Mohammadi-ivatloo B.,Sharif University of Technology |
Rabiee A.,Islamic Azad University at Abhar |
Soroudi A.,Islamic Azad University at Damavand |
Ehsan M.,Sharif University of Technology
Energy | Year: 2012
Dynamic economic dispatch (DED) aims to schedule the committed generating units' output active power economically over a certain period of time, satisfying operating constraints and load demand in each interval. Valve-point effect, the ramp rate limits, prohibited operation zones (POZs), and transmission losses make the DED a complicated, non-linear constrained problem. Hence, in this paper, imperialist competitive algorithm (ICA) is proposed to solve such complicated problem. The feasibility of the proposed method is validated on five and ten units test system for a 24 h time interval. The results obtained by the ICA are compared with other techniques of the literature. These results substantiate the applicability of the proposed method for solving the constrained DED with non-smooth cost functions. Besides, to examine the applicability of the proposed ICA on large power systems, a test case with 54 units is studied. The results confirm the suitability of the ICA for large-scale DED problem. © 2012 Elsevier Ltd.
Bazzazian S.,Islamic Azad University at Abhar |
Besharat M.A.,University of Tehran
Psychology, Health and Medicine | Year: 2012
The aim of this study was to develop and test a model of adjustment to type I diabetes. Three hundred young adults (172 females and 128 males) with type I diabetes were asked to complete the Adult Attachment Inventory (AAI), the Brief Illness Perception Questionnaire (Brief IPQ), Task-oriented subscale of the Coping Inventory for Stressful Situations (CISS), D-39, and well-being subscale of the Mental Health Inventory (MHI). HbA1c was obtained from laboratory examination. Results from structural equation analysis partly supported the hypothesized model. Secure and avoidant attachment styles were found to have effects on illness perception, ambivalent attachment style did not have significant effect on illness perception. Three attachment styles had significant effect on task-oriented coping strategy. Avoidant attachment had negative direct effect on adjustment too. Regression effects of illness perception and task-oriented coping strategy on adjustment were positive. Therefore, positive illness perception and more usage of task-oriented coping strategy predict better adjustment to diabetes. So, the results confirmed the theoretical bases and empirical evidence of effectiveness of attachment styles in adjustment to chronic disease and can be helpful in devising preventive policies, determining high-risk maladjusted patients, and planning special psychological treatment. © 2012 Copyright Taylor and Francis Group, LLC.
Amiri M.,Islamic Azad University at Abhar |
Khanmohammadi S.,University of Tabriz
Applied Soft Computing Journal | Year: 2013
This paper introduces an approach to one of the most important problems in electrical power system called the Unit Commitment (UC). The proposed method PUC-MP which stands for the primary unit commitment-modification process, addresses this problem firstly by using a simple and new priority for operating the generating units in each hour, and then, using a modification process which enhances the solution quality with lower cost. The PUC-MP takes advantage of both deterministic and stochastic algorithms in its structure to solve the discrete-variable part of the UC problem for choosing a suitable combination of units in each hour, and also, continuous-variable part of it which is dispatching the operating units' output power to the power network load economically. The latter part which is called economic dispatch (ED) has been solved using an intelligent algorithm which in turn has been customized by two new ideas to increase its efficiency. Simulation results show that this new approach even without using its modification process can be considered as an effective approach which surpasses some other popular and recently reported methods in producing near-optimal and robust solutions. © 2012 Elsevier B.V. All rights reserved.
Shayeghi H.,University of Mohaghegh |
Bagheri A.,Islamic Azad University at Abhar
International Journal of Electrical Power and Energy Systems | Year: 2013
Since the emerging of distributed generation (DG) technologies, their penetration into power systems has provided new options in the design and operation of electric networks. In this paper, DG units are considered as a novel alternative for supplying the load of sub-transmission system. Thus, the mathematical model of considering DG on the expansion planning of sub-transmission system is developed. Fix and variable costs of the plan and the related constraints are formulated in the proposed model. The proposed objective function and its constraint are converted to an optimization problem where the hybrid decimal codification genetic algorithm (DCGA) and linear programming (LP) technique are employed to solve it. Solution of the proposed method gives the optimal capacity of substations; optimal location and capacity of DGs as well as optimal configuration of the sub-transmission lines. To demonstrate the effectiveness of the proposed approach, it is applied on a realistic sub-transmission system of Zanjan Regional Electrical Company, Iran, and the results are evaluated. © 2012 Elsevier Ltd. All rights reserved.
Amini J.,Islamic Azad University at Abhar
IEEE Transactions on Power Electronics | Year: 2014
Although inverters with high number of levels offer many merits, their utilization is hindered mainly by their complicated control. Overcoming this barrier gives them the opportunity to find more practical applications. This paper presents an effective closed-loop space-vector-based modulation algorithm to control flying capacitor multilevel inverters with linearly distributed flying capacitor voltages. This modulation technique drastically reduces the computational load. Besides, it is able to balance capacitor voltages more simply and effectively than other methods presented so far. It does not require any stored information from memory or a lookup table. Therefore, it permits online computation of the switching sequence. Moreover, due to the closed-loop structure of this method, the effect of system nonlinearity and capacitor voltage deregulation on performance of the modulation is reduced. Other advantages of the proposed algorithm are: low number of instructions, level-independent number of instructions, and simple extendibility to an arbitrary number of levels without considerable modification. © 2014 IEEE.
Ahadi P.,Islamic Azad University at Abhar
Advanced Materials Research | Year: 2011
Construction industry is one of the sectors that would highly benefit from Nanomaterials with new functionalities and enhanced performances. The use of Nanomaterials in this industry should be considered not only for enhancing material properties and functions but also in the context of energy saving. This paper, aims to keep special attention on low energy buildings which utilizes the key resources of energy or construction materials in a more efficient way than the conventional buildings. Using Nanomaterials in these cases include harvest solar or other forms of renewable energy and energy conservation. The paper presents also applications of more efficient and cheaper solar energy collectors with high flexibility, heat absorbing windows, energy coatings and Nanoinsulations. The flexible insulation allowed the panels to be thin enough to fit within the existing window casements without need to modify window and roof fixtures. The NanoHouse represents a successful method of explaining what Nanomaterials are and how they work. © (2011) Trans Tech Publications, Switzerland.
Hosseini S.A.,Islamic Azad University at Abhar
Annals of Nuclear Energy | Year: 2012
The very complex geometry of PBM type reactors along with software limitations have made the simulation of this type of reactor very difficult, even in the case of such flexible code's as MCNP. In this paper a new random distribution method is proposed for the pebbles inside the core. This method has the advantage of needing a limited number of surfaces and cells thus reducing computation time and making it usable in older versions of MCNP. Whilst keeping the geometry as simple as possible, as shown by our simulations, this new distribution method greatly enhances the results obtained in the criticality height benchmark. © 2012 Elsevier Ltd. All rights reserved.
Ghorbani A.,Islamic Azad University at Abhar
Electric Power Systems Research | Year: 2015
Distance relays detect transmission line faults and their locations by measuring the voltage and the current signals. Also, phase shifting transformers (PSTs) are used to control the power flow in electrical power systems. PSTs protect transmission lines from thermal overloading, improve the stability of transmission system and control the power flow between different networks. Unfortunately, existence of PST in a transmission line vitiates the operation of protection relays by altering the voltage and current signals. In this paper, the effects of the delta-hexagonal PST on the operation of distance relays are investigated by both analytical and computational methods under different fault types and locations. Results of investigations reveal that the PST causes the distance relays to under-reach. Finally, a feasible method for eliminating the PST detrimental effects on the operation of the distance relays is presented. This method uses the voltage difference between the PST terminals to modify the operation of the distance relays. The phasor measurement units (PMUs) are used to calculate this voltage and remote signal systems are used to transfer it to the system protection center (SPC). All the simulations are conducted with electro-magnetic transient program (EMTPWorks). © 2015 Elsevier B.V. All rights reserved.
Amini J.,Islamic Azad University at Abhar
Electric Power Components and Systems | Year: 2012
Although the doubly fed induction generator has many advantages over other configurations of wind energy conversion systems, it is not only susceptible to low power quality but also generates some power quality problems, such as harmonics. Proliferation of non-linear loads and high-scale penetration of doubly fed induction generator based turbines in the near future make disturbance rejection and harmonic reduction of these systems important issues. Therefore, this article aims to reduce the effects of the grid power quality problems on doubly fed induction generators and power quality problems caused by the doubly fed induction generator itself. To achieve this goal, the capability of the grid-side converter is extended by means of adding an active filtering function based on the voltage-detecting method. By this way, the fatal effects of system voltage disturbances and instantaneous active power oscillations can be reduced. Moreover, the proposed system is capable of damping out harmonic propagation phenomenon that is of great concern in offshore wind farms. In this system, to reduce harmonics emission of the doubly fed induction generator and further improve of its performance, a noise-shaping modulator, named, is utilized for modulation of rotor-and grid-side converters. Simulation results demonstrate the efficiency of proposed strategy. © 2012 Taylor and Francis Group, LLC.
Asgari S.,Islamic Azad University at Abhar |
Saffari R.,Guilan University
General Relativity and Gravitation | Year: 2012
In this paper we have considered a red-shift based linear correction in derivative of action in the context of vacuum f (R) gravity. Here we have found out that the linear correction may describe the late time acceleration which is appeared by SuperNovae Ia with no need of dark energy. Also we have calculated the asymptotic action for the desired correction. The value of all solutions may reduce to de' Sitter universe in the absence of correction term. © 2011 Springer Science+Business Media, LLC.