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

Although the concept of variable-speed drives, based on utilization of multiphase machines, dates back to the late 1960s, it was not until the mid- to late 1990s that multiphase drives became serious contenders for various applications. These include electric ship propulsion, locomotive traction, electric and hybrid electric vehicles, ldquomore-electricrdquo aircraft, and high-power industrial applications. As a consequence, there has been a substantial increase in the interest for such drive systems worldwide, resulting in a huge volume of work published during the last ten years. An attempt is made in this paper to provide a brief review of the current state of the art in the area. After addressing the reasons for potential use of multiphase rather than three-phase drives and the available approaches to multiphase machine designs, various control schemes are surveyed. This is followed by a discussion of the multiphase voltage source inverter control. Various possibilities for the use of additional degrees of freedom that exist in multiphase machines are further elaborated. Finally, multiphase machine applications in electric energy generation are addressed.

Multiphase Electric Machines for Variable-Speed Applications

Large-scale deployment of intermittent renewable energy (namely wind energy and solar PV) may entail new challenges in power systems and more volatility in power prices in liberalized electricity markets. Energy storage can diminish this imbalance, relieving the grid congestion, and promoting distributed generation. The economic implications of grid-scale electrical energy storage technologies are however obscure for the experts, power grid operators, regulators, and power producers. A meticulous techno-economic or cost-benefit analysis of electricity storage systems requires consistent, updated cost data and a holistic cost analysis framework. To this end, this study critically examines the existing literature in the analysis of life cycle costs of utility-scale electricity storage systems, providing an updated database for the cost elements (capital costs, operational and maintenance costs, and replacement costs). Moreover, life cycle costs and levelized cost of electricity delivered by electrical energy storage is analyzed, employing Monte Carlo method to consider uncertainties. The examined energy storage technologies include pumped hydropower storage, compressed air energy storage (CAES), flywheel, electrochemical batteries (e.g. lead–acid, NaS, Li-ion, and Ni–Cd), flow batteries (e.g. vanadium-redox), superconducting magnetic energy storage, supercapacitors, and hydrogen energy storage (power to gas technologies). The results illustrate the economy of different storage systems for three main applications: bulk energy storage, T&D support services, and frequency regulation.

Electrical energy storage systems: A comparative life cycle cost analysis

Energy storage technologies and real life applications – A state of the art review

The electric vehicle (EV) technology addresses the issue of the reduction of carbon and greenhouse gas emissions. The concept of EVs focuses on the utilization of alternative energy resources. However, EV systems currently face challenges in energy storage systems (ESSs) with regard to their safety, size, cost, and overall management issues. In addition, hybridization of ESSs with advanced power electronic technologies has a significant influence on optimal power utilization to lead advanced EV technologies. This paper comprehensively reviews technologies of ESSs, its classifications, characteristics, constructions, electricity conversion, and evaluation processes with advantages and disadvantages for EV applications. Moreover, this paper discusses various classifications of ESS according to their energy formations, composition materials, and techniques on average power delivery over its capacity and overall efficiencies exhibited within their life expectancies. The rigorous review indicates that existing technologies for ESS can be used for EVs, but the optimum use of ESSs for efficient EV energy storage applications has not yet been achieved. This review highlights many factors, challenges, and problems for sustainable development of ESS technologies in next-generation EV applications. Thus, this review will widen the effort toward the development of economic and efficient ESSs with a longer lifetime for future EV uses.

Review of energy storage systems for electric vehicle applications: Issues and challenges

Five-phase Surface-mounted Permanent Magnet (SPM) machine offers the possibility of using the third harmonic of current to improve the average torque. In this paper, the use of third harmonic to compensate the pulsating torque and thus to reduce the vibrations transmitted to the shaft is explored. According to the multimachine theory, the torque of a five-phase star-connected SPM machine is distributed among two virtual machines: the Main Machine (MM) that corresponds to the fundamental of the current and the virtual Secondary Machine (SM) that corresponds to the third harmonic of the current. With this approach, it is shown that the first harmonic of the electromagnetic torque can be almost eliminated for a particular level of third harmonic current injection: this ratio depends on the back-emf spectrum and the resulting control makes the SM operating as generator to absorb the vibrations due to the MM operating as motor. This method is evaluated for the design specifications of a marine propeller where very low ripples at low speed are required. According to Finite Elements analysis, the expected significant reduction of the torque ripple factor is confirmed: more than two times with reference to the sinus control of the MM for the same average torque. The time simulations of the drive show the positive effect of this damping control strategy.

Third harmonic current injection to reduce the pulsating torque of a five-phase SPM machine

In this paper, the study of torque/speed characteristic for five-phase Surface-mounted Permanent Magnet (SPM) machine is carried out. With considering several hypothesis (linear magnetic modelling, only first and third harmonic terms in the back-emf and current spectrums), an optimization problem that aims to maximize the torque for given maximum voltage and RMS current is formulated: the optimal torque sharing among the two virtual machines (the two dq-axis subspaces) that represent the real five-phase machine is thus calculated for any mechanical speed. For an inverter and a DC voltage sized with only considering the first harmonic of back-emf and current, the problem is solved with changing the ratio between the two virtual machine back-emfs and changing the ratio between the two virtual machine inductances. The results are examined by introducing particular speed points.

/pdf/inductances-and-back-emf-harmonics-influence-on-the-torque-2oghm52t91.pdf

Inductances and Back-emf Harmonics Influence on the Torque/Speed Characteristic of Five-Phase SPM Machine

The paper studies the impact of first and third current-harmonic repartition in a five-phase Permanent Magnet machine whose Electromotive Forces (emfs) have first and third harmonics of the same amplitude. With a five-phase machine, it is possible for the torque production to achieve independent controls of the first and third harmonics of currents by using a vector control in each one of the two characteristic orthogonal sub-spaces of the machine. The same torque quality as obtained with a three-phase machine with sinusoidal emf can be thus obtained with a non-sinusoidal emf and with one more supplementary degree of freedom for the control. Based on the Maximum Torque Per Ampere (MTPA) strategy used for three-phase machines, a comparison of the obtained torque/speed characteristics of the machine is achieved using either one or two harmonics. The voltage limits imposed by the Voltage Source Inverter and two different values of the maximum allowed current densities are taken into account for obtaining the optimum repartition between first and third harmonics of currents: it appears that at first, from the point of view of efficiency, the MTPA is not optimal except for low speeds and secondly that the repartition of currents is not trivial and depends for example on the considered maximum current densities.

/pdf/maximum-torque-per-ampere-strategy-for-a-biharmonic-five-1vy5krssz4.pdf

Maximum Torque Per Ampere strategy for a biharmonic five-phase synchronous machine

Cette etude propose une methode de modelisation et de conception adaptee aux machines a flux axial et a Double Stator (poly-entrefer) destinee a etre integree comme generatrice pour une hydrolienne RIM-DRIVEN de grande puissance. La particularite du concept RIM-DRIVEN ou a entrainement circonferentiel reside dans le fait que la machine electrique se situe sur la peripherie de l'helice. De plus, dans cette etude, l'entrefer de la machine est considere immerge dans l'eau de mer. Les particularites du systeme imposent de mettre au point des modeles de dimensionnement adaptes. Ainsi, un modele electromagnetique analytique 2D inverse permettant le calcul des dimensions geometriques principales est presente. De meme, un modele thermique specifique aux machines a entrefer immerge est decrit. Ces modeles permettent d'estimer la masse et le cout des parties actives. Cette machine a flux axial est comparee en termes de couts matieres, masses et comportement thermique avec une machine a flux radial a aimants permanents dimensionnee pour un meme cahier des charges. Il en ressort clairement que la machine a flux axial double stator est thermiquement moins contrainte que les machines a simple stator.

/pdf/generatrice-a-aimants-permanents-a-flux-axial-a-grand-3ig3dfzzdd.pdf

Génératrice à aimants permanents à flux axial à grand diamètre avec entrefer immergé : Eléments de conception et analyse des performances pour un cahier des charges d'hydrolienne

In this paper, the possibility of designing a five-phase Surface-mounted Permanent Magnet (SPM) machine with 20 slots and 8 poles for a low power marine propulsion system is examined. Due to its particular winding and surface magnet design, the machine inherently offers an electronic pole changing effect from 3×4 pole pairs at low speed to 4 pole pairs at high speed. At high speed, in the constant power range, according to Finite Element Analysis, the Maximum Torque Per Ampere strategy appears not to be the right solution to minimize the whole machine losses (copper, iron and magnets). In particular, a strategy that favors the 4-pole rotating field at high speed allows to mitigate the magnet losses, thus limiting the risk of magnet overheating.

/pdf/five-phase-spm-machine-with-electronic-pole-changing-effect-1sbl89ehim.pdf

Franck Scuiller

Papers

Third harmonic current injection to reduce the pulsating torque of a five-phase SPM machine

Inductances and Back-emf Harmonics Influence on the Torque/Speed Characteristic of Five-Phase SPM Machine

Maximum Torque Per Ampere strategy for a biharmonic five-phase synchronous machine

Génératrice à aimants permanents à flux axial à grand diamètre avec entrefer immergé : Eléments de conception et analyse des performances pour un cahier des charges d'hydrolienne

Five-phase SPM machine with electronic pole changing effect for marine propulsion