A Local Control Approach to Voltage Regulation in Distribution Networks

This paper address the problem of voltage regulation in power distribution networks with deep penetration of distributed energy resources (DERs) without any explicit communication between the buses in the network. We cast the problem as an optimization problem with the objective of minimizing the distance between the bus voltage magnitudes and some reference voltage profile. We present an iterative algorithm where each bus updates the reactive power injection provided by their DER. The update at a bus only depends on the voltage magnitude at that bus, and for this reason, we call the algorithm a local control algorithm. We provide sufficient conditions that guarantee the convergence of the algorithm and these conditions can be checked a priori for a set of feasible power injections. We also provide necessary conditions establishing that longer and more heavily loaded networks are inherently more difficult to control. We illustrate the operation of the algorithm through case studies involving 8-,34- and 123-bus test distribution systems.Comment: shorter version submitted to NAPS 201

Symbolic analysis of switching systems : application to bifurcation analysis of DC/DC switching converters

Author name used in this publication: Chi K. Tse2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

One read per cell per gene is optimal for single-cell RNA-Seq

An underlying question for virtually all single-cell RNA sequencing experiments is how to allocate the limited sequencing budget: deep sequencing of a few cells or shallow sequencing of many cells? A mathematical framework reveals that, for estimating many important gene properties, the optimal allocation is to sequence at the depth of one read per cell per gene. Interestingly, the corresponding optimal estimator is not the widely-used plug-in estimator but one developed via empirical Bayes

Perception of healthy and unhealthy food among Chinese adolescents

Purpose The purpose of this paper is to explore snacking behavior and perspectives on healthy and unhealthy food choices among adolescents in Mainland China. Design/methodology/approach Four focus-group interviews were conducted. Altogether 24 participants were recruited in Changsha, a second-tier city in China, through a convenience sampling process. They were asked to report their snacking behaviors, identify whether certain snacks are healthy or unhealthy and elaborate on factors affecting food choices. Findings Snacking was prevalent among the participants. The most frequently consumed snacks included fruit, milk and instant noodles. Participants’ evaluations for the healthiness of foods were based on the actual nutritional values of those foods, the effects on growth and body weight and word-of-mouth. Choice of snack was driven mainly by taste, image, convenience and health consciousness. Research limitations/implications The finding was based on a non-probability sample. The paper also did not explore the contexts where snacks were consumed. Practical implications Parents can make healthy snacks more accessible at home and at schools. Educators can teach adolescents how to read food labels. Schools can increase the availability of healthy snacks on campus. Social marketers can promote healthy snacks by associating them with fun and high taste. Originality/value This is the first paper on snacking behaviors among adolescents conducted in a second-tier city in China using focus-group methodology. Keywords: Qualitative methods, Adolescence, Obesity, Consumer socialization, Children and foodpostprin

Slow-scale instability of single-stage power-factor-correction power supplies

Author name used in this publication: Chi K. Tse2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Hopf-type intermediate-scale bifurcation in single-stage power-factor-correction power supplies

Author name used in this publication: Chi K. TseRefereed conference paper2006-2007 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe