مجله کیفیت و بهره وری صنعت برق ایران
سال چهارم شماره 2 (پیاپی 8، پاییز و زمستان 1394)

Abstract- In this study, an optimal solution for day-ahead programming in a Security Constrained Unit Commitment (SCUC) problem in power system has been presented. In fact this programming concentrates on providing coordination between generation units when a variation in load constraints is occurred. The goal of this coordination is to reduce the power system total cost. A practical and accurate method called Particle Swarm Optimization (PSO) has been used to solve this problem. The system considered in this study contains thermal and photovoltaic units. Monte Carlo method has been employed to model the uncertainty of photovoltaic units and system load. The objective function in this optimization is a second order polynomial including fuel and operation costs. Results of simulation shows that unit commitment programming with this method decrease system operation costs remarkably and simultaneously satisfies all system constraints. This method has higher accuracy and convergence speed with respect to the conventional methods.

Using more accurate approaches to evaluate the efficiency of the Iranian electricity distribution companies will help to planner to identify the best practice companies among others and enhance the quality of customer services. Usually, the data envelopment analysis (DEA) and stochastic frontier analysis (SFA) were used to assess the efficiency of decision making units. Besides the advantages of each of these methods, they have some drawbacks such as lack of proper severability or the need to shape of the production function. In this paper, stochastic nonparametric envelopment of data (StoNED) approach which combines with the two mentioned methods and has the advantages of both, are proposed to evaluate the efficiency of 39 Iranian electricity distribution companies. We defined proper input and output variables for evaluating the efficiency of each case. The proportion of underground cables in the total length of the network is taken into account as a contextual variable which is the proposed method considers a variable to better control for the heterogeneity of the firms and their operating environments. The Iranian firms based of the DEA and StoNED are evaluated and ranked. The results show, the ranking by StoNED are more reliable than the DEA. Isfahan and Kermanshah companies have the highest rank and are benchmark for others.

Electric vehicles are among the elements which can play an effective role in improving the network's reliability. To utilize this potential, creating desirability in vehicle owners can increase their participation in plans offered by electric utilities. Thus, reduction of distances traveled by vehicles from their initial place to parking lots, in addition to sharing the benefits raised form their participation in the plan with them, can increase this cooperation. In this paper, by proposing a statistical model for the presence of electric vehicles in the network and by introducing two scenarios for choosing the parking lots, the improvement of network's reliability is dealt with besides the reduction of the distances traveled by vehicles. The effects of car owner's behavior in choosing the parking lots as well as the effects of the distance between the vehicles and parking lots are among the innovations of this paper. The combination of goals using fuzzy function, along with utilizing and comparing the performance of Genetic Algorithm, Particle Swarm Optimization and Gravitational Search, are the other subjects of this paper.

Abstract: In order to enhance the quality, Economic life and improving the reliability, In the attainment of electricity required supply, Performance evaluation of supervised (Generation, transmission and distribution above) each Regional Electricity Company As a challenge to be felt In Iran. This paper uses a three-stage DEA approach Data collected from 16 regional electricity companies During the 2006- 2013 period are evaluated and analyzed. One innovative aspect of this research Electricity Industry analysis DEA is a three-step approach . The study, by using a three-stage DEA The relative efficiency regional electricity companies with three different measures. Then the for measuring validity of the three models The effect of the independent variables (inputs and outputs of the model) The dependent variable (efficiency scores obtained by each model) Multiple regression was used. The results of the analysis of efficiency scores, The best model in three steps Generation, transmission and distribution of these shows. The average efficiency of 16 Regional Electricity Company of the year 2006 to 2011, a decreasing trend and from 2011 to 2013 has increasing trend. Regional electricity companies Tehran, Gilan and Khorasan highest efficiency rating and the regional electricity companies Sistan and Baluchistan, Mazandaran has the lowest efficiency rating in 2013 and also the results efficiency decomposition shows the transmission and the distribution the greatest impact on the overall efficiency of the regional electricity companies .

In this paper, a soft switching buck dc/dc converter applicable for fuel cell has been analyzed and the complete details of designing have been presented. Reduction in switching losses and the elimination of voltage/current stresses of the switches are the major advantages of the aforementioned converter. In this converter, the switches are to be ON under zero voltage and zero current conditions, whereas they are to be OFF under zero voltage condition. This converter can be used in high switching frequency. In this paper, the principles of the performance, full details of the analyses of conduction modes, and designing approach have been presented. The performance and correct operation of the converter are validated by the experimental and simulation in PSCAD/EMTDC software.

In this paper, a new structure for quasi-Z-source inverters based on the combination of switched inductors and transformers is proposed. In the proposed inverter, the high voltage gain is achieved by increasing the ratio of the transformer and the number of switched inductor cells. For proposed structure, the principles operation and calculations of voltage gains and average value of the voltage across the capacitors are provided. Power losses of the proposed structure are calculated and the efficiency comparison between the proposed and other structures is given. To determine the advantages and disadvantages of the proposed inverter, the comprehensive comparison between the proposed and conventional topologies is given. To prove the correctness operation of the proposed inverter, the simulation results in PSCAD/EMTDC are used.

Using energy hub concept has been increased as a way of implementing multi-carrier energy systems in recent years. It still needs more study and examination in both modeling and operating concerns. In this regard, in this paper optimal operation of an energy hub in restructured power system is investigated. Operation includes decision making to procure large consumer energies. A model is proposed considering an energy hub with electrical and gas energy as inputs and electrical and heat energy as outputs. Electrical energy is procured in various ways including: buying from bilateral contract, buying from pool market and generating by a Combined Heat and Power (CHP) unit. Heat demand is also procured by a CHP and furnace. Buying from pool market is faced with uncertainty. In addition, electrical loads have uncertainty, constantly. These uncertainties complicate the decision making process and cause unfavorable conditions. Conditional Value at Risk (CVaR) as a known risk index is used in order to decrease unfavorable states. Real data are utilized to simulate, as much as possible. Efficiency of proposed model is verified by various simulations.