A Generalized Approach to Analysing a Class of Passively Soft-Switched PWM DC-DC Converters

In this paper, a generalised approach to the analysis of a class of passively soft-switched PWM DC-DC converters is presented. The circuit cell that gives this class of converters its passively soft-switched characteristics is first introduced. The use of this circuit cell to transform the basic hard switched converters (buck, boost, bucklboost, Cuk's, Sepic and Zeta) into their varied passively soft-switched PWM topologies is illustratively presented. A generalised analysis representative of all the soft-switched converter types in the class is carried out

GEOPLEX: GSSA and VSS models

This report describes some aspects of the theory of Variable Structure Systems (VSS). It starts with the state-of-the-art classical methods of control and evolves to a description based on average port Hamiltonian models. In the framework of GEOPLEX, VSS appears due to the fact that some of the plants of interest are controlled using power converters, which are systems, changing between several circuits topologies. In section 2, the basic ideas of Sliding Mode Control (SMC) for VSS are presented, and a somewhat detailed exposition of its application to the control of a power converter is given. Most of section 3 is unpublished material, describing some preliminary results about the relation between (generalized) averaging and the port Hamiltonian description. The fundamentals of State Space Averaging (SSA) and Generalized Space State Averaging (GSSA) are presented, and averaged port Hamiltonian models for second order power converters are introduced. There is a summary of some rigorous mathematical results about GSSA, and a relationship between the Hamiltonians of the GSSA models and the original Hamiltonian is established for systems with quadratic Hamiltonian functions

Sliding Mode Control of Quadratic Boost Converters Based on Min-Type Control Strategy

The paper deals with the control of a quadratic boost converter supplied by low-voltage energy sources, such as photovoltaic panels, fuel cells, or batteries. The control scheme consists of two control loops. A min-type controller governs the inner loop to force the current state of the nominal model to converge in a neighborhood of the equilibrium state. The external loop processes the output tracking error using an integrator, and it allows reconfiguring the converter's working point by changing the equilibrium state given in the input to the internal loop. This configuration assures both zero tracking error of the output voltage and robustness against load and input voltage variations and converter parameter uncertainties. The stability of the whole system is investigated using the hybrid system framework. The proposed control technique has been tested experimentally in a suitably developed (low-cost) setup, and the results show the effectiveness of the proposed approach

Development of a Step Down DC-DC Converter for Power Grid Energy Harvesting

This work contains an analysis of multiple topologies of DC-DC voltage buck con verters. The main goal of this Thesis is to study and design a functioning Step Down converter for capacitive coupling devices used for energy harvesting from the power AC grid. In order to achieve this goal, multiple topologies and circuits of this type of converter are studied and analysed, so that the requirements for the intended application are met. Since the input is obtained from the AC power grid and the output is connected to a supercapacitor, this results in a large input voltage (over 150V) and a low output voltage (between 1V to 3V), therefore the converter requires a step down voltage conversion ratio of around 130. The DC-DC converter should also have a large input impedance (around 50Mohm) to maximize the energy transferred from the power grid. This mode of operation is not common for regular inductance based DC-DC converters, making this a challenging problem. Moreover, since the amount of energy available from the capacitive coupling is very small, it is also necessary to develop a controller circuit that is capable of created a clock with a very low duty cycle while dissipating less than 50uW.Este trabalho visa analisar várias tipologias de conversores de tensão DC-DC deno minados conversores Buck. O principal objectivo desta Tese é estudar e projectar um conversor DC-DC abaixador de tensão para sistemas de acopelamento electromagnético capacitivo utilizada em aplicações de Energy Harvesting a partir da rede AC. De forma a cumprir este objectivo, várias tipologias são estudadas ao longo deste trabalho, de forma a cumprir as especificações exigidas. Uma vez que o sinal de entrada é obtido a partir da rede AC, e que o output está ligado a um supercondensador, isto faz com que a tensão de entrada seja elevado (Acima dos 150V) e a tensão de saída seja baixa (entre 1V e 3V), como tal o conversor precisa de um rácio de abaixamento bastante elevado de cerca de 130 vezes. O conversor DC-DC deve também ter uma impedância de entrada elevada (cerca de 50MOhm) por forma a maximizar a energia transferida da rede de energia. Estas condições de funcionamento não são habituais para conversores DC-DC indutivos, o que torna este um problema muito desafiante. Adicionalmente, uma vez que a energia disponivel devido ao acopelamento capacitivo é muito reduzida, é necessário desenvolver um circuito controlador capaz gerar um sinal de relógio com um duty cycle reduzido enquanto dissipa menos de 50uW de potência

Isolated Single-stage Power Electronic Building Blocks Using Medium Voltage Series-stacked Wide-bandgap Switches

The demand for efficient power conversion systems that can process the energy at high power and voltage levels is increasing every day. These systems are to be used in microgrid applications. Wide-bandgap semiconductor devices (i.e. Silicon Carbide (SiC) and Gallium Nitride (GaN) devices) are very promising candidates due to their lower conduction and switching losses compared to the state-of-the-art Silicon (Si) devices. The main challenge for these devices is that their breakdown voltages are relatively lower compared to their Si counterpart. In addition, the high frequency operation of the wide-bandgap devices are impeded in many cases by the magnetic core losses of the magnetic coupling components (i.e. coupled inductors and/or high frequency transformers) utilized in the power converter circuit. Six new dc-dc converter topologies are propose. The converters have reduced voltage stresses on the switches. Three of them are unidirectional step-up converters with universal input voltage which make them excellent candidates for photovoltaic and fuel cell applications. The other three converters are bidirectional dc-dc converters with wide voltage conversion ratios. These converters are very good candidates for the applications that require bidirectional power flow capability. In addition, the wide voltage conversion ratios of these converters can be utilized for applications such as energy storage systems with wide voltage swings

The design of front-end DC-DC converters of distributed power supply systems with improved efficiency and stability

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.Includes bibliographical references (leaves 181-184).by Loveday Haachitaba Mweene.Sc.D