Power Electronic Converters in Low-Voltage Direct Current Distribution – Analysis and Implementation

Over the recent years, smart grids have received great public attention. Many proposed functionalities rely on power electronics, which play a key role in the smart grid, together with the communication network. However, “smartness” is not the driver that alone motivates the research towards distribution networks based on power electronics; the network vulnerability to natural hazards has resulted in tightening requirements for the supply security, set both by electricity end-users and authorities. Because of the favorable price development and advancements in the field, direct current (DC) distribution has become an attractive alternative for distribution networks. In this doctoral dissertation, power electronic converters for a low-voltage DC (LVDC) distribution system are investigated. These include the rectifier located at the beginning of the LVDC network and the customer-end inverter (CEI) on the customer premises. Rectifier topologies are introduced, and according to the LVDC system requirements, topologies are chosen for the analysis. Similarly, suitable CEI topologies are addressed and selected for study. Application of power electronics into electricity distribution poses some new challenges. Because the electricity end-user is supplied with the CEI, it is responsible for the end-user voltage quality, but it also has to be able to supply adequate current in all operating conditions, including a short-circuit, to ensure the electrical safety. Supplying short-circuit current with power electronics requires additional measures, and therefore, the short-circuit behavior is described and methods to overcome the high-current supply to the fault are proposed. Power electronic converters also produce common-mode (CM) and radio-frequency (RF) electromagnetic interferences (EMI), which are not present in AC distribution. Hence, their magnitudes are investigated. To enable comprehensive research on the LVDC distribution field, a research site was built into a public low-voltage distribution network. The implementation was a joint task by the LVDC research team of Lappeenranta University of Technology and a power company Suur-Savon S¨ahk¨o Oy. Now, the measurements could be conducted in an actual environment. This is important especially for the EMI studies. The main results of the work concern the short-circuit operation of the CEI and the EMI issues. The applicability of the power electronic converters to electricity distribution is demonstrated, and suggestions for future research are proposed.

Tulosohjauksen kehittämiskohteet Rikosseuraamuslaitoksella

Diplomityön tavoitteena on Rikosseuraamuslaitoksen tulosohjauksen kuvaaminen, mää-rittely, arviointi ja kehitysehdotusten tekeminen. Lisäksi määritellään normi- ja informaa-tio-ohjaus sekä tarkastellaan kuinka ne näkyvät tulosohjauksessa. Informaatio-ohjauksesta tuodaan esille keskeisimpiä kehityskohteita. Toiminnan tehostamistarpeet johtuvat yleisestä taloustilanteesta ja sitä seuraavasta määrärahojen pienenemisestä. Aluksi pidettiin puolistrukturoidut haastattelut, joiden perusteella kuvattiin laitoksen pro-sessikartta. Tämän jälkeen tulos- ja normiohjauksesta tehtiin eritasoisia prosessikuvauk-sia. Kuvauksilla rajattiin ja selvennettiin tarkasteltavia prosesseja. Kirjallisuuden, tutki-musten ja selvitysten avulla kartoitettiin tulosohjauksen yleisiä kehityskohteita. Niitä ver-rattiin haastattelutietoihin, arvioitiin tulosohjauksen nykytilaa ja tehtiin kehitysehdotuksia. Tulosohjauksesta löytyi useita kehityskohteita. Strategisen toimenpidesuunnitelman edis-tymiseen tulisi tehdä raportointiaikataulu. Tulostavoitteita voisi valmistella enemmän työntekijälähtöisesti ja yksiköille tulisi laatia omat strategiat. Asiakaspalautekyselyä tulisi kehittää, toteuttaa se verkkopohjaisena ja ottaa käyttöön kaikissa yksiköissä. Mittarit tuli-si liittää ydinprosesseihin ja jakaa ne laitos-alue-yksikkö -tasoille. Säännölliset raportit tulisi automatisoida ja antaa niiden tulostusoikeudet käyttäjille. Lisäksi kehittämishankkeita ja projekteja voisi hieman vähentää mutta viedä ne tehokkaammin läpi. Normi- ja informaatio-ohjaus ovat kiinteä osa tulosohjausta. Normiohjaus perustuu pääasiassa säädöksiin ja informaatio-ohjaus tiedolla ohjaamiseen. Informaatio-ohjauksessa tulisi kiinnittää huomiota aluekeskuksen tiedottamiseen, ettei yksiköitä ohjata keskushallinnosta aluekeskuksen ohi. Keskushallinnon tulisi myös päivittää ohjeistukset nopeammin erityisesti lakimuutosten yhteydessä. Myös vastuuta voisi jakaa enemmän alueille. Käyttöön voisi ottaa uuden tiedotuskanavan, esimerkiksi sähköinen uutislehtinen tai info-näytöt taukotiloissa.

Macro- and Microevolution of Languages: Exploring Linguistic Divergence with Approaches from Evolutionary Biology

There are more than 7000 languages in the world, and many of these have emerged through linguistic divergence. While questions related to the drivers of linguistic diversity have been studied before, including studies with quantitative methods, there is no consensus as to which factors drive linguistic divergence, and how. In the thesis, I have studied linguistic divergence with a multidisciplinary approach, applying the framework and quantitative methods of evolutionary biology to language data. With quantitative methods, large datasets may be analyzed objectively, while approaches from evolutionary biology make it possible to revisit old questions (related to, for example, the shape of the phylogeny) with new methods, and adopt novel perspectives to pose novel questions. My chief focus was on the effects exerted on the speakers of a language by environmental and cultural factors. My approach was thus an ecological one, in the sense that I was interested in how the local environment affects humans and whether this human-environment connection plays a possible role in the divergence process. I studied this question in relation to the Uralic language family and to the dialects of Finnish, thus covering two different levels of divergence. However, as the Uralic languages have not previously been studied using quantitative phylogenetic methods, nor have population genetic methods been previously applied to any dialect data, I first evaluated the applicability of these biological methods to language data. I found the biological methodology to be applicable to language data, as my results were rather similar to traditional views as to both the shape of the Uralic phylogeny and the division of Finnish dialects. I also found environmental conditions, or changes in them, to be plausible inducers of linguistic divergence: whether in the first steps in the divergence process, i.e. dialect divergence, or on a large scale with the entire language family. My findings concerning Finnish dialects led me to conclude that the functional connection between linguistic divergence and environmental conditions may arise through human cultural adaptation to varying environmental conditions. This is also one possible explanation on the scale of the Uralic language family as a whole. The results of the thesis bring insights on several different issues in both a local and a global context. First, they shed light on the emergence of the Finnish dialects. If the approach used in the thesis is applied to the dialects of other languages, broader generalizations may be drawn as to the inducers of linguistic divergence. This again brings us closer to understanding the global patterns of linguistic diversity. Secondly, the quantitative phylogeny of the Uralic languages, with estimated times of language divergences, yields another hypothesis as to the shape and age of the language family tree. In addition, the Uralic languages can now be added to the growing list of language families studied with quantitative methods. This will allow broader inferences as to global patterns of language evolution, and more language families can be included in constructing the tree of the world’s languages. Studying history through language, however, is only one way to illuminate the human past. Therefore, thirdly, the findings of the thesis, when combined with studies of other language families, and those for example in genetics and archaeology, bring us again closer to an understanding of human history.