-
[show abstract]
[hide abstract]
ABSTRACT: This study proposes a new multi-output LLC series resonant topology, which has asymmetrical structures for the main and the auxiliary outputs. The novel topology is devoted to use as multi-output power conversion system. The topology is a good candidate for multi-output applications with limited light loads. According to the output power level, different structures of the secondary outputs can be flexibly adapted. All the switches of this topology operate under the condition of zero voltage switch (ZVS) or zero current switch (ZCS). Therefore it is suitable to high frequency and high power density applications. The asymmetrical operation principle between the main output and the auxiliary outputs is analysed. ZVS and ZCS operations are explained in detail. Moreover the key parameter design considerations are presented. The theoretical analysis was verified both by simulation and experiment results. Finally, a prototype, with 310 V input, 48 V@1-2 A main output, and 24 V@0-0.5 A auxiliary output, was built and tested to validate the analysis done. The experimental results do match the theoretical analysis very well. The efficiency of the prototype under nominal input and full load reached 93%.
IET Power Electronics 12/2011; · 1.62 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This paper presents studies of the size effect on magnetic switching and interlayer magnetostatic coupling in synthetic antiferromagnet (SAF)-pinned spin-valve nanorings connected to nano stripes with a nanoconstriction. Micromagnetic simulation has been successfully used to reveal the detailed magnetization reversal process of these nanorings. It was observed that SAF-pinned spin-valve nanorings exhibit a double (onion-vortex-reverse onion) or single (onion-reverse onion) magnetization switching process depending on the ring diameter, which is contrary to narrow single-layer NiFe rings that show a double switching process only. Micromagnetic simulations of the SAF-pinned spin valve nanorings suggest that the magnetostatic coupling between the pinned layers of the SAF and the free layer is dependent on the ring size: it plays a very important role in the magnetization switching of small nanorings (600 nm outer diameter), but only a minor role in the switching of big nanorings (1600 nm outer diameter). An efficient reduction of the magnetostatic interaction results in a small shift of the minor magnetoresistance curve, which is beneficial to the magnetic memory applications.
IEEE Transactions on Magnetics 02/2011; · 1.36 Impact Factor
-
Z. Lu,
N. Collaert,
M. Aoulaiche,
B. De Wachter,
A. De Keersgieter,
W. Schwarzenbach,
O. Bonnin,
K.K. Bourdelle,
B.-Y. Nguyen,
C. Mazure,
L. Altimime,
M. Jurczak
[show abstract]
[hide abstract]
ABSTRACT: We demonstrate a novel low-voltage biasing scheme on ultra-thin BOX (UTBOX) FDSOI floating body cells with L<sub>g</sub>=55nm and t<sub>Si</sub>=20nm. By optimizing the front and back gate biasing to enhance the positive feedback loop, the required V<sub>DS</sub> can be reduced to 1.5V while retention times as high as 5s can still be achieved at 85°C. For the first time, we also show that the stringent endurance spec of 10<sup>16</sup> cycles can be met as a result of the V<sub>DS</sub> reduction.
Electron Devices Meeting (IEDM), 2010 IEEE International; 01/2011
-
[show abstract]
[hide abstract]
ABSTRACT: We report the first demonstration of a super-steep subthreshold slope (SS) (the smallest ever reported experimentally) with ultra-thin BOX (UTBOX) FDSOI standard CMOS transistors. Record steep SS of 72μV/dec for L<sub>g</sub>=25nm and 58μV/dec for L<sub>g</sub>=55nm at room temperature are achieved with low voltages. The device also exhibits high ON-state current (~100μA/μm), as compared to other devices from this class. As a result, I<sub>ON</sub>/I<sub>OFF</sub> ratio of 10<sup>8</sup> is realized with 0.5V gate swing for L<sub>g</sub>=55nm MOSFETs. The excellent reliability is also demonstrated.
Electron Devices Meeting (IEDM), 2010 IEEE International; 01/2011
-
[show abstract]
[hide abstract]
ABSTRACT: A dual-modulus prescaler based on a multi-phase quasi-differential locking divider is presented. It directly modulates the output in a multi-phase ring oscillator by quasi-differential injection. Dualmodulus operation is achieved by change of the number of injected signals. It is suitable for low supply operation while a wide locking range is obtained. Implemented in a standard 0.18 μm CMOS process, the 4/5 dual-modulus prescaler achieves an operating range of 1.1-5.6 GHz with 0.8 mW measured power consumption from a 1.2 V supply.
Electronics Letters 12/2010; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Ultra-wide bandwidth superluminescent diodes (SLDs) using multiple layers of InAs-GaAs quantum dots (QDs) with engineered height are realised. A tilted and tapered active region is used to reduce the effective reflectivity from the facets. A 3 dB emission bandwidth up to 140 nm centred at 1100 nm is achieved at a continuous-wave drive-current of 600 mA. It is shown that varying the height of the dots from one layer of dots to another within the active region considerably broadens the emission spectrum of the QD-SLDs compared to those made of similar layers of inhomogeneous QDs.
Electronics Letters 09/2010; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Moore's law steadily continues though facing a number of challenges. This paper identifies ongoing and desirable trends to exploit the technology capacity and further Moore's law for terascale on-chip computing architectures in the next ten years. Four foreseeable trends are: from single core to many cores, from bus-based to network-based interconnect, from centralized memory to distributed memory, and from 2D integration to 3D integration. We motivate these trends and show that the number of design choices for computing chips is increasing rapidly, leading to an exploding design space with uncountable opportunities for the innovative architect. Moreover, we envision that the multi-core Network-on-Chip will become an infrastructure backbone and accumulate many other infrastructural functions such as memory, power and resource management, testing and diagnostic services.
ASIC, 2009. ASICON '09. IEEE 8th International Conference on; 11/2009
-
[show abstract]
[hide abstract]
ABSTRACT: Co <sub>90</sub> Fe <sub>10</sub> films with an in-plane uniaxial magnetic anisotropy have been grown on an obliquely sputtered thin Ru underlayer. The anisotropy field can be increased up to 200 Oe. The hysteresis curves show a very high squareness in the easy axis direction and almost no hysteresis in the hard axis direction, suggesting that the induced uniaxial anisotropy is uniform throughout the films. The switching characteristics of the nanoelements fabricated from the films by e-beam lithography are also investigated. There is no degradation of the magnetic anisotropy after the annealing and lithographical process.
Journal of Applied Physics 11/2009; · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The magnetic properties of Si/Ru(t nm)/Fe<sub>90</sub>Co<sub>10</sub> (3.0 nm)/Ru (4.0 nm) films with obliquely sputtered Ru underlayers were studied as a function of Ru underlayer thickness (t). It was found that an obliquely sputtered Ru underlayer produces high uniaxial anisotropy in the Fe<sub>90</sub>Co<sub>10</sub> layer with extremely small hysteresis in the hard axis direction. The anisotropy field can be increased by increasing Ru underlayer thickness. X-ray reflectometry showed that the interfaces of the samples were quite smooth with rms roughness as small as 0.35 nm. The high uniaxial anisotropy of the samples shows high thermal stability and endures e-beam lithography for microscopic device fabrication. We discuss the origin of this high anisotropy in terms of a magnetostatic effect arising from an anisotropic surface morphology.
IEEE Transactions on Magnetics 11/2009; · 1.36 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This paper presents an adaptive distance relaying algorithm (ADRA) for transmission line protection. In ADRA, a fault detector designed based on mathematical morphology (MM) is used to determine the occurrence of a fault. The Euclidean norm of the detector output is then calculated for fault phase selection and fault type classification. With respect to a specific type of fault scenario, an instantaneous circuit model applicable to a transient fault process is constructed to determine the position of the fault. The distance between the fault position and the relay is calculated by a differential equation of the instantaneous circuit model which is resolved in a recursive manner within each sampling interval. Due to the feature of recursive calculation, the protection zone of the relay varies from a small length to large, which increases as an augment in the sample window length. ADRA is evaluated on a transmission model based on PSCAD/EMDTC, under a variety of different fault distances, fault types, fault resistances and loading angles, respectively. The simulation results show that in comparison with conventional DFT-based protection methods, by which the fault distance is calculated using phasor measurements of voltage and current signals in a fixed-length window, ADRA requires much fewer samples to achieve a same degree of the accuracy of fault distance calculation, which enables much faster tripping, and its protection zone can be extended as more samples are used.
Power & Energy Society General Meeting, 2009. PES '09. IEEE; 08/2009
-
[show abstract]
[hide abstract]
ABSTRACT: Anti-islanding protection of distributed generation (DG) is a significant technical barrier for the DG industry. This paper presents an innovative agent brokering-based anti-islanding scheme developed in response to the challenge. The scheme enables relay operational signals to be transferred to downstream DG units for coordinating their connection status using the multi-agent system (MAS) technology. A DG unit is considered as islanded from the upstream system if a trip signal is received at the DG unit. A number of software agents have been developed based on a generic structure for device control, data transfer and communication and the proposed scheme has been simulated using an established distribution system model integrated with four DG units. Two scenarios are designed to evaluate the performance of the scheme in handling multiple faults and change of system topology issues respectively. The simulation results are promising and the flexibility and scalability of the scheme are discussed.
Power & Energy Society General Meeting, 2009. PES '09. IEEE; 08/2009
-
[show abstract]
[hide abstract]
ABSTRACT: A near-infrared to visible light optical upconverter by the integration of an i-In<sub>0.53</sub>Ga<sub>0.47</sub>As/C<sub>60</sub> junction and an organic light emitting diode is reported. This device shows the photovoltaic effect of an i-In<sub>0.53</sub>Ga<sub>0.47</sub>As/C<sub>60</sub> heterojunction and potential application in a pixelless upconversion imaging device.
Electronics Letters 08/2009; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: It is a challenging problem to ensure the global goal of virtual organization together with maintaining the autonomous ability of individual agent in open, dynamic and heterogeneous network environment. Aiming at this problem, this paper proposes a model of agent social based on norms, policies, and contracts to form and operate VO. This model is divided into three layers: macro regulation layer, micro behavior layer, and joint layer. Firstly, in macro regulation layer, we design e-institution and its social behavior norms to regulate the cooperation behavior of autonomous agent. Secondly, in micro behavior layer, we design policy-driven agent which can accept the regulation from macro regulation layer. Finally, the joint layer joins the two layers to make the whole system operable. Thus, the cooperation behavior of autonomous agents can achieve the global goal of VO.
Computer Science and Information Engineering, 2009 WRI World Congress on; 05/2009
-
[show abstract]
[hide abstract]
ABSTRACT: This paper presents a novel morphological scheme for the identification of transformer magnetizing inrush. The scheme decomposes a current signal into multiresolution levels based on synthesis and analysis operators of mathematical morphology. It is able to discriminate between inrush and internal fault currents even in the case of an inrush with a low second harmonic component and an internal fault current with a high second harmonic component. Simulation studies have been undertaken to evaluate the scheme based on a three-phase high-voltage power transformer operating under different conditions, which is simulated with an alternative transients program. The testing results show that the proposed scheme is able to identify inrush currents reliably and provides an alternative solution for transformer differential protection.
IEEE Transactions on Power Delivery 05/2009; · 1.35 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Current transformer (CT) saturation can cause protective relay mal-operation or even prevent tripping. The wave shape of the secondary current is severely distorted as the CT is forced into deep saturation when the residual flux in the core adds to the flux change caused by faults. In this paper, a morphological lifting scheme is proposed to extract features contained in the waveform of the signal. The detection of the CT saturation is accurately achieved and the points of the inflection, where the saturation begins and ends, are found with the scheme used. This paper also presents a compensation algorithm, based upon the detection results, to reconstruct healthy secondary currents. The proposed morphological lifting scheme and compensation algorithm are demonstrated on a sample power system. The simulation results clearly indicate that they can successfully detect and compensate the distorted secondary current of a saturated CT with residual flux.
Circuits and Systems I: Regular Papers, IEEE Transactions on 12/2008; · 1.97 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, flexible AC transmission system (FACTS) devices are optimally allocated in a power network to achieve optimal power flow (OPF) solution. The location of FACTS devices and the setting of their control parameters are optimized by a bacterial swarming algorithm (BSA) to improve the performance of the power network. Two objective functions are simultaneously considered as the indexes of the system performance: maximization of system loadability in system security margin and minimization of total generation fuel cost. Four types of FACTS devices are modeled and incorporated in the OPF problem. Simulation studies are undertaken on a standard IEEE 30-bus test system. Results demonstrate that the steady state performance of the power system can be effectively enhanced due to the optimal allocation of multi-type FACTS devices.
Power and Energy Society General Meeting - Conversion and Delivery of Electrical Energy in the 21st Century, 2008 IEEE; 08/2008
-
[show abstract]
[hide abstract]
ABSTRACT: This paper presents a group search optimizer with multiple producer (GSOMP) for reactive power dispatch incorporating with flexible AC transmission system (FACTS) devices, which is formulated as a nonlinear constrained multi-objective optimization problem. The optimal location of multi-type FACTS devices and their control parameters are optimized by GSOMP to minimize the real power loss and also to improve voltage profile. The performance of GSOMP has been evaluated on the standard IEEE 14-bus and New England 39-bus test systems respectively. Simulation results show that the performance of the power systems is improved with multi-type FACTS devices optimally placed in the reactive power planning model.
Evolutionary Computation, 2008. CEC 2008. (IEEE World Congress on Computational Intelligence). IEEE Congress on; 07/2008
-
[show abstract]
[hide abstract]
ABSTRACT: This paper presents a dynamic bacterial swarming algorithm (DBSA) for harmonic estimation in dynamic environment. DBSA is designed from a dynamic searching framework that combines the underlying mechanisms of bacterial chemotaxis, quorum sensing and environment adaptation. The harmonic estimation process utilizes DBSA to estimate the phases of the harmonics, alongside a least square (LS) method to estimate the amplitudes. A cost function is given as an error between the original signal and the reconstructed signal.
Evolutionary Computation, 2008. CEC 2008. (IEEE World Congress on Computational Intelligence). IEEE Congress on; 07/2008
-
[show abstract]
[hide abstract]
ABSTRACT: We present a detailed study, on time scales from picoseconds to seconds, of transient and continuous wave (cw) photoconductivity in solution-grown thin films of functionalized pentacene (Pc), anthradithiophene (ADT), and dicyanomethylenedihydrofuran (DCDHF). In all films, at temperatures of 285–350 K, we observe fast carrier photogeneration and nonthermally activated charge transport on picosecond time scales. At ∼30 ps after photoexcitation at room temperature and at applied electric field of 1.2×10<sup>4</sup> V / cm , values obtained for the product of mobility and photogeneration efficiency, μη , in ADT-tri-isoproplysilylethynyl-(TIPS)-F, Pc-TIPS, and DCDHF films are ∼0.018–0.025 , ∼0.01–0.022 , and ∼0.002–0.004 cm <sup>2</sup>/ V s , respectively, depending on the film quality, and are weakly electric field dependent. In functionalized ADT and Pc films, the power-law decay dynamics of the transient photoconductivity is observed, on time scales of up to ∼1 μ s after photoexcitation, in the best samples. In contrast, in DCDHF amorphous glass, most of the photogenerated carriers are trapped within ∼200 ps . Transport of photoexcited carriers on longer time scales is probed by cw illumination through an optical chopper, with a variable chopper frequency. In contrast with what is observed on picosecond time scales, charge carriers on millisecond and longer time scales are predominantly localized, and are characterized by a broad distribution of carrier lifetimes. Such carriers make the principal contributions to dc photoconductivity.
Journal of Applied Physics 07/2008; · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: There are problems arising in fault type classification in double circuit transmission lines due to the mutual coupling between the two circuits under fault conditions. A novel fault phase selection scheme is proposed in this paper, which provides an approach to accurately classify the fault types by dealing with six-phase and a model currents using a morphological transformation. The fault characteristics can be effectively extracted from the associating currents by the morphological transformation. The fault phase selection scheme is tested on a simulation model under different fault types, location, resistance and inception angle. All the test results show that the proposed scheme is well suited for classifying fault types in double circuit transmission lines.
Electric Utility Deregulation and Restructuring and Power Technologies, 2008. DRPT 2008. Third International Conference on; 05/2008
