Conversores CC-CC não isolados gerados pela integração entre células de capacitores chaveados e células convencionais de comutação

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2016.Este trabalho apresenta o estudo da integração entre células a capacitor chaveado e células convencionais de comutação. Como resultado, obtêm-se duas células híbridas de comutação, as quais geram uma família de conversores CC-CC híbridos não isolados. Uma célula é denominada de célula passiva de comutação e a outra de célula ativa de comutação. Cada uma gera três conversores: um Buck, um Boost e um Buck-Boost. As duas células híbridas de comutação, juntas, geram seis conversores CC-CC não isolados, todos apresentados nesta Dissertação. Características de ganho no MCC e MCD (quando aplicável), ganho generalizado, análise por espaço de estados para obtenção dos valores médios das variáveis relevantes do circuito e expansão dessa análise com o objetivo de descrever os esforços de tensão e corrente dos componentes do estágio de potência foram realizados para todas as topologias estudadas. A fim de validar experimentalmente a teoria abordada, dois protótipos foram desenvolvidos, um para cada célula híbrida de comutação, cujo objetivo é a validação das seis topologias (três de cada célula de comutação) estudadas. Testes experimentais proporcionaram a validação do ganho estático de todas as topologias e, para a topologia Buck de cada célula (topologia utilizada para dimensionamento e construção dos protótipos), ensaios de eficiência e regulação também foram realizados para tensão de entrada de 600 V e potência nominal de 1 kW.Abstract: This work presents a study on the integration of switched capacitor cell sand a conventional commutation cell. As a result, two hybrid commutation cells are obtained, which generate a family of DC-DC non isolated hybrid converters. One cell is denominated passive commutation cell and the other one, active commutation cell. Each onegenerates three converters: a Buck, a Boost and a Buck-Boost type.Together, these two hybrid commutation cells generate six converters, all of them are presented in this dissertation. Characteristics of gain inCCM and DCM (if when applicable), generalized gain, steady state analysis to obtain the relevant steady values of the circuit and an expansion from this analysis with the objective of describe the voltage and current stresses on all power components were realized for all topologies. In order to experimentally evaluate the theory, two prototypes were developed, one for each hybrid commutation cell,whose goal is validate the six topologies (three of them from each commutation cell) studied. Experimental tests provided the static gainvalidation to all topologies and, for the Buck converter of each cell (topology used to develop the prototypes), efficiency and regulation tests are also reported for a 600 V of input voltage and 1 kW of ratedpower

Performance comparison between SiC and Si inverter modules in an electrical variable transmission application

This paper evaluates the performance of Silicon Carbide MOSFET and Silicon IGBT modules in a threephase inverter for Electrical Variable Transmission systems. For this purpose, two practical inverter setups were developed and compared. An increase of several percentage points is visible over the entire operating range for the Silicon Carbide prototype. The total energy efficiency increased by 3.7% for the rotor and by 11.2% for the stator, for the same test conditions

Non-Isolated High Step-Down DC-DC Converters for LVDC Application

In the early stage, AC prevailed over DC mainly because of the following reason: the presence of the low frequency transformer, which enables to step-up AC voltages for transmission purposes, and which enabled to generate the electricity centrally, far from the main economical and populational centers (AC offered lower losses for longer distances at that time). From that point on, AC was massively used to implement our today's generation, transmission and distribution systems. Nowadays, however, due to the advent of renewable energy sources in our modern grid, DC voltage is proving to be an alternative for our next generation grid design. The main DC energy technologies available and being introduced in the grid are the following: photovoltaics, batteries, fuel cells, super capacitors, among others. To integrate these technologies in a DC system, power electronic converters are essential to adjust and regulate the voltage levels accordingly; to control and adjust the power flow; to maximize the energy generation, e.g. maximum power point tracking in photovoltaics; to guarantee grid stability, e.g. voltage balancer converters; and for safe operation and protection, e.g. in DC circuit breakers. All the applications mentioned above are based on power electronic converters and, therefore, these devices are the breakthrough technology for massive DC grid penetration in our generation, transmission and distribution systems. In the DC world, different applications require different converter specifications and structures. The DC-link voltages of these systems are being implemented in a broad range e.g. between 48-800 V. Additionally, low voltage/low power equipment's are massively present in the grid. Therefore, high step-down DC-DC conversion is required to comply with these voltage profiles. Different strategies to step-down voltages can be used to achieve systems requirement, e.g. application of high frequency isolated transformers, coupled-inductor techniques, voltage/current multiplier/divider cells, to name a few. Isolated topologies and topologies that implement coupled-inductor techniques are able to achieve high ratios by selecting the proper transformer/coupled-inductor winding ratio. However, these techniques present high magnetic complexity. To achieve high ratios without the implementation of transformer and coupled-inductor techniques, the voltage/current multiplier/divider cells mentioned above are used. These techniques are investigated in this thesis. The introduction of these strategies increase the power stage complexity and component part count of the circuits. Therefore, a careful analysis is important to maximize the performance of these converters. The main objective of this thesis is to propose new solutions for DC-DC conversion with high step-down voltage capability for applications in, e.g. industrial and residential systems, datacenters, electric vehicles, aircrafts, among others. To do so, converters with high step-down capability applying voltage and current multiplier/divider cells are the main topic tackled in this thesis. As previously mentioned, converters that apply these techniques often involve a high power stage complexity and component part count. To fully address the advantages of these converters, it is important to evaluate the switch technologies available on the market, as for instance Silicon and Gallium Nitride semiconductors, and their performance in highly complex circuits. Gallium-Nitride semiconductors are proven to have better theoretical characteristics compared to Silicon. These devices are, therefore, theoretically and practically compared to each other in some of the high step-down converters proposed in this thesis and conclusions related to their overall performance are discussed. This thesis proposes 12 new converters and the high step-down capability of each of them is evaluated. These converters are based on multiplier/divider cells and the performance of Silicon and Gallium Nitride technologies applied in these circuits is addressed. There is a strong emphasis on the prototype development and practical validation of the proposed converters. Discussions on the circuit's performance are shown together with a comparison between the proposed solutions and state-of-the-art converters, showing their benefits and drawbacks. In the end, it has been proved that, with a careful theoretical analysis, the correct implementation of voltage divider cells and converter validation, a high step-down DC-DC conversion operating with satisfactory performance is obtained, enabling its applications in the next generation of power electronics-based DC grids.status: publishe

Gallium-Nitride Semiconductor Technology and Its Practical Design Challenges in Power Electronics Applications: An Overview

status: publishe

Review on Building-Integrated Photovoltaics Electrical System Requirements and Module-Integrated Converter Recommendations

© 2019 by the authors. Since building-integrated photovoltaic (BIPV) modules are typically installed during, not after, the construction phase, BIPVs have a profound impact compared to conventional building-applied photovoltaics on the electrical installation and construction planning of a building. As the cost of BIPV modules decreases over time, the impact of electrical system architecture and converters will become more prevalent in the overall cost of the system. This manuscript provides an overview of potential BIPV electrical architectures. System-level criteria for BIPV installations are established, thus providing a reference framework to compare electrical architectures. To achieve modularity and to minimize engineering costs, module-level DC/DC converters preinstalled in the BIPV module turned out to be the best solution. The second part of this paper establishes converter-level requirements, derived and related to the BIPV system. These include measures to increase the converter fault tolerance for extended availability and to ensure essential safety features.status: publishe

Novel Step-Down DC–DC Converters Based on the Inductor–Diode and Inductor–Capacitor–Diode Structures in a Two-Stage Buck Converter

This paper explores and presents the application of the Inductor–Diode and Inductor-Capacitor-Diode structures in a DC–DC step-down configuration for systems that require voltage adjustments. DC micro/picogrids are becoming more popular nowadays and the study of power electronics converters to supply the load demand in different voltage levels is required. Multiple strategies to step-down voltages are proposed based on different approaches, e.g., high-frequency transformer and voltage multiplier/divider cells. The key question that motivates the research is the investigation of the aforementioned Inductor–Diode and Inductor–Capacitor–Diode, current multiplier/divider cells, in a step-down application. The two-stage buck converter is used as a study case to achieve the output voltage required. To extend the intermediate voltage level flexibility in the two-stage buck converter, a second switch was implemented replacing a diode, which gives an extra degree-of-freedom for the topology. Based on this modification, three regions of operation are theoretically defined, depending on the operational duty cycles δ2 and δ1 of switches S2 and S1. The intermediate and output voltage levels are defined based on the choice of the region of operation and are mapped herein, summarizing the possible voltage levels achieved by each configuration. The paper presents the theoretical analysis, simulation, implementation and experimental validation of a converter with the following specifications; 48 V/12 V input-to-output voltage, different intermediate voltage levels, 100 W power rating, and switching frequency of 300 kHz. Comparisons between mathematical, simulation, and experimental results are made with the objective of validating the statements herein introduced

Novel Step-Down DC–DC Converters Based on the Inductor–Diode and Inductor–Capacitor–Diode Structures in a Two-Stage Buck Converter

© 2019 MDPI AG. All rights reserved. This paper explores and presents the application of the Inductor-Diode and Inductor-Capacitor-Diode structures in a DC-DC step-down configuration for systems that require voltage adjustments. DC micro/picogrids are becoming more popular nowadays and the study of power electronics converters to supply the load demand in different voltage levels is required. Multiple strategies to step-down voltages are proposed based on different approaches, e.g., high-frequency transformer and voltage multiplier/divider cells. The key question that motivates the research is the investigation of the aforementioned Inductor-Diode and Inductor-Capacitor-Diode, current multiplier/divider cells, in a step-down application. The two-stage buck converter is used as a study case to achieve the output voltage required. To extend the intermediate voltage level flexibility in the two-stage buck converter, a second switch was implemented replacing a diode, which gives an extra degree-of-freedom for the topology. Based on this modification, three regions of operation are theoretically defined, depending on the operational duty cycles δ 2 and δ 1 of switches S 2 and S 1 . The intermediate and output voltage levels are defined based on the choice of the region of operation and are mapped herein, summarizing the possible voltage levels achieved by each configuration. The paper presents the theoretical analysis, simulation, implementation and experimental validation of a converter with the following specifications; 48 V/12 V input-to-output voltage, different intermediate voltage levels, 100 W power rating, and switching frequency of 300 kHz. Comparisons between mathematical, simulation, and experimental results are made with the objective of validating the statements herein introduced.status: Published onlin

Fuse-Based Short-Circuit Protection of Converter Controlled Low-Voltage DC Grids

status: publishe

Conversion Efficiency of the Buck Three-level DC-DC Converter in Unbalanced Bipolar DC Microgrids

This article evaluates the power conversion efficiency of the buck three-level dc-dc converter, when operating in unbalanced bipolar dc microgrids. Bipolar dc microgrids adopt a positive, neutral, and negative wire to double the power transfer capability, reduce conduction losses, and provide two voltage levels. Additional converters are however required to balance the pole-to-neutral voltages in the presence of unbalanced loading conditions. Previous work has shown that the buck three-level dc-dc converter features voltage balancing capability and can serve, at the same time, as an interface for battery storage and photovoltaic systems for example. Nevertheless, available conversion loss models are only valid for balanced loading conditions. Therefore, this article derives a conversion loss model for a buck three-level dc-dc converter, also valid in unbalanced conditions. The model is decomposed in balanced and unbalanced components in order to separate losses arising in balanced and unbalanced conditions. Furthermore, the model accounts for nonideal common-mode currents as experimental results will reveal that they have a profound impact on the conversion efficiency in unbalanced and balanced conditions.keywords: DC-DC power convertors;distributed power generation;losses;poles and towers;power conversion;wires (electric);pole-to-neutral voltages;nonideal common-mode currents;negative wire;neutral wire;positive wire;power transfer capability;unbalanced bipolar DC microgrids;buck three-level dc-dc converter;power conversion efficiency;Inductors;Microgrids;Modulation;Steady-state;Voltage control;Batteries;Load modeling;Bipolar dc microgrid;common-mode current;dc?dc power conversion;energy storage;power distributionstatus: publishe