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

/pdf/power-electronic-systems-for-the-grid-integration-of-4s5cxjhatl.pdf

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

Power Semiconductors undergo thermal stress during operation, which is caused by thermal cycling. This refers to heating up and cooling down of the junction temperature and leads to aging and finally failures. Active thermal control can reduce the thermal stress of power semiconductors by regulating the power losses. Most algorithms proposed so far are only applicable to hard switching power converters and implement a regulation of the switching frequency, which is not applicable for the isolated DC/DC converters. This work proposes to regulate the duty cycle of the DC/DC converter to control the semiconductor losses, aiming at influencing the consequent thermal stress. The proposed algorithm is analyzed analytically and a thermal controller is designed, which is capable of reducing thermal cycles during operation without prior knowledge about the mission profile. The capability and the limitations of the proposed algorithm are demonstrated with simulations and the effectiveness is validated on a laboratory prototype with junction temperature measurement.

/pdf/active-thermal-control-of-isolated-soft-switching-dc-dc-1bucwo03k2.pdf

Active thermal control of isolated soft switching DC/DC converters

In this paper two promising LCL based filter topologies are evaluated against the well-known LCL with a damping resistor. The filters are designed for high power applications where the frequency modulation index is relatively low. The first topology is the selective resonant LCL filter which aim is to minimize the damping losses by bypassing the resistor at the fundamental and switching frequencies while preserving high attenuation at higher frequencies. A new design procedure is proposed for the selective resonant LCL filter. The presence of multi-tuned traps in the second topology aims to decrease the total size of the filter reactive elements while meeting current harmonic standards. It is found that selective resonant LCL filter provide much lower damping losses compared to the LCL filter with simple resistor topology. Additionally, for the trap topology a minimum switching frequency is determined which ensure that reduction in size of the filter is possible. The theoretical analysis is demonstrated by frequency analysis and time domain simulations.

Comparative analysis of the selective resonant LCL and LCL plus trap filters

Integration of charging stations for electric vehicles (EVs) will result in severe stress on electric grid. The EVs connected to the grid can also act as a source of energy and this demands greater control as well as coordination for better utilization. Conventional power transformers (CPTs) utilized in the EV charging stations are not well equipped for meeting these challenges. Recently, smart transformer (ST) has been proposed as an alternative to CPT. The ST connects medium voltage (MV) grid to low voltage (LV) grid with two intermediate MV and LV dc links. This paper utilizes the availability of the dc links of the ST to integrate the EVs charging station to electric grid rather than connecting these through the CPTs to the grid. A comprehensive analysis of sizing of the power converters utilized in the considered system has been presented. A comparison of efficiency for the different configurations is carried out and the possible more efficient scenario is suggested. Infact, the ST based EV charging system is found to be more efficient in comparison to CPT based EV charging station. The performance of ST based EV charging station is verified through simulation studies.

Operation and control of smart transformer-based electric vehicles charging system

The thermal behavior of power electronics devices has being a crucial design consideration because it is closely related to the reliability and also the cost of the converter system. Unfortunately, the widely used thermal models based on lumps of thermal resistance and capacitance have their limits to correctly predict the device temperatures, especially when considering the thermal grease and heat sink attached to the power semiconductor devices. In this paper, the frequency-domain approach is applied to the modelling of thermal dynamics for power devices. The limits of the existing RC lump-based thermal networks are explained from a point of view of frequency domain. Based on the discovery, a more advanced thermal model developed in the frequency domain is proposed, which can be easily established by characterizing the slope variation from the bode diagram of the typically used Foster thermal network. The proposed model can be used to predict not only the internal temperature behaviours of devices but also the behaviours of heat flowing out of the devices. As a result, more correct estimation of device temperature can be achieved when considering the attached cooling conditions.

https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/macau_derivate_00000431/frequency domian thermal modelling _homepage.pdf

Frequency-domain thermal modelling of power semiconductor devices

A modular Solid-State- Transformer (SST), typically consisting of cascaded H-Bridge (CHB) cells and isolated dc-dc converters, is considered as one of the most promising candidates for grid integration of large-scale PV systems (from MW to GW). However, the power imbalance among different modules and phases limits the operation range of SST. In this paper, a new common-dc-bus SST architecture, which consists of boost dc-de converters, isolated dc-dc converters and cascaded H-bridge cells, is proposed to solve the power imbalance issue. Power losses in the conventional and proposed common-dc-bus SST architectures are compared. Considering the characteristics of the proposed architecture, Zero Voltage Switching (ZVS) and the reactive current ratio of the isolated dc-dc converters are studied in detail. Simulation results of a three-phase 7-level large-scale PV system verify the effectiveness and feasibility of the proposed architecture.

Marco Liserre

Papers

Active thermal control of isolated soft switching DC/DC converters

Comparative analysis of the selective resonant LCL and LCL plus trap filters

Operation and control of smart transformer-based electric vehicles charging system

Frequency-domain thermal modelling of power semiconductor devices

High-Efficiency Solid State Transformer Architecture for Large-scale PV Application