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The present study aims at analyzing and assessing the performance of grid-connected photovoltaic (PV) systems, where the considered arrangement is the two-stage PV system. Normally, the maximum power point tracking (MPPT) process is utilized in the first stage of this topology (DC-DC). Furthermore, the active and reactive power control procedure is accomplished in the second stage (DC-AC). Different control strategies have been discussed in the literature for grid integration of the PV systems. However, we present the main techniques, which are considered the commonly utilized and effective methods to control such system. In this regard, and for MPPT, popularly the perturb and observe (P&O) and incremental conductance (INC) are employed to extract the maximum power from the PV source. Moreover, and to improve the performance of the aforementioned methods, an adaptive step can be utilized to enhance the steady-state response. For the inversion stage, the well-known and benchmarking technique voltage-oriented control, the dead-beat method, and the model predictive control algorithms will be discussed and evaluated using experimental tests. The robustness against parameters variation is considered and an extended Kalman filter (EKF) is used to estimate the system’s parameters. Future scope and directions for the research in this area are also addressed.

Sensorless strategies become very popular in modern control techniques because they increase the system reliability. Besides, they can be used as back-up control in case of sensor failure. In this paper, a DC-link sensorless control approach is developed, which is suited for grid-connected PV systems. The studied system is a two-stage PV scheme, where the DC–DC stage (boost converter) is controlled using an adaptive step-size perturb and observe (P&O) method. Further, the inverter control is accomplished by voltage oriented control (VOC). Generally, the VOC is implemented with two cascaded control loops, namely an outer voltage loop and an inner current loop. However, in this work, the outer loop is avoided and the reference current is generated using a losses model for the system. The losses model accounts for the most significant losses in the PV system. Moreover, particle swarm optimization (PSO) is utilized to compensate for the unmodeled losses. The PSO is executed offline for the purpose of calculation burden reduction. The proposed approach simplifies the cascaded VOC strategy and eliminates the DC-link voltage sensor, which in turn decreases the cost of the system. Finally, the proposed technique is compared with the conventional one at different atmospheric conditions and validated using MATLAB simulation results.

Maximum power point tracking (MPPT) techniques extract the ultimate power from the photovoltaic (PV) source. Therefore, it is a fundamental control algorithm in any PV configuration. The research in this area is rich and many MPPT methods have been presented in the literature. However, in the current study, we focus on the PV model-based MPPT algorithms. In this regard, the classification of this category can be mainly divided into curve fitting methods and techniques based on the mathematical model or characteristics of the PV source. The objective of the PV model-based MPPT algorithm is to allocate the position of the maximum power point (MPP). Thus, no searching efforts are required to capture that point, which makes it simple and easy to implement. Consequently, the aim of this study is to give an overview of the most commonly utilized model-based MPPT methods. Furthermore, discussion and suggestions are also addressed to highlight the gap in this area. The main methods from the literature are compared together. The comparison and evaluation are validated using an experimental hardware-in-the-loop (HIL) system, where high efficiency (more than 99%) can be obtained with a simple calculation procedure and fast convergence speed.

Maximum power point tracking (MPPT) is an essential and primary objective in photovoltaic (PV) systems implementation. Thus, in this article, the predictive fixed switching MPPT technique is proposed for a two-stage PV system, where the system under consideration consists of a PV source, boost converter, and two-level inverter. The MPPT design is based on dual adaptive step-size realization to limit the duty cycle oscillations at a steady state. Furthermore, the PI controller is eliminated, which simplifies the MPPT implementation. The suggested tuning procedure of the duty cycle is compared with the conventional adaptive step-size perturb and observe (P&O) method. The inverter is controlled using an efficient finite-set model predictive control (FS-MPC) algorithm with reduced computation burden, where the optimal switching state vector is identified based on the polarity of the reference voltage in the α-β reference frame and without any need for sector determination. Furthermore, the cost function of the FS-MPC algorithm is modified to include the reduction of the switching frequency as a secondary objective for the inverter control. The overall control methodology is evaluated using experimental results at different operating conditions.

Photovoltaic (PV) power systems are integrated with high penetration levels into the grid. This in turn encourages several modifications for grid codes to sustain grid stability and resilience. Recently, constant power management and regulation is a very common approach, which is used to limit the PV power production. Thus, this article proposes dual-mode power generation algorithm for grid-connected PV systems. The developed system considers the two-stage PV configuration for implementation, where the dual-mode power generation technique is executed within the DC–DC conversion (boost) stage. Most of the techniques adopted for dual-mode power operation employ the conventional perturb and observe method, which is known with unsatisfactory performance at fast-changing atmospheric conditions. Considering this issue, this study suggests a modified maximum power point tracker for power extraction. Furthermore, a new adaptive DC-link controller is developed to improve the DC-link voltage profile at different operating conditions. The adaptive DC-link controller is compared with the traditional PI controller for voltage regulation. The inverter control is accomplished using finite-set model predictive control with two control objectives, namely reference current tracking and switching frequency minimization. The overall control methodology is evaluated at different atmospheric and operating conditions using MATLAB/Simulink software.

In this paper, a finite control set model predictive control (FCS-MPC) for single-phase cascaded modified packed U-cell (MPUC) inverter is presented. The considered multilevel inverter (MLI) topology requires less number of switches and produces more levels in the output waveform compared to the conventional and recent ones. Two control objectives are achieved in the proposed control algorithm, reference current tracking and switching frequency minimization. The proposed FCS-MPC considers only the effective different vectors of the MPUC with eliminating the redundant states of the converter to reduce the computational effort of the algorithm. By minimizing a user-defined cost function, the developed FCS-MPC algorithm achieves low mean absolute reference tracking error of the grid current, high inverter voltage quality and low average switching frequency of the switches. The trade-off between the average switching frequency and the tracking performance with the voltage quality is studied to determine the suitable range of the weighting factor λ n for the proposed system. Simulation results are presented using MATLAB/Simulink to verify the effectiveness of the control system.

Predictive control provides many advantages over conventional control techniques. Thus, in this paper, a comparative study between the predictive direct current control (PDCC) and predictive direct power control (PDPC) is investigated. The study focuses on applying these control strategies with renewable energy systems (RESs), especially photovoltaic (PV) ones. RESs are integrated with high penetration into the grid, and they must satisfy certain regulations to sustain the grid stability. The studied system consists of a PV array and boost converter followed by two-level inverter to enable the grid connection, where the maximum power point tracking (MPPT) function is accomplished by an adaptive step-size method. The adopted technique here is perturb and observe (P&O) method. The control of active and reactive power is performed using PDPC and PDCC for the purpose of evaluation in terms of power quality, total harmonic distortion (THD), average switching frequency, implementation, calculation burden, etc. The system is validated by simulation results via Matlab platform under various operating conditions.

In this paper, an efficient finite control set model predictive control (FCS-MPC) for single-phase multilevel inverter (MLI) is proposed. The MLI topology under control reduces the number of the required semiconductor switches and produces more number of levels compared to traditional and recent topologies of MLIs. This topology has 49 different switching states, which means 49 predictions of the future current and 49 calculations of the cost function are required for each evaluation of the conventional FCS-MPC. Accordingly, the computational load is heavy. Thus, this paper presents a simplified FCS-MPC to reduce the calculation burden by computing the reference voltage and dividing the switching states of the MLI into two sets. Based on the reference voltage, one set is identified to determine the optimum voltage level. The proposed method does not require current predictions. Moreover, the number of cost function evaluations for each iteration is halved. As a result, the execution time is significantly reduced compared to that of the conventional FCS-MPC. The trade-off between the average switching frequency and the tracking performance is also investigated for the proposed scheme and compared to the conventional FCS-MPC. The effectiveness of the proposed solution in transient and steady state is verified by the simulation results.

This paper proposes a finite control set model predictive control (FCS-MPC) with a reduced computational burden for a single-phase grid-connected modified packed U-cell multilevel inverter (MPUC-MLI) with two control objectives: reference current tracking and switching frequency minimization. The considered competitive topology consists of two units with six active switches and two DC sources in each unit, allowing the generation of 49 levels in the output voltage, which is considered a significant reduction in the active and passive components compared to the conventional and recently developed topologies of multilevel inverters (MLIs). This topology has 49 different switching states, which means that 49 predictions of the future current and 49 calculations of the cost function are required for each evaluation of the conventional FCS-MPC. Accordingly, the computational load is heavy. Thus, this paper presents two reduced-complexity FCS-MPC methods to reduce the calculation burden. The first technique reduces the computational load almost to half by computing the reference voltage and dividing the states of the MLI into two sets. Based on the reference voltage polarity, one set is defined and evaluated to specify the optimal state, which has a minimal cost function. However, in the second proposed method, only three states of the 49 states are evaluated each iteration, achieving a significant reduction in the execution time and superior control performance compared to the conventional FCS-MPC. A mathematical analysis is conducted based on the reference voltage value to locate the three vectors under evaluation. In the second part of the paper, the sensitivity to parameter variations for the proposed simplified FCS-MPC is investigated and tackled by employing an extended Kalman filter (EKF). In addition, noise related to variable measurement is filtered in the proposed system with the EKF. The simulation investigation was performed using MATLAB/Simulink to validate the system under different operating conditions.

This paper presents a high-levels multilevel inverter (MLI) with a reduced number of the required switches. Forty-nine levels can be obtained in the output voltage from this circuit by usin...

In this article, a modified control structure for a single-stage three phase grid-connected photovoltaic (PV) system is presented. In the proposed system, the maximum power point tracking (MPPT) function is developed using a new adaptive model-based technique, in which the maximum power point (MPP) voltage can be precisely located based on the characteristics of the PV source. By doing so, the drift problem associated with the traditional perturb and observe (P&O) technique can be easily solved. Moreover, the inverter control is accomplished using a predictive dead-beat function, which directly estimates the required reference voltages from the commanded reference currents. Then, the reference voltages are applied to a space vector pulse width modulator (SVPWM) for switching state generation. Furthermore, the proposed inverter control avoids the conventional and known cascaded loop structure of the voltage oriented control (VOC) method by elimination of the outer PI controller, and hence the overall control strategy is simplified. The proposed system is compared with different MPPT techniques, including the conventional P&O method and other techniques intended for drift avoidance. The evaluation of the suggested control methodology depends on various radiation profiles created in MATLAB. The proposed technique succeeds at capturing the maximum available power from the PV source with no drift in comparison with other methods.

Bu çalışmada edebi roman alanında, yaratıcı Kürt yazarları arasında yer alan Abdulkerim Yahya Ez-Zibârî’nin romanlarında realizm ele alınmaktadır. Ez-Zibârî’nin romanlarına mükemmellik veren kullandığı sade ve akıcı Arapçadır. Yazarın romanlarından başka, yine Arapça olarak kaleme aldığı bazı kısa hikâyeler ve edebî eleştiri alanında birçok eseri bulunmaktadır. Yazar ulusal alanda birçok ödül kazanmıştır. Bunlardan biri Eşşarika Edebi Yaratıcılık ödülüdür. Bu çalışma yazarın iki romanı esas alınarak hazırlanmıştır. Uğniyât Et-tarîk İlâ Halepçe adlı romanında hayat realist bir bakış açısıyla ele alınmaktadır. Romanda yirminci yüzyıl başlarında, zorlu bir dönemde geçen Kürt toplumu ve diğer toplumlar ile bölgede yaşayan diğer milletler arasındaki yaşam imgelerinden bahsedilmektedir. Yazarın diğer romanı ise Şabbun ‘Arin Yahmilu Bundukiyyeteyn adını taşımaktadır. Bu romanda Irak’ın hem krallık hem de cumhuriyet dönemlerinde, zalim sistemler ve hükümetler altında acı çeken Kürt toplumunun yaşamından bahsedilmektedir. Bu romanlar, Irak’taki Kürt milletinin bu dönemlerde yaşadıklarını edebi bir bakış açısıyla yansıtmayı hedeflemiştir. Bu romanlarda Kürtlerin bölgedeki diğer Arap, Türk, Fars milletlerleriyle ilişkilerinden bahsedilmiştir. Bunun yanında bölgedeki aşiretlerin sıradan vatandaş üzerindeki zulmü, işkencesi ve baskısı yansıtılmaya çalışılmıştır. Burada ele alınan diğer bir konu da din adamlarının sömürge güçlerin emelleri karşısındaki siyasi tutumları ve rolüdür. Romanlarda Kürt toplumunda kadının statosü ve rolünden de bahsedilmektedir. Kürt toplumunda kadının konumuna bölgede yaşayan diğer milletlerin bakış açısı irdelenmiştir. Oryantalistlerin bu konudaki notları ve araştırmalarına değinilmiştir. Çalışmanın içerisinde bu sayılanlar ve daha fazlası yer almaktadır. Ez-Zibârî’nin romanları modern çağ sonrası dönemi temsil etmektedir. Zira yazar tarihi ve tarihi olayları modern bir bakış açısıyla, güçlü bir sanatsal örgü ve ifade biçimi ile okumaya çalışmaktadır. Yazar yerşeyi olduğu gibi gösteren bir fotoğraf makinesi gibi olmaktan kurtulmayı başarmıştır. Tam aksine tarihi gerçek olayları güzel tasvirler ve hayal gücüyle yansıtmıştır. Bunu da romanlarının edebi değerini yükselten bazı sanatsal edebi teknikler kullanarak yapmıştır. Bunların başında anlam/anlatım ötesi, hayal gücünü kullanma, metnin sembollerle dizimi, ironi ve retorik imgeler gibi edebi teknikler gelmektedir. This study attempts to stand and display the most significant features of realism in the novels of the Kurdish writer '' Abdul KarimYahyaZebari '', who is one of the Kurdish creative writersin the field ofliterature (Novel), besides, he has several books in criticism and short stories, who won international awards including the Sharjah Prize for Creativity Literary works at its twelfth session.The study displaysthe realistic aspect of his novel"Songs of the Road to Halabja", which reflects an image of life of Kurdish society with othercommunities in the region during a hard transitional period i.e. the beginning of twentieth century. While thenovel “A Disgrace Young Carries Two Guns” examines the sufferings of Kurdish societyunder the governments and tyrannical regimes, during the period of monarchy and republicanism in Iraq, where these stories went to deal with the history of Kurdish people in Iraq so as to reveal the reality in that historical period, in addition to the Kurds' relations with other communities whom lived together in the same region includingTurkmen,Persian, and Arab people. This novel also reveals the tribe’s tyrannical power and suppression to the common people, the role of religious men and their political movements against the ambitions of the colonial powers, moreover, the role of women in Kurdish society along with the people’s viewpoints towardsthem in the region, and the observations of orientalists and their studies on that status.All in all, throughout this study and what is observed from his novels, the study concluded that the novels are postmodern, where he tried to read the history in a post-modernistic viewpointby an artistic technique with high quality of performance, he endeavored to get rid of actual realism, such as the photographic device that depicts everything as it is, however,he combined history to his contemporary reality by his magic imagination and his beauty of photographing. The researchvia artistic literary techniques has examined in its study the "meta-narrative, fantasy, symbolic design, paradox and rhetorical images”.

This paper presents a modified multilevel inverter with a few number of semiconductorswitches and increasing number of output levels. One stage of the proposed inverter leads to getseven levels in the output voltage, while, forty-nine levels can be obtained when using two stages.Only six semiconductor switches are required for each stage. Standard DC sources are used, so, DC-DC converter is not required to get the desired output standard voltage. Total harmonic distortion in the output waveform of the two stage inverter is very low, so, using filter to improve output waveform is unnecessary. This topology is valid for all types of loads. Simulation results are presented for one stage and two stage inverters proposed. Experimental results are included for the one stage inverter to verify the theoretical results.

Effectiveness of CNS-acting drugs depends on the localization, targeting, and capacity to be transported through the blood-brain barrier (BBB) which can be achieved by designing brain-targeting delivery vectors. Hence, the objective of this study was to screen the formulation and process variables affecting the performance of sertraline (Ser-HCl)-loaded pegylated and glycosylated liposomes. The prepared vectors were characterized for Ser-HCl entrapment, size, surface charge, release behavior, and in vitro transport through the BBB. Furthermore, the compatibility among liposomal components was assessed using SEM, FTIR, and DSC analysis. Through a thorough screening study, enhancement of Ser-HCl entrapment, nanosized liposomes with low skewness, maximized stability, and controlled drug leakage were attained. The solid-state characterization revealed remarkable interaction between Ser-HCl and the charging agent to determine drug entrapment and leakage. Moreover, results of liposomal transport through mouse brain endothelialpolyoma cells demonstrated greater capacity of the proposed glycosylated liposomes to target the cerebellar due to its higher density of GLUT1 and higher glucose utilization. This transport capacity was confirmed by the inhibiting action of both cytochalasin B and phenobarbital. Using C6 glioma cells model, flow cytometry, time-lapse live cell imaging, and in vivo NIR fluorescence imaging demonstrated that optimized glycosylated liposomes can be transported through the BBB by classical endocytosis, as well as by specific transcytosis. In conclusion, the current study proposed a thorough screening of important formulation and process variabilities affecting brain-targeting liposomes for further scale-up processes.