다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<<ETX>>

Multi-level conversion : high voltage choppers and voltage-source inverters

Cascaded multilevel inverter (CMI) is one of the most popular multilevel inverter topologies. This topology is synthesized with some series-connected identical H-bridge cells. CMI requires several isolated dc sources which brings about some difficulties when dealing with this type of inverter. This paper addresses the problem by proposing a switched-capacitor (SC)-based CMI. The proposed topology, which is referred to as switched-capacitor single-source CMI (SCSS-CMI), makes use of some capacitors instead of the dc sources. Hence, it requires only one dc source to charge the employed capacitors. Usually, the capacitor charging process in a SC cell is companied by some current spikes which extremely harm the charging switch and the capacitor. The capacitors in SCSS-CMI are charged through a simple auxiliary circuit which eradicates the mentioned current spikes and provides zero-current switching condition for the charging switch. A computer-aid simulated model along with a laboratory-built prototype is adopted to assess the performances of SCSS-CMI, under different conditions.

Switched-Capacitor-Based Single-Source Cascaded H-Bridge Multilevel Inverter Featuring Boosting Ability

Due to the possibility of providing energy with much less dependence on the fossil fuels, renew-competent energy sources, in specified sun photovoltaic (PV) conversion have received elevated acceptance and progress in latest times. Big benefits of PV panels comprise easy and trustworthy power production and suitability for disbursed iteration. In addition the costs for photovoltaic modules is drastically lowering. To comprehend this issue, a control plan with modulation compensation scheme is likewise proposed. An exploratory three-stage seven-level cascaded H-bridge inverter has been manufactured using nine H-bridge modules (three modules for each stage). Each H-bridge module is associated with a 185-W solar panel. Simulation results are introduced to confirm the practicality of the proposed approach.

Modular Cascaded H-Bridge Multilevel PV Inverter with Distributed MPPT for Grid-Connected Applications

Multilevel inverters (MLIs) have gained increasing interest for advanced energy-conversion systems due to their features of high-quality produced waveforms, modularity, transformerless operation, voltage, and current scalability, and fault-tolerant operation. However, these merits usually come with the cost of a high number of components. Over the past few years, proposing new MLIs with a lower component count has been one of the most active topics in power electronics. The first aim of this article is to update and summarize the recently developed multilevel topologies with a reduced component count, based on their advantages, disadvantages, construction, and specific applications. Within the framework, both single-phase and three-phase topologies with symmetrical and asymmetrical operations are taken into consideration via a detailed comparison in terms of the used component count and type. The second objective is to propose a comparative method with novel factors to take component ratings into account. The effectiveness of the proposed method is verified by a comparative study.

Voltage Source Multilevel Inverters With Reduced Device Count: Topological Review and Novel Comparative Factors

The cascaded H-bridge multilevel inverter (CMI) is one of the most popular converters, especially in renewabale energy applications. Beyond offering some significant benefits, this inverter suffers from the drawback of employing great number of components which reduces the reliability of the inverter. Thus, designing a scheme to enhance reliability in this kind of inverter is of crucial importance. In this paper, a fault-tolerant structure for the cascaded H-bridge multilevel inverter is designed. Failure rates of the switches and diodes are calculated. Then, by using the Markov method, reliability and mean time to failure (MTTF) of the mentioned inverter, before and after employing the suggested scheme, are evaluated. In order to prove proper performance of the suggested scheme, a laboratory built prototype is employed. The results show that employing the suggested scheme significantly enhances reliability and MTTF of the inverter.

Reconfigurable Multilevel Inverter With Fault-Tolerant Ability

The main problem related to cascaded H-bridge (CHB) cell multilevel inverters is their using of a large number of components, such as switches and dc-sources. Therefore, minimization of components in these kinds of devices is of great importance. Cascaded-transformer multilevel inverters (CTMIs) have completely eliminated the need for several dc-sources in CHBs. Thus, minimization of the other components in CTMIs can lead to obtain an optimized structure for multilevel inverters. This paper introduces a simple and compact structure for transformer-based multilevel inverters. Since the number of utilized components in the proposed structure is remarkably reduced, the cost, volume, and complexity are minimized. The performance of the suggested inverter has been scrutinized through two different strategies. First, it is tested under condition of supplying a local load, and second, employing sample-based current control strategy; its performance is inspected when being connected to the grid. In the latter test, the leakage inductances of the transformers are utilized to execute the sample-based current control strategy, thus, the need for extra filter is eradicated. The feasibility of the suggested topology has been validated by using the laboratory-built prototype along with a computer-aided simulated model.

Verification of a Low Component Nine-Level Cascaded-Transformer Multilevel Inverter in Grid-Tied Mode

Cascaded H-bridge Multilevel Inverter (CMI) attracts much attention as a versatile converter in photovoltaic (PV) applications. Requiring several isolated dc sources and many switches are the main demerits of the CMI. In PV applications with the CMI, PV modules can be used as the isolated dc sources, which, however, may contribute to intermodule and grid leakage currents due to the module stray capacitors. In this context, a switched-capacitor-based cascaded half-bridge multilevel inverter is proposed in this paper to address the above issues. The proposed topology only requires one dc source, and it achieves the minimum number of switches, spontaneous capacitor charging, voltage boosting, and continuous input current. The inter-module leakage currents can also be eliminated in the proposed topology. The feasibility and effectiveness of the proposed topology are validated through simulations and experimental tests.

/pdf/a-multilevel-inverter-with-minimized-components-featuring-2mtu63shhw.pdf

A Multilevel Inverter with Minimized Components Featuring Self-balancing and Boosting Capabilities for PV Applications

Requiring lots of components is the main demerit of multilevel inverters. This problem makes them expensive, bulky, and with a high possibility of failure. Therefore, the issue of components reduction in multilevel topologies is of great importance. Cascaded transformers multilevel inverter (CTMI) is a converter that employs only one DC-source, thus it eliminates the need for several DC-sources. Same as the other multilevel inverters, CTMI consists of lots of components. This disadvantage of CTMI has been resolved through a new reduced components topology introduced in the present work. This topology uses almost half the number of switching elements, such as power switch and gate driver, which are required to construct a conventional CTMI for the same output voltage levels. Furthermore, to the end of enhancing the reliability of CTMI, this paper, using Markov reliability evaluation approach and evaluating the reliability and the Mean Time To Failure (MTTF) of the converters, has investigated the reliability of both the conventional and the proposed structures. Additionally, in order to prove the feasibility and correctness of the suggested topology computer aid simulation results along with the experimental results have been provided.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-pel.2016.0787

Hossein Khoun Jahan

Papers

Switched-Capacitor-Based Single-Source Cascaded H-Bridge Multilevel Inverter Featuring Boosting Ability

Reconfigurable Multilevel Inverter With Fault-Tolerant Ability

Verification of a Low Component Nine-Level Cascaded-Transformer Multilevel Inverter in Grid-Tied Mode

A Multilevel Inverter with Minimized Components Featuring Self-balancing and Boosting Capabilities for PV Applications

Low component merged cells cascaded-transformer multilevel inverter featuring an enhanced reliability