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.

The effects of derivative use on equity fund performance

Investing in mutual funds has become more popular than ever and the amount of money invested in mutual funds registered in Finland has hit its all-time high. Mutual funds provide a relatively low-cost method for private investors to invest in stock market and achieve diversified portfolios. In finance there is always a tradeoff between risk and return, where higher expected returns can usually be achieved only by taking higher risks. Diversifying the portfolio gets rid some of the risk but systematic risk cannot be diversified away. These risks can be managed by hedging the investments with derivatives. The use of derivatives should improve the performance of the portfolios using them compared to the funds that don’t. However, previous studies have shown that the risk exposure and return performance of derivative users does not considerably differ from nonusers. The purpose of this study is to examine how the use of derivatives affects the performance of equity funds. The funds studied were 155 equity funds registered in Finland in 2013. Empirical research was done by studying the derivative use of the funds during a 6-year period between 2008–2013. The performance of the funds was studied quantitatively by using several different performance measures used in mutual fund industry; Sharpe Ratio, Treynor Ratio, Jensen's alpha, Sortino Ratio, M2 and Omega Ratio. The effect of derivative use on funds' performance was studied by using a dummy variable and comparing performance measures of derivative-users and nonusers. The differences in performance measures between the two groups were analyzed with statistical tests. The hypothesis was that funds' derivative use should improve their performance relative to the funds that don't use them. The results of this study are in line with previous studies that state that the use of derivatives does not improve mutual funds' performance. When performance was measured with Jensen's alpha, funds that did not use derivatives performed better than the ones that used them. When measured with other performance measures, the results didn’t differ between two groups.

Tehohoitopotilaan siirtotiedote hoitotyön päätöksenteon tukena - retrospektiivinen asiakirja-analyysi vuosilta 2001-2013

Tuija Lehtikunnas: Intensive care patient handover document in support of decision-making in nursing work - Retrospective document analysis for the period 2001–2013 University of Turku, Faculty of Medicine, Nursing Science Annales Universitatis Turkuensis Turku 2016 ABSTRACT The continuity of care and flow of information must be ensured when transferring the responsibility of care, whether this is done within an organisation or from one organisation to another. The purpose of this study was to describe and compare the nursing handover documents of long-term intensive care patients and changes to these documents during the years 2001–2013. Research data comprehended long-term intensive care patient handover documents (N = 250). Data was gathered from one university hospital intensive care unit and subjected to a content analysis of technical implementation, structure and content at five different time points. In addition to this, the nursing handover documents were analysed from a nursing decision-making standpoint. Sub-data (n = 5 x 50) from the years 2001, 2002, 2004, 2006 and 2013 was gathered. The first sub-data was manual, written on paper with a pen. The rest of the sub-data obtained was entered in a dedicated intensive care information system. The study developed an intensive care patient nursing handover document analysis framework, which was used to deductively analyse the research data. The results indicated that the transitioning to electronic records reinforced structure and identification improving the reusability of data was increased. Although intensive care nursing was recorded on nursing handover documents more comprehensively in more recent sub-data, it was done selectively with regard to overall patient care, e.g. there are no entries concerning the psychological support and counselling of patients or family members. Nursing handover documents do not contain a systematic description of the patient's communication and functional capacity at the moment of transfer. The patient's condition at the moment of transfer is not clearly indicated on the handover documents. Plans for follow-up treatment are not recorded at all. Nursing decision-making is difficult to find on the nursing handover documents used as research data. The study developed a handover document model for intensive care nursing that supports nursing decision-making and the continuity of care. Developmental recommendations focus on the management of co-operation within organisations for ensuring the continuity of care and enhancing each area of nursing in recording nursing handover documents by planning nursing for the patient, taking follow-up treatment resources into consideration. Keywords: Intensive care nursing, nursing decision-making, nursing records, information flow, nursing handover document, continuity of care