فهرست مطالب

Energy Equipment and Systems - Volume:5 Issue:1, 2017
  • Volume:5 Issue:1, 2017
  • تاریخ انتشار: 1396/01/23
  • تعداد عناوین: 6
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  • Mehrdad Makki *, Siroos Hemmati Pages 1-11
    In the permanent magnet linear synchronous motor (PMLSM), force ripple is harmful, useless and disturbing. The force ripple is basically composed of two components: detent force and mutual force ripple. This force is influenced by the geometric parameters of the permanent magnet (PM) motors; such as width, thickness and length of the magnet poles, length and thickness of the rotor and stator, and stator slot shape. For design optimization, the force ripple can be considered as the objective function and geometric parameters can be considered as design variables. In this paper, the distribution of magnetic flux density in the air gap is calculated using an analytical method, then detent force is computed by integrating the Maxwell stress tensor; that is expressed in terms of flux density distribution on the slot face and end face of the iron core of moving parts. The analytical result is compared with FEM simulation to verify the model. The geometric parameter effect on the detent force is investigated. Finally, using genetic algorithm, the optimum design of a linear synchronous motor with minimum detent force is obtained.
    Keywords: Linear Brushless Permanent Magnet Motor, Detent Force, FEM, Analytical Methods, Genetic Algorithm
  • Mostafa Rahnavard, Mohammad Reza Hairi Yazdi, Moosa Ayati * Pages 13-26
    This paper addresses the design of an observer-based fault diagnosis scheme, which is applied to some of the sensors and actuators of a wind turbine benchmark model. The methodology is based on a modified sliding mode observer (SMO) that allows accurate reconstruction of multiple sensor or actuator faults occurring simultaneously. The faults are reconstructed using the equivalent output error injection signal. A well-known validated wind turbine benchmark model, developed by Aalborg University and KK-electronic a/c, is utilized to evaluate the FDD scheme. Different sensors and actuator fault scenarios are simulated in the drive train, generator, and pitch & blade subsystems of the benchmark model, and attempts have been made to estimate these faults via the proposed modified SMO. The simulation results confirm the effectiveness of the proposed diagnosis scheme, and the faults are well detected, isolated, and reconstructed in the presence of the measurement noise.
    Keywords: Wind Turbine, Fault Detection, Sliding Mode Observer
  • Abbas Ketabi, Sahbasadat Rajamand *, Mohammad Shahidehpour Pages 27-41
    Microgrids are nowadays used to produce electric energy with more efficiency and advantage. However, the use of microgrids presents some challenges. One of the main problems of the microgrids widely used in electrical power systems is the control of voltage, frequency and load sharing balance among inverter- based distributed generators (DGs) in islanded mode. Droop method performance degrades when the feeder impedances of two DGs are different and thereby, further modification is required. In this article, a new method based on virtual impedance and compensating voltage is proposed and simulation results show that this method combined with droop control results in balanced power sharing with negligible voltage and frequency drop. Simulation results have been extracted from the Simulink, MATLAB and showed that the proposed method has a good performance in equal load sharing between two DGs with different feeder impedances; both in equal and different droop gains, and with different loads such as nonlinear or unbalanced ones.
    Keywords: Microgrid, Compensating Voltage, Power Sharing, Inverter, Virtual Impedance, Nonlinear-Unbalanced Load
  • Hamed Javaheri Fard, Hamid Reza Najafi *, Hossein Eliasi Pages 43-58
    Hydropower plant and especially micro-hydropower plant is an available, reliable and economical energy source. Micro-hydropower plant is one of the most environment-friendly technology, use and development of which leads to reduction of energy consumption sporadically and worldwide. Along with the growth of these power plants, the issues related to the control of electrical parameters such as load, frequency, voltage and power are also constantly rising. This paper describes the proposed structure of variable speed micro-hydropower plant based on Doubly-Fed Induction Generator. The aim is to control the active and reactive powers for this generator. Here, the proposed controller applied to the generator is predictive power controller that adheres to the principle of predictive strategy. Therefore, in this research, a predictive power controller has been proposed to control active and reactive powers of a DFIG based micro-hydropower plant. The control law is acquired by optimizing a cost function considering the tracking factors. The prediction has been performed on basis of a DFIG model. Finally, the stimulations are carried out by Matlab/Simulink to verify the desired performance of controller.
    Keywords: Rotor Current, Permanent Magnet Synchronous Machine (PMSM), Doubly Fed Induction Generator (DFIG), Predictive Power Controller, Micro-Hydropower Plant
  • Behdad Shadidi, Hossein Haji Agha Alizade *, Barat Ghobadian Pages 59-69
    In internal combustion engines, only about a third of the total fuel input energy is converted into useful work. If the energy rejected into the cooling system and the exhaust gases could be recovered instead and put into useful work, fuel economy would have been substantially improved. The main aim of this research paper was to evaluate the effects of the hybrid nano-catalyst containing cerium oxide and molybdenum oxide in amide-functionalized multiwall carbon nano-tubes (MWCNTs) on the thermal balance of a diesel engine using two types of diesel-biodiesel blends (B5 and B10) in three concentrations (30, 60, and 90 ppm). The research engine was a single-cylinder, four-stroke, direct-injection, and air-cooled diesel engine. The engine was run at two speeds (1,700 rpm and 2,500 rpm) in full load conditions. The thermal efficiency (useful work) resulting from the energy transferred into the cooling system, the exhaust gases, and the unaccounted losses, including the lubricating oil heat loss and the convection and radiation heat transfer, were computed using the first law of thermodynamics. The results showed that by increasing the amount of nano-catalysts (cerium oxide and molybdenum oxide) in fuel blends, the energy transferred to the cooling system and exhaust gases were decreased. The highest reduction in the energy transferred to the cooling system and the exhaust gases was 5.38% and 2.26% for B5, containing 90 ppm (B590ppm), and 5.61% and 2.62% for B10, containing 90 ppm (B1090ppm) respectively. Also, the thermal efficiency went up. Compared with the nano-catalyst-free fuel blends, the highest increase in thermal balance was observed as 6.75% and 5.41% for B590ppm and B1090ppm respectively.
    Keywords: Energy Balance, Nano-Cerium Oxide, Nano-Molybdenum Oxide, Diesel Engine, Biodiesel
  • Seyyed Morteza Mousavi *, Amir Nejat, Farshad Kowsary Pages 71-83
    In the current work, different methods for optimization of turbine blade internal cooling are investigated, to achieve higher cyclic efficiency and output power for a typical gas turbine. A simple two-dimensional model of C3X blade is simulated and validated with available experimental data. The optimization process is performed on this model with two different methods. The first method is a popular method used in previous works with two objectives i.e. the minimization of the maximum temperature and the maximum temperature gradient on the blade. A new method is hereby proposed for optimization of turbine blade cooling, in which the coolant mass flow rate is minimized subject to maximum temperature, and maximum temperature gradient remains lower than certain values. The overall turbine performance is estimated by a simple comparative thermodynamic analysis of the reference design and the representative results obtained from the first and second method of optimization. It is concluded that while the first method of optimization allows higher TIT for a typical turbine, the turbine output power and efficiency could be lower than the reference design, due to high coolant mass flow rate in these candidate points. However, the optimum design point of the second method has higher power output and efficiency compared to all other designs (including reference design) at all values of compressor pressure ratio. It is shown that implementation of the second optimization method can increase the efficiency and the output power of a typical turbine 4.68% and 17% respectively.
    Keywords: Gas Turbine, CFD, Optimization, Genetic Algorithm, Thermodynamic Analysis