基于PSO的级联马赫-曾德尔型光滤波器优化设计

首次应用连续和离散版本的粒子群优化算法(PSO),实现级联马赫-曾德尔干涉仪(MZI)型光滤波器中关键结构参数(耦合角和相移因子)对理想系数的逼近,完成光滤波器的优化设计.结果表明:三级级联MZI型滤波器输出响应与理想响应之间的误差控制在10^-5量级内;同时与遗传算法(GA)设计方案相比,PSO方案具备计算时间少、逼近适应度好、滤波消光比高的特点.     

Numerical analysis of the effects of the magnetic self-field on the transport properties of a multilayer HTS cable

In this paper, the effects of the magnetic self-field on the transport properties of a multilayer high-T/sub c/ superconducting (HTS) cable are investigated by means of two-dimensional finite-element method (FEM) simulations. Analyzed is a three-layer HTS cable, but the developed methods can be used for a different number of layers. The superconductor is described by the nonlinear power-law relation E=E/sub c/(J/J/sub c/)/sup n/, where the parameters J/sub c/ and n depend on the magnetic field experienced by the material. This dependence decreases the global transport capacity of the superconductor, enhancing its AC losses. It is shown that, especially at high transport currents, the AC losses are considerably higher than in the case where the dependence on the magnetic field is neglected. A simple electrical model, considering the cable from macroscopic point of view, has been proposed for finding the optimal winding pitches, leading to a uniform current repartition. The use of this electrical model allows to overcome the difficulties of direct three-dimensional FEM computations. In addition, the rapidity of solutions by the electric model gives the possibility of testing quickly many geometrical configurations in order to find the ones leading to an even current repartition. This optimization process would not be possible with detailed FEM simulations.     

Analysis of AC Loss and Current Distribution Characteristics of Multi-Layer Triaxial HTS Cable for 3-Phase AC Power Transmission

This paper presented numerical studies on layer-to-layer current distributions and AC losses in triaxial multi-layer three-phase cable conductors. The simulations were performed for triaxial cables of 2-layer/phase configurations with several combinations of twist pitch to investigate the influence of the cable twist configuration on the layer-to-layer current distribution and the AC loss under 3-phase AC operation. From the numerical results, it was shown that the twist pitch combinations for uniform layer-to-layer current distributions could be found. The numerical results also showed, however, that the AC loss can not be reduced by equalizing the layer-to-layer current distribution. The reason is clarified from the numerical data of the current density profiles across the superconducting layers. For the cable design, it is necessary to select proper twist configuration considering not only the equalization of current distribution but also the minimization of AC loss.     

High capacity cable's role in once and future grids

High temperature superconducting (HTS) cables cooled to 77 K are starting to be tested and could soon be carrying a lot more current through the same old underground city pipes. If superconducting transmission cables can be made to work compatibly with other emerging high-temperature superconducting technologies then it may be possible to layout grids in innovative ways and to position generators closer to customers without having to step voltage up and down. Conventional underground cables normally incorporate fluid, such that the use of liquid-nitrogen coolant in superconducting cables is not such a departure as it might at first seem. The main immediate challenge in developing superconducting cables is to acquire operational experience. Only by working with live-networks and with the users of network equipment will it be possible to evaluate compatibility with existing components, system reliability, maintenance and total system costs. Two basic types of superconducting cable designs are emerging. In one the HTS conductor is enclosed in a cryogenic environment, which in turn is covered by conventional room temperature dielectric. In the other, a cryogenic-dielectric design, two concentric HTS conductors are used transmit electricity. These designs are discussed as are superconducting tapes for 77 K operation, cooling and insulation, joints and terminations, and testing parameters     

SuperPower's YBCO Coated High-Temperature Superconducting (HTS) Wire and Magnet Applications

Recent developments in second-generation (2G) HTS wire and coil technology are presented highlighting the ability of 2G HTS wire to function under demanding operating conditions associated with many applications including linear motors for transportation. The challenges of use in various coil constructions and applications are discussed. The 2G wire architecture of a structural substrate, buffer stack, HTS layer, and stabilization enables the 2G wire to tolerate high stress levels while providing the high current density required for lightweight, compact magnets. The high winding current density that is available with SuperPower's thin (0.1 mm) 2G HTS wire has been utilized in several coil demonstrations, including one generating central fields in excess of 26.8 T. The ability of the wire to be tailored (stabilization, insulation, ac losses) to fit various operating parameters will also be discussed.      

Numerical Analysis of AC Loss Characteristics of Cable Conductor Assembled by HTS Tapes in Polygonal Arrangement

Numerical studies on AC loss characteristic of a assembled conductors of multiple HTS tapes with high aspect ratio simulating YBCO tape in polygonal arrangement were presented in this paper. We developed a numerical model to analyze the AC loss in the HTS tape in the polygonally assembled conductor based on our previously developed model. The relations between the geometrical configuration and the AC loss properties of the conductor were made clear by the numerical simulation. The numerical results give the important information for the design of the cable conductor assembled by the HTS tapes with high aspect ratio such as YBCO tapes.     

Inversion of ocean color observations using particle swarm optimization

Inversion of ocean color reflectance measurements can be cast as an optimization problem, where particular parameters of a forward model are optimized in order to make the forward-modeled spectral reflectance match the spectral reflectance of a given in situ sample. Here, a simulated ocean color dataset is used to test the capability of a recently introduced global optimization process, particle swarm optimization (PSO), in the retrieval of optical properties from ocean color. The performance of the PSO method was compared with the more common genetic algorithms (GA) in terms of model accuracy and computation time. The PSO method has been shown to outperform the GA in terms of model error. Of particular importance to ocean color remote sensing is the speed advantage that PSO affords over GA.     

Multiobjective Optimization for HTS Fault-Current Limiters Based on Normalized Simulated Annealing

This paper presents an improved simulated annealing (SA) algorithm for multiobjective optimization, which is a positive approach in the design of high-temperature superconducting (HTS) fault-current limiters (SFCLs).The main goal of this paper is to achieve an effective and feasible approach in the structural design of HTS FCLs by means of multiobjective decision-making techniques, based on normalized SA. The combination of electrical and thermal models of a purpose-designed resistive-type HTS FCL is defined as a component in PSCAD/EMTDC simulations from which the proposed method will be used to optimize the selective parameters of the SFCL. The above requires the need of advanced numerical techniques for simulation studies by PSCAD on a sample distribution system for determining a global optimum HTS FCL, by considering individual parameters and accounting for the constraints, which is the main motivation for initiating this paper.      

Analysis of magnetic field and circulating current for HTS transformer windings

In a high-temperature superconducting (HTS) transformer, the leakage magnetic field decreases the critical current and increases the ac loss in the tapes. Moreover, because of nearly zero resistance of HTS tapes, a slight unbalance of the branch inductances of the windings might result in heavy circulating current. So, the numerical analysis of the leakage magnetic field and circulating current is especially necessary for an HTS transformer design. In this paper, the influence of the winding configurations on the stray field and circulating current is studied. That is, the magnetic field distribution is analyzed by finite-element method and then, based on the inductance matrix obtained after a magnetic field analysis, the circulating current is calculated by circuit analysis. Some measures for improving the leakage field and circulating current distribution are also proposed to make HTS transformers more efficient.     

利用智能方法进行LTCC电路的建模与优化

建模分析和优化综合是目前叠层LTCC滤波器设计的关键.建模方法一直是LTCC电路计算机辅助设计技术的主要瓶颈.利用智能方法对叠层LTCC滤波器的建模与优化的现状进行分析和讨论,即人工神经网络(ANN)、基因算法(GA)、遗传神经网络、神经网络空间映射(NSM)和知识自动模型生成(KAMG)等几种主要方法.并对以后的研究方向和发展趋势作了预测性阐述.     

Design of very thin wide band absorbers using modified local best particle swarm optimization

A method of using particle swarm optimization (PSO) algorithm to design electromagnetic absorber is presented. To demonstrate effectiveness of the PSO algorithm three different design cases are optimized. To reduce the local minimum traps, a modified local search strategy is employed. Each design problem is optimized using genetic algorithm (GA) and four variants of PSO algorithms, namely global PSO (gbest), local PSO (lbest), comprehensive learning PSO (CLPSO), and modified local PSO (MLPSO). The results clearly show that the MLPSO is a robust, fast, and useful optimization tool for designing absorbers. A seven-layer absorber achieved by this method has reflection coefficient below 18.7 dB from VHF to 20 GHz.     

Potential of Particle Swarm Optimization and Genetic Algorithms for FIR Filter Design

This article studies the performance of two metaheuristics, particle swarm optimization (PSO) and genetic algorithms (GA), for FIR filter design. The two approaches aim to find a solution to a given objective function but employ different strategies and computational effort to do so. PSO is a more recent heuristic search method than GA; its dynamics exploit the collaborative behavior of biological populations. Some researchers advocate the superiority of PSO over GA and highlight its capacity to solve complex problems thanks to its ease of implementation. In this paper, different versions of PSOs and GAs including our specific GA scheme are compared for FIR filter design. PSO generally outperforms standard GAs in some performance criteria, but our adaptive genetic algorithm is shown to be better on all criteria except CPU runtime. The study also underlines the importance of introducing intelligence in metaheuristics to make them more efficient by embedding self-tuning strategies. Furthermore, it establishes the potential complementarity of the approaches when solving this optimization problem.     

Thermal and electrical stabilization of high-temperature superconductor powder-in-tube conductor

High-temperature superconductor (HTS) powder-in-tube conductors often require thermal and/or electrical stabilization to ensure their long-term integrity. An example of such a stabilization need is the safety bypass lead of an HTS current lead intended for application to superconducting magnetic energy, storage (SMES) devices. The bypass lead functions include current sharing during upset conditions and conductor element temperature control. This paper presents a bypass lead design for an HTS current lead in an 0.5 MW h SMES system. Included are predictions of thermal and electrical stabilization and current lead heat leaks. The results of a supporting development program are presented, as are details of a method to connect conductor element/bypass leads, an assembly procedure, a cleaning method, and thermal-stress tolerance measurements.     

基于混沌自适应变异粒子群优化的解相干算法

针对相干信源波达方向估计的需要,结合粒子群优化算法,论文提出了一种基于混沌自适应变异粒子群优化的广义极大似然算法(CAMPSOGML),算法对阵列的几何结构没有任何约束,分辨的信源数可大于阵元数,算法把混沌初始化和自适应变异策略引进粒子群算法中,有效地提高了收敛速度,克服了粒子群算法容易陷入局部最优值的缺点。计算机仿真表明:与基于实数遗传算法和粒子群算法的广义极大似然估计方法相比,CAMPSOGML算法在收敛速度和估计精度上都有优势,是一种新颖的有效的解相干算法。     

An intelligent method to design laser resonator with particle swarm optimization algorithm

In order to design a complex laser resonator with multi-parameters, the method of particle swarm optimization (PSO) algorithm is employed. The parameters influencing the resonator stability and mode size distribution are taken into consideration, and the stability criteria index and the mode size distribution are used as target values. The absolute values of the differences between practical and the target values are set as the fitness function for the PSO. By minimizing the fitness function, a laser resonator with the optimized cavity parameters can be found. The analyses for the design example demonstrate the feasibility and validity of the PSO method in the computer aided design of multi- parameters laser resonator. Applying PSO algorithm in the intelligent design of solid state laser resonators can realize the transition from manual trial-and-error to computer intelligent design of the laser resonators.     

Transport AC Losses in YBCO Coated Conductors

Modeling and design of superconducting power devices (e.g. fault current limiters), based on second generation HTS tapes, requires accurate evaluation and prediction of AC losses. Transport AC losses measurements have been performed on samples of YBCO coated conductors at 77 K, as a function of current. The results have been compared with the classical analytical model for self field AC losses calculation, taking into account the role of the magnetic substrate.     

DOA and Power Estimation Using Genetic Algorithm and Fuzzy Discrete Particle Swarm Optimization

Aiming to reduce the computational costs and converge to global optimum, a novel method is proposed to solve the optimization of a cost function in the estimation of direction of arrival (DOA). In this method, genetic algorithm (GA) and fuzzy discrete particle swarm optimization (FDPSO) are applied to optimize the direction of arrival and power parameters of the mode simultaneously. Firstly, the GA algorithm is applied to make the solution fall into the global searching. Secondly, the FDPSO method is utilized to narrow down the search field. In FDPSO, chaotic factor and crossover method are added to speed up the convergence. This approach has been demonstrated through some computational simulations. It is shown that the proposed algorithm can estimate both the DOA and the powers accurately. It is more efficient than some present methods, such as Newton-like algorithm, Akaike information critical (AIC), particle swarm optimization (PSO), and genetic algorithm with particle swarm optimization (GA-PSO).     

有线电视屏蔽传输电缆电容的LBEM分析

屏蔽传输电缆把电视信号送进千家万户,而电感、电容等特性参数对传输电缆上的信号质量评估起着重要作用。介绍用线性边界元计算多芯屏蔽传输电缆电容的基本原理,3个工程实例的计算结果表明:有线电视屏蔽传输电缆电容不仅与芯线排列有关,还与芯线截面形状有很大关系。     

移动通信铁塔直击雷电流分布的研究

为研究雷击移动通信基站铁塔的电流分布特性,提出了一种全新的电路方法,创建了一个描述铁塔及其接地网构成的网络系统的电路模型。分析了铁塔上的雷电流分布及铁塔的冲击阻抗特性。仿真表明:铁塔及天线电缆屏蔽层上的雷电流分布情况与铁塔结构及雷击位置有关,但几乎不受大地电阻率的影响;而且,任意位置的直击雷在接地网对称位置的接地体上产生几乎相同的入地电流;"铁塔—接地网"网络的整体电阻和电抗随雷击点距地面高度的增加会有略微增大,其中电抗的变化比电阻的略大。研究成果为雷电防护设计提供了重要参考。     

Improving the Characteristics of integrated EMI filters by embedded conductive Layers

Discrete electromagnetic interference (EMI) filters have been used for power electronics converters to attenuate switching noise and meet EMI standards for many years. Because of the unavoidable structural parasitic parameters of the discrete filter components, such as equivalent parallel capacitance (EPC) of inductors and equivalent series inductance (ESL) of capacitors, the effective frequency range of the discrete filter is normally limited. Aiming at improving high frequency performance and reducing size and profile, the integrated EMI filter structure has been proposed based on advanced integration and packaging technologies , . Some improvements have been made but further progress is limited by EPCs of the filter inductors, which is restricted by dimension, size and physical structure. In this paper, a new structural winding capacitance cancellation method for inductors is proposed. Other than trying to reduce EPCs, a conductive ground layer is embedded in the planar inductor windings and the structural capacitance between the inductor winding and this embedded layer is utilized to cancel the parasitic winding capacitance. In order to obtain the best cancellation effect, the structural winding capacitance model of the planar spiral winding structure is given and the equivalent circuit is derived. The design methodology of the layout and area of the embedded ground layer is presented. Applying this method, an improved integrated EMI filter is designed and constructed. The experimental results show that the embedded conductive layer can effectively cancel the parasitic winding capacitance, hence ideal inductor characteristics can be obtained. With the help of this embedded conductive layer, the improved EMI filter has much smaller volume and profile and much better characteristics over a wide frequency range, compared to the former integrated EMI filter and the discrete EMI filter.