A distributed approach to global feedback control of multi-agent systems

This paper presents a distributed approach to global state feedback control of for multi-agent systems. The proposed solution is obtained from the construction of decentralised functional observers. The required local control signal is generated asymptotically using only corresponding local output information. It is shown that a complete distribution of the control of a decentralised system having N agents can be achieved upon the satisfaction of some necessary conditions, and that the resulting controller can emulate the performance of a global state feedback controller. A step-by-step design algorithm is given. Its simplicity and correctness are illustrated through a numerical example.

Design of a distributed power system stabiliser

A new design method for a distributed power system stabiliser for interconnected power systems is introduced in this paper. The stabiliser is of a low order, dynamic and robust. To generate the required local control signals, each local stabiliser requires information about either the rotor speed or the load angle of the other subsystems. A simple MATLAB based design algorithm is given and used on a three-machine unstable power system. The resulting stabiliser is simulated and sample results are presented.

Risk and trust management for online distributed system

This thesis investigated the problem of strategic manipulation of feedback attacks and proposed an approach that makes trust management systems sufficiently robust against feedback manipulation attacks. The new trust management system enables potential service consumers to determine the risk level of a service before committing to proceed with the transaction.

The pragmatic portfolio : an assessment approach for distributed learning

Portfolios, especially where they involve some use of or link to online technologies, are currently a popular focus for learning innovation in universities, drawing on a tradition of using portfolios in some areas of higher education and attempting to extend and broaden this practice. In some cases this focus has led to ambitious plans for whole-of-institution approaches, often involving significant technological development. However, the term portfolio can also cover a wider variety of possible learning and assessment activities and there are ways of using portfolios which, while quite traditional in their own form and approach, enable teachers to approach other aspects of their curriculum and pedagogy in far more innovative ways. This paper explores the conceptual basis on which the Department of Internet Studies at Curtin University of Technology is utilising a pragmatic approach to portfolio assessment within individual units of study, so as to enable a more thorough implementation of distributed learning. In this form of learning, where students regularly contribute to their own and others' learning through short tasks and conversations, the evidence of achievement is widely distributed and not easily accessible for either formative or summative assessment. As explained in the paper, students are required to collate, select, and then contextualise a sample of these numerous productive moments of their ongoing study. The paper concludes that while other goals for portfolio assessment (such as encouraging reflection) can also be used with this approach, its primary value is in unleashing the potential of social media creativity in a manner that motivates students via the requirement of assessment, enables feedback to be provided to guide learning, and which promotes shared responsibility between teachers and students in determining the kind and extent of their learning activities.

Robust nonlinear distributed controller design for active and reactive power sharing in islanded microgrids

This paper presents a robust nonlinear distributed controller design for islanded operation of microgrids in order to maintain active and reactive power balance. In this paper, microgrids are considered as inverter-dominated networks integrated with renewable energy sources (RESs) and battery energy storage systems (BESSs), where solar photovoltaic generators act as RESs and plug-in hybrid electric vehicles as BESSs to supply power into the grid. The proposed controller is designed by using partial feedback linearization and the robustness of this control scheme is ensured by considering structured uncertainties within the RESs and BESSs. An approach for modeling the uncertainties through the satisfaction of matching conditions is also provided in this paper. The proposed distributed control scheme requires information from local and neighboring generators to communicate with each other and the communication among RESs, BESSs, and control centers is developed by using the concept of the graph theory. Finally, the performance of the proposed robust controller is demonstrated on a test microgrid and simulation results indicate the superiority of the proposed scheme under different operating conditions as compared to a linear-quadratic-regulator-based controller.

Understanding feedback report uptake: process evaluation findings from a 13-month feedback intervention in long-term care settings

BACKGROUND: Long-term care settings provide care to a large proportion of predominantly older, highly disabled adults across the United States and Canada. Managing and improving quality of care is challenging, in part because staffing is highly dependent on relatively non-professional health care aides and resources are limited. Feedback interventions in these settings are relatively rare, and there has been little published information about the process of feedback intervention. Our objectives were to describe the key components of uptake of the feedback reports, as well as other indicators of participant response to the intervention. METHODS: We conducted this project in nine long-term care units in four facilities in Edmonton, Canada. We used mixed methods, including observations during a 13-month feedback report intervention with nine post-feedback survey cycles, to conduct a process evaluation of a feedback report intervention in these units. We included all facility-based direct care providers (staff) in the feedback report distribution and survey administration. We conducted descriptive analyses of the data from observations and surveys, presenting this in tabular and graphic form. We constructed a short scale to measure uptake of the feedback reports. Our analysis evaluated feedback report uptake by provider type over the 13 months of the intervention. RESULTS: We received a total of 1,080 survey responses over the period of the intervention, which varied by type of provider, facility, and survey month. Total number of reports distributed ranged from 103 in cycle 12 to 229 in cycle 3, although the method of delivery varied widely across the period, from 12% to 65% delivered directly to individuals and 15% to 84% left for later distribution. The key elements of feedback uptake, including receiving, reading, understanding, discussing, and reporting a perception that the reports were useful, varied by survey cycle and provider type, as well as by facility. Uptake, as we measured it, was consistently high overall, but varied widely by provider type and time period. CONCLUSIONS: We report detailed process data describing the aspects of uptake of a feedback report during an intensive, longitudinal feedback intervention in long-term care facilities. Uptake is a complex process for which we used multiple measures. We demonstrate the feasibility of conducting a complex longitudinal feedback intervention in relatively resource-poor long-term care facilities to a wider range of provider types than have been included in prior feedback interventions.

Load frequency control of power systems with electric vehicles and diverse transmission links using distributed functional observers

This paper presents a load frequency control scheme using electric vehicles (EVs) to help thermal turbine units to provide the stability fluctuated by load demands. First, a general framework for deriving a state-space model for general power system topologies is given. Then, a detailed model of a four-area power system incorporating a smart and renewable discharged EVs system is presented. The areas within the system are interconnected via a combination of alternating current/high voltage direct current links and thyristor controlled phase shifters. Based on some recent development on functional observers, novel distributed functional observers are designed, one at each local area, to implement any given global state feedback controller. The designed observers are of reduced order and dynamically decoupled from others in contrast to conventional centralized observer (CO)-based controllers. The proposed scheme can cope better against accidental failures than those CO-based controllers. Extensive simulations and comparisons are given to show the effectiveness of the proposed control scheme.

Nonlinear DSTATCOM controller design for distribution network with distributed generation to enhance voltage stability

This paper presents a nonlinear controller design for a DSTATCOM connected to a distribution network with distributed generation (DG) to regulate the line voltage by providing reactive power compensation.The controller is designed based on the partial feedback linearization which transforms the nonlinear system into a reduced-order linear system and an autonomous system whose dynamics are known as internal dynamics of the system. This paper also investigates the stability of internal dynamics of a DSTATCOM as it is a basic requirement to design partial feedback linearizing controllers. The performance of the proposed controller is evaluated in terms reactive power compensation to enhance the voltage stability of distribution with DG.