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Highly efficient three-phase grid-connected parallel inverter system

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Journal of Modern Power Systems and Clean Energy 2018年第5期6卷 1079-1089页

作者： Evren ISEN ahmet Faruk BAKAN Department of Electrical and Electronics Engineering Kirklareli University Department of Electrical Engineering Yildiz Technical University

In this paper, a new three-phase grid-connected inverter system is proposed. The proposed system includes two inverters. The main inverter, which operates at a low switching frequency, transfers active power to the grid. The auxiliary inverter processes a very low power to compensate for the grid current ripple. Thus, no active power is processed by the auxiliary inverter. The goal is to produce a grid current with a low total harmonic distortion(THD) and to obtain the highest efficiency from the inverter system. The main inverter is controlled via a space-vector pulse-width modulation owing to its optimum switching pattern, and the auxiliary inverter is controlled via a hysteresis current-control technique owing to the technique's fast dynamic response. The proposed system is analyzed in terms of different DC-link voltage, switching frequency,and filter inductance values. The optimum system parameters are selected that provide a THD value of less than 5%.A prototype inverter system at a 10 kW output power has been implemented. The main inverter operates at a 3 kHz switching frequency, and the auxiliary inverter compensates for the grid-current ripple. In total, a THD of 4.33%and an efficiency of 97.86% are obtained using the proposed inverter system prototype.

关键词： Active filter Inverter efficiency Ripple cancellation Three-phase grid-connected inverter

Numerical Solution of the Three-Dimensional Helmholtz Equation

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Chinese Physics Letters 2010年第6期27卷 1-4页

作者： Syed Tauseef Mohyud-Din ahmet Ylldlrim Department of Basic Sciences HITEC University Taxila Cantt Pakistan Department of Mathematics Ege University 35100 Bornova-izmir Turkey

We apply the homotopy analysis method to solve the nonhomogeneous multidimensional partial differential equation model problem. The analytic solutions are calculated in terms of convergent series with easily computable components. The nonhomogeneous problem is quickly solved by observing the self-canceling ＂noise＂ terms whose sum vanishes in the limit. Numerical results clearly reveal the complete reliability and efficiency of the proposed algorithm.

关键词： HELMHOLTZ equation -- Numerical solutions DIMENSIONAL analysis HOMOTOPY theory PARTIAL differential equations STOCHASTIC convergence NUMERICAL analysis

Acoustic beam splitting in a sonic crystal around a directional band gap

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Chinese Physics B 2013年第11期22卷 350-355页

作者： ahmet Cicek Olgun Adem Kaya Bulent Ulug Department of Physics Faculty of Arts and Sciences Mehmet Akif Ersoy University Department of Computer Education and Educational Technology Faculty of Education Inonu University 44280 Department of Physics Faculty of Science Akdeniz University

Beam splitting upon refraction in a triangular sonic crystal composed of aluminum cylinders in air is experimentally and numerically demonstrated to occur due to finite source size, which facilitates circumvention of a directional band gap. Experiments reveal that two distinct beams emerge at crystal output, in agreement with the numerical results obtained through the finite-element method. Beam splitting occurs at sufficiently-small source sizes comparable to lattice periodicity determined by the spatial gap width in reciprocal space. Split beams propagate in equal amplitude, whereas beam splitting is destructed for oblique incidence above a critical incidence angle.

关键词： sonic crystal directional band gap source size beam splitting

Microstructure and Property Relationships in Resistance Spot Weld between 7114 Interstitial Free Steel and 304 Austenitic Stainless Steel

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Journal of Materials Science & Technology 2006年第3期22卷 375-381页

作者： ahmet Hasanba■o■lu Ramazan Kaar Department of Metal Education Karabük Technical Education Faculty Karabük 78100 Turkey

Due to the differences in physical, chemical and mechanical properties of the base metals, the resistance spot welding of dissimilar materials is generally more challenging than that of similar materials. The influence of the primary welding parameters affecting the heat input such as peak current on the morphology, microhardness, and tensile shear load bearing capacity of dissimilar welds between 304 grades austenitic and 7114 grade interstitial free steel has been investigated in this study. The optimum welding parameters producing maximum joint strength were established at a peak current of 9 kA, where the electrode force is kept 6×10^-5 Pa and weld time is kept constant 17 cycles, respectively. The primary cause of weakening the weldment is identified as the excessive grain growing region of heat affected zone （HAZ） in case of 7114 grade interstitial free steel.

关键词： Resistance spot weld Interstitial free steel Austenitic stainless steel

Analytical Approach to Space- and *** Burgers Equations

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Chinese Physics Letters 2010年第9期27卷 38-41页

作者： ahmet Yildirim Syed Tauseef Mohyud-Din Department of Mathematics Ege University 35100 Bornova-Izmir Turkey HITEC University Taxila Cantt Pakistan

A scheme is developed to study numerical solution of the space- and time-fractional Burgers equations under initial conditions by the homotopy analysis method. The fractional derivatives are considered in the Caputo sense. The solutions are given in the form of series with easily computable terms. Numerical solutions are calculated for the fractional Burgers equation to show the nature of solution as the fractional derivative parameter is changed.

关键词： BURGERS' equation SPACE & time DIFFERENTIAL equations -- Numerical solutions HOMOTOPY theory FRACTIONAL calculus MATHEMATICAL analysis

Exact solutions of some fractional differential equations arising in mathematical biology

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International Journal of Biomathematics 2015年第1期8卷 29-45页

作者： Ozkan Guner ahmet Bekir Department of Management Information Systems School of Applied Sciences Dumlup~nar University Kutahya Turkey Department of Mathematics and Computer Art-Science Faculty Eskisehir Osmangazi University Eskisehir Turkey

In the last decades Exp-function method has been used for solving fractional differential equations. In this paper, we obtain exact solutions of fractional generalized reaction Duff- ing model and nonlinear fractional diffusion-reaction equation. The fractional derivatives are described in the modified Riemann-Liouville sense. The fractional complex trans- form has been suggested to convert fractional-order differential equations with modified Riemann-Liouville derivatives into integer-order differential equations, and the reduced equations can be solved by symbolic computation.

关键词： Fractional partial differential equation exact solutions Exp-function method modified Riemann-Liouville derivative.

Dark Soliton Solutions of Space-Time Fractional Sharma–Tasso–Olver and Potential Kadomtsev–Petviashvili Equations

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Communications in Theoretical Physics 2017年第2期67卷 182-188页

作者： Ozkan Guner Alper Korkmaz ahmet Bekir Cankiri Karatekin University Department of International Trade Cankiri 18200 Turkey ankiri Karatekin University Department of Mathematics Cankiri 18200 Turkey Eskisehir Osniangazi University Department of Mathematics & Computers Eskisehir 26200 Turkey

Dark soliton solutions for space-time fractional Sharma–Tasso–Olver and space-time fractional potential Kadomtsev–Petviashvili equations are determined by using the properties of modified Riemann–Liouville derivative and fractional complex transform. After reducing both equations to nonlinear ODEs with constant coefficients, the tanh ansatz is substituted into the resultant nonlinear ODEs. The coefficients of the solutions in the ansatz are calculated by algebraic computer computations. Two different solutions are obtained for the Sharma–Tasso–Olver equation as only one solution for the potential Kadomtsev–Petviashvili equation. The solution profiles are demonstrated in 3D plots in finite domains of time and space.

关键词： exact solution modified Riemann–Liouville derivative space-time fractional Sharma–Tasso–Olver equation space-time fractional potential Kadomtsev–Petviashvili equation

Solving Space-Time Fractional Differential Equations by Using Modified Simple Equation Method

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Communications in Theoretical Physics 2016年第5期65卷 563-568页

作者： Melike Kaplan Arzu Akbulut ahmet Bekir Eskisehir Osmangazi University Art-Science Faculty Department of Mathematics-Computer

In this article,we establish new and more general traveling wave solutions of space-time fractional Klein–Gordon equation with quadratic nonlinearity and the space-time fractional breaking soliton equations using the modified simple equation *** proposed method is so powerful and effective to solve nonlinear space-time fractional differential equations by with modified Riemann–Liouville derivative.

关键词： symbolic computation exact solution space-time fractional differential equation space-time fractional Klein–Gordon equation the space-time fractional breaking soliton equations

The efficiency of direct integration methods in elastic contact-impact problems

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Acta Mechanica Sinica 2005年第4期21卷 395-401页

作者： Ibrahim H.Guzelbey ahmet Erklig Bahattin Kanber University of Gaziantep Mechanical Engineering DepartmentGaziantep-Turkey

A comparison of direct integration methods is madeand their efficiency is investigated for impact ***-mark,Wilson-θ,Central Difference and Houbolt Methodsare used as direct integration *** analysisincludes that of elastic and large deformation based uponupdated Lagrangian including buckling *** resultsshow that the direct integration methods give differentresults in different contact-impact cases.

关键词： Elastic impact,Direct integration methods,Finite strain Contact