This paper presents an enhanced control method for a doubly-fed induction generator (DFIG) basedwind-power generation system with series grid-side converter (SGSC) under unbalanced grid voltage conditions. The behaviors of the DFIG system with SGSC during network unbalance are described. By injecting a series control voltage generated from the SGSC to balance the stator voltage, the adverse effects of voltage unbalance upon the DFIG, such as stator and rotor current unbalances, electromagnetic torque and power pulsations can be removed, then the conventional vector control strategy for the rotor-side converter (RSC) remains in full force under unbalanced conditions. Meanwhile, three control targets for the parallel grid-side converter (PGSC) are identified, including eliminating the oscillations in total active power or reactive power, or eliminating negative-sequence current injected to the grid. Furthermore, a precise current reference generation strategy for the PGSC has been proposed for the PGSC to further improve the operation performance of the whole system. Finally, the proposed coordinated control strategy for the DFIG system with SGSC has been validated by the simulation results of a 2 MW DFIG-based wind turbine with SGSC and experimental results on a laboratory-scale experimental rig under small steady-state grid voltage unbalance. Index Terms-wind-power generation, doubly-fed induction generator (DFIG), grid voltage unbalance, series grid-side converter (SGSC), enhanced control NOMENCLATUREThis article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. 2 u s and u g Stator and grid voltage vectors u seires Series injected voltage vector of SGSC referred to stator-side i s, i r Stator and rotor current vectors i series SGSC current vector referred to stator-side i total Total current vector of the DFIG system P s and Q s Stator output active and reactive powers P r and Q r Rotor output active and reactive powers P g and Q g PGSC output active and reactive powers P series and Q series Active and reactive powers through SGSC P total and Q total Total output active and reactive powers of the DFIG system with SGSC T e Electromagnetic torque u dc Common dc-link voltage ω Synchronous angular speed θ g Grid voltage angle s Slip C Common dc-link capacitance Subscripts + andPositive-and negative-sequence components av Average component sin and cos Sine and cosine oscillating components abc Stationary abc-axis dq Synchronous dq-axis s and r Stator and rotor g and series PGSC and SGSC Superscripts + andPositive and negative synchronous reference frames * Reference value ^ Conjugate complex

When prior partial information about a state to be cloned is available, it can be cloned with a fidelity higher than that of universal quantum cloning. We experimentally verify this intriguing relationship between the cloning fidelity and the prior information by reporting the first experimental optimal quantum state-dependent cloning, using nuclear magnetic resonance techniques. Our experiments may further have important implications into many quantum information processing protocols.

This work demonstrates the use of a bottom-up templated growth technique to prepare a continuous, vertically aligned 2D MOF coating.

Two kinds of novel plasmonic high-sensitivity of refractive index(RI) sensors based on analyte-filled photonic crystal fiber (AF-PCF) are proposed in this paper. The metallic gold and silver is used as the surface plasmon resonance (SPR) activity metal. A full-vector finite element method (FEM) is applied to analyze and investigate the sensing and coupling characteristics of this designed AF-PCF with the gold or silver layer. Phase matching between 2nd surface plasmon polariton (SPP) and fundamental modes can be met at different wavelengths as the analyte of RI is increased from 1.40 to 1.42. The phase matching wavelength of the designed AF-PCF with the gold layer is shifted to the longer wavelength direction compared to that with the silver layer, and the resonance strength is much stronger. The average sensitivities of 7040 nm/RIU and 7017 nm/RIU in the sensing arrange from 1.40 to 1.42 with high linearity are achieved for the designed sensors with the gold and silver layers, respectively, which are almost the same. While the figure of merit (FOM) with silver layer is much better than that with the gold layer.Index Terms: Photonic crystal fiber, Surface plasmon resonance. Refractive index sensor 1943-0655 (c)

We investigate quantum games in which the information is asymmetrically distributed among the players and find that the possibility of the quantum game outperforming its classical counterpart depends strongly on not only the entanglement but also the informational asymmetry. What is more interesting, when the information distribution is asymmetric, is that the contradictive impact of the quantum entanglement on the profits is observed, which is not reported in quantum games of symmetric information.

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The entanglement between spins of a pair of particles may change because the spin and momentum become mixed when viewed by a moving observer [R.M. Gingrich and C. Adami, Phys. Rev. Lett. 89, 270402 (2002)]. In this paper, it is shown that, if the momenta are appropriately entangled, the entanglement between the spins of the Bell states can remain maximal when viewed by any moving observer. Further, we suggest a relativistic-invariant protocol for quantum communication, with which the non-relativistic quantum information theory could be invariantly applied to relativistic situations.

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