다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The many different techniques for maximum power point tracking of photovoltaic (PV) arrays are discussed. The techniques are taken from the literature dating back to the earliest methods. It is shown that at least 19 distinct methods have been introduced in the literature, with many variations on implementation. This paper should serve as a convenient reference for future work in PV power generation.

/pdf/comparison-of-photovoltaic-array-maximum-power-point-2nci76j6n4.pdf

Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Review of the maximum power point tracking algorithms for stand-alone photovoltaic systems

This paper proposes a hybrid ac/dc micro grid to reduce the processes of multiple dc-ac-dc or ac-dc-ac conversions in an individual ac or dc grid. The hybrid grid consists of both ac and dc networks connected together by multi-bidirectional converters. AC sources and loads are connected to the ac network whereas dc sources and loads are tied to the dc network. Energy storage systems can be connected to dc or ac links. The proposed hybrid grid can operate in a grid-tied or autonomous mode. The coordination control algorithms are proposed for smooth power transfer between ac and dc links and for stable system operation under various generation and load conditions. Uncertainty and intermittent characteristics of wind speed, solar irradiation level, ambient temperature, and load are also considered in system control and operation. A small hybrid grid has been modeled and simulated using the Simulink in the MATLAB. The simulation results show that the system can maintain stable operation under the proposed coordination control schemes when the grid is switched from one operating condition to another.

A Hybrid AC/DC Microgrid and Its Coordination Control

The basic interphase power controller (IPC) presents the interesting features of simplicity and low cost but is less flexible than most flexible ac transmission system controllers. A compromise performance can be achieved by replacing the phase shifting transformers with a reduced rating dual unified power flow controller (UPFC) resulting in a unified IPC. The comparison of the basic, phase shifter-based, with a new UPFC-based, control logic is the main goal of this paper. The control variables of the dual UPFC are computed based on an optimization procedure to minimize a given cost function. The results show the higher capability of the proposed logic not only to control the current flow through the transmission line but also to achieve this task with lower branch currents that should lead to reduced power losses.

Comparison of Static Phase Shifter and Unified Power Flow Controller-Based Interphase

The basic interphase power controller (IPC) presents the interesting features of simplicity and low cost despite being less flexible than most FACTS controllers. A compromise performance can be achieved by replacing the phase shifting transformers (PSTs) with a reduced rating unified power flow control (UPFC), also known as Unified Interphase Power Controller (UIPC). This comparison is the main goal of this paper. The control variables of the UPFC are computed based on an optimization procedure to minimize a given cost function. The results show not only the higher capability of the UIPC to control the current flow through the transmission line but also shows that the UIPC achieves his task with less losses.

Comparison of phase shifting transformer and unified power flow control based interphase power controllers

Islanding is one important concern for grid connected distributed resources due to personnel and equipment safety. Preliminary design and performance assessment of inverter-resident frequency drifting islanding detection methods (IDMs) can be done by means of non-detection zones (NDZs) in a load parameter space. However, this tool only reflects the steady-state condition, that is, if the frequency of the islanded system will end up within a normal frequency range, where islanding occurs. It does not provide any information regarding the transient period, which is an important factor for the definition of the load testing points for the IEEE Std. 1547.1. Time domain simulations are used to identify critical load testing points that yield the longest run times. Then, the impact of these load values on the effectiveness of the design of frequency drifting IDMs using NDZ is discussed. As a result, an additional criterion for IEEE Std. 1547 compliance is presented.

Design and Compliance of Frequency Drifting Islanding Detection Methods with the IEEE Standard 1547.1

This paper aims to analyze the viability of a solar power system as a supplemental power source for commercial and business aircraft.,First, a model is established to estimate the potential available power from suitable aircraft surfaces for various meteorological conditions, ground and flight mission characteristics. A proposed aircraft system architecture and an associated parametric conceptual sizing model are presented. This supplemental solar power system sizing model is integrated into an aircraft multidisciplinary design optimization environment to evaluate the aircraft-level impact on mission fuel burn. A parametric study for a business jet aircraft is performed to analyze various solar cell types and power densities for converters. Trade-off studies are performed between efficiency and weight.,Considering today’s efficiency and power-to-weight ratio of the system components, overall fuel burn reduction can be achieved. Therefore, the technology development work can start now to target short to mid-term applications. In addition, promising system integration scenarios are identified, such as the use of solar power for autonomous operation of the air conditioning system on ground, which yield potential further benefit. In conclusion, a supplemental solar power system seems a promising candidate for more efficient aircraft operation.,The presented novel supplemental solar power system architecture concept and its foreseen aircraft integration show potential benefits for near term applications. The results show that the break even for this technology is already reached and therefore build the foundation to further investigate the technology integration challenges. Clear directions for future research and development are outlined enabling the advancement of the technology readiness level.

Proof-of-concept analysis of a supplemental solar power system for aircraft

DC grid interfaces for supercapacitors (SCs) are expected to operate with a wide range of input voltages with fast dynamics. The class-C DC-DC converter is commonly used in this application because of its simplicity. However, it does not work if the output voltage (V2) becomes smaller than the input voltage (V1). The non-isolated bi-directional Buck–Boost DC-DC converter does not have this limitation. Its two half-bridges provide a means for controlling the power flow operating in the conventional dual-state mode, as well as multi-state, tri, and quad modes. These can be used for mitigating issues such as the Right Half Plane (RHP) zero that has a negative impact on the dynamic response of the system. Multi-state operation typically requires multi-variable control, which is not easy to realize with conventional PI-type controllers. This paper proposes a unified controller for multi-state operation. It employs a carrier-based modulation scheme with three modulation signals that allows the converter to operate in all four possible states and eight different modes of operation. A mathematical model is developed for devising a multi-variable control scheme using feedback linearization. This allows the design of control loops with simple PI controllers that can be used for all multi-state modes under a wide range of operating conditions with the same performance. The proposed scheme is verified by means of simulations.

Luiz A. C. Lopes

Papers

Comparison of Static Phase Shifter and Unified Power Flow Controller-Based Interphase

Comparison of phase shifting transformer and unified power flow control based interphase power controllers

Design and Compliance of Frequency Drifting Islanding Detection Methods with the IEEE Standard 1547.1

Proof-of-concept analysis of a supplemental solar power system for aircraft

A Unified Controller for Multi-State Operation of the Bi-Directional Buck–Boost DC-DC Converter