Diskreettiaikainen liukuvan moodin säätö kiinteäoksidipolttokennon DC-tasonnostossa

Huoli ympäristön tilasta ja fossiilisten polttoaineiden hinnan nousu ovat vauhdittaneet tutkimusta uusien energialähteiden löytämiseksi. Polttokennot ovat yksi lupaavimmista tekniikoista etenkin hajautetun energiantuotannon, varavoimalaitosten sekä liikennevälineiden alueella. Polttokenno on tehonlähteenä kuitenkin hyvin epäideaalinen, ja se asettaa tehoelektroniikalle lukuisia erityisvaatimuksia. Polttokennon kytkeminen sähköverkkoon on tavallisesti toteutettu käyttämällä galvaanisesti erottavaa DC/DC hakkuria sekä vaihtosuuntaajaa sarjassa. Polttokennon kulumisen estämiseksi tehoelektroniikalta vaaditaan tarkkaa polttokennon lähtövirran hallintaa. Perinteisesti virran hallinta on toteutettu säätämällä hakkurin tulovirtaa PI (Proportional and Integral) tai PID (Proportional, Integral and Derivative) -säätimellä. Hakkurin epälineaarisuudesta johtuen tällainen ratkaisu ei välttämättä toimi kaukana linearisointipisteestä. Lisäksi perinteiset säätimet ovat herkkiä mallinnusvirheille. Tässä diplomityössä on esitetty polttokennon jännitettä nostavan hakkurin tilayhtälökeskiarvoistusmenetelmään perustuva malli, sekä malliin perustuva diskreettiaikainen integroiva liukuvan moodin säätö. Esitetty säätö on luonteeltaan epälineaarinen ja se soveltuu epälineaaristen ja heikosti tunnettujen järjestelmien säätämiseen.

[Five mystical songs]

Soitinnus: lauluääni (mezzosopraano), piano.

Hankintatoimen järjestäminen julkisella sektorilla ja yhteishankintayksikön motiivit ja haasteet – case: KL-Kuntahankinnat Oy

Tämän tutkielman tavoitteena on selvittää, miten hankintatoimi on järjestetty Suomen julkisella sektorilla ja erityisesti mitä motiiveja ja haasteita liittyy case-yrityksen toimintaan. Teoriaosan kirjallisuus-katsauksen avulla tarkastellaan hankintatoimen järjestämistä julkisella sektorilla ja tutkimus painottuu erityisesti kuntasektoriin, sillä suurin osa julkisista hankinnoista tehdään juuri kuntasektorilla. Tavoitteena on lisäksi löytää sopivia viitekehyksiä liittyen lisäarvon tuottamiseen ja arvontuotto-logiikkaan sisäisille asiakkaille yhteishankintayksikön toiminnassa. Empiirisen osan materiaali on koottu haastattelujen perusteella. Tavoitteena on hyödyntää löydettyjä malleja case-yrityksen toiminnan tarkastelussa ja mahdollisesti sen kehittämisessä. Nykyisillä rakenteilla ja toimintamalleilla kunnat eivät selviä niille osoitetuista tehtävistä, sillä kunta-alalla perusongelma on edelleen se, että menot kasvavat nopeammin kuin tulot. Tämä vaatii uusia toimintatapoja ja rakenteita. Yhteishankintayhtiö KL-Kuntahankinnat Oy:n tarjoama ydinpalvelu on tuoda tarjoamansa hankintapalvelun avulla selkeää lisäarvoa kunta-asiakkailleen. Yritys hyödyntää keskitettyä hankintamallia ja toiminnan sen motiivit liittyvät asiantuntijuuteen, asiakkaille tuotettaviin kustannus- ja prosessisäästöihin, erikoistumisella saavutettaviin etuihin ja toiminnan tehokkuuden kasvuun sekä asiakkaiden omaan oppimiseen.

World Heritage of the Kvarken Archipelago : Echoes of the Ice Age

The Kvarken Archipelago is Finland’s first Unesco Natural Heritage Site. The story of the Kvarken Archipelago began about 10.000 years ago when the melting of the continental ice sheet as it retreated gave rise to this unique archipelago. The land once forced down by the mass of ice is now gradually rising and continuously creating new landscapes. People, animals and plants have learnt to adjust to their changing conditions in exceptional ways. The Ice Age may be over in Kvarken, but the drama still continues to unfold.

Kun ajanhenki vie

Kirjallisuusarvostelu

The Design and Implementation of a Power Management Feature to a Configuration Management System

Green IT is a term that covers various tasks and concepts that are related to reducing the environmental impact of IT. At enterprise level, Green IT has significant potential to generate sustainable cost savings: the total amount of devices is growing and electricity prices are rising. The lifecycle of a computer can be made more environmentally sustainable using Green IT, e.g. by using energy efficient components and by implementing device power management. The challenge using power management at enterprise level is how to measure and follow-up the impact of power management policies? During the thesis a power management feature was developed to a configuration management system. The feature can be used to automatically power down and power on PCs using a pre-defined schedule and to estimate the total power usage of devices. Measurements indicate that using the feature the device power consumption can be monitored quite precisely and the power consumption can be reduced, which generates electricity cost savings and reduces the environmental impact of IT.

Advanced welding technologies used for arctic metal structures

Rapid depletion of easy-to-access fossil fuel, predominantly, oil and gas resources has now necessitated increase in need to develop new oil and gas sources in ever more remote and hostile environments. This is necessary in order to explore more oil and gas resources to meet rapidly rising long-term energy demand in the world, both at present and in the nearest future. Arctic is one of these harsh environments, where enormous oil and gas resources are available, containing about 20% of the world total oil and gas, but the environmental conditions are very harsh and hostile. However, virtually all the facilities required for the exploration and development of this new energy source are constructed with metals as well as their alloys and are predominantly joined together by welding processes and technologies. Meanwhile, due to entirely different environment from the usual moderate temperate region, conventional welding technologies, common metals and their alloys cannot be applied as this Arctic environment demand metals structures with very high toughness and strength properties under extremely low temperature. This is due to the fact that metals transit from ductility to brittleness as the temperature moves toward extreme negative values. Hence, this research work investigates and presents the advanced welding technologies applicable to Arctic metal structures which can give satisfactory weldments under active Arctic service conditions. .

Strategic alliances as an international entry strategy: Finnish cleantech SMEs and the Indian market

The demand for environmental technologies, also called cleantech, is growing globally but the need is especially high in emerging markets such as India where the rising economy and rapid industrialisation have led to increasing energy needs and environmental degradation. The market is of great potential also for the Finnish cleantech cluster that represents advanced expertise in several fields of environmental technologies. However, most of the Finnish companies in the field are SMEs that face challenges in their internationalisation due to their limited resources. The objective of this study was to estimate, whether strategic alliances could be an efficient entry strategy for Finnish cleantech SMEs entering the Indian market. This was done by studying what are the key factors influencing the international entry mode decision of Finnish cleantech SMEs, what are the major factors affecting the entry of Finnish cleantech SMEs to the Indian market and how do Finnish cleantech SMEs use strategic alliances in their internationalisation process. The study was realised as a qualitative multi-case study through theme interviews of Finnish cleantech SME representatives. The results indicated that Finnish cleantech SMEs prefer to enter international markets through non-equity and collaborative modes of entry. These entry modes are chosen because of the small size and limited resources of companies, but also because they want to protect their innovative technologies from property rights violations. India is an attracting market for Finnish cleantech SMEs mainly because of its size and growth, but insufficient environmental regulation and high import tariffs have hindered entry to the market. Finnish cleantech SMEs commonly use strategic alliances in their internationalisation process but the use is rather one-sided. Most of the formed strategic alliances are low-commitment, international contractual agreement in sales and distribution. Alliance partner selection receives less attention. In the future, providing Finnish cleantech SMEs with international experience and training could help in diversifying the use of strategic alliances and increase their benefits to SME internationalisation.

Element speciation and behaviour in metal-rich Boreal river and estuarine systems using ultrafiltration and chemical modelling

The bioavailability of metals and their potential for environmental pollution depends not simply on total concentrations, but is to a great extent determined by their chemical form. Consequently, knowledge of aqueous metal species is essential in investigating potential metal toxicity and mobility. The overall aim of this thesis is, thus, to determine the species of major and trace elements and the size distribution among the different forms (e.g. ions, molecules and mineral particles) in selected metal-enriched Boreal river and estuarine systems by utilising filtration techniques and geochemical modelling. On the basis of the spatial physicochemical patterns found, the fractionation and complexation processes of elements (mainly related to input of humic matter and pH-change) were examined. Dissolved (<1 kDa), colloidal (1 kDa-0.45 μm) and particulate (>0.45 μm) size fractions of sulfate, organic carbon (OC) and 44 metals/metalloids were investigated in the extremely acidic Vörå River system and its estuary in W Finland, and in four river systems in SW Finland (Sirppujoki, Laajoki, Mynäjoki and Paimionjoki), largely affected by soil erosion and acid sulfate (AS) soils. In addition, geochemical modelling was used to predict the formation of free ions and complexes in these investigated waters. One of the most important findings of this study is that the very large amounts of metals known to be released from AS soils (including Al, Ca, Cd, Co, Cu, Mg, Mn, Na, Ni, Si, U and the lanthanoids) occur and can prevail mainly in toxic forms throughout acidic river systems; as free ions and/or sulfate-complexes. This has serious effects on the biota and especially dissolved Al is expected to have acute effects on fish and other organisms, but also other potentially toxic dissolved elements (e.g. Cd, Cu, Mn and Ni) can have fatal effects on the biota in these environments. In upstream areas that are generally relatively forested (higher pH and contents of OC) fewer bioavailable elements (including Al, Cu, Ni and U) may be found due to complexation with the more abundantly occurring colloidal OC. In the rivers in SW Finland total metal concentrations were relatively high, but most of the elements occurred largely in a colloidal or particulate form and even elements expected to be very soluble (Ca, K, Mg, Na and Sr) occurred to a large extent in colloidal form. According to geochemical modelling, these patterns may only to a limited extent be explained by in-stream metal complexation/adsorption. Instead there were strong indications that the high metal concentrations and dominant solid fractions were largely caused by erosion of metal bearing phyllosilicates. A strong influence of AS soils, known to exist in the catchment, could be clearly distinguished in the Sirppujoki River as it had very high concentrations of a metal sequence typical of AS soils in a dissolved form (Ba, Br, Ca, Cd, Co, K, Mg, Mn, Na, Ni, Rb and Sr). In the Paimionjoki River, metal concentrations (including Ba, Cs, Fe, Hf, Pb, Rb, Si, Th, Ti, Tl and V; not typical of AS soils in the area) were high, but it was found that the main cause of this was erosion of metal bearing phyllosilicates and thus these metals occurred dominantly in less toxic colloidal and particulate fractions. In the two nearby rivers (Laajoki and Mynäjoki) there was influence of AS soils, but it was largely masked by eroded phyllosilicates. Consequently, rivers draining clay plains sensitive to erosion, like those in SW Finland, have generally high background metal concentrations due to erosion. Thus, relying on only semi-dissolved (<0.45 μm) concentrations obtained in routine monitoring, or geochemical modelling based on such data, can lead to a great overestimation of the water toxicity in this environment. The potentially toxic elements that are of concern in AS soil areas will ultimately be precipitated in the recipient estuary or sea, where the acidic metalrich river water will gradually be diluted/neutralised with brackish seawater. Along such a rising pH gradient Al, Cu and U will precipitate first together with organic matter closest to the river mouth. Manganese is relatively persistent in solution and, thus, precipitates further down the estuary as Mn oxides together with elements such as Ba, Cd, Co, Cu and Ni. Iron oxides, on the contrary, are not important scavengers of metals in the estuary, they are predicted to be associated only with As and PO4.

Toimintamallin luominen halutun ympäristöluokitustason saavuttamiseksi uudisrakennusprojektissa

Tämän diplomityön tavoitteena on selvittää miksi uudisrakennushankkeeseen ryhtyvän kannattaa huomioida kestävän rakentamisen vaatimukset ja miten asetettuja kestävän ra-kentamisen tavoitteita voidaan hallita rakennusprojektin aikana. Perinteisesti rakennussektorilla on keskitytty tilaajan tavoitteiden saavuttamiseen kustan-nustehokkaasti ja aikataulussa. Kestävän kehityksen ja vastuullisuuden näkökulmat ovat kuitenkin vahvistuneet viime aikoina. Kestävän rakentamisen hallinta vaatii vielä uusia toimintatapoja ja -malleja, jotta voidaan varmistaa kestävän kehityksen kriteerien mukai-suus läpi hankkeen ja valmiissa rakennuksessa. Ympäristöluokitusjärjestelmien avulla voidaan asettaa kestävän rakentamisen tavoitteita, joita seurataan läpi hankkeen. Diplomityössä selvitetään yksityiskohtaisemmin BREEAM (BRE Environmental Assessment Method)-ympäristöluokitusjärjestelmän käyttämistä kestävän rakentamisen ohjaamisessa. Työssä selvitetään myös miten rakennusten tietomallinnusta voidaan käyttää tukemaan kestävän rakentamisen uudisrakennushanketta. Työ toteutetaan kirjalli-suustutkimuksen, asiantuntijahaastatteluiden ja ympäristöluokitusta hakeneesta esimerkki-kohteesta saatujen tietojen avulla. Diplomityön tuloksena muodostettiin toimintamalli varmistamaan halutun kestävän kehi-tyksen tason saavuttaminen uudisrakennusprojektissa. Toimintamallissa on jaettu vastuut ja tehtävät eri osapuolille koko projektin ajalle tarveselvityksestä käytönaikaan.

Feasibility studies of the weldability of structural steels used in the offshore environment

The rising demand for oil and gas has made it very necessary for the oil and gas industries to explore the offshore. There is a huge resources which is available in the offshore. The search for oil and gas is faced with greater challenges because of the nature of the marine environment as it poses difficult and harsh conditions for the construction of offshore structures. The major problem of the construction of offshore structure is the ability to produce a sound weld that gives the whole structure the structural integrity needed to withstand the harsh environmental conditions. This research work presents the performance of typical offshore steels with improved weldability. The ability of reducing the carbon content of thermo-mechanically rolled steels down to 0.08% makes it possible to achieve good weldability, toughness and strength for high strength steels used in offshore applications. Importantly, the ideal welding procedure should be strictly followed as recommended. The fabrication process is as important as the welding procedure in achieving a sound weld which is free of weld defects such as hydrogen induced cracking, lamellar tearing and solidification cracking. This research work also considers the corrosion as it affects offshore structure and necessary measures to mitigate the problem caused by corrosion.

Yrittäjyyskasvatuksen arvoja etsimässä. Design-tutkimus opettajankoulutuksen opetussuunnitelmien kehittämisessä

This research is a survey on values related to entrepreneurship education and a participatory action research on entrepreneurship education curricula in teacher education. Research problems, rising from the practical development work, were solved by several methods, following the principles of design-based research. Values related to entrepreneurship education were studied among teachers, headmasters, teacher educators, researchers and officers in the field of entrepreneurship education in 16 European Union countries. Fifteen most important values related to entrepreneurship education were listed based on two qualitative surveys (N 124 and N 66). Values were also surveyed among Finnish teacher trainees (N 71). Results of the surveys show that the values given by the teacher trainees did not differ much from the ones given by the professionals already working in the field. Subsequently, emergence of these values was studied in documents that steer education. The values gathered in the surveys did not occur in the documents to a substantial degree. Development of entrepreneurship education curricula in teacher education was conducted by means of participatory action research. The development project gathered 55 teacher trainers from 15 teacher education organisations in Finland. The starting point of the phenomenon based project (see Annala and Mäkinen 2011) was the activity plan created for developing entrepreneurship education curricula. During the project, the learning of the teacher educators proceeded in a balanced way as brightening visions, stronger motivation, increasing understanding and new practices, following Shulman and Shulman’s model (2004). Goals of the development project were set to each teacher educator acquiring basic knowledge on entrepreneurship education, organization of obligatory courses on entrepreneurship education, and making entrepreneurship education a cross-curricular theme in teacher education. The process increased the understanding and motivation of teacher educators to develop and teach entrepreneurship education. It also facilitated collaboration as well as creating visions on entrepreneurship education. Based on the results, the concept of enterprisingness was defined, and recommendations were given for developing curricula in entrepreneurship education.

Soraääniä, sitaatteja ja suunnitelmallisuutta. Moniäänisyys Eira Stenbergin romaanituotannossa

Tutkin väitöskirjassani Eira Stenbergin (s. 1943) romaanituotannon moniäänisyyttä, joka liittyy niin subjektiin, kertomisen prosessiin kuin todellisuuskäsityksiin. Aineistonani ovat Stenbergin 1980–1990-luvulla kirjoittamat, tutkimusongelmani kannalta keskeiseen ajanjaksoon kuuluvat romaanit Paratiisin vangit (1984), Häikäisy (1987), Kuun puutarhat (1990) sekä Gulliverin tytär (1993). 1980-luvulla postmodernista tuli kirjallisen kulttuurin keskeisimpiä aiheita Suomessa, ja subjektista tuli ongelma jopa siinä määrin että puhuttiin sen kuolemasta. Ääni oli 1980-luvulla osa subjektia koskevaa keskustelua: yhtäältä nousevan feministisen liikkeen identiteettipoliittisena ja emansipatorisena metaforana, toisaalta jälkistrukturalismin antihumanismin uhkakuvana, joka koski subjektin ääntä alkuperän lähteenä ja persoonan ilmaisuna. Äänen käsitteen voidaan katsoa implikoivan jonkinlaista käsitystä subjektista, ja tarkastelenkin tutkimuksessani erityisesti henkilöhahmoja, kertojia ja kertomisen prosessia, mutta myös tekijän suunnitelmallisuutta ja kuulijaa kohti orientoitumista. Yhdistelen tutkimuksessani retorista kertomuksen teoriaa dekonstruktioon sekä feministisiin subjektiteorioihin. Myös Mihail Bahtinin käsitys moniäänisestä romaanista on työssäni keskeinen. Problematisoin tutkimuksessani äänen kytköksen sisimmän ilmaisuun, omistamiseen ja auktoriteettiin ja ymmärrän sen keskustelualueena, jossa kohtaavat erilaiset arvot ja näkemykset maailmasta. Tällöin kaikenkattava puhe subjektin kuolemasta sekä käsitykset 1980-luvun kirjallisuudesta maailmasta vieraantuneena ja yksityisen alueelle vetäytyvänä problematisoituvat. Stenbergin tuotannon perusteella voi sanoa, että kirjallisuuden äänet saavat merkityksensä vasta erilaisina äänensävyinä konkreettisissa ja ainutkertaisissa konteksteissa. Tämä viittaa tarpeeseen ymmärtää kirjallisuusteoreettisessa keskustelussa usein historiattomana ja universaalina nähty käsite historiaan paikantuneena: eivät vain erityiset aineistot, vaan myös erityiset kontekstit määrittelevät äänen saamia merkityksiä.

Towards sustainable Iron- and steelmaking with economic optimization

The iron and steelmaking industry is among the major contributors to the anthropogenic emissions of carbon dioxide in the world. The rising levels of CO2 in the atmosphere and the global concern about the greenhouse effect and climate change have brought about considerable investigations on how to reduce the energy intensity and CO2 emissions of this industrial sector. In this thesis the problem is tackled by mathematical modeling and optimization using three different approaches. The possibility to use biomass in the integrated steel plant, particularly as an auxiliary reductant in the blast furnace, is investigated. By pre-processing the biomass its heating value and carbon content can be increased at the same time as the oxygen content is decreased. As the compression strength of the preprocessed biomass is lower than that of coke, it is not suitable for replacing a major part of the coke in the blast furnace burden. Therefore the biomass is assumed to be injected at the tuyere level of the blast furnace. Carbon capture and storage is, nowadays, mostly associated with power plants but it can also be used to reduce the CO2 emissions of an integrated steel plant. In the case of a blast furnace, the effect of CCS can be further increased by recycling the carbon dioxide stripped top gas back into the process. However, this affects the economy of the integrated steel plant, as the amount of top gases available, e.g., for power and heat production is decreased. High quality raw materials are a prerequisite for smooth blast furnace operation. High quality coal is especially needed to produce coke with sufficient properties to ensure proper gas permeability and smooth burden descent. Lower quality coals as well as natural gas, which some countries have in great volumes, can be utilized with various direct and smelting reduction processes. The DRI produced with a direct reduction process can be utilized as a feed material for blast furnace, basic oxygen furnace or electric arc furnace. The liquid hot metal from a smelting reduction process can in turn be used in basic oxygen furnace or electric arc furnace. The unit sizes and investment costs of an alternative ironmaking process are also lower than those of a blast furnace. In this study, the economy of an integrated steel plant is investigated by simulation and optimization. The studied system consists of linearly described unit processes from coke plant to steel making units, with a more detailed thermodynamical model of the blast furnace. The results from the blast furnace operation with biomass injection revealed the importance of proper pre-processing of the raw biomass as the composition of the biomass as well as the heating value and the yield are all affected by the pyrolysis temperature. As for recycling of CO2 stripped blast furnace top gas, substantial reductions in the emission rates are achieved if the stripped CO2 can be stored. However, the optimal recycling degree together with other operation conditions is heavily dependent on the cost structure of CO2 emissions and stripping/storage. The economical feasibility related to the use of DRI in the blast furnace depends on the price ratio between the DRI pellets and the BF pellets. The high amount of energy needed in the rotary hearth furnace to reduce the iron ore leads to increased CO2 emissions.

Power semiconductor nonlinearities in active du/dt output filtering

This doctoral thesis introduces an improved control principle for active du/dt output filtering in variable-speed AC drives, together with performance comparisons with previous filtering methods. The effects of power semiconductor nonlinearities on the output filtering performance are investigated. The nonlinearities include the timing deviation and the voltage pulse waveform distortion in the variable-speed AC drive output bridge. Active du/dt output filtering (ADUDT) is a method to mitigate motor overvoltages in variable-speed AC drives with long motor cables. It is a quite recent addition to the du/dt reduction methods available. This thesis improves on the existing control method for the filter, and concentrates on the lowvoltage (below 1 kV AC) two-level voltage-source inverter implementation of the method. The ADUDT uses narrow voltage pulses having a duration in the order of a microsecond from an IGBT (insulated gate bipolar transistor) inverter to control the output voltage of a tuned LC filter circuit. The filter output voltage has thus increased slope transition times at the rising and falling edges, with an opportunity of no overshoot. The effect of the longer slope transition times is a reduction in the du/dt of the voltage fed to the motor cable. Lower du/dt values result in a reduction in the overvoltage effects on the motor terminals. Compared with traditional output filtering methods to accomplish this task, the active du/dt filtering provides lower inductance values and a smaller physical size of the filter itself. The filter circuit weight can also be reduced. However, the power semiconductor nonlinearities skew the filter control pulse pattern, resulting in control deviation. This deviation introduces unwanted overshoot and resonance in the filter. The controlmethod proposed in this thesis is able to directly compensate for the dead time-induced zero-current clamping (ZCC) effect in the pulse pattern. It gives more flexibility to the pattern structure, which could help in the timing deviation compensation design. Previous studies have shown that when a motor load current flows in the filter circuit and the inverter, the phase leg blanking times distort the voltage pulse sequence fed to the filter input. These blanking times are caused by excessively large dead time values between the IGBT control pulses. Moreover, the various switching timing distortions, present in realworld electronics when operating with a microsecond timescale, bring additional skew to the control. Left uncompensated, this results in distortion of the filter input voltage and a filter self-induced overvoltage in the form of an overshoot. This overshoot adds to the voltage appearing at the motor terminals, thus increasing the transient voltage amplitude at the motor. This doctoral thesis investigates the magnitude of such timing deviation effects. If the motor load current is left uncompensated in the control, the filter output voltage can overshoot up to double the input voltage amplitude. IGBT nonlinearities were observed to cause a smaller overshoot, in the order of 30%. This thesis introduces an improved ADUDT control method that is able to compensate for phase leg blanking times, giving flexibility to the pulse pattern structure and dead times. The control method is still sensitive to timing deviations, and their effect is investigated. A simple approach of using a fixed delay compensation value was tried in the test setup measurements. The ADUDT method with the new control algorithm was found to work in an actual motor drive application. Judging by the simulation results, with the delay compensation, the method should ultimately enable an output voltage performance and a du/dt reduction that are free from residual overshoot effects. The proposed control algorithm is not strictly required for successful ADUDT operation: It is possible to precalculate the pulse patterns by iteration and then for instance store them into a look-up table inside the control electronics. Rather, the newly developed control method is a mathematical tool for solving the ADUDT control pulses. It does not contain the timing deviation compensation (from the logic-level command to the phase leg output voltage), and as such is not able to remove the timing deviation effects that cause error and overshoot in the filter. When the timing deviation compensation has to be tuned-in in the control pattern, the precalculated iteration method could prove simpler and equally good (or even better) compared with the mathematical solution with a separate timing compensation module. One of the key findings in this thesis is the conclusion that the correctness of the pulse pattern structure, in the sense of ZCC and predicted pulse timings, cannot be separated from the timing deviations. The usefulness of the correctly calculated pattern is reduced by the voltage edge timing errors. The doctoral thesis provides an introductory background chapter on variable-speed AC drives and the problem of motor overvoltages and takes a look at traditional solutions for overvoltage mitigation. Previous results related to the active du/dt filtering are discussed. The basic operation principle and design of the filter have been studied previously. The effect of load current in the filter and the basic idea of compensation have been presented in the past. However, there was no direct way of including the dead time in the control (except for solving the pulse pattern manually by iteration), and the magnitude of nonlinearity effects had not been investigated. The enhanced control principle with the dead time handling capability and a case study of the test setup timing deviations are the main contributions of this doctoral thesis. The simulation and experimental setup results show that the proposed control method can be used in an actual drive. Loss measurements and a comparison of active du/dt output filtering with traditional output filtering methods are also presented in the work. Two different ADUDT filter designs are included, with ferrite core and air core inductors. Other filters included in the tests were a passive du/dtfilter and a passive sine filter. The loss measurements incorporated a silicon carbide diode-equipped IGBT module, and the results show lower losses with these new device technologies. The new control principle was measured in a 43 A load current motor drive system and was able to bring the filter output peak voltage from 980 V (the previous control principle) down to 680 V in a 540 V average DC link voltage variable-speed drive. A 200 m motor cable was used, and the filter losses for the active du/dt methods were 111W–126 W versus 184 W for the passive du/dt. In terms of inverter and filter losses, the active du/dt filtering method had a 1.82-fold increase in losses compared with an all-passive traditional du/dt output filter. The filter mass with the active du/dt method was 17% (2.4 kg, air-core inductors) compared with 14 kg of the passive du/dt method filter. Silicon carbide freewheeling diodes were found to reduce the inverter losses in the active du/dt filtering by 18% compared with the same IGBT module with silicon diodes. For a 200 m cable length, the average peak voltage at the motor terminals was 1050 V with no filter, 960 V for the all-passive du/dt filter, and 700 V for the active du/dt filtering applying the new control principle.