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51 
A threephase hybrid dcac inverter system utilizing hysteresis control /White, Terence H. January 2004 (has links) (PDF)
Thesis (M.S. in Electrical Engineering)Naval Postgraduate School, June 2004. / Thesis advisor(s): Robert Ashton. Includes bibliographical references (p. 7374). Also available online.

52 
Modelling and control of a novel hybrid multilevel inverter for photovoltaic integration.Wanjekeche, Tom. January 2013 (has links)
D. Tech. Electrical Engineering. / Aims to : 1. Derive the analytical solutions for describing the spectral characteristics of multicarrier based multilevel PWM inverter using double Fourier transform. 2. To carry out a comprehensive modelling of a cascaded NPC/Hbridge for PVGrid application. 3. To integrate the Cascaded NPC/Hbridge inverter, grid and PV model and analyze the power flow characteristics for varying PV source current and voltage. Detailed analysis of PV and development of MPPT algorithm are not part of this thesis. 4. To develop a novel hybrid phase shifted PWM control algorithm and test its superior harmonic suppression in MATLAB simulation. 5. To compare the developed control algorithm with conventional multicarrier approach in terms of harmonic suppression and component count 6. To develop a control scheme that is capable of injecting maximum power into the grid from the model at different environmental conditions. 7. To explore and develop analytical tools for DC link voltage control of the model. 8. To design and built a scaled down. 9 Level cascaded NPC/Hbridge inverter for grid connected application.

53 
Design synthesis of LCC HVDC control systems.Chetty, Leon. January 2011 (has links)
From the early days of HVDC system applications, the importance of mathematical
modelling of the dynamics of Line Commutated Converter (LCC) HVDC systems
has been appreciated. There are essentially two methodologies used to develop
mathematical models of dynamic systems. One methodology is to define the
properties of the system by the “laws of nature” and other wellestablished
relationships. Basic techniques of this methodology involve describing the system’s
processes using differential equations. This methodology is called “Deductive
Modelling”.
The other methodology used to derive mathematical models of a dynamic system is
based on experimentation. Input and output signals from the original system are
recorded to infer a mathematical model of the system. This methodology is known as
“Inductive Modelling”.
A review of the current state of the art of modelling LCC HVDC systems indicates
that majority of the techniques utilized to develop mathematical models of LCC
HVDC systems have used the “Deductive Modelling” approach. This methodology
requires accurate knowledge of the ac systems and the dc system and involves
complicated mathematics. In practice, it is nearly impossible to obtain accurate
knowledge of the ac systems connected to LCC HVDC systems.
The main aim of this thesis is to present an “Inductive Modelling” methodology to
calculate the plant transfer functions of LCC HVDC systems. Due to the uncertain
nature of the effective short circuit ratio of rectifier and inverter converter stations,
generic ranges of parametric uncertainties of the developed plant transfer functions
were determined. Based on the determined range of HVDC plant parametric
uncertainty, Quantitative Feedback Theory (QFT) methodology was used to design
the parameters of the LCC HVDC control system. The stability of the startup and
step responses for varying ac system conditions validated the “Inductive Modelling”
technique and the QFT design methodology.
The thesis presents the following, which are considered to be scientific advancements and
contributions to the body of knowledge:
· Novel LCC HVDC Step Response (HSR) equations were developed using an
“Inductive Modeling” technique.
· The range of parametric variations of the LCC HSR equations were determined for
various rectifier and inverter ac system effective short circuit ratios.
· The LCC HSR equations were used to develop the LCC HVDC plant transfer
functions for various rectifier and inverter effective short circuit ratios.
· The LCC HVDC plant transfer functions were utilized to design an LCC HVDC
control system for varying ac system conditions using Quantitative Feedback Theory
(QFT) methodology.
The main contributions of this thesis relate to LCC HVDC systems. This thesis does
not attempt to advance control theory however this thesis does apply existing
classical control theory to LCC HVDC control systems.
Index Terms: Line Commutated Converter, HVDC, inductive modelling, power
system, transient analysis. / Thesis (Ph.D.)University of KwaZluNatal, Durban, 2011.

54 
The application of controllable inverterbased series compensation to power oscillation damping.Chonco, Nkosinathi Stanford. January 2000 (has links)
Poorly damped oscillations that occur between the generators in large interconnected
power systems often limit the amount of power that can be transmitted through a
transmission corridor and are a threat to secure system operation. Coordinated
insertion and removal of capacitors in series with a transmission line is one of the
approaches that has been known for many years to be capable of enhancing the
damping of power system oscillations. Unfortunately however, this approach
historically relied on the operation of mechanical circuit breakers which were too
slow and unreliable for the highspeed and repetitive operation that such an
application demands. Recentlyemerged, highspeed powerelectronicbased
switching devices are finding increasing use in modem power systems in the socalled
Flexible AC Transmission Systems (F ACTS) concept. One particular FACTS
impedance controller, namely the inverterbased series compensator, can rapidly alter
the magnitude of capacitive compensating reactance in series with the line to make it
practically feasible to enhance the damping of power system oscillations via
dynamicallycontrolled series compensation.
This thesis identifies, in the literature, an insightful approach to the design of an
idealised controllable series compensator (CSC) damping scheme; such an approach
has been considered in the analyses of the thesis. Three mathematical models of a
singlemachine infinite bus (SMIB) system are developed and are subsequently used
in the initial design and analysis of a CSC damping controller carried out in the thesis.
The simple SMIB system case study is used to identify and investigate the factors that
have a significant impact on the performance of a CSC damping controller before
studying the more complex issue of interarea mode damping using a CSC.
This thesis successfully confirms the results of a previous analytical study in which an
idealised representation of the CSC was used, and extends the scope of that previous
study by also considering a detailed representation of one particular type of CSC: the
inverterbased series compensator. The two key findings of this extended
investigation are that the inverterbased form of controllable series compensator can
successfully be used to damp power oscillations and that, where the damping of oscillations is the particular focus of study, an idealised representation of the inverterbased
CSC is suitable for the analyses.
In the case of the interarea mode damping problem, the selection of an appropriate
input signal to the CSC damping controller is a key issue, since the oscillations that
are to be damped involve a number of participating generators. This thesis examines
the suitability of a few candidate input signals that have been proposed in the
literature using the conceptually simpler SMIB system analytical models that have
been developed. Finally, the thesis applies the understanding of CSC damping
controller design gained from the SMIB study to the problem of interarea mode
damping on a fourgenerator study system. Timedomain simulation results are
presented to demonstrate the impact of the controlled inverterbased series
compensator on the damping of the interarea mode of this system. / Thesis (M.Sc.Eng.)University of Natal, Durban, 2000.

55 
Programmed harmonic reduction in inverters and controlled rectifiersDeib, Deib Ali. January 1993 (has links)
Thesis (Ph. D.)Ohio University, August, 1993. / Title from PDF t.p.

56 
A comparative study of capacitor voltage balancing techniques for flying capacitor multilevel power electronic convertersYadhati, Vennela, January 2010 (has links) (PDF)
Thesis (M.S.)Missouri University of Science and Technology, 2010. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed July 26, 2010) Includes bibliographical references (p. 96102).

57 
A multilevel inverter for DC reticulationMolepo, Seaga Abram 03 1900 (has links)
Thesis (MScEng)Stellenbosch University, 2003. / ENGLISH ABSTRACT: This report presents the design and development of a multilevel inverter for DC reticulation.
Two main multilevel inverter topologies are introduced and discussed. The research
focusses on the flying capacitor multilevel topology, since it became evident that it is
more suitable for DC reticulation than the diode clamped multilevel topology.
A bootstrap power supply for the gate drive circuits of a multilevel inverter is developed
and its feasibility verified experimentally. A selfstarting auxiliary power supply, that
aims at addressing the power supply problem of DC to AC and DC to DC converters, is
designed and its functionality demonstrated on a flying capacitor multilevel inverter. An
FPGA based digital controller for implementing the inverter's control algorithms is also
discussed. This controller incorporates a feedforward output voltage regulation technique.
Experimental results obtained with the fourlevel flying capacitor multilevel inverter, using
the FPGA based digital controller and the selfstarting auxiliary power supply, are
presented in this report. / AFRIKAANSE OPSOMMING: In hierdie verslag word die ontwerp en ontwikkelling van 'n multivlak omsetter vir GS
retikulasie bespreek. Twee hoof multivlak omsetter topologië word voorgestel en bespreek.
Die navorsing fokus op die "vlieëndekapasitor" multivlak topologië omdat dit
duidelik geword het dat dit 'n beter opsie is vir die GS retikulasie as die diodeklamp
multivlak topologië.
'n Kragbron vir die hekaandryfbane van die multivlak omsetter is ontwikkel en die werking
daarvan is met experimentele toetse bevestig. 'n Selfbegin kragbron, wat die probleem
van die kragtoevoer aan die GS na WS en die GS na GS omsetters aanspreek, is
ontwerp en die funksionaliteit is gedemonstreer met die "vlieëndekapasitor" multivlak
. omsetter. 'n Digitale beheerder, gebaseer op 'n FPGA, wat gebruik word om die omsetter
se beheer algoritmes te implementeer, word ook bespreek. Hierdie beheerder inkorporeer
'n vorentoevoer uittree spannings regulasie tegniek.
Eksperimentele resultate wat gekry is met 'n viervlak "vlieëndekapasitor" multivlak
omsetter, wat van die FPGA gebaseerde digitale beheerder en die selfbegin kragbron
gebruik maak, word ook in die verslag bespreek.

58 
Desenvolvimento da modulação Space Vector para um inversor trifásico multinível híbrido assimétrico de nove níveis por fase com PonteH em cascataRosito, Fernando Covolan 13 September 2017 (has links)
Esta dissertação de mestrado propõe desenvolver a modulação vetorial (space vector – SV) para um inversor trifásico multinível híbrido assimétrico de nove níveis por fase com ponteH em cascata (cascaded Hbridge – CHB). A verificação do desempenho ocorre através de simulações em software de simulação matemática, e posterior comparações entre duas simulações realizadas, como também a comparação da simulação de melhor desempenho com simulações obtidas com a modulação por síntese de formas de onda quasequadradas e a modulação híbrida. Para tanto, inicialmente são revisadas as topologias de inversores de frequência mais tradicionais na literatura, identificando as suas características para justificar a escolha da topologia híbrida assimétrica. Posteriomente são revisados os métodos de modulação para inversores de frequência, identificando na modulação vetorial vantagens para sintetização das tensões de linha. Após, são relacioanados trabalhos envolvendo a modulação space vector aplicada em inversores multiníveis. Em seguida, a modulação SV é desenvolvida para o inversor trifásico multinível híbrido assimétrico de nove níveis por fase com ponteH em cascata, sendo realizadas as seguintes etapas: definição dos possíveis vetores de comutação (estados de chaveamento) do inversor proposto no espaço tridimensional e no plano αβ; identificação dos planos limites e dos planos de separação dos setores no plano αβ; obtenção das matrizes de decomposição e; definição da sequência de comutação. Os resultados, obtidos por meio de software de simulação matemática, dos gráficos das tensões de fase e tensões de linha, assim como os valores de distorção harmônica total (total harmonic distortion – THD), fator de distorção de primeira ordem (first order distortion factor – DF1), tensão de modo comum, espectro harmônico dos sinais das tensões (de fase e de linha) são analisados, sendo os índices de THD, DF1 e tensão de modo comum comparados entre duas sequências de comutação diferentes para o inversor proposto. Também, os valores desses índices são comparados com outras técnicas de modulação (modulação por síntese de formas de onda quasequadradas (QQ) e a modulação híbrida). O desenvolvimento e os resultados das simulações da modulação SV na topologia híbrida assimétrica de nove níveis proposta, assim como as análises das comparações, apontam resultados satisfatórios, identificando um potencial grandioso da modulação SV desenvolvida. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 20170929T13:33:41Z
No. of bitstreams: 1
Dissertacao Fernando Covolan Rosito.pdf: 6134096 bytes, checksum: e34621dae75a6139302a387eb73107b7 (MD5) / Made available in DSpace on 20170929T13:33:41Z (GMT). No. of bitstreams: 1
Dissertacao Fernando Covolan Rosito.pdf: 6134096 bytes, checksum: e34621dae75a6139302a387eb73107b7 (MD5)
Previous issue date: 20170929 / This dissertation proposes to develop the space vector (SV) modulation for a three phase hybrid asymmetric multilevel inverter of nine levels per phase with cascaded Hbridge (CHB). Performance verification occurs through software simulations, and subsequent comparisons between two simulations performed, as well as the comparison of the best performance simulation with simulations obtained with the step wave modulation and hybrid modulation. To do this, the topologies of more traditional frequency inverters are reviewed in the literature, identifying their characteristics to justify the choice of hybrid asymmetric topology. Subsequently, the modulation methods for frequency inverters are reviewed, identifying the advantages of vector modulation for the synthesis of line voltages. Afterwards, works involving the space vector modulation applied in multilevel inverters are related. Then, the SV modulation is developed for a three phase hybrid asymmetric multilevel inverter of nine levels per phase with cascaded Hbridge (CHB). The following steps are performed: definition of the possible switching vectors (switching states) of the proposed inverter in threedimensional space and in the plane αβ; identification of boundary planes and separation plans of sectors in the αβ plane; obtaining the decomposition matrices e; definition of the switching sequence. The results, obtained through mathematical simulation software, of the phase voltages and line voltages graphs, as well as the values of total harmonic distortion (THD), first order distortion factor (DF1), common mode voltage, harmonic spectrum of the voltage signals (phase and line) are analyzed, with THD, DF1 and common mode voltage indices being compared between two different switching sequences for the proposed inverter. In addition, the values of these indices are compared with other modulation techniques (step wave modulation and hybrid modulation). The development and results of the SV modulation simulations in the ninelevel hybrid asymmetric topology proposed, as well as the comparative analyzes, indicate satisfactory results, identifying a great potential for SV modulation developed.

59 
Inversores monofásicos para conexão de sistemas fotovoltaicos à redeMarangoni, Filipe 27 August 2012 (has links)
Esta pesquisa apresenta um estudo comparativo de inversores monofásicos conectados à rede (sem transformador de acoplamento), empregando geradores fotovoltaicos. Inicialmente é destacada a crescente demanda mundial por energia elétrica e o crescimento da utilização de geração através de fontes renováveis, impulsionando o desenvolvimento dessas tecnologias. Também é apresentado um resumo sobre a geração de energia elétrica fotovoltaica descentralizada, incluindo os principais tipos de sistemas e a sua conexão à rede de distribuição da concessionária. Em busca da redução do custo da energia elétrica produzida com geradores fotovoltaicos, a eliminação do transformador de baixa frequência que conecta
o inversor à rede, foi apresentada como uma alternativa interessante. Porém associada à
conexão direta do inversor podem surgir correntes de fuga devido à existência de
capacitâncias parasitas entre as células fotovoltaicas do painel e o potencial de terra do sistema geradorrede. Para evitar esses problemas várias modificações no circuito eletrônico dos inversores têm sido propostas visando eliminar variações na tensão de modo comum destes. Esse trabalho busca avaliar algumas destas topologias visando definir parâmetros de desempenho que possam servir como base para a escolha de uma topologia em detrimento as demais para um conjunto de especificações tais como a potência instalada do gerador ou a amplitude da tensão da rede, dentre outros. / This research presents a comparative study of singlephase transformerless grid
connected inverters, employing photovoltaic generators. Initially is highlighted the increasing worldwide demand for electricity and the growth of the use of renewable sources, driving the development of these technologies. It is also presented an overview of the photovoltaic decentralized power generation, including the major types of systems and their connection to the utility grid. In order to reduce the electricity cost of photovoltaic generation, the elimination of low frequency transformer that connects the inverter to the grid, was presented as an interesting alternative. But associated with the direct inverter connection, leakage currents may arise due to the existence of parasitic capacitances between the panel photovoltaic cell and the system ground. To avoid these problems, several modifications in the electronic circuit of the inverter have been proposed to eliminate variations in the inverter
common mode voltage. This research evaluates some of these topologies in order to define
performance parameters that can serve as the basis for choosing a topology over the other for a set of specifications such as the installed power or the amplitude of grid voltage, among others.

60 
Estudo e implementação de um filtro ativo de potência paralelo aplicado em sistemas trifásicos a quatro fios com controle e modulação vetorialAcordi, Edson Junior 31 August 2012 (has links)
O presente trabalho realiza o estudo e implementação de um filtro ativo de potência paralelo (FAPP) aplicado em sistemas trifásicos a quatro fios utilizando a topologia de um inversor de tensão fourlegs, visando a redução do conteúdo harmônico gerado por cargas não lineares e a compensação de reativos. A geração das correntes de referência de compensação é obtida através da estratégia de compensação baseada no sistema de eixos de referência síncrona (SRF) a qual utiliza conceitos de controle vetorial. O sincronismo do sistema SRF é realizado através de um circuito qPLL (qPhase Locked Loop) o qual é baseado no conceito da teoria da potência instantânea imaginária (teoria pq). A análise matemática da topologia fourlegs é desenvolvida a fim de se obter um modelo linear em espaço de estados que represente o sistema físico para os sistemas de coordenadas abc, αβ0 e dq0. O método de controle proposto é implementado em eixos dq0, através de três controladores do tipo PI (ProporcionalIntegral), os quais são projetados utilizando os conceitos de margem de estabilidade. Um estudo detalhado da modulação Space Vector aplicada a sistemas trifásicos fourlegs é apresentado. Resultados de simulações são apresentados para validar o modelo do filtro proposto bem como a técnica de controle aplicada. Por fim, os resultados experimentais obtidos são avaliados considerando a a recomendação IEEE 5191992 para mostrar a capacidade do FAPP na supressão de correntes harmônicas e compensação de potência reativa. / This work deals with the study and analysis of a parallel active power filter (APF) applied to threephase fourwire systems using a fourleg inverter, aiming the suppresion of the harmonic content of nonlinear loads and reactive power compensation. The generation of the compensation current references is obtained by means of the strategy based on the synchronous reference frame (SRF) system, which utilizes the concepts of vector control. The timing of the SRF system is performed through a qPLL (qPhase Locked Loop) circuit that is based on the imaginary instantaneous power theory. Mathematical analysis is developed in order to obtain a linear model in state space that represents the physical system in the coordinate systems abc, αβ0 and dq0. The proposed control method is implemented in dq0 axes through three ProportionalIntegral (PI) controllers, which are designed using the concepts of stability margin. A detailed study of Space Vector modulation applied to threephase fourleg inverter is presented. Simulation results are presented to validate the model of the APF and the control technique adopted. Finally, experimental results are obtained and evaluated considering the recommendation IEEE 5191992 to show the capability of the parallel APF of current harmonic suppression and reactive power comensation.

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