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

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

Three-phase four-wire DC/AC converters are crucial for applications like electric vehicle (EV) chargers and solid-state transformers (SST). For ensuring galvanic isolation, dual-active-bridge (DAB) converters are often selected to be associated with the front-end AC/DC stage. In this context, this paper explores the possibility of delivering and driving the additional neutral wire directly from the DAB converter without introducing any additional and dedicated fourth-leg, as well as an independent-controlled neutral module. Further, a modified single phase-shift strategy capable of providing common-mode injection is presented and discussed under different operating conditions and modulation schemes. Finally, numerical results are presented to validate the correctness of all developments.

DAB-Based Common-Mode Injection in Three-Phase Four-Wire Inverters

As the amount of decentralized electric power generation is steadily growing, not only the direction of power flow, but also the overall behavior of the grid changes. This means that harmonic voltages in the supply grid become more problematic. To deal with this problem, inverters of decentralized renewable energy resources can help to mitigate these harmonic grid voltages by injecting harmonic currents. However, this so-called active filter functionality leads to additional stress of the dc-link capacitor due to inevitable oscillations of the dc-link current and voltage. Hence, this article for the first time presents an analytical derivation of these dc-link oscillations caused by a harmonic current injection into the grid. The analysis is presented for two-level and three-level inverters with split dc-link in a four-wire configuration. Simulation and experimental measurement results show the validity of the proposed analytical calculations. Furthermore, the impact of these dc-link harmonics on the capacitor lifetime is discussed. An exemplary scenario with a 10-KW photovoltaic inverter mitigating a 5th-harmonic grid voltage shows a possible lifetime reduction of the dc-link capacitor of up to 52% due to the oscillations in the dc-link voltage and current. Thus, this article aims to raise awareness of converter designers regarding this lifetime reduction, so that they take these oscillations into account during the design process and avoid unexpected early failure of the dc-link capacitor.

DC-Link Voltage Dynamics of Three-Level Four-Wire Grid-Connected Converters During Harmonics Injection Operations

AC-DC conversion is required in many applications, and in some of them isolation is strictly required, certainly while maintaining characteristics such as a high power factor and low input current THD. In this paper, an AC-DC converter, comprising a full-bridge diode rectifier and a dual-active-bridge (DAB) converter, is utilized to fulfill these characteristics. The used modulation makes the converter behave as a resistive load, maintaining the output voltage constant while achieving a high power factor and low input current THD. The operation of the converter is simple, as only two voltage sensors are required, and no inner current loop is utilized. A low-power prototype was experimentally tested to corroborate the proposal.

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AC-DC DAB Converter with Power Factor Correction

Kalman filtering is commonly used for state-of-charge (SOC) estimation for lithium-ion (Li-ion) batteries owing to its simplicity, computational efficiency, and relatively precise results. However, kalman filters depend on the Li-ion battery model. Several laboratory tests such as incremental current and dynamic stress tests are required to determine battery model parameters in model-based SOC estimation. These tests such as incremental current test and dynamic stress test are time-consuming and can take multiple days. A mathematical optimization along with a battery test method, which does not need rest time for battery, are adopted to reduce the battery parameter identification time, drastically. A mathematical optimization stage is embedded prior to Kalman Filter based SOC estimation computing the battery open circuit voltage (OCV) and as well as an initial guess of the RC parameters of the battery equivalent circuit. Therefore, it reduces the required number of tests to one. Extensive numerical studies on a 2 Ah Lithium-ion cell verify the effectiveness of the proposed method by achieving a RMS error less than one percent.

Autonomous Characterization of Lithium-Ion Battery Model Parameters utilizing a Mathematical Optimization Methodology

The energy systems are evolving toward the comprehensive and massive integration of power electronics-based technologies, such as photovoltaic, wind turbines, and electric vehicles. All these emerging and promising power converters technologies must be tested to comply with the grid codes, especially during severe grid fault events, before their commer-cialization. Low-Voltage Ride-Through (LVRT) field tests are usually conducted to prove the ability of the converter to ride through faults. Those field tests are expensive and require bulky equipment, while Power-Hardware-in-the-Loop (P-HIL) offers a more cost-effective and flexible alternative. However, the P-HIL must be stable and accurate to get reliable results. The accuracy of a P-HIL test is directly influenced by its interface algorithm. This paper proposes a frequency domain approach based on the concept of singular values in Multi-Input Multi-Output systems to study the P-HIL accuracy in grid connected converter testing under symmetrical and line-to-line asymmetrical fault conditions. The accuracy analysis has been performed analytically and validated by Matlab/Simulink simulations and by experimental P-HIL testing.

Marco Liserre

Papers

DAB-Based Common-Mode Injection in Three-Phase Four-Wire Inverters

DC-Link Voltage Dynamics of Three-Level Four-Wire Grid-Connected Converters During Harmonics Injection Operations

AC-DC DAB Converter with Power Factor Correction

Autonomous Characterization of Lithium-Ion Battery Model Parameters utilizing a Mathematical Optimization Methodology

Modeling of Symmetrical and Asymmetrical Grid Faults for P-HIL Accuracy Analysis in LVRT Tests