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Mostafa Dellahi Hattab Maker Guillermo Botella Enrique Alameda-Hernandez Azeddine Mouhsen 《International Journal of Circuit Theory and Applications》2020,48(6):887-905
The three-phase four-wire shunt active power filter (SAPF) was developed to suppress the harmonic currents generated by nonlinear loads, and for the compensation of unbalanced nonlinear load currents, reactive power, and the harmonic neutral current. In this work, we consider instantaneous reactive power theory (PQ theory) for reference current identification based on the following two algorithms: the classic low-pass filter (LPF) and the second-order generalized integrator (SOGI) filter. Furthermore, since an important process in SAPF control is the regulation of the DC bus voltage at the capacitor, a new controller based on the Lyapunov function is also proposed. A complete simulation of the resultant active filtering system confirms its validity, which uses the SOGI filter to extract the reference currents from the distorted line currents, compared with the traditional PQ theory based on LPF. In addition, the simulation performed also demonstrates the superiority of the proposed approach, for DC bus voltage control based on the Lyapunov function, compared with the traditional proportional-integral (PI) controller. Both novel approaches contribute towards an improvement in the overall performance of the system, which consists of a small rise and settling time, a very low or nonexistent overshoot, and the minimization of the total harmonic distortion (THD). 相似文献
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Maria Yousaf Lodhi Muhammad Azhar Khan Majid Niaz Akhtar Muhammad Farooq Warsi Asif Mahmood Shahid M. Ramay 《Ceramics International》2018,44(3):2968-2975
The influence of neodymium and nickel substitution on structural and dielectric parameters was investigated in strontium-barium X-type hexagonal ferrites having composition SrBaCu2?xNixNdyFe28?yO46 (x = 0, 0.2, 0.4, 0.6, 0.8, 1 and y = 0, 0.02, 0.04, 0.06, 0.08, 0.1). Sol-gel method was employed for synthesizing these hexagonal ferrites. The XRD plots of all studied materials which were annealed at 1250 °C show single phase characteristics. Lattice parameter ‘c’ increased as a consequence of larger radius of rare earth ion (Nd3+) as compared to (Fe3+), while lattice parameter ‘a’ showed very small variation. The cell volume was obtained in the range 2508.32–2523.75 (Å3). The inclusion of Nd-Ni also affected X-ray density, bulk density and porosity. The FTIR spectroscopy indicated the particular absorption peaks of hexagonal ferrites and it was performed in the range of 500–700 cm?1. On account of Nd-Ni doping, the dielectric constant, dielectric loss and AC-conductivity showed decreasing trend. The occupancy of Nd3+ ions at octahedral site impedes the valence alternation of Fe3+; therefore there was decrease in dielectric permittivity. Ac conductivity has been decreased from 9.14 to 6.49 (Ω cm)?1 at frequency of 2.7 GHz. The Cole-Cole plots of synthesized materials noticeably revealed grain boundary contribution. The appearance of single semi-circle in impedance Cole-Cole graphs confirms the exceptional role of grain boundaries in the conduction process. The considerably lower dielectric parameters of investigated nano X-type ferrites propose their feasibility for high-frequency applications (phase shifters, dielectric resonators, stealth technology etc). 相似文献
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K.M. Srinivasamurthy Jagadeesha Angadi V S.P. Kubrin Shiddaling Matteppanavar D.A. Sarychev P. Mohan Kumar Haileeyesus Workineh Azale B. Rudraswamy 《Ceramics International》2018,44(8):9194-9203
Ferrites may contain single domain particles which gets converted into super-paramagnetic state near critical size. To explore the existence of these characteristic feature of ferrites, we have performed magnetization(M-H loop) and Mössbauer spectroscopic studies of Ni2+ substitution effect in Co1-xNixFe2O4 (where x?=?0, 0.25, 0.5, 0.75 and 1) nanoparticles were fabricated by solution combustion route using mixture of carbamide and glucose as fuels for the first time. As prepared samples exhibit spinel cubic structure with lattice parameters which decreases linearly with increase in Ni2+ concentration. The M-H loops reveals that saturation magnetization(Ms), coercive field(Hc) remanence magnetization(Mr) and magnetron number(ηB) decreases significantly with increasing Ni2+ substitution. The variation of saturation magnetization has been explained on the basis of Neel's molecular field theory. The coercive field(Hc) is found strongly dependent on the concentration of Ni2+ and decrease of coercivity suggests that the particles have single domain and exhibits superparamagnetic behavior. The Mössbauer spectroscopy shows two ferrimagnetically relaxed Zeeman sextets distribution at room temperature. The dependence of Mössbauer parameters such as isomer shift, quadru pole splitting, line width and hyperfine magnetic field on Ni2+ concentration have been discussed. Hence our results suggest that synthesized materials are potential candidate for power transformer application. 相似文献
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在探讨了Web查询服务的典型模型后,论文阐述了服务器端会话追踪机制的实现方式,设计了基于服务器端会话追踪的Web查询服务的典型解决方案。该设计方案可以较为安全地保存和维护客户的上下文信息,可靠地跟踪用户查询所处的状态,有效地实现有状态的Web查询服务。 相似文献
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动态源路由协议是无线自组织网络众多路由协议中被广泛关注的一种按需路由协议,目前,关于该协议的优化措施有很多。本文先分析了动态源路由协议的一种优化机制——路由自动缩短,该机制能动态缩短处于工作状态路由的跳数,但不保证缩短路由的质量,在此基础上,提出一种自适应路由自动缩短机制,新机制既可缩短路由.又能保证缩短路由质量.理论分析及仿真结果表明,自适应路由缩短机制的各项性能优于原路由缩短机制。 相似文献
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An Improved Immune Genetic Algorithm for Solving the Optimization Problems of Computer Communication Networks 总被引:4,自引:0,他引:4
1 IntroductionIndesigningacomputercommunicationnet work ,thenetworkaveragedelayisanimportantpa rameterinthenetworkperformance .Inthispaper,weonlyconsiderM /M/1networks,whichmeansthatthemessageprocessingtimeisaprobabilisticdensityfunctionwithnegativepower,thegroupar rivalandsendingisofPoissiondistributionwithasinglequeue .Supposethatthenetworktopologicalstructureandtheestimatesoftheexternaltrafficrequirementsaregiven ,howtoselecttheoptimalroutestobeusedbythecommunicatingnodesinthenetworksoast… 相似文献
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现场总线控制系统是计算机、网络与自动控制三项技术相互结合的一门新技术。文章介绍了现场总线控制系统仪表网络的典型结构,对现场总线控制系统与集散控制系统进行了比较,论述了现场总线控制系统检查和调试的程序、内容与操作方法。 相似文献