Reflection on the use of rating and score cards for asset and service assessment

The concept of star rating council facilities has progressively gained traction in Australia following the work of Dean Taylor at Marochy Shire Council in Queensland in 2006 – 2007 and more recently by the Victorian STEP asset management program. The following paper provides a brief discussion on the use and merits of star rating within community asset management. We suggest that the current adoption of the star rating system to manage community investment in services is lacking in consistency. It is suggested that the major failing is a lack of clear understanding in the purpose being served by the systems. The discussion goes on to make some recommendations on how the concept of a star system could be further enhanced to serve the needs of our communities better.

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.

Power Quality Improvement Using Interline Voltage Controller

The concept of an interline voltage controller (IVOLCON) to improve the power quality in a power distribution system is discussed. An IVOLCON consists of two shunt voltage source converters (VSCs) that are joined through a common dc bus. The VSCs are connected to two different feeders. The main aim of the IVOLCON is to control the PCC (Point of Common Coupling) bus voltages of the two feeders to pre-specified magnitudes. The phase angles of the PCC bus voltages are obtained such that the voltage across the common dc link remains constant. The structure, control and capability of the IVOLCON are described. The efficacy of the proposed configuration has been verified through simulation studies using PSCAD/EMTDC for voltage sags and feeder outage

Controller structure and design of firing angle controllers for (unit connected) HVDC systems

This paper investigates the control of a HVDC link, fed from an AC source through a controlled rectifier and feeding an AC line through a controlled inverter. The overall objective is to maintain maximum possible link voltage at the inverter while regulating the link current. In this paper the practical feedback design issues are investigated with a view of obtaining simple, robust designs that are easy to evaluate for safety and operability. The investigations are applicable to back-to-back links used for frequency decoupling and to long DC lines. The design issues discussed include: (i) a review of overall system dynamics to establish the time scale of different feedback loops and to highlight feedback design issues; (ii) the concept of using the inverter firing angle control to regulate link current when the rectifier firing angle controller saturates; and (iii) the design issues for the individual controllers including robust design for varying line conditions and the trade-off between controller complexity and the reduction of nonlinearity and disturbance effects

Poisson, Poisson-gamma and zero-inflated regression models of motor vehicle crashes: balancing statistical fit and theory

There has been considerable research conducted over the last 20 years focused on predicting motor vehicle crashes on transportation facilities. The range of statistical models commonly applied includes binomial, Poisson, Poisson-gamma (or negative binomial), zero-inflated Poisson and negative binomial models (ZIP and ZINB), and multinomial probability models. Given the range of possible modeling approaches and the host of assumptions with each modeling approach, making an intelligent choice for modeling motor vehicle crash data is difficult. There is little discussion in the literature comparing different statistical modeling approaches, identifying which statistical models are most appropriate for modeling crash data, and providing a strong justification from basic crash principles. In the recent literature, it has been suggested that the motor vehicle crash process can successfully be modeled by assuming a dual-state data-generating process, which implies that entities (e.g., intersections, road segments, pedestrian crossings, etc.) exist in one of two states—perfectly safe and unsafe. As a result, the ZIP and ZINB are two models that have been applied to account for the preponderance of “excess” zeros frequently observed in crash count data. The objective of this study is to provide defensible guidance on how to appropriate model crash data. We first examine the motor vehicle crash process using theoretical principles and a basic understanding of the crash process. It is shown that the fundamental crash process follows a Bernoulli trial with unequal probability of independent events, also known as Poisson trials. We examine the evolution of statistical models as they apply to the motor vehicle crash process, and indicate how well they statistically approximate the crash process. We also present the theory behind dual-state process count models, and note why they have become popular for modeling crash data. A simulation experiment is then conducted to demonstrate how crash data give rise to “excess” zeros frequently observed in crash data. It is shown that the Poisson and other mixed probabilistic structures are approximations assumed for modeling the motor vehicle crash process. Furthermore, it is demonstrated that under certain (fairly common) circumstances excess zeros are observed—and that these circumstances arise from low exposure and/or inappropriate selection of time/space scales and not an underlying dual state process. In conclusion, carefully selecting the time/space scales for analysis, including an improved set of explanatory variables and/or unobserved heterogeneity effects in count regression models, or applying small-area statistical methods (observations with low exposure) represent the most defensible modeling approaches for datasets with a preponderance of zeros

Further notes on the application of zero-inflated models in highway safety

The intent of this note is to succinctly articulate additional points that were not provided in the original paper (Lord et al., 2005) and to help clarify a collective reluctance to adopt zero-inflated (ZI) models for modeling highway safety data. A dialogue on this important issue, just one of many important safety modeling issues, is healthy discourse on the path towards improved safety modeling. This note first provides a summary of prior findings and conclusions of the original paper. It then presents two critical and relevant issues: the maximizing statistical fit fallacy and logic problems with the ZI model in highway safety modeling. Finally, we provide brief conclusions.

Post-occupancy analysis of a Zero Energy Hojme (ZEH)

Zero energy buildings (ZEB) and zero energy homes (ZEH) are a current hot topic globally for policy makers (what are the benefits and costs), designers (how do we design them), the construction industry (can we build them), marketing (will consumers buy them) and researchers (do they work and what are the implications). This paper presents initial findings from actual measured data from a 9 star (as built), off-ground detached family home constructed in south-east Queensland in 2008. The integrated systems approach to the design of the house is analysed in each of its three main goals: maximising the thermal performance of the building envelope, minimising energy demand whilst maintaining energy service levels, and implementing a multi-pronged low carbon approach to energy supply. The performance outcomes of each of these stages are evaluated against definitions of Net Zero Carbon / Net Zero Emissions (Site and Source) and Net Zero Energy (onsite generation v primary energy imports). The paper will conclude with a summary of the multiple benefits of combining very high efficiency building envelopes with diverse energy management strategies: a robustness, resilience, affordability and autonomy not generally seen in housing.

Governmentality and the reflection of legal educators : assessment practices as a case study

This paper presents a conceptual framework, informed by Foucault’s work on governmentality, which allows for new kinds of reflection on the practice of legal education. Put simply, this framework suggests that legal education can be understood as a form of government that relies on a specific rationalisation and programming of the activities of legal educators, students, and administrators, and is implemented by harnessing specific techniques and bodies of ‘know-how’. Applying this framework to assessment at three Australian law schools, this paper highlights how assessment practices are rationalised, programmed, and implemented, and points out how this government shapes students’ legal personae. In particular, this analysis focuses on the governmental effects of pedagogical discourses that are dominant within the design and scholarship of legal education. It demonstrates that the development of pedagogically-sound regimes of assessment has contributed to a reformulation of the terrain of government, by providing the conditions under which forms of legal personae may be more effectively shaped, and extending the power relations that achieve this. This analysis provides legal educators with an original way of reflecting on the power effects of teaching the law, and new opportunities for thinking about what is possible in legal education.

Operation and control of hybrid microgrid with angle droop controller

This paper compares the performance of two droop control schemes in a hybrid microgrid. With presence of both converter interfaced and inertial sources, the droop controller share power in a decentralized fashion. Both the droop controllers facilitate reactive power sharing based on voltage droop. However in frequency droop control, the real power sharing depends on the frequency, while in angle droop control, it depends on output voltage angle. For converter interfaced sources this reference voltage is tracked while for inertial DG, reference power for the prime mover is calculated from the reference angle with the proposed angle control scheme. This coordinated control scheme shows significant improvement in system performance. The comparison with the conventional frequency droop shows that the angle control scheme shares power with much lower frequency deviation. This is a significant improvement particularly in a frequent load changing scenario.

Free surface flow into a horizontal slot with zero gravity

The two-dimensional free surface flow of a finite-depth fluid into a horizontal slot is considered. For this study, the effects of viscosity and gravity are ignored. A generalised Schwarz-Christoffel mapping is used to formulate the problem in terms of a linear integral equation, which is solved exactly with the use of a Fourier transform. The resulting free surface profile is given explicitly in closed-form.

Beyond the controller

Performance / presentation given at Freeplay 2010, Melbourne, Victoria as an invited guest for a session entitled "Beyond the controller" This performance intended to review the follies of tangible interface design for games since the appearance of games specific control peripherals in the 1980s. In this work I examine: Technology as prosthesis – designed artefacts that enable interaction in a virtual world; Technology as the dream of virtuality – mind-ware. IN each instance the controller DICTATES the form of interaction