2,334 research outputs found

    Modeling of power electronic systems with EMTP

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    In view of the potential impact of power electronics on power systems, there is need for a computer modeling/analysis tool to perform simulation studies on power systems with power electronic components as well as to educate engineering students about such systems. The modeling of the major power electronic components of the NASA Space Station Freedom Electric Power System is described along with ElectroMagnetic Transients Program (EMTP) and it is demonstrated that EMTP can serve as a very useful tool for teaching, design, analysis, and research in the area of power systems with power electronic components. EMTP modeling of power electronic circuits is described and simulation results are presented

    Linearized large signal modeling, analysis, and control design of phase-controlled series-parallel resonant converters using state feedback

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    This paper proposes a linearized large signal state-space model for the fixed-frequency phase-controlled series-parallel resonant converter. The proposed model utilizes state feedback of the output filter inductor current to perform linearization. The model combines multiple-frequency and average state-space modeling techniques to generate an aggregate model with dc state variables that are relatively easier to control and slower than the fast resonant tank dynamics. The main objective of the linearized model is to provide a linear representation of the converter behavior under large signal variation which is suitable for faster simulation and large signal estimation/calculation of the converter state variables. The model also provides insight into converter dynamics as well as a simplified reduced order transfer function for PI closed-loop design. Experimental and simulation results from a detailed switched converter model are compared with the proposed state-space model output to verify its accuracy and robustness

    Conversor de alta tensão e alta frequência para carga resistiva com variação imprevisível

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    Orientador: José Antenor PomilioDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Transformadores de alta tensão possuem algumas características específicas, uma vez que o efeito de elementos parasitas é amplificado, devido ao elevado número espiras, necessário para se atingir os níveis de tensão desejados. A operação em alta frequência reduz o volume de dispositivos magnéticos, tornando os sistemas mais compactos, o que pode, no entanto, dar margem a outros problemas, como ruídos de alta frequência, interferência eletromagnética e manifestação de ressonâncias. Nesta dissertação foi desenvolvido um conversor de alta tensão, com operação em alta frequência para transferência de potência para uma carga resistiva com variação imprevisível, desde uma situação de curto-circuito até a de circuito aberto, levando em consideração as particularidades do transformador de alta tensão operando em alta frequência. Simulações e cálculos teóricos foram realizados para caracterização do comportamento do sistema. Sistemas de proteção, controle e supervisão foram desenvolvidos para minimizar os efeitos de elementos parasitas e ressonâncias, bem como para garantir a operação segura do conversor. Um protótipo conceitual foi construído para validação das simulações e cálculos realizadosAbstract: High voltage transformers have specific characteristics, since the effect of some parasitic elements is highlighted, due to its high number of turns, in order to reach the desired voltage levels. High frequency operation reduces the volume of magnetic devices, making the systems more versatile, however it can give rise to other problems such as switching noise, electromagnetic interference and resonances. In this dissertation a high voltage converter, with high frequency operation was developed for power transferring to resistive loads with unpredictable variation, from the short circuit to the open circuit condition, taking in account the High Voltage High Frequency Transformer¿s particularities. Simulations and theoretical calculations were made to characterize the system¿s behavior. Protection, control and supervision systems were developed to minimize the effects of parasitic elements and resonances, as well as to ensure the safe and correct converter¿s operation. A conceptual prototype was built to validate the simulations and calculations performedMestradoEnergia EletricaMestre em Engenharia Elétric

    Induction heating converter's design, control and modeling applied to continuous wire heating

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    Induction heating is a heating method for electrically conductive materials that takes advantage of the heat generated by the Eddy currents originated by means of a varying magnetic field. Since Michael Faraday discovered electromagnetic induction in 1831, this phenomena has been widely studied in many applications like transformers, motors or generators' design. At the turn of the 20th century, induction started to be studied as a heating method, leading to the construction of the first industrial induction melting equipment by the Electric Furnace Company in 1927. At first, the varying magnetic fields were obtained with spark-gap generators, vacuum-tube generators and low frequency motor-generator sets. With the emergence of reliable semiconductors in the late 1960's, motor-generators were replaced by solid-state converters for low frequency applications. With regard to the characterization of the inductor-workpiece system, the first models used to understand the load's behavior were based on analytical methods. These methods were useful to analyze the overall behavior of the load, but they were not accurate enough for a precise analysis and were limited to simple geometries. With the emergence of computers, numerical methods experienced a tremendous growth in the 1990's and started to be applied in the induction heating field. Nowadays, the development of commercial softwares that allow this type of analysis have started to make the use of numerical methods popular among research centers and enterprises. This type of softwares allow a great variety of complex analysis with high precision, consequently diminishing the trial and error process. The research realized in last decades, the increase in the utilization of numerical modeling and the appearance and improvement of semiconductor devices, with their corresponding cost reduction, have caused the spread of induction heating in many fields. Induction heating equipments can be found in many applications, since domestic cookers to high-power aluminum melting furnaces or automotive sealing equipments, and are becoming more and more popular thanks to their easy control, quick heating and the energy savings obtained. The present thesis focuses on the application of induction heating to wire heating. The wire heating is a continuous heating method in which the wire is continuously feeding the heating inductor. This heating method allows high production rates with reduced space requirements and is usually found in medium to high power industrial processes working 24 hours per day. The first chapters of this study introduce the induction heating phenomena, its modeling and the converters and tanks used. Afterwards, a multichannel converter for high-power and high-frequency applications is designed and implemented with the aim of providing modularity to the converter and reduce the designing time, the production cost and its maintenance. Moreover, this type of structure provides reliability to the system and enables low repairing times, which is an extremely interesting feature for 24 hours processes. Additionally, a software phase-locked loop for induction heating applications is designed and implemented to prove its flexibility and reliability. This type of control allows the use of the same hardware for different applications, which is attractive for the case of industrial applications. This phase-locked loop is afterwards used to design and implement a load-adaptative control that varies the references to have soft-switching according to load's variation, improving converter's performance. Finally, the modeling of a continuous induction wire hardening system is realized, solving the difficulty of considering the mutual influence between the thermal, electromagnetic and electric parameters. In this thesis, a continuous process is modeled and tested using numerical methods and considering converter's operation and influence in the process.Postprint (published version

    Exploitation of Digital Filters to Advance the Single-Phase T/4 Delay PLL System

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    With the development of digital signal processing technologies, control and monitoring of power electronics conversion systems have been evolving to become fully digital. As the basic element in the design and analysis phases of digital controllers or filters, a number of unit delays (z-1) have been employed, e.g., in a cascaded structure. Practically, the number of unit delays is designed as an integer, which is related to the sampling frequency as well as the ac signal fundamental frequency (e.g., 50 Hz). More common, the sampling frequency is fixed during operation for simplicity and design. Hence, any disturbance in the ac signal will violate this design rule and it can become a major challenge for digital controllers. To deal with the above issue, this paper first exploits a virtual unit delay (zv-1) to emulate the variable sampling behavior in practical digital signal processors with a fixed sampling rate. This exploitation is demonstrated on a T/4 Delay Phase Locked Loop (PLL) system for a single-phase grid-connected inverter. The T/4 Delay PLL requires to cascade 50 unit delays when implemented (for a 50-Hz system with 10 kHz sampling frequency). Furthermore, digital frequency adaptive comb filters are adopted to enhance the performance of the T/4 Delay PLL when the grid suffers from harmonics. Experimental results have confirmed the effectiveness of the digital filters for advanced control systems

    Dual active bridge converters in solid state transformers

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    This dissertation presents a comprehensive study of Dual Active Bridge (DAB) converters for Solid State Transformers (SSTs). The first contribution is to propose an ac-ac DAB converter as a single stage SST. The proposed converter topology consists of two active H-bridges and one high-frequency transformer. Output voltage can be regulated when input voltage changes by phase shift modulation. Power is transferred from the leading bridge to the lagging bridge. It analyzes the steady-state operation and the range of zero-voltage switching. It develops a switch commutation scheme for the ac-ac DAB converters. Simulation and experiment results of a scaled down prototype are provided to verify the theoretical analysis. The second contribution is to develop a full-order continuous-time average model for dc-dc DAB converters. The transformer current in DAB converter is purely ac, making continuous-time modeling difficult. Instead, the proposed approach uses the dc terms and 1st order terms of transformer current and capacitor voltage as state variables. Singular perturbation analysis is performed to find the sufficient conditions to separate the dynamics of transformer current and capacitor voltage. Experimental results confirm that the proposed model predicts the small-signal frequency response more accurately. The third contribution addresses the controller design of a dc-dc DAB converter when driving a single-phase dc-ac inverter. It studies the effect of 120 Hz current generated by the single-phase inverter. The limitation of PI-controller is investigated. Two methods are proposed to reduce the voltage ripple at the output voltage of DAB converter. The first method helps the feedback loop with feedforward from inverter, while the second one adds an additional resonance controller to the feedback loop. Theoretical analysis, simulation and experiment results are provided to verify the effectiveness of the proposed methods --Abstract, page iii

    A survey on modeling of microgrids - from fundamental physics to phasors and voltage sources

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    Microgrids have been identified as key components of modern electrical systems to facilitate the integration of renewable distributed generation units. Their analysis and controller design requires the development of advanced (typically model-based) techniques naturally posing an interesting challenge to the control community. Although there are widely accepted reduced order models to describe the dynamic behavior of microgrids, they are typically presented without details about the reduction procedure---hampering the understanding of the physical phenomena behind them. Preceded by an introduction to basic notions and definitions in power systems, the present survey reviews key characteristics and main components of a microgrid. We introduce the reader to the basic functionality of DC/AC inverters, as well as to standard operating modes and control schemes of inverter-interfaced power sources in microgrid applications. Based on this exposition and starting from fundamental physics, we present detailed dynamical models of the main microgrid components. Furthermore, we clearly state the underlying assumptions which lead to the standard reduced model with inverters represented by controllable voltage sources, as well as static network and load representations, hence, providing a complete modular model derivation of a three-phase inverter-based microgrid

    Analysis, Design and Control of a Modular Full-Si Converter Concept for Electric Vehicle Ultra-Fast Charging

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    L'abstract è presente nell'allegato / the abstract is in the attachmen

    Emerging Works on Wireless Inductive Power Transfer: AUV Charging from Constant Current Distribution and Analysis of Controls in EV Dynamic Charging

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    Wireless power transfer through inductive coupling, termed as inductive power transfer (IPT), is one of the important technologies in power electronics that enable transfer of power between entities without physical connections. While it has seen significant growth in the areas such as electric vehicle charging, phone charging and biomedical implants, its emerging applications include charging of autonomous underwater vehicles (AUVs) and dynamic charging of electric vehicles from the roadway. This dissertation addresses a few key challenges in these areas of IPT applications, paving the way for future developments. For the WPT for AUV, the recently developing sea-bed installed marine systems are targeted, which typically gets power from on-shore sources through constant dc low-current distribution. As the present underwater IPT topologies are not suitable for such applications, this dissertation proposes underwater IPT topologies to interface directly with such constant current distribution and provide a constant voltage output supply to the on-board systems inside the AUVs. The considerations for seawater losses and the small-signal models for control purposes are also addressed. Analysis and experimental results are provided for validations of the analytical designs and models. In the area of electric vehicle dynamic wireless power transfer (EV DWPT), the comparison of control performances of different coupler, compensation topologies and control implementations are addressed. The effect of communication latency on control bandwidth are also addressed. The outcomes are presented through analysis and simulations, and based on that future research recommendations are made to pave way for future commercial developments of well regulated and interoperable EV DWPT systems

    Modeling and control of a high power soft-switched bi-directional DC/DC converter for fuel cell applications

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    This work presents a new high power, bi-directional, isolated dc-dc converter for a fuel cell energy management system that will be fitted into a test vehicle being built by Ford Motor Company. The work includes two parts. The first part is to propose a new topology and analyze the principles of the circuits operation. Design guidelines with detailed circuit simulations are presented to verify the feasibility of the new circuit topology. Based on the conceptual understanding of the converter, the mathematical model is also derived to design a control system that achieves soft start up and meets the performance requirements. The second part is to fabricate a 1.6 kW prototype converter in the laboratory. Using the prototype, the steady state performance of the open loop system was tested to verify the analysis and simulation results. A dual half-bridge topology is presented to implement the required power rating using the minimum number of devices. Unified zero-voltage-switching (ZVS) is achieved in either direction of power flow to eliminate switching losses for all devices, increase the efficiency of the system and reduce the electromagnetic interference (EMI). Compared to the other soft-switched dc-dc converters, neither a voltage-clamping circuit nor extra switching devices and resonant components are required in the proposed circuit for soft-switching implementation. All these new features allow efficient power conversion and compact packaging. Different start-up schemes are proposed to successfully limit the in-rush current when the converter is started in the boost mode of operation. The full control system including the start-up scheme is developed and verified using simulation results based upon the average model. A 1.6 kW prototype of the converter has been built and successfully tested under full power. The experimental results of the converter\u27s steady-state operation confirm the simulation analysis
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