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Öğe 4Nx Non-Isolated and Non-Inverting Hybrid Interleaved Multilevel Boost Converter Based on VLSIm Cell and Cockroft Walton Voltage Multiplier for Renewable Energy Applications(Institute of Electrical and Electronics Engineers Inc., 2017) Bhaskar, M.S.; Padmanaban, S.; Blaabjerg, F.; Norum, L.E.; Ertas, A.H.In this treatise, 4Nx hybrid Non Inverting & Non Isolated (NI-NI) DC-DC interleaved multi-level boost converter (4Nx IMBC) for renewable energy applications is proposed. The proposed 4Nx IMBC is derived by coalescing the feature of 2Nx DC-DC Interleaved Multi-level Boost Converter (2Nx IMBC), voltage-lift-switched-inductor-modified (VLSIm Cell) and Cockcroft Walton (CW) voltage multipliers. The 4Nx converter provides 4N times more conversion voltage ratio compared to conventional boost converter where N denotes the number of output stages of the 4Nx IMBC. To make renewable energy sources applicable at user end its DC voltage magnitude needs to be incremented with high conversion. Existing and recently proposed DC-DC converter are not sufficiently expert to employ practically, because of stability issues, high duty cycle and high ripple in the output. To overcome the conversion ratio problem isolated boost DC-DC converter are in use but it makes circuitry bulky and costly because of transformer and several coupled inductors. The converter topology proposed in this treatise reduces the output ripple and overcome the problem mentioned above without exploiting extreme values of duty cycle or transformers. Simulations results of proposed circuitry are presented which verify the analysis, function, working modes & feasibility of proposed circuitry converter. © 2016 IEEE.Öğe Creep simulation of a micro-CT based finite element model of porcine cancellous bone(2011) Ertas, A.H.; Sindelar, B.J.; Cotton, J.R.[No abstract available]Öğe Determination of fatigue and static strength of scots pine and beech wood(Statny Drevarsky Vyskumny Ustav, 2015) Yildirim, M.N.; Uysal, B.; Ozcifci, A.; Ertas, A.H.In this study, fatigue and static strength of Scots pine (Pinus sylvestris L.) and beech (Fagus orientalis L.) woods were investigated. The fatigue and static strength were conducted using a three point bending test-rig. The specimens were prepared according to ISO 3129 (1975) and fatigue and static bending test were carried out according to ISO 3133 (1975). The fatigue test was carried out at 80, 70, 60, 50 and 40 % stress level that corresponded to specific percentage of material's ultimate strength modulus of rupture (MOR). However the microstructures of fatigue failures were observed by using scanning electron microscope (SEM). The results were indicated that, the fatigue life of Scots pine wood amounted to over 1 million cycle when the stress level was 40 % of MOR for Scots pine and 50 % MOR for Beech. In general, fatigue life decreased as stress level increased and vice versa. The allowable design stress is based on some percentage of MOR for furniture design. On this account, the allowable design stresses for Beech and Scots pine could be set at 50 and 40 % respectively.Öğe Dual mode control of inverter to integrate solar-wind hybrid fed DC-grid with distributed AC grid(Institute of Electrical and Electronics Engineers Inc., 2016) Awasthi, A.; Venkitusamy, K.; Selvamuthukumaran, R.; Padmanaban, S.; Siano, P.; Ertas, A.H.This paper presents integration of solar-wind hybrid fed DC-grid to distributed AC grid. Generally, the renewable hybrid energy systems use two or more energy sources to supply power to the dc grid. In case of insufficient power generation or excessive load demand, in order to supply power to DC loads, it must integrate with AC grid. As dc loads increase in number, complexity increases and tighter voltage regulation is required. This paper presents dual mode control operation of inverter which integrates the solar and wind power fed dc bus to the single phase ac distribution system. The inverter can be operated in hysteresis current control when power is fed from DC grid to AC distributed grid and in AC-DC boost rectifier mode otherwise. The detailed operation of dual mode control of inverter is described in this paper. The effectiveness of the proposed system has been verified through simulation studies using MATLAB/SIMULINK. © 2016 IEEE.Öğe Proposed novel multiphase-multilevel inverter configuration for open-end winding loads(Institute of Electrical and Electronics Engineers Inc., 2016) Padmanaban, S.; Wheeler, P.; Blaabjerg, F.; Ertas, A.H.; Ojo, J.O.; Szczesniak, P.This paper presents a new multiphase-multilevel inverter configuration for open-winding loads and suitable for medium power (low-voltage/high-current) applications such as 'More Electric Aircraft'. Modular structure comprised of standard dual three-phase voltage source inverter (VSI) along with one additional bi-directional semi-conductor device (MOSFET/IGBT) per phase and two capacitors with neutral point. The additional switches and capacitors are introduced to generate the additional voltage levels in outputs of the VSI. An original modified single carrier five-level modulation (MSCFM) algorithm is developed in this work and overcomes the complexity of standard space vector modulations, easy for real implementation purposes in digital processors. Proposed six-phase multilevel inverter configuration generates multilevel outputs with benefit in comprises with standard multilevel inverter topologies. Further, the complete numerical model of the proposed AC converter along with pulse-width modulation (PWM) is developed with Matlab/PLECS simulation software's. A set of observed results is presented in balanced working condition and always shown good agreement with the theoretical developments. © 2016 IEEE and EPE Association.Öğe A review of robust image enhancement algorithms and their applications(Institute of Electrical and Electronics Engineers Inc., 2016) Irmak, E.; Ertas, A.H.The essential target of image enhancement is to minimize noise from a digital image by keeping the intrinsic information of the image preserved. The main difficulty in image enhancement is determining the criteria for enhancement and, therefore, more than one image enhancement techniques are empirical and require interactive procedures to obtain satisfactory results. In this paper robust image enhancement algorithms are discussed, implemented to noisy images and compared according to their robustness. The algorithms are especially able to improve the contrast of medical images, fingerprint images and selenography images by means of software techniques. When deciding that one image has better quality than another image, quality measure metrics are needed. Otherwise comparing image quality just by visual appearance may not be objective because images could vary from person to person. That is why quantitative metrics are crucial to compare images for their qualities. In this paper Peak Signal to Noise Ratio (PSNR) and Mean Squared Error (MSE) quality measure metrics are used to compare the image enhancement methods systematically. All the methods are validated by the performance measures with PSNR and MSE. It is believed that this paper will provide comprehensive reference source for the researchers involved in image enhancement field. © 2016 IEEE.Öğe Single-phase seven-level stack multicell converter using level shifting SPWM technique(Institute of Electrical and Electronics Engineers Inc., 2016) Padmanaban, S.; Siano, P.; Ertas, A.H.; Selvamuthukumaran, R.; Maroti, P.K.This paper presents a single-phase seven-level stack multicell converter (SMC) which provides a viable solution for multilevel converter. Conventional cascaded multilevel inverter (MLI) removes the drawbacks of clamping diodes and clamping capacitors topologies. However, in a cascaded MLI number of voltage source and power switches increases as the number of level increases. The main advantage of single-phase SMC converter is only two DC sources are needed for any number of levels. Level shifting SPWM technique has been incorporated to achieve gate pulses, in which carrier wave of 20kHz is compared with 50Hz sinusoidal reference wave at a modulation index of 1 and 0.9. Total harmonic distortion (THD) for SMC converter is achieved at 1.55% and 5.26% with and without filter respectively. The seven-level SMC topology is simulated in MATLAB/SIMULINK and simulation results are provided to verify the performance. © 2016 IEEE.Öğe Transfer function modeling of parallel connected two three-phase induction motor implementation using LabView platform(Institute of Electrical and Electronics Engineers Inc., 2015) Gunabalan, R.; Sanjeevikumar, P.; Blaabjerg, F.; Wheeler, P.W.; Fedak, V.; Ertas, A.H.This paper presents the transfer function modeling and stability analysis of two induction motors of same ratings and parameters connected in parallel. The induction motors are controlled by a single inverter and the entire drive system is modeled using transfer function in LabView. Further, the software is used to perform the stability analysis of the parallel connected induction motor drive under unbalanced load conditions. It is very simple compared with the methods discussed so far to study the performance of the drive under unbalanced load conditions. Control design and simulation toolkits are used to model the drive system and to study the stability analysis. Simulation is done for various operating conditions and the stability investigation is performed for different load conditions and difference in stator and rotor resistances among the two motors. © 2015 IEEE.
