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

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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

The power electronics-based Smart Transformer (ST) can increase the hosting capacity of Distributed Generators (DGs) as well as electric vehicle charging stations and potentially reduce the reinforcements in the distribution grid by providing the DC connectivities and optimizing the capability in the secondary substations. Due to the asynchronous behaviour between the power generation in DGs and load consumption, the ST will operate in asymmetrically bidirectional power flow conditions. The power electronics in the ST can be fully used under the forward power flow condition, while only be partially used under the reverse power flow condition. This paper proposes a Bidirectional-Asymmetrical DC/DC converter in ST to reduce the cost of the power semiconductors and to satisfy the ST operating in bidirectional requirement. Under forward operation mode, the power sharing between two paralleled full bridge rectifiers in the secondary side of the proposed converter is studied and then the output impedance reshaping solution is presented to improve the dynamic performance of the output voltage under load disturbances. The simulation results clearly validate the effectiveness and feasibility of the proposed converter.

High Performances Voltage Control of Bidirectional-Asymmetrical DC/DC Converter in Smart Transformer for Limited Reverse Power Flow

In this article, a three-phase voltage-source converter (VSC)-based isolated matrix-type ac/dc converter is proposed for wind energy conversion system. The line-frequency transformer is replaced by the high-frequency transformer (HFT), and there is no need for the intermediate electrolytic capacitors used in conventional two-stage power conversion system. Moreover, the bidirectional switches used for conventional matrix converter are eliminated in the proposed topology. Consequently, the complicated four-step commutation scheme is avoided and the additional conduction loss caused by serial connection of power switches can be eliminated. The proposed isolated matrix-type ac/dc can be regarded as the dual VSC circuit, where two VSCs alternately work during each switching cycle. Hence, the voltage vectors-based space vector modulation can be employed and the control schemes for nonisolated VSCs can be used for the proposed converter. For safe operation, the commutation strategy is proposed for the leakage-inductor current of HFT. Both simulations and experiments are conducted to verify the performance of the proposed converter.

A VSC-Based Isolated Matrix-Type AC/DC Converter Without Bidirectional Power Switches

In solid-state transformer (SST) applications, the multiport non-resonant converter became a standard solution for the dc/dc stage, mainly because of its simple power flow control. However, little attention was given to the multiport resonant topologies, which have several benefits in terms of soft-switching and power flow capability when operating as a DC-transformer (DCX). The high performance of the multiport resonant converter has not yet been demonstrated in the literature. Thus, a multiport resonant converter operating as DCX is proposed to enhance the power flow management, efficiency, and cost of the SST, without requiring any additional control strategy. For this purpose, the resonant multiport converter based on CLLC (fully bidirectional) and LLC (partially unidirectional) topologies are analyzed and designed as the basic power electronic building block (PEBB) for the SST's dc/dc stage. Finally, experimental results of a 20 kW multiport DCX are shown to prove the effectiveness of the design approach, and the correctness of the theoretical analysis. Experimental results for the designed DCX of 20 kW have shown a peak efficiency of 97.5 %.

Analysis and Design of a Multiport Resonant DC-Transformer for Solid-State Transformer Applications

Power converters, and particularly multilevel converters, are key elements in the current energy scenario. Among them, cascaded H-bridge converters are a popular and versatile solution for many industrial applications. Technical literature provides multiple modulation techniques for its operation. Among them, hybrid pulsewidth modulation techniques provide a good tradeoff between switching loss and output voltage quality. In this article, a hybrid modulation technique is presented, which allows not only the fundamental block switching operation of some power cells but also a harmonic control over a specific harmonic distortion present in the grid. To validate the operation of the proposal, several experimental results have been reported to demonstrate the good behavior of the proposed modulation technique.

A Hybrid Modulation Technique for Operating Medium-Voltage High-Power CHB Converters Under Grid Voltage Disturbances

The dual-side control (DSC) of inductive power transfer (IPT) generally requires communication between the system sides to coordinate the local controllers. For the reduction of component count and operation in challenging environments, such as underwater, communicationless DSC is beneficial. This article investigates if and how asymmetric modulations, known for their improved performance in IPT, can be applied to phase cooperative communicationless DSC. A per side separate steady-state model is derived, and the selection criteria for modulation schemes to be suitable for phase cooperative control are determined. The crucial importance of bijective or unique phase behavior in modulations for this control scheme is identified and demonstrated. In comparison with phase modulation, it is shown that the asymmetric voltage cancelation of full-bridges is not reliably applicable to phase cooperative DSC, but the asymmetrical modulation of half-bridges is. Therefore, a phase cooperative half-bridge DSC system as a simplified low-complexity DSC scheme is further investigated, and the load step regulation boundary is derived. Analysis is verified in experiment and simulation, demonstrating zero-voltage-switching behavior, dynamic load step regulation, the impact of harmonics on magnetics losses for high coupling, and the impact of variable voltage ratio.

Marco Liserre

Papers

High Performances Voltage Control of Bidirectional-Asymmetrical DC/DC Converter in Smart Transformer for Limited Reverse Power Flow

A VSC-Based Isolated Matrix-Type AC/DC Converter Without Bidirectional Power Switches

Analysis and Design of a Multiport Resonant DC-Transformer for Solid-State Transformer Applications

A Hybrid Modulation Technique for Operating Medium-Voltage High-Power CHB Converters Under Grid Voltage Disturbances

Communicationless Phase Cooperative Control of Inductive Power Transfer Using Asymmetrical Modulations