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57 results on '"Khan, Naveed Ahmad"'

52. Hybrid Nearest Level and open loop control of Modular Multilevel Converters with N+1 and 2N+1 levels

Author

Khan, Naveed Ahmad, Vanfretti, Luigi, Li, Wei, and Haider, Arif

Subjects
Other Electrical Engineering, Electronic Engineering, Information Engineering, Voltage Source Converter (VSC), Modulation Strategy, Modeling, Annan elektroteknik och elektronik, Multilevel Converters, Simulation
Abstract

In this paper a Nearest Level Control with open loop approach for modular multilevel converter (MMC) is proposed. By using open loop approach it is possible to suppress circulating currents without using feedback controllers. Moreover, with this method, both N+1 and 2N+1 levels (N=number of sub-modules) can be obtained at the output voltage. In addition, the voltage quality is improved and the total harmonic distortion is reduced at higher and lower modulation indices by increasing the number of levels up to 2N+1. Simulation results of 3-phase MMC are presented for both 2N+1 and N+1 levels together with the description of proposed Nearest Level Control scheme. QC 20150319

Published
2014

53. Generic High Level VSC-HVDC Grid Controls and Test Systems for Offline and Real Time Simulation

Author

Hasan, Md Rokibul, Vanfretti, Luigi, Li, Wei, Khan, Naveed Ahmad, Hasan, Md Rokibul, Vanfretti, Luigi, Li, Wei, and Khan, Naveed Ahmad

Abstract

This article describes generic high level control models for VSC-HVDC grid systems. An average value model of the voltage source converter (VSC) is used; it includes the vector current control strategy. As an improvement to traditional conventional high-level control systems, this paper includes dc voltage, negative sequence current and dc voltage droop control loops. To validate the controller's performances, two tests systems were developed: a point-to-point link and a four-terminal DC grid. Both offline and real-time simulations are carried out for several test scenarios. A methodology for calibrating controller parameters is presented and used to tune the controls of each test system considering the different scenarios presented. All simulation models were developed in SimPowerSystem/Simulink and prepared using the RT-LAB software from Opal-RT for real-time simulation; real-time simulation performance of the simulation models is also discussed., QC 20150116

Published
2014
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57. Theoretical Analysis on Absorption of Carbon Dioxide (CO 2) into Solutions of Phenyl Glycidyl Ether (PGE) Using Nonlinear Autoregressive Exogenous Neural Networks.

Author

Khan, Naveed Ahmad, Sulaiman, Muhammad, Tavera Romero, Carlos Andrés, and Alarfaj, Fawaz Khaled

Subjects
*PHENYL ethers, *CARBON dioxide analysis, *CARBON dioxide, *ARTIFICIAL neural networks, *NONLINEAR differential equations, *CARBON dioxide adsorption
Abstract

In this paper, we analyzed the mass transfer model with chemical reactions during the absorption of carbon dioxide (CO 2 ) into phenyl glycidyl ether (PGE) solution. The mathematical model of the phenomenon is governed by a coupled nonlinear differential equation that corresponds to the reaction kinetics and diffusion. The system of differential equations is subjected to Dirichlet boundary conditions and a mixed set of Neumann and Dirichlet boundary conditions. Further, to calculate the concentration of CO 2 , PGE, and the flux in terms of reaction rate constants, we adopt the supervised learning strategy of a nonlinear autoregressive exogenous (NARX) neural network model with two activation functions (Log-sigmoid and Hyperbolic tangent). The reference data set for the possible outcomes of different scenarios based on variations in normalized parameters (α 1 ,   α 2 ,   β 1 ,   β 2 ,   k) are obtained using the MATLAB solver "pdex4". The dataset is further interpreted by the Levenberg–Marquardt (LM) backpropagation algorithm for validation, testing, and training. The results obtained by the NARX-LM algorithm are compared with the Adomian decomposition method and residual method. The rapid convergence of solutions, smooth implementation, computational complexity, absolute errors, and statistics of the mean square error further validate the design scheme's worth and efficiency. [ABSTRACT FROM AUTHOR]

Published
2021
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