Social and Behavioral Sciences Commons^™

Comparative Analysis Of Dynamic Line Rating Models And Feasibility To Minimise Energy Losses In Wind Rich Power Networks, Mathew Simms, Lasantha Meegahapola

Dr Lasantha G Meegahapola

Wind power generation has indicated an exponential increase during last two decades and existing transmission network infrastructure is increasingly becoming inadequate to transmit remotely generated wind power to load centres in the network. The dynamic line rating (DLR) is one of the viable solutions to improve the transmission line ampacity during high wind penetration without investing on an additional transmission network. The main objective of this study is to identify the basic differences between two main line rating standards, since transmission network service providers (TNSPs) heavily depend on these two standards when developing their line rating models. Therefore, a parameter …

Flicker Mitigation Strategy For Dfigs During Variable Wind Conditions, Lasantha Meegahapola, Brendan Fox, Damian Flynn

Dr Lasantha G Meegahapola

This paper presents a flicker mitigation scheme for the doubly-fed induction generator (DFIG) during variable wind conditions. The flicker mitigation strategy was developed based on the distribution line X/R ratio and the active power deviation from the average active power during variable wind conditions. Flicker emission was analyzed using a flicker meter based on the IEC standards. Both short-term and long-term flicker severities were analyzed during the time period of study. The flicker mitigation strategy was evaluated under different system conditions such as X/R ratio, distribution line length, shortcircuit capacity (SCC), and wind variability. It is shown that the proposed …

Optimal Power Flow With Variable Wind Conditions, S Durairaj, L Meegahapola, D Flynn, B Fox

Dr Lasantha G Meegahapola

This paper presents simulation studies of an electric arc furnace (EAF) model in the MATLAB/SIMULINK environment. EAF was modeled as a current source controlled by a non-linear resistance. Voltage flicker, a phenomenon of annoying light intensity fluctuation, caused by EAF, has been a major power quality concern for both power companies and customers. A model was developed for the electric arc furnace and it was applied in the simulation studies of distribution static synchronous compensator (DSTATCOM) for voltage flicker mitigation. The controller for DSTATCOM was designed based on DQ-model for the reactive power management which helps in the mitigation of …

Voltage And Power Quality Improvement Strategy For A Dfig Wind Farm During Variable Wind Conditions, L Meegahapola, T Littler, B Fox, J Kennedy, D Flynn

Dr Lasantha G Meegahapola

This paper presents a voltage and power quality enhancement scheme for a doubly-fed induction generator (DFIG) wind farm during variable wind conditions. The wind profiles were derived considering the measured data at a DFIG wind farm located in Northern Ireland (NI). The aggregated DFIG wind farm model was validated using measured data at a wind farm during variable generation. The voltage control strategy was developed considering the X/R ratio of the wind farm feeder which connects the wind farm and the grid. The performance of the proposed strategy was evaluated for different X/R ratios, and wind profiles with different characteristics. …

Impact On Transient And Frequency Stability For A Power System At Very High Wind Penetration, Lasantha Meegahapola, Damian Flynn

Dr Lasantha G Meegahapola

This paper analyzes the impact on transient and frequency stability for a power system at very high wind penetration (40% wind). Wind penetration is based on the doubly-fed induction generator (DFIG), and a systematic approach has been adopted for wind power integration. A sensitivity analysis has been carried out for each wind integration scenario and for different wind generator loading conditions. A range of fault locations has been selected for stability analysis based on the proximity to synchronous generation and wind farms. The analysis has shown that transient stability performance is subject to fault location in the network, especially when …

Optimal Allocation Of Reactive Power Resources To Minimise Losses And Maintain System Security, Eknath Vittal, Lasantha Meegahapola, Damian Flynn, Andrew Keane

Dr Lasantha G Meegahapola

Modern doubly-fed induction generator (DFIG) wind turbines have significant reactive power control capability, even during low wind speed conditions. This can improve system security by providing terminal voltage control at buses in the system. Generally, such control employs the full range of reactive power production from the turbine which can lead to increased system losses. By utilizing optimal power flow analysis, and limiting the range of reactive power production at certain wind farms, system losses can be minimized. If the reactive power of the wind farms are optimized to achieve the minimum system losses this may adversely affect the voltage …

Transient Stability Analysis Of A Power System With High Wind Penetration, Lasantha Meegahapola, Damian Flynn, Tim Littler

Dr Lasantha G Meegahapola

This paper presents transient stability analysis for a power system with high wind penetration. The transient stability has been evaluated based on two stability criteria: rotor angle stability and voltage stability. A modified IEEE-14 bus system has been used as the main study network and simulations have been conducted at several wind power penetration levels, defined as a fraction of total system generation. A wide range of scenarios have been presented based on the wind farm voltage at the point of connection, i.e. low voltage (LV) distribution level and high voltage (HV) transmission level, and the type of wind generator …

Multi-Objective Reactive Power Support From Wind Farms For Network Performance Enhancement, Lasantha Meegahapola, Brendan Fox, Tim Littler, Damian Flynn

Dr Lasantha G Meegahapola

This paper examines the ability of the doubly fed induction generator (DFIG) to deliver multiple reactive power objectives during variable wind conditions. The reactive power requirement is decomposed based on various control objectives (e.g. power factor control, voltage control, loss minimisation, and flicker mitigation) defined around different time frames (i.e. seconds, minutes, and hourly), and the control reference is generated by aggregating the individual reactive power requirement for each control strategy. A novel coordinated controller is implemented for the rotor-side converter and the grid-side converter considering their capability curves and illustrating that it can effectively utilise the aggregated DFIG reactive …

Voltage Security Constrained Reactive Power Optimization Incorporating Wind Generation, L G. Meegahapola, E Vittal, A Keane, D Flynn

Dr Lasantha G Meegahapola

This paper presents a comparative analysis between conventional optimal power flow (OPF) and voltage constrained OPF strategies with wind generation. The study has been performed using the New England 39 bus system with 12 doublyfed induction generator (DFIG) based wind farms installed across the network. A voltage security assessment is carried out to determine the critical wind farms for voltage stability enhancement. The power losses and individual wind farm reactive power generation have been compared with and without voltage stability constraints imposed on the OPF simulation. It is shown that voltage constrained OPF leads to much greater active power losses …

Dynamic Characteristics Of A Hybrid Microgrid With Inverter And Non- Inverter Interfaced Renewable Energy Sources: A Case Study, A V. Jayawardena, L G. Meegahapola, S Perera, D A. Robinson

Dr Lasantha G Meegahapola

Microgrids are becoming important constituents of electric power distribution networks. Microgrids are typically comprised of both inverter interfaced (e.g. double-fed induction generator (DFIG), solar-photovoltaic (PV) system) and non-inverter interfaced (e.g. synchronous generator) renewable energy generators (REGs), hence their dynamic characteristics are significantly different from the conventional grids comprised of centralised synchronous generators. Different inherent characteristics of REGs, power dispatch levels, relative REG capacities, and external grid characteristics are some of the important features of significant interest in relation to microgrid dynamic behaviour. For this study a microgrid model was developed in DIgSILENT Power Factory based on the IEEE-13 bus system …

Active Use Of Dfig Based Wind Farms For Transient Stability Improvement During Grid Disturbances, Lasantha Meegahapola, Damian Flynn, Jason Kennedy, Tim Littler

Dr Lasantha G Meegahapola

The doubly-fed induction generator (DFIG) now represents the dominant technology in wind turbine design. One consequence of this is limited damping and inertial response during transient grid disturbances. A 'decoupled' strategy is therefore proposed to operate the DFIG grid-side converter (GSC) as a static synchronous compensator (STATCOM) during a fault, supporting the local voltage, while the DFIG operates as a fixed-speed induction generator (FSIG) providing an inertial response. The modeling aspects of the decoupled control strategy, the selection of protection control settings, the significance of the fault location and operation at sub- and super-synchronous speeds are analyzed in detail. In …

Capability Curve Based Enhanced Reactive Power Control Strategy For Stability Enhancement And Network Voltage Management, Lasantha Meegahapola, Tim Littler, Sarath Perera

Dr Lasantha G Meegahapola

Reactive power has become a vital resource in modern electricity networks due to increased penetration of distributed generation. This paper examines the extended reactive power capability of DFIGs to improve network stability and capability to manage network voltage profile during transient faults and dynamic operating conditions. A coordinated reactive power controller is designed by considering the reactive power capabilities of the rotor-side converter (RSC) and the grid-side converter (GSC) of the DFIG in order to maximise the reactive power support from DFIGs. The study has illustrated that, a significant reactive power contribution can be obtained from partially loaded DFIG wind …

Fuzzy Logic And Artificial Neural Network Approaches In Odor Detection, Lasantha Meegahapola, J Karunadasa, Kasun Sandasiri, Damith Tharanga, Dammika Jayasekara

Dr Lasantha G Meegahapola

This paper presents the research segment of development of methodology for determining odor level of various applications using two different concepts; Fuzzy logic based algorithm and Artificial Neural Network (ANN) based algorithm. Three different gas sensors are used which respond to ammonia (NH3), hydrogen sulfide (H2S) and methane (CH4). Sensory fusion is achieved through processing the analog to digital converted values of sensor outputs using the algorithm to determine the odor level of various types of predetermined odors. Olfactometry was used to determine the desired outputs (odor levels) of the algorithms. Fuzzy logic algorithm uses Zadeh-Mamdani type Fuzzy inference system …

Optimization Of Frt Active Power Performance Of A Dfig During Transient Grid Faults, L Meegahapola, Damian Flynn, Tim Littler

Dr Lasantha G Meegahapola

Optimal fault ride-through (FRT) conditions for a doubly-fed induction generator (DFIG) during a transient grid fault are analyzed with special emphasis on improving the active power generation profile. The transition states due to crowbar activation during transient faults are investigated to exploit the maximum power during the fault and post-fault period. It has been identified that operating slip, severity of fault and crowbar resistance have a direct impact on the power capability of a DFIG, and crowbar resistance can be chosen to optimize the power capability. It has been further shown that an extended crowbar period can deliver enhanced inertial …

Flicker Propagation Analysis In Distribution Networks With Embedded Generation, D Perera, L Meegahapola, S Perera, P Ciufo

Dr Lasantha G Meegahapola

Embedded generators such as wind generators can produce observable voltage fluctuations during variable wind conditions hence flicker. The flicker produced by such intermittent and fluctuating generating sources can propagate to other parts of the distribution network while creating power quality issues in distribution feeders. This study presents a flicker emission analysis for a doubly-fed induction generator (DFIG) based wind farm and investigate the pertinent factors which influence flicker propagation and attenuation in distribution feeders. Study has shown that voltage fluctuations are significantly influenced by the attenuation characteristics of various load types (i.e. constant power, impedance and current loads) connected to …

Foreign Direct Investment And Uncertainty: Implications For Ethiopia, Adugna Lemi, Sisay Asefa

Adugna Lemi

The paper examines the effect of price and exchange rate uncertainty and political instability on the inflow of Foreign Direct Investment (FDI) to selected African economies. Measures of uncertainty of inflation rate and real exchange rate are incorporated by taking the conditional variance of the residual of the Autoregressive (AR) processes of each series. Pooled data result without accounting for country specific factors is misleading. Fixed effects model provides a better explanation of the variation of FDI flow to African economies. The results show that uncertainty in the rate of inflation and political instability constrain the flow of FDI only …

Do Foreign Direct Investment And Foreign Aid Promote Good Governance In Africa?, Adugna Lemi, Blen Solomon, Sisay Asefa

Adugna Lemi

The literature on the roles that governance/political and economic stability play to attract capital flows into African economies has been burgeoning. Good governance, liberalization, infrastructure, incentive packages have been regarded as cures to break the deadlock to reverse the economic plight, to attract inflow of capital and, in some cases, to reverse outflows of African economies. The flow of capital, however, has undesirable side effects on host economies’ working conditions, environmental standard, inequality, and culture, among others. These economic and social external or negative spillover effects are due to the phenomenon of “race-to-the-bottom” where companies invest in economies with lax …

Utilizing Gis To Examine The Relationship Between State Renewable Portfolio Standards And The Adoption Of Renewable Energy Technologies, Chelsea Schelly, Jessica Price

Department of Social Sciences Publications

In the United States, there is no comprehensive energy policy at the federal level. To address issues as diverse as climate change, energy security, and economic development, individual states have increasingly implemented Renewable Portfolio Standards (RPSs), which mandate that utility providers include a specified amount of electricity from renewable energy sources in their total energy portfolios. Some states have included incentives for individual energy technologies in their RPS, such as solar electric (also called photovoltaic or PV technology). Here, we use GIS to visualize adoption of RPSs and electricity generation from renewable energy sources in the US and examine changes …

Khodorkovsky & La Génesis De Los Mercados En Rusia, Víctor Pavón-Villamayor

Víctor Pavón-Villamayor

No abstract provided.

Church Bulletin, December 24, 2013

Church Bulletin

A newsletter published for Deaf Catholics in Ottawa, Canada

Church Bulletin Finding Aid

Stuck In The Moment: Cognitive Inflexibility In Preschoolers Following An Extended Time Period, Carolina Garcia, Anthony Steven Dick

Department of Psychology

Preschoolers display surprising inflexibility in problem solving, but seem to approach new challenges with a fresh slate. We provide evidence that while the former is true the latter is not. Here, we examined whether brief exposure to stimuli can influence children’s problem solving following several weeks after first exposure to the stimuli. We administered a common executive function task, the Dimensional Change Card Sort, which requires children to sort picture cards by one dimension (e.g., color) and then switch to sort the same cards by a conflicting dimension (e.g., shape). After a week or after a month delay, we administered …

Do Storybooks Really Break Children's Gender Stereotypes?, Carla Abad, Shannon M. Pruden

Department of Psychology

A book review on An open book: What and how young children learn from picture and storybooks. Special Issue of Frontiers in Developmental Psychology.

Edited by J.S. Horst and C. Houston-Price

Reid On Olfaction And Secondary Qualities, Jake Quilty-Dunn

Publications and Research

Thomas Reid is one of the primary early expositors of the “dual-component” theory of perception, according to which conscious perception constitutively involves a non-intentional sensation accompanied by a noninferential perceptual belief. In this paper, I will explore Reid's account of olfactory perception, and of odor as a secondary quality. Reid is often taken to endorse a broadly Lockean picture of secondary qualities, according to which they are simply dispositions to cause sensations. This picture creates problems, however, for Reid's account of how we perceive secondary qualities, including odors. Given Reid's insistence that we come to be aware of odors only …

Beyond Judicial Populism, Anil Kalhan

Anil Kalhan

No abstract provided.

Latinas And Electoral Politics: Expanding Participation And Power In State And National Elections, Anna Sampaio

Ethnic Studies

Latina and Latino political participation in the 2012 election reached new heights, proving to be a significant factor in the electoral outcomes of several battleground states and ultimately the reelection of President Obama. Both Latinas and Latinos played pivotal roles in the 2012 election, increasing their share of the national electorate and their support for President Obama over 2008 election levels. In the end, President Obama received 71 percent of the Latina/o vote (compared with 27 percent for Mitt Romney), surpassing all previous presidential candidates with the exception of Bill Clinton, who garnered 72 percent of the Latina/o vote in …

Students’ Perceived Utility Of Precision Taught Calculus, Rebecca- Anne Dibbs, David Glassmeyer, Wafa Yacoub

The Qualitative Report

The last decade of calculus research has showed students learn best when lecture is supplemented with thoughtful use of technology and group work; however, educators are given little direction of how they are to balance the already full first semester calculus class. Precision teaching is an instructional model that employs formative assessment to provide information on what topics are understood by students as well as indicate troublesome concepts. With this information, the instructor can adjust class time accordingly by incorporating supplemental activities most beneficial to students. The purpose of this interview study was to explore the perceived utility of precision …

How Does My Research Question Come About? The Impact Of Funding Agencies In Formulating Research Questions, Massimiliano Tarrozzi

The Qualitative Report

It is a widespread claim that the research question should primarily come from a careful literature analysis (Creswell, 2007). Actually, it is basically a good suggestion, mainly for novices, to avoid the mistake of choosing a research method only for ideological reasons, and far from the phenomenon that one is willing to explore. However, this idea does not take into account other complex phenomena involved in constructing a research question. First of all, the epistemological framework, which is never neutral and performs what I am supposed to investigate; second, the kind of funding agency, which has an indisputable impact not …

Negotiating Responsibility For Navigating Ethical Issues In Qualitative Research: A Review Of Miller, Birch, Mauthner, And Jessop’S (2012) Ethics In Qualitative Research, Second Edition, Michelle C.E. Mccarron

The Qualitative Report

Ethics in Qualitative Research (Miller, Birch Mauthner, & Jessop, 2012), now in its second edition, uses a feminist framework to present a variety of issues pertinent to qualitative researchers. Topics include traditional challenges for qualitative researchers (e.g., access to potential participants, informed consent, overlapping roles), as well as those that have garnered more attention in recent years, particularly with regard to uses and consequences of technological advances in research. The book is critical of committees whose function it is to review proposed research and grant research ethics approval (e.g., University Research Ethics Committees [URECs], Research Ethics Boards [REBs], and Institutional …

Measurement, Monitoring, And Evaluation Of State Demonstrations To Integrate Care For Dual Eligible Individuals: Massachusetts Evaluation Design Plan., Julie T. Fralich Mba, Maureen Booth Mrp, Ma, Edith G. Walsh Phd, Angela M. Greene Ms, Mba, Melissa Morley Phd, Wayne Anderson Phd

Disability & Aging

CMS contracted with RTI International to monitor the implementation of all State demonstrations under the Financial Alignment Initiative, and to evaluate their impact on beneficiary experience, quality, utilization, and cost. The evaluation includes an aggregate evaluation and State-specific evaluations. This report describes the State-specific Evaluation Plan for the Massachusetts demonstration as of December 16, 2013. The evaluation activities may be revised if modifications are made to either the Massachusetts demonstration or to the activities described in the Aggregate Evaluation Plan (Walsh et al., 2013). Although this document will not be revised to address all changes that may occur, the annual …

Open Source Integrated Library Systems In Public Libraries, Tony Brooke

School of Information Student Research Journal

One of the most fundamental decisions a library makes is choosing an integrated library system, or ILS. A public library can remove unwanted outside influence and save money by switching their ILS to free and open source software, or FOSS. This article is an examination of the progress made by FOSS ILSs to become not only contenders against proprietary systems, but also an appropriate choice for financial, functional, and philosophical reasons. Included is a timeline of published evaluations, the milestone of 14% adoption, a summary of the current landscape, and example implementation cases. A functional analysis shows why a public …