فهرست مطالب

Amirkabir International Journal of Electrical & Electronics Engineering - Volume:51 Issue:1, 2019
  • Volume:51 Issue:1, 2019
  • تاریخ انتشار: 1398/03/11
  • تعداد عناوین: 12
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  • Sekine Asadi Amiri *, Hamid Hassanpour Pages 3-12
    Saliency regions attract more human’s attention than other regions in an image. Low- level and high-level features are utilized in saliency region detection. Low-level features contain primitive information such as color or texture while high-level features usually consider visual systems. Recently, some salient region detection methods have been proposed based on only low-level features or high-level features. It is necessary to consider both low-level features and high-level features to overcome their limitations. In this paper, a novel saliency detection method is proposed which uses both low-level and high-level features. Color difference and texture difference are considered as low-level features, while modeling human’s attention to the center of the image is considered as a high-level feature. In this approach, color saliency maps are extracted from each channel in Lab color space; and texture saliency maps are extracted using wavelet transform and local variance of each channel. Finally, these feature maps are fused to construct the final saliency map. In the post processing step, morphological operators and the connected components technique are applied on the final saliency map to construct further contiguous saliency regions. We have compared our proposed method with four state-of-the-art methods on the MSRA (Microsoft Security Response Alliance) database. The averaged F-measure over 1000 images of the MSRA dataset is achieved 0.7824. Experimental results demonstrate that the proposed method outperforms the existing methods in saliency region detection.
    Keywords: Saliency region detection, connected components, low-level feature, high-level feature
  • Arman Alimardani *, Shahram Jadid Pages 13-20
    It is necessary to form an energy system in order to deliver the electrical power to a region that delivering energy to them from the national grid is not possible. At the moment, using the hybrid renewable energy systems (HRES) is the suggestion of more articles and scientific books because of environmental problems, nearing to the end of fossil fuels, and challenges including unpredictability of the renewable resources. In order to optimize the operation of a PV-diesel-battery energy system in the paper, a practical model has been proposed to optimal day-ahead scheduling diesel generator in a PV-diesel-battery system. Because of the uncertainty of the solar prediction data, it has been considered by Monte-Carlo simulation in the day-ahead diesel generator scheduling model (DDSM). The model has been implemented for PV-diesel-battery system on a sample desert area in Kerman in Iran. The area load modeling has been done by predicting electrical consumption of some days of the seasons that are the symbols of all days of the seasons. Annual and five-year environmental, economic, and technical indexes have been computed and the results have been compared using the indexes in different reliability and storing capacity scenarios. Sensitivity analysis of the results has been done for the PV-diesel-battery system.
    Keywords: Hybrid Renewable Energy Systems (HRES), Diesel generator, Scheduling, Uncertainty, Pollution
  • Moein Mozaffarzadeh *, Seyed Amin Ollah Izadi Avanji, Hamid Reza Jashnani Pages 21-28
    Photoacoustic imaging (PAI) is a promising medical imaging modality which provides the resolution of Ultrasound (US) and the contrast of Optical imaging modalities. One of the most important challenges in PAI is image formation, especially in the case that a linear-array US transducer is used for data acquisition. This is due to the fact that in the linear-array scenario, there is only 60 degrees view angle available to detect the photoacoustic waves, and due to the nature of photoacoustic waves, the problem is inherently a limited angle-view one. Delay-and-Sum (DAS) is the most prevalent beamforming algorithm in PAI due to its simple implementation, but it provides a low quality image. One of the alternatives is Minimum Variance (MV) and its derivatives. In this paper, we introduce a novel beamforming algorithm based on the combination of Forward-Backward MV (FBMV) and Delay-Multiply-and-Sum (DMAS) beamforming algorithms (DMAS_FBMV). It was shown that the FBMV can be integrated into the expansion of the DMAS. The proposed method is evaluated numerically. The results demonstrate that the DMAS_FBMV significantly outperforms the FBMV in the term of sidelobes (12 dB improvement at 45 mm). Quantitative metrics such as Signal-to-Noise (SNR) and Full-Width-Half-Maximum have been calculated for better evaluation.
    Keywords: Photoacoustic imaging, image formation, beamforming, linear-array imaging, contrast improvement
  • Mohammad Saeed Mahdavi, Gevork B. Gharehpetian *, Parisa Ranjbaran, Hossein Azizi Pages 31-38
    Usage of flywheel energy storage system (FESS) is a common method for frequency regulation due to its high power injection capacity and long life time. FESS is equipped by two back-to-back inverters including grid-side inverter and machine-side inverter. In conventional method, the machine-side inverter sets the active power and machine flux while grid-side inverter sets the reactive power and common DC bus voltage by conventional PI current controllers. Especially for frequency regulation, FESS is constantly faced with change of power and operating point but PI controller performance is dependent on operating point of the system. In this paper, at first, the control of both active and reactive power is moved to grid-side inverter and control of DC bus voltage and machine flux is moved to machine-side inverter. Then a modified version of fuzzy PI controller is proposed for grid-side inverter control in which rated PI controller coefficients values are optimally designed for rated operating point by feed-back linearization and pole placement then fuzzy system (FS) is used for PI coefficients variation around the rated values when operating point changes. Experimental results verify the performance of the proposed FESS control system for AUT microgrid frequency regulation and also moving the DC bus voltage control to machine-side inverter.
    Keywords: Flywheel Energy Storage, Fuzzy Logic System, Microgrid, Frequency Regulation
  • Abbas Ali Sharifi * Pages 39-44
    Cognitive radio (CR) technology has been suggested for effective use of spectral resources. Spectrum sensing is one of the main operations of CR users to identify the vacant frequency bands. Cooperative spectrum sensing (CSS) is used to increase the performance of CR networks by providing spatial diversity. The accuracy of spectrum sensing is the most important challenge in the CSS process since the sensing performance is vulnerable to security attacks. Primary user emulation attack (PUEA) is one of the most important attacks, where a malicious attacker sends the signal similar to the signal of the legitimate primary user (PU) and deceives the CR sensors to avoid them from accessing the spectrum holes. In this paper, we investigate two different strategies for the attacker. Always present (AP) and spectrum sensing (SS) based strategies. In the AP scenario, the PUEA, without performing spectrum sensing, continuously sends its fake signals. In SS based PUEA, the attacker senses the spectrum to identify the spectrum holes and then only sends its signals in idle frequency bands. Assuming attack strategy, we estimate normalized attack power factor (NAPF) to obtain an optimal value of energy detection threshold. The parameter NAPF is the ratio of the average emitted power of the attacker to the average power of the PU transmitter. The obtained results verify the superiority of the proposed energy detection approach compared to the existing conventional methods.
    Keywords: CR, PUEA, NAPF, AP, SS
  • Mohammad Amin Jalali Kondelaji, Mojtaba Mirsalim * Pages 45-54

    A variable reluctance machine (VRM) has been proven to be an outstanding candidate for electric vehicle (EV) applications. This paper introduces a new double-stator, 12/14/12-pole three-phase hybrid-excited modular variable reluctance machine (MVRM) for EV applications. In order to demonstrate the superiorities of the proposed structure, the static torque characteristics and dynamic performances of the novel MVRM are compared with two other VRMs with similar dimensions and parameters. Then, the steady-state performance of the proposed motor with single-pulse control (SPC) for two operating speeds is obtained. Additionally, the cogging torque profile of the machine is derived. Finally, the motor performance is investigated under faulty conditions. The proposed MVRM is built and the test results are obtained. Both of the simulation and test results indicate that the proposed MVRM produces higher average torque compared to the two other machines in the same operational speeds, with an ignorable cogging torque.

    Keywords: Electric vehicle applications, hybrid-excited machine, single-pulse control (SPC), variable reluctance machine
  • Ahmadreza Alaei *, Dong Hee Lee, Jin Woo Ahn, Sayed Morteza Saghaeian Nejad Pages 55-62
    This paper focuses on three commonly used sensorless methods based on high-frequency signal injection; namely, the rotating sinusoidal injection in the stationary reference frame, the pulsating sinusoidal injection in the estimated synchronous reference frame, and the pulsating square wave injection in the estimated synchronous reference frame. Although these methods have found applications in interior permanent magnet synchronous motor (IPMSM) sensorless drives. Some efforts have been performed to compare such high frequency signal injection based methods from viewpoint of some parameters such as injection frequency, voltage magnitude and so on. However, evaluation of their dynamic seems to await further investigation and evaluation. Hence, some of motor parameters such as pole number, machine saliency ratio, that affect the performance of the saliency based sensorless methods are evaluated in this paper. Moreover, some such other parameters in driver circuit such as current measurement noise, effect of time delay on demodulation, and load disturbance effect are also explored. The maximum torque per ampere (MTPA) strategy is employed to improve motor driven torque and overcome the load torque by using of the reluctance torque component. Finally, simulation and experimental results are used to investigate the effects of the above parameters on the performance of high frequency signal injection based sensorless methods.
    Keywords: High-frequency signal injection, Interior permanent magnet synchronous motor, Maximum torque per ampere strategy, Position estimation, Sensorless control
  • Kamran Davoodi *, Javad Shokrollah Moghani, Sina Salehi Dobakhshari Pages 63-70
    This paper presents a 4th order CLCL resonant converter which is suitable for constant current power supply applications. This converter is designed with Immittance characteristic with two inductors and two capacitors in resonant network. A detailed analysis and design process of a 200w converter as a constant current supply have been provided and simulation results are verified with results of a constructed converter. In analyzing this converter, the AC analysis method is used. This converter with its unique structure, a combination of series and parallel resonant converter, has the advantages of both. As a constant current supply, CLCL resonant converter has the advantages of rigidity against short circuit even without a controller, easy operation in parallel mode, low circulating currents and high efficiency due to its soft switching operation. For this converter, leakage and magnetizing inductance of a transformer can be used as a part of the resonance network and it decreases the converter size. Also series capacitor, eliminates the DC component and prevents the transformer saturation in unbalance conditions. With fixed-frequency performance, filter design also will be easier. Considering these advantages, the proposed topology can be used in a variety of applications such as magnetic power supplies, capacitor charging power supplies and agitator for laser diodes.
    Keywords: Constant current, DC-DC, Immittance, resonance converter, high efficiency
  • Milad Dalali, Hosein Kazemi Karegar * Pages 71-82
    In wide area measurement systems, PMUs are the main component measuring real time synchronized data from different buses. Installation of PMUs at all buses is a primary way to provide full observability of the power network. However, it is not practical in real networks due to the relatively expensive cost of PMUs and other technical limitations. Optimal PMU Placement (OPP) is an optimization problem providing full observability of the power network with minimum number of PMUs. However, additional goals are often considered in OPP problem. In this paper, OPP problem is solved from voltage stability viewpoints. The presence of VSC-HVDC based resources and decomposition of the power network into intentional islanded parts are selected as two main approaches to improve the voltage stability margin in the power network. Hence, OPP solution is obtained considering both integrated and islanded operation modes of the network with the presence of HVDC links and their voltage stability considerations. Since, the location of HVDC could simultaneously affect on the network voltage stability and OPP results, the proposed algorithm is designed as a multi stage method to obtain optimal locations for both HVDC link and PMUs. Due to the linear and binary structure of the problem, Binary Integer Linear Programming (BILP) is used to solve the problem. The performance of the proposed OPP problem is investigated on IEEE 14-, 30- and 118-bus test systems considering normal operation and different contingencies consist of Single PMU Failure (SPF) and Single Line Outage (SLO).
    Keywords: HVDC, islanding, observability, PMU placement, voltage stability
  • Farzin Yaghmaee *, Ehsanhosein Kalatehjari Pages 83-92
    In this paper, a novel saliency theory based RR-IQA metric is introduced. As the human visual system is sensitive to the salient region, evaluating the image quality based on the salient region could increase the accuracy of the algorithm. In order to extract the salient regions, we use blob decomposition (BD) tool as a texture component descriptor. A new method for blob decomposition is proposed, which extracts blobs not only in different scales but also in different orientations. Different blob components consist of location of blobs, blob shape and color attributes are used to describe texture of the image accordance to the human visual system conception. A region Covariance matrix is calculated from extracted blob components which can be easily interpreted in terms of its eigenvalues. Therefore, the reference image is described as a squared covariance matrix and a good data reduction is achieved. The same process is used for describing the received image in the destination. Finally, the image quality is estimated by using the eigenvalues of two covariance matrices. The performance of the proposed metric is evaluated on different databases. Experimental results indicate that the proposed method performs in accordance with the human visual perception and uses few reference data (maximum 90 values).
    Keywords: Reduced-Reference Image Quality Assessment, Human Visual System, Blob detection, salient regions
  • Sayeh Mirzaei *, Alireza Gholipour Pages 93-100
    Antenna 3D pattern measurement can be a tedious and time consuming task even for antennas with manageable sizes inside anechoic chambers. Performing onsite measurements by scanning the whole 4π [sr] solid angle around the antenna under test (AUT) is more complicated. In this paper, with the aim of minimum duration of flight, a test scenario using unmanned aerial vehicles (UAV) is proposed. A practically optimal scanning strategy is presented. The suggested techniques are beneficial particularly for the case of large directive antennas. The UAV follows a predefined trajectory in the scanning windows around the AUT and reads the field strength. Then, using compressed sensing (CS) method, the antenna pattern is reconstructed. It is shown that applying Bayesian CS algorithm to the samples of field intensity gathered by UAV can efficiently reconstruct the pattern. Discrete cosine Transform (DCT) is utilized for sparsifying the antenna patterns. Performance is evaluated by obtaining the reconstructed patterns for different antenna types. The effects of the antenna type and area of scanning are analyzed. It is shown that satisfying performance can be achieved with measuring about 50 percent of the total pattern samples. The reconstruction error of different CS implementations is computed and superiority of Bayesian CS is illustrated.
    Keywords: Antenna pattern, unmanned aerial vehicle(UAV), compressed sensing (CS), Bayesian CS, field scanner
  • Maryam Shirkavand, Mohammad Bavir *, Ali Fattah, Hamid Reza Alaei, Mohammad Hossein Tayarani Najaran Pages 101-110
    Dye-sensitized solar cells (DSSCs) are categorized as some of inexpensive thin-film solar cells. The basis and foundation of these cells is a semiconductor that consists of an electrolyte and a light-sensitive anode. Titanium dioxide (TiO2) is a semiconductor that plays the role of anode and is the main constituent of these cells. In this paper, we have addressed the functionality and performance of TiO2 films with thicknesses of 2.96, 7.54 and 11.1 micrometers in DSSCs. The morphology, crystal structure and the optical bandgap are some of the effective elements on the electron transfer rate and recombination process in the TiO2 film. When using TiO2, one must choose the optimum thickness to ensure optimal short-circuit current, open-circuit voltage and fill factor, so that the cell can have the highest possible efficiency. Analyzing the obtained characteristic curves, it is concluded that the efficiency of a cell with a 2.96 micrometer TiO2 film is 4.2%; the efficiency of a cell with a 7.54 micrometer TiO2 film is 5.54% and the efficiency of a cell with an 11.1 micrometer Tio2 film is 6%. Also, analyzing the EIS shows that the highest electron life time is 17 milliseconds which is obtained for the cell with an 11.1 micrometer TiO2 film. The films of TiO2 for each cell are provided by the doctor-blade deposition method and the dyes are deposited on their surface.
    Keywords: Dye-sensitized solar cell, Photoanode, TiO2, Thickness, EFFICIENCY