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 Tecnología DPI2001-3089Ministerio de Eduación y Ciencia d TEC2006-0386

Variable-Angle Phase-Shifted PWM for Multilevel Three-Cell Cascaded H-bridge Converters

Multilevel cascaded H-bridge converters have become a mature technology for applications where high-power medium ac voltages are required. Normal operation of multilevel cascaded H-bridge converters assumes that all power cells have the same dc voltage, and each power cell generates the same voltage averaged over a sampling period using a conventional phase-shifted pulse width modulation (PWM) technique. However, this modulation method does not achieve good results under unbalanced operation per H-bridge in the power converter, which may happen in grid-connected applications such as photovoltaic or battery energy storage systems. In the paper, a simplified mathematical analysis of the phase-shifted PWM technique is presented. In addition, a modification of this conventional modulation method using variable shift angles between the power cells is introduced. This modification leads to the elimination of harmonic distortion of low-order harmonics due to the switching (triangular carrier frequency and its multiples) even under unbalanced operational conditions. The analysis is particularized for a three-cell cascaded H-bridge converter, and experimental results are presented to demonstrate the good performance of the proposed modulation method

A Review on Control Strategies and Topologies of Multi Level Converter System

In recent decades, high-performance and medium voltage energy management for academia and industry have been attracted by multi-level converter topologies. In addition, the multi-level principle is used without decreasing the inverter power output to synthesise the harmonic distortion on the output waveform. For the reduction of harmonic distortion in the output waveform, the multi-level principle is used. The following topologies are presented: diode clamped inverters (neutral point clamped), condenser clamped (flying condenser), multi-level cascading (dc source, etc.) and the most effective modulation methods built for this converter category: multi-level, selective harmonic removal and space m vectors. A series of different topologies are given in this paper. Multi-level inverters have been gaining popularity in research teams and in the production of industrial applications for high and medium voltage applications for 20 years. Moreover, compared to a conventional converter, multi-level inverters can generate switched waveforms with reduced harmonic slopes. Recently, multi-level inverters have increased interest in their ability to generate high-quality wave forms at lower frequencies; the multi-level topology used in dynamic restaurant voltages reduces the harmonic distortion of the inverter output waveform without inverter output losses. By integrating control techniques for multi-level inverters, this paper discusses the most common topologies, making their implementations flexible in some power applications in many industrial areas

Pengaruh adukan dan kepekatan partikel silicon karbida sebagai penguat terhadap kelakuan salutan komposit matriks nikel

Affordable quality housing is vital in developing countries to meet its growing population. Development of a new cost effective system is crucial to fulfill these demands. In view of this, a study is carried out to develope a Precast Lightweight Foamed Concrete Sandwich Panel (PLFP), as a new affordable building system. Experimental investigation and finite element analysis to study the structural behaviour of the PLFP panel under axial load is undertaken. The panel consists of two foamed concrete wythes and a polystyrene insulation layer in between the wythes. The wythes are reinforced with high tensile steel bars and tied up to each other through the polystyrene layer by steel shear connectors bent at an angle of 45º. The panels are loaded with axial load until failure. The ultimate load carrying capacity, load-lateral deflection profile, strain distributions, and the failure mode are recorded. Partial composite behaviour is observed in all specimens when the cracking load is achieved. Finite element analysis is also carried out to study the effect of slenderness ratio and shear connectors which are the major parameters that affect the strength and behaviour of the panels. An empirical equation to predict the maximum load carrying capacity of the panels is proposed. The PLFP system proposed in this research is able to achieve the intended strength for use in low rise building. Considering its lightweight and precast construction method, it is feasible to be developed further as a competitive IBS building system

Power Quality Enhancement in Electricity Grids with Wind Energy Using Multicell Converters and Energy Storage

In recent years, the wind power industry is experiencing a rapid growth and more wind farms with larger size wind turbines are being connected to the power system. While this contributes to the overall security of electricity supply, large-scale deployment of wind energy into the grid also presents many technical challenges. Most of these challenges are one way or another, related to the variability and intermittent nature of wind and affect the power quality of the distribution grid. Power quality relates to factors that cause variations in the voltage level and frequency as well as distortion in the voltage and current waveforms due to wind variability which produces both harmonics and inter-harmonics. The main motivation behind work is to propose a new topology of the static AC/DC/AC multicell converter to improve the power quality in grid-connected wind energy conversion systems. Serial switching cells have the ability to achieve a high power with lower-size components and improve the voltage waveforms at the input and output of the converter by increasing the number of cells. Furthermore, a battery energy storage system is included and a power management strategy is designed to ensure the continuity of power supply and consequently the autonomy of the proposed system. The simulation results are presented for a 149.2 kW wind turbine induction generator system and the results obtained demonstrate the reduced harmonics, improved transient response, and reference tracking of the voltage output of the wind energy conversion system.Peer reviewedFinal Accepted Versio

A Reduced Switch Asymmetric Multilevel Inverter Topology Using Unipolar Pulse Width Modulation Strategies for Photovoltaic Application

A new design of multilevel inverter configuration is proposed for reducing the component count and improving the quality of waveform in a photovoltaic system. The proposed configuration operates at the binary asymmetric condition for generating the large amount output voltage level with small amount harmonic distortion. Unipolar trapezoidal reference with triangular carriers is used for generating the desired switching pulses to generate the required output voltage level. The proposed configuration requires eight unipolar switches for generating the 31-level output voltage level with total harmonic distortion of 3.18% without using any filters. The value of %total harmonic distortion (THD) satisfies the IEEE 519 harmonic standard. Separate DC sources of proposed configuration are replaced by the array of photovoltaic panels for testing the configuration with the renewable energy source. The proposed configuration is tested with an experimental setup for proving the operation of it. Selected simulation and experimental results are shown for the verification of proposed configuration ability

GRID INTEGRATION OF SOLAR PHOTOVOLTAIC SYSTEM USING 25LEVEL SUB-MULTILEVEL INVERTER.

The sub-multilevel electrical inverter could be a replacement topology for multilevel Inverters that are improved or advanced multilevel inverter topology. The projected sub-multilevel inverter uses a reduced range of switching devices and series association within the Power circuit while not compensating the levels. The multilevel inverters are within the center of attraction for the researchers in recent years. this is often owing to it holds advantageous feature to produce improved power quality. The proposed scheme of 25Level sub-multilevel electrical inverter tends to produce a generalized kind to the multilevel inverters that may produce a nearly sinusoidal output voltage. output voltage quality depends on the number of voltage levels of the inverter. Special attention is required to induce the most effective sub-multilevel concerning criteria just like the range of switches, standing voltage on the switches, the range of DC voltage sources, number of output voltage levels on switches and so. the foremost motivation behind this inverter topology is to realize the high power quality, low total harmonic distortion, less magnetic attraction interference, lesser the higher power stability, and reliability. The Simulation strategies of voltage responses and THD responses for asymmetric and symmetric photovoltaic array associated with the three-phase 25-level CSMLI(cascaded Sub- multilevel Inverters) are being carried under the MATLAB environment

MATLAB-Simulink environment based power quality improvement in photovoltaic system using multilevel inverter

Introduction. In this world of technical advancement, conventional resources are at the stage of destruction. To avoid such problems, we are going to use an alternative energy source namely solar by photovoltaic effect. The demand for multilevel inverters increased as they are used for different dynamic (high) voltage and dynamic (high) power appliances as they are capable of producing the output wave shape with low total harmonic distortion. Novelty. A new multilevel inverter is used in adding a (bidirectional) two way switch in between the capacitor and a traditional H-bridge module. This produces a better sine wave. By series connection of these two H-bridge modules, nine levels output voltage including zero is possible. The purpose of the proposed topology is reduction in the number of switches and it gives the good result with comparatively less power loss when it is compared with the other normal basic traditional inverters of the same output quality. Methods. In this paper, sinusoidal pulse width modulation technique is used for the working of the switches in the multilevel inverter. The results are verified by using simulation and also experimental setup is done. From the results it is observed that the proposed topology with reduced number of switches gives lower electromagnetic interference, lower harmonic distortion. Practical value. The total harmonic distortion value in the simulation is 14.4 % and practically it is 13.8 %.Вступ. У світі технічного прогресу звичайні ресурси перебувають у стадії руйнації. Щоб уникнути таких проблем, ми збираємося використати альтернативне джерело енергії, а саме сонячну енергію з фотоелектричним ефектом. Попит на багаторівневі інвертори збільшився, оскільки вони використовуються для різних динамічних (високих) напруг та динамічних (високих) потужностей, оскільки вони здатні формувати вихідну форму хвилі з низьким гармонічним загальним спотворенням. Новизна. Новий багаторівневий інвертор використовується для додавання двостороннього перемикача між конденсатором і традиційним модулем Н-моста. Це дає найкращу синусоїду. При послідовному з’єднанні двох модулів Н-моста можливо дев’ять рівнів вихідної напруги, включаючи нуль. Метою запропонованої топології є зменшення кількості перемикачів, що дає хороший результат при порівняно менших втратах потужності порівняно з іншими традиційними звичайними інверторами з такою ж вихідною якістю. Методи. У цій статті для роботи перемикачів у багаторівневому інверторі використовується метод широтно-імпульсної синусоїдальної модуляції. Результати перевіряються за допомогою моделювання, а також виконується експеримент. З результатів видно, що пропонована топологія зі зменшеною кількістю перемикачів дає менші електромагнітні перешкоди, менші гармонійні спотворення. Практична цінність. Сумарне значення гармонійних спотворень при моделюванні складає 14,4 %, а практично – 13,8 %