emitter region that is much thinner than the polysilicon emitter region, the lower the tunnelling probability of the interfacial oxide layer the better is the improvement in fT. However, if the thickness of the mono‐crystalline silicon emitter region is made larger with respect to the polysilicon emitter region, the converse can be true.