The main goal of this thesis is to develop an active thermal management control scheme for multi-phase current mode buck converters in order to improve the long term reliability of the converters. A thermal management unit (TMU) with independent linear compensators for the thermal loops is incorporated into the existing digital controller to regulate the current through each phase so that equal temperature distribution is achieved across all phases. A lumped parameter thermal model of the multi-phase converter is built as the basis of the TMU. MATLAB simulation results are used to verify the TMU concept. Experimental results from a digitally controlled 12 V to 1 V, 50 A, 250 kHz four-phase peak current mode buck converter demonstrate the effectiveness of the proposed thermal management technique in the presence of uneven air flow. The steady-state performance, dynamic transient load performance, effect of gate drive voltage and efficiency measurements are investigated and discussed.

Distributed generation that utilizes 5-10kW Solid Oxide Fuel Cells requires power electronics to optimize the overall system efficiency while reducing the cost. The Adaptive Energy Zero-Voltage-Switching Phase-Shift-Modulated Full-Bridge (AE-ZVS-PSM-FB) topology meets these criteria under all loading conditions, but suffers from complexity associated with an analog control implementation. This thesis presents a novel Look-Up-Table (LUT) based digital controller required for such converter. The applied design approach also reduces the design time and controller requirements, which in turn decreases the overall system cost. Steady-state analysis for the AE-ZVS-PSM-FB converter is performed using a piece-wise equivalent circuit model. This analysis is used to verify the LUT concept that forms the basis for the proposed LUT-based digital controller. The proposed LUT-based digital control algorithm is developed and verified using Field Programmable Gate Array (FPGA) Logic platform. Design procedures and operational function under steady state and step change conditions are presented. Simulation results demonstrate the LUT concept in the AE-ZVS-PSM-FB converter, and the simplicity of the proposed LUT-based digital controller in producing the expected switching sequence. Simulation results were also produced showing successful dynamic response of LUT-based digital controller interconnected with the converter under different operating conditions. A Xilinx FPGA demonstration board was used to generate experimental switching sequence results to demonstrate the simplicity of the proposed controller. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2007-09-25 10:26:39.909

Power electronic systems have been widely used in the electrical power processing for applications with power levels ranging from less than one watt in battery-operated portable devices to more than megawatts in the converters, inverters and rectifiers of the utility power systems. These systems typically involve the passive elements such as inductors, capacitors, and resistors, the switching electronic components such as IGBTs, MOSFETS, and diodes, and other electronic circuits. Multifrequency averaging is one of the widely used modeling and simulation techniques today for the analysis and design of power electronic systems. This technique is capable of providing the average behavior as well as the ripple behavior of power electronic systems. This work begins with the extension of multifrequency averaging to represent uniformly sampled PWM converters. A new multifrequency averaging method of solving an observed issue with model stability is proposed and validated. Multifrequency averaging can also be applied to study the instability phenomenon in power electronic systems. In particular, a reduced-order multifrequency averaging method, along with a genetic algorithm based procedure, is proposed in this work to estimate the regions of attraction of power electronic converters. The performance of this method is shown by comparing the accuracy and efficiency with the existing methods. Finally, a new continuous-time multifrequency averaging method of representing discrete-time systems is proposed. The proposed method is applied to model digitally controlled PWM converters. Simulation and hardware results show that the proposed method is capable of predicting the average behavior as well as the ripple behavior of the closed-loop systems. Future research in the area of multifrequency averaging is proposed.

Digitally-controlled, high power universal telecommunication power supply modules have been developed. In this work, the converter control strategy, and its design and implementation first, by means of parallel-operated, dual, 8-bit microcontrollers, and then by using a high processing power digital signal processor (DSP) have been emphasized. The proposed dual-processor based digital controller provides an extended operating output voltage range of the power supplies, user programmable current limit setting, serial communication based active load current sharing with automatic master-slave selection among parallel-operated modules, user selectable number of back-up battery cells, programmable temperature compensation curves, and automatic derating without extra hardware requirement. Overload and output short-circuit protection features are also controlled by software. One of the processors in the digital controller is employed for user interface purposes such as long term records, display, and alarm facilities, and remote control, which are inherently slow processes. The fast processing speed required by output voltage setting, current limit, and load current sharing however is to be fulfilled by a second processor dedicated to the adjustment of output voltages of modules. Tight dynamic load regulation requirement of a telecommunication power supply has been fulfilled by a 150 MIPS DSP, in place of a low cost, 8-bit microcontroller. The implemented digitally-controlled, 1.8 kW, 0-70V telecommunication power supplies have been tested successfully in several locations in the field.

Content removed due to copyright Conference Proceedings I R. P. Fisk and S. M. Hasan, “Analysis of Internally-Generated Noise in Bandgap References,” in Proc. Electronics New Zealand Conf., Christchurch, New Zealand, Nov. 2006, pp. 18-23. Conference Proceedings II R. P. Fisk and S. M. Hasan, “Incremental Delta-Sigma Modulators for Temperature Sensing Applications,” in Proc. Int. Conf. Mechatronics and Machine Vision in Practice, Auckland, New Zealand, Dec. 2008, pp. 63-67. Conference Proceedings III R. P. Fisk and S. M. Hasan, “Low-Cost Temperature Sensor on a Modern Submicron CMOS Process,” in Proc. Electronics New Zealand Conf., Otago, New Zealand, 2009, pp. 43-48. / Digital control systems can be found performing a wide range of duties throughout modern society. These systems demand accurate, low cost interfaces to physical parameters of interest, one of the most common being temperature. A ‘smart’ sensor takes advantage of modern integrated circuit technology to create a sensor and analog-to-digital converter on the same silicon chip. Smart temperature sensors are widely available offering simple digital interfaces, high reliability, low power consumption and low cost. The primary weakness of these devices is the low inherent accuracy of on-chip thermal sensors. This thesis presents a smart thermal sensor design that improves upon current technology by employing a modern 0.13μm CMOS process and circuit-level techniques to reduce sensor size and power consumption while increasing digital converter resolution. Data is presented that shows uncalibrated sensor accuracy can be increased by using correlated device characteristics to compensate for random inter-device variation. The research findings guide the construction of future smart thermal sensors with uncalibrated accuracy levels exceeding that of any currently available design.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This master thesis performs the analysis and design of an AC-DC converter with high voltage gain to be used to supply a magnetron in a microwave generation system. The converter topology is chosen so as to enable input power control, operation with high power factor and with possibility of wide variation in the effective voltage input, so that the converter operates in the universal 100-240 V effective voltage range. The topology consists of a controlled type half-bridge rectifier at the entrance, responsible for the current control and diferencial voltage balance on the DC link capacitors and an isolated DC-DC half-bridge converter with high voltage gain, which operates with a fixed duty cycle. The design of passive and active elements of AC-DC converter are presented and the discrete control to implement a prototype that operates with input power up to 800 W is performed. The controllers are implemented in a low-cost 32-bit and fixed point arithmetic microcontroller. Experimental results to validate the designed controllers are obtained for various power reference values, evaluating the converter for practically all operational range. / A presente dissertação de mestrado realiza a análise e o projeto de um conversor CA-CC de elevado ganho de tensão para ser utilizado na alimentação de um magnetron em um sistema de geração de micro-ondas. A topologia do conversor é escolhida de forma a possibilitar o controle da potência de entrada, operação com elevado fator de potência e com possibilidade de grande variação na tensão eficaz da entrada, de forma que o conversor opere na faixa de tensão universal eficaz de 100 a 240 V. A topologia é composta por um retificador meia-ponte na entrada, responsável pelo controle de corrente e equilíbrio das tensões no barramento CC, e por um conversor CC-CC meia ponte isolado na saída com elevado ganho de tensão, que opera com razão cíclica fixa. O projeto dos elementos passivos e ativos do conversor CA-CC são apresentados e o controle discreto para implementação de um protótipo que opera com potência de entrada de até 800 W é realizado. Os controladores são implementados em um microcontrolador de baixo custo de 32 bits e operação aritmética de ponto fixo. Resultados experimentais para validação dos controladores projetados são obtidos, para vários valores de referência de potência, avaliando o conversor para praticamente toda sua faixa de operação.

Orientador: Carlos Alberto Canesin / Banca: Fabio Toshiaki Wakabayashi / Banca: Luiz Carlos de Freitas / Resumo: Este trabalho apresenta o desenvolvimento e implementação de um emulador para a característica estática de saída (Tensão versus Corrente) equivalente àquela de fontes de energia com células combustível. O emulador apresenta como vantagens, em relação à aquisição de uma FC, o baixo custo, o reduzido espaço físico e a flexibilidade via software para a implementação de diversas características baseadas em diferentes tipos de células combustível. Neste sentido, o emulador proposto permite a realização de ensaios preliminares durante a fase de projeto e os testes dinâmicos dos subsistemas de condicionamento de energia, sem a necessidade do acoplamento com o sistema de geração à células combustível, reduzindo-se os custos associados a estes testes laboratoriais. O emulador proposto consiste em um conversor Buck isolado "Full-Bridge", com potência de saída de 2kW e alimentação via barramento de 400VCC, permitindo a emulação da característica nominal de saída de um conjunto de células tipo PEM ("Proton Exchange Membrane" - Membrana de Troca Protônica), em uma faixa de tensão de saída variando entre 32VCC e 72VCC, dependendo da corrente drenada pela carga. O circuito principal de controle é realizado através... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work presents a design and implementation of an emulator to the static output characteristic (Voltage versus Current) that is similar to Fuel Cell generators. There are many advantages on using the Fuel Cell emulator. The emulator is cheaper, smaller and more flexible than the real Fuel Cell systems, because it is possible to emulate different characteristics through the use of a computer. In this context, a Fuel Cell emulator is proposed in this work in order to allow laboratory testes in the power conditioning system during its design and development stage. The proposed emulator is an insulated "Full-Bridge" converter with "Buck" operation, 2kW output power and 400VCC input voltage. This emulator achieves the output characteristic of a PEM (Proton Exchange Membrane) Fuel Cell stack with output voltage range of 32VCC to 72VCC, depending on the output current. The main control circuit is based on FPGA (Field Programmable Gate Array) and VHDL (Very High Speed Integrated Circuit Hardware Description Language) language. The experimental results demonstrate that the proposed emulator achieves the output static characteristic of the PEMFC Fuel Cell System and this output characteristic can be easily modified in order to obtain another desirable static... (Complete abstract click electronic access below) / Mestre

Resumo: Este trabalho trata da análise, desenvolvimento e implementação de um estágio Pré- Regulador Retificador Boost de alto fator de potência, para servir como fonte de alimentação para sistemas de iluminação fluorescente multi-lâmpadas, com potência de até 1.200 watts e com índices de qualidade tanto para a fonte de alimentação em corrente alternada quanto para o sistema de iluminação. Este conversor será controlado de forma digital, através da técnica dos valores médios instantâneos da corrente de entrada, desenvolvido através da linguagem de descrição de hardware VHDL (VHSIC HDL - Very High Speed Integrated Circuit Hardware Description Language) e implementado em um dispositivo FPGA (Field Programmable Gate Array) Spartan 3. Neste trabalho são apresentadas análises matemáticas, para a obtenção das funções de transferência pertinentes ao projeto dos compensadores, onde será aplicada uma metodologia de projeto capaz de projetar estes compensadores utilizando os diagramas de Bode, de módulo e de fase, e ainda contemplar as influencias dos dispositivos A/D, D/A e do processador digital de sinais. Isto eliminará os erros presentes nos projetos via aproximação e permitirá a diminuição das taxas de aquisição necessárias. O projeto é simulado e validado através da plataforma MatLab/Simulink, onde são apresentados resultados para o regime permanente e para transitórios de carga e da tensão de alimentação. Além disso, o controle do conversor através da linguagem VHDL, usando o modelo comportamental num estilo de projeto topdown, é apresentado e também validado através de simulação. Ademais, um sucinto estudo dos reatores eletrônicos convencionais é apresentado, com o intuito de sevir como base para o desenvolvimento de um filtro capaz de barrar as componentes em ca da corrente que circula entre o capacitor de saída... (Resumo completo clicar acesso eletrônico abaixo) / Abstract: This work presents the analysis, development and implementation of a single-phase power factor correction (PFC) pre-regulator rectifier, based on boost circuit, to act as a power supply for 1.200 watts multi-lamp fluorescent systems. The converter's digital control will be implemented using the average current mode control, based on VHDL language (VHSIC HDL - Very High Speed Integrated Circuit Hardware Description Language) and using a FPGA (Field Programmable Gate Array) device. In this work, the mathematical analyses of the converter's model are developed in order to obtain the proper transfer functions to design voltage and current digital compensators. The methodology applied at the digital design is capable to deal with the Bode diagrams and incorporate the analog to digital converter, the digital to analog converter and the digital signal processor, eliminating the uncertainties involving approximation methodologies and minimizing the necessity of high level of acquisition rates. This project is evaluated through MatLab/Simulink, showing results for steady-state operation and dynamics in order to analyze the converter's response. Moreover, the converter's digital control is based on VHDL language, using the behavioral modeling in a top-down project style, which is presented and validated through simulation results. In addition, the behavior of the conventional electronic ballasts are presented in order to help in the development of a filter, capable to impede the circulation of the AC components of the ballast current throught the feeding link, guaranteeing the continuous current conduction, among the boost capacitor and the electronic ballasts. Finally, this work presents the laboratorial development of this PFC with digital control, where the prototype was evaluated through experimental results. / Orientador: Carlos Alberto Canesin / Coorientador: Fabio Toshiaki Wakabayashi / Banca: Claudio Kitano / Banca: Arnaldo José Perin / Mestre

Este trabalho apresenta uma contribuição à área de controle de sistemas multivariáveis com a utilização de lógica fuzzy. Esta proposta consiste no desenvolvimento de um sistema de controle com duas entradas e duas saídas. São apresentados os principais aspectos estruturais e tecnológicos do sistema desenvolvido, assim como os fundamentos da estratégia de controle fuzzy, incluindo suas principais derivações, a saber, Fuzzy-PD, Fuzzy-Incremental, Fuzzy-PD+I. Ainda, foi considerada a utilização de uma topologia Fuzzy-P+I que se destaca pelo número reduzido de regras. Estratégias de controle descentralizado são consideradas. As estruturas de controle são implementadas no hardware CompactRIO R, em conjunto com o software de desenvolvimento LabVIEW R, com o objetivo de controlar nível e temperatura de fluido em um reservatório de uma planta didática. / This work presents a research proposal for the control of multivariable systems using fuzzy logic. This proposal consists in developing a control system with two inputs and two ouputs. It is presented the main structural and technological aspects of the developed system as well as the fundamentals of fuzzy control, including its main derivations, namely Fuzzy-PD, Fuzzy-Incremental, Fuzzy-PD+I. Still, it is considered the use of a fuzzy-P+I topology, which stands for the reduced number of rules. Fuzzy-P+I. Decentralized control strategies are considered. The control structures are implemented in the hardware CompactRIO R together with the LabVIEW R evelopment software, with the aim of controlling the fluid level and temperature in a tank of the didactic plant.

Thesis (MTech(Electrical Engineering))--Cape Peninsula University of Technology, 2010 / Optimal control of fermentation processes is necessary for better behaviour of the process in order to achieve maximum production of product and biomass. The problem for optimal control is a very complex nonlinear, dynamic problem requiring long time for calculation Application of decomposition-coordinating methods for the solution of this type of problems simplifies the solution if it is implemented in a parallel way in a cluster of computers. Parallel computing can reduce tremendously the time of calculation through process of distribution and parallelization of the computation algorithm. These processes can be achieved in different ways using the characteristics of the problem for optimal control. Problem for optimal control of a fed-batch, batch and continuous fermentation processes for production of biomass and product are formulated. The problems are based on a criterion for maximum production of biomass at the end of the fermentation process for the fed-batch process, maximum production of metabolite at the end of the fermentation for the batch fermentation process and minimum time for achieving steady state fermentor behavior for the continuous process and on unstructured mass balance biological models incorporating in the kinetic coefficients, the physiochemical variables considered as control inputs. An augmented functional of Lagrange is applied and its decomposition in time domain is used with a new coordinating vector. Parallel computing in a Matlab cluster is used to solve the above optimal control problems. The calculations and tasks allocation to the cluster workers are based on a shared memory architecture. Real-time control implementation of calculation algorithms using a cluster of computers allows quick and simpler solutions to the optimal control problems.