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

2011 International Conference on Power Engineering, Energy and Electrical Drives

This paper is focused on the control of small wind turbines, rated less than 200 kW, in grid-interactive microgrids. The considered system is based on a back-to-back power conversion stage. The management of the active and reactive power exchange in the different operating conditions is the key point to allow a practical integration of wind turbine systems in the main electrical grid. This issue lies in a proper control system design achieving high performance in grid-connection as in stand-alone operation modes. A cascade control loops structure is proposed in the paper. Some simulation and experimental results validate the control algorithm.

Small wind turbines in grid-interactive microgrids

Smart Transformers enable a stronger control of distribution grids, due to their advanced active/reactive power control capability. Redispachting the power in radial and meshed grids, the Smart Transformers are able to keep the voltage within limits and solve grid assets congestions. This paper offers the modelling of Smart Transformers for optimal power flow algorithms, in both radial and meshed grids. The Smart Transformer is compared with already implemented power electronics-based solutions, such as STATCOM or Soft Open Points, and its performance are validated in a large South-Italian distribution grid.

Modelling and Performance Evaluation of Smart Transformer in Distribution Grids

Higher magnitudes of the stator currents, low efficiency, and degradation of the output torque in high speed machine are caused by iron losses, which are not sufficiently small to be neglected. A Finite Control Set Model Predictive Control (FCS-MPC) which takes iron losses into account in the prediction model on a high speed motor is proposed in this paper and compared to classical FCS-MPC that neglects iron losses influence. Performances of both models are analysed and compared under steady-state and transient conditions including acceleration condition using a 3-Level Hybrid Active Neutral Point Clamped (HANPC) inverter topology. Accurate simulations of a 3-Level HANPC inverter driving a high speed PMSM are presented comparing the proposed control respect to classical FCS-MPC and the classical Field Oriented Control (FOC) together with neutral point (NP) balance and loss minimization control (LMC).

Iron Losses Impact on High-Speed Drives

The Modular Multilevel Converter represents a really promising solution for several high-power applications. Nevertheless, to furtherly enhance the penetration of such conversion structure and to fully exploit its advantages, some issues related to its operation need to be addressed. In particular, this converter features some circulating currents that deeply affect both the conduction losses occurring in the semiconductor devices and the voltage ripple across the capacitors of this conversion structure, which in turn influences the converter efficiency. In order to minimize the converter losses, this work proposes innovative control strategies of the circulating currents by calculating the optimal value of their reference. Alongside the increase of the converter efficiency, the proposed control strategies allow additional advantages in terms of enhancing the converter reliability and extending the overall system lifetime.

Marco Liserre

Papers

2011 International Conference on Power Engineering, Energy and Electrical Drives

Small wind turbines in grid-interactive microgrids

Modelling and Performance Evaluation of Smart Transformer in Distribution Grids

Iron Losses Impact on High-Speed Drives

Control Strategies for Losses Optimization in Modular Multilevel Converter