The investigation focused on chalcogenide perovskite compounds, specifically CaZrTe₃ and CaHfTe₃. We analyzed their structural, electronic, and optical properties using first-principles calculations with the CASTEP code, employing gradient generalized approximations of Wu and Cohen (GGA-WC) and Perdew et al. (GGA-PBE) from density functional theory (DFT). Our findings revealed that CaZrTe₃ and CaHfTe₃ compounds have orthorhombic crystalline structures, with primitive cell volumes measuring 661.30 and 665.04 ų, respectively, using the PBE method. Our analysis of the electronic characteristics suggests the potential for customizing bandgap and semiconductor behavior, which could improve the efficiency of electronic semiconductor devices and photovoltaic cells. Additionally, the optical properties of CaZrTe₃ and CaHfTe₃ perovskites, including high absorption coefficients and distinct reflectivity characteristics, indicate the potential for improved solar energy conversion efficiencies and advanced optoelectronic device performance. However, the study also highlights challenges in the commercial deployment of chalcogenide perovskite materials, such as scalable synthesis methods and integration into existing device architectures. We propose future research directions focusing on developing and exploring material interfaces within device configurations. This research contributes to our understanding of CaZrTe₃ and CaHfTe₃ chalcogenide perovskites and underscores their potential to significantly influence the development of photovoltaic and optoelectronic technologies and their environmental compatibility.

Reactive and harmonic currents that are being injected into the power supply by nonlinear loads, cause an increasing deterioration of the power system voltages and currents, whereas active power filter (APF) has been widely used to overcome this problem and to improve the power quality delivered by the power supply. In this paper, a three-level four-legged active power filter based on a neutral-point-clamped (NPC) inverter is presented. To fulfil the requirement of the active power filtering function under balanced, unbalanced, and distorted (including 3rd and 5th harmonics) power supply voltages, a control method based on the instantaneous power theory has been used and discussed. On the other side, the inverter switching state control has been achieved based on PWM current controller. The performance of the proposed topology under the control approach has been finally discussed through the obtained simulation results.

Voltage sags, as defined by the IEEE Standard, refer to sudden drops in voltage magnitude that last for a duration greater than 0.5 cycles of the power frequency but less than or equal to 1 minute. These events are considered significant in power quality issues. The change rate of voltage during a voltage sag can range from 0.1 to 0.9 per unit (p.u.) of nominal voltage, where 1 p.u. represents the nominal voltage level. Addressing the power quality (PQ) challenge is a critical component of ensuring the reliable and efficient operation of modern power systems. Advances in PQ monitoring and control technologies, power electronic devices, smart grid technologies, and PQ standards have all contributed significantly to improving PQ and enhancing the resilience and responsiveness of power systems. However, voltage sags are particularly challenging to resolve and may require a range of solutions. Voltage sags are a critical factor in PQ and can cause significant disruptions in the power system. As a result, mitigating voltage sags is a key area of focus in PQ improvement efforts. This paper presents an in-depth analysis of voltage sags in power grid, including their causes, characteristics, and harmful effects on electrical equipment and industrial processes. The authors highlight the significance of voltage sag mitigation techniques to reduce the economic losses and damage caused by these PQ issues. The paper provides an overview of existing mitigation techniques, including dynamic voltage restorer (DVR), distribution static synchronous compensator (D-STATCOM), and other custom solutions. Additionally, the paper discusses the economic impact of voltage sag on various industrial sectors, including the semiconductor and information industries. The authors emphasize the need for continued research and development of effective voltage sag mitigation techniques to enhance the stability and reliability of power grid and electrical systems. This paper is a valuable resource for researchers, engineers, and professionals in the field of power systems, providing insights into the causes and mitigation of voltage sags in the power grid.

The Doubly-Fed Induction Generator (DFIG) technology's capacity to adjust the rotor frequency depending on wind conditions greatly enhanced the wind farm's total energy collection. Adaptability is crucial for maximizing the efficiency of power generation, especially in regions with variable wind patterns. This article does a comprehensive examination of a 9 MW wind farm of six 1.5 MW wind turbines. The turbines are designed to optimize power generation and reduce mechanical strain. The wind farm is linked to a 25 kV distribution system, which transmits power to a 120 kV grid by a 30 km, 25 kV feeder. The primary advancement is in the use ofDFIG technology in every turbine. This method utilizes a wound rotor induction generator in conjunction with an AC/DC/AC IGBT-based PWM converter. The stator winding is directly linked to the 60 Hz Microgrid, whilst the rotor is supplied with electricity of varying frequency via the converter. DFIG technology optimizes the energy extraction from low wind speeds by dynamically regulating the turbine's rotational speed, resulting in optimal use of wind power. The capacity to adjust is essential for keeping a constant power production under different wind conditions. Furthermore, the technique significantly contributes to the reduction of mechanical strains on the turbines when exposed to strong gusts of wind, hence improving their durability and decreasing the expenses associated with maintenance. The article assesses the whole performance of the wind farm, analyzing power generation, effectiveness, connection to the Microgrid, and the influence of DFIG technology on energy extraction and reduction of mechanical stress. The results highlight the efficacy of the suggested approach in attaining substantial energy production and maintaining consistent performance.