There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

This paper reviews the current status and implementation of battery chargers, charging power levels, and infrastructure for plug-in electric vehicles and hybrids. Charger systems are categorized into off-board and on-board types with unidirectional or bidirectional power flow. Unidirectional charging limits hardware requirements and simplifies interconnection issues. Bidirectional charging supports battery energy injection back to the grid. Typical on-board chargers restrict power because of weight, space, and cost constraints. They can be integrated with the electric drive to avoid these problems. The availability of charging infrastructure reduces on-board energy storage requirements and costs. On-board charger systems can be conductive or inductive. An off-board charger can be designed for high charging rates and is less constrained by size and weight. Level 1 (convenience), Level 2 (primary), and Level 3 (fast) power levels are discussed. Future aspects such as roadbed charging are presented. Various power level chargers and infrastructure configurations are presented, compared, and evaluated based on amount of power, charging time and location, cost, equipment, and other factors.

/pdf/review-of-battery-charger-topologies-charging-power-levels-85yy2igx2w.pdf

Review of Battery Charger Topologies, Charging Power Levels, and Infrastructure for Plug-In Electric and Hybrid Vehicles

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

Power electronics

This work is devoted to review and analyze the most relevant characteristics of multilevel converters, to motivate possible solutions, and to show that we are in a decisive instant in which energy companies have to bet on these converters as a good solution compared with classic two-level converters. This article presents a brief overview of the actual applications of multilevel converters and provides an introduction of the modeling techniques and the most common modulation strategies. It also addresses the operational and technological issues.

/pdf/the-age-of-multilevel-converters-arrives-izieu77jn6.pdf

The age of multilevel converters arrives

This paper proposes a novel topology for a three-phase hybrid passive filter (HPF) to compensate for reactive power and harmonics. The HPF consists of a series passive filter and a thyristor-controlled-reactor-based variable-impedance shunt passive filter (SPF). A mutual-inductance design concept is used to reduce the series passive filter inductance rating. The special features of the proposed HPF system are as follows: 1) insensitivity to source-impedance variations; 2) no series or parallel resonance problems; 3) fast dynamic response; and 4) significant size reduction in an SPF capacitor. The performance of the proposed HPF system is validated by simulation, as well as by experimentation, under different load conditions. Experimental and simulation results show that the proposed system can effectively compensate all voltage and current harmonics and reactive power for large nonlinear loads.

A Hybrid Passive Filter Configuration for VAR Control and Harmonic Compensation

The protection of the sensitive unbalanced nonlinear loads from sag/swell, distortion, and unbalance in supply voltage is achieved economically using the dynamic voltage restorer (DVR). A simple generalized algorithm based on basic synchronous-reference-frame theory has been developed for the generation of instantaneous reference compensating voltages for controlling a DVR. This novel algorithm makes use of the fundamental positive-sequence phase voltages extracted by sensing only two unbalanced and/or distorted line voltages. The algorithm is general enough to handle linear as well as nonlinear loads. The compensating voltages when injected in series with a distribution feeder by three single-phase H-bridge voltage-source converters with a constant switching frequency hysteresis band voltage controller tightly regulate the voltage at the load terminals against any power quality problems on the source side. A capacitor-supported DVR does not need any active power during steady-state operation because the injected voltage is in quadrature with the feeder current. The proposed control strategy is validated through extensive simulation and real-time experimental studies.

“SRF Theory Revisited” to Control Self-Supported Dynamic Voltage Restorer (DVR) for Unbalanced and Nonlinear Loads

In this paper, the authors propose a novel six-band hysteresis technique to efficiently control the seven-level packed U cells (PUC) converter. The proposed PUC combines advantages of the flying capacitor and the cascaded H-bridge topologies. The novel control strategy is proposed in order to insure a good operation of the PUC converter in both inverter and rectifier modes. In case of rectifier operation, the proposed six-band controller is designed to draw a sinusoidal line current (load current in case of inverter operation) with a unity power factor. Harmonics contents of line current (or load current) and rectifier input voltage (or inverter output voltage) are very low which permits the reduction of the active and passive filters ratings resulting on a very high energetic efficiency and a reduced installation cost. The proposed concept was validated through experimental implementation using real-time controller, the DS1103 of dSpace.

A Novel Six-Band Hysteresis Control for the Packed U Cells Seven-Level Converter: Experimental Validation

Three-pole/four-pole topologies of current-controlled voltage source inverters (CC-VSI) used as active filter (AF) are considered. The proposed AF system employs power balance theory, which is implemented using a TMS320C31 DSP. A four-pole topology for the AF system exhibits the facility of operating it as a three-pole device. A prototype model of the AF system has been designed and tested with a non-linear load to demonstrate its effectiveness for harmonic elimination, reactive power compensation and power-factor correction. After the control scheme was verified through extensive experimental investigations on a three-pole AF system, it was applied to demonstrate the performance of a four-pole AF system through simulation with different possibilities for the non-linear loads in field applications. Simulation and experimental results of the developed model of the AF system are given and discussed in detail.

Design, simulation and implementation of three-pole/four-pole topologies for active filters

This paper proposes a modified conation of single-phase pack U-cell (PUC) multilevel inverter in which the output voltage has higher amplitude than the maximum dc link value used in the topology as a boost operation. The introduced inverter generates seven-level ac voltage at the output using two dc links and six semiconductor switches. Comparing to cascaded H-bridge and neutral point clamp multilevel inverters, the introduced multilevel inverter produces more voltage levels using less components. The proposed inverter is used in photovoltaic (PV) system where the green power comes from two separate PV panels connected to the dc links through dc–dc converters to draw the maximum power. Due to boost operation of this inverter, two different PV panels can combine and send their powers to the grid. Simulations and experimental tests are conducted to investigate the good dynamic performance of the inverter in grid-connected PV system.

Kamal Al-Haddad

Papers

A Hybrid Passive Filter Configuration for VAR Control and Harmonic Compensation

“SRF Theory Revisited” to Control Self-Supported Dynamic Voltage Restorer (DVR) for Unbalanced and Nonlinear Loads

A Novel Six-Band Hysteresis Control for the Packed U Cells Seven-Level Converter: Experimental Validation

Design, simulation and implementation of three-pole/four-pole topologies for active filters

Modified Seven-Level Pack U-Cell Inverter for Photovoltaic Applications