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

2 1 The innovative transport systems and the CityMobil project 10 1.1 The research questions 10 2 The state of art in the field of automatic transport systems 12 2.1 Case studies and demand studies for innovative transport systems 12 3 The design and implementation of surveys 14 3.1 Definition of experimental design 14 3.2 Questionnaire design and delivery 16 3.3 First analyses on the collected sample 18 4 Calibration of Logit Multionomial demand models 21 4.1 Methodology 21 4.2 Calibration of the “full” model. 22 4.3 Calibration of the “final” model 24 4.4 The demand analysis through the final Multinomial Logit model 25 5 The analysis of interaction between the demand and socioeconomic attributes 31 5.1 Methodology 31 5.2 Application of Mixed Logit models to the demand 31 5.3 Analysis of the interactions between demand and socioeconomic attributes through Mixed Logit models 32 5.4 Mixed Logit model and interaction between age and the demand for the CTS 38 5.5 Demand analysis with Mixed Logit model 39 6 Final analyses and conclusions 45 6.1 Comparison between the results of the analyses 45 6.2 Conclusions 48 6.3 Answers to the research questions and future developments 52

The European commission

Renewable energy sources like wind, sun, and hydro are seen as a reliable alternative to the traditional energy sources such as oil, natural gas, or coal. Distributed power generation systems (DPGSs) based on renewable energy sources experience a large development worldwide, with Germany, Denmark, Japan, and USA as leaders in the development in this field. Due to the increasing number of DPGSs connected to the utility network, new and stricter standards in respect to power quality, safe running, and islanding protection are issued. As a consequence, the control of distributed generation systems should be improved to meet the requirements for grid interconnection. This paper gives an overview of the structures for the DPGS based on fuel cell, photovoltaic, and wind turbines. In addition, control structures of the grid-side converter are presented, and the possibility of compensation for low-order harmonics is also discussed. Moreover, control strategies when running on grid faults are treated. This paper ends up with an overview of synchronization methods and a discussion about their importance in the control

/pdf/overview-of-control-and-grid-synchronization-for-distributed-2nx31ovpe9.pdf

Overview of Control and Grid Synchronization for Distributed Power Generation Systems

DC and AC Microgrids are key elements to integrate renewable and distributed energy resources as well as distributed energy storage systems. In the last years, efforts toward the standardization of these Microgrids have been made. In this sense, this paper present the hierarchical control derived from ISA-95 and electrical dispatching standards to endow smartness and flexibility to microgrids. The hierarchical control proposed consist of three levels: i) the primary control is based on the droop method, including an output impedance virtual loop; ii) the secondary control allows restoring the deviations produced by the primary control; and iii) the tertiary control manage the power flow between the microgrid and the external electrical distribution system. Results from a hierarchical-controlled microgrid are provided to show the feasibility of the proposed approach.

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Hierarchical control of droop-controlled DC and AC microgrids — a general approach towards standardization

The use of distributed energy resources is increasingly being pursued as a supplement and an alternative to large conventional central power stations. The specification of a power-electronic interface is subject to requirements related not only to the renewable energy source itself but also to its effects on the power-system operation, especially where the intermittent energy source constitutes a significant part of the total system capacity. In this paper, new trends in power electronics for the integration of wind and photovoltaic (PV) power generators are presented. A review of the appropriate storage-system technology used for the integration of intermittent renewable energy sources is also introduced. Discussions about common and future trends in renewable energy systems based on reliability and maturity of each technology are presented

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Power-Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey

This study deals with η ρ (efficiency-power density) pareto optimisation of medium frequency transformers (MFTs) with considerations of voltage and frequency (Vf) constraints of semiconductors for mega-watt range input-series output-parallel (ISOP) connected dual-active bridges (DABs). A simple design methodology to include the Litz wire configuration in the optimisation process is proposed. Based on the presented design methodology, the effects of the semiconductors blocking voltage and switching frequency on the η ρ -pareto optimisation are evaluated. First, an idealised optimisation is carried out to understand the general behaviour of the optimum point. Second, brute-force optimisation is utilised to find the practical optimum solution based on the market availability of MFT components. Designing MFTs for a 1 MW 10 kV/600 V ISOP-DAB converter is the subject of numerical studies. The best trade-off between η ρ and V f is selected as the final optimal solution and its design correctness is validated using three-dimensional finite-element analysis. Experimental tests on a 3 kW downscaled MFT prototype show that the proposed method is valid in practice.

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Vf-constrained ηρ-pareto optimisation of medium frequency transformers in ISOP-DAB converters

Back-to-back converters for wind turbine systems (WTS) feature capacitors in the DC-link to maintain a stable DC-link voltage and to decouple the generator from the grid. Electrolytic and film capacitors can be chosen to this purpose. Long-term field experience and recorded failure data reveal that capacitor failures are one of the main reasons for the downtime of WTS. The ripple current accelerates the wear-out of the capacitors, which is strongly dependent on the mission profile of the system. Therefore, it becomes important to estimate the useful lifetime of a capacitor as a function of the ripple current. In this paper, aging characteristics of electrolytic capacitors are described, and a power converter topology and its control strategy are designed to perform accelerated lifetime tests. The voltage and ripple current of the capacitor under test (CUT) can be controlled with low THD to correlate wear-out with ripple.

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Topology and control strategy for accelerated lifetime test setup of DC-link capacitor of wind turbine converter

The current control techniques developed on the basis of the internal model principle (IMP) are well suited for the single-phase photovoltaic systems. The main achievements of these controllers have been: sinusoidal grid current, unity power factor and high immunity to grid harmonic disturbances. Two main families of current controllers have been developed: the first based on the use of resonant controllers and the second based on the use of repetitive controllers. Similarities have been already individuated between these two classes of controllers, however many different implementation possibilities arise (use of selective, full, or any grid voltage feed-forward, implementation via the delta operator or zeta operator, etc.). This paper proposes an exhaustive comparison between these classes of controllers, full of insight judgment, and based on simulation and experimental results.

Performance Comparison of Current Controllers with Harmonic Compensation for Single-Phase Grid converter

In this paper, a three-port, galvanic isolated, bidirectional power converter is proposed to control the power flow between the main dc buses, low voltage loads and energy storage unit on a generic airplane. A simplified model of the converter is presented to explain the control strategies design procedure. Simulations of the developed closed-loop controller that manages the energy exchange in different operating conditions are provided. Finally, a laboratory prototype based on GaN power devices is described and basic experimental results are presented.

GaN-based triple active bridge for avionic application

This special issue honors Dr. Bimal K. Bose and this editorial includes an interview with Dr. Bose.

Marco Liserre

Papers

Vf-constrained ηρ-pareto optimisation of medium frequency transformers in ISOP-DAB converters

Topology and control strategy for accelerated lifetime test setup of DC-link capacitor of wind turbine converter

Performance Comparison of Current Controllers with Harmonic Compensation for Single-Phase Grid converter

GaN-based triple active bridge for avionic application

Dr. Bimal K. Bose: A reference for generations [Editor's Column]