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 use of Silicon Carbide (SiC) power semiconductors presents an attractive solution for increasing the efficiency and the power density of power converters. However, the capability to withstand a short circuit represents a challenge, because of higher current density and smaller chip size compared to Si-based power semiconductors with similar rating. Therefore, the time to detect and interrupt a short circuit is shorter and requires a fast detection and switch off of a short circuit current. In this work, short circuits detection methods for SiC MOSFETs are compared and a desaturation detection is developed and validated experimentally on a specially built SiC MOSFET module.

Short Circuit Detection Methods for Silicon Carbide (SiC) Power Semiconductors

Intermittent generation and load demand are one of the major challenges for grid operators. Caused for example by renewables power variability or electric vehicle charging, it can create mismatches between the real-time demand and the forecast demand, affecting frequency regulation. To alleviate this mismatch, operators have to resort either on the balancing market or on extensive use of energy storage systems, which increases operation costs. This article introduces a load-leveling approach exploiting the voltage dependence of the loads. With a controlled reactive power injection, the converters of fast charging stations can influence the voltage profile and, consequently, the power consumption of voltage-dependent loads. The approach has two main goals: minimizing the mismatches with respect to the demand forecast and reducing the grid losses. Fast charging stations are particularly suited for this approach. Being employed with full capacity for charging only for short time, their spare capacity can be exploited to apply the load-leveling approach. This proposed approach is discussed theoretically and analyzed in a modified distribution network in Northern Germany. Parameters variation analysis has been performed to thoroughly demonstrate the effectiveness of the approach under different load/grid conditions. Its feasibility has been evaluated by means of power-hardware-in-the-loop tests.

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Voltage-Dependent Load-Leveling Approach by Means of Electric Vehicle Fast Charging Stations

Wide bandgap semiconductors are promising regarding loss reduction and increase of switching frequency. In the specific case of two level power converter it has not been up to now clearly shown the potential of SiC and GaN in comparison with Si semiconductors. In this paper, a multi-variable analysis for different devices is carried out, considering system efficiency, heatsink size and output filter design. The results are condensed in a performance index, that allows comparing different solutions.

Evaluation of SiC and GaN technologies for a full-bridge grid-connected converter through a comprehensive performance index

Internal distribution systems such as photovoltaic parks allow to use DC or AC with a frequency different from 50Hz. In this paper is instead proposed to use more than one frequency at the same time. The grid voltage amplitude at the fundamental frequency can be increased while the voltage peak value is kept constant by adding odd harmonics to the voltage waveform. The currents are decreased for the same power level which leads to reduced power converter losses. A further current reduction is achieved if waveform peak shaping is applied to the current waveforms. This paper presents the impact of multi-frequency power transfer on single-phase converters, and verifies the results with analysis and simulations. The impact of harmonic frequencies on cable losses due to the skin effect is taken into consideration in the analysis and effects on protection are discussed.

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Waveform peak shaping by multi-frequency power transfer in internal, single-phase distribution systems

3-Level Voltage Source Inverters (3L-VSI) have emerged as effective approach to achieve high efficiency and better harmonic distortion performance. As a State-of-Art (SoA), two types of carrier arrangement methods are used for carrier-based pulse width modulation (PWM), namely, phase disposition (PD) and alternate phase opposite disposition (APOD). PD PWM gives better performance in terms of current quality and Total Harmonic Distortion (THD) whereas, APOD PWM is more effective for suppression of Common-Mode Voltage (CMV) with the expense of increased THD. In this paper, a novel Quasi-reference PWM method for 3L-VSIs is presented which results in low CMV as that of the APOD along with the reduced THD. The proposed method can be considered as a distinct trade-off between the two SoA methods, which maintains the merits of both. This paper presents the detail analysis and experimental verification of the proposed PWM technique.

Marco Liserre

Papers

Short Circuit Detection Methods for Silicon Carbide (SiC) Power Semiconductors

Voltage-Dependent Load-Leveling Approach by Means of Electric Vehicle Fast Charging Stations

Evaluation of SiC and GaN technologies for a full-bridge grid-connected converter through a comprehensive performance index

Waveform peak shaping by multi-frequency power transfer in internal, single-phase distribution systems

Quasi-Reference PWM for 3-level Voltage Source Inverters