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Showing 2 results for Sheikholeslami

M. A. Taghikhani, A. Sheikholeslami, Z. Taghikhani,
Volume 11, Issue 2 (June 2015)
Abstract

This paper presents a new method for evaluation and simulation of inrush current in various transformers using operational matrices and Hartley transform. Unlike most of the previous works, time and frequency domain calculations are conducted simultaneously. Mathematical equations are first represented to compute the inrush current based on reiteration and then Hartley transform is used to study harmonic effects in the frequency domain. Being a real valued function and accordingly giving results with the higher speed of calculations are the main features of Hartley transform. The inrush problem is initially solved for single-phase transformers for switching at different angles of the voltage waveform using this method and then the results of harmonic domain are compared with that of Fourier transform. The methodology is also applied to three-phase three-limb transformers since the analysis of their transient behavior is significant owing to the flux coupling interactions in multi-leg core structures. The feasibility and efficacy of the method is illustrated with appropriate circuits and MATLAB code is developed to get the time and frequency domain waveforms with high accuracy. The results are helpful to identify and evaluate inrush current harmonic effects in various transformers and hence the efficiency of the method is verified.

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M. Ajoudani, A. Sheikholeslami, A. Zakariazadeh,
Volume 16, Issue 4 (December 2020)
Abstract

The development of communications and telecommunications infrastructure, followed by the extension of a new generation of smart distribution grids, has brought real-time control of distribution systems to electrical industry professionals’ attention. Also, the increasing use of distributed generation (DG) resources and the need for participation in the system voltage control, which is possible only with central control of the distribution system, has increased the importance of the real-time operation of distribution systems. In real-time operation of a power system, what is important is that since the grid information is limited, the overall grid status such as the voltage phasor in the buses, current in branches, the values of loads, etc. are specified to the grid operators. This can occur with an active distribution system state estimation (ADSSE) method. The conventional method in the state estimation of an active distribution system is the weighted least squares (WLS) method. This paper presents a new method to modify the error modeling in the WLS method and improve the accuracy SVs estimations by including load variations (LVs) during measurement intervals, transmission time of data to the information collection center, and calculation time of the state variables (SVs), as well as by adjusting the variance in the smart meters (SM). The proposed method is tested on an IEEE 34-bus standard distribution system, and the results are compared with the conventional method. The simulation results reveal that the proposed approach is robust and reduces the estimation error, thereby improving ADSSE accuracy compared with the conventional methods.


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© 2022 by the authors. Licensee IUST, Tehran, Iran. This is an open access journal distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license.