فهرست مطالب

Majlesi Journal of Energy Management
Volume:5 Issue: 3, Sep 2016

  • تاریخ انتشار: 1395/09/15
  • تعداد عناوین: 6
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  • Hamed Aliabadi, Mehdi Zarif* Page 1
    Witricity has recently been considered as a wireless electric power transmission technology via near field non-radial magnetic coupling at limited distances. In this paper, an auto tuning system is introduced for wireless electric power transmission (WPT) systems which have the ability to use in both up frequency and down frequency unlike the other systems which can be designed only for one model of topologies in wireless power transmission system and doesn’t work in other approaches. As well as the ability to scan frequencies and find the right resonance frequency using information analysis receiving from voltage and capacitive reactance automatic compensation sensors from system requirements and also fulfill the conditions of ZVS and ZCS is another its capabilities. Increasing transmission efficiency and transmission power are the results of applying this system.
    Keywords: Wireless Power Transmission, Magnetic Coupling, Resonant Frequency, Impedance Adaptation, Zero Voltage Switching (ZVS), Zero Current Switching (ZCS), Coupling Mode Theory (CMT)
  • Seyed Mahdi Hosseini*, N. Ghaffarzadeh, E. Afjei Page 7
    In this paper, a new passive method of islanding detection is proposed based on energy of wavelet coefficients in Distributed Generation (DG) systems. This new method is developed for islanding detection based on measuring the utility voltage signals. These voltage signals are measured before the main circuit breaker of micro grid including wind turbine DFIG, diesel generator, battery and different loads. Signal’s features are processed and extracted by Discrete Wavelet Transform (DWT) and adequate decomposition level. This method detects the islanding condition with the Daubiches wavelets. Voltage signals are sampled at 20 KHZ. Features and wavelet coefficients are achieved from mean voltage of three phases and these parameters are used for distinguishing the islanding conditions from non-islanding ones. The proposed method has been examined under various scenarios including one phase fault, three phases fault, capacitor switching, load shedding and load injecting. The numerical studies show that feasibility and applicability of the proposed method with acceptable and satisfactory results. The results show that the proposed islanding detection method is able to detect islanding operation very fast in an efficient way. Matlab/Simulink software is employed for this purpose.
    Keywords: Energy Wavelet, Distributed Generation, Islanding Detection, Protection, Micro Grid
  • Sourena Kazemi Vaysari, Esmael Fallah Choolabi Page 15
    Power system is a nonlinear time-variant system with a large variety of disturbances among them is the Low Frequency Oscillations (LFO). It is necessary to have an appropriate Power System Stabilizer (PSS) which can stabilize the power system in different operating points. In this paper fuzzy logic has been used to design the stabilizer for a multi-machine power system. The main advantage of fuzzy logic is that a person can involve the experiences he has about the system’s behavior, in the design process. These experiences are implemented as fuzzy rules. In this paper a fuzzy PSS is designed to stabilize a typical two-area four-machine power system under a short-term 3 phase short circuit fault. Results show the advantages of the proposed stabilizer over the classic one in damping the local and inter-area oscillations.
    Keywords: Power System Stabilizer, Fuzzy Logic, Multi-Machine Power System
  • Mojtaba Sarlack, Vahid Amir* Page 21
    This paper presents a new combined technique for minimizing the power loss in distribution system by optimal Distributed Generation (DG) installation together with capacitor placement. Sensitivity analysis is used to identify the optimal candidate locations of DGs and capacitor placement. Installing the distributed generation sources and parallel capacitors can substantially improve the performance of the distribution systems and the problem of placement and finding the size of these sources is associated with equal and unequal constraints, in which a solution for minimizing the losses and costs in these systems is sought. In this paper, using the bat algorithm of placement and giving size, the capacitor and DG have been designed in such a way the most appropriate voltage profile in the buses are provided and the costs of system losses are considerably reduced. This study discusses a method for improving the voltage profile and minimizing the losses and costs. The solution is divided into two parts: (1) sensitivity factor of the losses is used for determining the optimal location of the capacitor and DG; and (2) a new algorithm for determining the size of the capacitor and DG for the target buses is used. Proposed method has been tested on IEEE 34-bus radial distribution system and the results obtained are encouraging.
    Keywords: Distribution System, Capacitor, Distributed Generation Sources, Reduction of Losses, Costs, Sensitivity analysis, Bat Algorithm
  • Sajad Fatahi*, Mojtaba Sarlack, Mohammad.S. Mehrabi Page 27
    In this paper, genetic algorithm was used in order to find the size of the place and the optimal type of the distribution transformers. A new updating strategy was applied in the proposed model in order to find the proper and possible responses that facilitate calculating the improvement of the optimization potentials. Some electrical constraints of this proposed model include permissible voltage drop at the end of the low pressure feeders, maximum loading capacity of the transformers, feeding all load points and the limitation of the radial structure of the distribution network. In the objective function, the problem of the equipment costs of the land, cables of low pressure, energy loss of the lines and transformers and geographical information of the network are considered that result in more viable responses in the process of designing the distribution system. Using this method, location and optimal capacity of the distribution substations and their feed domain are determined with respect to the minimum losses and economic issues. The results show the efficiency of the proposed method.
    Keywords: Optimal Placement, Genetic Algorithm, Distribution Networks, Distribution Transformers
  • M. Saadatmand*, B. Mozafari, G.B. Gharehpetian, E. Rasuli Page 35
    The advances in electronic technologies and emergence of modern industries, particularly electronic industries, have led to growing harmonic distortion in distribution networks. On the other hand, presence of harmonics in distribution networks is inevitable due to unfeasibility of complete removal of harmonic components, problems caused by introduction of filters into networks, load and distribution network requirements, changes in and expansion of power systems, etc. This presents another problem referred to as harmonic allocation which entails setting harmonic emission allowance for each load connected to network. IEC61000-6-3 gives practical guidelines for such applications. The findings and simulations results of the present study indicate that the equal harmonic power strategy is the most effective and precise candidate for accurate calculations in networks which are sensitive to harmonic distortion.
    Keywords: Harmonic allocation, Distribution network, IEC 61000-3-6, Harmonic distortion, Harmonic contribution