فهرست مطالب

  • Volume:1 Issue:2, 2016
  • تاریخ انتشار: 1395/09/24
  • تعداد عناوین: 7
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  • H Saboori, S Dehghan, Shahram Jadid * Pages 47-56
    Renewable energy sources (RES), especially wind power plants, have high priority of promotion in the energy policies worldwide. An increasing share of RES and distributed generation (DG), should, as has been assumed, provide improvement in reliability of electricity delivery to the customers. Paper presented here concentrates on electricity storage systems technologies and applications pinpointing renewable energies variability removal. It can be seen from presented issues that there are numerous options to energy storage systems which can assist in generation and load shifting, peak shaving, transmission expansion planning deferral, ancillary services procurement, and power quality issues. Focus of applications is on renewable resources intermittency elimination. Some related issues including relation between electricity markets and storage systems, system expansion and storage systems, and correlation among smart grid issues and storage systems are also presented. As a result, some comparisons are conducted in terms of various interested criterions in the field of energy storage comprising storage capacity, power level, response time, unit investment and operation costs, round trip efficiency, physical dimensions, cycle life time, life time, availability, and environmental impacts.
    Keywords: Ancillary services procurement, electricity market, energy storage systems (ESS), renewable energy resources, smart grid, storage applications
  • Javad Gholinezhad, Mahmood Ebadian *, Mohammad Aghaebrahimi Pages 57-64
    When power systems are expanded and connected together with weak tie lines, the low-frequency oscillations are increased and the stability margin of the power system decreases. Therefore, when designing the transmission system to be used, it is necessary to maintain the dynamic stability of the power system, and to make sure to have the most possible stability margin. SSSC is a FACTS device connected in series with power transmission lines. SSSC can control power flow very effectively and can inject series inductive or capacitive voltages into the line. In this paper, a new control strategy based on voltage measurement for the SSSC is proposed. The commonly used strategy for SSSC is based on line current measurement; consequently, the injected voltage is in quadrature with the line current. But in the proposed strategy, the injected voltage is in quadrature with the ac voltage at the point of common coupling (PCC) of SSSC. With modifications done in the proposed strategy, compared with the conventional control method, it can be adjusted easily to control the power flow of the transmission line. The simulation is performed in single-machine and multi-machine power systems. The analysis of the results under different disturbances show that the proposed strategy has an appropriate response with respect to the changes in the system states and it is relatively faster in damping power system oscillations, compared with the conventional strategy.
    Keywords: Static Synchronous Series Compensator (SSSC), voltage frame strategy, current frame strategy, damping controller, dynamic stability
  • A Parizad, A.H Akhazali, Mohsen Kalantar * Pages 65-72
    Due to the increasing interest on renewable sources in recent years, the studies on integration of distributed generation to the power grid have rapidly increased. In order to minimize line losses of power systems, it is crucially important to define the size and location of local generation to be placed. Minimizing the losses in the system would bring two types of saving, in real life, one is capacity saving and the other one is energy saving. In this paper, our aim would be optimal distributed generation allocation for voltage profile improvement and loss reduction in distribution network. Harmony Search algorithm (HSA) was used as the solving tool; the problem is defined and objective function is introduced according to losses, security and cost indices. The applied load flow method is based on the equivalent current injection that uses the bus-injection to branch-current (BIBC) and branch-current to bus-voltage (BCBV) matrices which were developed based on the topological structure of the distribution systems. This method is executed on 13 bus unbalanced distribution system and show robustness of this method in optimal and fast placement of DG, efficiency for improvement of voltage profile, reduction of power losses and cost.
    Keywords: Unbalanced radial distribution network, Distribution load flow, power losses, Harmony Search algorithm (HSA), Optimal placement
  • Reza Shariatinasab *, Z Ejtemaee, J Gholinezhad Pages 73-82
    Power system overvoltages due to switching, lightning and other disturbances are the main problem for designers of the power transformers. Once some frequencies of the incoming surges match with some of the natural frequencies of transformer winding, the resonance phenomenon is expected in transformer winding. The resonant overvoltages may destroy the insulation between turns and cause to insulation failure or transmformer damage. In this paper, the transformer winding is modeled based on the lattice diagram concept with variable parameters and the IEEE model of surge arresters has been utilized in order to perform the simulations.  For internal protection of transformer windings, it is assumed that ZnO varistors are installed in parallel to the winding turns. Also the effect of ZnO varistors in reducing the voltage stress across the transformer winding has been investigated for the case of grounded and insolated nutral winding.
    Keywords: Zno oxide arrester, transient stresses, internal protection, transformer winding
  • M Shahnazari, Abolfazl Vahedi * Pages 83-88
    Accurate modeling of the wind energy conversion system is necessary to design and implementation of the control loop for the generator and the frequency converter, in order to extract maximum power from the wind and to investigate the effects of interconnection between wind farms and power system. In this paper the combination of a permanent magnet synchronous generator loaded with a diode rectifier, used in wind energy conversion system, is modeled using a state machine approach. The model is validated through comparison of the proposed model and the experimental results.
    Keywords: wind energy conversion system, permanent magnet synchronous generator, rectifier, state machine model
  • Ali Saberi Noughabi *, Nader Hatefi Torshizi, Hamidreza Najafi Pages 89-96
    In this paper, an interval approach is presented to achieve perfect selectivity and maximum sensitivity in distance relay zones, considering uncertainties. For this purpose, first, the uncertainties affecting the settings of the three zones of a distance relay are discussed. Then, by using the Monte-Carlo simulation, the uncertainties are modelled and the impedances seen by the distance relay are obtained for internal and external faults of the protection zones. Under such conditions, the impedance seen by the relay is modelled as interval impedance for each zone of the relay. With interval impedance being known, an upper and a lower bound are obtained for each zone of the relay. Then, the settings of each zone are determined in such a way that at first, perfect selectivity is achieved between different zones of distance relays and second, the sensitivity of each zone is maximized. The sensitivity and the selectivity of the distance relay zones are defined based on the protection philosophy of these zones. The proposed interval method is applied on a sample 8-bus system, and the advantages of the proposed approach in comparison with conventional methods of setting distance relay zones are shown.
    Keywords: Interval Impedance, Sensitivity, Coordination, Distance Relay, Monte-Carlo Simulation
  • Majid Zandi *, A. Payman, J, P. Martin, S. Pierfederici, B. Davat Pages 97-104
    Consideration of the Current-voltage (I-V) characteristics variations of solar modules with temperature and irradiations variations is basic for maximum power point tracking (MPPT). Having a simple and accurate mathematical model for the optimize utilization of the solar modules is essential. In this paper, a novel modeling of photovoltaic systems with novel coefficients is proposed for mathematical description of the current-voltage (I-V) characteristic. Based on the proposed novel temperature and irradiation coefficients, the mathematical modeling of the solar modules is accurate. The accuracy of this proposed model is evaluated through comparison of simulation results to the data provided by experimental tests. The variations of maximum power point parameters (MPPP) versus irradiation and temperature in the experimental tests and the proposed model is evaluated. The proposed model is as well as adaptable for MPPT control operation.
    Keywords: solar system modeling, temperature, irradiation coefficients, DC, DC converter, maximum power point tracking