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

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

Application of Multiple Criteria Decision Models for Oilseed Crops in Pakistan’s Punjab

Pakistan is deficient in major food products. Self-sufficiency in food has virtually always been a major priority, because imports of wheat, edible oil, sugar, pulses and milk products put a massive burden on the balance of payments for the country. The increase in the production of oilseed has been a priority goal of the agricultural development policy in Pakistan. The oilseed crops have been validated as alternative crops on several target locations of different agro-ecological zones [PARC (1990)]; but the success of this validation work in terms of their dissemination is very limited. The possibility of including these crops in well established systems needed to be well conceived. The selection of farming systems, which have the potential to adopt such crops, is a prerequisite to investigate the problems and prospects of oilseed crops. The emphasis of the study is, therefore, on the identification of typical farm situations where the oilseed crops can be evaluated for their potential inclusion in the cropping plans. A real decision-making environment in agriculture involves several objectives along with their explicit targets.

XBioSiP: A Methodology for Approximate Bio-Signal Processing at the Edge

Bio-signals exhibit high redundancy, and the algorithms for their processing are inherently error resilient. This property can be leveraged to improve the energy-efficiency of IoT-Edge (wearables) through the emerging trend of approximate computing. This paper presents XBioSiP, a novel methodology for approximate bio-signal processing that employs two quality evaluation stages, during the pre-processing and bio-signal processing stages, to determine the approximation parameters. It thereby achieves high energy savings while satisfying the user-determined quality constraint. Our methodology achieves, up to 19x and 22x reduction in the energy consumption of a QRS peak detection algorithm for 0% and <1% loss in peak detection accuracy, respectively.Comment: Accepted for publication at the Design Automation Conference 2019 (DAC'19), Las Vegas, Nevada, US

The commercialisation of BDS through an NGO: case study of AKRSP-Pakistan

Book ChapterBased on the theme of how donors can play a more effective role to stimulate effective and sustainable provision of BDS by or through private sector intermediaries, this case study looks at how the Aga Khan Rural Support Programme (AKRSP) has sought to encourage the development of markets for Business Development Services (BDS) in the remote areas of northern Pakistan. This paper explores that the isolation of the region, poor infrastructure, small scale of landholdings, and lack of economic development leads to problems when attempting to promote markets for business development services. In the short term, the priority is the development of more basic markets, rather than markets for business development services. Without active markets there are a few opportunities for BDS provision let alone the development of vibrant private sector markets for BDS. It specifies the geographic, economic, political, and institutional context in which the AKRSP’s interventions have been implemented. Grassroots village based initiatives have been discussed, where groups of farmers are facilitated by AKRSP to provide BDS to neighboring farmers (farmers interest groups in Chitral), along with more structured formal approaches such as the more direct provision of BDS through commercial entity associated with AKRSP (North South Seeds). It is argued that both models have a positive impact on MSME performance and lead to market development in the long run. Both are methods through which donors can promote BDS markets but which model is most appropriate depends on the market being served. Where the service offered is relatively simple and the business of the BDS provider is relatively straight-forward, facilitating private sector intermediaries may be the most effective way of creating markets for BDS. However, where the service is complex and there is a need to establish a sophisticated organisation to provide the service, it may be necessary to set up an organisation within the NGO, on commercially sustainable basis if possible, with a view to fully commercialising and ideally privatising the organisation over time