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

Multi-Terminal HVDC transmission systems are vulnerable to DC faults. Hence, it is necessary to determine critical fault points in DC grids and develop reliable design criteria for protection equipment. Existing literature does not provide simple, computational efficient and accurate DC fault current calculation methods. The standard approach relies on simplified MMC models, which neglect the dynamics of power and DC voltage control loops. This results in inaccurate calculations of the node voltages and especially the DC currents in areas far away from the fault. To overcome these limitations, this article introduces first an improved MMC averaged model including the dynamics of power and DC voltage control. Second, this model is used in an improved fault current calculation method based on coupled differential equations. The analytical results of branch currents and node voltages in the overall DC grid are in good consistency with EMT-simulation results.

Improved Fault Current Calculation Method for Pole-to-Pole Faults in MMC Multi-Terminal HVDC Grids Considering Control Dynamics

Several maximum power point tracking (MPPT) methods have been proposed to optimize the energy harvesting of photovoltaic systems. However, the optimization of the energy harvesting can produce extremely variable loading of the power semiconductors resulting in a decrease of the system lifetime. This work proposes a multi-objective MPPT for two-stage photovoltaic converters, where the semiconductor thermal stress is taken into account while searching for the maximum power point. A perturb and observe based algorithm which limits the positive temperature gradient and the maximum junction temperature of the power semiconductors of the boost converter is introduced and fully validated in the laboratory with a mission profile emulating variable irradiance conditions. The achievable lifetime improvement is evaluated against the reduction in the energy harvesting.

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Thermal stress reduced maximum power point tracking for two stages photovoltaic converters

Fast charging stations support the electrification of transportation sector by reducing the charging time of electric vehicles. However, this process requires considerable power availability from the power system. In order to meet increasing load demand, the system operator is forced to oversize the distribution grid components. In order to maintain the system within its ampacity, the operator can adopt innovative strategies to handle peak demand. In this paper, a peak-shaving strategy for fast charging stations, based on the on-line load control, is proposed by means of reactive power injection. Controlling the reactive power injection from fast charging stations, the online load control is able to reduce the voltage amplitude in the distribution grid, therefore shave the active power consumption of voltage-dependent loads. The investigation the proposed control scheme has been implemented in a modified 20kV radial feeder. The analysis has showed the effectiveness in shaving the peak load.

Online Load Control in Medium Voltage Grid by Means of Reactive Power Modification of Fast Charging Station

Virtual Synchronous Machines (VSMs) have been proposed during the last decade as possible solutions for integrating the increasing amount of power electronics-based grid connected converters in the utility grid. One of their main characteristics is the ability to self-synchronize themselves to the main grid without the need of a dedicated unit, since they can reproduce the power synchronization mechanism of a synchronous machine (SM). Different control strategies have been proposed in the literature based on the aforementioned principle. The aim of this work is to provide a generalized formulation of a power synchronization based (PSB) control algorithm, outlining the different loops constituting the control and to give an overview of the solutions proposed in the literature. Similarities along with advantages and drawbacks of each formulation are highlighted in the paper and time-domain simulation in MATLAB/SimulinkIPLECS are performed to compare the performance of the different solutions.

A Generalized Formulation of Active Power Synchronization Based Control Algorithms for Grid Connected Converters

Modular converter structures are state of the art for fast charging, since high power and short charging times are required Multiwinding converter structures can bring several positive advantages, like cost and space reduction However, the increased complexity due to the magnetically coupled ports needs to be handled This paper introduces a multiwinding based Semidual-Active-Bridge converter with separated output voltages The related design challenges in terms of independent charging voltage regulation are evaluated and design guidelines for the medium frequency transformer are presented The theoretical analysis is validated experimentally

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Marco Liserre

Papers

Improved Fault Current Calculation Method for Pole-to-Pole Faults in MMC Multi-Terminal HVDC Grids Considering Control Dynamics

Thermal stress reduced maximum power point tracking for two stages photovoltaic converters

Online Load Control in Medium Voltage Grid by Means of Reactive Power Modification of Fast Charging Station

A Generalized Formulation of Active Power Synchronization Based Control Algorithms for Grid Connected Converters

Multiwinding based Semi-Dual Active Bridge Converter