Load sharing and power quality enhanced operation of a distributed microgrid

This paper describes control methods for proper load sharing between parallel converters connected in a microgrid and supplied by distributed generators (DGs). It is assumed that the microgrid spans a large area and it supplies loads in both in grid connected and islanded modes. A control strategy is proposed to improve power quality and proper load sharing in both islanded and grid connected modes. It is assumed that each of the DGs has a local load connected to it which can be unbalanced and/or nonlinear. The DGs compensate the effects of unbalance and nonlinearity of the local loads. Common loads are also connected to the microgrid, which are supplied by the utility grid under normal conditions. However during islanding, each of the DGs supplies its local load and shares the common load through droop characteristics. Both impedance and motor loads are considered to verify the system response. The efficacy of the controller has been validated through simulation for various operating conditions using PSCAD. It has been found through simulation that the total Harmonic Distortion (THD) of the of the microgrid voltage is about 10% and the negative and zero sequence component are around 20% of the positive sequence component before compensation. After compensation, the THD remain below 0.5%, whereas, negative and zero sequence components of the voltages remain below 0.02% of the positive sequence component.

Power system stability analysis based on descriptive study of electrical indices

In a power network, when a propagation energy wave caused by a disturbance hits a weak link, a reflection is appeared and some of energy is transferred across the link. In this work, an analytical descriptive methodology is proposed to study the dynamical stability of a large scale power system. For this purpose, the measured electrical indices (angle, or voltage/frequency) following a fault in different points among the network are used, and the behaviors of the propagated waves through the lines, nodes and buses are studied. This work addresses a new tool for power system stability analysis based on a descriptive study of electrical measurements. The proposed methodology is also useful to detect the contingency condition and synthesis of an effective emergency control scheme.

Evaluation of aerial remote sensing techniques for vegetation management in power line corridors

The following paper presents an evaluation of airborne sensors for use in vegetation management in powerline corridors. Three integral stages in the management process are addressed including, the detection of trees, relative positioning with respect to the nearest powerline and vegetation height estimation. Image data, including multi-spectral and high resolution, are analyzed along with LiDAR data captured from fixed wing aircraft. Ground truth data is then used to establish the accuracy and reliability of each sensor thus providing a quantitative comparison of sensor options. Tree detection was achieved through crown delineation using a Pulse-Coupled Neural Network (PCNN) and morphologic reconstruction applied to multi-spectral imagery. Through testing it was shown to achieve a detection rate of 96%, while the accuracy in segmenting groups of trees and single trees correctly was shown to be 75%. Relative positioning using LiDAR achieved a RMSE of 1.4m and 2.1m for cross track distance and along track position respectively, while Direct Georeferencing achieved RMSE of 3.1m in both instances. The estimation of pole and tree heights measured with LiDAR had a RMSE of 0.4m and 0.9m respectively, while Stereo Matching achieved 1.5m and 2.9m. Overall a small number of poles were missed with detection rates of 98% and 95% for LiDAR and Stereo Matching.

Hybrid cascade converter topology with series connected symmetrical and asymmetrical diode-clamped H-Bridge cells

A novel H-bridge multilevel PWM converter topology based on a series connection of a high voltage (HV) diode-clamped inverter and a low voltage (LV) conventional inverter is proposed. A DC link voltage arrangement for the new hybrid and asymmetric solution is presented to have a maximum number of output voltage levels by preserving the adjacent switching vectors between voltage levels. Hence, a fifteen-level hybrid converter can be attained with a minimum number of power components. A comparative study has been carried out to present high performance of the proposed configuration to approach a very low THD of voltage and current, which leads to the possible elimination of output filter. Regarding the proposed configuration, a new cascade inverter is verified by cascading an asymmetrical diode-clamped inverter, in which nineteen levels can be synthesized in output voltage with the same number of components. To balance the DC link capacitor voltages for the maximum output voltage resolution as well as synthesise asymmetrical DC link combination, a new Multi-output Boost (MOB) converter is utilised at the DC link voltage of a seven-level H-bridge diode-clamped inverter. Simulation and hardware results based on different modulations are presented to confirm the validity of the proposed approach to achieve a high quality output voltage.

Cyber bullying in schools and the law : is there an effective means of addressing the power imbalance?

Cyber bullying – or bullying through the use of technology – is a growing phenomenon which is currently most commonly experienced by young people and the consequences manifested in schools. Cyber bullying shares many of the same attributes as face-to-face bullying such as a power imbalance and a sense of helplessness on the part of the target. Not surprisingly, targets of face-to-face bullying are increasingly turning to the law, and it is likely that targets of cyber bullying may also do so in an appropriate case. This article examines the various criminal, civil and vilification laws that may apply to cases of cyber bullying and assesses the likely effectiveness of these laws as a means of redressing that power imbalance between perpetrator and target.

Detection and Estimation of Nonstationary Power Transients

This chapter looks at issues of non-stationarity in determining when a transient has occurred and when it is possible to fit a linear model to a non-linear response. The first issue is associated with the detection of loss of damping of power system modes. When some control device such as an SVC fails, the operator needs to know whether the damping of key power system oscillation modes has deteriorated significantly. This question is posed here as an alarm detection problem rather than an identification problem to get a fast detection of a change. The second issue concerns when a significant disturbance has occurred and the operator is seeking to characterize the system oscillation. The disturbance initially is large giving a nonlinear response; this then decays and can then be smaller than the noise level ofnormal customer load changes. The difficulty is one of determining when a linear response can be reliably identified between the non-linear phase and the large noise phase of thesignal. The solution proposed in this chapter uses “Time-Frequency” analysis tools to assistthe extraction of the linear model.

Knowledge is not power, but it’s a start : young people and employment entitlements

This paper employs empirical evidence from a survey of Queensland secondary school students to examine their knowledge about their wages and working conditions. It does so within the theoretical lens of the Gagne (or Gagne-Briggs) theory of instruction, which centres on the content of learning and how learning is acquired (Gagne, Briggs & Wager, 1988). While Gagne articulates five categories of learning, our focus here is on two; verbal information or declarative knowledge (facts that people can declare), and procedural knowledge (the rules and procedures for achieving outcomes). We show that student workers know little about the instruments governing their employment, or their workplace entitlements. Of the total sample of year 9 and year 11 students surveyed (n=892), those students who worked, or who had worked in the past year (n=438), were asked to identify whether they were employed under an award, collective agreement or AWA. Eighty three per cent of students did not know which industrial instrument set their wages. We argue that if young workers do not have declarative knowledge of their entitlements, nor basic procedural knowledge about redress, then they are not in a position to deploy Gagne’s ‘cognitive strategies’ that would enable them to take action to ensure their working conditions meet legal minima. We advocate that young workers should be given summary information on their wages and other entitlements on appointment and that such summary information should be readily available on employers’ noticeboards and electronically on company websites, and that the information should include a brief summary of avenues for redressing issues of underpayment or sub-standard conditions.

Survival Power: An Empirical Analysis of Power in a Life and Death Situation

This paper seeks to identify what antecedents of power make it more or less likely for people to survive in a life-threatening situation.In particular, we look at the Titanic disaster as the life or death situation. Maritime disasters can be interpreted as quasi-natural experiments because every person is affected by the shock. True human nature becomes apparent in such a dangerous situation. Five antecedents of power are distinguished: physical strength, economic resources, nationality, social and moral factors. This empirical analysis supports the notion that power is a key determinant in extreme situations of life or death.

Cities in the airports 'shadow' : underlying interests and discretionary power in airport-region development

The previously distinct boundary between airports and their cities has become increasingly blurred as new interests and actors are identified as important stakeholders in the decision making process. As a consequence airport entities are more than ever seeking an integrated existence with their surrounding regions. While current planning strategies provide insights on how to improve and leverage land use planning in and around airports, emerging challenges for implementing and protecting these planning ideals stem from the governance shadows of development decisions. The thesis of this paper is that improving the identification, articulation and consideration of city and airport interests in the development approval process (between planning and implementation) can help avoid outcomes that hinder the ability of cities and their airports to meet their separate/mutual long-term objectives. By applying a network governance perspective to the pilot case study of Brisbane, analysis of overlapping and competing actor interests show how different governance arrangements facilitate (or impede) decision making that protects sustainable ‘airport region’ development. ---------- Contributions are made to airport and city development decision makers through the identification and analysis of effective and ineffective decision making pathways, and to governance literature by way of forwarding empirically derived frameworks for showing how actors protect their interests in the ‘crowded decision making domain’ of airport region development. This work was carried out through the Airport Metropolis Research Project under the Australian Research Council’s Linkage Projects funding scheme (LP0775225).

The power of a single prototype : sustainable fashion textile design and the prevention of carcinogenic melanoma

Is there a role for prototyping (sketching, pattern making and sampling) in addressing real world problems of sustainability (People, Profit, and Planet), in this case social/healthcare issues, through fashion and textiles research? Skin cancer and related illnesses are a major cause of disfigurement and death in New Zealand and Australia where the rates of Melanoma, a serious form of skin cancer, are four times higher than in the Northern Hemisphere regions of USA, UK and Canada (IARC, 1992). In 2007, AUT University (Auckland University of Technology) Fashion Department and the Health Promotion Department of Cancer Society - Auckland Division (CSA) developed a prototype hat aimed at exploring a barrier type solution to prevent facial and neck skin damage. This is a paradigm shift from the usual medical research model. This paper provides an overview of the project and examines how a fashion prototype has been used to communicate emergent social, environmental, personal, physiological and technological concerns to the trans-disciplinary research team. The authors consider how the design of a product can enhance and support sustainable design practice while contributing a potential solution to an ongoing health issue. Analysis of this case study provides an insight into prototyping in fashion and textiles design, user engagement and the importance of requirements analysis in relation to sustainable development. The analysis and a successful outcome of the final prototype have provided a gateway to future collaborative research and product development.

Enabling or "real" power and influence in leadership

On the theme of personal development, this conceptual article aims to provoke thought about power and influence in leadership by means of a short excursion into character depictions in J.R.R Tolkien’s The Lord of the Rings (1966). It is said of mythopoeic literature, the genre of Tolkien’s work, that the very simplicity of the lens “pares away distractions,” “opens the way to unexpected connections,...[and] draws attention to alternative modes of being and thinking” (Greene, 1994, p. 457). Taking the liberty of perceived applicability of Tolkien’s literary genius to motifs on leadership, this article provokes thinking on what constitutes “real” power and influence in leadership. It is contended that demonstrating real power and influence in leadership lies not in coercive tactics of wielding power over others but in withholding usurping power to work with and enable others to achieve worthwhile ends.

The rediscovery of traditional urbanism at Melrose Arch

Contemporary urban form, particularly in the cities of South Africa, lacks distinction and quality. The majority of developments are conceived as private and dislocated initiatives, surveiled enclaves with gated access being the only conduit to the outside world. Any concern for a positive contribution to the matrix of public activity is seldom a consideration. The urban form responds to the perception that traffic systems are paramount to the successful flux of the city in satisfying the escalating demands of vehicular movement. In contrast many of the urban centres around the world, the great historical centres of Europe, Americas and the Sub-Continent are admired and considered the ultimate models in urban experience. The colonnades, bazaars and boulevards hosting an abundance of street activity are the characteristics of such centres and are symptomatic of a city growth based on pedestrian movement patterns, an urbanism supportative of human interaction and exchange, a form which has nurtured the existence of a public realm. Through the understanding of the principles of traditional urbanism we may learn that the modernist paradigm of a contemporary suburbia has resulted in disconnected and separate land uses with isolated districts where a reliance on the car is essential rather than optional.