The Modares Journal of Electrical EngineeringThe Modares Journal of Electrical Engineering
http://mjee.modares.ac.ir/
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http://mjee.modares.ac.ir/
Feed provided by The Modares Journal of Electrical Engineering. Click to visit.Online Static Security Margin Improvement based on Wind Farms
http://mjee.modares.ac.ir/article_14478_0.html
Abstract: Due to high penetration of the wind farms in the networks, they can have a role in the control of the power systems. In this paper, wind farms (WFs) are used to improve the static security margins of the power system. The net active and reactive (generation minus demand) powers of all buses are selected as features to classify the static security of the power system. Feature extraction method is used to save all features effect on the security of power system. Two optimization problems are introduced in this paper to select the optimum way to improve the static security margin improvement. The proposed method is implemented on IEEE 39-bus network and the results show its effectiveness on the static security margin. It should be mentioned that the proposed method can deal with correlated random variables. The real data of Iran's grid is used to validate the nataf transformation.Tue, 12 Apr 2016 19:30:00 +0100Short-Switch Fault Ride-Through andPost-Fault Reconfiguration Strategy for a Static Synchronous ...
http://mjee.modares.ac.ir/article_16792_5538.html
The cascaded H-bridge (CHB) converter is one of the viable options for large-scale power conversion. Owing to the increased number of components involved in this topology, converter reliability and fault-tolerant control are important issues. This paper proposes a new short-switch fault protection scheme and a post-fault modulation (PFM) strategy to keep the performance of a CHB converter in a static synchronous series compensator (SSSC) application. The SSSC is a series converter to the transmission line, which controls the power flow in the line. Acting as a series converter, any abnormal action of SSSC can affect the whole line reliability. So following the fast fault detections and protections, remedial actions have to be considered to extend normal operation of the SSSC and, in some cases, derate the system to prevent unexpected shutdowns. The new method of short switch fault protection can eliminate the fault in the proper time, while the novel proposed PFM strategy guarantee the continuation of converter operation. This method is based on the application of increasing dc bus utilization techniques in conjunction with the phase shifted pulse width modulation method, which generates the balanced grid currents. Take the advantages of this method; the converter is able to control the transmission line power flow with the remaining healthy H-bridges. Simulation results validate the effectiveness of the proposed method. Fri, 20 Jan 2637 20:30:00 +0100Reducing both Torque and Flux Ripple in the DTC of IPMSM Incorporating Duty Cycle Calculation ...
http://mjee.modares.ac.ir/article_14479_0.html
The Direct Torque Control (DTC) of Interior Permanent Magnet Synchronous Motor (IPMSM) offers simple structure and fast torque response. The conventional Switching Table based DTC (ST-DTC) presents some disadvantages like high torque and flux ripple and also variable switching frequency. This paper proposes a simple, but effective method to reduce both torque and flux ripple in DTC of IPMSM with emphasis on structure simplicity and fast dynamics. New switching table with only two active vectors was introduced for each sector and the torque control hysteresis band has been replaced by duty cycle calculation unit. For flux ripple reduction, conventional hysteresis-based controller has been replaced by simple dithering technique. Applying high frequency triangular signal to flux controller hysteresis band input, increases the number of selected vectors in one period of fundamental frequency and makes stator current more sinusoidal. The duty cycle calculation unit has been implemented to operate on each selected vector with the aim of torque ripple RMS minimization.Tue, 12 Apr 2016 19:30:00 +0100A Nonisolated Transformerless High Voltage Gain Buck Boost dc-dc Converter
http://mjee.modares.ac.ir/article_16794_5538.html
A novel transformer less high step-up buck–boost dc-dc converter is proposed in this paper. The output voltages of some sources such as fuel cell, photovoltaic are not regulated. Therefore voltage regulation is required to fix the DC-link voltage. Hence, a buck boost DC/DC converter is suitable to regulate the output voltage of these sources. The presented converter voltage gain is higher that of the conventional boost, buck boost, CUK, SEPIC and ZETA converters and high voltage gain can be obtained with a suitable duty cycle. In this converter, only one power switch is utilized. The voltage stress across the power switch and diodes is low. Hence, the low on-state resistance of the power switch can be selected to decrease conduction loss of the switch and improve efficiency. The low voltage stress across the diodes allows the prevent the reverse-recovery current problem. The proposed converter can be operated in the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). The presented converter has simple structure; therefore the control of the proposed converter will be easy. The principle of operation and the mathematical analyses of the proposed converter are explained. The validity of the presented converter is verified by the experimental results.Fri, 20 Jan 2637 20:30:00 +0100Special-Issue-PEPS, Power Electronics and Power Systems Design of an Model Predictive ...
http://mjee.modares.ac.ir/article_14480_0.html
This paper develops new results on the use of model predictive control to regulate the attitude of a ground station antenna. Two degree of freedom AZ-EL pedestal is considered as ground station antenna. Permanent Magnet Synchronous Motors (PMSMs) are taken into consideration as the best choice for satisfaction of control objectives as actuators. The design is based on a two cascade controller consist of MPC and a simple feedback linearization, respectively. The proposed approach provide more smooth tracking and lower energy consumption with respect to analogous works. The model predictive controller employs integral action, resulting in zero steady-state error and load torque disturbance rejection. Realistic disturbances caused by wind and load is considered and applied to an industry-sized pedestal. The reference data of azimuth and elevation angles are chosen from a real tracking mission. The simulation results verify the effectiveness of the proposed method. a a a a a a a a aTue, 12 Apr 2016 19:30:00 +0100Induction Motor Drive Performance Improvement of Indirect Vector Control using Fuzzy PID controller
http://mjee.modares.ac.ir/article_16795_5538.html
This paper presents the speed control scheme of indirect vector controlled of induction motor (IM) drive. Voltage source inverter type space vector pulse width modulation (SVPWM) is used for PWM controlling scheme. Regarding the capabilities and potentials of intelligent based on Fuzzy logic in the control of non-linear and complex systems, the Fuzzy PID controllers is developed for controlling the speed, torque, and flux of an IM. The performances of the proposed FLC-based IM drives are investigated and compared to those obtained from the conventional proportional-integral (PI) controller-based drives both simulated at different dynamic operating conditions such as step change in command speed, load change, and increase in the rotor resistance. The comparative results show that the FLC is more robust, found to be a suitable replacement of the conventional PI controller for the high-performance industrial drive applicationsFri, 20 Jan 2637 20:30:00 +0100Confidence-Interval Based Multi-Objective Constrained Probabilistic Optimal Capacitor Placement ...
http://mjee.modares.ac.ir/article_14481_0.html
This paper presents a probabilistic confidence-interval based method for optimal placement of shunt capacitors in distribution networks, considering probabilistic characteristics of loads. The objective function is reduction of loss and improvement of voltage profile. Backward forward sweep has been used to obtain the power flow results in distribution system. An Integer Harmony Search Algorithm has been used to solve the optimization problem. The probabilistic aspects of the problem have been solved using Point Estimation (PE) method. Introduction of a confidence interval index using Gram-Charlier expansion is the novelty of this paper. This index shows the risk of system to violate its security constraints when loads are considered as stochastic random variables. Using this index, planners can find the optimal sitting and sizing of capacitors in distribution systems based on their desired level of risk. Verification of the proposed method has been tested on 33-bus radial distribution system. Results demonstrate the effectiveness and merits of the proposed method.Tue, 12 Apr 2016 19:30:00 +0100Electronic and optical properties of single-walled silicon nanotubes: the sp3 tight-binding model
http://mjee.modares.ac.ir/article_16796_5538.html
In this paper, we investigate the curvature effects on the electronic band structure and dielectric function of single-walled silicon nanotubes and carbon nanotubes, based on tight-binding method. The curvature nature of nanotubes causes radius-dependent σ-π-orbital hybridization which leads to optimization of tight-binding model for each radii. First, the effects of orbitals overlap and the structural optimization on the electronic band structure of small radius nanotubes are investigated. Second, the imaginary part of dielectric function of nanotubes, which is related to optical absorption coefficient, is obtained by calculating the interband optical matrix elements using gradient approximation. It is shown that the σ-π-tight-binding model optimization due to the curvature effects, introduces small changes to the optical transition energies obtained by simple π-band tight-binding model. The results show that the curvature effects are more important in small radius tubes. Fri, 20 Jan 2637 20:30:00 +0100Short-Switch Fault Ride-Through and Post-Fault Reconfiguration Strategy for a Static ...
http://mjee.modares.ac.ir/article_16793_0.html
Multilevel converters play key roles in motor drives, flexible power transmissions, and grid-tied renewable energy generation units. Therefore, availability and reliability of the multilevel converters is an important issue. Following fast fault detection, remedial actions can extend normal operation of the multilevel converters and, in some cases, derate the system to prevent unexpected shutdowns. Since these kinds of converters are featured by a high number of semiconductor switches, it is possible to reshuffle the topology when a semiconductor switch failure occurs. This paper proposes a new fault-tolerant strategy to keep the performance of a cascaded H-bridge based static synchronous series compensator, as a FACTS controller, with a single faulty switch, by aiding a combination of hardware and software reconfiguration. The proposed fault-tolerant strategy is based on the use of a third harmonic injection technique in conjunction with the phase-shift modulation method, which makes the felicitous use of the converter capacity in the faulty condition, and generates balanced line voltages. The important feature of the proposed method is the absence of any changes in the structure of the main control system. Simulation results are given to verify the developed system.Fri, 19 May 2017 19:30:00 +0100Realization of a Localized Surface Plasmon Resonance Gas Sensor, Based on Ag nanoparticles
http://mjee.modares.ac.ir/article_16797_5538.html
در این تحقیق، پاسخ حسگر گازی پلاسمونی شامل نانوذرات نقره بر روی بستر شیشه (SiO2) در معرض گاز نیتروژن با استفاده از تحریک پلاسمونهای سطحی موضعی مورد بررسی قرار گرفت. سنتز نانوذرات نقره با استفاده از روش سنتز شیمیایی به گونه ای انتخاب گردید که اندازه بهینه ذرات کروی شکل برای رسیدن به بهترین پاسخ و حساسیت در خروجی حسگر بدست آید. بهترین پاسخ حسگر برای نانوذرات با قطر متوسط 30 نانومتر در طول موج تشدید جذب پلاسمونی حدود 415 نانومتر بدست آمد. جذب فیزیکی مولکول های نیتروژن توسط نانوذرات نقره باعث افزایش ضریب شکست محیط اطراف این ذرات گردید. زمانی که نانوذرات در معرض غلظت های مختلف از گاز نیتروژن (ppm250-0) قرار گرفتند، افزایش ضریب شکست باعث جابجایی طول موج پلاسمونی به سمت طول موج های بلندتر شد. با بررسی این پاسخ نشان داده شد که این طیف پلاسمونی نسبت به گاز نیتروژن حساس بوده و حساسیت حدود 0.6 نانومتر در غلظت ppm100 دارد. پاسخ های حسگر پلاسمونی توسط دستگاه طیف سنجی مرئی-فرابنفش اندازه گیری شدند. بررسی های انجام شده با نتایج حاصل از شبیه سازی ساختار و محاسبات نظری مربوط به ساختار پلاسمونی مورد نظر نیز مقایسه گردید که بیانگر تطابق قابل قبولی میان نتایج بدست آمده بود.Fri, 20 Jan 2637 20:30:00 +0100Energy-Efficient Resource Allocation in NOMA-based HCN Systems
http://mjee.modares.ac.ir/article_16803_5538.html
In this paper, the energy efficient resource allocation in NOMA-based heterogeneous cellular network (HCN) systems is investigated. Since energy consumption and its limitations is one of the important challenges in fifth generation of cellular networks (5G), we propose a resource allocation problem which allocates power and subcarriers to multiple users to achieve the best system energy efficiency (EE). To solve the corresponding problem an iterative algorithm is used. In each iteration power and subcarrier are assigned separately. In each iteration, to solve the power allocation problem dual method considering successive convex approximation (SCA) approach is used, and to solve the subcarrier allocation problem, mixed integer non-linear programing (MINLP) of optimization toolboxes is applied. The effectiveness of this resource allocation method is illustrated in simulation results section.Fri, 20 Jan 2637 20:30:00 +0100