Showing 4 results for Eslami
T. Barforoushi, M. P. Moghaddam, M. H. Javidi, M. K. Sheik-El-Eslami,
Volume 2, Issue 2 (April 2006)
Abstract
Medium-term modeling of electricity market has essential role in generation
expansion planning. On the other hand, uncertainties strongly affect modeling and
consequently, strategic analysis of generation firms in the medium term. Therefore, models
considering these uncertainties are highly required. Among uncertain variables considered
in the medium term generation planning, demand and hydro inflows are of the greatest
importance. This paper proposes a new approach for simulating the operation of power
market in medium-term, taking into account demand and hydro inflows uncertainties. The
demand uncertainty is considered using Monte-Carlo simulations. Standard Deviation over
Expected Profit (SDEP) of generation firms based on simulation results is introduced as a
new index for analyzing the influence of the demand uncertainty on the behavior of market
players. The correlation between capacity share of market players and their SDEP is also
demonstrated. The uncertainty of inflow as a stochastic variable is dealt using scenario tree
representation. Rational uncertainties as strategic behavior of generation firms, intending to
maximize their expected profit, is considered and Nash-Equilibrium is determined using the
Cournot model game. Market power mitigation effects through financial bilateral contracts
as well as demand elasticity are also investigated. Case studies confirm that this
representation of electricity market provides robust decisions and precise information about
electricity market for market players which can be used in the generation expansion
planning framework.
H. Rajabi Mashhadi, S. M. Eslami, H. Modir Shanechi,
Volume 10, Issue 3 (September 2014)
Abstract
The main goal of this paper is to study statistical indices and evaluate AGC indices in power system which has large penetration of the WTGs. Increasing penetration of wind turbine generations, needs to study more about impacts of it on power system frequency control. Frequency control is changed with unbalancing real-time system generation and load . Also wind turbine generations have more fluctuations and make system more unbalance. Then AGC loop helps to adjust system frequency and the scheduled tie-line powers. The quality of AGC loop is measured by some indices. A good index is a proper measure shows the AGC performance just as the power system operates. One of well-known measures in literature which was introduced by NERC is Control Performance Standards(CPS). Previously it is claimed that a key factor in CPS index is related to standard deviation of generation error, installed power and frequency response. This paper focuses on impact of a several hours-ahead wind speed forecast error on this factor. Furthermore evaluation of conventional control performances in the power systems with large-scale wind turbine penetration is studied. Effects of wind speed standard deviation and also degree of wind farm penetration are analyzed and importance of mentioned factor are criticized. In addition, influence of mean wind speed forecast error on this factor is investigated. The study system is a two area system which there is significant wind farm in one of those. The results show that mean wind speed forecast error has considerable effect on AGC performance while the mentioned key factor is insensitive to this mean error.
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.
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.
