Active power flow control in a distribution system using discontinuous voltage controller

stract This paper proposes a hybrid discontinuous control methodology for a voltage source converter (VSC), which is used in an uninterrupted power supply (UPS) application. The UPS controls the voltage at the point of common coupling (PCC). An LC filter is connected at the output of the VSC to bypass switching harmonics. With the help of both filter inductor current and filter capacitor voltage control, the voltage across the filter capacitor is controlled. Based on the voltage error, the control is switched between current and voltage control modes. In this scheme, an extra diode state is used that makes the VSC output current discontinuous. This diode state reduces the switching losses. The UPS controls the active power it supplies to a three-phase, four-wire distribution system. This gives a full flexibility to the grid to buy power from the UPS system depending on its cost and load requirement at any given time. The scheme is validated through simulation using PSCAD.

A Delphi study to validate an advanced practice nursing tool

Aim This paper is a report of a study conducted to validate an instrument for measuring advanced practice nursing role delineation in an international contemporary health service context using the Delphi technique. Background Although most countries now have clear definitions and competency standards for nurse practitioners, no such clarity exists for many advanced practice nurse roles, leaving healthcare providers uncertain whether their service needs can or should be met by an advanced practice nurse or a nurse practitioner. The validation of a tool depicting advanced practice nursing is essential for the appropriate deployment of advanced practice nurses. This paper is the second in a three-phase study to develop an operational framework for assigning advanced practice nursing roles. Method An expert panel was established to review the activities in the Strong Model of Advanced Practice Role Delineation tool. Using the Delphi technique, data were collected via an on-line survey through a series of iterative rounds in 2008. Feedback and statistical summaries of responses were distributed to the panel until the 75% consensus cut-off was obtained. Results After three rounds and modification of five activities, consensus was obtained for validation of the content of this tool. Conclusion The Strong Model of Advanced Practice Role Delineation tool is valid for depicting the dimensions of practice of the advanced practice role in an international contemporary health service context thereby having the potential to optimize the utilization of the advanced practice nursing workforce.

A study of abrasive water jet characteristics by CFD simulation

Computational fluid dynamics (CFD) models for ultrahigh velocity waterjets and abrasive waterjets (AWJs) are established using the Fluent 6 flow solver. Jet dynamic characteristics for the flow downstream from a very fine nozzle are then simulated under steady state, turbulent, two-phase and three-phase flow conditions. Water and particle velocities in a jet are obtained under different input and boundary conditions to provide an insight into the jet characteristics and a fundamental understanding of the kerf formation process in AWJ cutting. For the range of downstream distances considered, the results indicate that a jet is characterised by an initial rapid decay of the axial velocity at the jet centre while the cross-sectional flow evolves towards a top-hat profile downstream.

Innovative Products Project: Background Study

The Australian Research Council (ARC) Innovative Products Project aims to facilitate project innovation by exploring means to improve the diffusion of innovative products to road and bridge projects. It adopts a highly novel approach to achieve this end, developing three different ways of viewing the problem: (1) as a relational governance issue, (2) as an absorptive capacity issue and (3) as a knowlege intermediation issue. This report presents teh results of teh first phase of a three phase fieldwork program.

Development and interrater reliability testing of a telephone interview training programme for Australian nurse interviewers

Summary Background The final phase of a three phase study analysing the implementation and impact of the nurse practitioner role in Australia (the Australian Nurse Practitioner Project or AUSPRAC) was undertaken in 2009, requiring nurse telephone interviewers to gather information about health outcomes directly from patients and their treating nurse practitioners. A team of several registered nurses was recruited and trained as telephone interviewers. The aim of this paper is to report on development and evaluation of the training process for telephone interviewers. Methods The training process involved planning the content and methods to be used in the training session; delivering the session; testing skills and understanding of interviewers post-training; collecting and analysing data to determine the degree to which the training process was successful in meeting objectives and post-training follow-up. All aspects of the training process were informed by established educational principles. Results Interrater reliability between interviewers was high for well-validated sections of the survey instrument resulting in 100% agreement between interviewers. Other sections with unvalidated questions showed lower agreement (between 75% and 90%). Overall the agreement between interviewers was 92%. Each interviewer was also measured against a specifically developed master script or gold standard and for this each interviewer achieved a percentage of correct answers of 94.7% or better. This equated to a Kappa value of 0.92 or better. Conclusion The telephone interviewer training process was very effective and achieved high interrater reliability. We argue that the high reliability was due to the use of well validated instruments and the carefully planned programme based on established educational principles. There is limited published literature on how to successfully operationalise educational principles and tailor them for specific research studies; this report addresses this knowledge gap.

Power electronic converters for high power ultrasound transducers

Piezoelectric transducers convert electrical energy to mechanical energy and play a great role in ultrasound systems. Ultrasound power transducer performance is strongly related to the applied electrical excitation. To have a suitable excitation for maximum energy conversion, it is required to analyze the effects of input signal waveform, medium and input signal distortion on the characteristic of a high power ultrasound system (including ultrasound transducer). In this research, different input voltage signals are generated using a single-phase power inverter and a linear power amplifier to excite a high power ultrasound transducer in different medium (water and oil) in order to study the characteristic of the system. We have also considered and analyzed the effect of power converter output voltage distortions on the performance of the high power ultrasound transducer using a passive filter.

Multi-level knowledge transfer in software development outsourcing projects : the agency theory view

In recent years, software development outsourcing has become even more complex. Outsourcing partner have begun‘re- outsourcing’ components of their projects to other outsourcing companies to minimize cost and gain efficiencies, creating a multi-level hierarchy of outsourcing. This research in progress paper presents preliminary findings of a study designed to understand knowledge transfer effectiveness of multi-level software development outsourcing projects. We conceptualize the SD-outsourcing entities using the Agency Theory. This study conceptualizes, operationalises and validates the concept of Knowledge Transfer as a three-phase multidimensional formative index of 1) Domain knowledge, 2) Communication behaviors, and 3) Clarity of requirements. Data analysis identified substantial, significant differences between the Principal and the Agent on two of the three constructs. Using Agency Theory, supported by preliminary findings, the paper also provides prescriptive guidelines of reducing the friction between the Principal and the Agent in multi-level software outsourcing.

The University of Queensland St Lucia campus 1.22 MW photovoltaic array

At the time of its official opening on 15 July 2011, The University of Queensland 1.22 MW array was the largest flat-panel PhotoVoltaic (PV) array in Australia. This PV array consists of over 5000 Trina Solar 240 Wp polycrystalline silicon PV modules installed across four rooftops at the St Lucia campus. Grid connection was achieved with 85 12.5 kW three phase and four 5 kW single phase grid connect inverters manufactured by Power-One. The site also includes one 8.4 kWp SolFocus concentrating solar 2 axis tracking PV array. Site wide monitoring and data logging of all DC, AC and environmental quantities will allow this array to be a rich source of research data. The site will also include a 200 kW 400 kWh zinc bromine energy storage system by Redflow, and associated power quality metering and monitoring. This paper presents highlights of the project feasibility study which included a site survey, shading analysis, and technology and triple bottom line assessment. A detailed description of the final technical implementation including discussion of alterative options considered is given. Finally, example initial data showing yield, trends and early example experimental results are presented.

End-of-life care in the critical care setting : nurses' practices and factors affecting these practices

Background: Critical care units are designed and resourced to save lives, yet the provision of end-of-life care is a significant component of nursing work in these settings. Limited research has investigated the actual practices of critical care nurses in the provision of end-of-life care, or the factors influencing these practices. To improve the care that patients at the end of life and their families receive, and to support nurses in the provision of this care, further research is needed. The purpose of this study was to identify critical care nurses' end-of-life care practices, the factors influencing the provision of end-of-life care and the factors associated with specific end-of-life care practices. Methods: A three-phase exploratory sequential mixed-methods design was utilised. Phase one used a qualitative approach involving interviews with a convenience sample of five intensive care nurses to identify their end-of-life care experiences and practices. In phase two, an online survey instrument was developed, based on a review of the literature and the findings of phase one. The survey instrument was reviewed by six content experts and pilot tested with a convenience sample of 28 critical care nurses (response rate 45%) enrolled in a postgraduate critical care nursing subject. The refined survey instrument was used in phase three of this study to conduct a national survey of critical care nurses. Descriptive analyses, exploratory factor analysis and univariate general linear modelling was undertaken on completed survey responses from 392 critical care nurses (response rate 25%). Results: Six end-of-life care practice areas were identified in this study: information sharing, environmental modification, emotional support, patient and family-centred decision making, symptom management and spiritual support. The items most frequently identified as always undertaken by critical care nurses in the provision of end-of-life care were from the information sharing and environmental modification practice areas. Items least frequently identified as always undertaken included items from the emotional support practice area. Eight factors influencing the provision of end-of-life care were identified: palliative values, patient and family preferences, knowledge, preparedness, organisational culture, resources, care planning, and emotional support for nurses. Strong agreement was noted with items reflecting values consistent with a palliative approach and inclusion of patient and family preferences. Variation was noted in agreement for items regarding opportunities for knowledge acquisition in the workplace and formal education, yet most respondents agreed that they felt adequately prepared. A context of nurse-led practice was identified, with variation in access to resources noted. Collegial support networks were identified as a source of emotional support for critical care nurses. Critical care nurses reporting values consistent with a palliative approach and/or those who scored higher on support for patient and family preferences were more likely to be engaged in end-of-life care practice areas identified in this study. Nurses who reported higher levels of preparedness and access to opportunities for knowledge acquisition were more likely to report engaging in interpersonal practices that supported patient and family centred decision making and emotional support of patients and their families. A negative relationship was identified between the explanatory variables of emotional support for nurses and death anxiety, and the patient and family centred decision making practice area. Contextual factors had a limited influence as explanatory variables of specific end-of-life care practice areas. Gender was identified as a significant explanatory variable in the emotional and spiritual support practice areas, with male gender associated with lower summated scores on these practice scales. Conclusions: Critical care nurses engage in practices to share control with and support inclusion of families experiencing death and dying. The most frequently identified end-of-life care practices were those that are easily implemented, practical strategies aimed at supporting the patient at the end of life and the patient's family. These practices arguably require less emotional engagement by the nurse. Critical care nurses' responses reflected values consistent with a palliative approach and a strong commitment to the inclusion of families in end-of-life care, and these factors were associated with engagement in all end-of-life care practice areas. Perceived preparedness or confidence with the provision of end-of-life care was associated with engagement in interpersonal caring practices. Critical care nurses autonomously engage in the provision of end-of-life care within the constraints of an environment designed for curative care and rely on their colleagues for emotional support. Critical care nurses must be adequately prepared and supported to provide comprehensive care in all areas of end-of-life care practice. The findings of this study raise important implications, and informed recommendations for practice, education and further research.

Superior piezoelectric composite films : taking advantage of carbon nanomaterials

Piezoelectric composites comprising an active phase of ferroelectric ceramic and a polymer matrix have recently attracted numerous sensory applications. However, it remains a major challenge to further improve their electromechanical response for advanced applications such as precision control and monitoring systems. We hereby investigated the incorporation of graphene platelets (GnPs) and multi-walled carbon nanotubes (MWNTs), each with various weight fractions, into PZT (lead zirconate titanate)/epoxy composites to produce three-phase nanocomposites. The nanocomposite films show markedly improved piezoelectric coefficients and electromechanical responses (50%) besides an enhancement of ~200% in stiffness. Carbon nanomaterials strengthened the impact of electric field on the PZT particles by appropriately raising the electrical conductivity of epoxy. GnPs have been proved far more promising in improving the poling behavior and dynamic response than MWNTs. The superior dynamic sensitivity of GnP-reinforced composite may be caused by GnPs’ high load transfer efficiency arising from their two-dimensional geometry and good compatibility with the matrix. Reduced acoustic impedance mismatch resulted from the improved thermal conductance may also contribute to the higher sensitivity of GnP-reinforced composite. This research pointed out the potential of employing GnPs to develop highly sensitive piezoelectric composites for sensing applications.

Predicting voltage unbalance impacts of plug-in electric vehicles penetration in residential low-voltage distribution networks

Plug-in electric vehicles will soon be connected to residential distribution networks in high quantities and will add to already overburdened residential feeders. However, as battery technology improves, plug-in electric vehicles will also be able to support networks as small distributed generation units by transferring the energy stored in their battery into the grid. Even though the increase in the plug-in electric vehicle connection is gradual, their connection points and charging/discharging levels are random. Therefore, such single-phase bidirectional power flows can have an adverse effect on the voltage unbalance of a three-phase distribution network. In this article, a voltage unbalance sensitivity analysis based on charging/discharging levels and the connection point of plug-in electric vehicles in a residential low-voltage distribution network is presented. Due to the many uncertainties in plug-in electric vehicle ratings and connection points and the network load, a Monte Carlo-based stochastic analysis is developed to predict voltage unbalance in the network in the presence of plug-in electric vehicles. A failure index is introduced to demonstrate the probability of non-standard voltage unbalance in the network due to plug-in electric vehicles.

Control, operation and power sharing among parallel converter-interfaced DERs in a microgrid in the presence of unbalanced and harmonic loads

This paper demonstrates power management and control of DERs in an autonomous MG. The paper focuses on the control and performance of converter-interfaced DERs in voltage controlled mode. Several case studies are considered for a MG based on the different types of loads supplied by the MG (i.e. balanced three-phase, unbalanced, single-phase and harmonic loads). DERs are controlled by adjusting the voltage magnitude and angle in their converter output through droop control, in a decentralized concept. Based on this control method, DERs can successfully share the total demand of the MG in the presence of any type of loads. This includes proper total power sharing, unbalanced power sharing as well as harmonic power sharing, depending on the load types. The efficacy of the proposed power control, sharing and management among DERs in a microgrid is validated through extensive simulation studies using PSCAD/EMTDC.

A SiC-based matrix converter topology for inductive power transfer system

Typical inductive power transfer (IPT) systems employ two power conversion stages to generate a high-frequency primary current from low-frequency utility supply. This paper proposes a matrix-converter-based IPT system, which employs high-speed SiC devices to facilitate the generation of high-frequency current through a single power conversion stage. The proposed matrix converter topology transforms a three-phase low-frequency voltage system to a high-frequency single-phase voltage, which, in turn, powers a series compensated IPT system. A comprehensive mathematical model is developed and power losses are evaluated to investigate the efficiency of the proposed converter topology. Theoretical results are presented with simulations, which are performed in MATLAB/Simulink, in comparison to a conventional two-stage converter. Experimental evident of a prototype IPT system is also presented to demonstrate the applicability of the proposed concept.

Modeling and position-sensorless control of a dual-airgap axial flux permanent magnet machine for flywheel energy storage systems

This paper presents the modeling and position-sensorless vector control of a dual-airgap axial flux permanent magnet (AFPM) machine optimized for use in flywheel energy storage system (FESS) applications. The proposed AFPM machine has two sets of three-phase stator windings but requires only a single power converter to control both the electromagnetic torque and the axial levitation force. The proper controllability of the latter is crucial as it can be utilized to minimize the vertical bearing stress to improve the efficiency of the FESS. The method for controlling both the speed and axial displacement of the machine is discussed. An inherent speed sensorless observer is also proposed for speed estimation. The proposed observer eliminates the rotary encoder, which in turn reduces the overall weight and cost of the system while improving its reliability. The effectiveness of the proposed control scheme has been verified by simulations and experiments on a prototype machine.

Doubly Fed Induction Generator for wind energy generation using nine-switch power converter

A Three-Phase Nine-Switch Converter (NSC) topology for Doubly Fed Induction Generator in wind energy generation is proposed in this paper. This converter topology was used in various applications such as Hybrid Electric Vehicles and Uninterruptable Power Supplies. In this paper, Nine-Switch Converter is introduced in Doubly Fed Induction Generator in renewable energy application for the first time. It replaces the conventional Back-to-Back Pulse Width Modulated voltage source converter (VSC) which composed of twelve switches in many DFIG applications. Reduction in number of switches is the most beneficial in terms of cost and power switching losses. The operation principle of Nine-Switch Converter using SPWM method is discussed. The resulting NSC performance of rotor side current control, active power and reactive control are compared with Back-to Back voltage source converter performance. DC link voltage regulation using front end converter is also presented. Finally the simulation results of DFIG performances using NSC and Back-to-Back VSC are analyzed and compared.