فصلنامه مهندسی و مدیریت انرژی
سال پنجم شماره 1 (پیاپی 15، بهار 1394)

By increasing the penetration level of the inverter-based distributed generations (IBDGs) in power system, their fault ride through capability has become one of the essential issues of the new grid codes. This paper proposes a novel method to limit inverter fault currents which are used in DGs. To achieve FRT, interface-inverter operates as a controlled voltage source during normal operation as well as fault condition. The proposed FRT technic employs dc link bridge type non-superconductor fault current limiter (NSFCL) module with capability of controlling the magnitude of the fault current to limit inverter output current during fault condition. At steady state, dc link NSFCL module has not important role on overall IBDG performance. But, at the event of the network fault, by means of this module, it is possible to restrain inverter output currents to a desired value. Also, IBDG is capable to stay connected with the utility at zero grid voltage. The analytical analysis is provided in each switching interval to highlight the impact of the dc link NSFCL on inverter fault current limitation. The effectiveness of proposed scheme is validated through the simulation studies in PSCAD/EMTDC environment.

According to the latest developments in smart grid infrastructures of today’s modern networks, in this paper, end-consumers are presented as a means for participating in distribution networks voltage control. In this regard, for reactive power control of the smart grids, a distributed control approach is proposed as an efficient approach which improves computation burden of the problem, considerably. In the proposed approach, at first, epsilon-decomposition technique is adopted to calculate sensitivities of bus voltage to the injected reactive power. Therefore, buses with strong voltage relation are considered as a region which divides the network to some voltage related regions. Afterwards, candidate buses for reactive power injection are identified for each one of the achieved region. It is noted that, candidate buses of the network are those with reasonably better response to the reactive power injection. Finally, genetic algorithm is applied to obtain optimal reactive power injection of each region. For better evaluation of the proposed distributed reactive power control model, the IEEE 33-bus test system which is commonly used in literature is applied here. Simulation results clearly illustrate the effectiveness of proposed voltage control framework in improving voltage profile of distribution networks.

One of the fundamental problems in developed countries has been a growing need to develop new sources of energy، especially in the transportation sector. This problem is not unique to oil importing countries and oil-producing countries are faced with the problem. Biodiesel is a biofuel that produced from renewable materials such as animal fats and vegetable oil and it can be used in the transport section. Using inexpensive oil such as waste animal feed can produce biodiesel economically justify it. In this study، the production of biodiesel from animal and poultry slaughterhouse waste and optimization of chemical and physical parameters affecting the production of biodiesel was investigated. In this work، transesterification method was used to produce biodiesel. The effects of temperature، molar ratio of alcohol to oil and catalyst were studied and optimum conditions were obtained. In the case of animal waste oil، molar ratio 6:1، 1. 25% of catalyst and Temp = 60 ° C، eventually yield was 93%. In the case of Poultry waste، molar ratio 6:1، 1. 25% of catalyst and Temp = 50 ° C، eventually yield was 85%.

In this study, a dual pressure combined cycle power plant without duct burner for three types of fuel has been investigated. The main objective of this paper is to specify the effect of changing the fuel poperties on cycle performance and finally introducing the best choice. Applying the results, one can see that the highest exergy loss occurs in the combustion chamber and maximum energy and exergy efficiency are obtained via natural gas. Also the results show that in HRSG, the most exergy loss for the three types of fuel occurs at high pressure evaporator. Furthermore the first and second law efficiency for natural gas is 2.34% and 4.69% more than oil fuel. Finally, by comparing the performance parameters of plant, it is concluded that the natural gas is the best fuel and gasoline can be considered as the alternative fuel.

Regarding to the increase of cost and consumption of the nonrenewable energies such as natural gas and electricity, using renewable energies such as solar energy reduces the consumption of nonrenewable energies. In this research, at first, a regenerative organic Rankine cycle with flat plate solar collector as energy source is simulated and the effects of different parameters such as turbine inlet temperature, turbine inlet pressure, condenser temperature, solar collector area, environment temperature and solar radiation intensity on energy and exergy efficiency of system under seven organic fluids are investigated. Finally, system optimization with mentioned parameters is taken related to objective function of energy efficiency and objective function of exergy efficiency. The results of optimization illustrate that between the chosen fluids: R141b, R113, R32, R134a, R12, R717, R290, the highest and lowest performance belong to R113 and R32 respectively.