A Variable-Structure Variable-Order Simulation Paradigm for Power Electronic Circuits

Solid-state power converters are used in a rapidly growing number of applications including variable-speed motor drives for hybrid electric vehicles and industrial applications, battery energy storage systems, and for interfacing renewable energy sources and controlling power flow in electric power systems. The desire for higher power densities and improved efficiencies necessitates the accurate prediction of switching transients and losses that, historically, have been categorized as conduction and switching losses. In the vast majority of analyses, the power semiconductors (diodes, transistors) are represented using simplified or empirical models. Conduction losses are calculated as the product of circuit-dependent currents and on-state voltage drops. Switching losses are estimated using approximate voltage-current waveforms with empirically derived turn-on and turn-off times

Modeling and Simulation in Engineering

The general aim of this book is to present selected chapters of the following types: chapters with more focus on modeling with some necessary simulation details and chapters with less focus on modeling but with more simulation details. This book contains eleven chapters divided into two sections: Modeling in Continuum Mechanics and Modeling in Electronics and Engineering. We hope our book entitled "Modeling and Simulation in Engineering - Selected Problems" will serve as a useful reference to students, scientists, and engineers

International Workshop on Finite Elements for Microwave Engineering

When Courant prepared the text of his 1942 address to the American Mathematical Society for publication, he added a two-page Appendix to illustrate how the variational methods first described by Lord Rayleigh could be put to wider use in potential theory. Choosing piecewise-linear approximants on a set of triangles which he called elements, he dashed off a couple of two-dimensional examples and the finite element method was born. … Finite element activity in electrical engineering began in earnest about 1968-1969. A paper on waveguide analysis was published in Alta Frequenza in early 1969, giving the details of a finite element formulation of the classical hollow waveguide problem. It was followed by a rapid succession of papers on magnetic fields in saturable materials, dielectric loaded waveguides, and other well-known boundary value problems of electromagnetics. … In the decade of the eighties, finite element methods spread quickly. In several technical areas, they assumed a dominant role in field problems. P.P. Silvester, San Miniato (PI), Italy, 1992 Early in the nineties the International Workshop on Finite Elements for Microwave Engineering started. This volume contains the history of the Workshop and the Proceedings of the 13th edition, Florence (Italy), 2016 . The 14th Workshop will be in Cartagena (Colombia), 2018

Controlling Photon and Ion Fluxes in Low Pressure Low Temperature Plasmas

Low temperature plasmas are widely used in both industry and everyday life, from fluorescent lighting, water purification to important processes in semiconductor industry fabricating electronic devices. In most of these applications, the flux of various energetic species generated by low temperature plasmas are the main promoter of necessary reactions facilitating the applications, by efficiently delivering energy for chemical reactions at molecular level. For example, in the process of plasma etching for semiconductor material processing, fluxes of radicals and ions can selectively react with material on the surface of the wafer, creating surface structures on the order of 10s of nm over the surface area of 103 cm-3. In the work of this thesis, the possibility of gaining a better understanding at controlling those fluxes is explored numerically using a two-dimensional plasma equipment model. In semiconductor industry, control of ion fluxes and ion energy distribution is critical to optimizing fabrication process and pushing the limit of Moore’s law. In this thesis, a unconventional tri-frequency capacitively coupled plasma (CCP) is investigated for scaling of ion fluxes and energy over power of individual frequencies. Compared with the conventional single-frequency and state-of-the-art dual-frequency CCP, we discovered that additional control of ion energy distribution can be achieved by the power of two lower frequencies. Ion fluxes scale positively with increasing power at all frequencies, and are more sensitive to low frequency power. Vacuum-Ultra-Violet (VUV) photon fluxes are also discovered to have important effect during plasma etching, such that controlling of VUV photon fluxes could potentially benefit to process optimization. This work studied dynamics of a low pressure inductively coupled plasma (ICP), trying to develop approaches of separate controlling VUV and ion fluxes. It was discovered that the ratio of VUV and ion flux, β, can be controlled by pressure, gas mixture and even surface conditions of the reactor wall. β can also be a function of duty cycle in pulsed ICP, caused by the customized electron energy distribution facilitated by the pulse power. Pulsed ICP has been widely studied for its unique tunability of electron energy distribution. Normally operating in radio frequency, power delivery of ICP can be sensitive to the matching circuit of the system. In this thesis, the dynamics of a pulsed ICP is investigated against the matching network. Instead of considering power mismatch as limiting factor, a deliberately tuned off-match condition is used to control the plasma density of a pulsed ICP. Both experimental and computational results are reported to observe instantaneous match time changes with configuration of matching circuit. Pulsed ICP that matches at a later time exhibits delayed density rise time with a larger final density. Low temperature plasma source are also investigated as a device for chemical analysis. A microwave excited microplasma, operated at several watts, is generated in dielectric cavities of hundreds of microns as ionization source for a novel concept of mass spectrometer. VUV photon fluxes produced from such microplasma source are then used to ionize samples for spectrometry. Result shows that the power efficiency of VUV emission is less than 1% and saturates as power increases. The VUV spectra can be individually tuned by adding Penning gas in the mixtures.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144041/1/tianpeng_1.pd