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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Deployment of Autonomous Electric Taxis with Consideration for Charging Stations

Manickavasagam, Sounthar 30 May 2017 (has links)
Autonomous electric vehicles are set to replace most conventional vehicles in the near future. Extensive research is being done to improve efficiency at the individual and fleet level. There is much potential benefit in optimizing the deployment and rebalancing of Autonomous Electric Taxi Fleets (AETF) in cities with dynamic demand and limited charging infrastructure. We propose a Fleet Management System with an Online Optimization Model to assign idle taxis to either a region or a charging station considering the current demand and charging station availability. Our system uses real-time information such as demand in regions, taxi locations and state of charge (SoC), and charging station availability to make optimal decisions in satisfying the dynamic demand considering the range-based constraints of electric taxis. We integrate our Fleet Management System with MATSim, an agent-based transport simulator, to simulate taxis serving real on-demand requests extracted from the San Francisco taxi mobility dataset. We found our system to be effective in rebalancing and ensuring efficient taxi operation by assigning them to charging stations when depleted. We evaluate this system using different performance metrics such as passenger waiting time, fleet efficiency (taxi empty driving time) and charging station utilization by varying initial SoC of taxis, frequency of optimization and charging station capacity and power.
42

Utilização de unidades de microgeração fotovoltaica para regulação centralizada de tensão

Godoy, Lívia Lisandro Judice January 2017 (has links)
A Geração Distribuída no Brasil tem crescido ao longo dos anos, especialmente na fonte fotovoltaica e na categoria que a ANEEL denomina microgeração distribuída, que são centrais geradoras de energia elétrica com potência instalada menor ou igual a 75 kW e conectada na rede de distribuição por meio de instalações de unidades consumidoras. Apesar dos problemas tradicionais que podem ocorrer com a inserção em larga escala, como maiores perdas e desvios de tensão, as placas fotovoltaicas, conectadas à rede de distribuição por meio de um inversor, trazem a possibilidade de controlar a tensão no ponto de conexão, manipulando-se o fator de potência de saída do inversor, controlando a potência reativa. Neste contexto, considerando o uso dos inversores inteligentes com possibilidade de envio de sinal remotamente ao operador e a possibilidade de criação de Centros de Despacho de Geração Distribuída (CDGD), este trabalho tem por objetivo propor uma metodologia de regulação de tensão centralizada utilizando unidades de microgeração fotovoltaicas, em redes de distribuição com larga inserção. A metodologia proposta utiliza o conceito de despacho de potência reativa e fluxo de potência reativa ótimo, por meio de uma abordagem centralizada da rede, utilizando-se o software OpenDSS e MatLab, equipado com Algoritmo Genético (AG) para solucionar o problema de otimização. Para avaliar o desempenho do modelo, foram feitos estudos de caso no sistema IEEE 123 barras e em uma rede real em Alegrete. Os resultados obtidos validam a abordagem proposta, demonstra a aplicabilidade e limitações em casos reais. / The distributed generation in Brazil has increased in the past years, specially in photovoltaic power generation, at the category that Brazilian Electric Regulator ANEEL classifies as "distributed micro-generation", i.e., generation units in which the active power capacity is equal or bellow 75kW and conected on distribution network by the consumers. Despite the traditional problems that might occur due to high penetration of the units, e.g., higher losses and voltage sags and swells, they are conected to the network through an inverter that can be controlled in order to provide or consume reactive power, providing voltage regulation. In that context, considering the use of intelligent inverters that can be remotely operated by a centralized utility operator, this work aims to propose a centralized voltage regulation methodology using distributed micro-generation in distribution networks. The proposed methodology uses the concept of reactive power dispatch and optimal power flow, from a centralized view of the network, using the software MatLab and OpenDSS with Genetic Algorithm to solve the optimization problem. To evaluate the model, simulations were performed with the IEEE 123 bus system and with a real distribution network from the Alegrete city, in the Brazilian state of Rio Grande do Sul. The results show the proposed is valid, despite some limitations on real cases.
43

A distributed control approach to optimal economic dispatch of power generators

Cho, Brian Bumseok 01 December 2010 (has links)
In this dissertation, we propose a novel distributed approach to the control of generators in the electric grid. Specifically, we consider the problem of the optimal economic dispatch of generator; we present a simple, distributed algorithm, which adjusts the power-frequency set-points of generators to correct for power imbalances arising from generation and load fluctuations. In this algorithm each generator independently adjusts its real-power output based on its estimate of the aggregate power imbalance in the network; such as an estimate can be independently obtained by each generator through local measurements of the frequency deviation on the grid. Eventually, over the course of network operation, the distributed algorithm achieves the equal-marginal-cost power allocation among generators while driving the power imbalance exponentially to zero. In the absence of power losses, we prove the eventual optimality of the distributed algorithm under mild assumptions (strict convexity and positivity of cost functions) and present simulation results to compare its performance with traditional (centralized) dispatch algorithms. Furthermore, we present numerical simulation results that show that the distributed algorithm performs well even in the presence of power losses and other constraints. We argue that distributed control methods are especially attractive for electric grids with smart meters and other advanced capabilities at the end node and grids with high penetration of alternative energy generators and we identify interesting open problems for future work in this area.
44

A Cost Benefit Analysis of Using a Battery Energy Storage System (BESS) Represented by a Unit Commitment Model

Mihailovic, Nemanja 02 November 2018 (has links)
This thesis aims to provide a general overview of a cost and benefit analysis of incorporating a battery energy storage system within unit commitment model. The deregulation of the electricity market in the U.S. has only been around for the last two decades. With renewable energy and energy storage systems becoming less expensive, a decentralized market scheme is becoming more popular and plausible. The scope of this work is to provide a fundamental understanding of unit commitment and a cost analysis of applying a battery energy storage system to an already established power system. A battery energy storage system (BESS) was placed within a unit commitment schematic and modeled for a 7 day/168 hour forecast. Three models were generated, two with and one without the battery energy storage device (BESS). The comparison between the three systems was conducted to produce a visual economic justification to the feasibility of a BESS.
45

Narrative of Working Experience for the Managers Dispatched to China Return to Taiwan

Chen, Ming-Tien 31 July 2012 (has links)
In recent years, with the economic development in China and the direct flights between Taiwan and China; there are more and more Taiwanese enterprises invest in China industrial market. This business environment change results in the increasing Taiwanese employees travelling between China and Taiwan frequently, or even been dispatched to China for long-term. In the future, the opportunities of work exchange between Taiwan and China will increase rapidly. Taiwan and China has no language barrier, however, the thinking logic, attitude towards work, and corporate management style between two places are fairly divergent. All these differences impact both Taiwanese and Chinese enterprises development. Today, China¡¦s workers strive for their work and almost catch up with Taiwan. Do Taiwan¡¦s workers notice it? The author has been dispatched to China for more than five years, and returned to Taiwan for three years. We can see the way of business management and the working environment between Taiwan and China through the experience of author. This narrative will give an overview and suggestions to those Taiwanese who is willing to work in China, and to those Taiwanese who plan to return to Taiwan market. For the workers who are seeking for opportunities of work exchange, the author suggests they should have abilities such as authorization management, regulate the rhythm of the work, resource integration, and excellent communication skill with local workers. On the other hand, for the workers who return to Taiwan job market, face to the primary depression, adjust mindset, and balance work and family lives are the keys to a successful transfer.
46

Study of The Effect of The Policy of Industry¡¦s Heading West to China on The Inclination to Retain for Oversea Dispatching Staff - - To Take C Company as An Example

Lin, Shih-wei 19 August 2007 (has links)
In terms of global TFT-LCD industry, the most important competitors for Taiwan TFT-LCD industry are Korean Samsung & LG Philips (LPL) at present. To compete with them, it becomes one of the important strategies to work with Mainland China as working partners. The development of ¡§strategy of heading west to China¡¨ becomes the most direct way to reduce cost & maintain business. When managers prudently evaluate industry¡¦s heading west to China, how to reduce the conflict faced by the enterprise & employees is becoming one of the important issues for experts & enterprises recently. Referring to the interimportance & the interdependence of the criteria items that the experts selected in evaluation of the inclination to detain for oversea dispatching staff, AHP was applied to compare the interimportance of the clusters, and then ANP was applied to compare the interdependence of the clusters, and the expert questionnaires were collected. The interimportance of the questionnaires was calculated through AHP, and the interdependence was calculated through ANP in order to construct the weighting system of the inclination to detain for oversea dispatching staff, as the reference to the policy of oversea dispatch for the subject company. It can increase the scientific factors for human decisions. Data of C Company was analyzed through ANP & the findings were as follows. 1. The weight of all the criteria items for the effect of the policy of heading west to China on the inclination to detain for oversea dispatching staff. Criteria Item Weight Individual Factor Working Pressure 9.54% 59.82% Career Development 28.13% Individual Inclination 22.15% Organizational Factor Leadership 12.27% 40.18% Dispatch System 10.73% Supporting System 13.36% Organizational Culture 3.81% Total 100.00% 2. The Company should put primary stress on employees¡¦ career development. 3. In terms of increase in individual inclination, it becomes the primary consideration for supporting the policy of oversea dispatch that the company assists the employee family.
47

Stability Analysis and Economic Dispatch of an Isolated Power System with Wind Generators

Lai, Yu-chieh 07 July 2011 (has links)
The objective of this thesis is to investigate the transient response and optimal economic dispatch of an isolated power system with wind generators. Different types of wind turbines and the classification of Stability are introduced. Then, the process of Transient stability analysis and the concept of Genetic Algorithms are given for explanation. In this thesis, the practical power system of Kinmen is selected for case study. The disturbances introduced by gusting wind and N-1 system contingency are considered in the transient stability analysis. Furthermore, in order to obtain both accuracy and feasibility of the Optimal power dispatch by using Real-parameter Genetic Algorithms, the simulation results should be tested for the restrictions and requirements of the actual operation.
48

Narrative of Working Experience for the Managers Dispatched to China Return to Taiwan

CHEN, MING-TIEN 06 August 2012 (has links)
In recent years, with the economic development in China and the direct flights between Taiwan and China; there are more and more Taiwanese enterprises invest in China industrial market. This business environment change results in the increasing Taiwanese employees travelling between China and Taiwan frequently, or even been dispatched to China for long-term. In the future, the opportunities of work exchange between Taiwan and China will increase rapidly. Taiwan and China has no language barrier, however, the thinking logic, attitude towards work, and corporate management style between two places are fairly divergent. All these differences impact both Taiwanese and Chinese enterprises development. Today, China¡¦s workers strive for their work and almost catch up with Taiwan. Do Taiwan¡¦s workers notice it? The author has been dispatched to China for more than five years, and returned to Taiwan for three years. We can see the way of business management and the working environment between Taiwan and China through the experience of author. This narrative will give an overview and suggestions to those Taiwanese who is willing to work in China, and to those Taiwanese who plan to return to Taiwan market. For the workers who are seeking for opportunities of work exchange, the author suggests they should have abilities such as authorization management, regulate the rhythm of the work, resource integration, and excellent communication skill with local workers. On the other hand, for the workers who return to Taiwan job market, face to the primary depression, adjust mindset, and balance work and family lives are the keys to a successful transfer.
49

The operation of this atypical employment from the perspective of working enterprise in the consumer banking

TSAI, TSUN-CHING 24 January 2005 (has links)
As globalization is under its way, enterprises should take the turbulent business environment into account as the normal conditions. Furthermore, the advancement of information technology (IT) facilitates the information flow between departments inside and outside organization, and which brings us more convenient & flexible communication. The force of globalization and the IT impact is not only influence the employment systems, but also restructure the relationship among them. Following the dramatic change is that enterprises try their best to look for flexibility to cope with business needs. Unlike the traditional employment system, the dispatched employment is a system which involves the interaction among the three parties (dispatched worker, dispatch agency and working enterprise). The purpose of this research is to investigate the operation of this atypical employment from the perspective of working enterprise in the consumer banking. The method employed in this research is in-depth interview with eight cases. The purpose of interviewing can be classified into three aspects: 1. Understanding the operations of working enterprise associated with dispatched affairs, including reasons for employing dispatched workers, positions, and standards for selecting dispatch agency. 2. From the enterprises point of view, how the dispatch agencies dispatch their workers, including the services offered from dispatch agencies, recruiting, and the management of employment relationship, etc. 3. What are the expectations from the working enterprise, and how should the government and dispatch agency work hand in hand to make the whole process smoothly.
50

Study of Two-Objective Dynamic Power Dispatch Problem by Particle Swarm Optimization

Chen, Yi-Sheng 12 June 2009 (has links)
In recent years, the awareness of environmental protection has made the power dispatch model no longer purely economical-oriented. This thesis proposed the application of particle swarm optimization (PSO) algorithm and interactive compromise programming method to solve the 24-hour two-objective power dispatch problem. Considering simultaneously the lowest generating cost and the lowest pollution emission, the two mutually-conflicting objectives will choose a compromised dispatch model. This thesis joined the mixed-integer programming problem of optimal power flow (MIOPF) with the dynamic economic dispatch (DED), making this dispatch solution more realistic without electrical violations; The MIOPF considers both continuous and discrete types of variables. The continuous variables are the generating unit real power output and the generator-bus voltage magnitudes; the discrete variables are the shunt capacitor banks and transformer tap setting. Simulation were run on the standard IEEE 30 Bus system. In order to avoid the PSO local optimality problem, this thesis proposed the utilization of the PSO algorithm with time-varying acceleration coefficients (PSO_TVAC) plus the local random search method (LRS), so it can quickly and effectively reach the optimal solution, without advantages of performance and accuracy of PSO. This thesis also proposed the consideration of the available transfer capability (ATC) on transmission lines of the existing dispatch model. Applying sensitivity factors to calculate each generator¡¦s available transfer capability that can be offered in the analyzed time interval, enables the creation of a new constraint. Joined with the dynamic economic dispatch problem, it will make possible that a load client wishes to raise its demand. Simultaneously taking care of the minimum cost and the limits of system security, better dispatch results could be expected.

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