A management model is developed that determines the optimum economic recoverability of a particular hot -water geothermal reservoir undergoing exploitation for electric power generation. The management model integrates a physical model of the reservoir that predicts the areas of pressure decline due to withdrawals, and pressure rise due to reinjection of spent fluid, with a model of a two -stage steam turbine power plant that determines the quantity of electricity generated for a rate of hot -water extraction. Capital costs, variable costs and annual fixed costs are obtained for the reservoir development, extraction and reinjection, the transmission system, and the power plant. Revenues are determined for electrical power production. Application of the management model to a simplified, yet realistic example reservoir demonstrates that the methodology developed in this report can be used for analyzing the management of an integrated geothermal reservoir-power plant system.

The purpose of this dissertation describes several power optimization techniques for energy efficient datacenters. To achieve this goal, it approaches power dissipation holistically for entire datacenters and analyzes them layer-by-layer from (1) the infrastructure level, (2) the system level, and all the way down to (3) the micro-architecture level. First, for infrastructure-level power optimization of datacenters, this work presents infrastructure-level mathematical models and a holistic warehouse-scale datacenter power and performance simulator, SimWare. Experiments using SimWare show a high loss of cooling efficiency resulting from the non-uniform inlet air temperature distribution across servers. Second, this study describes a system-level technique, ATAC, which maximizes power efficiency while minimizing overheating. Finally, this dissertation describes a micro-architecture level technique under the context of emerging non-volatile memory technologies. We first show that storing more than one bit per cell, or multiple bits per cell, ends up with much higher soft-error rates than conventional technologies. However, multi-bit per cell technology can still be used as approximate storage. To this end, we propose a new class of multi-bit per cell memory in which both a precise bit and an approximate bit are located in a physical cell. With the development of these techniques, the contribution of this body of work is a reduction in the power consumption of datacenters in a holistic way, eliminating one of the most important hurdles to the proliferation of cloud-computing environments.

No description available.

Från den elektriska likströmsmotorn, till dagens komplexa trefassystem med motorer styrda av frekvensomformare, skapas det idag mer ”skräp” på elnätet än någonsin. Det har givit oss ett modernt problem som ofta är osynligt, men som kan ställa till med rejäl oreda om man har otur. Permascands fabrik är belägen i Ljungaverk och har problem med ljud i ett ställverk. Mätningar görs därför i anläggningen för att samla in mätdata och utifrån dessa skapa en nulägesbeskrivning när det gäller elkvalité. En tidigare mätning av anläggningen på grund av de upplevda problemen refereras i stora drag, som en bakgrundsgenomgång och förståelse för problemet. Ett steg i att upplysa personalen om begreppet elkvalité görs i samband med en studie i form av en enkät med en inledande text och några enkla frågor. Slutligen görs en jämförelse mellan fabriksanläggningen och en liknande anläggning på samma elnät, där uttaget av reaktiv effekt i förhållande till aktiv effekt studeras över tid. Under de mätningar som gjorts vid transformatorns nedsida visade det sig att det i förhållande till standarden EN 50160 finns för höga nivåer av flimmer. Utifrån den enkät som personalen vid fabriken fått besvara visar det sig att många inte känner till så mycket om begreppet elkvalité, men att man upplever att det är bra elkvalité vid fabriken. En rekomendation är att fortsätta arbetet med att söka efter ursprunget till kraftiga strömvariationer och de höga strömövertonshalterna då de påverkar transformatorn. Även att man på sikt budgeterar för att höja kunskapen om elkvalité bland de anställda för att kunna ta adekvata beslut vid inköp av utrustning. / From the electric DC-motor to today’s complex three-phase systems with motors controlled by frequency converters, more "junk" is created on the electric grid than ever. This has given us a modern problem that is often invisible, and can cause a substantial mess if you are unlucky. Permascand plant is located in Ljungaverk and has problems with sound in one of their switchgears. Measurements are therefore made in the plant to collect data and create a status report for power quality. A previous measurement of the plant, which was done because of the perceived problems, is refered in broad terms as a background review and understanding of the problem. One step to educate staff about the concept of power quality is done with a study in the form of a questionnaire with an introductory text and a few simple questions. Finally, a comparison is made between the plant and a similar factory on the same electric grid, where the reactive electrical energy is compared to the active electrical energy over time. During the measurements that were made at the transformer downside, it turned out that in relation to the standard EN 50160, there are high levels of flicker. Based on the questionnaire that staff at the plant had to answer, it turns out that many do not know much about the concept of power quality, but they feel that there is good power quality at the factory. A recommendation is to continue the work to find the origin to strong variations in the current and the harmonic current, because they affect the transformer. It is also recommended, that the budget in the long term is made to raise awareness of power quality among the employees, to be able to take proper decisions when purchasing new equipment.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

<p>The rapid development of wind power technology is reshaping conventional power grids in many countries across the world. As the installed capacity of wind power increases, its impact on power grids is becoming more important. To ensure the reliable operation of a power system which is significantly fed by wind power, the dynamics of the power system must be understood, and the purpose of this study is to develop suitable analytical tools for analysing the dynamic impact of large-scale wind parks on the stability of a power grid, and to investigate the possibility of improving the stabilisation and damping of the grid by smart control strategies for wind turbines.Many of the newer, larger turbines now being produced are variable speed turbines, which use doubly fed induction generators (DFIGs). These are induction generators which have their stator and rotor independently excited. When unconventional generators of this type are used in a power system, the system behaves differently under abnormal dynamic events.  For example, new types of generators cause different modes of oscillation in the power system, not only because of their dynamic characteristics, but also because they load the system differently.Very large power oscillations can occur in a power system as a result of internal disturbances.  Ordinarily these oscillations are slow and, in principle, it is possible to damp them with the help of wind power.  This leads to the idea of using a power system stabiliser (PSS) for a DFIG.  In order to damp oscillations in the system, it is necessary to understand the equipment causing these oscillations, and the methods to optimally damp the oscillations.Voltage stability is another important aspect of the safe operation of a power system. It has been shown that the voltage stability of a power system is affected by induction generators.  The voltage stability must therefore be carefully analysed in order to guard against a power system collapse.By using modal analysis and dynamic simulations, we show that the presence of a wind farm in the vicinity of a power system will improve the angular behaviour of the power system under small disturbances, but may decrease voltage stability under larger disturbances. We compare the performance of wind turbines to that of conventional synchronous generator power plants, and we show that a wind park consisting of DFIGs, which are equipped with PSSs, may be used as a positive contribution to power system damping.</p>

No description available.

<p>The rapid development of the global economics has made power systems allover the world become large-scale interconnected grids. This increases the capabilityof power grids to transfer power over the long distance to serve the desiredpower demand with the minimum cost of operation. Unfortunately, it alsoenables the propagation of local failures into global networks. In other words,if a blackout happens in a power system, the size and the damage may significantlyincrease.</p><p>One of the main ways in which blackouts become widespread is cascadingfailures. This type of failure originates after a critical component of the systemhas been removed fromthe service by protective relaying. As a consequence, theload handled by the failed component needs to be redistributed which mightcause an overloading on other components in the system.</p><p>On the other hand, the high power electronics controllable devices suchas Voltage Source Converters-based High Voltage Direct Current (VSC-HVDC)transmission are recently developed. These electronics devices have the potentialadvantages such as the ability to independently control active and reactivepower, and maintain voltage to be at acceptable level. Therefore, they are consideredto be the promising devices that with an appropriately designed controlstrategy, they can substantially improve the performance and reliability of thepower system.</p><p>This thesis presents the possibility to consider protection system status inthe control of VSC-HVDC link. A great deal of this research is development ofcoordination between this power electronic device and protection system which normally are considered separately. The derivation of protection system has been selected to determine the operation of VSC-HVDC. The methodology isbased on utilizing the signal created from a logical evaluation of relay and simplificationsof certain parameters. By introducing information from the relays tothe VSC-HVDC link via Central Control Unit (CCU), the modulation of transmitted power is devised in order to reduce the risk of system-wide failures. In turn,this means an avoided blackout.Furthermore, this thesis also includes the preliminary suggestion to selectthe location of VSC-HVDC. The methodology is based on predicting voltage instabilityusing voltage stability indices and related parameterswhich are derivedby using Singular ValueDecomposition method. The solutions indicate an effectivelocation for applying corrective action such as load shedding. This optimallocation is selected to reinforce the control strategy of VSC-HVDC in order toprevent cascading failures in the more encompassing systems.</p> / QC20100615

No description available.