Amirkabir International Journal of Electrical & Electronics Engineering
Volume:54 Issue: 2, Summer-Autumn 2022

Perovskite solar cells (PSCs) are the brilliant stars of new generation photovoltaic technologies due to their superior features of perovskite material and high power conversion efficiency (PCE) that has reached up to 25.5%. For the commercialization of PSCs, their stability is the main challenge that should be addressed. The perovskite structure is decomposed to its precursor in the face of continuous light irradiation (mainly UV light), humidity, and heat. In this work, mesoporous PSCs with structure of FTO (400 nm)/ Compact TiO2 (30 nm)/ Mesoporous-TiO2 (330 nm)/ CH3NH3PbI3 (270 nm)/ P3HT (30 nm)/ Au (100 nm) are fabricated in uncontrolled environment. The UV light stability of the PSC is enhanced by adding a photoactive phase change material (PCM) into the perovskite. The PCM undergoes trans-to-cis isomerization under UV light irradiation. Then, the cis form absorbs the heat produced in the solar cell and converts it into its trans isomer in a reversible process. By this approach, the destructive effect of UV light and heat is prohibited, leading to the enhancement of PSC durability by almost 2.4 times compared to devices without PCM. Indeed, the PCE of the device with AzB reaches 67% of the initial PCE upon 120 min of light soaking under AM 1.5, while the device without AzB only keeps 28% of its initial PCE under the same condition. It should be noted that there is no significant difference in the PCE of both solar cells.

This paper presents a mathematical model for the distribution network (DN) expansion planning to increase the penetration of photovoltaic (PV) energy sources in the distribution network. The presented model determines the optimal place of PVs in coordination with energy storage systems (ESS). It also identifies the optimal power generation of PVs as well as the optimal amount of energy that must be purchased from the upstream utility grid. The aim of this optimization problem is to maximize the penetration capacity of PVs such that the technical constraints of the distribution network are satisfied. The proposed optimization problem is formulated as a mixed-integer nonlinear programming (MINLP) problem and is solved using the SBB solver under GAMS. The uncertainties associated with PV production and electricity demand are modeled by generating different scenarios. The K-means clustering technique is used to reduce the number of scenarios to make the problem tractable. The effectiveness of the presented model is verified on a standard IEEE 33-bus distribution system. The numerical results show that using ESS capabilities, on-load tap changer (OLTC), and PVs’ reactive power production capability for controlling voltage profile, increase the hosting capacity of PVs and improves the voltage profile, thereby decreasing the total investment and operation costs.

Neuromarketing assists us to uncover the subconscious effects of marketing stimuli on consumers' brains from a neuroscientific perspective. One of the important effects of brands on humans’ brains is in the level of directed relations between brain areas which was less considered in neuromarketing studies. In this paper, we used the EEG signals recorded during the confrontation of participants to the brands in the virtual shopping center. 20 participants (10 female and 10 men) were contributed to the experiment. After preprocessing, extracted brain sources were clustered to brain areas. Effective connectivity between brain areas was calculated using the generalized partial coherence (GPDC) index in four different states of watching brands (1. unfamiliar and undesired brands 2. familiar and undesired brands 3. unfamiliar and desired brand 4. desired and familiar brands). Statistical analysis of these states showed in watching familiar brands almost all of the brain areas have a stronger relation to each other. In watching unfamiliar brands, between hemispheric relations are stronger when brands are desired, and interhemispheric relations are stronger when brands are not desired. Also, in watching familiar brands, left-brain relations are stronger when the brands are desired and right-brain relations are stronger when the brands are undesired. As the brands were shown for 2 seconds, the connectivity values in 1st second and 2nd second of watching brands don’t have significant differences.

A new miniaturized antenna that covers the industrial scientific medical (ISM) band 2.4-2.483.5 GHz is designed. The implantable antenna system consists of a rectangular patch with coaxial feed and Y slots. The compact size of the recommended antenna is 8 × 8 × 1.27 〖mm〗^3. A shorting pin is used for miniaturization. In the proposed antenna, simulated −10 dB bandwidth is about 160 MHz. Enhanced bandwidth (2.39-2.55 GHz) operation can be achieved by introducing ground slots and moving feed and pin at the appropriate position. In a flat type implantable system, the antenna is capsulated with battery and electronic boards. The result was verified by CST software in both heterogeneous multi-layer (skin, fat, and muscle) and homogenous single layer (skin, muscle, stomach, small intestine, and colon) human tissue phantoms. To diagnose the effect of fabrication tolerance and dimensions of slots on impedance and bandwidth, the antenna is parametrically analyzed. For safety consideration and effects of EM radiation on the human body, the antenna’s specific absorption rate (SAR) is computed. The main features of the designed antenna are the gain value of -15.8 dBi, low SAR, small volume and large bandwidth that make the proposed antenna an appropriate choice for implantable medical devices. The designed implantable antenna features have been compared with previously reported antennas.

The decentralized control of a multi-agent system with leader-follower consensus is investigated. Thesystem is formulated in graph theory, and a general configuration for L-F formation is proposed. The goalfor the formation is defined to track the predefined trajectory in the presence of high-frequency noise. Thecontroller for the system is proposed on the basis of a model predictive-based controller. Differentscenarios for a multi-agent system are considered, which lead to the linearization of the plant; meanwhile,External structured disturbances are considered in the system. The novelty of the present paper addresses the gap between the optimal controllers and robust controllers. The robustness of optimal controllers isnot verified in the optimality of MPC controllers. Thus a tube MPC theory is proposed to increase therobustness of the interacting noise system. consequently, the optimal controller, maintains robust throughout the existence of external disturbances and high frequency noises. Meanwhile, the closed-loop multi-agent response is investigated in the presence of external bounded disturbances. Next, The Hybrid controller is designed for the formation. The switches take place between MPC and Tube-MPC controllers for each agent. On the other hand, hard constraints on control input and its variations and soft constraint on graph structures and topology of the multi-agent system are submitted. At length, the stability proof is considered for the closed loop multi-agent system. Finally, the simulation results demonstrate the formation results and the proposed controller can also satisfactorily deal with the high-frequency noise with hard and soft constraints.

Flexible AC transmission system devices can function efficiently, powerfully and economically in congestion management through the control of the lines transmission power and the voltage of the power systems buses. However, the congestion management of power systems may affect the transient stability or network voltage stability and also reduce the system security. Therefore, constructing congestion management requires the consideration of power system stability. In this paper, a multi-objective Fuzzy structure is employed so as to obtain the optimal locating and sizing of unified power quality conditioner-phase angle control for the congestion management so that it optimizes total operating cost, voltage and transient security. In order to achieve the above goals, unified power quality conditioner-phase angle control placement has been performed using Fuzzy method. Using Fuzzy inference system, triple objective functions are expressed in terms of a single objective function and optimized with the Harmony search algorithm. To illustrate the effectiveness of the proposed approach, this method is implemented in MATLAB software for the congestion management of England's new network with 39 buses. The results indicate that using the proposed method, congestion management is done optimally, which not only does not reduce system security, but also increases the its security margin.

Electromagnetic susceptibility (EMS) of a power amplifier (PA) against an interfering wave is presented. The interfering waves affect the performance of any circuit, either intentionally or from adjacent equipment. In the case of power amplifiers, this phenomenon can overdrive the PAs into the nonlinear region and if the interfering wave still exists, it can damage the PA. Therefore, circuit designers must design the circuit to be not susceptible to interfering waves, as much as possible. In this article, EMS analysis of a PA against an interfering Gaussian modulated pulse with the 3D finite difference time domain (3D-FDTD) method is presented. In this method, the transistor is replaced with an appropriate transistor nonlinear large-signal EEHEMT circuit model, and the whole circuit of the PA including the transistor circuit model, matching networks, and biasing circuits is simultaneously analyzed in the presence of radiated and conducted interferences. This method gives more accurate results than the hybrid methods that analyze the active and passive parts of the amplifier separately. This method is applied to a designed PA with Wolfspeed’s CGHV1J006D discrete GaN on SiC high electron mobility transistor (HEMT) and a hybrid method is proposed to validate the results. The results show a good agreement between the proposed and the validation method.

The microgrid power system has a nonlinear dynamics with many uncertainties such as changes in wind power and solar irradiation. in other words, the main challenges in microgrids are the presence of disturbances. Sustaining such a system requires a robust approach. In this paper in order to deal with this problem, the properties and concepts of multi-agent systems are used to model the microgrid power system as this system has seven agents, all of which have a common point the production-consumption power. Then, the design and implementation of cooperative control of the microgrid agents' output power are discussed. Due to the fact that in the multi-agent modeling structure, each agent is related only to its neighbor agent, so the designed controller is of decentralized or distributed type. Among the advantages of this distributed structure is the ability to adapt immediately and be resistant to uncertainties in the system. In addition, the advantages of the Lyapunov function in the cooperative control structure have been used in order to overcome the disturbances and uncertainties in the structure of the microgrid and to ensure the stability of the system. Ultimately, the control law designed for the seven-factor model in Matlab software is simulated and compared with similar previous methods.

In this paper, a new structure of an Empty Substrate Integrated Waveguide (ESIW) H-plane Horn Antenna with improved gain and impedance bandwidth is introduced. Using ESIW technology, by removing the dielectric material of the SIW structure, the dielectric loss is eliminated and in turn, antenna gain is improved. The flaring area of the ESIW horn is also divided into a few rectangular waveguide sections with proper length and width to improve its impedance bandwidth. Moreover, adding radiating slots significantly reduce Half Power Beamwidth (HPBW) of the E-plane pattern of the ESIW horn. In addition, by adding a slot array at the right position of the structure, the radiating fields of both the horn aperture and the slot array are properly combined and in turn, radiation performance of the ESIW horn is improved. Also, by adding non-radiating slots on both sides of the structure, impedance bandwidth is significantly enhanced. The most important feature of the proposed horn antenna is its two-dimensional (2-D) structure, while both gain and impedance bandwidth are improved. The introduced horn antenna is successfully simulated by High Frequency Structure Simulator (HFSS) software and the results are verified by CST. The obtained results show that it provides 14.1 dBi gain with 98% radiation efficiency and 11.3% impedance bandwidth over the frequency range of 25.5 GHz up to 28.5 GHz.

This study addresses the distributed fault estimation control problem for linear multi-agent systems with an event-triggered communication mechanism. In multi-agent systems, a substantial challenge is to find out the size and the shape of the occurred faults and then how to reduce the wastage of communication bandwidth and unnecessary executions. In order to address these concerns, we proposed a distributed fault estimation observer where each agent employs an augmented system based on a predefined communication graph, and with consideration of its neighbors, to estimate the fault and states both in itself as well as its neighbors, simultaneously. In addition, in this approach, an event-triggering scheme was implemented in order to effectively reduce unnecessary signal transmission between the agents and attain a reasonable allocation of resources. Sufficient conditions are presented to guarantee that the closed-loop system is asymptotically stable with prescribed disturbance attenuation, and the parameter matrices of the event-triggered mechanism and observer can be obtained simultaneously by solving a set of linear matrix inequities (LMIs). Eventually, some simulations are included to demonstrate the performance of the introduced fault estimation and effectively of the event-triggered mechanism. . ------- --------- - - - -- - - - -- - - - -- - - -- - - -- - - - - - -

Appropriate power quality is indispensable for electrical distribution networks especially in microgrids including renewable energy sources. One of the critical issues affecting power quality is the unbalanced voltage. Voltage imbalance in microgrids spreads due to proximity of loads and power sources, causing instability and eventually interruption. In general, unbalanced voltage can be compensated by using reactive power compensators, e.g. series active power filter and dynamic voltage restorer. However, these equipment imposes additional costs, which is not economically viable. Recently, the surplus capacity of inverter-interfaced distributed generations is used to improve voltage quality. In this regard, the control methods based on proportional-resonance controllers in αβ frame or PI controllers in a dual-frame synchronous reference frame (DSRF) are the usual methods that are used. The problem of limiting the output current in αβ frame and the problem of oscillating components in DSRF are weakness of these methods. To resolve the mentioned drawbacks, in this paper a control method based on decoupled double synchronous reference frame (DDSRF) is proposed for unbalanced voltage compensation using a two-stage grid-connected photovoltaic system. The simulation results show that despite the dynamic changes and the alternating nature of the photovoltaic system in power generation, the proposed control system appropriately compensates the unbalanced voltage and controls DC link voltage and the photovoltaic output power. After compensation using the proposed control strategy, the voltage unbalance factor (VUF) and the total harmonic distortion (THD) at the PCC are under the permissible range accounting for two percent and five percent, respectively.