Intelligent STATCOM Voltage Regulation using Fuzzy Logic Control

Reactive power compensation is a very important and challenging task in electrical power systems today. Future trends foreseen in power systems such as high interconnectivity and the integration of renewable energy resources produce even more issues related to power system control and stability. Flexible AC transmission systems are vastly used in power systems in order to mitigate several performance aspects found in typical power systems. One shunt connected device in particular, STATCOM, is very powerful and commonly used in voltage regulation at the power transmission level. STATCOM uses voltage sourced converters to inject or absorb reactive power from the power grid as commanded to stabilize the transmission line voltage at the point of connection. The control of STATCOM has relied historically on using traditional PI controllers, however, since the dynamic response of STATCOM highly affects its ability to perform its task, improving the capabilities of STATCOM using more advanced control approaches has become vital for both manufacturers and power systems operators. Fuzzy logic control, as one area of artificial intelligence techniques, has been emerging in recent years as a complement to the conventional methods in various areas of power systems control. The most significant advantage of fuzzy controller as an intelligent controller is that it doesn’t require mathematical modelling. It is robust and nonlinear in its nature, and expert’s knowledge can be utilized in generating control rules. The main contribution is to use fuzzy logic control theory to design a pure fuzzy logic control and another fuzzy adaptive PI control strategies for STATCOM that are superior in performance to traditional PI control approach. This will increase STATCOM’s ability to seamlessly perform their task in voltage regulation. This work investigates the performance of classical PI controlled STATCOM then compares it with fuzzy logic based STATCOM and fuzzy adaptive PI controlled STATCOM. Simulations done using MATLAB on a three generator test system show that adaptive fuzzy PI control technique is faster in responding to voltage variations and better in tracking the reactive current reference. Results also show that a direct control using fuzzy logic provides even faster voltage regulation and acts almost as a perfect tracker for reference reactive current

The influence of audit committee characteristics on firm performance : evidence in Oman

The role of an audit committee (AC) is very significant to stakeholders in influencing the quality of disclosure of financial reporting and in improving market performance. This study examines the influence of audit committee characteristics (AC multiple directorship, AC size, AC independence, AC meeting, AC chairman independence, AC diligence) and firm performance (ROA and Tobin’s Q). The population of the study is 82 firms based on the Muscat Stock Market (MSM) listed companies as at 2014 to 2015, excluding the financial and banking sectors. The method of data collection was secondary data, using annual financial reports of firms gathered from Data Stream. The data was analyzed using Stata. The major findings of the study show that audit committee characteristics do not influence firm performance as measured by ROA. However, the study found that AC multiple directorships and AC diligence influence the firm performance as measured by Tobin’s Q. The result also showed that the control variables; (firm size and leverage) are significant in influencing firm performance (ROA and Tobin’s Q). Therefore, the study recommends future studies to consider taking into account some other variables such as foreign audit committee members, and other variables that may have a significant role in improving firm performance

Investigation and comparison of solution methods of the unit commitment problem for thermal units

This thesis deals with a general investigation and comparison of methods of solution of the unit commitment problem for thermal generating units. An intensive mathematical model for this problem has been developed and presented. The most commonly implemented methods for solving the problem of unit commitment were reviewed and discussed. Every reviewed method had been coded in FORTRAN 77 on a VAX11/785 machine. On the basis of the results obtained, a comprehensive comparison of the different methods ha; been carried out. For the comparison to be realistic and practical, each method was tested on three power systems of different sizes. As a result of the comparison, the unit commitment problem for a case study system has been solved by using the most appropriate method(s) from those discussed in the thesis. A new approach for solving the problem has also been proposed and tested.This thesis deals with a general investigation and comparison of methods of solution of the unit commitment problem for thermal generating units. An intensive mathematical model for this problem has been developed and presented. The most commonly implemented methods for solving the problem of unit commitment were reviewed and discussed. Every reviewed method had been coded in FORTRAN 77 on a VAX11/785 machine. On the basis of the results obtained, a comprehensive comparison of the different methods ha; been carried out. For the comparison to be realistic and practical, each method was tested on three power systems of different sizes. As a result of the comparison, the unit commitment problem for a case study system has been solved by using the most appropriate method(s) from those discussed in the thesis. A new approach for solving the problem has also been proposed and tested

Regionally Distributed Architecture for Dynamic e-Learning Environment (RDADeLE)

Non

Real-time monitoring of the prototype design of electric system by the ubidots platform

In this paper, a prototype DC electric system was practically designed. The idea of the proposed system was derived from the microgrid concept. The system contained two houses each have a DC generator and load that consists of four 12 V DC lamps. Each house is controlled fully by Arduino UNO microcontroller to work in Island mode or connected it with the second house or main electric network. House operating mode depends on the power generated by its source and the availability of the main network. Under all operating cases, the minimum price of electricity consumption should satisfy as possible. Information between the houses about the operating mode and the main network state was exchanging wirelessly with the help of the RF-HC12. This information uploaded to the Ubidots platform by the Wi-Fi-ESP8266 included in the node MCU microcontroller. This platform has several advantages such as capture, visualization, analysis, and management of data. The system was examined for different cases to verify its working by varying the load in each building. All tested states showed that the houses transfer from one mode to another automatically with high reliability and minimum energy cost. The information about the main grid states and the sources of the houses were monitored and stored at the Ubidots platform

DOES PHILLIPS CURVE REALLY EXIST? AN EMPIRICAL EVIDENCE FROM JORDAN

This study empirically examined the relationship between inflation rate and unemployment rate in order to predict and estimate the existence of Philips curve trade-off relationship within Jordanian economy over the period of 1976 to 2013. It employs multiple descriptive and econometrics approaches using unit root tests, co-integration tests, VECM, and linear and non-linear ordinary least square regression tests. In the findings of this study, there was a negative and non-linear relationship between unemployment and inflation. The lowest limits of inflation and unemployment were estimated to be 3.779% and 11.077% respectively. The elasticity of inflation with respect to unemployment, and the elasticity of unemployment with respect to inflation were estimated to be -0.23% and- 0.02% respectively. Therefore, this study provides a strong empirical existence of Phillips Curve on Jordanian economy over the period of 1976- 2013. However, this trade-off implies that policymakers can target low unemployment or low inflation, but not both. As a result, policy makers should pay attention to this kind of relationship between these two important economic variables in applying fiscal and monetary policies in reducing any of these two variables

Prevalence of Impacted and Transmigrated Canine among Palestinian People -Jenin District.

The purpose of this study was to investigate the incidence of impacted maxillary canines in a Palestinian population. The study consisted of a retrospective analysis of the panoramic records of 1683 patients. Statistical analysis was used to examine potential differences in the distribution of impacted maxillary and mandibular canines stratified by gender, location (left or right), unilateral and bilateral position, and presence of transmigration. It was found that the incidence of impacted canines was (2.9%). Of the 54 impacted canines, 30 were in females and 24 were in male patients. Ages were in the range of 16-47. Of these subjects, 38 (84.44%) had unilaterally impacted maxillary canines, while 7 (15.55%) had bilateral impactions. One case of transmigrated canine was recorded among the whole sample. As has been noted the incidence of impacted canines in the sample Palestinian population was (2.9%) which is comparable to the findings from previous studies

Estimation of female radiation doses and breast cancer risk from chest CT examinations

Breast organ doses, effective doses and lifetime attributable risk (LAR) of breast cancer from chest CT scans are presented for 200 female patients surveyed from 10 hospitals in the West Bank and Gaza Strip, Palestine. Patient data were collected and organized in a database from May to November 2016. Data include age (15–80 years), weight, height, and calculated body mass index. Exposure data were also recorded for every examination. Exposure data includes milliampere-second (mAs), X-ray tube kilovoltage (kVp), computed tomography dose index, dose length product, manufacturer, name and type of operated CT scanner. Organ and effective doses were evaluated using a web-based commercially available Monte Carlo software: VirtualDose™CT, a product of Virtual Phantoms, Inc. The software utilizes male and female tissue equivalent phantoms of all ages and sizes including pregnant patients. The corresponding phantom was selected for every patient according to patient’s tomographic parameters. Calculated organ doses were used to estimate the LAR of breast cancer according to BEIR VII Phase 2 report. It was found that radiation doses resulting from the same exam vary widely between different hospitals, depending on the parameters used and the type of scanner. For all patients, the breast organ dose ranged from 6.5 to 28 mGy per examination, with an average breast organ dose of 15mGy. The effective dose from chest CT scan per examination ranged from 3 to 14.7 mSv with an average of 7mSv. For younger females (15–29 years), the LAR of breast cancer risk was estimated to be around 0.05%. For older female patients (60–79 years), the risk was ~0.001%. It was found that LAR decreases remarkably with patient’s age. Values obtained in this study vary between hospitals, they are generally low and consistent with other studies reported worldwide