فصلنامه مهندسی و مدیریت انرژی
سال چهارم شماره 4 (پیاپی 14، زمستان 1393)

In recent years، due to the economical advantages، environmental friendly attribute and renewable generation cycle، the renewable power sources have gained a great attention as a main alternative to traditional power resources. However، as a main deficiency، a renewable power system has low reliability، because of the stochastic and the un-deterministic generation pattern of these resources. In order to obviate the mentioned deficiency، this paper proposes a hybrid renewable generation system with primary sources of wind and photovoltaic generation units، and a fuel cell storage system as a backup unit. Also a power management strategy is proposed to maintain the power balance between the renewable power generation and load power consumption. Moreover، to modify the control system performance and system efficiency، PI controllers are modified by application of a heuristic optimization method، called harmony search algorithm. The simulation study of the proposed hybrid renewable energy system and presented power management strategy is carried out in MATLAB/SIMULINK software framework. The simulation results determine the effectiveness of the proposed solution by increasing the total system efficiency and improving transient behavior of system.

Wind turbine is one of the important electrical power sources which have fastest growth rate among renewable energy sources. Several researchers have had contributions in maximizing power efficiency of wind turbines. To take advantages of linear control technique، this paper is devoted to linear the wind turbine nonlinear dynamics with respect to one parameter. Afterwards a fuzzy T-S model is implemented over linear models. Therefore output of the fuzzy model would be a linear model. This simplification allows using a gain scheduling controller named PDC. This controller is designed based on T-S fuzzy model of the wind turbine to apply appropriate feedback gains corresponding to the wind speed variations. Considering common areas of the wind turbine model and the controller membership functions، in conjunction with LMIs analysis a Lyapunov function is proposed to improve the stability. Finally a comparison is down between PID controller and the article approach.

In this paper، control of doubly fed induction generator (DFIG) for a variable speed wind turbine in stand-alone mode is analyzed and simulated. The purpose of stand-alone mode in this paper is a wind turbine which is assumed without the presence of energy storage systems (ESS) and other distributed generators (DGs). A large number of wind turbines installed in Iran are from 660 kW type and until now in Iran has not been worked on a 660 kW wind turbine with DFIG in stand-alone operation. Therefore، with considering advantages of the DFIG for wind turbine، these researches are important. In this regard، a case study is done on a 660 kW wind turbine of Vestas Company in order to design the desired controlling structures for DFIG in stand-alone mode operation. Also the direct and indirect stator voltage control methods based on vector control are analyzed. Finally، two simulation scenarios are employed to verify the designed controlling structures; these results are analyzed in detail.

Finitude of fossil fuels and its environmental damage is a major challenge to the use of renewable energy sources such as biomass. The world''s largest source of biomass is agricultural residues; in this study، the possibility of using agricultural waste as fuel in the combustion chambers in the Ardabil province has been investigated. The agricultural residues of Ardabil province are studied and finally the wheat and barley straws are selected due to extra production، low nutritious for animals and excess wastes. The samples are used for elemental and ash analysis then compared with allowed limits of the technical and environmental problems. Also the TGA and combustion behavior of sample are analyzed then combustion and kinetics characteristics are calculated. Chlorine and sulfur in both samples are above the allowable level (0. 1 %) leading to corrosion and pollutant emissions، nitrogen content is above the allowable level (0. 7%) and this leads to the nitrogen oxides emission. So it is predicted that both the straws are not acceptable for direct usage as fuel and they need to do some complement processes. Samples of wheat straw in comparison with barley straw has higher comprehensive index of combustion and flammability index and as a result، the peak temperature and the time of maximum combustion rate and the final temperature of combustion is lower but the maximum rate of combustion is more. The activation energy and frequency factor of barley straw has higher than the wheat straw samples at the second combustion stage. Two samples are unsuitable for direct use at combustion process and the preparation procedure is required.

In this paper، a (photovoltaic-wind-battery) hybrid system is designed to provide a network-independent pattern. The purpose of this paper is to provide the necessary energy and minimize production total costs over the life of the system. By using a new algorithm called «particle swarm optimization algorithm with constriction factor»، which has advantages like high convergence speed، the optimal size and minimum cost of these resources are determined. The system’s components optimal size has been studied under various operating conditions using real-time information and meteorological data of one of Iran’s Southern، North West and North East regions. The results show that the «particle swarm optimization algorithm with constriction factor» is more efficient than the «particle swarm optimization algorithm» and ''tabu search''.

In this research، a thermodynamic analysis of a hybrid SOFC/ GT cycle system with ITM technology in order to capture CO2 has been performed. The cycle is designed to supply required power of an Iranian oil platform and its CO2 will be injected into an oil reservoir. At first، the proposed cycle and modeling methodology is introduced and by using EES software coding، the thermodynamic model has been developed. Then، mass، energy and electrochemical balance equations are solved simultaneously. The modeling results show that this cycle has an electrical efficiency of 79. 19% without the CO2 capture and compression system، and while adding the CO2 capture and compression system، the efficiency reduces to 75. 4%. The SOFC، gas turbine and steam turbine shares from power generation of the cycle are 73. 55%، 18. 79% and 7. 67 %، respectively. The specific CO2 production of the cycle is 24. 12% lower than the average of modern combined-cycle gas power plants. Injection of the produced CO2 into the oil reservoir results in extracting of 995 barrels per year of crude oil. Parametric analysis show that by considering the performance restriction of the ITM، the cycle’s working pressure should be as low as possible. According to condition، reservoir structure and recovery coefficient of the Iran’s oil fields، and due to the above-mentioned advantages، application of this technology has been suggested in this research.