Overview of three-phase inverter topologies for distributed generation purposes

The increasing presence of single-phase distributed generators and unbalanced loads in the electric power system may lead to unbalance of the three phase voltages, resulting in increased losses and heating. Distribution network operators are seeking to install larger DG units (viz. $>5$kVA in Belgium) by means of three-phase connections instead of single-phase to reduce voltage unbalance. There are several possible topologies to connect the DG units to the three-phase distribution network. These topologies can be divided into three groups: the three-phase three-wire inverters, the three-phase four-wire inverters and the multilevel inverters. In this paper, an overview of the aforementioned topologies is given

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

A cascaded NPC/H-bridge inverter with simplifiied control strategy and minimum component count

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A novel 9-level multilevel inverter based on 3-level NPC/H-bridge topology for photovoltaic applications

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Cascaded Converters For Integration And Management Of Grid Level Energy Storage Systems

ABSTRACT CASCADED CONVERTERS FOR INTEGRATION AND MANAGEMENT OF GRID-LEVEL ENERGY STORAGE SYSTEMS by ZUHAIR ALAAS December 2017 Advisor: Dr. Caisheng Wang Major: ELECTRICAL ENGINEERING Degree: Doctor of Philosophy This research work proposes two cascaded multilevel inverter structures for BESS. The gating and switching control of switching devices in both inverter typologies are done by using a phase-shifted PWM scheme. The first proposed isolated multilevel inverter is made up of three-phase six-switch inverter blocks with a reduced number of power components compared with traditional isolated CHB. The suggested isolated converter has only one battery string for three-phase system that can be used for high voltage and high power applications such as grid connected BESS and alternative energy systems. The isolated inverter enables dq frame based simple control and eliminates the issues of single-phase pulsating power, which can cause detrimental impacts on certain dc sources. Simulation studies have been carried out to compare the proposed isolated multi-level inverter with an H-bridge cascaded transformer inverter. The simulation results verified the performance of the isolated inverter. The second proposed topology is a Hierarchal Cascaded Multilevel Converter (HCMC) with phase to phase SOC balancing capability which also for high voltage and high power battery energy storage systems. The HCMC has a hybrid structure of half-bridge converters and H-bridge inverters and the voltage can be hierarchically cascaded to reach the desired value at the half-bridge and the H-bridge levels. The uniform SOC battery management is achieved by controlling the half-bridge converters that are connected to individual battery modules/cells. Simulation studies and experimental results have been carried on a large scale battery system under different operating conditions to verify the effectiveness of the proposed inverters. Moreover, this dissertation presents a new three-phase SOC equalizing circuit, called six-switch energy-level balancing circuit (SSBC), which can be used to realize uniform SOC operation for full utilization of the battery capacity in proposed HCMC or any CMI inverter while keeping balanced three-phase operation. A sinusoidal PWM modulation technique is used to control power transferring between phases. Simulation results have been carried out to verify the performance of the proposed SSBC circuit of uniform three-phase SOC balancing

A cascaded hybrid inverter with improved dc-link voltage control for grid connected systems

Abstract: This paper presents investigation of a new Phase shifted PWM technique with improved harmonic suppression. A novel balance circuit for DC – link voltage balance of two three level legs connected back – to back is designed and tested. Combined with the individual voltage control, a complete voltage controller is developed for a cascaded nine level hybrid model with two cells. Robustness of the proposed algorithm under varying operating conditions and modulation indices is verified by simulation

Asymmetric Cascaded Multilevel Inverter with Unequal Dc Sources using SPWM and MSVPWM Topologies

This paper introduces the modeling design and simulation of seven and thirteen levels cascaded asymmetric multilevel inverter (MLI) with reduced number of switches.  MLI is the most efficient energy converters which are essentially appropriated for high power applications with decrease total harmonics distortion (THD). MLI doesn't only get high power in the output but it is also utilized in renewable energy resources such as fuel cells, wind and photovoltaic cells. This paper principally focuses on a hybrid cascaded MLI with two and three unequal dc supplies which decreases the number of semiconductor power switches. Sinusoidal PWM (SPWM) and modified space vector PWM (MSVPWM) techniques are used to improve an ac output with reduced THD. The gating pulses for seven and thirteen level hybrid cascaded converter using SPWM and MSVPWM techniques are introduced. The results of these proposed modulation strategies reduce the percentage magnitude of THD. The performance of the proposed SPWM and MSVPWM topologies are verified using seven and thirteen levels cascaded asymmetric MLI via simulink/matlab. Keywords: Sinusoidal Pulse Width Modulation (SPWM), Modified Space Vector Pulse Width Modulation (MSVPWM), Multilevel Inverter (MLI), Total Harmonics Distortion (THD)

Operating strategies and capacitor voltace balance strategies for a cascaded "3-5-9" hybrid inverter for grid interface application

Abstract: The paper presents a novel phase shifted SPWM control scheme for cascading two cells to form a “3-5-9 hybrid inverter with improved harmonic suppression. Modeling of the hybrid inverter from first principle is introduced and a standard control law is derived for further analysis and development of the model. A new balance circuit for DC link voltage control is designed and tested. Combined with individual voltage control, a complete control scheme is developed. Detailed MATLAB simulation and experimental results are obtained for further validation of the adopted topology and the control schem