3,721 research outputs found
The Essential Role and the Continuous Evolution of Modulation Techniques for Voltage-Source Inverters in the Past, Present, and Future Power Electronics
The cost reduction of power-electronic devices, the increase in their reliability, efficiency, and power capability, and lower development times, together with more demanding application requirements, has driven the development of several new inverter topologies recently introduced in the industry, particularly medium-voltage converters. New more complex inverter topologies and new application fields come along with additional control challenges, such as voltage imbalances, power-quality issues, higher efficiency needs, and fault-tolerant operation, which necessarily requires the parallel development of modulation schemes. Therefore, recently, there have been significant advances in the field of modulation of dc/ac converters, which conceptually has been dominated during the last several decades almost exclusively by classic pulse-width modulation (PWM) methods. This paper aims to concentrate and discuss the latest developments on this exciting technology, to provide insight on where the state-of-the-art stands today, and analyze the trends and challenges driving its future
Multilevel Converters: An Enabling Technology for High-Power Applications
| Multilevel converters are considered today as the
state-of-the-art power-conversion systems for high-power and
power-quality demanding applications. This paper presents a
tutorial on this technology, covering the operating principle and
the different power circuit topologies, modulation methods,
technical issues and industry applications. Special attention is
given to established technology already found in industry with
more in-depth and self-contained information, while recent
advances and state-of-the-art contributions are addressed with
useful references. This paper serves as an introduction to the
subject for the not-familiarized reader, as well as an update or
reference for academics and practicing engineers working in
the field of industrial and power electronics.Ministerio de Ciencia y TecnologĂa DPI2001-3089Ministerio de EduaciĂłn y Ciencia d TEC2006-0386
Conventional Space-Vector Modulation Techniques versus the Single-Phase Modulator for Multilevel Converters
Space-vector modulation is a well-suited technique
to be applied to multilevel converters and is an important
research focus in the last 25 years. Recently, a single-phase
multilevel modulator has been introduced showing its conceptual
simplicity and its very low computational cost. In this paper,
some of the most conventional multilevel space-vector modulation
techniques have been chosen to compare their results with those
obtained with single-phase multilevel modulators. The obtained
results demonstrate that the single-phase multilevel modulators
applied to each phase are equivalent with the chosen wellknown
multilevel space-vector modulation techniques. In this
way, single-phase multilevel modulators can be applied to a
converter with any number of levels and phases avoiding the
use of conceptually and mathematically complex space-vector
modulation strategies. Analytical calculations and experimental
results are shown validating the proposed concepts
Multiphase induction motor drives - a technology status review
The area of multiphase variable-speed motor drives in general and multiphase induction motor drives in particular has experienced a substantial growth since the beginning of this century. Research has been conducted worldwide and numerous interesting developments have been reported in the literature. An attempt is made to provide a detailed overview of the current state-of-the-art in this area. The elaborated aspects include advantages of multiphase induction machines, modelling of multiphase induction machines, basic vector control and direct torque control schemes and PWM control of multiphase voltage source inverters. The authors also provide a detailed survey of the control strategies for five-phase and asymmetrical six-phase induction motor drives, as well as an overview of the approaches to the design of fault tolerant strategies for post-fault drive operation, and a discussion of multiphase multi-motor drives with single inverter supply. Experimental results, collected from various multiphase induction motor drive laboratory rigs, are also included to facilitate the understanding of the drive operatio
Feed-forward Space Vector Modulation for Single-Phase Multilevel Cascade Converters with any DC voltage ratio
Modulation techniques for multilevel converters
can create distorted output voltages and currents if the DC link
voltages are unbalanced. This situation can be avoided if the
instantaneous DC voltage error is not taken into account in the
modulation process. This paper proposes a feed-forward space
vector modulation method for a single-phase multilevel cascade
converter. Using this modulation technique, the modulated output
voltage of the power converter always generates the reference
determined by the controller even in worst case voltage unbalance
conditions. In addition the possibility of optimizing the DC
voltage ratio between the H-bridges of the power converter is
introduced. Experimental results from a 5kVA prototype are
presented in order to validate the proposed modulation technique
Evaluation of a dual-T-type converter supplying an open-end winding induction machine
The multilevel inverter is a promising technology compared to two-level inverters in the applications of ac-drives and smart-grid applications. In this paper, a dual-T-type three-level inverters is used to drive an open-end winding induction machine. The Space-Vector Pulse-Width Modulation is selected as a good-performing control strategy to control the dual-inverter. Furthermore, an optimized method is used to select the proper switching state for the new configuration to decrease the converter losses. A comparison between the proposed configuration and the conventional diode clamped converter is made. The proposed drive system is designed and modelled by using Matlab/Simulink. It is shown that the converter can give the same hexagon, wave forms and harmonic spectrum of the five level converter. An optimized switching state selection is used to reduce the converter losses. The advantages and drawbacks of the dual-T-type configuration are discussed. In addition, the harmonic analysis and the loss calculations of the dual-T-type converter are provided and compared to the T-type three-level converter and the conventional five-level diode-clamped-converter
FPGA Implementation of a General Space Vector Approach on a 6-Leg Voltage Source Inverter
A general algorithm of a Space Vector approach is implemented on a 6-leg VSI controlling a PM synchronous machine with three independent phases. In this last case, the necessity of controlling the zero-sequence current motivates the choice of a special family of vectors, different of this one used in Pulse Width Modulation (PWM) intersective strategy and in common Space Vector PWM (SVPWM). To preserve the parallelism of the algorithm and fulfill the execution time constraints, the implementation is made on a Field Programmable Gate Array (FPGA). Comparisons with more classical 2-level and 3-level PWM are provided.Fui8 within the SOFRACI projec
Contributions to Modulation and Control Algorithms for Multilevel Converters
Las actuales tendencias de la red elĂ©ctrica han lanzado a la industria a la bĂșsqueda de sistemas de generaciĂłn, distribuciĂłn y consumo de energĂa elĂ©ctrica mĂĄs eficientes. GeneraciĂłn distribuida, reducciĂłn de componentes pasivos, lĂneas DC de alta tensiĂłn son, entre otras, las posibles lĂneas de investigaciĂłn que estĂĄn actualmente siendo consideradas como el futuro de la red elĂ©ctrica. Sin embargo, nada de esto serĂa posible si no fuera por los avances alcanzados en el campo de la electrĂłnica de potencia.
El trabajo aquĂ presentado comienza con una breve introducciĂłn a la electrĂłnica de potencia, concretamente a los convertidores de potencia conectados a red, sus estrategias de control mĂĄs comunes y enfoques ante redes desbalanceadas. A continuaciĂłn, las contribuciones del autor sobre el control y modulaciĂłn de una topologĂa particular de convertidores, conocidos como convertidores multinivel, se presentan como el principal contenido de este trabajo. Este tipo de convertidores mejoran la eficiencia y ciertas prestaciones, en comparaciĂłn con convertidores mĂĄs tradicionales, a costa de una mayor complejidad en el control al incrementar la cantidad de los componentes hardware.
A pesar de que existen numerosas topologĂas de convertidores multinivel y algunas de ellas son brevemente expuestas en este trabajo, la mayorĂa de las aportaciones estĂĄn enfocadas para convertidores del tipo diode-clamped converter. Adicionalmente, se incluye una aportaciĂłn para convertidores del tipo multinivel modular, y otra para convertidores en cascada.
Se espera que el contenido de la introducciĂłn de este trabajo, junto a las contribuciones particulares para convertidores multinivel sirva de inspiraciĂłn para futuros investigadores del campo
Coconut dehusker machine
Generally, coconut is dehusked manually using either a machete or a spike. These methods required skill labor and tiring to use. Attempts made so far in development of dehusking tools have been only partially successful and not effective in replacing manual methods. The reasons quoted for the failure of these tools include unsatisfactory and incomplete dehusking, breakage of the coconut shell while dehusking, spoilage of useful coir, greater effort needed than manual methods, etc
Direct usage of photovoltaic solar panels to supply a freezer motor with variable DC input voltage
In this paper, a single-phase photovoltaic (PV) inverter fed by a boost converter to supply a freezer motor with variable DC input is investigated. The proposed circuit has two stages. Firstly, the DC output of the PV panel that varies between 150 and 300 V will be applied to the boost converter. The boost converter will boost the input voltage to a fixed 300 V DC. Next, this voltage is supplied to the single-phase full-bridge inverter to obtain 230 V AC. In the end, The output of the inverter will feed a freezer motor. The PV panels can be stand-alone or grid-connected. The grid-connected PV is divided into two categories, such as with a transformer and without a transformer, a transformer type has galvanic isolation resulting in increasing the security and also provides no further DC current toward the grid, but it is expensive, heavy and bulky. The transformerless type holds high efficiency and it is cheaper, but it suffers from leakage current between PV and the grid. This paper proposes a stand-alone direct use of PV to supply a freezer; therefore, no grid connection will result in no leakage current between the PV and Grid. The proposed circuit has some features such as no filtering circuit at the output of the inverter, no battery in the system, DC-link instead of AC link that reduces no-loads, having a higher efficiency, and holding enough energy in the DC-link capacitor to get the motor started. The circuit uses no transformers, thus, it is cheaper and has a smaller size. In addition, the system does not require a complex pulse width modulation (PWM) technique, because the motor can operate with a pulsed waveform. The control strategy uses the PWM signal with the desired timing. With this type of square wave, the harmonics (5th and 7th) of the voltage are reduced. The experimental and simulation results are presented to verify the feasibility of the proposed strategy
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