Agileswari K. Ramasamy

Bio: Agileswari K. Ramasamy is an academic researcher from Universiti Tenaga Nasional. The author has contributed to research in topics: Electric power system & Photovoltaic system. The author has an hindex of 10, co-authored 77 publications receiving 340 citations.

Review on Scheduling, Clustering, and Forecasting Strategies for Controlling Electric Vehicle Charging: Challenges and Recommendations

Abstract: The usage and adoption of electric vehicles (EVs) have increased rapidly in the 21st century due to the shifting of the global energy demand away from fossil fuels. The market penetration of EVs brings new challenges to the usual operations of the power system. Uncontrolled EV charging impacts the local distribution grid in terms of its voltage profile, power loss, grid unbalance, and reduction of transformer life, as well as harmonic distortion. Multiple research studies have addressed these problems by proposing various EV charging control methods. This manuscript comprehensively reviews EV control charging strategies using real-world data. This review classifies the EV control charging strategies into scheduling, clustering, and forecasting strategies. The models of EV control charging strategies are highlighted to compare and evaluate the techniques used in EV charging, enabling the identification of the advantages and disadvantages of the different methods applied. A summary of the methods and techniques for these EV charging strategies is presented based on machine learning and probabilities approaches. This research paper indicates many factors and challenges in the development of EV charging control in next-generation smart grid applications and provides potential recommendations. A report on the guidelines for future studies on this research topic is provided to enhance the comparability of the various results and findings. Accordingly, all the highlighted insights of this paper serve to further the increasing effort towards the development of advanced EV charging methods and demand-side management (DSM) for future smart grid applications.

Dynamic Voltage Restorer For Voltage Sag Compensation

Abstract: The Dynamic Voltage Restorer (DVR) is a power electronic device that is used to inject 3-phase voltage in series and in synchronism with the distribution feeder voltages in order to compensate for voltage sag. In this paper the operation of a DVR is presented. The power circuit of a DVR together with the control techniques used for compensation is explained. The operation of the Software Phase Locked Loop (SPLL) and its stability are analyzed. The DVR control system is described and verified using simulation. The control algorithm implemented using DSP was tested using generated input voltage signals and the results are also presented. The micro-cycle effect of battery current for balanced and unbalanced sag is also investigated.

Design & Development of Compact Uniplanar Semi-Hexagonal ACS Fed Multi-Band Antenna for Portable System Application

Abstract: In the present work, a compact size, dual-band antenna is proposed for WLAN/WiMAX/LTE 2500/DMB applications. The designed antenna is fed by a 50 Ω coplanar line. The radiating component of the composed antenna consists of radiating strips with half hexagonal and vertical rectangular shapes and square-shaped ground plane which are printed on the same layer. The overall size of the antenna substrate is only 10× 24× 1.6 mm3. The simulated and measured results of the proposed antenna show that it operates in the frequency range from 2.5 GHz to 2.75 GHz and 5.0 GHz to 6.7 GHz, respectively.

Grey Wolf Optimizer Based Battery Energy Storage System Sizing for Economic Operation of Microgrid

Abstract: Battery energy storage systems (BESSs) can support microgrid's economic operation. In this paper, the optimal capacity of BESS is determined for economic operation of microgrid. The BESS sizing problem is solved simultaneously with “mix-mode energy management system” (MM-EMS). Here, the MM-EMS is solved using linear programming (LP), and mixed integer linear programming (MILP) optimization techniques. Metaheuristic optimization techniques such as grey wolf optimizer (GWO), particle swarm optimization (PSO), artificial bee colony (ABC), gravitational search algorithm (GSA) and genetic algorithm (GA) are used to solve the BESS sizing problem and a comparison of its performance is also carried out. It was found that GWO produces the most optimal solution than other optimization techniques. With this, the performance of the proposed BESS sizing method is validated with traditional tradeoff method. Moreover, a comparison in microgrid's operating cost with and without BESS is carried out. It was also found that, 70% savings in microgrid's operating cost can be achieved when microgrid is operated with BESS.

Fundamentals of Queueing Theory

Abstract: Praise for the Third Edition: "This is one of the best books available. Its excellent organizational structure allows quick reference to specific models and its clear presentation . . . solidifies the understanding of the concepts being presented."IIE Transactions on Operations EngineeringThoroughly revised and expanded to reflect the latest developments in the field, Fundamentals of Queueing Theory, Fourth Edition continues to present the basic statistical principles that are necessary to analyze the probabilistic nature of queues. Rather than presenting a narrow focus on the subject, this update illustrates the wide-reaching, fundamental concepts in queueing theory and its applications to diverse areas such as computer science, engineering, business, and operations research.This update takes a numerical approach to understanding and making probable estimations relating to queues, with a comprehensive outline of simple and more advanced queueing models. Newly featured topics of the Fourth Edition include:Retrial queuesApproximations for queueing networksNumerical inversion of transformsDetermining the appropriate number of servers to balance quality and cost of serviceEach chapter provides a self-contained presentation of key concepts and formulae, allowing readers to work with each section independently, while a summary table at the end of the book outlines the types of queues that have been discussed and their results. In addition, two new appendices have been added, discussing transforms and generating functions as well as the fundamentals of differential and difference equations. New examples are now included along with problems that incorporate QtsPlus software, which is freely available via the book's related Web site.With its accessible style and wealth of real-world examples, Fundamentals of Queueing Theory, Fourth Edition is an ideal book for courses on queueing theory at the upper-undergraduate and graduate levels. It is also a valuable resource for researchers and practitioners who analyze congestion in the fields of telecommunications, transportation, aviation, and management science.

Wide Band Gap Chalcogenide Semiconductors.

Abstract: Wide band gap semiconductors are essential for today's electronic devices and energy applications because of their high optical transparency, controllable carrier concentration, and tunable electrical conductivity. The most intensively investigated wide band gap semiconductors are transparent conductive oxides (TCOs), such as tin-doped indium oxide (ITO) and amorphous In-Ga-Zn-O (IGZO), used in displays and solar cells, carbides (e.g., SiC) and nitrides (e.g., GaN) used in power electronics, and emerging halides (e.g., γ-CuI) and 2D electronic materials (e.g., graphene) used in various optoelectronic devices. Compared to these prominent materials families, chalcogen-based (Ch = S, Se, Te) wide band gap semiconductors are less heavily investigated but stand out because of their propensity for p-type doping, high mobilities, high valence band positions (i.e., low ionization potentials), and broad applications in electronic devices such as CdTe solar cells. This manuscript provides a review of wide band gap chalcogenide semiconductors. First, we outline general materials design parameters of high performing transparent semiconductors, as well as the theoretical and experimental underpinnings of the corresponding research methods. We proceed to summarize progress in wide band gap (EG > 2 eV) chalcogenide materials-namely, II-VI MCh binaries, CuMCh2 chalcopyrites, Cu3MCh4 sulvanites, mixed-anion layered CuMCh(O,F), and 2D materials-and discuss computational predictions of potential new candidates in this family, highlighting their optical and electrical properties. We finally review applications-for example, photovoltaic and photoelectrochemical solar cells, transistors, and light emitting diodes-that employ wide band gap chalcogenides as either an active or passive layer. By examining, categorizing, and discussing prospective directions in wide band gap chalcogenides, this Review aims to inspire continued research on this emerging class of transparent semiconductors and thereby enable future innovations for optoelectronic devices.

Battery energy-storage system: A review of technologies, optimization objectives, constraints, approaches, and outstanding issues

Abstract: Due to urbanization and the rapid growth of population, carbon emission is increasing, which leads to climate change and global warming. With an increased level of fossil fuel burning and scarcity of fossil fuel, the power industry is moving to alternative energy resources such as photovoltaic power (PV), wind power (WP), and battery energy-storage systems (BESS), among others. BESS has some advantages over conventional energy sources, which include fast and steady response, adaptability, controllability, environmental friendliness, and geographical independence, and it is considered as a potential solution to the global warming problem. This paper provides a comprehensive review of the battery energy-storage system concerning optimal sizing objectives, the system constraint, various optimization models, and approaches along with their advantages and weakness. Furthermore, for better understanding, the optimization objectives and methods have been classified into different categories. This paper also provides a detailed discussion on the BESS applications and explores the shortages of existing optimal BESS sizing algorithms to identify the gaps for future research. The issues and challenges are also highlighted to provide a clear idea to the researchers in the field of BESS. Overall, this paper conveys some significant recommendations that would be useful to the researchers and policymakers to structure a productive, powerful, efficient, and robust battery energy-storage system toward a future with a sustainable environment.

DC Microgrid Planning, Operation, and Control: A Comprehensive Review

Abstract: In recent years, due to the wide utilization of direct current (DC) power sources, such as solar photovoltaic (PV), fuel cells, different DC loads, high-level integration of different energy storage systems such as batteries, supercapacitors, DC microgrids have been gaining more importance. Furthermore, unlike conventional AC systems, DC microgrids do not have issues such as synchronization, harmonics, reactive power control, and frequency control. However, the incorporation of different distributed generators, such as PV, wind, fuel cell, loads, and energy storage devices in the common DC bus complicates the control of DC bus voltage as well as the power-sharing. In order to ensure the secure and safe operation of DC microgrids, different control techniques, such as centralized, decentralized, distributed, multilevel, and hierarchical control, are presented. The optimal planning of DC microgrids has an impact on operation and control algorithms; thus, coordination among them is required. A detailed review of the planning, operation, and control of DC microgrids is missing in the existing literature. Thus, this article documents developments in the planning, operation, and control of DC microgrids covered in research in the past 15 years. DC microgrid planning, operation, and control challenges and opportunities are discussed. Different planning, control, and operation methods are well documented with their advantages and disadvantages to provide an excellent foundation for industry personnel and researchers. Power-sharing and energy management operation, control, and planning issues are summarized for both grid-connected and islanded DC microgrids. Also, key research areas in DC microgrid planning, operation, and control are identified to adopt cutting-edge technologies. This review explicitly helps readers understand existing developments on DC microgrid planning, operation, and control as well as identify the need for additional research in order to further contribute to the topic.