Coordinated control of DFIG’s rotor and grid side converters during network unbalance

This paper proposes a coordinated control of the rotor and grid side converters (RSC & GSC) of doubly-fed induction generator (DFIG) based wind generation systems under unbalanced voltage conditions. System behaviors and operations of the RSC and GSC under unbalanced voltage are illustrated. To provide enhanced operation, the RSC is controlled to eliminate the torque oscillations at double supply frequency under unbalanced stator supply. The oscillation of the stator output active power is then cancelled by the active power output from the GSC, to ensure constant active power output from the overall DFIG generation system. To provide the required positive and negative sequence currents control for the RSC and GSC, a current control strategy containing a main controller and an auxiliary controller is analyzed. The main controller is implemented in the positive (dq)+ frame without involving positive/negative sequence decomposition whereas the auxiliary controller is implemented in the negative sequence (dq)? frame with negative sequence current extracted. Simulation results using EMTDC/PSCAD are presented for a 2MW DFIG wind generation system to validate the proposed control scheme and to show the enhanced system operation during unbalanced voltage supply.

Distributed Consensus Charging for Current Unbalance Reduction

Electric Vehicle (EV) technology has developed rapidly in recent years, with the result that increasing levels of EV penetration are expected on electrical grids in the near future. The increasing electricity demand due to EVs is expected to provide many challenges for grid companies, and it is expected that it will be necessary to reinforce the current electrical grid infrastructure to cater for increasing loads at distribution level. However, by harnessing the power of Vehicle to Grid (V2G) technologies, groups of EVs could be harnessed to provide ancillary services to the grid. Current unbalance occurs at distribution level when currents are unbalanced between each of the phases. In this paper a distributed consensus algorithm is used to coordinate EV charging in order to minimise current unbalance. Simulation results demonstrate that the proposed algorithm is effective in rebalancing phase currents.

Coordinated Control of DFIG and FSIG-based Wind Farms under Unbalanced Grid Conditions

This paper investigates the control and operation of doubly-fed induction generator (DFIG) and fixed-speed induction generator (FSIG) based wind farms under unbalanced grid conditions. A DFIG system model suitable for analyzing unbalanced operation is developed, and used to assess the impact of an unbalanced supply on DFIG and FSIG operation. Unbalanced voltage at DFIG and FSIG terminals can cause unequal heating on the stator windings, extra mechanical stresses and output power fluctuations. These problems are particularly serious for the FSIG-based wind farm without a power electronic interface to the grid. To improve the stability of a wind energy system containing both DFIG and FSIG based wind farms during network unbalance, a control strategy of unbalanced voltage compensation by the DFIG systems is proposed. The DFIG system compensation ability and the impact of transmission network impedance are illustrated. The simulation results implemented in Matlab/Simulink show that the proposed DFIG control system improves not only its own performance, but also the stability of the FSIG system with the same grid connection point during network unbalance.

Change in UK construction: Moving towards supply chain collaboration

There has been an increasing highlight of supply chain collaboration in UK construction. However, few studies have provided evidence for the current status. Based on the analysis of over 100 questionnaire responses in this research, it is found that the UK construction industry as a whole is experiencing an important change and moving towards supply chain collaboration. On the other hand, an unbalance is found for the change movement. In addition to the questionnaire survey, a series of expert interviews help to explore the specific characteristics of supply chain collaboration in construction and provide practical implications for collaboration strategy implementation.

Establishing a nurse practitioner collaborative: evolution, development, and outcomes

The first Australian palliative care nurse practitioner (NP) was endorsed in 2003. In 2009 the Victoria Department of Health funded the development of the Victorian Palliative Care Nurse Practitioner Collaborative (VPCNPC). Its aim was to promote the NP role, develop resources, and provide education and mentorship to NPs, nurse practitioner candidates (NPCs), and health service managers. Four key objectives were developed: identify the demographic profile of palliative care NPCs in Victoria; develop an education curriculum and practical resources to support the training and education of palliative care NPCs and NPs; provide mentorship to NPs, NPCs, and service managers; and ensure effective communication with all key stakeholders. An NPC survey was also conducted to explore NPC demographics, models of care, the hours of study required for the role, the mentoring process, and education needs. This paper reports on the establishment of the VPCNPC, the steps taken to achieve its objectives, and the results of the survey. The NP role in palliative care in Australia continues to evolve, and the VPCNPC provides a structure and resources to clearly articulate the benefits of the role to nursing and clinical services. The advanced clinical practice role of the nurse practitioner (NP) has been well established in North America for several decades and across a range of specialties (Ryan-Woolley et al, 2007; Poghosyan et al, 2012). The NP role in Australia and the UK is a relatively new initiative that commenced in the early 2000s (Gardner et al, 2009). There are over 1000 NPs across all states and territories of Australia, of whom approximately 130 work in the state of Victoria (Victorian Government Health Information, 2012). Australian NPs work across a range of specialties, including palliative, emergency, older person, renal, cardiac, respiratory, and mental health care. There has been increasing focus nationally and internationally on developing academic programmes specifically for nurses working toward NP status (Gardner et al, 2006). There has been less emphasis on identifying the comprehensive clinical support requirements for NPs and NP candidates (NPCs) to ensure they meet all registration requirements to achieve and/or maintain endorsement, or on articulating the ongoing requirements for NPs once endorsed. Historically in Australia there has been a lack of clarity and limited published evidence on the benefits of the NP role for patients, carers, and health services (Quaglietti et al, 2004; Gardner and Gardner, 2005; Bookbinder et al, 2011; Dyar et al, 2012). An NP is considered to be at the apex of clinical nursing practice. The NP role typically entails comprehensively assessing and managing patients, prescribing medicines, making direct referrals to other specialists and services, and ordering diagnostic investigations (Australian Nursing and Midwifery Council, 2009). All NPs in Australia are required to meet the following generic criteria: be a registered nurse, have completed a Nursing and Midwifery Board of Australia approved postgraduate university Master's (nurse practitioner) degree programme, and be able to demonstrate a minimum of 3 years' experience in an advanced practice role (Nursing and Midwifery Board of Australia, 2011). An NPC in Victoria is a registered nurse employed by a service or organisation to work toward meeting the academic and clinical requirements for national endorsement as an NP. During the period of candidacy, which is of variable duration, NPCs consolidate their competence to work at the advanced practice level of an NP. The candidacy period is a process of learning the new role while engaging with mentors (medical and nursing) and accessing other learning opportunities both within and outside one's organisation to meet the educational requirements. Integral to the NP role is the development of a model of care that is responsive to identified service delivery gaps that can be addressed by the skills, knowledge, and expertise of an NP. These are unique to each individual service. The practice of an Australian NP is guided by national standards (Nursing and Midwifery Board of Australia 2014). It is defined by four overarching standards: clinical, education, research, and leadership. Following the initial endorsement of four Victorian palliative care NPs in 2005, there was a lull in recruitment. The Victoria Department of Health (DH) recognised the potential benefits of NPs for health services, and in 2008 it provided funding for Victorian public health services to scope palliative care NP models of care that could enhance service delivery and patient outcomes. The scoping strategy was effective and led to the appointment of 16 palliative care nurses to NPC positions over the ensuing 3 years. The NPCs work across a broad range of care settings, including inpatient, community, and outpatient in metropolitan, regional, and rural areas of Victoria. At the same time, the DH also funded the Centre for Palliative Care to establish the Victorian Palliative Care Nurse Practitioner Collaborative (VPCNPC) to support the NPs and NPCs. The Centre is a state-wide service that is part of St Vincent's Hospital Melbourne and a collaborative Centre of the University of Melbourne. Its primary function is to provide training and conduct research in palliative care. The purpose of the VPCNPC was to provide support and mentorship and develop resources targeted at palliative care NPs, NPCs, and health service managers. Membership of the VPCNPC is open to all NPs, NPCs, health service managers, and nurses interested in the NP role. The aim of this paper is to describe the development of the VPCNPC, its actions, and the outcomes of these actions.

EspZ of enteropathogenic and enterohemorrhagic Escherichia coli regulates type III secretion system protein translocation

UNLABELLED: Translocation of effector proteins via a type III secretion system (T3SS) is a widespread infection strategy among Gram-negative bacterial pathogens. Each pathogen translocates a particular set of effectors that subvert cell signaling in a way that suits its particular infection cycle. However, as effector unbalance might lead to cytotoxicity, the pathogens must employ mechanisms that regulate the intracellular effector concentration. We present evidence that the effector EspZ controls T3SS effector translocation from enteropathogenic (EPEC) and enterohemorrhagic (EHEC) Escherichia coli. Consistently, an EPEC espZ mutant is highly cytotoxic. Following ectopic expression, we found that EspZ inhibited the formation of actin pedestals as it blocked the translocation of Tir, as well as other effectors, including Map and EspF. Moreover, during infection EspZ inhibited effector translocation following superinfection. Importantly, while EspZ of EHEC O157:H7 had a universal "translocation stop" activity, EspZ of EPEC inhibited effector translocation from typical EPEC strains but not from EHEC O157:H7 or its progenitor, atypical EPEC O55:H7. We found that the N and C termini of EspZ, which contains two transmembrane domains, face the cytosolic leaflet of the plasma membrane at the site of bacterial attachment, while the extracellular loop of EspZ is responsible for its strain-specific activity. These results show that EPEC and EHEC acquired a sophisticated mechanism to regulate the effector translocation.

IMPORTANCE: Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) are important diarrheal pathogens responsible for significant morbidity and mortality in developing countries and the developed world, respectively. The virulence strategy of EPEC and EHEC revolves around a conserved type III secretion system (T3SS), which translocates bacterial proteins known as effectors directly into host cells. Previous studies have shown that when cells are infected in two waves with EPEC, the first wave inhibits effector translocation by the second wave in a T3SS-dependent manner, although the factor involved was not known. Importantly, we identified EspZ as the effector responsible for blocking protein translocation following a secondary EPEC infection. Interestingly, we found that while EspZ of EHEC can block protein translocation from both EPEC and EHEC strains, EPEC EspZ cannot block translocation from EHEC. These studies show that EPEC and EHEC employ a novel infection strategy to regulate T3SS translocation.

Integrated Optimal Power Flow for Distribution Networks in Local and Urban Scales

This paper develops an integrated optimal power flow (OPF) tool for distribution networks in two spatial scales. In the local scale, the distribution network, the natural gas network, and the heat system are coordinated as a microgrid. In the urban scale, the impact of natural gas network is considered as constraints for the distribution network operation. The proposed approach incorporates unbalance three-phase electrical systems, natural gas systems, and combined cooling, heating, and power systems. The interactions among the above three energy systems are described by energy hub model combined with components capacity constraints. In order to efficiently accommodate the nonlinear constraint optimization problem, particle swarm optimization algorithm is employed to set the control variables in the OPF problem. Numerical studies indicate that by using the OPF method, the distribution network can be economically operated. Also, the tie-line power can be effectively managed.