Asymmetric Topologies and PWM Modulation Strategy for Low-Cost and High-Quality Single-Phase Multilevel Inverter Choi, Woo-Seok Department of Electrical Engineering Graduate School of Chonnam National University

Asymmetric Topologies and PWM Modulation Strategy for Low-Cost and High-Quality Single-Phase Multilevel Inverter Choi, Woo-Seok Department of Electrical Engineering Graduate School of Chonnam National University (Supervised by Professor : Park, Sung-Jun) 

 (Abstract) Recently, the development of the renewable power industry has been accelerating due to climate change induces to make an effort is the greenhouse gas reduction, and as industrial growth increases the demand for electric power and the electricity generation costs, it has been changing to improve efficiency for power industry structure, and have necessary to develop suitable power converter. Power industry structure has been changing to system minimize demand variation in order to improve grid stability, with low cost. It appears that distributed powers based on renewable power are spreaded over the society at large. In order to fulfill the role of distributed power based on renewable power would be advantageous, using the small size of the distributed power, for grid in stabilized respect. In such cases, many power transmission applications have used the multilevel inverter because the power quality of the renewable distributed power is very important. The multilevel inverter has the advantage of being to generate the output voltage with lower loss and lowr EMC(Electro-Magnetic Compatibility) owing to its low dv/dt stress. The conventional multilevel inverter topologies can include the diode clamped multilevel inverter and flying capacitor multilevel inverter, cascaded multi-cell H-bridge inverter topology. The conventional inverter topologies have a series connection of switch groups, and are usually applied to high power applications with high input/output voltage. However, these topologies have a large increase in the number of switches as the output voltage level increases, and thus are not suitable for the single-phase grid or low voltage applications. The single-phase multilevel topology has the advantage of reducing the number of switches due to lower input/output voltage compared with the conventional multilevel inverter topology. Recently, research into single-phase multilevel inverters has been active as a way to improve power quality. The single-phase multilevel inverter topologies are classified as multilevel inverter based on H-bridge and multilevel inverter based on Half-bridge. This single-phase multilevel inverter based on H-bridge is needed to turn on more than two switches on the one voltage level.
However, the single-phase n-level inverter based on H-bridge is comprised of a smaller number of switches than 2n, and thus a switch is used on more than two output voltage levels.

LINKS
PART1: http://www.mediafire.com/file/ox76ybclip3mphq/SINGLE_PHASE_MULTILEVEL_INVERTER.pdf
PART2 :
http://www.mediafire.com/file/nbqmzi3nas5nkdg/SIMULATION_AND_HARMONIC_ANALYSIS.pdf

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OpenCourseWare Electrical Engineering Hanyang University - Seoul, South Korea 전기공학 한양대학교 박관규

1. Transformer의 특성 이해 및 이를 포함한 회로의 해석

A Study on High Quality Single-Phase Seven-Level Grid-Connected Inverter Department of Electrical Engineering Graduate School, Chonnam National University - Le Tuan Vu

(Abstract)
Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. Multilevel inverters include an array of power semiconductors and capacitor voltage sources, the output of which generate voltages with stepped waveforms. The commutation of the switches permits the addition of the capacitor voltages, which reach high voltage at the output, while the power semiconductors must withstand only reduced voltages. There are three commonly topologies have been proposed for multilevel inverters: diode-clamped (neutralclamped); capacitor-clamped (flying capacitors); and cascaded multicell with separate dc sources. The most attractive features of multilevel inverters are that they can generate output voltages with extremely low distortion, they draw input current with very low distortion and they can operate with a lower switching frequency.
LINK
http://www.mediafire.com/file/4c4wv4gq7t47141/HIGH_QUALITY_SINGLE_PHASE_SEVEN_LEVEL.pdf

A Study of High Resolution Isolated Multi-Level Inverter for Grid-Tie Renewable Generation System by Noh Sik Park Department of Mechatronics Engineering The Graduate School Pukyong National University

A Study of High Resolution Isolated Multi-Level Inverter for Grid-Tie Renewable Generation System 신재생 발전 시스템의 계통 연계를 위한 고정도 절연형 멀티레벨 인버터에 관한 연구 
Advisor: Prof. Soon Jae Kwon 
by Noh Sik Park 
A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Department of Mechatronics Engineering
The Graduate School Pukyong National University February 2009
 ABSTRACT 
 The objective of this paper is to contribute to the commercialization of high resolution 3 phase multi level inverter that uses new control method which is properto thegreatcapacity inverter used for Grid-tiedRenewable GenerationSystem.Forthispurpose,thebasicoperationprincipleandtypes of the conventional multi level inverter is divided to describe the each merit and demerit, the modulation technique applicable to multi level inverter, the domestic and overseas standard and protecting technology of grid-tied technology which is indispensable to grid-tied inverter. The loss for each factor in 3 phase multi level inverter that uses low-frequency transformer was analyzed with structure of 3 phase multi level, theoretic investigationontheregularspacevectormodulationmethodandanewcontrol technique so as to calculate all loss that may occur in the proposed inverter. Further, this research explained the control technique applied to anti-islanding, an essential function of grid-tied inverter and confirmed outputwaveformandTHDforeachrateofmodulationbyusingMatrap/Simulink so as to check the technical feasibility of multi level inverter using 3 phase low-frequency transformer. As 3 phase multi level inverter in 30kW isolate type was designed, produced and experimented, it was confirmed that the performance which was not inferior to that of the existing 2 level inverter method was embodied. Since there is no particular difficulty in productioncomparedtotheexistingproductswhichareproducedbydepending on many know-hows and less part was technically restricted in producing inverter with capacity larger thanthatof inverter produced forresearch, it presents the possibility of localizing power transformer for Grid-tied RenewableGenerationSystemwhichgetslarger
LINK
http://www.mediafire.com/file/vqs3pl4rkq4ezao/A_Study_of_High_Resolution_Isolated_Multi-Level_Inverter_for_Grid-Tied_Renewable_Generation_System.pdf