Iranian Journal of Electrical and Electronic Engineering
Volume:18 Issue: 1, Mar 2022

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.

This paper scrutinizes the impact of different renewable energy sources (RES) development policies on competitiveness within multiple electricity markets (MEMs). Also, the variation in market power indices by increasing the integration of the markets undergoing symmetric and asymmetric RES development policies is investigated. To do so, several stochastic mixed-integer non-linear programming objective functions are used in the agent-based simulation framework to model the power plants’ behavior and markets. The case study shows in the low RES penetrated markets, one can say the more integration level of the markets, the lower potential of exercising market power. The reciprocal judgment is true for a high RES penetrated market. Also, large asymmetry in RES development between markets within MEMs may bring about market power problem for a high RES penetrated market. Unlike the asymmetric RES development policies, adopting homogeneous policies in RES development within MEMs reduces the market power potential in all markets and this potential decreases with the increase in the integration of the markets.

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.

Moisture in the transformer insulation can shorten its life. There are many methods for detecting humidity in transformer paper insulation. One of the methods used in the factory to evaluate the drying process of transformer insulation and determine its humidity is the frequency response analysis method. In this paper, the desired experiments are performed on different transformers, and after obtaining the results of frequency response measurements, the required features are extracted from them. Then, using the k-means method, these features are placed in three clusters (dry, wet, and excessively wet). The cost function of the k-means method is optimized using the particle swarm optimization (PSO) algorithm to get a better result. By applying new data from different transformers, the capability of the proposed method in determining the moisture content of the transformer is evaluated. The results obtained from the evaluation of the insulation condition of another group of transformers indicate the high accuracy of the proposed method.

In recent years, the increasing of non-dispatchable resources has posed severe challenges to the operation planning of power systems. Since these resources are random in nature, the issue of flexibility to cover their uncertainty and variability has become an important research topic. Therefore, having flexible resources to cover changes in the generation of these resources during their operation can play an essential role in eliminating node imbalances, system reliability, providing the required flexible ramping capacity, and reducing system operating costs. Among flexibility resources, there are quick-act generation units such as gas units that can play an important role in covering net load changes. Also, on the demand side, the optimal design of demand response programs as responsive resources to price and incentive signals, by modifying the system load factor can prevent severe ramps at net load, especially during peak load hours, and as a result, increase system flexibility while decreasing operational cost of the power system. In this paper, unlike the existing literature, the effect of the mentioned flexibility resources (both on the generation side and the demand side) in day-ahead operation planning under high penetration of wind generation units has been studied on the IEEE RTS 24-bus test system. Also, for this scheduling, a mixed-integer, two-stage, and tri-level adaptive robust optimization have been used, which is solved by column-and-constraint generation decomposition-based algorithm to clear the energy and ramping capacity reserve jointly.

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.

One of the significant concerns in the MTDC systems is that voltage source converters (VSCs) do not hit their limits in the post-contingency conditions. Converters outage, DC line disconnection, and changeable output power of wind farms are the most common threats in these systems. Therefore, their destructive impact on neighboring AC systems should be minimized as much as possible. The fixed droop control is a better choice than others to deal with this, although it also has some limitations. Accordingly, a novel centralized droop-based control strategy considering N-1 contingency is proposed in this paper. It prevents converters from exceeding their limits while causes optimal power sharing and minimum DC link voltage deviation immediately, without secondary control layer. It also utilizes maximum wind power without curtailment. These properties improve the performance of the MTDC system in post-contingency conditions. The effectiveness of the proposed control method is validated by simulation of a 4-terminal VSC-MTDC system in MATLAB/Simulink R2016a.

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.

There are two serious issues regarding gait recognition. The first issue presents when the walking direction is unknown and the other one presents when the appearance of the user changes due to various reasons including carrying a bag or changing clothes. In this paper, a two-step view-invariant robust system is proposed to address these. In the first step, the walking direction is determined using five features of pixels of the leg region from gait energy image (GEI). In the second step, the GEI is decomposed into rectangular sections and the influence of changes in the appearance is confined to a small number of sections that could be eliminated by masking these sections. The system performs very well because the first step is computationally inexpensive and the second step preserves more useful information compared to other methods. In comparison with other methods, the proposed method shows better results.

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.

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.

The need for low-power VLSI chips is ignited by the enhanced market requirement for battery-powered end-user electronics, high-performance computing systems, and environmental concerns. The continuous advancement of the computational units found in applications such as digital signal processing, image processing, and high-performance CPUs has led to an indispensable demand for power-efficient, high-speed and compact multipliers. To address those low-power computational aspects with improved performance, an approach to design the multiplier using the algorithms of Vedic math is developed in this research. In the proposed work, the pre-computation technique is incorporated that aided in estimation of the carries during the partial product calculation stage; that enhanced the speed of the multiplier. This design was carried out using Cadence NCSIM 90 nm technology. The comparative analysis between the proposed multiplier design and the multipliers from the literature resulted in a substantial improvement in power dissipation as well as delay. The research was extended to assess the designed architectures’ performance statistically, applying the independent sample t-test hypothesis.

The paper presents the steady-state analysis of a new hybrid synchronous machine with a higher reluctance to excitation power ratio. The machine comprises a round rotor and a salient-pole machine elements that are mechanically coupled together and integrally wound. In each stator, there are two sets of identical poly-phase windings identifiable as the primary and secondary windings which are electrically isolated but magnetically coupled. The primary windings are connected in series between the two sections of the hybrid machine while the secondary windings are connected in anti-series and terminated across a balanced capacitor bank. The hybrid machine exhibits a special feature that when running at the synchronous speed, its effective XD/XQ ratio can be amplified and hence its output by the tuning of the variable capacitance bank which capacitive reactance XC neutralizes only the quadrature axis reactance XQ while the direct axis reactance XD remains unaffected. It is shown that at XD/XQ = 3, the reluctance component of the output power is 2.5 times the excitation power. The calculated and the measured results from the machine are in good conformity.