Showing 103 results for Ali
S. Sivasakthi, R. K. Santhi, N. Murali Krishnan, S. Ganesan, S. Subramanian,
Volume 13, Issue 2 (June 2017)
Abstract
The increasing concern of global climate changes, the promotion of renewable energy sources, primarily wind generation, is a welcome move to reduce the pollutant emissions from conventional power plants. Integration of wind power generation with the existing power network is an emerging research field. This paper presents a meta-heuristic algorithm based approach to determine the feasible dispatch solution for wind integrated thermal power system. The Unit Commitment (UC) process aims to identify the best feasible generation scheme of the committed units such that the overall generation cost is reduced, when subjected to a variety of constraints at each time interval. As the UC formulation involves many variables and system and operational constraints, identifying the best solution is still a research task. Nowadays, it is inevitable to include power system reliability issues in operation strategy. The generator failure and malfunction are the prime influencing factor for reliability issues hence they have considered in UC formulation of wind integrated thermal power system. The modern evolutionary algorithm known as Grey Wolf Optimization (GWO) algorithm is applied to solve the intended UC problem. The potential of the GWO algorithm is validated by the standard test systems. Besides, the ramp rate limits are also incorporated in the UC formulation. The simulation results reveal that the GWO algorithm has the capability of obtaining economical resolutions with good solution quality.
G. Alipoor,
Volume 13, Issue 4 (December 2017)
Abstract
Performance of the linear models, widely used within the framework of adaptive line enhancement (ALE), deteriorates dramatically in the presence of non-Gaussian noises. On the other hand, adaptive implementation of nonlinear models, e.g. the Volterra filters, suffers from the severe problems of large number of parameters and slow convergence. Nonetheless, kernel methods are emerging solutions that can tackle these problems by nonlinearly mapping the original input space to the reproducing kernel Hilbert spaces. The aim of the current paper is to exploit kernel adaptive filters within the ALE structure for speech signal enhancement. Performance of these nonlinear algorithms is compared with that of their linear as well as nonlinear Volterra counterparts, in the presence of various types of noises. Simulation results show that the kernel LMS algorithm, as compared to its counterparts, leads to a higher improvement in the quality of the enhanced speech. This improvement is more significant for non-Gaussian noises.
E. Alizadeh, A. Motie Birjandi, M. Hamzeh,
Volume 13, Issue 4 (December 2017)
Abstract
This paper proposes a decentralized control technique to minimize the total operation cost of a DC microgrid in both grid-connected and islanded modes. In this study, a cost-based droop control scheme based on the hourly bids of all participant distributed generators (DGs) and the hourly energy price of the utility is presented. An economic power sharing technique among various types of DG units is adopted to appropriately minimize the daily total operation cost of DC microgrid without a microgrid central controller. The DC microgrid may include non-dispatchable DG units (such as photovoltaic systems) and dispatchable generation units. Unlike other energy management techniques, the proposed method suffers neither from forecasting errors for both load demand and renewable energy power prediction modules, nor from complicated optimization techniques. In the proposed method, all DGs and the utility are classified in a sorting rule based on their hourly bids and open market price, and then the droop parameters are determined. The simulation results are presented to verify the effectiveness of the proposed method using MATLAB/SIMULINK software. The results show that the proposed strategy is able to be implemented in various operation conditions of DC microgrid with resistance to uncertainties.
V. Behnamgol, A. R. Vali, A. Mohammadi,
Volume 14, Issue 3 (September 2018)
Abstract
In this paper, a new guidance law is designed to improve the performance of a homing missiles guidance system in terminal phase. For this purpose first of all, the two dimensions equations of motion are formulated, then the approximation dynamic of missile control loop is added to these equations which are nonlinear whit unmatched uncertainty. Then, a new adaptive back-stepping method is developed in order to control this system. An adaptive term is used in the control law that is converged to the uncertainty. This convergence is proved based on Lyapunov stability theorem. Therefore using this adaptive term in the control law can be eliminated the uncertainty. Based on this algorithm, a new guidance law is designed. Then its performance is compared with common guidance laws in a guidance loop simulation in the presence of control loop dynamics.
A. Fadhil Halihal,
Volume 15, Issue 2 (June 2019)
Abstract
The boiler drum process is a nonlinear, complex and multivariable process which includes significant time delay. Therefore, the control on the water level in the drum is not easy and ideal. The first objective of this paper is to model the drum water level referring to 210 MW power unit for Nassiriyah thermal power plant. The second objective is to study the water level controller operation with its performance investigation. Firstly, the drum water level process has been modelled based on first principles by two models: the proposed simplified linearized model and the complicated nonlinear model. Then, a comparison between the extracted practical plant data and the water level results simulated by the two models demonstrate the validity of both models with very good approximations. Secondly, Proportional Integral (PI) controller based on three element water level control strategy and used in this plant, has been described and simulated by MATLAB/Simulink. The controller parameters have been selected according to practical considerations. These considerations are minimizing as possible, a number of the close and open commands to the feedwater flow control valve to extend its lifetime with maintaining the drum water level on a set point. The controller has been tested to evaluate its performance for different values of proportional gain (Kp), integral gain (Ti), gain of steam flow signal (Gx2), and gain of mass feedwater flow signal (Gx3). Firstly, the results show that selection of Kp is difficult because of the tradeoff between fast dynamic response and steady state performance. Secondly, the results show selection of Ti affects only steady state performance. Finally, the results show that selection of Gx2 and Gx3 plays an important role in stability of the drum water level.
H. Rajabalipanah, M. Fallah, A. Abdolali,
Volume 15, Issue 2 (June 2019)
Abstract
An intelligent design method of double screen frequency selective surfaces (FSSs) is addressed in this paper. The employed unit cell is composed of two metallic screens, which are printed on both sides of a substrate. The presented non-trial-and-error approach is investigated based on the separate design of each screen. With the help of some physical intuition and an equivalent circuit model, it is shown that the conventional use of complement geometries restricts the final desired filtering response. Therefore, unlike the previous studies, the metallic screens are not geometrically complementary in this paper. An excellent agreement between the full-wave simulations and corresponding equivalent circuit models has been observed. Using standard lumped elements, a highly selective miniaturized FSS (0.06λ0 ~ 0.08λ0) with two closely-spaced pass bands is designed, for GSM and WLAN frequencies. Simulation results show a dual-polarized characteristic with a good angular stability performance for the proposed structure.
M. Sanatgar, M. R. Alizadeh Pahlavani, A. Bali Lashak,
Volume 15, Issue 3 (September 2019)
Abstract
This paper presents the control approach for single inverter dual coupled brushless DC motors (DCBLDC) drive system. One of the basic requirements of such systems, is the power balance between two motors and on the other hand, minimizing mechanical fluctuations in order to avoid mechanical equipment damage especially in the state of mechanical resonance. This paper also presents an improved form of the conventional direct torque control (IDTC) for the DCBLDC, which can be used on nine-switch inverters (NSIs). The conventional approaches used in the coupled motors are considered, and then a combination of torque and velocity control is proposed for DCBLDC. After theoretical analysis and drive modeling, whose performance has been simulated by MATLAB/Simulink in terms of dispatching balanced power as well as dealing with transient phenomena owing to malfunctioning of the mechanical connection line. Finally, experiments with the 120W BLDC motors are executed to verify the feasibility of the proposed approach.
S. Abolmaali,
Volume 15, Issue 4 (December 2019)
Abstract
Accurate delay calculation of circuit gates is very important in timing analysis of digital circuits. Waveform shapes on the input ports of logic gates should be considered, in the characterization phase of delay calculation, to obtain accurate gate delay values. Glitches and their temporal effect on circuit gate delays should be taken into account for this purpose. However, the explosive number of combinations of waveform shapes, which can be applied to the input ports of logic gates, causes existing lookup-based methods to have huge space requirements. In this article, instead of considering all possible combinations of waveform shapes in the characterization phase of delay calculation process, the least number of combinations, which are dominant in determining the waveform shape of gate output, is presented. Multivariate Polynomial Regression (MPR) method is used to further reduce the required memory space. Exploration of the possible MPR analyses is performed to find the best regression case with proper memory space reduction and precision. Attained results show a 1.013E6 times reduction in storage space required for storing parameters utilized in extraction of output waveform characteristics in comparison to a state of the artwork, accompanied by acceptable precision.
F. Masoudinia, E. Babaei, M. Sabahi, H. Alipour,
Volume 16, Issue 1 (March 2020)
Abstract
In this paper, a new structure for cascade multilevel inverter is presented which consists of a series connection of several sub-multilevel units. Each sub-multilevel unit comprises of eight unidirectional switches, two bidirectional switches, and six DC voltage sources. For the proposed cascade topology, two algorithms are presented to produce all possible levels at the output voltage waveform. The required analysis of the voltage rating on the switches is provided. In order to verify the performance of the proposed inverter, the experimental results for a 15-level inverter are provided. The experimented 15-level inverter is compared with the other presented inverters in literature in terms of the number of DC voltage sources, switches, drivers, and blocked voltage by switches. The results of comparisons indicate that the experimented 15-level inverter requires lower power electronic elements. Moreover, the blocked voltage on the switches of the proposed topology is less than other topologies.
H. Davari, Y. Alinejad-Beromi,
Volume 16, Issue 1 (March 2020)
Abstract
In this paper, at first, a 24/16 three-phase switched reluctance motor is designed, then the rotor poles shape tips corrected for reduction ripple of single-phase torque waveform. By doing this, the single-phase torque waveform has a flat surface and consequently, the single-phase torque ripple is reduced. Also, due to the commutation between the machine phases, the torque drops during this time, which are known as torque pits. To reduce the ripple torque at these points, which requires overlap between the two successive phases of the machine, the pulse width of the excitation of the machine phases is adjusted. Comparisons have been made between two types of direct current excitation and chopped current (with different pulse widths). The results show that for constant pulse width under chopped current, applying the arc and modifying the shape of the rotor poles can reduce the torque ripple by 3.4%. Also, by applying chopped current control, the torque ripple was reduced by 46.7% compared to its conventional design structure.
A. Bahmanyar, H. Borhani-Bahabadi, S. Jamali,
Volume 16, Issue 3 (September 2020)
Abstract
To realize the self-healing concept of smart grids, an accurate and reliable fault locator is a prerequisite. This paper presents a new fault location method for active power distribution networks which is based on measured voltage sag and use of whale optimization algorithm (WOA). The fault induced voltage sag depends on the fault location and resistance. Therefore, the fault location can be found by investigation of voltage sags recorded throughout the distribution network. However, this approach requires a considerable effort to check all possible fault location and resistance values to find the correct solution. In this paper, an improved version of the WOA is proposed to find the fault location as an optimization problem. This optimization technique employs a number of agents (whales) to search for a bunch of fish in the optimal position, i.e. the fault location and its resistance. The method is applicable to different distribution network configurations. The accuracy of the method is verified by simulation tests on a distribution feeder and comparative analysis with two other deterministic methods reported in the literature. The simulation results indicate that the proposed optimized method gives more accurate and reliable results.
S. H. Montazeri, A. Damaki Aliabad, F. Zare, S. Aghaei,
Volume 17, Issue 1 (March 2021)
Abstract
The direct drive permanent magnet synchronous motor (DD-PMSM) is a suitable choice for high-precision position control applications. Among various control methods of this motor, the vector control approaches especially the field oriented control has a high-performance in the industrial drives. In this method, the components of stator current are controlled independently and as a result, the torque and flux are controlled continuously. Since there are some limitations and constraints in the motor, inverter, and control system, a new anti-windup gain scheduling PID controller based on the adaptive control principles is proposed for the position control loop. In the proposed method, different values are assigned to coefficients of the PID controller according to the position error to achieve high precision. Also, a very high-accuracy encoder and an ARM processor are used for measuring the instantaneous position and implementation of the proposed method, respectively. The simulation and experimental results validate the effectiveness, high accuracy, and good dynamic behavior of the proposed control method.
M. Ghaseminezhad, A. Doroudi, S. H. Hosseinian, A. Jalilian,
Volume 17, Issue 1 (March 2021)
Abstract
Nowadays study of input voltage quality on induction motors behavior has become a controversial subject due to the wide application of these motors in the industry. The impact of grid voltage fluctuations on the performance of induction motors can be included in this area. The majority of papers devoted to the influence of voltage fluctuations on the induction motors are focusing only on the solving of d-q state equations or steady-state equivalent circuit analysis. In this paper, a new approach to this issue is investigated by field analysis which studies the effects of voltage fluctuations on the magnetic fluxes of induction motors. New analytical expressions to approximate the airgap flux density and the torque under-voltage fluctuation conditions are presented. These characteristics are also calculated directly by the finite-element method considering the magnetic saturation and the harmonic fields. Finally, experimental results on a typical induction motor are employed to validate the accuracy of analytical and simulation results.
M. Habibolahzadeh, A. Jalilian,
Volume 17, Issue 2 (June 2021)
Abstract
Electric traction trains are huge non-linear single-phase loads influencing adversely on power quality parameters on the grid side. Hybrid power quality conditioner (HPQC) has been utilized to compensate current unbalance, harmonics, and low power factor in the co-phase traction system simultaneously. By incrementing the traction load, the rating of the HPQC increases and may constraints its application. In this paper, a C-type filter is designed to compensate for some part of the load reactive power while the HPQC compensates the remaining part of the load reactive power. Hence, the capacity of the HPQC is reduced in full compensation (FC) mode compared to the conventional configuration. The satisfactory performance of the HPQC is associated with its DC-link operating voltage. Therefore, the Genetic algorithm (G.A) is adopted to optimize the DC-link voltage performance. Simulation verifications are performed to illustrate the usefulness of the proposed configuration. The simulation results show an 18.86% reduction in the rating of the HPQC with optimized DC-link voltage.
S. Abolmaali,
Volume 17, Issue 3 (September 2021)
Abstract
Area reduction of a circuit is a promising solution for decreasing the power consumption and the chip cost. Timing constraints should be preserved after a delay increase of resized circuit gates to guarantee proper circuit operation. Sensitization of paths should also be considered in timing analysis of circuit to prevent pessimistic resizing of circuit gates. In this work, a greedy area reduction algorithm is proposed which is path-based and benefits well from viability analysis as the sensitization method. A proper metric based on viability conditions is presented to guide the algorithm towards selecting useful circuit nodes to be resized with acceptable performance and area reduction results. Instead of using gate slacks in resizing the candidate gates, all circuit gates are down-sized first and then the sizes of circuit gates that violate the circuit timing constraint are increased. This approach leads to considerable improvement in the complexity and performance of the proposed method. Results show that area improvement of about 88% is achievable. Comparison to a pessimistic method also reveals that on average 14.2% growth in area improvement is obtained by the presented method.
A. Karimpour, A. M. Amani, M. Karimpour, M. Jalili,
Volume 17, Issue 4 (December 2021)
Abstract
This paper studies the voltage regulation problem in DC microgrids in the presence of variable loads. DC microgrids generally include several Distributed Generation Units (DGUs), connected to electrical loads through DC power lines. The variable nature of loads at each spot, caused for example by moving electric vehicles, may cause voltage deregulation in the grid. To reduce this undesired effect, this study proposes an incentive-based load management strategy to balance the loads connected to the grid. The electricity price at each node of the grid is considered to be dependent on its voltage. This guide moving customers to connect to cheaper connection points, and ultimately results in even load distribution. Simulations show the improvement in the voltage regulation, power loss, and efficiency of the grid even when only a small portion of customers accept the proposed incentive.
Y. McHaouar, A. Abouloifa, I. Lachkar, H. Katir, F. Giri, A. El Aroudi, A. Elallali, C. Taghzaoui,
Volume 18, Issue 1 (March 2022)
Abstract
In this paper, the problem of controlling PWM single-phase AC/DC converters is addressed. The control objectives are twofold: (i) regulating the output voltage to a selected reference value, and (ii) ensuring a unitary power factor by forcing the grid current to be in phase with the grid voltage. To achieve these objectives, the singular perturbation technique is used to prove that the power factor correction can be done in the open-loop system with respect to certain conditions that are not likely to take place in reality. It is also applied to fulfill the control objectives in the closed-loop through a cascade nonlinear controller based on the three-time scale singular perturbation theory. Additionally, this study develops a rigorous and complete formal stability analysis, based on multi-time-scale singular perturbation and averaging theory, to examine the performance of the proposed controller. The theoretical results have been validated by numerical simulation in MATLAB/Simulink/SimPowerSystems environment.
M. Khalili, F. Namdari, E. Rokrok,
Volume 18, Issue 1 (March 2022)
Abstract
This paper presents a new single-end scheme to locate and protect faults on the compensated transmission line using the Unified Power Flow Controller (UPFC). The UPFC controllers have remarkable effects on the transient and steady-state components of the voltage and current signals. First of all, this study evaluates the impact of UPFC on Traveling Waves (TW) that pass through the UPFC location. Following that, the effects of UPFC’s harmonic on conventional protections will be investigated using the TW theory. A single-end method will be presented in the next stage to protect and locate the faults on the compensated transmission lines with UPFC. Moreover, an extraction technique (i.e., Discrete Wavelet Transform [DWT]) is used to process the current and voltage signals. As a branch of mathematics, cooperative game is employed in this study to represent the strategic interaction of different players in a context by predefined rules and outcomes. Additionally, this study made use of this theory to distinguish the extracted TWs from each other. The proposed method is assessed considering different fault situations with great variations in operating conditions accompanied by a UPFC placed at the midpoint of the line.
P. Paliwal,
Volume 18, Issue 1 (March 2022)
Abstract
The determination of a suitable technology combination for an isolated micro-grid (IMG) based on hybrid renewable energy resources (HRES) is a challenging task. The intermittent behavior of RES leads to an adverse impact on system reliability and thus complicates the planning process. This paper proposes a two-fold approach to provide a suitably designed HRES-IMG. Firstly, a reliability-constrained formulation based on load index of reliability (LIR) is developed with an objective to achieve a minimum levelized cost of energy (LCOE). Multi-state modeling of HRES-IMG is carried out based on hardware availability of generating units and uncertainties due to meteorological conditions. Modeling of battery storage units is realized using a multi-state probabilistic battery storage model. Secondly, an efficient optimization technique using a decentralized multi-agent-based approach is applied for obtaining high-quality solutions. The butterfly-PSO is embodied in a multi-agent (MA) framework. The enhanced version, MA-BFPSO is used to determine optimum sizing and technology combinations. Three different technology combinations have been investigated. The combination complying with LIR criterion and least LCOE is chosen as the optimal technology mix. The optimization is carried out using classic PSO, BF-PSO, and, MA-BFPSO and obtained results are compared. Further, in order to add a dimension in system planning, the effect of uncertainty in load demand has also been analyzed. The study is conducted for an HRES-IMG situated in Jaisalmer, India. The technology combination comprising of solar, wind, and battery storage yields the least LCOE of 0.2051 $/kWh with a very low value of LIR (0.08%). A reduction in generator size by 53.8% and LCOE by 16.5% is obtained with MABFPSO in comparison with classic PSO. The results evidently demonstrate that MA-BFPSO offers better solutions as compared to PSO and BF-PSO.
S. Abolmaali,
Volume 18, Issue 2 (June 2022)
Abstract
In this article, a critical path identification method is proposed for ternary logic circuits. The considered structure for the ternary circuits is based on 2:1 multiplexers. Sensitization conditions for the employed ternary multiplexers are introduced. Moreover, static timing analysis and dynamic programming are utilized in the identification of true and false paths of the circuit for obtaining more realistic results in a reasonable time. An event-driven simulation engine is also developed for confirming the sensitization state of the identified paths. Some ternary arithmetic logic circuits are designed to depict the effectiveness of the proposed identification method. Simulation results show the correctness and efficiency of the proposed method.
