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

INDIAN VENTURE CAPITALISTS (VCs) INVESTMENT EVALUATION CRITERIA

The Venture capital (VC) industry in India is of recent origin. However, the average investment value of each deal in India have grown from $3.85 million in 2000 to$7.89 million in 2001.These developments together with the recent steps taken by government to promote venture capitalism in India provide an opportunity for an examination of venture capital industry in India. This paper analyses the validity of venture evaluation model in India by directly comparing the relative importance of evaluation criteria on the funding decision with the relative importance to factors influencing venture's empirical performance. In the light of the differences in investment opportunities around India, and the nature of industrial development in South East Asia in general, the author anticipated that the investment criteria employed by Venture Capital Firms (VCs) in India would differ. A questionnaire was administered to venture capitalists (regular members of Indian Venture Capital Association) to determine the criteria they use to decide on funding new ventures. The response rate was 100%. A list of forty two criteria was developed on previously developed lists. The criteria fell into six groups: the entrepreneur’s personality, the entrepreneur’s experience, characteristics of the product or service, characteristics of the market, financial consideration and characteristics of venture management team. Answers were given on a four point rating scales. The results reveal that criteria adopted by Indian VCs are different from those adopted by VCs in other countries including US. The results also confirm that the entrepreneur’s personality and experience are seen as being primary indicators of the venture’s potential.India, Venture, Capital, Vanture Capital, Criteria, VCs, VCCs, VCFs, Venture Capitalists

Parenting while food insecure: Links between adult food insecurity, parenting aggravation and children’s behaviors

Parents who experience food insecurity face not only uncertainty in obtaining food, but an invisible emotional burden, one that can potentially influence both their parenting behaviors and ultimately, their children. In our study, we investigated adult food insecurity’s link to parents’ aggravation and whether that aggravation influenced their children’s behaviors. Results, based on data from the Early Childhood Longitudinal Survey, Kindergarten Class of 2010-11 using first-difference regression, showed that parents (n=7820) of first graders who became food insecure experienced heightened parenting aggravation (0.525; p < .01). Our mediation analysis on a matched sample of food secure (n=1600) and insecure parents (n=470) revealed that adult food insecurity was not directly associated with children’s behaviors; rather, it was indirectly related to lowered attentional focus (-0.062; p<.05) and inhibitory control (-0.093; p<.001) via parenting aggravation. Our findings underscore the importance of parenting aggravation in transmitting the effects of food insecurity on children’s behaviors

Salient Local 3D Features for 3D Shape Retrieval

In this paper we describe a new formulation for the 3D salient local features based on the voxel grid inspired by the Scale Invariant Feature Transform (SIFT). We use it to identify the salient keypoints (invariant points) on a 3D voxelized model and calculate invariant 3D local feature descriptors at these keypoints. We then use the bag of words approach on the 3D local features to represent the 3D models for shape retrieval. The advantages of the method are that it can be applied to rigid as well as to articulated and deformable 3D models. Finally, this approach is applied for 3D Shape Retrieval on the McGill articulated shape benchmark and then the retrieval results are presented and compared to other methods.Comment: Three-Dimensional Imaging, Interaction, and Measurement. Edited by Beraldin, J. Angelo; Cheok, Geraldine S.; McCarthy, Michael B.; Neuschaefer-Rube, Ulrich; Baskurt, Atilla M.; McDowall, Ian E.; Dolinsky, Margaret. Proceedings of the SPIE, Volume 7864, pp. 78640S-78640S-8 (2011). Conference Location: San Francisco Airport, California, USA ISBN: 9780819484017 Date: 10 March 201