Optimized FTR portfolio construction: the speculator's problem

In this thesis, we propose a systematic methodology to construct an optimized financial transmission rights (FTR) portfolio for the speculator, who purchases FTR holdings in order to have returns that are as good as possible. The conventional approach of selecting the FTR in a portfolio requires the exhaustive evaluation of all the possible FTR combinations, which in a large-scale network is computationally too demanding a task, particularly when the wide variations in the behavior of the locational marginal price (LMP) differences of nodes over the many hours of the holding period are taken into account. In order to make the speculator's problem more manageable, we recast the problem into a form that allows us to exploit the salient characteristics of power systems, the topological nature of the underlying network and the historical data, so as to gain mathematical insights that we apply to develop the proposed scheme. The speculator returns are collected from the hourly day ahead markets (DAMs) only for those hours that the grid is congested, i.e., the flows on one or more lines are at their maximum limits. Each MW flowing through those lines incurs a transmission usage cost. Unlike a physical transaction from a source node to a sink node that holds FTR in the amount of the flow and receives reimbursement for the transmission usage charges from the independent grid operator (IGO), the speculator who holds FTR for the same node pair simply receives those revenues, because of lack of physical flows. Thus, the identification of congested lines is a key step in the construction methodology. So, rather than focusing on the LMP differences of node pairs to choose FTR, we select node pairs such that the selected congested lines are on their paths from the source nodes to the sink nodes. Conceptually, we specify FTR such that transactions with same node pairs and amounts induce real power flows on the selected congested lines. The strategy of the speculator is to select each congested line and his level of participation on the congested flows on the line. In practice, the speculator cannot do this for all the congested lines, because that would imply the acquisition of too large a number of FTR, whose premiums add to his costs and, thus, lower his returns. Under the assumption that the past behavior continues in the future, he judiciously chooses a subset of lines whose transmission usage costs exceeded the speculator's specified price and time fraction thresholds historically. This subset forms the basis of the optimized FTR portfolio construction. In our proposed scheme, we construct the FTR portfolio with minimum number of node pairs; i.e., we find the minimum number of transactions that induce the desired real power flows on the subset of selected lines. To demonstrate the computational efficiency of the construction algorithm, we select a subset of nodes to specify the FTR node pairs in the portfolio. The manageability of the problem is further aided by focusing on a small number of node pairs. Fewer node pairs improve the manageability. The recasting of the problem in terms of congested lines, rather than LMP differences of node pairs, results in a simplified solution methodology that is amenable to practical implementation. We have extensively tested the proposed methodology on multiple test systems and we discuss representative case study results. The results on three test systems, including the PJM ISO network, illustrate the effectiveness of the proposed approach and provide insights into the nature of the problem

Numerical Analysis of National Travel Data to Assess the Impact of UK Fleet Electrification

Accurately predicting the future power demand of electric vehicles is important for developing policy and industrial strategy. Here we propose a method to create a representative set of electricity demand profiles using survey data from conventional vehicles. This is achieved by developing a model which maps journey and vehicle parameters to an energy consumption, and applying it individually to the entire data set. As a case study the National Travel Survey was used to create a set of profiles representing an entirely electric UK fleet of vehicles. This allowed prediction of the required electricity demand and sizing of the necessary vehicle batteries. Also, by inferring location information from the data, the effectiveness of various charging strategies was assessed. These results will be useful in both National planning, and as the inputs to further research on the impact of electric vehicles

Enhanced automatic generation control with uncertainty

Maintaining reliability is a key aspect in power system operations. One process that helps in achieving this goal is automatic generation control (AGC), which is responsible for restoring the system frequency to the nominal value, and the real power interchange between balancing authority (BA) areas to the scheduled values. In this dissertation, we present the limitations of current AGC system implementations, and propose modifications in their design in order to increase their efficiency. The AGC system goal has become more challenging due to the radical transformations occurring in the structure and functionality of power systems. These transformations are enabled by the integration of new technologies, such as advanced communication and power electronics devices, and the deepening penetration of renewable resources. For example, renewable-based generation is highly variable and intermittent, and might undermine the objective of AGC systems. A framework that may be used to quantify the effects of various uncertainty sources, such as load variations, renewable-based generation, and noise in communication channels, on the system characteristics is presented in this dissertation. To this end, we develop a method to analytically propagate the uncertainty from the aforementioned sources to the system frequency and area control error (ACE), and obtain expressions that approximate their probability distribution functions. We make use of the proposed framework and derive probabilistic expressions of the frequency performance criteria, developed by the North American Electric Reliability Corporation (NERC). Such expressions may be used to determine the limiting values of uncertainty that the system may withstand. Our studies show that some advances are necessary in AGC system implementations, due to changes in power systems, such as the deregulation of the power industry and the integration of new technologies. The basic concept of AGC systems that is used by the BA areas has not changed severely over the past years. We aim in proposing AGC system modifications that are realistic and implementable in real large-scale systems. The high complexity of power systems is an obstacle when performing several processes related to reliability. In order to overcome such issues, we propose a systematic reduction of the synchronous generator model with low computational effort. In addition, we use the derived reduced model to describe a BA area dynamic behavior by including only the BA area variables. We use the developed models to design adaptive AGC systems, with self-tuning gain techniques, that decrease the unnecessary regulation and reduce the associated costs, since they take into account the actual system conditions in the determination of the control gains. Furthermore, each BA area implements its own AGC system. However, if all the BA areas were operated as one single BA area, then the regulation amounts as well as the associated costs would be less. Operating separately and locally, individual BA areas are obliged to purchase more expensive ancillary services to accommodate the variability and uncertainty from high penetration of renewable-based resources. Thus, some level of coordination between BA areas is favorable for all entities. We propose a coordination scheme between BA areas that would decrease the regulation amounts and costs. Our approach is inspired from trying to mimic the AGC system, in the scenario where all areas are assumed to be one single BA area. To this end, we use the individual ACEs of each BA area to approximate the ACE in the scenario where all BA areas are assumed to be a single BA area. Then, we allocate the approximated ACE to the individual AGC systems proportionally to their size. Next, we mimic the AGC allocation for the entire area without the need for exchanging cost information between the BA areas. To this end, we develop a distributed algorithm that provides the same solution as the centralized AGC allocation, with the total mismatch of regulation being the only information exchanged between BA areas. Moreover, the AGC dispatch in many independent system operators (ISOs) is determined through a market mechanism, as mandated by the restructuring of power systems. However, we investigate the possibility of using the economic signals from the real-time markets (RTMs) instead of having AGC markets for the AGC dispatch. To do so, we start out by giving the formulation of the economic dispatch (ED) process, which is used to clear the RTM, and use it to obtain appropriate economic signals. We also discuss that the quality of the AGC service provided is affected by the ramping characteristics of the regulating units chosen to participate in AGC. We propose a systematic method for the AGC dispatch taking into account the economic signals from the ED process as well as the quality of the AGC service provided. The proposed ideas are illustrated through several test systems. We choose small systems to provide insights into the proposed methodologies and large-scale systems to demonstrate their scalability

Σχεδιασμός πυργογερανού με μεταλλικό σκελετό

98 σ.Η εργασία αφορά το σχεδιασμό, τη μελέτη, τη στατική και δυναμική ανάλυση ενός πυργογερανού μεταλλικής προέλευσης, με την εφαρμογή του προγράμματος SOFISTIK 2003.Περιλαμβάνει μια εισαγωγή όσον αφορά την εξέλιξη των γερανών, τις μηχανικές αρχές τους και τις ιδιότητες των υλικών που χρησιμοποιούνται.Ακολουθεί η περιγραφή των βασικών στοιχείων της κατασκευής, οι διαστάσεις και οι διατομές των μελών της στο πρόγραμμα SOFISTIK.Αναλύονται οι δράσεις που επενεργούν στον γερανό, ενώ παρουσιάζονται τα αποτελέσματα των ελέγχων στην Οριακή Κατάσταση Αστοχίας και Λειτουργικότητας.Γίνεται ο έλεγχος της σύνδεσης μελών και εξάγονται συμπεράσματα για το σχεδιασμό του πυργογερανού.This paper is about the design, study, static and dynamic analysis of a metal crane, using the program SOFISTIK 2003.It includes an introduction about the historical evolution of cranes, their principles and the attribute of the materials which have been used.It has also been descripted the basic elements of the structure, their dimensions and their intersections in program SOFISTIK.We analyse the actions evolving the constuction and presentate the results of the control in bordering states.We export the conclusions as far as it concerned the design of the crane.Δήμητρα Γ. Αποστολοπούλο

Meanings and Functions in Olympic Consumption: A Study of the Athens 2004 Olympic Licensed Products

This is an exploratory study of the meanings and functions of one aspect of Olympic consumption, the purchase of Olympic licensed products. More specifically, the present study attempted to examine the value Olympic licensed items hold for their owners by uncovering the meanings attached to those items. Using the Athens 2004 Summer Olympic Games as the setting, 280 consumers responded to questions regarding their reasons for purchasing Olympic licensed products as well as how they intended to use those products. Furthermore, an effort was made to assess what those products meant for their owners. The findings of this study point to the highly symbolic meanings embedded in the consumption of Olympic licensed products. The symbolic meanings revealed centred around three main themes: the Olympic Movement, national identity, and national political history and achievement. To a lesser extent, experiential and functional meanings attached to Olympic licensed items were also identified

Power Transmission and Control in Microturbines’ Electronics: A Review

When the shaft rotates in microturbines, the rotational movement is converted to electrical power. This is achieved through a permanent magnet synchronous machine (PMSM) housed on the shaft and the power electronics components. To the best of the authors’ knowledge, articles that comprehensively describe the power transmission and control in the electrical part of microturbines have yet to be introduced, namely, the PMSM and power electronics. This review paper presents a detailed review of power conversion in each component of the electrical part of microturbines. The paper also reviews the existing literature on microturbines’ electrical performance, noting areas where progress has already been made as well as those where more research is still needed. Furthermore, the paper explains the control system in the electrical part of microturbines, outlining the grid synchronisation control approach for grid-connected microturbines and reviews the possibility of employing control strategies that engage the PMSM and power electronics as controllers for certain variables in microturbines, such as the shaft rotational speed and torque. Such control methods are more crucial in externally fired microturbines since traditional control strategies used in internally fired microturbines, such as thermal input regulation, are no longer an option in externally fired microturbines for controlling the shaft speed. The significance of higher switching frequencies in power electronics is also discussed. The higher switching frequency, the faster response to load variations and, therefore, the more reliable the control system. A greater switching frequency allows for reduced power loss, cost, and unit size. In this context, it is recommended in this review paper that future research consider using silicon carbide switching devices rather than silicon ones, which is the current practice, to build up the microturbines converters’ topology. The recommendation was motivated by looking at the existing literature that compares the switching frequency, size, cost, thermal endurance, and power losses of silicon and silicon carbide components in applications other than microturbines since initiatives of using silicon carbide in microturbine power electronics have not been reported in the literature, as far as the authors are aware. The electrical components of microturbines account for a third of the entire size and cost of the unit. This means that reducing the size and cost of the electronics contributes effectively to reducing the total size and cost. In applications other than microturbines, silicon carbide exhibited promising results compared to silicon in terms of size and long-term cost. Investigating silicon carbide in microturbines is worthwhile to see if it provides such promising benefits to the microturbine unit