Investigation of FACTS devices to improve power quality in distribution networks

Flexible AC transmission system (FACTS) technologies are power electronic solutions that improve power transmission through enhanced power transfer volume and stability, and resolve quality and reliability issues in distribution networks carrying sensitive equipment and non-linear loads. The use of FACTS in distribution systems is still in its infancy. Voltages and power ratings in distribution networks are at a level where realistic FACTS devices can be deployed. Efficient power converters and therefore loss minimisation are crucial prerequisites for deployment of FACTS devices. This thesis investigates high power semiconductor device losses in detail. Analytical closed form equations are developed for conduction loss in power devices as a function of device ratings and operating conditions. These formulae have been shown to predict losses very accurately, in line with manufacturer data. The developed formulae enable circuit designers to quickly estimate circuit losses and determine the sensitivity of those losses to device voltage and current ratings, and thus select the optimal semiconductor device for a specific application. It is shown that in the case of majority carrier devices (such as power MOSFETs), the conduction power loss (at rated current) increases linearly in relation to the varying rated current (at constant blocking voltage), but is a square root of the variable blocking voltage when rated current is fixed. For minority carrier devices (such as a pin diode or IGBT), a similar relationship is observed for varying current, however where the blocking voltage is altered, power losses are derived as a square root with an offset (from the origin). Finally, this thesis conducts a power loss-oriented evaluation of cascade type multilevel converters suited to reactive power compensation in 11kV and 33kV systems. The cascade cell converter is constructed from a series arrangement of cell modules. Two prospective structures of cascade type converters were compared as a case study: the traditional type which uses equal-sized cells in its chain, and a second with a ternary relationship between its dc-link voltages. Modelling (at 81 and 27 levels) was carried out under steady state conditions, with simplified models based on the switching function and using standard circuit simulators. A detailed survey of non punch through (NPT) and punch through (PT) IGBTs was completed for the purpose of designing the two cascaded converters. Results show that conduction losses are dominant in both types of converters in NPT and PT IGBTs for 11kV and 33kV systems. The equal-sized converter is only likely to be useful in one case (27-levels in the 33kV system). The ternary-sequence converter produces lower losses in all other cases, and this is especially noticeable for the 81-level converter operating in an 11kV network

Moderating effect of social support on personal financial constraints and job stress relationship

The aim of this paper is to examine the moderating effect of social support (which may be supervisory, friends, family and relatives) on the relationship of personal financial constraints and job stress relationship. Sample consists of 294 respondents from randomly selected 28 branches of 22 banks located across all major cities of Pakistan. Moderated regression analysis has been used to test the hypothesized relationships. Personal financial constraints enhance job stress and social support moderates this relationship. Job stress increases when an employee faces financial constraints but decreases in the presence of social support. Practical and theoretical implications are drawn. This research is conducted in banking industry, so its results can’t be generalized to other industries. This paper is the first which examines the impact of a non-work related variable, personal financial constraint on job stress along with buffering role of social support. Its findings have great implications for employers for increasing productivity of employees.Job stress, personal financial constraints, social support, moderating, banking, Pakistan

The Effect of Foreign Remittances on Schooling: Evidence from Pakistan

The underlying study intends to show the impact of foreign remittances on the educational performance of children in the households receiving these remittances. Much of the literature in this area covers the effects of remittances on poverty, consumption, and investment behaviour of the receiving households. The literature on the impact of remittances on educational performance, however, is rare, especially in Pakistan. To investigate the impact of remittances on educational performance, primary data at the household level is collected from four main cities of the Khyber Pakhtunkhwa Province, Pakistan. The OLS results illustrate that, without considering parental education, remittances have significant adverse effects on educational performance. However, the effect becomes insignificant once parental education is included, as a control variable, in the regression. The results also reveal that the low level of parental education, current income, assets, family type, and family size play an important role in the educational performance of children.Remittances , Education, Parental Absence

Factors Affecting job satisfaction of employees in Pakistani banking sector

The job satisfaction has got tremendous attention in organizational research. The focus of this study is to determine the impact of various human resource management practices like job autonomy, team work environment and leadership behavior on job satisfaction. It also investigates the major determinants of job satisfaction in Pakistani banking sector. This study further evaluates the level of difference in job satisfaction among male and female employees. The sample of the study consisted of 450 employees working in different banks of Rawalpindi, Islamabad and Lahore through the questionnaire, of which 295 were returned and processed. SPSS was used to analyze the data, using Independent Sample T Test, Correlation and regression analysis. There is a positive and significant link between job satisfaction and human recourse management practices like team work environment, job autonomy and behavior of leadership. From the findings of the study, it is also inferred that male and female workers have significantly different level of job satisfaction.Human resource management practices, job satisfaction, employees, banking sector