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High voltage DC/DC converter for offshore wind applicationZhou, Yao January 2015 (has links)
With the increasing interest in offshore wind power, the related technologies, including HVDC networks, are gaining similar levels of attention. For large scale wind farms far from shore, high voltage DC transmission can provide several advantages over traditional high voltage AC transmission. This thesis focuses on DC/DC converters, a core part of the HVDC network, especially for use in the high voltage, high power and offshore wind environment. The thesis examines a wide range of possible DC/DC converter topologies for the application. Different topologies are compared and evaluated in detail for use in a high power situation. Based on these results, three DC/DC converter topologies are selected for more detailed modelling. The simulation processes and results are presented in the thesis, which reveals the limitations and behaviour of the topologies when they are used at the MW level. In addition, the high power semiconductor switching devices are discussed and evaluated for each topology. To assess the suitability of the DC/DC converter topologies in the offshore wind application, the selected converter topologies are also analysed and modelled combined with a PMSG wind turbine. Finally, a down-scaled DC/DC converter prototype is built to verify the analysis and simulation results.
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Wide input range DC-DC converter with digital control schemeHarfman Todorovic, Maja 12 April 2006 (has links)
In this thesis analysis and design of a wide input range DC-DC converter is proposed along with a robust power control scheme. The proposed converter and its control is designed to be compatible to a fuel cell power source, which exhibits 2:1 voltage variation as well as a slow transient response. The proposed approach consists of two stages: a primary three-level boost converter stage cascaded with a high frequency, isolated boost converter topology, which provides a higher voltage gain and isolation from the input source. The function of the first boost converter stage is to maintain a constant voltage at the input of the cascaded DC-DC converter to ensure optimal performance characteristics with high efficiency. At the output of the first boost converter a battery or ultracapacitor energy storage is connected to take care of the fuel cell slow transient response (200 watts/min). The robust features of the proposed control system ensure a constant output DC voltage for a variety of load fluctuations, thus limiting the power being delivered by the fuel cell during a load transient. Moreover, the proposed configuration simplifies the power control management and can interact with the fuel cell controller. The simulation results and the experimental results confirm the feasibility of the proposed system.
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Energy management systems on board of electric vehicles, based on power electronicsGuidi, Giuseppe January 2009 (has links)
The core of any electric vehicle (EV) is the electric drive train, intended as the energy conversion chain from the energy tank (typically some kind of rechargeable battery) to the electric motor that converts the electrical energy into the mechanical energy needed for the vehicle motion. The need for on-board electrical energy storage is the factor that has so far prevented pure electric vehicles from conquering significant market share. In fact electrochemical batteries, which are currently the most suitable device for electrical energy storage, have serious limitations in terms of energy and/or power density, cost and safety. All those characteristics reflect in pure electric vehicles being outperformed by standard internal combustion engine (ICE) based vehicles in terms of driving range, time needed to refuel and purchase cost. Electric vehicles do have their distinctive advantages, being intrinsically much more efficient, operating at zero emissions at the pipe, and offering a higher degree of controllability that can potentially enhance driving safety. No wonder then, that electric energy storage technology has attracted considerable R&D investments, resulting in new traction battery packs that are getting closer and closer to the industrial targets. In this scenario of EV technology gaining momentum, power electronics engineers have to come up with newer solutions allowing for more efficient and more reliable utilization of the precious on-board energy that comes in a form that cannot be directly utilized by the motor. At present, most of the research in the area of power electronics for automotive is focused in volume and cost reduction techniques. The increase in power density is pursued by developing components that can be operated at higher temperature, thus relieving the requirements on cooling. In this thesis, the focus is on the development of alternative topologies for the power electronics converters that make use of some peculiarities of the energy storage components and of the electrical drive train in general, rather than being a mere component-level optimization of well established topologies. A novel converter topology is proposed for hybridization of the energy source with a supercapacitor-based power buffer being used to assist the main traction battery. From the functional point of view, the topology implements a bidirectional DC/DC converter. Making use of the fact that the battery terminal voltage is close to constant, an arrangement for the supercapacitors is devised allowing for bidirectional power flow by using power electronics devices of lower ratings than the ones needed in conventional DC/DC converters. At the same time, much smaller magnetic components are needed. Theoretical analysis of the operation of the proposed converter is given, allowing for optimized design. A full-scale experimental prototype rated at 30 kW, intended for use in a pure EV, has been built and tested. Results validate the theory and show that no particular impediment exist to the deployment of the concept in practical applications. Another concept introduced in the thesis is an architecture where the traction inverter is embedded in the energy storage device. The latter is constituted by several modules, as in the case of modern Li-ion battery systems, and each module is equipped with a local power electronics interface, making it functionally equivalent to a controllable voltage source. The result is a modular, distributed system that can be engineered to have very high reliability and also to exhibit self-healing properties. A prototype with a minimum number of modules has been built and tested. Results confirm the effectiveness of the system, and make it a good candidate for deployment in applications where reliability is the most important requirement.
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DC-DC Converter with Improved Dynamic Response and Efficiency Using a Calibrated Auxiliary PhaseWen, Yue 04 January 2012 (has links)
A digital adaptive slope control (DASC) technique is presented to improve the dynamic
response and efficiency of a current programmed mode (CPM) buck converter employing
a low-cost auxiliary phase. Compared to the existing nonlinear control techniques, the
advantages of the proposed control scheme include superior voltage droop and settling
time, and on-line calibration to compensate for tolerance in the inductance. The proposed
technique is experimentally verified on a 500 kHz, 10 V to 2.5 V CPM buck converter
prototype. Charge balancing and optimal transient response are achieved for a range of
positive and negative load steps. In addition, compared to a representative single phase
converter, the proposed system not only has better dynamic response but also achieves
2 % heavy-load and 10 % light-load steady-state efficiency improvement. The impact of
the auxiliary phase operation on the converter’s dynamic efficiency is also evaluated at
different load step amplitudes and frequencies.
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DC-DC Converter with Improved Dynamic Response and Efficiency Using a Calibrated Auxiliary PhaseWen, Yue 04 January 2012 (has links)
A digital adaptive slope control (DASC) technique is presented to improve the dynamic
response and efficiency of a current programmed mode (CPM) buck converter employing
a low-cost auxiliary phase. Compared to the existing nonlinear control techniques, the
advantages of the proposed control scheme include superior voltage droop and settling
time, and on-line calibration to compensate for tolerance in the inductance. The proposed
technique is experimentally verified on a 500 kHz, 10 V to 2.5 V CPM buck converter
prototype. Charge balancing and optimal transient response are achieved for a range of
positive and negative load steps. In addition, compared to a representative single phase
converter, the proposed system not only has better dynamic response but also achieves
2 % heavy-load and 10 % light-load steady-state efficiency improvement. The impact of
the auxiliary phase operation on the converter’s dynamic efficiency is also evaluated at
different load step amplitudes and frequencies.
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Pem fuel cell modeling and converters design for a 48 v dc power busRestrepo Patiño, Carlos Alberto 22 June 2012 (has links)
Fuel cells (FC) are electrochemical devices that directly convert the chemical energy of a fuel into electricity. Power systems based on proton exchange membrane fuel cell (PEMFC) technology have been the object of increasing attention in recent years as they appear very promising in both stationary and mobile applications due to their high efficiency, low operating temperature allowing fast startup, high power density, solid electrolyte, long cell and stack life, low corrosion, excellent dynamic response with respect to the other FCs, and nonpolluting emissions to the environment if the hydrogen is obtained from renewable sources. The output-voltage characteristic in a PEMFC is limited by the mechanical devices which are used for regulating the air flow in its cathode, the hydrogen flow in its anode, its inner temperature, and the humidity of the air supplied to it. Usually, the FC time constants are dominated by the fuel delivery system, in particular by the slow dynamics of the compressor responsible for supplying the oxygen. As a consequence, a fast load transient demand could cause a high voltage drop in a short time known as oxygen starvation
phenomenon that is harmful for the FC. Thus, FCs are considered as a slow dynamic response equipment with respect to the load transient requirements. Therefore, batteries, ultracapacitors or other auxiliary power sources are needed to support the operation of the FC in order to ensure a fast response to any load power transient. The resulting systems, known as FC hybrid systems, can limit the slope of the current or the power generated by the FC with the use of current-controlled dc-dc converters. In this way, the reactant gas starvation phenomena can be avoided and the system
can operate with higher efficiency. The purpose of this thesis is the design of a DC-DC converter suitable to interconnect all the different elements in a PEMFC-hybrid 48-V DC bus. Since the converter could be placed between elements with very different voltage levels, a buck-boost structure has been selected. Especially to fulfill the low ripple requirements of the PEMFCs, but also those of the auxiliary storage elements and loads, our structure has inductors in series at both its input and its output. Magnetically coupling these inductors and adding a damping
network to its intermediate capacitor we have designed an easily controllable converter with second-order-buck-like dominant dynamics. This new proposed topology has high efficiency and wide bandwidth acting either as a voltage or as a current regulator. The magnetic coupling allows to control with similar performances the input or the output inductor currents. This characteristic is very useful because the designed current-controlled converter is able to withstand
shortcircuits at its output and, when connected to the FC, it facilitates to regulate the current extracted from the FC to avoid the oxygen starvation phenomenon. Testing in a safe way the converter connected to the FC required to build an FC simulator that was subsequently improved by developing an emulator that offered real-time processing and oxygen-starvation indication. To study the developed converters and emulators with different brands of PEMFCs it was necessary to reactivate long-time inactive Palcan FCs. Since the results provided by the manual reactivation procedure were unsatisfactory, an automatic reactivation system has been developed as a complementary study of the thesis. / En esta tesis se avanzo en el diseño de un bus DC de 48 V que utiliza como elemento principal de generación de energía eléctrica una pila de combustible. Debido a que la dinámica de las pilas de combustible están limitadas por sus elementos mecánicos auxiliares de control una variación rápida de una carga conectada a ella puede ocasionar daños. Es por esto que es necesario utilizar elementos almacenadores de energía que puedan suministrar estas rápidas variaciones de carga y convertidores para que gestionen de una forma controlada la potencia del bus DC. Durante la realización de pruebas de los convertidores es de gran importancia utilizar emuladores o simuladores de pilas de combustibles, esto nos permite de una forma económica y segura realizar pruebas criticas antes de conectar los convertidores a la pila. Adicionalmente una nueva topologia de convertidor fue presentada y ésta gestionará la potencia en el bus
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Advances in Fuel Cell Vehicle DesignBauman, Jennifer January 2008 (has links)
Factors such as global warming, dwindling fossil fuel reserves, and energy security concerns combine to indicate that a replacement for the internal combustion engine (ICE) vehicle is needed. Fuel cell vehicles have the potential to address the problems surrounding the ICE vehicle without imposing any significant restrictions on vehicle performance, driving range, or refuelling time. Though there are currently some obstacles to overcome before attaining the widespread commercialization of fuel cell vehicles, such as improvements in fuel cell and battery durability, development of a hydrogen infrastructure, and reduction of high costs, the fundamental concept of the fuel cell vehicle is strong: it is efficient, emits zero harmful emissions, and the hydrogen fuel can be produced from various renewable sources. Therefore, research on fuel cell vehicle design is imperative in order to improve vehicle performance and durability, increase efficiency, and reduce costs. This thesis makes a number of key contributions to the advancement of fuel cell vehicle design within two main research areas: powertrain design and DC/DC converters.
With regards to powertrain design, this research presents a novel fuel cell-battery-ultracapacitor topology which shows reduced mass and cost, and increased efficiency, over other promising topologies found in the literature. A detailed vehicle simulator created in MATLAB/Simulink is used to perform a comprehensive parametric study on different fuel cell vehicle types, resulting in general conclusions for optimal topologies, as well as component types and sizes, for fuel cell vehicles. Next, a general analytical method to optimize the novel battery-ultracapacitor energy storage system based on maximizing efficiency, and minimizing cost and mass, is developed.
With regards to DC/DC converters, it is important to design efficient and light-weight converters for use in fuel cell and other electric vehicles to improve overall vehicle fuel economy. Thus, this research presents a novel soft-switching method, the capacitor-switched regenerative snubber, for the high-power DC/DC boost converters commonly used in fuel cell vehicles. This circuit is shown to increase the efficiency and reduce the overall mass of the DC/DC boost converter.
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DC to DC converter for smart dustNisar, Kashif January 2012 (has links)
This work describes the implementation of DC to DC converter for Smart Dust in 65 nm CMOS technology. The purpose of a DC to DC converter is to convert a battery voltage of 1 Vto a lower voltage of 0.5 V used by the processor. The topology used in this DC to DC converteris of Buck type which converts a higher voltage to lower voltage with the advantage of givinghigh efficiency about 75%. The system uses PWM (Pulse width modulation) technique. It usesnon-overlapping clock generation technique for reducing the power consumption. The systemprovides up to 5 mA load current and has power consumption of 2.5 mW.
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Advances in Fuel Cell Vehicle DesignBauman, Jennifer January 2008 (has links)
Factors such as global warming, dwindling fossil fuel reserves, and energy security concerns combine to indicate that a replacement for the internal combustion engine (ICE) vehicle is needed. Fuel cell vehicles have the potential to address the problems surrounding the ICE vehicle without imposing any significant restrictions on vehicle performance, driving range, or refuelling time. Though there are currently some obstacles to overcome before attaining the widespread commercialization of fuel cell vehicles, such as improvements in fuel cell and battery durability, development of a hydrogen infrastructure, and reduction of high costs, the fundamental concept of the fuel cell vehicle is strong: it is efficient, emits zero harmful emissions, and the hydrogen fuel can be produced from various renewable sources. Therefore, research on fuel cell vehicle design is imperative in order to improve vehicle performance and durability, increase efficiency, and reduce costs. This thesis makes a number of key contributions to the advancement of fuel cell vehicle design within two main research areas: powertrain design and DC/DC converters.
With regards to powertrain design, this research presents a novel fuel cell-battery-ultracapacitor topology which shows reduced mass and cost, and increased efficiency, over other promising topologies found in the literature. A detailed vehicle simulator created in MATLAB/Simulink is used to perform a comprehensive parametric study on different fuel cell vehicle types, resulting in general conclusions for optimal topologies, as well as component types and sizes, for fuel cell vehicles. Next, a general analytical method to optimize the novel battery-ultracapacitor energy storage system based on maximizing efficiency, and minimizing cost and mass, is developed.
With regards to DC/DC converters, it is important to design efficient and light-weight converters for use in fuel cell and other electric vehicles to improve overall vehicle fuel economy. Thus, this research presents a novel soft-switching method, the capacitor-switched regenerative snubber, for the high-power DC/DC boost converters commonly used in fuel cell vehicles. This circuit is shown to increase the efficiency and reduce the overall mass of the DC/DC boost converter.
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Organically Grown Microgrids: the Development and Simulation of a Solar Home System-based MicrogridUnger, Kurtis January 2012 (has links)
The United Nations has declared 2012 the ``International Year of Sustainable Energy for All''. A substantial portion of the world's population (some 1.3 billion people) currently live without electricity and development efforts to reach them are progressing relatively slowly. This thesis follows the development of a technology which can enable community owned and operated microgrids to emerge based solely on the local supply and demand of that community.
Although this thesis ends with the technical analysis of a DC/DC converter, there is a significant amount of background to cover in order to properly understand the context in which it will be used.
After providing an introduction into typical rural electrification efforts and pointing out some of the shortcomings of these projects, this thesis introduces some cutting edge efforts which combine solar home system technology with cellular technology and discusses the benefits of such a marriage of technology.
Next, the research proposes some tweaks to this novel technology and provides a high-level economic demonstration of the spread of solar home systems in a community based on these modifications. It then takes this concept even further and proposes the addition of a DC/DC converter which could turn these individual solar home systems into a proper microgrid.
This thesis elaborates on the development process of simulating such a microgrid in PSCAD, including the individual components of a solar home system and the specific task of designing the converter which would form the backbone of the proposed microgrid. The final simulations and analyses demonstrate a microgrid that is both technically and economically feasible for developing world applications.
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