Showing 77 results for Nn
M. Khalaj-Amirhosseini,
Volume 17, Issue 1 (3-2021)
Abstract
Linear and planar antenna arrays are synthesized to have maximum directivity for a specified sidelobe level. The directivity is maximized subject to a given SLL. The beamwidth and the zeros of array factor are studied as well as the directivity. Maximum directivity-arrays are compared through some examples with super-directive, uniform, Dolph-Chebyshev and Riblet-Chebychev arrays to find a complete definition of optimum arrays. Also, the optimum value of n-bar is intuitively found for Taylor arrays.
J. Fatemi-Nasab, S. Jarchi, A. Keshtkar,
Volume 17, Issue 1 (3-2021)
Abstract
In this study, a radiation pattern reconfigurable microstrip antenna is designed and fabricated. The antenna’s radiation pattern is directed in 9 different angles by employing a radiating patch and embedding complementary split ring resonators (CSRR) on the ground plane. The radiating patch is of circular shape, while for CSRR elements both circular and rectangular shapes are investigated. The antenna is excited through coaxial feed. There are four CSRR cells on the ground plane. With applying slots on CSRR’s arms and loading them by pin diodes, variable length CSRRs are obtained which result in radiation pattern reconfigurable property. Radiation characteristics of the antenna versus different switching modes of pin diodes are investigated and illustrated. The proposed antenna is also compact. The designed antenna was fabricated on FR4 substrate with thickness of 1.6 mm, and measurement results are provided. The results demonstrate that the presented antenna has impedance bandwidth of 2.39-2.47 GHz with a gain of more than 7 dBi.
R. Rezavandi, D. A. Khaburi, M. Siami, M. Khosravi, S. Heshmatian,
Volume 17, Issue 2 (6-2021)
Abstract
Recently, Brushless Cascaded Doubly Fed Induction Generator (BCDFIG) has been considered as an attractive choice for grid-connected applications due to its high controllability and reliability. In this paper, a Finite Control Set Model Predictive Control (FCS-MPC) method with active and reactive power control capability in grid-connected mode is proposed for controlling the BCDFIG in a way that notable improvement of the dynamic response, ripple reduction of the active and reactive power waveforms and also better THD performance are achieved compared to the traditional approaches such as Vector Control (VC) method. For this purpose, the required mathematical equations are obtained and presented in detail. In order to validate the proposed method performance, a 1–MW grid-connected BCDFIG is simulated in MATLAB/Simulink environment.
M. Khalaj-Amirhosseini,
Volume 17, Issue 2 (6-2021)
Abstract
Nonuniform Phased Sampling method is proposed to phase-only synthesize the power pattern of both linear and planar antenna arrays. This method modifies the conventional sampling method which is used for amplitude-phase synthesis. This method is based on assigning suitable phases to the sampling points of radiation pattern in order to reach desired amplitude of currents. Some examples are given to verify the effectiveness of the proposed method for both pencil-beam and shaped beam patterns.
H. Shayeghi, Y. Hashemi,
Volume 17, Issue 3 (9-2021)
Abstract
The main idea of this paper is proposing a model to develop generation units considering power system stability enhancement. The proposed model consists of two parts. In the first part, the indexes of generation expansion planning are ensured. Also, small-signal stability indexes are processed in the second part of the model. Stability necessities of power network are supplied by applying a set of robustness and performance criteria of damping. Two parts of the model are formulated as two-objective function optimization that is solved by adaptive non-dominated sorting genetic method-III (ANSGM-III). For better decision-making of the final solution of generation units, a set of Pareto-points have been extracted by ANSGM-III. To select an optimal solution among Pareto-set, an analytical hierarchy style is employed. Two objective functions are compared and suitable weights are allocated. Numerical studies are carried out on two test systems, 68-bus and 118-bus power network. The values of generation expansion planning cost and system stability index have been studied in different cases and three different scenarios. Studies show that, for example, in the 68-bus system for the case of system load growth of 5%, the cost of generation expansion planning for the proposed model increased by 7.7% compared to the previous method due to stability modes consideration and the small-signal stability index has been improved by 6.7%. The proposed model is survived with the presence of a wide-area stabilizer (WAS) for damping of oscillations. The effect of WAS latency on expansion programs is evaluated with different amounts of delay times.
A. Chaabane, M. Guerroui,
Volume 17, Issue 4 (12-2021)
Abstract
A new design of a Coplanar Waveguide-Fed (CPW) Ultra Wideband (UWB) Rhombus-shaped antenna for Ground Penetrating Radar (GPR) applications is designed and discussed in this work. The antenna has a simple design which is composed by a rhombus-shaped patch and a modified ground plane. The working bandwidth is improved by removing the metal from the upper part of the ground plane surrounding the patch and by introducing a corrugation geometry in the ground plane. The proposed antenna was designed on a low-cost FR4-substrate having a compact size of 0.2721λ0×0.2093λ0×0.0157λ0 at 3.14 GHz. All the simulations were carried out by using the commercially software CST Microwave StudioTM. The simulated results show that the designed antenna covers an UWB extending from 3.14 GHz to 13.82 GHz (125.94%) and indicate excellent radiation performances throughout the operating bandwidth. The measured bandwidth is nearly extending between 3.95 GHz and 13.92 GHz (111.58%). Besides, the antenna bandwidth response was checked in close proximity to a mass of Concrete. The obtained results are satisfactory and assure the efficiency of the designed antenna to work as a GPR antenna.
F. Bahmanzadeh, F. Mohajeri,
Volume 18, Issue 1 (3-2022)
Abstract
In this article, a very small flexible antenna with dual-band rejection specifications is proposed for operating in both wearable and ultra-wideband (UWB) applications. The overall size of this antenna is about 18×18×0.508 mm3 and by etching out two rectangular slot type single split-ring resonators (SRRs) of different dimensions from the radiating patch, dual band-notched specifications are obtained in WiMAX (3.3 GHz to 3.7 GHz) and WLAN (5.15 GHz to 5.825 GHz) wireless communication bands. The designed antenna operates over a wide impedance bandwidth (|S11| < –10 dB) from 2.1 GHz to 12 GHz which can cover the whole UWB band from 3.1 GHz to 10.6 GHz and reject the two mentioned bands. An asymmetrical partial ground plane and a beveled radiating patch are utilized to achieve 140% fractional bandwidth. Also, due to the good wearable radiation characteristics, this antenna can operate in industrial scientific medical (ISM) band from 2.4 GHz to 2.5 GHz. Meanwhile, the specific absorption ratio (SAR) value of the proposed antenna is less than the standard limit of 1.6 W/kg.
A. Saffari, S. H. Zahiri, M. Khishe,
Volume 18, Issue 1 (3-2022)
Abstract
In this paper, multilayer perceptron neural network (MLP-NN) training is used by the grasshopper optimization algorithm with the tuning of control parameters using a fuzzy system for the big data sonar classification problem. With proper tuning of these parameters, the two stages of exploration and exploitation are balanced, and the boundary between them is determined correctly. Therefore, the algorithm does not get stuck in the local optimization, and the degree of convergence increases. So the main aim is to get a set of real sonar data and then classify real sonar targets from unrealistic targets, including noise, clutter, and reverberation, using GOA-trained MLP-NN developed by the fuzzy system. To have accurate comparisons and prove the GOA performance developed with fuzzy logic (called FGOA), nine benchmark algorithms GOA, GA, PSO, GSA, GWO, BBO, PBIL, ES, ACO, and the standard backpropagation (BP) algorithm were used. The measured criteria are concurrency speed, ability to avoid local optimization, and accuracy. The results show that FGOA has the best performance for training datasets and generalized datasets with 96.43% and 92.03% accuracy, respectively.
V. M. Zavylov, I. Y. Semykina, S. A. Abeidulin, E. A. Dubkov, A. S. Veliliaev,
Volume 18, Issue 1 (3-2022)
Abstract
The promising element of the infrastructure of unmanned electric vehicles is wireless chargers. The central part of such systems is a resonant circuit that provides wireless power transfer. The article discusses a set of criteria used for making the rational choice of the resonant circuit parameters. Such criteria include the efficiency, the current transfer coefficient, the excess voltage on the resonant circuit capacitors over the input voltage, the ratio between the transmitting circuit current and the receiving one. For the resonant circuit with fixed coils size and fixed resonant frequency, the families of curves were obtained via parametric analysis to show how these criteria change depending on the inductance and capacitance of the resonant circuit. The obtained dependencies allow choosing the rational inductances and capacitances of the resonant circuit, providing for a given size and a given value of the input voltage the highest conveyed power with the highest efficiency at the minimum voltage class of capacitors and the minimum current of semiconductor switches. The results of the parametric analysis were confirmed experimentally.
T. Barforoushi, R. Heydari,
Volume 18, Issue 2 (6-2022)
Abstract
Curtailment of the production of wind resources due to uncertainty can affect the expansion of the transmission networks. The issue that needs to be addressed is how to expand the transmission network, which is accompanied by increasing wind energy utilization. In this paper, a new framework is proposed to solve the transmission expansion planning (TEP) problem in the presence of wind farms, considering wind curtailment cost. The proposed model is a risk-constrained stochastic bi-level problem that, the difference between the expected social welfare and investment cost is maximized at the upper level where optimal decisions on expansion plans are adopted by the independent system operator (ISO). To make the best use of wind generation resources, a new term called wind power curtailment cost is added to the upper level. Also, the risk index is included in expansion decisions. The market-clearing is considered at the lower level, aiming at maximizing social welfare. Uncertainties relating to wind power and the forecasted demand are modeled by sets of scenarios. Using duality theory, the proposed framework is modeled as mixed-integer linear programming (MILP) problem. The model is examined using the classical Garver’s six-bus test system and the IEEE 24-bus reliability test system (RTS). The results show that by considering the wind curtailment cost, the transmission network is expanded in a way that increases the wind energy utilization factor from 92.05% to 95.17%.
S. Saeedinia, M. A. Shamsi-Nejad, H. Eliasi,
Volume 18, Issue 2 (6-2022)
Abstract
This paper proposes a grid-connected single-phase micro-inverter (MI) with a rated power of 300 W and an appropriate control strategy for photovoltaic (PV) systems. The proposed MI is designed based on a two-stage topology. The first stage consists of a SEPIC DC-DC converter with high voltage gain to step up the voltage of the PV panel and harness the maximum power, while the second stage includes a full-bridge DC-AC converter. The advantages of the proposed MI are the use of fewer components to provide suitable output voltage level for connection to a single-phase grid, continuous input current, limited voltage stress on the switch, high efficiency, long operational lifetime, and high reliability. Lower input current ripple and the presence of film capacitors in the power decoupling circuit increase the lifetime and reliability of the proposed MI. In the proposed MI, the active power decoupling circuit, which is normally used in a typical single-stage SEPIC-based MI, is eliminated to achieve both a long lifetime and high efficiency. The operating principles of the proposed MI are analyzed under different conditions. The results of design and simulation confirm the advantages and proper performance of the proposed MI.
M. Khalaj-Amirhosseini,
Volume 18, Issue 3 (9-2022)
Abstract
Linear antenna arrays are synthesized to have maximum directivity for a specified beamwidth. The directivity is maximized subject to a given beamwidth such as null to null or half power one. The excitation currents are obtained using a matrix equation obtained from the Lagrange multiplier method. The performance of the proposed method is studied by means of some examples. The synthesized arrays have the pre-specified beamwhidths and their directivity is close to the number of elements.
K. Fertas, F. Fertas, S. Tebache, A. Mansoul, R. Aksas,
Volume 18, Issue 3 (9-2022)
Abstract
In this paper, a frequency switchable antenna design using genetic algorithms (GAs) for dual band WiMAX (3.5GHz) and WLAN (5.2GHz) applications is proposed. The area of the radiating patch element is divided into 2 mm square cells, with each cell assigned a conducting or non-conducting characteristic. To realize frequency reconfiguration, switches are incorporated into appropriate locations to activate/deactivate corresponding cells. The on/off states of the switches are represented by the presence or absence of conductor, respectively. Hence, the proposed approach allows the antenna to operate as mono-band or dual-band radiator according to the desired application. Further, measurements and simulations are carried out and a reasonable agreement is achieved.
P. Paliwal,
Volume 18, Issue 4 (12-2022)
Abstract
This paper presents a multi-stage planning framework for analysis of stochastic distributed energy resources (DERs) comprising of solar, wind, and battery storage. The existing models do not consider penetration level analysis in conjunction with sizing, placement, and economic assessment. The main objective of this research is to embed all these dimensions of system planning in one structure. The first stage involves reliability constrained component sizing. The second stage pertains to placement of DERs based on loss minimization and voltage profile. The third stage is the main thrust of this work which provides exhaustive economic evaluation and cost-benefit analysis. The novelty of this work lies in the consideration of penetration level in backdrop of all three stages. The proposed formulation is implemented on a 33-Bus radial distribution feeder located in Jaisalmer, Rajasthan, India. Four penetration levels viz. 10, 20, 40, and 60 percent have been investigated and analyzed under different planning scenarios. The results facilitate the determination of optimum penetration level.
N. Thakkar, P. Paliwal,
Volume 18, Issue 4 (12-2022)
Abstract
In the last decade, there has been a lot of focus on sustainable development in the electrical power industry to meet the growing energy demand. This has led to an increase in the integration of renewable energy sources (RES). In addition to being abundantly available, the RES offers advantages such as low environmental impact and increased social development of rural communities which are imperative for a sustainable society. However, the selection of a particular generating resource or resource mix (RM) for an autonomous micro-grid is a complex problem that involves multiple conflicting factors. In this paper, a planning strategy for selecting an appropriate RM has been proposed. Seven RMs comprising different combinations of four generation/storage technologies such as solar photovoltaic array (SPVA), wind turbine (WT), diesel generator (DG) and battery storage (BS) have been considered. The planning is initiated with the determination of optimal component sizing for all seven RMs. The RMs are then analyzed with respect to four primary sustainability parameters i.e. economic, social, technical and environmental. The analysis is further enhanced by investigation of 13 sub-parameters as well. Thereafter, prioritization of RMs is carried out using two MCDM methods: Best worst method (BWM) and PROMETHEE II. Finally, to assert the importance of weight assignment on RM ranking, sensitivity analysis is performed. In order to impart the practical aspect to analysis, the planning formulation is applied to a case study of the Thar desert, India. The results suggest that a combination of SPVA and BS provides the most optimum RM solution.
Shankarshan Prasad Tiwari,
Volume 18, Issue 4 (12-2022)
Abstract
In modern infrastructure, the demand for DC power-based appliances is rapidly increasing, and this phenomenon has created a positive impact on the acceptance of the DC microgrid. However, due to numerous issues such as the absence of zero crossing, bidirectional behaviour of sources, and different magnitudes of fault current during grid connected and islanded modes of operation, protecting DC microgrid remains a difficult task. Apart from these challenges, intermittent conditions are also a major challenge. Under such type scenarios, shadow conditions in the solar based DERs will reduce the desired output of the solar panels simultaneously in wind based DERs will be affected due to the low pressure of air. In this type of circumstances threshold setting based overcurrent relays may fail to sense the operational dynamics of the system. Therefore, in this manuscript, an ensemble of decision tree-based protection scheme is proposed to provide immunity against the stochastic conditions under the varying natures of the fault resistance. A total of 7150 test cases have been considered for validation of the protection scheme and all modules have been tested.
A. O. Issa, A. I. Abdullateef, A. Sulaiman, A. Y. Issa, M. J. E. Salami, M. A. Onasanya ,
Volume 19, Issue 3 (9-2023)
Abstract
Grid-connected photovoltaic (PV) system is often needed whenever utilities fail to provide consumers with a reliable, sufficient and quality power supply. It provides more effective utilization of power, however, there are technical requirements to ensure the safety of the PV installation and utility grid reliability. In solar systems there is often excessive use of components, resulting in high installation costs. Consequently, appropriate measures must be taken to develop a cost-effective grid-connected PV system. An optimally sized PV system incorporated into an existing unreliable grid-connected commercial load for Mount Olive food processing is presented in this paper. The study focused on providing a reliable electricity supply which is cost-effective and environment-friendly. The techno-economic analysis of grid-connected PV/Diesel/Battery Storage systems was carried out using HOMER Pro software. Results showed that Grid/PV/BSS are technically, economically and environmentally feasible with the cost of energy at 0.136$/kWh and net present cost at $254,469. Also, the excess electricity produced by this combination is 13,264kWh/year, which generates income for the company by selling excess generated energy back to the grid if net metering were to be implemented. Furthermore, the CO2 emissions for these combinations decreased to 10,081.6 kg/year as compared to the existing systems (Grid/Diesel Generator) with emissions of 124,480 kg/year. This is an additional advantage in that it improves the greenhouse effect. A sensitivity analysis was carried out on the variation of load change, grid power price and schedule outages for the optimal system.
S. Prasad Tiwari,
Volume 19, Issue 3 (9-2023)
Abstract
In spite of the numerous benefits over the traditional power distribution system, protection of the microgrid is a challenging and complex task. The varying fault resistances due to dissimilar grounding conditions can affect the performance of the protection scheme. Under such conditions, the magnitude of the fault current can vary from lower to higher level. In addition to the above, the dissimilar magnitude of fault current during grid connected and islanded mode demands a protection scheme that can easily discriminate the mode of operation. The magnitude of fault current in grid-connected and islanded modes needs a robust protection scheme. In this regard, an ensemble of subspace kNN based robust protection scheme has been proposed to detect the faulty conditions of the microgrid. The tasks of the mode detection, fault detection/classification as well as faulty line identification has been carried out in the proposed work. In the proposed protection scheme, discrete wavelet transform (DWT) has been used for processing of the data. After recording the voltage and current signals at bus-1, the protection scheme has been validated. The validation of the protection scheme in Section 6 reveals that the protection scheme is efficiently working.
Atefeh Sohrabi, Hamideh Dashti, Javad Ahmadi-Shokouh,
Volume 19, Issue 4 (12-2023)
Abstract
In this article, an active electrically small Horn antenna for very high frequency (VHF) and ultra-high frequency (UHF) frequencies is presented. The proposed horn antenna has a height of 5 cm and a diameter of 4.28 cm which can cover 6-12 GHz without a special active circuit with the VSWR of less than 2. A Non-foster Active Adaptation Circuit is used to reduce the antenna input frequency from 164 MHz to 880 MHz. Good matching is visible between the simulation results and the measurement of the antenna reflection coefficient with the active matching circuit. The proposed structure has more than 137 % bandwidth. With the proposed active antenna, the problem of non-portability of VHF and UHF Horn antenna antennas has been solved. Finally, by analyzing the time domain, the stability of the circuit is examined, and the results of the stability test show that the system, including the antenna and the circuit, is stable. The antenna and the matching circuits are simulated by CST microwave studio and advanced design system, respectively.
Ayotunde Abimbola Ayorinde, Sulaiman Adeniyi Adekola, Ike Mowete,
Volume 19, Issue 4 (12-2023)
Abstract
This paper, using the circuit-geometric features of the Method of Moments (MoM), presents a comprehensive analytical treatment of an exponentially non-uniform helical antenna (ENH), mounted on a ground plane of finite extent. Earlier investigations reported in the literature established that the introduction of an exponential non-uniformity in the turns spacing of an otherwise uniformly wound helical antenna significantly improves its axial ratio and power gain profiles, but failed to address two important questions; one concerning the influence of the degree of non-uniformity on the antenna performance: and the other, the associated return loss profile, which is of particular importance in practical applications. It is shown in this paper, that when a properly designed impedance matching circuitry is introduced, a return loss of the ENH of close to 60 dB is achievable; without compromising axial ratio and gain performances. Indeed, axial ratio bandwidth remained unchanged at 54.55% for both the impedance-matched and unmatched ENHs, whilst maximum gain changed marginally from 14.19dB, for the unmatched ENH to 14.18dB for the impedance-matched antenna.
