Iranian Journal of Science and Technology-Transactions of Electrical Engineering最新文献

A new non-isolated high-gain high-efficiency interleaved DC–DC converter with low voltage stress is introduced in this paper, which is suitable for renewable energy sources applications. It utilizes coupled inductor (CI) and built-in transformer (BIT) to achieve an ultra-step-up voltage ratio. In such a case, a more flexible voltage gain is provided through the turn ratios of CI and BIT. Through the interleaving effect, the input current ripple is minimized and also equal current sharing performance is realized between the interleaved phases. Moreover, the implementation of low voltage MOSFETs is facilitated by reducing the voltage stress across which consequently decreases the conduction losses. Meanwhile, the leakage inductances of the magnetic devices provide zero current switching of the semiconductors, and reverse recovery losses of diodes are diminished, as well. Finally, a 1 kW 20–400 V prototype is fabricated to examine the conducted steady-state analysis and to demonstrate the merits of the proposed converter.

This paper concentrate on an option for mitigating distributed denial of service (DDoS) attacks that can stern consequences in mobile ad hoc network (MANET). Discovering a solution to a DDoS attack has gained research focus but challenges exists in performing attack detection with high accuracy along with developing a mechanism in detecting diverse methods to classify DDoS attack activities and also to classify it as an effective measure. The existing methods have numerous difficulties involving detection system performance limits, system scalability and stability, and the capability to develop large volumes of information. This paper concentrates on ETC with randomized search algorithm to detect attacks categorized as flooding, scheduling, black holes and gray holes, using a machine learning (ML) technique as classifier for understanding the behavior of these attacks and trains the better classification method in the MANET data transmitting dataset. The ETC algorithm employs the traditional top-down construction method to construct an ensemble of unpruned decision or regression trees. It separates nodes by selecting cut points thresholds completely at random, which sets it apart from previous tree-based ensemble approaches. When the data transmitted in the AODV, the behavior of node is analyzed and reported in the dataset as target which is trained through ML method. This AODV with ML proposed model can justify the behavior of network in MANET and classify the attack type for the current application. Moreover, the ML method performance has been developed through hyperparameter tuning which can be evaluated through confusion matrix metrics. This AODV with extra tree classifier (ETC) generate improved accuracy as 98.89% using hyperparameter tuning process in determining the safe data transaction in MANET.

The purpose of low voltage ride through the requirement for utility-interactive type inverters like microinverters, string inverters, and central inverters is to maintain the grid stability, power loss reduction, voltage support/boost by reactive power support during sudden fluctuations in grid voltage. In this paper, the performance of solar PV-based grid-connected central inverters of 350 kW is evaluated during its operation of low voltage ride through (LVRT), high voltage ride through (HVRT), and frequency ride through (FRT). The evaluation is based on “Technical Standards for grid connectivity,” published by CEA, India, in February 2019. The inverter is evaluated at a power of 350 kW using the grid simulator of the 540 kVA facility available at the CPRI laboratory. The LVRT, HVRT, and FRT results show that this central inverter can qualify for the fault ride-through requirements mentioned in the CEA Regulations 2019. This paper also shows the gaps in the standard for evaluating the fault ride-through in an inverter and recommends a few suggestions that need improvement to make the standard more stringent and clearer. Finally, the proposed recommendations' industrial implications and limitations are provided in the conclusion section.

Multi-Level Inverters (MLIs) are the most promising and significant applications in grid-connected renewable energy systems. This research article proposed a novel 7-level MLI with fewer switches that produce the voltage levels required for photovoltaic (PV) applications using hybrid Harris-Hawks Optimization with the Particle Swarm Optimization (HHO-PSO) algorithm. Modulation techniques play a vital role in MLI filtering output voltage harmonics. The Selective Harmonic Elimination (SHE) modulating methodology has been used in this research. This SHE method eliminates the lower-order harmonics by the hybrid HHO-PSO technique,which generates the optimized switching angles. The proposed MLI topology is developed and validated by comparison with other recent 7-level MLI topologies. The PSO, HHO, and hybrid HHO-PSO algorithms are developed in Matlab using m-file coding, which produces the optimized switching angle. Total Harmonic Distortion (THD) analysis on the inverter outer voltage has been carried out, and the results are briefed. The simulation results show that the suggested HHO-PSO approach can yield superior performance with low total harmonic distortion compared to existing approaches. The experimental results for the proposed MLI provide lower THD (2.82%) and minimum switching losses compared to the conventional PSO and HHO algorithms.

Despite of being a cleaner energy resource, the solar photovoltaic (SPV) system faces the dynamic and unpredictable changes in environmental conditions; hence, conventional and extant maximum power point tracking (MPPT) methods can get stuck at local minima. However, on account of less switching strain on the DC–DC converter, the drift-free P&O MPPT method can be supervised with effective bio-inspired metaheuristic algorithms to maximize its robustness and efficiency to generate photovoltaic power. Therefore, in this paper, the efficiency of the drift-free P&O MPPT method is significantly enhanced using a grey wolf skill embedded levy flight optimization (LI-GWO) method as a new approach. Firstly, a single-ended primary inductor converter (SEPIC)-based grid-connected SPV system is modeled to assess the MPPT performance. Further, using the LI-GWO enhanced drift-free P&O algorithm, the duty cycle of the SEPIC is regulated by updating the position of the grey wolfs based on the Brownian motion of the levy flights. Moreover, the exploration, exploitation and convergence analysis are carried out to examine the effectiveness of the proposed LI-GWO + drift-free P&O algorithm. In this manner, the proposed algorithm attains the global maxima quickly and, thereafter, the global MPP (GMPP) is tracked by the drift-free P&O itself with the less switching strain. The performance of the proposed MPPT approach is compared with the other conventional and hybrid metaheuristic-based MPPTs to show effectiveness under the newly formulated extreme weather condition model.

This research introduces a novel dual-frequency microstrip patch antenna (MPA) design that features orthogonal slant linear polarizations and a wide frequency ratio (FR) range. A truncated square patch is employed to realize dual-band operation under TM₁₀ and TM₀₁ modes. Both modes are excited along diagonals of the square MPA leading to orthogonal slant polarizations. A shorting pin is loaded underneath the radiator to suppress TM₂₀ mode at the intermediate frequency. Simulated single-feed excitation demonstrates an arbitrary FR between 1.04 and 2.5. In order to confirm the feasibility of the suggested approach, an example of the antenna prototype with an FR of 2 is implemented and tested. Experimental results demonstrate that the antenna successfully achieves dual-band operation with a gain of 4.8 dB and 7.8 dB at 2.7 and 5.4 GHz, respectively, using probe excitation. This approach yields a marginal gain reduction of 0.8 dB at lower frequency when compared to a conventional MPA resonating at the identical frequency. The level of cross-polarization is less than − 20 dB at two frequencies. The proposed antenna stands out for its lightweight and low-profile design, wide FR range, low cross-polarization, stable unidirectional radiation pattern, simple structure and ease of fabrication, making it an ideal choice for dual-band applications.

In this paper, we present a new optimization method to estimate the parameters and torques of an induction motor (IM). The proposed method is known as the Vortex Search Algorithm (VSA), whose performance is based on the behavior of the vortices created by stirred fluids. This algorithm was compared with other four optimization methods reported in the specialized literature (grasshopper optimization algorithm, particle swarm optimization, salp swarm algorithm and sine cosine algorithm), and its solution quality, precision, and robustness were validated using two test motors. During the tests, we analyzed the minimum error between the estimated values and the values provided by the manufacturer, as well as the global error of each method and their required processing time. The results show that the VSA is an excellent alternative to estimate the parameters of an IM, as it exhibited the best performance when compared to the other optimization methods.

The analysis of outage performance in a Non-Orthogonal Multiple Access (NOMA) based network is conducted for a hybrid model that combines an IRS with a decode-forward relay. The use of an IRS-assisted relay network is particularly significant in environments with deep fading. The outage performance of each user in different ordered NOMA configurations has been evaluated, taking into account different numbers of IRS elements. The optimal number of users that can be accommodated by a source using NOMA for a specific threshold has been identified. The required number of active reflecting elements has been estimated to achieve a target SINR for a given order of NOMA. Additionally, a closed-form expression and its asymptotic expressions have also been derived for the outage probability of all users. The analytical results have been validated via Monte Carlo simulations.

In this work, a novel compact antenna with a super-wideband (SWB) feeding (3–43 GHz) is designed. The SWB lens antenna consists of a super-wideband feeding, a parallel plate waveguide (PPW), and a dielectric lens. The flat Luneburg lens has been designed and implemented based on metasurface technology. This antenna can be employed as a sense antenna in ultrawideband (UWB) applications. Attaining a SWB antenna that also grants a high gain in the whole bandwidth is a major issue considered in this work. The introduced structure reveals a very good matching properties (VSWR < 2.15) and also acceptable gain (5–13.5dBi) and very good efficiency (typ. > 83%) in the whole ultrawide bandwidth (3–43GHz). Another important feature of the proposed structure is its capability for being used in multi-beam applications by merely adding some extra feeding ports to it. To show this, the designed lens is fed by three ports placed on its circumference with 30° angular separation. These results show three beam directions in − 30°, + 30°, and 0°, and in addition to its broad bandwidth, excellent impedance matching and close-to-ideal port isolation are achieved.