Position sensorless electrically excited synchronous motor drive for industrial use based on direct flux linkage and torque control

Synchronous machines with an AC converter are used mainly in large drives, for example in ship propulsion drives as well as in rolling mill drives in steel industry. These motors are used because of their high efficiency, high overload capacity and good performance in the field weakening area. Present day drives for electrically excited synchronous motors are equipped with position sensors. Most drives for electrically excited synchronous motors will be equipped with position sensors also in future. This kind of drives with good dynamics are mainly used in metal industry. Drives without a position sensor can be used e.g. in ship propulsion and in large pump and blower drives. Nowadays, these drives are equipped with a position sensor, too. The tendency is to avoid a position sensor if possible, since a sensor reduces the reliability of the drive and increases costs (latter is not very significant for large drives). A new control technique for a synchronous motor drive is a combination of the Direct Flux Linkage Control (DFLC) based on a voltage model and a supervising method (e.g. current model). This combination is called Direct Torque Control method (DTC). In the case of the position sensorless drive, the DTC can be implemented by using other supervising methods that keep the stator flux linkage origin centered. In this thesis, a method for the observation of the drift of the real stator flux linkage in the DTC drive is introduced. It is also shown how this method can be used as a supervising method that keeps the stator flux linkage origin centered in the case of the DTC. In the position sensorless case, a synchronous motor can be started up with the DTC control, when a method for the determination of the initial rotor position presented in this thesis is used. The load characteristics of such a drive are not very good at low rotational speeds. Furthermore, continuous operation at a zero speed and at a low rotational speed is not possible, which is partly due to the problems related to the flux linkage estimate. For operation in a low speed area, a stator current control method based on the DFLC modulator (DMCQ is presented. With the DMCC, it is possible to start up and operate a synchronous motor at a zero speed and at low rotational speeds in general. The DMCC is necessary in situations where high torque (e.g. nominal torque) is required at the starting moment, or if the motor runs several seconds at a zero speed or at a low speed range (up to 2 Hz). The behaviour of the described methods is shown with test results. The test results are presented for the direct flux linkage and torque controlled test drive system with a 14.5 kVA, four pole salient pole synchronous motor with a damper winding and electric excitation. The static accuracy of the drive is verified by measuring the torque in a static load operation, and the dynamics of the drive is proven in load transient tests. The performance of the drive concept presented in this work is sufficient e.g. for ship propulsion and for large pump drives. Furthermore, the developed methods are almost independent of the machine parameters.

Marjatta

Soitinnus: lauluääni, piano.

The Importance of Semantics: Visual World Studies on Drawing Inferences and Resolving Anaphors

The present thesis investigated the importance of semantics in generating inferences during discourse processing. Three aspects of semantics, gender stereotypes, implicit causality information and proto-role properties, were used to investigate whether semantics is activated elaboratively during discourse comprehension and what its relative importance is in backward inferencing compared to discourse/structural cues. Visual world eye-tracking studies revealed that semantics plays an important role in both backward and forward inferencing: Gender stereotypes and implicit causality information is activated elaboratively during online discourse comprehension. Moreover, gender stereotypes, implicit causality and proto-role properties of verbs are all used in backward inferencing. Importantly, the studies demonstrated that semantic cues are weighed against discourse/structural cues. When the structural cues consist of a combination of cues that have been independently shown to be important in backward inferencing, semantic effects may be masked, whereas when the structural cues consist of a combination of fewer prominent cues, semantics can have an earlier effect than structural factors in pronoun resolution. In addition, the type of inference matters, too: During anaphoric inferencing semantics has a prominent role, while discourse/structural salience attains more prominence during non-anaphoric inferencing. Finally, semantics exhibits a strong role in inviting new inferences to revise earlier made inferences even in the case the additional inference is not needed to establish coherence in discourse. The findings are generally in line with the Mental Model approaches. Two extended model versions are presented that incorporate the current findings into the earlier literature. These models allow both forward and backward inferencing to occur at any given moment during the course of processing; they also allow semantic and discourse/structural cues to contribute to both of these processes. However, while the Mental Model 1 does not assume interactions between semantic and discourse/structural factors in forward inferencing, the Mental Model 2 does assume such a link.

Historia Regiae Academiae Aboensis

Invocatio: I.N.J.C.

Metsäsääntely Suomessa ja Venäjällä. Näkökulmia kestävään metsätalouteen

Sustainability is the aim of forest management and forest regulation in many countries. Accordingly, forest management has been steered towards more environmentally friendly methods and new regulatory instruments have been introduced. At the same time, wood trade and forest industry have become a global business. Even if the importance of national forest legislation has not decreased, it has been widely acknowledged that national regulation of forest management is no longer sufficient. The movement of goods does not acknowledge boundaries, even though most negative environmental and social consequences stay in the country of origin of wood and other raw materials. As a partial solution to this dilemma, different kinds of regulations have been developed. Various forest certification schemes and wood trade regulation in the EU (995/2010) are examples of efforts to prevent illegal logging and unsustainable forestry. The Finland-based forest industry is to a varying extent dependent on wood trade from Russia. Especially in the 1990‟s, ethical questions concerning import of wood from Russian old growth forests near the Finnish border were widely discussed. Consequently, forest industry enterprises have developed systems to trace the origin of wood and to buy certified wood from Russia. The aim of the research has been to evaluate Finnish and Russian forest regulations in order to investigate what kind of forest management these regulations enhance, and to what extent ecologically sustainable forest management has been integrated into different forms of regulation. I have examined Finnish and Russian forest regulation in four separate articles based on the topics of the Russian Forest Code, forest certification and other voluntary forest protection measures in Russia, Finnish forest certification and Finnish forest legislation. One objective has been to analyse the roles voluntary forest certification plays in promoting sustainable forest management in different countries. In my research, I have mainly concentrated on ecological sustainability and protection of biodiversity, although other aspects of sustainable forest management have been touched upon in different articles. In the following I shall conclude the findings of my research. When the current Russian Forest Code (2006) was being adopted, the main emphasis was not on ecological issues, but on reorganizing forest governance. The role of ecological requirements was even slightly diminished during the legislative reform. There are, nevertheless, still stipulations aiming at ecological sustainability, such as the division of forests into different forest management categories and various protection zones. In 2000, FSC forest certification arrived in Russia, at present covering already 28 million hectares of forests. The PEFC scheme is now in use as well, but to a much lesser extent. If properly implemented, Russian forest certification schemes clearly improve the level of ecological and social sustainability of forestry in Russia. Certification criteria, however, are partly in conflict with the Russian forest legislation and certified enterprises have been forced to pay fines or to negotiate with forest authorities. This clearly indicates that even if Russian forest legislation has otherwise been liberalized to a certain extent, some significant paternalism still exists. Voluntary, hands-on biodiversity protection measures are not valued, and they are not part of the official protection policies as in many other countries. However, there have been some regional solutions to this dilemma. In the Republic of Karelia forest authorities have approved a set of forest biodiversity protection rules created by a local NGO and a forest industry enterprise. By following these local rules, an enterprise can avoid fines for protection measures. The current Finnish Forest Act was adopted in 1996. It brought forest legislation into a new era as some ecological aspects were integrated into forest legislation. The various soft-law forest management recommendations further increased the level of biodiversity protection. My evaluation of the overall legitimacy of the Finnish forest legislation and forest management paradigm revealed, however, several problematic issues. As part of this study I analysed the history of the current forest management paradigm. This analysis revealed the path dependency which still hinders the protection of biodiversity and clearly decreases the general legitimacy of forest management. Due to several historical reasons only even-structured forest management based on clear cuts has for decades been officially approved in Finland. Due to increasing demands of forest owners the legislation is finally being revised. Yet, the official approval of uneven-structured forest management would not be enough to fully improve ecological, social and cultural legitimacy. The latest ecological theories and knowledge of endangered species should be taken into account in the on-going reform of forest legislation as well as the modernisation. Forest legislation is one of the very few spheres of Finnish environmental legislation where openness and participation are still considered a threat. The first Finnish forest certification scheme, PEFC, was established in 2000. It now covers more than 20 million hectares, about 95% of the forests in Finland. PEFC Finland does not require a higher level of biodiversity protection than the recommendations by Tapio (the Development Centre for Forestry), but certification has unified forest management practices and requires more protection measures than mere forest legislation. The study suggests that in Finland PEFC has not functioned as an instrument which would substantially improve the level of forest management. Rather it has supported the status quo of the forest sector. While the ecological and social responsibility of Finland-based forest corporations was one impetus for this research, I want to conclude that there are problems related to forest legislation and non-state regulation in both Finland and Russia. If an enterprise buying wood from Russia buys only certified wood, and carefully avoids wood coming from high conservation value forests that are either ecologically or socially valuable, it can be claimed to be as sustainably produced as in Finland. However, there must be continuous scrutiny of the circumstances. In Russia, the level of the compliance of certification criteria varies considerably, and there are vast unprotected invaluable forest areas. The utilisation of these areas should not be based on short-sighted decisions or lack of consensus among stakeholders.

Pohjois-Karjalan maakunnan ilmanlaadun bioindikaattoriseuranta vuonna 2010

Ilmanlaatua on seurattu Pohjois-Karjalan alueen kunnissa 1980-luvulta lähtien käyttäen ilmentäjinä havupuita ja niiden rungoilla kasvavia jäkäliä. Vuonna 1998 seuranta toteutettiin ensimmäisen kerran koko maakunnan laajuisena. Vuonna 2010 ilmanlaatua arvioitiin männyn epifyyttijäkälien esiintymisen ja kunnon sekä sammalten ja neulasten alkuainepitoisuuksien perusteella koko Pohjois-Karjalan maakunnan alueella. Tutkimusalueen päästömäärät ovat laskeneet selvästi 1980- ja 1990-luvuilta 2000-luvulle tultaessa, mutta 2000-luvulla etenkin rikkidioksidien ja hiukkasten päästökehitys on ollut aaltomaista. Myös liikenteen rikkidioksidin, typen oksidien ja hiukkasten päästöt ovat vähentyneet selvästi tarkasteluajanjaksolla. Ilmasta mitattujen epäpuhtauksien pitoisuudet ovat pääasiassa laskeneet 2000-luvulle tultaessa verrattuna 1980- ja 1990-lukuihin. Tutkimusalueen suurimmat päästölähteet sijaitsevat Joensuussa, Lieksassa ja Kiteellä. Ilman epäpuhtauksien vaikutukset ilmanlaatua kuvaaviin jäkälämuuttujiin olivat koko Pohjois-Karjalan maakunnan mittakaavassa lieviä ja erityisesti taustaalueilla vaikutukset olivat hyvin vähäisiä. Päästölähteiden ympäristössä vaikutukset olivat selvempiä, mutta laajuudeltaan melko pieniä. Terveintä sormipaisukarvetta tutkimusalueella kasvoi Kesälahdella, paikoin Kiteellä, Joensuun kaupungin alueella Tuupovaarassa ja Kiihtelysvaarassa, Ilomantsissa sekä Valtimon ja Nurmeksen pohjoisosissa. Vaurioituneinta sormipaisukarve oli Joensuun keskustaajamasta Hammaslahteen ulottuvalla vyöhykkeellä, Juuan kunnan keskiosassa ja Nurmeksen keskustaajamasta Valtimon kunnan eteläosaan ulottuvalla vyöhykkeellä. Tutkimusalueen pohjoisosissa jäkälälajisto oli laajalti luonnontilaista ja etelä- ja keskiosassa lievästi köyhtynyttä. Monipuolisin ja luonnontilaisin jäkäläyhteisö tutkimusalueella oli Kesälahden, Kontiolahden ja Valtimon kuntien alueella ja köyhtynein puolestaan Joensuun, Kiteen ja Rääkkylän alueella. Korkeimmat sammalten alkuainepitoisuudet tutkimusalueella määritettiin päästölähteiden läheisyydestä. Tilastollisten analyysien perusteella tutkimusalueelta löydettiin merkittävimmät raskasmetallien ja muiden alkuaineiden päästölähteet, joita olivat lämpölaitokset sekä kaivokset ja kaivostuotteiden jatkojalostuslaitokset. Tulosten perusteella sammalten raskasmetallipitoisuudet Pohjois-Karjalassa edustavat suhteellisen puhtaan tausta-alueen pitoisuuksia. Kuusen harsuuntuminen oli Pohjois-Karjalassa tilastollisesti merkitsevästi vähäisempää kuin muualla maan eteläosissa. Männyn harsuuntuminen ei poikennut muun Etelä-Suomen arvoista. Erilaiset tuhot ja puiden ikä selittävät suuren osan havupuiden harsuuntumisen vaihtelusta. Neulasten rikkipitoisuuksissa ei ollut tapahtunut merkittävää muutosta tutkimusalueen merkittävimpien päästölähteiden läheisyydessä vuoden 1998 tutkimukseen verrattuna, kun otetaan huomioon neulashavaintoalojen toisistaan poikkeava sijoittelu eri tutkimusvuosina. Verrattuna vuonna 1998 toteutettuun tutkimukseen, sormipaisukarpeen vauriot olivat hieman kasvaneet, levä yleistynyt ja ilman epäpuhtauksille herkät lajit harvinaistuneet tutkimusalueella, mutta kokonaisuudessaan muutokset vuosien välillä olivat lieviä. Vaurioituneimman sormipaisukarpeen ja köyhtyneimmän lajiston vyöhykkeet sijoittuivat pääosin samoille alueille molempina tutkimusvuosina eli Joensuun-Hammaslahden väliselle alueelle, Uimaharjuun, Kiteelle ja Nurmeksen ja Lieksan keskusta-alueille, mutta vuonna 2010 köyhtyneimmän lajiston vyöhykkeet olivat hieman laajempia. Päästömäärien lievä kasvu 2000-luvun loppuvuosina on todennäköisesti vaikuttanut jäkäliin ja vaikutus näkyi vielä tässä tutkimuksessa, vaikka päästömäärät ovatkin 2000-luvulla olleet pienempiä kuin 1990-luvulla. Hajapäästöjä aiheuttavan toiminnan (esim. kaivostoiminta, turvetuotanto ja maatalous) lisääntyminen tutkimusalueella voi myös osittain selittää tutkimusvuosien välisiä lieviä muutoksia jäkälälajistossa ja jäkälien kunnossa tausta-alueilla.

Modeling and Control of the Power Conversion Unit in a Solid Oxide Fuel Cell Environment

In this doctoral thesis, a power conversion unit for a 10 kWsolid oxide fuel cell is modeled, and a suitable control system is designed. The need for research was identified based on an observation that there was no information available about the characteristics of the solid oxide fuel cell from the perspective of power electronics and the control system, and suitable control methods had not previously been studied in the literature. In addition, because of the digital implementation of the control system, the inherent characteristics of the digital system had to be taken into account in the characteristics of the solid oxide fuel cell (SOFC). The characteristics of the solid oxide fuel cell as well the methods for the modeling and control of the DC/DC converter and the grid converter are studied by a literature survey. Based on the survey, the characteristics of the SOFC as an electrical power source are identified, and a solution to the interfacing of the SOFC in distributed generation is proposed. A mathematical model of the power conversion unit is provided, and the control design for the DC/DC converter and the grid converter is made based on the proposed interfacing solution. The limit cycling phenomenon is identified as a source of low-frequency current ripple, which is found to be insignificant when connected to a grid-tied converter. A method to mitigate a second harmonic originating from the grid interface is proposed, and practical considerations of the operation with the solid oxide fuel cell plant are presented. At the theoretical level, the thesis discusses and summarizes the methods to successfully derive a model for a DC/DC converter, a grid converter, and a power conversion unit. The results of this doctoral thesis can also be used in other applications, and the models and methods can be adopted to similar applications such as photovoltaic systems. When comparing the results with the objectives of the doctoral thesis, we may conclude that the objectives set for the work are met. In this doctoral thesis, theoretical and practical guidelines are presented for the successful control design to connect a SOFC-based distributed generation plant to the utility grid.

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Mettälän, Elimäen kirkonkylän ja Napan pohjavesialueiden suojelusuunnitelma : Kouvola

Mettälän, Elimäen kirkonkylän ja Napan pohjavesialueiden suojelusuunnitelma on tehty osana vuosina 2012–2014 toteutettua kymPOVERI (Kymenlaakson pohjavesiriskit hallintaan) -hanketta. Hankkeessa laadittiin pohjavesialueiden suojelusuunnitelmat 32:lle Kymenlaakson vedenhankinnan kannalta tärkeälle pohjavesialueelle. Pohjavesialueiden suojelusuunnitelmaan on koottu tietoa pohjavesialueiden hydrogeologisista olosuhteista käyttäen hyväksi vanhoja alueella tehtyjä tutkimuksia sekä hankkeen yhteydessä suoritettujen maastokartoitusten ja -tutkimusten tuloksia. Suojelusuunnitelmaan on koottu tietoa alueilla sijaitsevista pohjavedelle riskiä aiheuttavista toiminnoista, kuten teollisuus- ja yritystoiminnoista, liikenteen ja tienpidon riskeistä, pilaantuneista maa-alueista, maa-ainestenotosta, maa- ja metsätaloudesta, asutuksesta, jätevesistä, öljy- ja polttoainesäiliöistä, maalämmöstä ja muuntamoista. Suojelusuunnitelmassa on annettu toimenpidesuosituksia sekä yksittäisille riskikohteille että eri riskiryhmille yleisesti. Suojelusuunnitelmassa käsitellään kaavoitustilanne alueilla ja annetaan ohjeita maankäytön suunnitteluun pohjavesialueilla. Lisäksi suunnitelmaan on kirjattu toimintaohjeet mahdollisissa vahinko- ja onnettomuustapauksissa.