مهندسی برق مجلسی
سال:1387 | دوره:1 | شماره:4 |تعداد مقالات:19

The integration of Distributed Energy Resources (DER) in power systems can provide the opportunity to supply electricity to customers more efficiently and effectively. The DER includes Distributed Generation (DG) and Demand Side Management (DSM). In a smart grid incorporating automated control and distributed energy systems an effective DSM can alleviate the peak load and shift part of the demand to off-peak hours. The aim of this research is to assess the impact of the DG and the DSM on reliability of the smart distribution system by analyzing different case studies. Roy Billinton test system RBTS Bus2 is used to validate case studies which are performed as a part of this paper. For more practical considerations, a modification of the RBTS Bus2 model is developed to assess the system reliability

Recently, the renewable resources such as wind farms assumed more attraction due to their features of being clean, no dependency to any type of fuel and having a low marginal cost. The output power of wind units is dependent on the wind speed which has a volatile and intermittent nature. This fact confronts the solution of unit commitment problem with some challenges when a huge amount of wind resources is penetrated and considerable uncertainties are included in the problem. Moreover, the demand of the system has some volatility in comparison with forecasted values. This kind of volatility and stochastic nature is another source of uncertainty in the power system. In this paper, thermal and wind units are incorporated and the optimization problem is solved by the employment of proper probability distribution function and the Monte Carlo simulation approach for dealing with uncertainties. Afterwards, the optimization problem is solved by the use of the binary form of gray wolf optimization algorithm and the minimized total cost will be obtained. Ultimately, the unit commitment schedule and optimal generation of each unit are determined and the optimization results are compared with the solution of genetic algorithm and particle swarm algorithm.

Due to the specific nature and various limitations in the architecture and resources of mobile wireless networks, AD HOC networks are highly challenging and risky in terms of quality spheres and maintaining such systems. Opportunistic routing provides the opportunity to improve these issues and enhance the network performance appropriately. Meanwhile, due to unspecified exchange routes in this strategy, it is more difficult to support the quality of routing. In this type of routing, decision-making and candidate prioritization are done based on a criterion named “ opportunism” in such a way that this method of prioritization and selection leads to increased instability in intermediate routes. Accordingly, in order to improve this issue, this research introduces a new routing protocol, named “ QoS-Aware and Stable Opportunistic Routing Protocol (QSORP)” . The QSORP is a three-stage protocol that is based on the performance of its stages, this protocol tries to provide quality together with stability in opportunistic routing, depending on the necessities and requirements of this type of routing. The QSORP protocol supports the capability of reducing the complexity of candidate management in addition to effectively support the quality and stability of links. In order to evaluate the QSORP’ s performance and efficiency, this protocol is simulated using the OPNET simulator and then the protocol is compared with two other protocols; ORAC and QEOR. The simulation results indicated the superiority of the proposed protocol based on the following criteria: unstable intermediate routes, the rate of the received data, and network throughput.

This paper presents indirect field-oriented control method for two-level inverter FED induction motor. This research paper offers a simple switching strategy to provide optimized output torque, speed regulation and also, less switching losses. In addition to enabling fast torque and speed response, this study also offers constant switching frequency. Conventional Hysteresis current controller has two main drawbacks; the first one is the variation of the switching frequency and the second one is more harmonics in motor currents. The aim of the present paper is to describe a novel switching technique, optimal controller, with the smallest possible tracking error and fixed switching frequency. Modeling and simulation of the proposed method are carried out using MATLAB/SIMULINK.

This paper presents a study on the four-leg VSI based distribution static compensator (D-STATCOM) for compensation of neutral, source & PCC current harmonic distortion, PCC voltage regulation and compensation of unbalanced in current waveform. This solution could be used for three-phase four-wire nonlinear and unbalanced load medium voltage distribution system. The proposed control algorithm is developed based on synchronous reference frame theory with the PI controller. The obtained reference current signal from control algorithm is compared in hysteresis band current controller for a better switching of the D-STATCOM. The performance of the system with implementing the D-STATCOM is also analyzed and compared. The proposed control method is implemented on 11/0. 4kv medium voltage distribution system and provided effective compensation for reactive power and harmonic distortion mitigation. The simulation results are obtained using MATLAB/SIMULINK.

In this paper,the economic dispatch problem in combined AC-DC systems is studied based on the equivalent losses matrix of power flow.The proposed method starts with calculation of the power flow for the combined AC-DC system,and continues with the calculation of the losses matrix.Afterwards,the economic dispatch problem is calculated by the interior point method.The active powers which are founded by the economic dispatch problem,are used to recalculate the new power flow.The procedure will be iterated until the results convergence.Finally,several simulations carried out on a 14-bus system including five generation units,with and without DC links.

It is well-known that the stator Inter-Turn Short Circuit (ITSC) fault detection in vector-controlled Induction Motor (IM) is a very difficult task so far. This is due to the various problems encountered in diagnostic processes resulting from the speed variation and its influence on electrical signals. As a solution, this paper proposes an approach based on the Vold-Kalman Filter Order Tracking (VKF-OT) technique. To this end, stator phase current, quadrature current and rotational speed were monitored at various speeds with and without fault (i. e. healthy and with the ITSC fault) in the Field oriented control (FOC) IM drive. The VKF-OT technique was applied to the monitored currents in order to track the related harmonic components fault, the results are compared to the classical Fourier analysis (FFT). The obtained results proved that the presented approach is more efficient than the FFT technique, especially when the IM is operating under non-stationary speed conditions.

The purpose of this research is to study and select the type of engine and circuits for connecting their windings in the generator operating mode of the electric machine unit for the device of converting kinetic and mechanical energy of rotation in the electric one. The design and principle of the device, which transforms the kinetic energy from pressure into an electric one, is proposed. The results of experimental studies on the determination of the most efficient type of electric engine in accordance with the value of the generated power output are presented. According to the results of the experiments, it was determined that a stepper motor DSh 200-1 is more efficient for one rotation in the forward and reverse direction with frequency f = 1. 185 Hz. The processing of experimental research was carried out using integral methods of mathematical physics, namely the trapezoid method. Integration of the received oscillograms allowed to determine the most effective circuit of connection of stepper motor DSh-200-1 stator windings. For one rotation in the forward and reverse direction with frequency f = 1. 185 Hz, the given circuit will provide the power of 0. 164 Watt.

This paper presents a wide tuning range, and low noise voltage controlled oscillator (VCO) based on cross-coupled and colpitts structures. The advantages of this work provide a low-phase noise and robust start-up condition, leading to minimized the dc power. In addition, a new structure of the capacitor bank is used in this structure to achieve a wide range of frequency. The proposed circuit is simulated in 0. 18 μ m CMOS process. The designed VCO covers the frequency range of 21. 95 GHz to 24 GHz with a tuning range of 8. 9%. Simulation results show that the phase noise is-120. 5 dBc/Hz at 1MHz offset frequency for 23GHz carrier frequency. Also, power consumption of the VCO is 6. 34 mW under 1. 8 supply voltage, and the figure-of-merit is-191. 68 dBc/Hz.

This review paper contains the discussion about performance analysis of high speed 4-2 compressor architectures, starting from the general idea; conventional form for implementation of this building block along with its truth table has been studied. Thereafter, the modified versions which show promise for high speed multiplier implementations along with their benefits and drawbacks were demonstrated and comprehensively analyzed. Following the same principles, an optimized structure for the 4-2 compressor is obtained which has 2 XOR gate level delay for the critical path and contains the least delay among the reported works. As another advantage, because of uniform paths the output waveforms will be free of any glitches. Simulation results for TSMC 0. 18 μ m CMOS technology and 1. 8V power supply using HSPICE have been provided to show the superiority of our designed architecture in terms of the speed performance. Finally, to confirm the correct behavior of proposed compressor, an 8x8 bit multiplier was designed which can operate at the frequency of 500MHz without employing any special multiplication algorithm for partial product generation.