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

Cascaded multilevel inverter with regeneration capability and reduced number of switches

Abstract—multilevel converters are a very interesting alternative for medium and high power drives. One of the more flexible topologies of this type is the cascaded multicell converter. This paper proposes the use of a single-phase reduced cell suitable for cascaded multilevel converters. This cell uses a reduced singlephase active rectifier at the input and an H-bridge inverter at the output side. This topology presents a very good performance, effectively controlling the waveform of the input current and of the output voltage and allowing operation in the motoring and regenerative mode. The results presented in this paper confirm that this medium voltage inverter effectively eliminates low frequency input current harmonics at the primary side of the transformer and operates without problems in regenerative mod

The Age of Multilevel Converters Arrives

This work is devoted to review and analyze the most relevant characteristics of multilevel converters, to motivate possible solutions, and to show that we are in a decisive instant in which energy companies have to bet on these converters as a good solution compared with classic two-level converters. This article presents a brief overview of the actual applications of multilevel converters and provides an introduction of the modeling techniques and the most common modulation strategies. It also addresses the operational and technological issues

A New Control Technique for Multilevel Cascaded H-Bridge Inverters

Multi cell converters are one of the alternative topologies for medium-voltage industrial drives. For an application modulation (PWM) rectifier as front end Multi level cascaded H-bridge (CHB) converters have been presented as a good solution for high-power applications. The choice of single-phase PWM rectifiers for the input of the cells results in a reduced number of power switches and a simpler input transformer than the three phase equivalent. However, its control is not as straightforward. In this paper, the steady-state power balance in the cells of a single-phase two-cell CHB is studied. The ability to receive active power network or to deliver active power to the grid in each cell is analyzed according to the DC-link voltage and the desired output AC voltage value. Simulation results are shown to validate the presented analysis

MATLAB/SIMLINK Model for Three Phase Hybrid Multilevel Inverter Based on Half Bridge Modules

Nowadays the multilevel inverters are widely used in power electronic applications. The multilevel inverters are recommended for medium and high voltage applications. Multilevel inverters have become more popular due to reduced switching losses, low costs, low harmonic distortion and high voltage capability when compared to traditional PWM inverters. This paper deals with hybrid multilevel converter which is synthesize of neutral point clamped and cascaded multilevel inverter. The hybrid multilevel converter is proposed for medium voltage large power ratings. The proposed converter consisting of voltage source inverter connected with half bridge modules at each phase. With the proposed connection large portion of energy can be preceded by the VSI by connecting single multi pulse rectifier. The smaller power shares processed within the half bridge modules. The modulation scheme for hybrid multilevel inverter is naturally achieved by using logic circuit. The modulation scheme for four-level version is analyzed in detail for higher modulation (HM), three level version is analyzed for lower modulation (LM). This modulation scheme allows unidirectional power flow in all DC sources. For unidirectional application, the diode bridges are employed at rectification input side. The modulation schemes of sinusoidal pulse width modulation (SPWM), space vector PWM (SVPWM) are analyzed by using MATLAB/SIMLINK. The comparison of THD’s for SPWM and SVPWM modulation techniques done by using MATLAB/SIMLINK. Keywords:Hybrid Converters, Multilevel Converters, PWM Modulation, Three Phase Inverters

Z Source Inverter Topologies-A Survey

Need for alternative energy sources to satisfy the rising demand in energy consumption elicited the research in the area of power converters/inverters. An increasing interest of using Z source inverter/converter in power generation involving renewable energy sources like wind and solar energy for both off grid and grid tied schemes were originated from 2003. This paper surveys the literature of Z source inverters/converter topologies that were developed over the years

Addressing control and capacitor voltage regulation challenges in multilevel power electronic converters

Multilevel power electronic converters are the current industry solutions for applications that demand medium voltage, reasonable efficiency, and high power quality. The proper operation of these types of power converters requires special control, modulation methods, and capacitor voltage regulation techniques. Both developing capacitor voltage regulation methods and addressing their associated issues with such fall within the primary focus of this dissertation. In this dissertation an investigation was conducted on the capacitor voltage regulation constraints in cascaded H-bridge multilevel converters with a staircase output voltage waveform. In the proposed method, the harmonic elimination technique is used to determine the switching angles. A constraint was then derived to identify modulation those indices that lead to voltage regulation of the capacitor. This constraint can be used in optimization problems for harmonic minimization to guarantee capacitor voltage regulation in these types of converters. Furthermore, a capacitor voltage regulation method was developed using redundant state selection for a flying capacitor active rectifier. This method reduces the number of switching instances by using both online and offline state selection procedure. Additionally, a start-up procedure is proposed that pre-charges the all of capacitors in the rectifier to both avoid overstressing the switches and obtain a smoother start-up. Finally, a flexible capacitor voltage regulation method is proposed that provides the ability to control the voltage of the capacitors in both cascaded H-bridge and hybrid multilevel converters. In this method, the capacitor voltage in each individual H-bridge cell is independently regulated by controlling the active power of each cell

High-performance motor drives

This article reviews the present state and trends in the development of key parts of controlled induction motor drive systems: converter topologies, modulation methods, as well as control and estimation techniques. Two- and multilevel voltage-source converters, current-source converters, and direct converters are described. The main part of all the produced electric energy is used to feed electric motors, and the conversion of electrical power into mechanical power involves motors ranges from less than 1 W up to several dozen megawatts