Nashriyyah -i Muhandisi -i Barq va Muhandisi -i Kampyutar -i Iran: 55 (2)

Open Access Article

1 - Online Estimation of Transient Stability in a Two-Area Power System Based on Local and Wide-Area Measurements
M. Arabzadeh H. Seifi Mohammad Kazem Sheikh El Eslami

20.1001.1.16823745.1396.15.2.1.2

Transient stability analysis (TSA) is one of the important issues in the power system operation. The common methods of TSA are typically based on offline simulations so that some preventive and corrective actions may be designed to be adopted in real time conditions. To More

Transient stability analysis (TSA) is one of the important issues in the power system operation. The common methods of TSA are typically based on offline simulations so that some preventive and corrective actions may be designed to be adopted in real time conditions. To reduce the risk of these actions, in this paper a new method of transient stability estimation is proposed in which both local and wide-area measurements are used. According to the proposed method, the coherent generator groups of the two-area power system are initially identified and then the system is simplified based on the single machine equivalent (SIME) method. Thereafter, the equal area (EA) criterion is used to estimate the system transient stability. The innovation of this paper is the calculation of the acceleration area of SIME system based on the acceleration areas calculated locally in generator buses. The proposed method is applied on a10-mchine 39-bus test system and its results are presented by further explanation of its technical advantages. Manuscript profile

Open Access Article

2 - Speed Control of Matrix Converter-Fed Five-Phase Permanent Magnet Synchronous Motors under Unbalanced Voltages
B. Yousefi S. Soleymani B. Mozafari S. A. Gholamian

20.1001.1.16823745.1396.15.2.2.3

Five-phase permanent magnet synchronous motors (PMSM) are often used for specific applications, in which the precise speed control of the motor by an appropriate driver design is important. The use of three-phase to five-phase matrix converter is a suitable technique fo More

Five-phase permanent magnet synchronous motors (PMSM) are often used for specific applications, in which the precise speed control of the motor by an appropriate driver design is important. The use of three-phase to five-phase matrix converter is a suitable technique for constructing such a motor driver. Since the input voltages of such converters are directly supplied by input three-phase supply voltages, an imbalance in the voltages will cause problems such as unbalanced stator currents and electromagnetic torque fluctuations, making it inefficient to use such converters. In this paper, a new method is proposed to remove torque oscillator factors based on direct power control (DPC). In this way, a number of features including speed, torque, and flux of the motor will improve in terms of the above-mentioned conditions. Simulations are analyzed using Matlab/Simulink software. Manuscript profile

Open Access Article

3 - An Efficient Method for Modulation Recognition of MPSK Signals in Fading Channels
S. Hakimi

20.1001.1.16823745.1396.15.2.3.4

Automatic modulation recognition of digital signals is an essential for intelligent communication systems. Most automatic classifications of digital signal types deal with recognizing signals formats in presence of additive white Gaussian noise (AWGN) in channels. Howev More

Automatic modulation recognition of digital signals is an essential for intelligent communication systems. Most automatic classifications of digital signal types deal with recognizing signals formats in presence of additive white Gaussian noise (AWGN) in channels. However, real world communication environments, such as wireless communication channels, suffer from fading effects. There are few methods proposed to perform in fading channels. This paper presents a high efficient method for identification of M-array phase shift keying (MPSK) digital signal type. The proposed method is heuristic hybrid, formed by a multilayer perceptron (MLP) neural network as the classifier and the bees algorithm (BA) as the optimizer. An equalizer is also used to reduce channel effects. A suitable combination of higher order statistics, up to eighth, is considered as prominent characteristics of signals. Simulation results validate the high efficiency of the proposed technique in recognizing the types of digital signals even at low SNRs. Manuscript profile

Open Access Article

4 - Design and Analysis of a Novel Robust and Fast Sliding-Mode Control with Multi-Slope Sliding Surface for Single-Phase Three Level NPC Inverters under Different Loads and Reduce the Output THD
B. Khajeh-Shalaly G. Shahgholian

20.1001.1.16823745.1396.15.2.4.5

In this paper control structure with robust performance in presence of parametric uncertainties of the converter in order to improve pure sinusoidal inverter in whole functional and loading conditions is rendered. The controller guarantees fast and accurate behavior of More

In this paper control structure with robust performance in presence of parametric uncertainties of the converter in order to improve pure sinusoidal inverter in whole functional and loading conditions is rendered. The controller guarantees fast and accurate behavior of the converter in order to increase the output voltage quality and reduce output harmonics. This controller by sliding performance and utilizing output voltage and capacitor current used in the control process, not only has exact output voltage tracking from reference but also has ability to reject the periodic disturbances due to loading. Also, it guides error states to zero rapidly and makes transient states of the converter as well as possible at error moments that is the same high spikes and loads in output current. Another characteristic of the proposed controller is, improved stability region under wide ranges of loading in different conditions. Accuracy of proposed controller on a single-phase three level NPC inverter which has high sensitivity in control in order to increase quality, decrease harmonics and THD output has been compared with a single-slope sliding mode controller with the sane loading conditions and reference. The simulations results are obtained by MATLAB. Manuscript profile

Open Access Article

5 - An Adaptive Incremental Conductance MPPT Based on BELBIC Controller in Photovoltaic Systems
S. Azimi Sardari B. Mirzaeian Dehkordi M. Niroomand

20.1001.1.16823745.1396.15.2.5.6

Many conventional incremental conductance (INC) methods are applied for maximum power point tracking (MPPT) of photovoltaic arrays. Where, the optimization step size determines the speed of MPPT. Fast tracking could be achieved with bigger increments but the system migh More

Many conventional incremental conductance (INC) methods are applied for maximum power point tracking (MPPT) of photovoltaic arrays. Where, the optimization step size determines the speed of MPPT. Fast tracking could be achieved with bigger increments but the system might not operate properly at the MPP and might become oscillated at this point; therefore, there is a trade-off between the time needed to reach the MPP and the oscillation error. This article is to present an adaptive optimization step size in the INC to improve solar array performance. To adjust the MPP in the photovoltaic (PV) operation point, brain emotional learning based intelligent controller (BELBIC) is applied as an adaptive optimization step size in the INC. This would considerably increase the system's accuracy. The effectiveness of this proposed method is verified by comparing its simulation and experimental results with the conventional methods in different operating conditions. Manuscript profile

Open Access Article

6 - Torque and Flux Ripple Elimination in DTC Control of PMSM Motors using Duty Cycle Control of Voltage Vectors
V. Ghasemian S. A. Gholamian S. M. Mirimani

20.1001.1.16823745.1396.15.2.6.7

This paper presents a novel method for controlling torque and stator flux ripples in DTC control of PMSM motor. In contrast to conventional duty ratio modulation methods which do not pay attention to stator flux condition, the proposed method controls both torque and st More

This paper presents a novel method for controlling torque and stator flux ripples in DTC control of PMSM motor. In contrast to conventional duty ratio modulation methods which do not pay attention to stator flux condition, the proposed method controls both torque and stator flux RMS ripples using minimization of a proper two variable (stator flux and torque) objective function. After realizing that, flux related machine specifications such as circular stator flux vector trajectory and current waveform quality will be developed. For this purpose, in addition to torque dynamics in any DTC control cycle, stator flux dynamics will be studied. Using this, the condition of both torque and stator flux at the end of an applied voltage vector of inverter is predicted. Then, standard deviation of torque RMS ripple and that of stator flux is studied in any control cycle and the normalized sum of these two deviations will be considered as the objective function. Finally, a proper switching instant during any control cycle is calculated for minimizing the objective function. The proposed method is validated by MATLAB simulation. Manuscript profile

Open Access Article

7 - Performance Assessment of a WCDMA Based Radio-over-Fiber System with Near-Far Effect: Uplink Scenario
G. Baghersalimi

20.1001.1.16823745.1396.15.2.7.8

In this research the effect of a radio-over-fiber (RoF) subsystem on the total degradation (TD) performance of uplink wideband code division multiple access (WCDMA) is assessed in the presence of near-far effect. The study considers the use of pilot-aided channel estima More

In this research the effect of a radio-over-fiber (RoF) subsystem on the total degradation (TD) performance of uplink wideband code division multiple access (WCDMA) is assessed in the presence of near-far effect. The study considers the use of pilot-aided channel estimation to neutralize the optical subsystem nonlinearities for different channel conditions, estimation intervals, and near-far factors (NFF). The results demonstrate that the proposed equalization technique almost compensates for the joint impact of the optical subsystem nonlinearity and the near-far effect irrespective of spreading factor, large signal distortion, estimation interval, and user number. Manuscript profile

Open Access Article

8 - A Novel Source/Drain side Double Recessed Gate 4H-SiC MESFET with n-Buried Layer in the Channel
S. M. Razavi Seyed-Hamid Zahiri

20.1001.1.16823745.1396.15.2.8.9

A new structure named as source/drain sides-double recessed gate with N-buried layer in the channel (SDS-DRG) silicon carbide (SiC) based metal semiconductor field effect transistor (MESFET) is presented in this study. Important parameters such as short channel effect, More

A new structure named as source/drain sides-double recessed gate with N-buried layer in the channel (SDS-DRG) silicon carbide (SiC) based metal semiconductor field effect transistor (MESFET) is presented in this study. Important parameters such as short channel effect, maximum DC trans-conductance, drain current and breakdown voltage of the proposed structure are simulated and compared with those of the source side-double recessed gate (SS-DRG) and drain side-double recessed gate (DS-DRG) 4H-SiC MESFETs. Our simulation results reveal that reducing the channel thickness under the gate at the SDS-DRG structure improves the maximum DC trans-conductance and reduces the short channel effects compared to SS-DRG and DS-DRG structures. Reducing the channel thickness under the gate at the drain side of the SDS-DRG structure is used to enhance the breakdown voltage in comparison with the SS-DRG structure. Also, N-buried layer with larger doping concentration in the SDS-DRG structure improves the saturated drain current compared to SS-DRG and DS-DRG structures.‏ Manuscript profile

Open Access Article

9 - A Multi-Frequency Miniaturized Microstrip Fractal Antenna
S. Jam A. Mehboodi

20.1001.1.16823745.1396.15.2.9.0

For further and various applications of communication systems, we lead to using the overall of electromagnetic spectrum. Also, because of the developing f multiband wireless systems, antenna designers are enforced to design antennas matched to the operation in multi-ban More

For further and various applications of communication systems, we lead to using the overall of electromagnetic spectrum. Also, because of the developing f multiband wireless systems, antenna designers are enforced to design antennas matched to the operation in multi-band and multi-frequency. On the other hand, nowadays, the use of light-weight, simple, small and inexpensive antennas is an essential requirement for covering multi bands. In this paper, a microstrip antenna is designed and suggested fractal-based and utilized FR4 substrate with small size and light, and also ability to resonance in multi-frequency by increasing fractal repetitions and self-similarity property. Therefore, this proposed structure causes the antenna resonance in more frequencies, and also leads to miniaturization of its size. This antenna operates in 1-10 GHz range includes five frequency resonance for the most of convenient applications. Also, it has appropriate pattern and circular polarization which increases its applications. The antenna has been fabricated and there is a good agreement between measurement results and full wave simulation using HFSS software.‏ Manuscript profile

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