نشریه مهندسی برق و مهندسی کامپیوتر ایران
سال ششم شماره 3 (پیاپی 15، پاییز 1387)

Precise and practical based economic dispatch is one of the most important problems in power systems. Thus, this paper proposes usage of particle swarm optimization (PSO) algorithm for solving economic dispatch problem. In this study real constraints of economic dispatch problem are considered. For this purpose, it has been considered that the fuel cost function is a non-smooth one. On the other hand, reduction of the pollutants that is emitted from fossil fuel power plants is one of the goals of the optimization problem, so that we fulfill economic and emission dispatch at the same time for solving practical and optimum economic dispatch problem with consideration of many constraints in the operating point and transmission losses, these constraints are included in the proposed method. Finally, simulation results of the proposed method for economic dispatch are compared with those of the other methods such as tabu search, genetic algorithm, and artificial neural network. The results clearly show that the proposed method gives global optimum and fast solution compared to the other methods.

In this paper the model of UPFC is represented by a bilinear equation. Then with the second method of Lyapunov, the input of converter is derived such that the derivative of energy function is negative. The design of controller is carried out with two methods. In the first method, the controller is linearized at operating point. In the second method, the nonlinear method is used in the series converter and the PI controller is used in the shunt converter. Reduction of first swing peak after fault clearing is the main advantage of designed controller with respect of PI controller.

In spite of improvement of the AC drive systems still the DC drives are widely used in industry. One of the problems associated with control of DC motor which might cause unsuccessful attempts for designing a proper controller would be the time-varying nature of DC motors parameters and variables which might be changed while working with the motion systems. In these conditions, the control system will not response properly. One of the best suggested solutions to overcome this problem would be the use of sliding mode control (SMC). SMC is not sensitive to parameters changes and yet would have a fair response to the systems variations. However, SMC suffers from some deficiencies including inflexibility in controller parameters. A Better response can be achieved by SMC in compare with classical methods but it is not the most optimized response. The fair solution can be defined through faster fulfillment of target, less overshoot and more consistency of the system against the changes of the parameters. In this paper, a new fuzzy based method is presented to increase the SMC ability to reach a more convenient solution. Optimized response can be achieved in terms of shorter settling time, less overshoot, and more stability.

This paper, presents a new approach for bidding strategy in spot electricity markets. A two-level optimization method is used for profit maximization of non-cooperative firms, while taking into account overall system constrains. In this approach, the market equilibrium points are determined as Nash Equilibria. In order to capture the behavior of all market participants and therefore, a much more competitive environment both the suppliers and consumers are considered as the players of the market. To avoid local maxima solutions, Genetic Algorithm based optimization is incorporated. The proposed method has been applied to IEEE 9 bus system with satisfactory results.

Voltage flicker and harmonics are the power quality problems which are introduced to the power system as a result of behavior of the arc furnace operation.To analyze harmonic and flicker generated by an arc furnace, accurate arc furnace models are needed. In this paper, different arc furnace models with different level of complexity are reviewed.In the first part of this paper a new developed time domain static model based on a piece-wise linear approximation of the V-I characteristics of the arc furnace is presented.In the second part of the paper, dynamic model for an arc furnace using MATLAB (Simulink) is presented. In addition to this, the novelty of this simulation technique lies in the fact that the variation of power transmitted to the load by the arc furnace during the cycle of operation is considered, thus making the proposed model more accurate and dependent on the operating conditions of the load.Finally recommendations are made for the application of some of these models and the accuracy of the presented model to other models from the practical point of view by using MATLAB is shown.

Moments are utilized in image processing for pattern recognition, machine vision and numerous feature extraction techniques. Due to computational complexity, it is difficult to use high order moments in real time processing. This paper presents the design of two new architectures for real time computation of moments, up to order 14, M00 to M77, in gray level images, based on parallel systolic arrays and pipelining technique, using a 0.18μm CMOS technology.Implementation of the moment processing element (MPE) of the first architecture illustrates a processing speed of 125 frames/s for 1024×1024 grey-level images. The maximum operating frequency and the power consumption for an architecture with 5 elements is 133 MHz and 14.36 mW, respectively. Since the design is very low power, the number of parallel MPE’s can be easily increased. Simulation shows that with 11 parallel MPE’s, the first 49 moments of 1024×1024 image are computed with the speed of 30 frames/sec.To further decrease the latency of the first architecture, the second architecture is proposed, in which the add operation is performed only with a single adder and a compressor. Simulation shows that the latency of the second architecture is 3.3 times lower than that of the first architecture. Implementation of the second architecture illustrates the maximum operating frequency and the power consumption of 125 MHz and 58.34 mW, respectively. Operating frequency and power consumption of the second architecture is approximately the same as that of the first architecture which befit real time applications.

In this paper, we proposed a new method for speech enhancement. The method is based on wavelet spectral subtraction. We use linear predictive coding (LPC) for noise estimation and extraction. The proposed method was compared with the wavelet spectral subtraction method. The new method increased signal to noise ratio of the noise contaminated speech signal more than wavelet spectral subtraction method. Also, good results have been achieved in auditory test (Mean Opinion Score).

To simulate the effects of rain on the wave propagation, refractive index, size, and pattern of the rain drops should be characterized. By finding these parameters through the measurements, one is able to calculate scattering parameters from a particle and then extend it to a group of particles. In this study, attenuation, polarization changes, and phase shift are calculated by considering rainfall distribution and moment method. Based on the comparison of the simulation results and ITU recommendations, it is shown that ITU recommendations model is general and approximately presents average attenuation.

Ultrasonography is one of the most useful diagnostic tools for human soft tissue and is one of the methods that are in routine use for distinguishing benign and malignant breast tumors. But its diagnosis is operator dependent. In previous researches texture analysis for solid breast mass classification is used. In those works texture features of the tumor are used, but sonologists notice to the features of the surrounding area of the tumors for their diagnosis. In this research as well as the morphological features of the mass the features of the surrounding area of the mass are also considered. MLP neural network is used for classification. 36 breast sonography images are used that 18 of them proved to be benign and 18 of them proved to be malignant through biopsy. The features are used in different combinations and it is shown that using the texture features of behind the tumor area and the same depth near the tumor provide meaningful result and also compensate the different adjustments of the systems.