Energy storage systems (ESSs) are the technologies that have driven our society to an extent where the management of the electrical network is easily feasible. The balance in supply-demand, stability, voltage and frequency lag control, and improvement in power quality are the significant attributes that fascinate the world toward the ESS technology. However, being one of the oldest ESS, the flywheel ESS (FESS) has acquired the tendency to raise itself among others being eco-friendly and storing energy up to megajoule (MJ). Along with these, FESS also surpasses the quality of high power density, longer life cycle, higher rate of charge and discharge cycle, and greater efficiency. In this article, an overview of the FESS has been discussed concerning its background theory, structure with its associated components, characteristics, applications, cost model, control approach, stability enhancement, maintenance, and future trends. The FESS structure is described in detail, along with its major components and their different types. Further, its characteristics that help in improving the electrical network are explained. The applications of the FESS have also been illustrated through their economically available prototypes. The economics associated with FESS technology has been projected. A thorough survey of various control strategies of FESS highlighting the merits and demerits of each has been discussed in depth. The stability enhancement and maintenance of the FESS unit have also been enumerated. Further, the article also recommends numerous future work that plays a vital role in the hassle-free operation of FESS for the efficient functioning of the electrical power system.

In recent years, multilevel inverters (MLIs) have emerged to be the most empowered power transformation technology for numerous operations such as renewable energy resources (RERs), flexible AC transmission systems (FACTS), electric motor drives, etc. MLI has gained popularity in medium- to high-power operations because of numerous merits such as minimum harmonic contents, less dissipation of power from power electronic switches, and less electromagnetic interference (EMI) at the receiving end. The MLI possesses many essential advantages in comparison to a conventional two-level inverter, such as voltage profile enhancement, increased efficiency of the overall system, the capability of high-quality output generation with the reduced switching frequency, decreased total harmonic distortions (THD) without reducing the power of the inverter and use of very low ratings of the device. Although classical MLIs find their use in various vital key areas, newer MLI configurations have an expanding concern to the limited count of power electronic devices, gate drivers, and isolated DC sources. In this review article, an attempt has been made to focus on various aspects of MLIs such as different configurations, modulation techniques, the concept of new reduced switch count MLI topologies, applications regarding interface with renewable energy, motor drives, and FACTS controller. Further, deep insights for future prospective towards hassle-free addition of MLI technology towards more enhanced application for various fields of the power system have also been discussed. This article is believed to be extremely helpful for academics, researchers, and industrialists working in the direction of MLI technology.

Recent researches in electrical grids and networks fraternity are directed toward the integration of Microgrid (MG) technologies across the consumer's end. Nowadays, conventional power grid networks are obsolete due to its difficulty of control and protection when many numbers of distributed generations are used. MGs thus acts as a viable solution replacing the conventional grid as it provides integrating platform for Microsources, loads, Electrical Energy Storage Devices and Power Electronic Devices at the demand end within a small locality. MGs are capable of operating either in grid connected or autonomous mode of operation during a faulted situation. However, the system's stability, reliability, and operational control is of extreme concern basically during the islanded mode of operation. Regardless of that, very notable real time implementation and commercial use of MGs are yet to be deployed. This research article brings out a comprehensive review of various challenges and issues related to installation of MG, different controllers for power flow control, idea about the protection system, role of MGs in realizing smart grids (SGs), its major shortcomings, and future prospects.

In recent years, the IoT has emerged as the most promising technology in the key evolution of industry 4.0/industry 5.0, smart home automation (SHA), smart cities, energy savings and many other areas of wireless communication. There is a massively growing number of static and mobile IoT devices with a diversified range of speed and bandwidth, along with a growing demand for high data rates, which makes the network denser and more complicated. In this context, the next-generation communication technology, i.e., sixth generation (6G), is trying to build up the base to meet the imperative need of future network deployment. This article adopts the vision for 6G IoT systems and proposes an IoT-based real-time location monitoring system using Bluetooth Low Energy (BLE) for underground communication applications. An application-based analysis of industrial positioning systems is also presented.

The growing demand for electricity driven by population growth and industrialization is met by integrating hybrid renewable energy sources (HRESs) into the grid. HRES integration improves reliability, reduces losses, and addresses power quality issues for safe and effective microgrid (MG) operation, requiring efficient controllers. In this regard, this article proposes a prairie dog optimization (PDO) algorithm for the photovoltaic (PV)-, fuel cell (FC)-, and battery-based HRESs designed in MATLAB/Simulink architecture. The proposed PDO method optimally tunes the proportional integral (PI) controller gain parameters to achieve effective compensation of load demand and mitigation of PQ problems. The MG system has been applied to various intentional PQ issues such as swell, unbalanced load, oscillatory transient, and notch conditions to study the response of the proposed PDO controller. For evaluating the efficacy of the proposed PDO algorithm, the simulation results obtained are compared with those of earlier popular methodologies utilized in the current literature such as bee colony optimization (BCO), thermal exchange optimization, and PI techniques. A detailed analysis of the results found emphasizes the efficiency, robustness, and potential of the suggested PDO controller in significantly improving the overall system operation by minimizing the THD, improving the control of active and reactive power, enhancing the power factor, lowering the voltage deviation, and keeping the terminal voltage, DC-link voltage, grid voltage, and grid current almost constant in the event of PQ fault occurrence. As a result, the proposed PDO method paves the way for real-time employment in the MG system.