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

In this paper, an original multi-phase Surface Mounted Permanent Magnet (SMPM) Machine designed for naval propulsion is proposed. The design objective of this high power low speed machine is twofold: to enhance the fault tolerance capability of the system and to optimize the quality of the torque by reducing the electromagnetic torque ripples which underlie the acoustic behaviour of the motor and of the global mechanical structure. A low level of ripple torques must also be ensured in faulty operations. To fullfill these constraints, the machine is equipped with a fractional-slot concentrated winding made up of four 3-phase windings each one being star-connected, each star being magnetically shifted by an angle of 15 degrees. This 4-star 3-phase configuration allows to reduce the cogging torque and to separate magnetically and physically the phase windings. The end-turns are also drastically reduced, which improves the compactness and the efficiency of the machine. This original multi-phase machine is supplied by four 3-phase PWM voltage source inverter with sinusoidal current law. The magnetic independences between the four star windings allow a very simple control of the four-star supply and a straightforward fault operating mode. Moreover, this 4-star winding configuration yields to very low torque ripples in nominal configuration (four stars connected) and in faulty operations if two magnetic non adjacent stars are disconnected. For all these reasons, this structure appears particularly suitable for naval propulsion application since it increases the machine performances in terms of compactness, reliability and quality of torque.

/pdf/multi-star-multi-phase-winding-for-a-high-power-naval-59rvh08x4j.pdf

Multi-star multi-phase winding for a high power naval propulsion machine with low ripple torques and high fault tolerant ability

Five-phase surface-mounted permanent-magnet machines can inherently produce a smooth electromagnetic torque which can be increased when using third harmonic current injection. To really take advantage of these characteristics, the rotor magnets can be shaped to obtain a back electromotive force with large third harmonic term. This is the scope of this paper. For the design specifications of a low-speed marine propulsion machine, the following objective must be achieved: to significantly mitigate the pulsating torque without reducing the average torque bearing in mind the solution where the rotor is made with full pole-pitch magnets. An analytical field computation, called equivalent coil method, is developed to quickly explore the magnet geometries. Thus a procedure to optimize small trapezoid notches at the surface of the pole magnets is performed. Referring to the classical fully pole-pitch magnet shape, the solution found allows a substantial reduction of the pulsating torque without reducing the torque density. Furthermore, with regard to an equivalent three-phase machine, for the same copper losses, the average torque of the optimized five-phase machine can be potentially higher if the third harmonic current injection is implemented.

/pdf/magnet-shape-optimization-to-reduce-pulsating-torque-for-a-380mnq12ni.pdf

Magnet Shape Optimization to Reduce Pulsating Torque for a Five-Phase Permanent-Magnet Low-Speed Machine

A design methodology dedicated to multi-phase permanent magnet synchronous machines (PMSMs) supplied by pulse width modulation voltage source inverters (PWM VSIs) is presented. First, opportunities for increasing torque density using the harmonics are considered. The specific constraints caused by the PWM supply of multi-phase machines are also taken into account during the design phase. All the defined constraints are expressed in a simple manner by using a multi-machine modelling of the multi-phase machines. This multi-machine design is then applied to meet the specifications of a marine propeller: verifying simultaneously four design constraints, an initial 60-pole three-phase machine is converted into a 58-pole five-phase machine without changing the geometry and the active volume (iron, copper and magnet). First, a specific fractional-slot winding, which yields to good characteristics for PWM supply and winding factors, is chosen. Then, using this winding, the magnet layer is designed to improve the flux focussing. According to analytical and numerical calculations, the five-phase machine provides a higher torque (about 15%) and less pulsating torque (71% lower) than the initial three-phase machine with the same copper losses.

/pdf/multi-criteria-based-design-approach-of-multi-phase-2onrfpopcu.pdf

Multi-criteria-based design approach of multi-phase permanent magnet low-speed synchronous machines

This paper deals with the rough design of a Double-Stator Axial Flux Permanent Magnet Machine (DSAFPM) for a rim-driven Marine Current Turbine (MCT). The DSAFPM machine will be compared to a previously developed and realized Radial Flux Permanent Magnet Machine (RFPM); given the same rim-driven MCT specifications. For that purpose, a first-order electromagnetic design model and a thermal one are developed and used to compare active part mass, cost, and thermal behavior of the two machines. The obtained results show that such a structure of poly-air gap axial flux machine can be more interesting in terms of compactness and thermal behavior for rim-driven marine current turbines.

/pdf/rough-design-of-a-double-stator-axial-flux-permanent-magnet-4b1r558m6x.pdf

Rough design of a Double-Stator Axial Flux Permanent Magnet generator for a rim-driven Marine Current Turbine

This paper deals with the control strategies for a fixed-pitch marine current turbine (MCT) when the marine current speed exceeds the rated value corresponding to the rated power of generator and converter. Over-rated marine currents occur at large spring tides or under strong sea states; in these cases maximum power point tracking (MPPT) strategies must be changed to power limitation strategies for limiting the generator power at rated value. In this paper, two power limitation strategies with flux-weakening control are investigated. A feedback flux-weakening control is applied to extend the rotor speed operating range over the nominal MPPT tracking speed during high speed marine currents. In the speed control strategy, the turbine power characteristics are used to generate the rotor speed reference and the power limitation can be obtained at steady-state. In the torque control strategy, the generator torque is directly calculated by the power limitation and the rotor speed; this method enables to control the generator power at the limited value at dynamic process. Both strategies are investigated and compared at high tidal speeds without and with swell effect.

/pdf/power-limitation-control-for-a-pmsg-based-marine-current-rsl8oacg5o.pdf

Franck Scuiller

Papers

Multi-star multi-phase winding for a high power naval propulsion machine with low ripple torques and high fault tolerant ability

Magnet Shape Optimization to Reduce Pulsating Torque for a Five-Phase Permanent-Magnet Low-Speed Machine

Multi-criteria-based design approach of multi-phase permanent magnet low-speed synchronous machines

Rough design of a Double-Stator Axial Flux Permanent Magnet generator for a rim-driven Marine Current Turbine

Power limitation control for a PMSG-based marine current turbine at high tidal speed and strong sea state