Suomalaissotilaiden ja itäkarjalaisnaisten suhteet

Kirjallisuusarvostelu

Lapsi matkalla maailmaan ujostelemattomien kätilöiden avulla

Kirjallisuusarvostelu

Luonnonhaltijat ‒ haltijoita luonnonympäristössä? : Nature spirits : continuity and change : Conference of Belief Narrative Network of ISFNR, Zugdidi, Georgia 1.‒4.10.2014

Konferenssiraportti

Saamelaisen pienyhteisön uskomusperinteen motiivit ja kerronta

Kirjallisuusarvostelu

Tulospalkkausjärjestelmän kehittäminen startup-yrityksen näkökulmasta Case: Idea Roof

Työssä tutkitaan tulospalkkausjärjestelmän kehittämistä kohdeyritykselle.

Tulviin varautuminen ja tulvatiedottaminen Lapuan- ja Kyrönjoen pengerrysalueilla: kyselyn tulokset

Kyselyn laatiminen oli osa Tehostettu tulviin varautuminen ja tulvatiedottaminen -hanketta. Kyselyllä kartoitettiin Lapuan- ja Kyrönjoen pengerrysalueiden asukkaiden ja maanomistajien tiedontarvetta tulviin ja niihin varautumiseen liittyen. Samalla selvitettiin mahdollisen tulvavaroituspalvelun tarvetta ja toteutustapaa. Kysely tehtiin kesällä 2015.

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.

Intelligence in peace support operations

Finnish Defence Studies is published under the auspices of the National Defence College, and the contributions reflect the fields of research and teaching of the College. Finnish Defence Studies will occasionally feature documentation on Finnish Security Policy. Views expressed are those of the authors and do not necessarily imply endorsement by the National Defence College.