Phase voltage control and filtering in a converter-fed single-phase customer-end system of the LVDC distribution network

In recent years, the network vulnerability to natural hazards has been noticed. Moreover, operating on the limits of the network transmission capabilities have resulted in major outages during the past decade. One of the reasons for operating on these limits is that the network has become outdated. Therefore, new technical solutions are studied that could provide more reliable and more energy efficient power distributionand also a better profitability for the network owner. It is the development and price of power electronics that have made the DC distribution an attractive alternative again. In this doctoral thesis, one type of a low-voltage DC distribution system is investigated. Morespecifically, it is studied which current technological solutions, used at the customer-end, could provide better power quality for the customer when compared with the current system. To study the effect of a DC network on the customer-end power quality, a bipolar DC network model is derived. The model can also be used to identify the supply parameters when the V/kW ratio is approximately known. Although the model provides knowledge of the average behavior, it is shown that the instantaneous DC voltage ripple should be limited. The guidelines to choose an appropriate capacitance value for the capacitor located at the input DC terminals of the customer-end are given. Also the structure of the customer-end is considered. A comparison between the most common solutions is made based on their cost, energy efficiency, and reliability. In the comparison, special attention is paid to the passive filtering solutions since the filter is considered a crucial element when the lifetime expenses are determined. It is found out that the filter topology most commonly used today, namely the LC filter, does not provide economical advantage over the hybrid filter structure. Finally, some of the typical control system solutions are introduced and their shortcomings are presented. As a solution to the customer-end voltage regulation problem, an observer-based control scheme is proposed. It is shown how different control system structures affect the performance. The performance meeting the requirements is achieved by using only one output measurement, when operating in a rigid network. Similar performance can be achieved in a weak grid by DC voltage measurement. An additional improvement can be achieved when an adaptive gain scheduling-based control is introduced. As a conclusion, the final power quality is determined by a sum of various factors, and the thesis provides the guidelines for designing the system that improves the power quality experienced by the customer.

Metsäteollisuuden käännekohdat

Kirjallisuusarvostelu

Uskontomeemi ja elämän sattumat

Kirjallisuusarvostelu

IDEAS for Strategic Technology Management: Design of an electronically mediated scenario method

The age-old adage goes that nothing in this world lasts but change, and this generation has indeed seen changes that are unprecedented. Business managers do not have the luxury of going with the flow: they have to plan ahead, to think strategies that will meet the changing conditions, however stormy the weather seems to be. This demand raises the question of whether there is something a manager or planner can do to circumvent the eye of the storm in the future? Intuitively, one can either run on the risk of something happening without preparing, or one can try to prepare oneself. Preparing by planning for each eventuality and contingency would be impractical and prohibitively expensive, so one needs to develop foreknowledge, or foresight past the horizon of the present and the immediate future. The research mission in this study is to support strategic technology management by designing an effective and efficient scenario method to induce foresight to practicing managers. The design science framework guides this study in developing and evaluating the IDEAS method. The IDEAS method is an electronically mediated scenario method that is specifically designed to be an effective and accessible. The design is based on the state-of-the-art in scenario planning, and the product is a technology-based artifact to solve the foresight problem. This study demonstrates the utility, quality and efficacy of the artifact through a multi-method empirical evaluation study, first by experimental testing and secondly through two case studies. The construction of the artifact is rigorously documented as justification knowledge as well as the principles of form and function on the general level, and later through the description and evaluation of instantiations. This design contributes both to practice and foundation of the design. The IDEAS method contributes to the state-of-the-art in scenario planning by offering a light-weight and intuitive scenario method for resource constrained applications. Additionally, the study contributes to the foundations and methods of design by forging a clear design science framework which is followed rigorously. To summarize, the IDEAS method is offered for strategic technology management, with a confident belief that it will enable gaining foresight and aid the users to choose trajectories past the gales of creative destruction and off to a brighter future.

Energiapuuta Etelä-Savosta

Energiapuuta Etelä-Savosta hankkeessa tutkittiin ja kehitettiin energiapienpuun mahdollisuuksia osana suurimittakaavaista alueellista hankintaa. Energiapienpuun potentiaali suurimittakaavaisena polttoaineena on lupaava johtuen hyvästä biomassan saatavuudesta ja tarjontahalukkuudesta, korjuun teknologisesta edistyksestä ja logististen ratkaisujen monipuolisuudesta sekä käyttömäärien kasvusta. Hanke kokonaisuus sisälsi seuraavia osatutkimuksia: Etelä-Savon energiatase, metsänomistajakysely, asiantuntijahaastattelu, metsänkasvatussimulointi, metsäpolttoaineiden saatavuuslaskenta, puun kosteuden seurantatutkimus, logistiikan demonstraatioita sekä energiapuun hankintalogistiikan kustannusvertailuja. Hankkeessa käsiteltiin energiapienpuun arvoketjua metsänkasvatuksesta lopputuotteen käyttöön asti. Tutkimuksen tulokset osoittavat, että energiapienpuulla on mahdollisuudet suurimittakaavaisessa hankinnassa, kunhan toimitusketjussa panostetaan tehokkuuden ja laadun jatkuvaan parantamiseen.

Kohti parasta A-luokkaa

English version of this research report is available at: http://urn.fi/URN:ISBN:978-951-29-4615-0

Lypsäjän laulu

Kansanlaulu.

ähä, ähä (ämmät)

Kansanlaulu.

Onnelliset

Soitinnus: lauluäänet (2), piano.

Orpopojan valssi

Alkuperäislevy on HMV X2381.

Jannen hanuripolkka

Kansansävelmä.

Hankintasopimusten merkitys ja ohiostaminen julkisessa organisaatiossa

Hankintasopimusten merkitys ja ohiostaminen julkisessa organisaatiossa. Tutkielmassa käsitellään julkisen organisaation hankintojen johtamista ja tarkstellaan tähän liittyen hankintasopimusten noudattamista ja ohiostamista, sekä näihin liittyviä ilmiöitä.

Tuotannon läpäisyajan lyhentäminen kartiohammaspyöriä valmistavassa tehtaassa

Tutkimuksen tavoitteena oli selvittää keinot, joilla kartiohammaspyöriä valmistavan tuotantolinjan tuotannon läpäisyaika saadaan laskettua kahteen kalenteriviikkoon. Tutkimus perustui tarkkaan nykytila-analyysiin, joka suoritettiin haastatteluiden sekä tuotannonohjausjärjestelmästä saatavien tietojen perusteella. Nykytila-analyysin perusteella päädyttiin ratkaisumalliin, jossa pääkeinona tuotannon läpimenoajan pienentämiseen on keskeneräisen tuotannon määrän pienentäminen. Keskeneräisen tuotannon määrän pienentämisen lisäksi tutkittiin mahdollisuutta tuotannon kuorman tasoittamiseen, sekä toimintatapamuutoksiin lämpökäsittelyn yhteydessä. Tutkimuksen tuloksena luotiin järjestelmä tuotannon alkuvaiheisiin sitoutuneen keskeneräisen tuotannon pienentämiseksi, sekä tutkittiin lämpökäsittelyn toimintatapamuutoksista saatavaa hyötyä. Tutkimuksen tuloksena luotiin myös toimintamalli, jolla tuotannon läpäisyaika saadaan laskettua kahteen kalenteriviikkoon.