Journal of King Saud University, Engineering Sciences最新文献

With the objective of discovering the vital line in an electrical power grid (EPG) where the unified power flow controller (UPFC) could be inserted to minimize the severity of overloading (SOL) during contingencies, an investigation into the stiffness of single line contingencies (SLC) on the EPG is presented in this study. An overloading index (OVI) is developed and used in this contribution to arrange the transmission branches of the EPG based on their cruciality and criticality throughout SLC. A harmony search algorithm (HSA), an optimization method, has been adopted to optimally set the parameters of the UPFC to achieve the best minimum SOL of the system at the optimal location. The IEEE 30-bus network was used as the test bed. Results based on the test bed show that placing a UPFC based on the ranking of a well-known contingency severity index (CSI) minimized the SOL to $2.40\times {10}^{10}$ as against the $8.05\times {10}^5$ obtained when the placement is done on the ranking based on the proposed OVI. The minimization of SOL is achieved with a reactance and reactive power of $0.036pu$ and $0.096pu,$ respectively, of the UPFC. The result also reveals that the proposed OVI identifies with a higher level of precision the vital line in the test bed for placing the UPFC for the purpose of minimizing the SOL during contingencies.

This work used a unified dynamic model of microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) that were combined to create MFC-powered MECs. This allowed for a completely sustainable and green system of hydrogen production and wastewater treatment. The main advantage that was envisioned for this coupled system was the elimination of the need for an external power source; the only feed to the system was the wastewater itself. We present the results of parameter estimation and model validation. The results showed the importance of minimizing internal resistance to increase hydrogen production. Better powering of MECs was achieved by setting MFCs in series rather than in parallel.

This study focuses on assessing the resilient characteristics of a clayey soil modified with a fly ash (FA)-based geopolymer and reclaimed asphalt pavement (RAP) as an unpaved road material. RAP-geopolymer-soil mixtures were designed using the response surface methodology-central composite design with 0–40% RAP and 0–25% FA. The repeated-load California bearing ratio (CBR) testing method was used to determine the recoverable and permanent deformations and then obtain the equivalent (resilient) modulus (M_equ). The M_equ values were used to develop predictive models and determine the optimum soil–RAP–geopolymer mixture. The effects of the load level and soaking period on the stiffness of the optimum mixture were also investigated. The results revealed that the geopolymer binder played a significant role in enhancing the stiffness of the mixtures, with the maximum M_equ obtained at 25% FA and 0% RAP. However, it was determined that RAP has an adverse effect on the stiffness for almost all the studied cases and more significantly for the 40% RAP and 0% FA mixture. The optimal mixture was found to be 25% FA and 30% RAP. The developed model exhibited excellent predictive capability based on ANOVA results. The optimum mixture exhibited stress-softening behavior at an increased load level. No clear trend was observed in the effect of the soaking period on the resilient modulus within the examined soaking period range. Overall, this study agrees with several pavement design guidelines to limit the RAP content used in road applications owing to uncertain adequacy. Additionally, it suggests that the geopolymer binder is an effective stabilizer with excellent environmental and economic potential.

Microgrids (MGs) comprising of distributed generation units (DGs) are subjected to plug-and-play operation (PnP), lines (connecting the DGs) parameters uncertainty, and load changes. Robust stability and an authentic operation for islanded microgrids can be guaranteed through a robust decentralized voltage tracker developed in this paper. The proposed controller design has the following merits: 1) fully decentralized, 2) scalable, and 3) maintains robust stability against PnP of DGs, load changes, and lines parameters’ uncertainties. A sufficient condition is developed by linear matrix inequality convex optimization is exploited to solve the problem. The MGs’ changes in load and the line's parameters are modelled as norm-bounded uncertainties. The suggested controller uses local measurements from DGs, i.e., decentralized by the decomposition of the global system into subsystems. For each subsystem, the rest of the system's impact is considered disturbances, whose influence must be minimized. The proposed disturbance rejection control algorithm is based on the method of invariant-ellipsoids. Several time-domain scenarios such as connecting and disconnecting a number of DGs, local load changes, and variation of transmission line parameters are executed to assess the suggested controller's effectiveness, using MATLAB /Sim PowerSystems Toolbox.

This paper proposes a field-oriented control (FOC) of a rotor-tied DFIG (RT-DFIG) using a high gain observer (HGO). For speed/DC-voltage and current regulation, the FOC employs a Proportional-Integral (PI) controller in both outer and inner loops. The goal is to maximize wind power mining by allowing wind turbines to operate at variable speeds. In addition, by utilizing current/voltage measurements, HGO estimates the mechanical speed of the rotor for FOC deployment. Finally, the simulation results of the suggested method for the 7.5 kW RT-DFIG are provided. The HGO was tested in both static and dynamic wind settings and with parameter modifications. Furthermore, various existing observer-based control methods were compared, which verified the proposed method’s superiority.

In addition to global warming and population growth, the Turkish and Iranian water projects have negatively affected the water resources in Iraq. Recently, Iran has implemented its largest water project (The Tropical Water Project – TWP). This project aims to store the flowing water in the Sirwan and Zmkan rivers (i.e., tributaries of the Diyala River) to provide irrigation, domestic, and industrial water for areas inside and outside the Diyala River Basin. The Darbandikhan dam and Halabja water supply project are located on the Diyala River. In this study, the impact of the TWP on the operation of the Darbandikhan dam and Halabja water supply project was investigated. The monthly inflow data of the Darbandikhan dam from September 1991 to December 2017 were used to simulate the operation of the dam using the HEC-ResSim 3.1 package. Two scenarios were adopted for the operation of the Darbandikhan dam. In the first scenario, the Darbandikhan dam operation was simulated without considering the effects of the TWP project.

In contrast, in the second scenario, the full operation of the TWP project was considered. The results revealed that about 48.4% of the power generation capacity would be lost, and the water surface elevation in the reservoir would be affected significantly due to the TWP project. The water surface elevation would be at or below 443 m for long periods, which will affect the operation of the Halabja water supply project.

For optimal equipment procurement in Taiwan, first, the specifications and prices of a product are evaluated. Based on these evaluations, procurement decisions are made. Ensuring accurate evaluation criteria for procurement is a multicriteria decision making (MCDM) problem. Printed circuit board (PCB) manufacturers have not grasped the decision-making factors of the new equipment specification, and they continue to use the previous generation specifications as the decision-making criteria for new equipment; this results in inappropriate evaluation criteria. When new equipment with different specifications is launched, purchasers may still use the specifications of older equipment as a basis for their purchase decisions. For example, thermal power generation specifications are often used to evaluate equipment for nuclear power generation. The difference in criteria renders it difficult to make decisions for new equipment. We proposed the use of a scientific method to establish a set of criteria decision-making models for equipment procurement to help PCB factories accurately evaluate contemporary specifications. This research established criteria for new technologies to help decision makers select the most appropriate method. We used the Delphi method and the analytic hierarchy process (AHP) to provide insights into technological and commercial requirements, and a model was further developed for optimal equipment procurement.

City traffic conditions contain frequent starts and stops. Thus, Single-Stage Continuously Variable Transmissions are subject to high loads when operating at high gear ratios, leading to excessive friction that cause slipping and heating of friction elements. This study proposes a microprofile with undulation on the surface of the pulley. A mathematical dependence on the technological quality assurance of the surface layer of the V-belt transmission parts formed during turning is proposed, enabling the prediction of height parameters of undulation depending on the change in the spindle speed, feed, and cutting speed. Estimating the error in the field experiment data and calculating values of the proposed methodology showed that the height parameters of the undulation of pulleys have a relative error of 6.3%.