Research Articles
Power systems
Sirus Salehimehr; Behrooz Taheri; Seyed Amir Hosseini; Hossein Askarian Abyaneh; Farzad Razavi
Abstract
In this paper, a new method based on Hilbert transform is proposed to detect the power swing and faults occurring during the power swing. The proposed method operates independently from the system parameters. As well as, this method has the ability to detect different types of power swings, including ...
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In this paper, a new method based on Hilbert transform is proposed to detect the power swing and faults occurring during the power swing. The proposed method operates independently from the system parameters. As well as, this method has the ability to detect different types of power swings, including stable, unstable, and multi-mode power swings, and also can differentiate the power swing from the faults for blocking or unblocking the distance relay. In order to evaluate the proposed method, various types of power swing and simultaneous faults are simulated in DIgSILENT software and then using the obtained matrix data from the current signals, the proposed algorithm has been implemented in Matlab software using the Hilbert transform. The results of this study show that the proposed method can detect different types of power swing successfully. In addition, it has been shown that the proposed method operates very fast; besides when a fault occurs simultaneously with the power swing unblocks the relay as soon as possible. This method has been also implemented practically on a distance relay and is tested by a relay tester device made by Vebko Amirkabir knowledge-based company. The results obviously show that the proposed method has a better operation than industrial conventional methods.
Research Articles
Control
Mostafa Rahideh; Abbas Ketabi; Abolfazl Halvaei Niasar
Abstract
In this paper, an adaptive control method is proposed for maximum power point tracking (MPPT) in photovoltaic (PV) systems. For improving the performance of an MPPT, this study develops a two-level adaptive control structure that can decrease difficulty in system control and efficiently handle the uncertainties ...
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In this paper, an adaptive control method is proposed for maximum power point tracking (MPPT) in photovoltaic (PV) systems. For improving the performance of an MPPT, this study develops a two-level adaptive control structure that can decrease difficulty in system control and efficiently handle the uncertainties and perturbations in the PV systems and the environment. The first control level is a ripple correlation control (RCC), and the second level is a model reference adaptive control (MRAC). This paper emphasizes mainly on designing the MRAC algorithm, which improves the underdamped dynamic response of the PV system. The original state-space equation of PV system is time-varying and nonlinear, and its step response contains oscillatory transients that damp slowly. Using the extended state-dependent Riccati equation (ESDRE) approach, an optimal law of the controller is derived for the MRAC system to remove the underdamped modes in PV systems. A algorithm of scanning the P-V curve of the PV array is proposed to seek the global maximum power point (GMPP) in the partial shading conditions (PSCs). It is shown that the proposed control algorithm enables the system to converge to the maximum power point in milliseconds in partial shading conditions .
Research Articles
Control
fahimeh akhavan ghassabzadeh; Samaneh Soradi zeid
Abstract
Due to the easy adaption of radial basis functions (RBFs), a directRBF collocation method is considered to develop an approximate scheme to solvefractional delay differential equations (FDDEs). The method of RBFs is a method of scattered data interpolation that has many application in different fields. ...
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Due to the easy adaption of radial basis functions (RBFs), a directRBF collocation method is considered to develop an approximate scheme to solvefractional delay differential equations (FDDEs). The method of RBFs is a method of scattered data interpolation that has many application in different fields. In spite of easy implementation of other high-order methods and finite difference schemes for solving a problem of fractional order derivatives, the challenge of these methods is their limited accuracy, locality, complexity and high cost of computing in discretization of the fractional terms, which suggest that global scheme such as RBFs that are more accurate way for discretizing fractional calculus and would allow us to remove the ill-conditioning of the system of discrete equations. Applications to a variety ofproblems confirm that the proposed method is slightly more efficient than thoseintroduced in other literature and the convergence rate of our approach is high.
Research Articles
Optimization
Milad Niaz Azari; Vasiye Lohrasbi; Seyed Abdolah Mousavi
Abstract
Today, with the high promotion of technology and the expansion of industries, electric motors are used extensively and consume a large part of the electrical energy produced by power plants. Therefore, researchers and experts have always sought solutions to make electric motors with high reliability ...
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Today, with the high promotion of technology and the expansion of industries, electric motors are used extensively and consume a large part of the electrical energy produced by power plants. Therefore, researchers and experts have always sought solutions to make electric motors with high reliability and low losses. The machines are made of a high temperature superconducting motor with high efficiency are called high temperature superconductor -induction synchronous motor (HTS-ISM). In this paper, the high-temperature superconducting induction/synchronous motor (HTS-ISM) is studied. Optimizing of torque density and the structural dimensions of HTS-ISM is done using one of the newest optimization methods, the collective decision optimization algorithm (CDOA). The results show a torque of about 51.75% increase via the optimization process. Also commonly used optimization method, particle swarm optimization algorithm (PSO) method was implemented to compare the results. The comparison has proved that the CDOA method high capability to optimize the motor design parameters. All of the algorithms in this paper is performed with MATLAB software.
Research Articles
Control
Amin Karimi; YousefReza Jafarian; Hassan Bevrani; Rahmatollah Mirzaei
Abstract
The use of renewable energy sources in microgrids has grown dramatically in recent years. The absence of a rotational mass in these microgrids and their interfaces leads to a lack of inertia and consequently, frequency and voltage instability. To cope with these dilemmas, the virtual synchronous generator ...
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The use of renewable energy sources in microgrids has grown dramatically in recent years. The absence of a rotational mass in these microgrids and their interfaces leads to a lack of inertia and consequently, frequency and voltage instability. To cope with these dilemmas, the virtual synchronous generator (VSG) has been introduced as an effective solution. This paper first focuses on modeling a VSG using basic electrical equations. It, then, proffers a transient fuzzy controller augmented on virtual inertia’s topology. Inspired by the FACTS’ performance, the privileged specifications such as STATCOM fluctuation damping ability for major perturbations at transient times are appended to the VSG scheme by a fuzzy controller. This controller is implemented with a feedback from the system voltage angle and its derivative, as well as in frequency and its derivative. The modified coefficients of both active and reactive powers are outputs of the fuzzy system. Using the proposed fuzzy controller, the transient response of VSG-based microgrids is improved. Simplicity and ability to improve the transient response are the principal specifications of the proposed configuration. Simulation results confirm the improvement of the presented method by the introduced augmented VSG control mechanism.
Research Articles
Power systems
Mehdi Bekrani; Mojtaba Heydari; Seyedeh Tahereh Behrooz
Abstract
In this paper, a new adaptive control method is proposed for direct matrix converters. The proposed method uses interval type-2 fuzzy logic integrated with sliding mode control. Employing the sliding mode control in matrix converters leads to an efficient choice of switching combinations and a reliable ...
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In this paper, a new adaptive control method is proposed for direct matrix converters. The proposed method uses interval type-2 fuzzy logic integrated with sliding mode control. Employing the sliding mode control in matrix converters leads to an efficient choice of switching combinations and a reliable reference tracking. The main problem of the sliding mode control is the chattering phenomenon that degrades the controller performance through injecting high-frequency variations in the controller variables. The proposed method incorporates the interval type-2 fuzzy with the sliding mode control to mitigate the chattering problem. The sliding mode switch surface can be adjusted adaptively according to the system state and the proposed fuzzy compensation based on the Lyapunov stability theorem, so that the control system has the characteristics of low chattering effect and appropriate operation quality. Comprehensive evaluations of the waveforms are conducted for the new matrix converter through various simulations. Simulation results verify the effectiveness of the proposed adaptive control method for matrix converter in various conditions, and its superiority in chattering suppression in comparison to the conventional sliding mode control and the boundary layer method.
Research Articles
Optimization
sadegh kalantari; mehdi ramezani; ali madadi
Abstract
This paper aimed to formulate image noise reduction as an optimization problem and denoise the target image using matrix low rank approximation. Considering the fact that the smaller pieces of an image are more similar (more dependent) in natural images; therefore, it is more logical to use low rank ...
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This paper aimed to formulate image noise reduction as an optimization problem and denoise the target image using matrix low rank approximation. Considering the fact that the smaller pieces of an image are more similar (more dependent) in natural images; therefore, it is more logical to use low rank approximation on smaller pieces of the image. In the proposed method, the image corrupted with AWGN (Additive White Gaussian Noise) is locally denoised, and the optimization problem of low rank approximation is solved on all fixed-size patches (Windows with pixels needing to be processed). This method can be implemented in parallelly for practical purposes, because it can simultaneously handle different image patches. This is one of the advantages of this method. In all noise reduction methods, the two factors, namely the amount of the noise removed from the image and the preservation of the edges (vital details), are very important. In the proposed method, all the new ideas including the use of TI image (Training Image) and SVD adaptive basis, iterability of the algorithm and patch labeling have all been proved efficient in producing sharper images, good edge preservation and acceptable speed compared to the state-of-the-art denoising methods.
Research Articles
Optimization
Hassan Farokhi Moghadam; Nastaran Vasegh; Seyed Mohsen Seyed Moosavi
Abstract
In this paper, an adaptive repetitive controller (ARC) is proposed to reject periodic disturbance with an unknown period. First, a repetitive controller is designed when the disturbance period is known. In this case, the RC time delay is equal to the period of disturbance. Then, the closed-loop system ...
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In this paper, an adaptive repetitive controller (ARC) is proposed to reject periodic disturbance with an unknown period. First, a repetitive controller is designed when the disturbance period is known. In this case, the RC time delay is equal to the period of disturbance. Then, the closed-loop system with the RC controller is analyzed and the effect of RC gain, k, is studied analytically. It is shown that by increasing k, the steady-state error is reduced. It is dependent on the speed of the response convergence. Secondly, an adaptive fast Fourier transform (AFFT) algorithm is proposed to extract the accurate period of disturbance adaptively. Simulation results show that the period is converged to its true value even though varying the period. Also, simulation results about the effect of controller gain are in good agreement with analytical results. Finally, it is shown that the proposed method can decrease the amplitude and energy of output signal significantly.
Research Articles
Electronics
alireza shamsi
Abstract
This paper proposes a new mismatch cancelation technique for quadrature delta-sigma modulators (QDSM). In this approach, a high speed and simple structure dynamic element matching (DEM) based on homogenization and time-division (HTD) is designed. In addition, I and Q digital-to-analog converters (DACs) ...
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This paper proposes a new mismatch cancelation technique for quadrature delta-sigma modulators (QDSM). In this approach, a high speed and simple structure dynamic element matching (DEM) based on homogenization and time-division (HTD) is designed. In addition, I and Q digital-to-analog converters (DACs) are merged into one complex DAC (C_DAC) for quadrature mismatch cancelation which leads to near-perfect I/Q balance. A third-order multi-bit continuous-time (CT) QDSM for a WCDMA LOW-IF receiver is designed and implemented in 180 nm CMOS technology to investigate the effects of the proposed DEM. The proposed DEM method and DWA algorithm are applied to the QDSM with 2% mismatch errors in DAC cells and compared two outputs PSD effects. Simulation results show that the modulator achieves a signal-to-noise ratio (SNR) of 74 dB and 74.2 dB for the proposed method and DWA, respectively, while the proposed method is simpler and faster than the data weighted averaging (DWA) algorithm.
Research Articles
Electronics
Hamideh Dashti
Abstract
In this paper, for the first time, effects of external electromagnetic fields on a coplanar waveguide (CPW) are numerically studied by means of the method of finite elements. Two CPW lines with different geometry and dielectric substrate permittivity are considered. Both lines have characteristic impedance ...
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In this paper, for the first time, effects of external electromagnetic fields on a coplanar waveguide (CPW) are numerically studied by means of the method of finite elements. Two CPW lines with different geometry and dielectric substrate permittivity are considered. Both lines have characteristic impedance of 50 Ω. Induced electric and magnetic fields on the two CPW lines are analyzed by illuminating the structure with a plane wave. The uniform plane wave with fixed frequency at 3 GHz is considered as the incident field. The influences of the incidence angle and dielectric substrate permittivity are investigated. For this purpose, two incidence planes are considered and, for each case, two polarizations, parallel and perpendicular, for incidence electric field relative to incidence planes are studied. According to the results, for the two CPW lines terminated with their characteristic impedance at both ends and the incident plane wave with electric-field intensity of 1 V/m at f = 3 GHz with incidence angles of 22.5Ëš and 45Ëš, maximum peaks of the induced field occur and also, depending on the incidence plane, incidence angle and E-field polarization, even or odd quasi-TEM mode of the CPW line can be propagated.
