Variable frequency drives (VFDs) are a type of electronic device commonly used to drive motors with a wide range of industrial and practical applications, especially in power systems. VFDs are sensitive to voltage sag, thereby limiting their application. However, the difficulty in determining detailed voltage sag tolerance characteristics of VFDs is due to various influencing factors, and the tolerance curve obtained from test results is updated as mainstream low-voltage VFDs change. This study is the first to perform an in-depth analysis on the influence and operation mechanism of voltage sags on VFDs. Voltage sag types, which is regarded as an important influencing factor, are explored for their different impacts on VFDs from the perspective of energy. Then, eight commonly used low-voltage VFDs with small and medium powers (7.5 and 18.5 kW) are selected as the test objects. The influence of voltage sags on VFDs is tested, and equipment parameters (protection modes and control modes of VFDs, load torque and speed) and voltage sag characteristics factors (sag types, voltage magnitude before voltage sag, and harmonics) are considered. Finally, the general tolerance curves of the low-voltage VFDs under different sag types are extracted via comprehensive analyses and processing of more than 13,000 sets of test data. Based on the test data, this study further explores the influence of voltage sag on the motor by using the permanent magnet synchronous motor (PMSM) as an example, which is used as the load during the tolerance test. Operation performance of PMSM driven by different VFDs is also discussed.

This research article presents a comprehensive investigation into the design, optimization, and performance analysis of a hybrid stand-alone microgrid for an industrial facility in Iraq at coordinates 36.51 and 43.99. The system consists of photovoltaic (PV) modules, inverters, a battery energy storage system (BESS), a generator, and AC loads. Leveraging the capabilities of PVsyst version 7.3.1, HOMER Pro version 3.14.2 and SAM version 2022.11.21 software tools, this study assesses the feasibility and functionality of the hybrid stand-alone microgrid. In this study, PVsyst software is used for detailed designing and analysis of a PV plant, and the PVsyst design file is then used in HOMER Pro software to optimize and design the proposed hybrid stand-alone microgrid, and for detailed performance analysis SAM software is employed. This paper also investigates the impact of ground clearance and ground albedo on the annual generation of bifacial PV modules at various tilt angles. Key findings include a promising normalized production rate of 4.53 kWh/kWp/day with a performance ratio of 0.815 and annual energy production estimates of 84.31 MWh (P50), 79.57 MWh (P90), and 78.24 MWh (P95) for monofacial PV modules, highlighting the system’s potential for renewable energy generation. Notably, this research demonstrates the hybrid stand-alone microgrid’s capacity to significantly reduce CO₂ emissions, saving approximately 1811.6 tons over a 30-year period, thus contributing to sustainability and environmental conservation goals. Additionally, this study reveals operational challenges during the winter months, necessitating generator support to meet load demands. The successful installation and experimental validation of the hybrid stand-alone microgrid underscore its practical viability and its role in advancing clean energy solutions. This research provides valuable insights into hybrid stand-alone microgrid design, emphasizing its importance in ensuring reliable power supply and environmental stewardship.

This research proposes an improved finite control set direct power model predictive control method (FCS-DPMPC) for grid-tie distributed generation (DG). FCS-DPMPC predicts the system outcomes using the system model. During the next sampling time, a voltage vector is defined using the cost function to minimize the power ripple, consequently allowing flexibility for power regulation. Furthermore, the impact of implementing a one-step delay is studied and compensated through a model forecast pattern. In addition, a new two-step horizon technique has been developed to minimize switching frequency and computation burden. Simulation results for single DG and parallel operated DGs in a grid-tie manner confirm the effectiveness of the suggested control strategy, which signifies that this is an appropriate approach for distributed generation in microgrids.

The demand for power demand and nonlinear loads is currently increasing, and thus a compensator that can efficiently afford compensation with growing or reducing load requirement and available transmission network resources are necessary. In this study, we implemented serial FACTS devices, namely, static series synchronous compensator (SSSC) and thyristor-controlled series compensator (TCSC), to increase the power capacity flow in an electric power network. We primarily aim to increase the load capability of the system to maintain system stability after a fault transient. Therefore, we implemented series FACTS devices SSSC and TCSC to maintain stability after a fault transient. Performance result of considered series FACTS controller shows an unstable steady state without a power system stabilizer. This paper presents modeling and simulation of SSSC and TCSC in MATLAB/Simulink to maintain transient stability.

With the rapid development of active distribution networks, the “petal”‐type distribution network has become the mainstream power supply structure. Power control methods for active distribution networks should be further studied to ensure the safe and reliable power supply of a distribution system. An electromagnetic rotary power flow controller (RPFC) is a feasible solution for controlling power in active distribution networks. However, when testing the effectiveness of the PQ decoupled control method for RPFC based on instantaneous reactive power theory, difficulties were encountered with the synchronous control of the rotor position angle of two rotating‐phase transformers, and the accuracy of power control was unsatisfactory. Given this condition, PQ control is improved in three ways. First, the system's periodic oscillation problem is solved via variable speed control. Second, the servo motor‐rotary phase‐shifting transformer synchronous rotation scheme, which reduces power control error and improves stability, is designed. Third, the overshoot phenomenon in power control is improved using the variable‐domain fuzzy proportional‐integral adaptive method. Experimental results show that the proposed advanced control scheme exhibits good dynamic and static performance in power control scenarios and achieves effective improvement in RPFC.

This study aimed to develop a cost-effective, environmentally sustainable, and technologically advanced dielectric fluid by utilizing the beneficial properties of natural ester-based vegetable oils, offering a promising alternative for transformer insulation and cooling applications. The novelty of this research lies in the formulation of a nanofluid that combines three distinct vegetable oils—castor, flaxseed, and blackseed—creating a unique base fluid. SiO₂ nanoparticles were incorporated into the fluid to leverage their multiple advantageous characteristics. Extensive experiments were conducted to evaluate the superior properties of the proposed nanofluid, focusing on key dielectric properties, such as relative permittivity (ε_r) and the dielectric dissipation factor (tan δ). Comparative analyses with conventional mineral oil, which was used as a benchmark, demonstrated the significant advantages of the vegetable oil-based nanofluid. The novel formulation outperformed all other tested samples, highlighting its exceptional performance. Additionally, three preparation methods were examined, with the green synthesis technique producing the nanofluid with better dielectric properties. Through a detailed presentation of empirical data and compelling arguments, this study confirms the potential of natural ester-based vegetable oil nanofluids as a highly promising alternative, driven by their intrinsic properties and the environmentally friendly synthesis method employed.