Factors Affecting Efficiency of LVDC Distribution Network – Power Electronics Perspective

The power distribution network will be changed towards the future Smart Grid due to increased number of installed renewable power generation units to fulfill the tightened environmental regulation. The control of the future Smart Grid will be challenging due to increased number of renewable power generation units, which are variable in nature, and at the same time, the customers are highly dependent on uninterruptable, high quality power supply. The Smart Grid control is intensively studied. It can be concluded that the control might be simpler and the grid operation more reliable if the AC grid would be replaced by DC grid. However, the detailed energy efficiency analysis of the DC grid is not thoroughly studied. The efficiency and total lifetime costs are the key parameters when the network owners consider the future grid structure.This thesis addresses the factors, which affect the energy efficiency of the low voltage DC (LVDC) distribution network from power electronics perspective. The power loss models for the converters and their AC filters are developed and verified by measurements. The impact on the converter topology, used power semiconductor switches, AC filter design and inductor core material, DC network configuration, customer behavior, the need of DC voltage balancing in the bipolar DC network as well as the grounding issues to fulfill the electrical safety standards are treated. For facilitating the design of cost effective LVDC distribution networks, the total power losses of the network with different configurations are evaluated and compared.It is revealed that the used filter inductor core material has a significant impact on the power losses of the LVDC distribution network. The inductor core material having low high-frequency power loss characteristics, such as amorphous alloy, is recommended. The LVDC distribution network should be grounded to minimize the power losses whenever it is possible according to the local safety standardization and grounding conditions. The three-level NPC converters connected to 1500 VDC should be used to minimize the power losses. The grid-frequency isolation transformer is the main power loss source if the galvanic isolation is needed to isolate the ungrounded LVDC distribution network and the grounded customer electrical installations. In this case, the highest energy efficiency is achieved by using two- or three-level converters connected to 750 VDC if the DC cable length is less than 600 m. Otherwise, slightly higher energy efficiency is achieved by using three-level converters connected to 1500 VDC. Therefore, voltage transformation ratio of the isolation transformer must be 800V/400V instead of 400V/400V. Moreover, the efficiency of the power converters is increased by using SiC MOSFETs instead of conventional IGBTs as power semiconductor switches

Turun kaupungin perhevalmennusmateriaalin uudistaminen : synnytys ja lapsivuodeaika

Opinnäytetyö oli osa Turun sosiaali- ja terveystoimen, Turun ammattikorkeakoulun sekä yhteistyökumppaneiden välistä Neuvolatoiminta 2010-luvulle-hanketta. Hankkeen tarkoituksena oli perhevalmennuksen sisällön nykyaikaistaminen sekä uuden yhtenäisen materiaalin tuottaminen äitiysneuvoloiden terveydenhoitajien käyttöön. Opinnäytetyön tutkimustehtävät muodostettiin maaliskuussa 2010 pidetyn kokouksen pohjalta, joka järjestettiin yhdessä kolmen Turun äitiysneuvolan terveydenhoitajan sekä Vava-projektin suunnittelijan ja opinnäytetyön ohjaajan kanssa. Opinnäytetyön aiheeksi valittiin Tuomisen (2009,123) kehittämästä uudesta perhevalmennusmallista toinen perhevalmennuskerta, joka sisälsi teemat synnytys ja lapsivuodeaika. Opinnäytetyön tarkoituksena oli selvittää Turun kaupungin äitiysneuvoloiden olemassa olevan perhevalmennusmateriaalin kehittämistarpeita synnytykseen ja lapsivuodeaikaan liittyvien teemojen osalta. Tämä tapahtui analysoimalla Turun kaupungin perhevalmennuskansion sisältöä sekä kartoittamalla aiheeseen liittyvää tutkimustietoa kirjallisuuskatsauksen muodossa. Näiden pohjalta uudistettiin toisen perhevalmennuskerran valmennusmateriaalia uuden mallin mukaisesti. Perhevalmennuksen ideana oli saada vanhemmat luottamaan omiin voimavaroihinsa. Päämääränä oli synnytyksen ja lapsivuodeajan luonnollisuuden korostaminen. Synnytysteemaan tarkoituksena oli tarpeita vastaavan ja ajanmukaisen tiedon antaminen synnytyksen kulusta ja hoitokäytännöistä, jotta vanhemmat voisivat valmistautua synnytykseen turvallisin mielin. Lapsivuodeajan teeman tavoitteena oli antaa vanhempien tarpeita vastaavaa ja ajankohtaista tietoa lapsivuodeajasta sekä valmentaa synnytyksen jälkeiseen aikaan. Kasvaneiden tarpeiden ja odotusten myötä perhevalmennuksen kehittämistarve on ilmeinen, sillä perhevalmennus on tärkeä osa vanhemmuuteen kasvussa. Kirjallisuuskatsauksen pohjalta nousseet tulokset vahvistivat oletusta siitä, että vanhemmat kaipaavat perhevalmennukselta täsmällisempää ja yksilöllisempää tietoa.This bachelor´s thesis was based on the results from Miia Tuominen’s Valmiina Vanhemmuu-teen (VaVa) (2009) research. VaVa´s idea was to bring family training up to this date. Upgrading maternity and child health care clinics was started from Maternity and Child Health Care Clinics to 21.century -project (Kymppi -hanke). Research problems were based on a meeting that was held in March 2010. The meeting was held together with three nurses from Turku Maternity and Child Health Care Clinics, the leader of VaVa-project and the instructor of this thesis. Tuominen (2009, 123) has greated a new family training model of witch the second family training session includes themes childbirth and pu-erperium. The second family training session became the subject of this thesis. The meaning of thesis was to discover what kind of family training material needed to be up-graded for childbirth and puerperium themes. This was done by analyzing the family training material of the City of Turku and surveying the research material in a form of literature review. The material of childbirth and puerperium was upgraded by Tuominen’s new model of the second family training session. The idea of family training was to get parents to trust on their own capabilities. The aim was to emphasize the naturalness of childbirth and puerperium. The purpose of the childbirth theme was to give information about ongoing birth so that parents can prepare themselves to that with trust. The aim of the puerperium theme was to offer knowledge about the time after giving birth and to coach for the postpartum period. Family training has become an important part of becoming a parent. The growing needs and expectations from parents have made it clear that there is a need to develop family training. A review of the literature indicated that parents require more exact and individualized information

Implementing of Activating Learning Strategy for a Course on Electric Drives

Effective teaching of electric drives is highly important for the electrical engineers, because almost half of the global produced electrical energy is consumed by electric motor drives. Electric drives are a key technology for reducing energy consumption of industrial processes, for wind power generation and for electric transportation. The pedagogical premise is to improve the educational methods of an Electrical Drives course by activating students to work on their own. The paper describes the educational strategy and course objectives. Student feedback was collected at the end of the course and the results of the evaluation are summarized.publishedVersionPeer reviewe

The Impact of LED Lighting Systems to the Power Quality and Recommendations for Installation Methods to Achieve the Expected Energy Efficiency

The experimental study of the lighting system influence on the power quality has been performed. The effect of the fluorescent tube lights (FTL) with magnetic and electronic ballasts as well as the LED lights from four companies are compared. It is very usual to replace only the FTL tube to LED tube without removing the additional capacitors. According to the presented results, the expected increase in energy efficiency and power quality is not achieved. The produced reactive power is significant with the defective replacement practice. The issue is accelerated with the continuous reduction of inductive loads and the increase of the capacitive reactive power production. When replacing old FTLs with LEDs, the protection and the start-up transient must to be considered. The protection device may require update, for example slower circuit breaker. If no updates for the supply side are made, there may be a need to reduce the amount of lights when FTLs are replaced with LEDs. According to the measurements, LEDs are remarkable factor in the change of capacitive reactive power production. In the future, there should be more detailed instructions and requirements for the lighting system renovation. For example, the installation instructions should include the removal of the capacitors. However, electromagnetic compatibility of the modified lighting equipment cannot be ensured straightforwardly. The best practice for lighting update is to change the whole luminaire. At the moment, this is the only way to ensure the designed operation.publishedVersionPeer reviewe