Power management and control strategies for efficient operation of a solar power dominated hybrid DC microgrid for remote power applications

In this paper, a hybrid DC microgrid consisting of a diesel generator with a rectifier, a solar photovoltaic (PV) system, and a battery energy storage system is presented in relation to an effective power management strategy and different control techniques are adopted to power electronic interfaces. The solar PV and battery energy storage systems are considered as the main sources of energy sources that supply the load demand on a daily basis whereas the diesel generator is used as a backup for the emergency operation of the microgrid. All system components are connected to a common DC bus through an appropriate power electronics devices (e.g., rectifier systems, DC/DC converter). Also a detailed sizing philosophy of all components along with the energy management strategy is proposed. Energy distribution pattern of each individual component has been conducted based on the monthly basis along with a power management algorithm. The power delivered by the solar PV system and diesel generator is controlled via DC-DC converterand excitation controllers which are designed based on a linearquadratic regulator (LQR) technique as as proportional integral (PI)controllers. The component level power distribution is investigatedusing these controllers under fluctuating load and solar irradiationconditions and comparative results are presented.

Promoting while checking self-interest : a conflict-based governance approach to rebalance corporate power disequilibria in Canada and the United States

La délégation du pouvoir de gestion aux administrateurs et aux gestionnaires, une caractéristique intrinsèque à la gestion efficace de grandes entreprises dans un contexte de capitalisme, confère une grande discrétion à l’équipe de direction. Cette discrétion, si elle n’est pas surveillée, peut mener à des comportements opportunistes envers la corporation, les actionnaires et les autres fournisseurs de capital qui n’ont pas de pouvoir de gestion. Les conflits entre ces deux classes d’agents peuvent émerger à la fois de décisions de gouvernance générale ou de transactions particulières (ie. offre publique d’achat). Dans les cas extrêmes, ces conflits peuvent mener à la faillite de la firme. Dans les cas plus typiques, ils mènent l’extraction de bénéfices privés pour les administrateurs et gestionnaires, l’expropriation des actionnaires, et des réductions de valeur pour la firme. Nous prenons le point de vue d’un petit actionnaire minoritaire pour explorer les méchanismes de gouvernance disponibles au Canada et aux États‐Unis. Après une synthèse dans la Partie 1 des théories sous‐jacentes à l’étude du pouvoir dans la corporation (séparation de la propriété et du contrôle et les conflits d’agence), nous concentrons notre analyse dans la Partie 2 sur les différents types de méchanismes (1) de gouvernance interne, (2) juridiques et (3) marchands, qui confèrent du pouvoir aux deux classes d’agents. Nous examinons comment les intérêts de ces deux classes peuvent être réalignés afin de prévenir et résoudre les conflits au sein de la firme. La Partie 3 explore un équilibre dynamique de pouvoir corporatif qui cherche à minimiser le potentiel d’opportunisme toute en préservant une quantité de discrétion suffisante pour la gestion efficace de la firme. Nous analysons des moyens pour renforcer les protections des actionnaires minoritaires et proposons un survol des pistes de réforme possibles.

Power and politics in a system implementation

The central concern of this study is to identify the role of power and politics in systems implementation. The current literature on systems implementation is typically divided into two areas, process modelling and factor based studies. Process modelling classifies the implementation into a linear process, whereas factor based studies have argued that in order to ‘successfully’ implement a system, particular critical factors are required. This literature misses the complexities involved in systems implementation through the human factors and political nature of systems implementation and is simplistic in its nature and essentially de-contextualises the implementation process. Literature has investigated some aspects of human factors in systems implementation. However, it is believed that these studies have taken a simplistic view of power and politics. It is argued in this thesis that human factors in systems implementation are constantly changing and essentially operating in a dynamic relationship affecting the implementation process. The concept of power relations, as proposed by Foucault (1976, 1977, 1978, 1980, 1982), have been utilised in order to identify the dynamic nature of power and politics. Foucault (1978) argued that power is a dynamic set of relationships constantly changing from one point in time to the next. It is this recognition that is lacking from information systems. Furthermore, these power relations are created through the use of discourse. Discourse represents meaning and social relationships, forming both subjectivity and power relations. Discourses are also the practices of talk, text and argument that continuously form that which actors speak. A post-structuralist view of power as both an obvious and hidden concept has provided the researcher a lens through which the selection and implementation of an enterprise-wide learning management system can be observed. The framework aimed to identify the obvious process of system selection implementation, and then deconstruct that process to expose the hegemonic nature of policy, the reproduction of organisational culture, the emancipation within discourse, and the nature of resistance and power relations. A critical case study of the selection and implementation of an enterprise-wide learning management system at the University of Australia was presented providing an in-depth investigation of the implementation of an enterprise-wide learning management system, spanning five years. This critical case study was analysed using social dramas to distinguish between the front stage issues of power and the hidden discourses underpinning the front stage dramas. The enterprise-wide learning management system implemented in the University of Australia in 2003 is a system which enables academic staff to manage learners, the students, by keeping track of their progress and performance across all types of training activities. Through telling the story of the selection and implementation of an enterprise-wide learning management system at the University of Australia discourses emerged. The key findings from this study have indicated that the system selection and implementation works at two levels. The low level is the selection and implementation process, which operates for the period of the project. The high level is the arena of power and politics, which runs simultaneously to the selection and implementation process. Challenges for power are acted out in the front stage, or public forums between various actors. The social dramas, as they have been described here, are superfluous to the discourse underpinning the front stage. It is the discourse that remains the same throughout the system selection and implementation process, but it is through various social dramas that reflect those discourses. Furthermore, the enactment of policy legitimises power and establishes the discourse, limiting resistance. Additionally, this research has identified the role of the ‘State’ and its influence at the organisational level, which had been previously suggested in education literature (Ball, 1990).

Change implementers’ resistance : considering power and resistance in IT implementation projects

Resistance is normally characterized as a set of behaviours located in and belonging to change recipients. Such behaviours are seen to thwart the legitimate aims of both change strategists and the change agents who implement systems and the associated organisational change on the strategists' behalf. However, results from our case study research indicate that resistance can be a property not only of change recipients’ behaviour, but also of change agents and change strategists. The resistance behaviours identified included the failure to follow a prescribed corporate method and template, a refusal to help or listen, a refusal to fix known problems, the display of an adversarial, confrontational, and/or condescending attitude, subversiveness, a poor work ethic, and a refusal to meet requests. This paper argues for a revised conceptualization of resistance as a behaviour that can be demonstrated by any IT project stakeholders, that cannot be divorced from considerations of power in the IT project context.

Power and influence in joint venture relationships and their impact on performance

The purpose of this research was to apply the concepts of power and influence tactics to the joint venture context by examining how they relate to venture performance. In addition, culture and the expectations of future cooperation were examined for their association with influence tactic use and joint venture performance. Data were collected from 58 parent firms of U.S.-based domestic and international joint ventures about their relationships with their partners.^ Under the theories of social exchange and power dependence, a parent's level of power is based on its partner's dependence on the relationship. The statistical results indicated that: (1) the greater the total of power of both parents in an equal power relationship, the greater the joint venture's performance; and (2) the greater the inequality between each parent's level of power, the lower the joint venture's performance. It was also found that the way in which a parent firm tried to influence its partner was related to joint venture performance. Specifically, the use of references to a partner's legitimate authority was negatively related to performance, while the use of rational arguments and compromises was positively related.^ Contrary to expectations, the cultural backgrounds of the parents were not shown to have a relationship to influence tactic use or joint venture's performance. On the other hand, greater expectation of future cooperation had a positive association with performance, and a significant relationship with influence tactic use. The greater the expectation, the less partners used more confrontational tactics such as pressure or legitimate authority. ^

An exploration of two female principals’ leadership in mainland China

Purpose: The purpose of this paper is to explore two dimensions of leadership practices (i.e. teaching and learning and sources of power) used by two exemplary principals in mainland China against a background of education reform and to identify how broader contextual factors have shaped these two dimensions of their leadership.--------- Design/methodology/approach: An exploratory case study was used that drew upon semi-structured interviews, observations and document analysis. Interviews were conducted with two principals, six teachers from each of the two schools and a superintendent who was the supervisor of the two principals.---------- Findings: The findings reveal that there are some common elements in both of the leaders’ practices but also some subtle differences. Both leaders emphasise teaching and learning. One sees herself as curriculum expert; the other delegate teaching responsibilities. While both uses a top down approach, one principal uses an adversarial approach and the other a more facilitative approach.---------- Research limitations/implications: The study used a small sample size. It explored the leaders’ practices in the light of broader contextual factors rather than personal factors or gender-based factors Originality/value – Given the limited empirical research conducted on female principals in mainland China, this qualitative study provides insights into two dimensions of leadership used by two exemplary principals and explains their practices in the light of critical contextual factors such as contemporary and traditional Chinese culture and the school’s organisational context.

Modeling dynamic demand response using Monte Carlo simulation and interval mathematics for boundary estimation

With the rapid development of various technologies and applications in smart grid implementation, demand response has attracted growing research interests because of its potentials in enhancing power grid reliability with reduced system operation costs. This paper presents a new demand response model with elastic economic dispatch in a locational marginal pricing market. It models system economic dispatch as a feedback control process, and introduces a flexible and adjustable load cost as a controlled signal to adjust demand response. Compared with the conventional “one time use” static load dispatch model, this dynamic feedback demand response model may adjust the load to a desired level in a finite number of time steps and a proof of convergence is provided. In addition, Monte Carlo simulation and boundary calculation using interval mathematics are applied for describing uncertainty of end-user's response to an independent system operator's expected dispatch. A numerical analysis based on the modified Pennsylvania-Jersey-Maryland power pool five-bus system is introduced for simulation and the results verify the effectiveness of the proposed model. System operators may use the proposed model to obtain insights in demand response processes for their decision-making regarding system load levels and operation conditions.

Desenvolvimento do clube de história da matemática: um diálogo das ciências humanas com a matemática

Este trabalho apresenta uma pesquisa sobre a utilização da História da Matemática no ensino básico do Colégio Militar do Rio de Janeiro CMRJ através de manifestações artísticas, fazendo uso, principalmente, do teatro,para que alunos percebam a matemática como uma ciência temporal, humana e sujeita a interferências políticas e sociais e, dessa forma, desenvolver a criticidade, aumentar a sensibilidade e o senso de solidariedade. A partir de um tema da história envolvendo fatos matemáticos os alunos pesquisam, escrevem uma peça teatral e encenam para um público formado por pessoas da comunidade escolar. Como a intenção é tornar essa prática efetiva, a pesquisa culmina na fundação do Clube de História da Matemática, espaço onde, espera-se, atividades recorrentes sejamdesenvolvidas, atraindo alunos afetos tanto às ciências humanas e sociais como às ciências exatas. Realiza-se um estudo de caso com observação participante, por ser o autor também professor do CMRJ. Este estudo busca referência teórica principalmente em autores relacionados à História da Matemática, Arte na Educação, gestão democrática, relações de poder e na legislação vigente. A pesquisa aponta a importância do trabalho com a história e com a arte e nos leva a concluir que, para formar cidadãos participativos e críticos, o primeiro passo é a sociedade tornar-se participativa e crítica, sendo a escola o principal locuspara tal formação.

Las TIC en la administración de la cadena de suministro y su incidencia en el desempeño operacional

Las tecnologías de la información han empezado a ser un factor importante a tener en cuenta en cada uno de los procesos que se llevan a cabo en la cadena de suministro. Su implementación y correcto uso otorgan a las empresas ventajas que favorecen el desempeño operacional a lo largo de la cadena. El desarrollo y aplicación de software han contribuido a la integración de los diferentes miembros de la cadena, de tal forma que desde los proveedores hasta el cliente final, perciben beneficios en las variables de desempeño operacional y nivel de satisfacción respectivamente. Por otra parte es importante considerar que su implementación no siempre presenta resultados positivos, por el contrario dicho proceso de implementación puede verse afectado seriamente por barreras que impiden maximizar los beneficios que otorgan las TIC.

Entrepreneurship: a long way to go

Entrepreneurship education has emerged as one popular research domain in academic fields given its aim at enhancing and developing certain entrepreneurial qualities of undergraduates that change their state of behavior, even their entrepreneurial inclination and finally may result in the formation of new businesses as well as new job opportunities. This study attempts to investigate the Colombian student´s entrepreneurial qualities and the influence of entrepreneurial education during their studies.

Power management and power flow control with back-to-back converters in a utility connected microgrid

This paper proposes a method for power flow control between utility and microgrid through back-to-back converters, which facilitates desired real and reactive power flow between utility and microgrid. In the proposed control strategy, the system can run in two different modes depending on the power requirement in the microgrid. In mode-1, specified amount of real and reactive power are shared between the utility and the microgrid through the back-to-back converters. Mode-2 is invoked when the power that can be supplied by the DGs in the microgrid reaches its maximum limit. In such a case, the rest of the power demand of the microgrid has to be supplied by the utility. An arrangement between DGs in the microgrid is proposed to achieve load sharing in both grid connected and islanded modes. The back-to-back converters also provide total frequency isolation between the utility and the microgrid. It is shown that the voltage or frequency fluctuation in the utility side has no impact on voltage or power in microgrid side. Proper relay-breaker operation coordination is proposed during fault along with the blocking of the back-to-back converters for seamless resynchronization. Both impedance and motor type loads are considered to verify the system stability. The impact of dc side voltage fluctuation of the DGs and DG tripping on power sharing is also investigated. The efficacy of the proposed control ar-rangement has been validated through simulation for various operating conditions. The model of the microgrid power system is simulated in PSCAD.

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.