Sharif Digital Repository

This study presents the application of the doubly fed induction generator (DFIG) to reduce the frequency deviation and improve frequency of a power system. This has been done by proposing a wind turbine model and a new fuzzy controller. The fuzzy controller has been suggested to change the speed of the wind turbine rotor and modify the impacts of wind speed fluctuations on the output power. The fuzzy controller parameters are optimized using the genetic algorithm (GA) to achieve the appropriate transient response. A smart controller is combined with fuzzy controller to optimize the usage of wind turbine’s kinetic energy. Furthermore, the DFIG with the proposed controller participates in the... 

AC/DC/AC converters are widely being used in a variety of power applications. Continuity of service of these systems, as well as their reliability and performance are now of the major concerns. Indeed, the failure of the converter can lead to the total or partial loss of the control of the phase currents and can cause serious system malfunction or even shutdown. Thus, uncompensated faults can quickly endanger the system. Therefore, to prevent the spread of the fault to the other system components and to ensure continuity of service, fault tolerant converter topologies associated with quick and effective fault detection and compensation methods must be implemented. In this thesis, the... 

Nowdays, the world’s need for energy from renewable sources is increasing due to the excessive use of non - renewable resources and the pollution of the environment. Energy converters are classified into three general types: electromagnetic, electrostatic, and piezoelectric, in which piezoelectric materials are used in converters that convert mechanical energy into electrical energy (and vice versa). In the last decade there has been extensive research into the use of these materials for self-charging of low consumption electrically-powered devices such as sensors. For this purpose, in this study, a new method for harvesting electrical energy from the sea using piezoelectric elements is... 

The ocean thermal energy conversion system is one of a variety of renewable marine energy that is made up of a thermodynamic cycle, and it uses the difference between the temperature of hot water at the ocean surface and cold water at the depths of the ocean to generate electricity. The closed cycle is one type in which the system uses a working fluid which its boiling point less than the boiling point of water. Increasing the temperature of the fluid inlet in the cycle increases the system efficiency, which has been applied in this study to increase the efficiency of the OTEC system. The required energy to increase this temperature has been achieved by adding a solar collector to this... 

Today, due to increasing electricity consumption and demand, the use of conventional systems such as thermal, hydro and nuclear power plants is not enough to convert energy. Over the past century, scientists have sought to discover new technologies for exploiting different forms of energy and converting them into high-efficiency electrical energy. One of these ways is to use the phenomenon of magnetohydrodynamics (magnetic fluid dynamics) to convert thermal energy directly into electrical energy. Magnetohydrodynamics is a theoretical field that studies the dynamics of fluids with electrical conductivity. Induction magneto-hydrodynamic generators use ionized hot plasma (a quasi-neutral gas of... 

Nuclear batteries have been attractive since the beginning of the twentieth century due to their longer life in comparison with other types of batteries. These batteries are produced in different types with different efficiencies depending on the method used to convert their energy. In this study, due to the lack of the resources in the country to study the types of nuclear batteries, first we did an overview of the classification and operation of different types of nuclear batteries, especially on the latest type of nuclear batteries, PIDEC, that has not been studied in the country so far. The most important feature of a PIDEC is that it has an intermediate stage to transmit the maximum... 

In this research, the feasibility of the usage of the Wells turbine for direct conversion of the hydro-mechanical energy of the surface waves is studied via analytical and numerical methodologies. The results produced, showed for the first time that the Wells turbine can be employed for such waves directly and the performance variables are quite reasonable and even efficient considering low cost of HKWT system and abundant availability of those waves. For the low-frequency waves, the turbine is tested for different wave velocities to discover the best angular velocity of the rotor in terms of performance and the rotational velocity of 300 RPM has been found to be the optimum amount. Further,... 

The energy systems efficiency is a great issue confront power plants professionals. Besides using high-tech components in power plants, plant operation optimization can significantly improve energy efficiency and economic performance, as efficiency of plant components generally depends on operating conditions. In addition, system preventive maintenance can reduce plant operation and failure costs, however it is also costly when done frequently. Therefore, optimizing operating conditions and preventive maintenance intervals can minimize the expected total cost of plant due to operation, failures and preventive maintenances. In recent years, the use of optimization models to determine plant... 

Along with the development of social and economical development and expansion of urban areas the rate of municipal solid waste (MSW) generation has been increased. Waste-to-Energy technologies consist of any waste treatment process that enables generating energy from a waste source. In recent years many studies have shown that plasma gasification has a considerable potential as an effective method for solid waste treatment and energy recovery. Plasma gasification converts MSW to a clean syngas and its application could reduce MSW volume and the environmental risks of waste landfill. In the present study the methods of waste conversion to energy has been reviewed, then plasma gasification of... 

Traditionally, different energy carriers are operated and planned independently. In recent years, with the growth of technology, communication has increased between different energy carrier-systems, in particular within electricity and natural gas networks. The attention to the links between various energy carriers has led to the formation of a new concept called the Energy Hub (EH). In this research, the problem of capacity development planning for gas power plant, CHP and boiler has been studied in a specified time horizon for several energy hubs, so as to meet the demand for electrical and thermal energy. It is worthy to note that the development of electricity and natural gas... 

As a long-established approach, the electricity and natural gas networks have been operated and planned independently. Nevertheless, in recent years there has been a significant progress in energy conversion technologies in microgrids, thus making the electricity and gas networks more connected on the costumers’ side and also enabling users to utilize each of the carriers interchangeably. This increasing correlation between the two networks has led us to a new approach called co-planning of electricity and natural gas networks.This thesis aimed to take a closer look at this new approach and tried to study different aspects of it. Based on the concept of useful energy, a new approach has been...