This thesis deals with the time-domain analysis of switched linear networks and investigates inherent problems which have to be considered when analyzing this class of networks. Computer simulation requires the use of numerical methods and we focus on the transmission -line modelling technique (TLM) and the numerical inverse Laplace transform. A general approach based on the one-graph modified nodal description is given which allows the formulation of circuit equations of a TLM-modelled circuit by inspection. The numerical equivalence of TLM and trapezoidal rule has been found and a proof is given. A variable step size simulator has been developed based on the 4th order numerical inverse Laplace transform. The properties of this method are reviewed and its limitations are discussed. Simulation results are given to illustrate capabilities of the simulator.

The use of switched linear networks is prevalent in power processing systems such as dc-to-dc power converters. These converters provide regulated dc output power and are widely used in the power supplies for computers and peripherals. As with most systems where high performance is a criterion, the power converter is usually enclosed in a feedback loop. Feedback design usually entails the use of small signal (linear) models with linear feedback design techniques. There exists a large number of small signal models, but most of them are ad hoc. A describing function approach has previously been presented which determines the exact small signal frequency response of the converters. This method is now used to systematically derive circuit models for power converters. The aim of the work presented in this thesis is to model the nonlinear part of the switching converters which are simply the switches. This study is focused on the Pulse Width Modulation (PWM) class of converters. Majority of available models are not very accurate because they are averaged models. The aim of the new approach is to obtain accurate and simple model. A partial realization of this aim has been achieved; the new model is accurate over a very wide frequency range, but presently the parameters are rather complicated.

For many high-speed, high-performance circuits, purely differential inputs are needed. This project focuses on building high-speed voltage converters which can transfer a single-ended signal to a purely differential signal, or a differential input signal to a single-ended signal. Operational transconductance amplifier (OTAs) techniques are widely used in high-speed continuous-time integrated analog signal processing (ASP) circuits because resistors, inductors, integrators, buffers, multipliers and filters can be built by OT As and capacitors. Taking advantage of OT As, very-high-speed voltage converters are designed in CMOS technology. These converters can work in a frequency range from DC (OHz) up to lOOMHz and higher, and keep low distortion over a± 0.5V input range. They can replace transformers so that designing fully integrated differential circuits becomes possible. The designs are based on a MOSIS 2μm n-well process. SPICE simulations of these designs are given. The circuit was laid out with MAGIC layout tools and fabricated through MOSIS. The chip was measured at PSU and Intel circuit labs and the experimental results show the correctness of the designs.

Thesis (Ph. D.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 29, 2007) Includes bibliographical references.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Robert Ashton. Includes bibliographical references (p. 73-74). Also available online.

From the early days of HVDC system applications, the importance of mathematical modelling of the dynamics of Line Commutated Converter (LCC) HVDC systems has been appreciated. There are essentially two methodologies used to develop mathematical models of dynamic systems. One methodology is to define the properties of the system by the “laws of nature” and other well-established relationships. Basic techniques of this methodology involve describing the system’s processes using differential equations. This methodology is called “Deductive Modelling”. The other methodology used to derive mathematical models of a dynamic system is based on experimentation. Input and output signals from the original system are recorded to infer a mathematical model of the system. This methodology is known as “Inductive Modelling”. A review of the current state of the art of modelling LCC HVDC systems indicates that majority of the techniques utilized to develop mathematical models of LCC HVDC systems have used the “Deductive Modelling” approach. This methodology requires accurate knowledge of the ac systems and the dc system and involves complicated mathematics. In practice, it is nearly impossible to obtain accurate knowledge of the ac systems connected to LCC HVDC systems. The main aim of this thesis is to present an “Inductive Modelling” methodology to calculate the plant transfer functions of LCC HVDC systems. Due to the uncertain nature of the effective short circuit ratio of rectifier and inverter converter stations, generic ranges of parametric uncertainties of the developed plant transfer functions were determined. Based on the determined range of HVDC plant parametric uncertainty, Quantitative Feedback Theory (QFT) methodology was used to design the parameters of the LCC HVDC control system. The stability of the start-up and step responses for varying ac system conditions validated the “Inductive Modelling” technique and the QFT design methodology. The thesis presents the following, which are considered to be scientific advancements and contributions to the body of knowledge: · Novel LCC HVDC Step Response (HSR) equations were developed using an “Inductive Modeling” technique. · The range of parametric variations of the LCC HSR equations were determined for various rectifier and inverter ac system effective short circuit ratios. · The LCC HSR equations were used to develop the LCC HVDC plant transfer functions for various rectifier and inverter effective short circuit ratios. · The LCC HVDC plant transfer functions were utilized to design an LCC HVDC control system for varying ac system conditions using Quantitative Feedback Theory (QFT) methodology. The main contributions of this thesis relate to LCC HVDC systems. This thesis does not attempt to advance control theory however this thesis does apply existing classical control theory to LCC HVDC control systems. Index Terms: Line Commutated Converter, HVDC, inductive modelling, power system, transient analysis. / Thesis (Ph.D.)-University of KwaZlu-Natal, Durban, 2011.

This thesis presents the operational principles, and analysis, simulation. experimental results of a single-cell full-bridge high frequency (HF) transformer isolated DC-to-DC power converter with an inductive output filter controlled with a new gating scheme. A single-stage multi-cell HF transformer isolated AC-to-DC power converter with the same new gating scheme is designed and tested. The new gating scheme is implemented in a Field-programmable gate-array (FPGA) chip to generate the control gating signals for the DC-to-DC and AC-to-DC converters. The steady-state operation of the DC-to-DC converter controlled with the new gating scheme is analyzed using the equivalent circuits during different intervals of operation. Based on the operational analysis, a set of equations is derived to draw design curves. A design example of 5 kW, 580 V to 620 V input and 420 V output DC-to-DC converter is given to present the design procedure. PSPICE simulation and experimental results obtained from an experimental converter controlled with the FPGA are provided to verify the theoretical analysis, and design procedure. A systematical procedure for finding the parameters of the output RCD snubber circuit is also given. A 3 kW 3-cell 166 V to 260 V input 420 V output single-stage HF transformer isolated AC-to-DC multi-cell converter is designed and tested using a FPGA controller The new gating scheme is implemented on a Xilinx Spartan 11 FPGA chip using two digital pulse-width modulation (DPWM) approaches, the conventional DPWM module and the delay-line DPWM module. The simulation and experimental results are presented.

This thesis deals with hybrid phase modulated converter with inductive output filter as well as capacitive output filter. The operational principles, detailed steady-state analysis for different modes of operation, detailed design procedure with an example. simulation and experimental results are presented for HPMC with inductive output filter. HPMC with inductive output filter has reduced output filter requirements and maintains ZVS for wide line and load variations. This converter suffers from duty cycle loss and output rectifier ringing requiring secondary-side snubbers and higher voltage rated rectifier diodes. To overcome this problem, a hybrid phase modulated DC-DC converter with a capacitive output filter is proposed. Different modes of operation of the proposed converter are identified and a detailed steady-state analysis for these modes of operation is presented. A design example of 200 W, 22 V to 41 V input voltage and 350 V output voltage hybrid phase modulated converter with inductive and capacitive output filter is given to present the design procedure. Simulation and experimental results obtained from the laboratory prototype are provided to verify the performance of the converter. A comparison of performance between the HPMC with inductive and capacitive output filters with standard phase-shifted PWM full bridge converter are also presented.

Thesis (Ph. D.)--Ohio University, August, 1993. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, June, 1997. / Title from PDF t.p.