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A study of the degradation of ferroelectric properties in Lead Zirconate Titanate (PZT) thin film capacitors is presented in this work. Metal- Ferroelectric - Metal capacitors were prepared by sputtering and metal organic decomposition (MOD) techniques. Samples with several different film thicknesses were considered in this study. Depolarization, leading to imprint has been studied at various temperatures. Changes in the dielectric properties of the capacitors as a function of the number of fatigue cycles is presented. Impedance and modulus spectroscopic techniques have been applied to study the effect of degradation on the ferroelectric thin film. It has been shown that with accurate low frequency impedance measurement equipment, new insight can be gained on the mechanisms of degradation in ferroelectric capacitors. / Master of Science

Various types of current mode control are being used in different applications. Model for current mode control is indispensable for proper system design. Since 1980s, modeling of current mode control has been a hot topic in power electronics field. In current mode control, sub-harmonic oscillation is a common issue, especially for constant frequency current mode control: like peak current mode control, valley current mode control, or average current mode control. Recently V2 control is becoming more and more popular due to its simple implementation ad super fast transient response. V2 control can also run into sub-harmonic oscillation just as current mode control. Efforts have been devoted to modeling of V2 control. A common property of different types of current mode control and V2 control is that they are all multi-loop structures and the inner loops are all highly nonlinear. Due to the nonlinearity of the inner loops, modeling of these structures is extremely difficult. Up to now, there are two main problems which haven't been solved: 1. modeling of average current mode control; 2. modeling of V2 control with composite capacitors. This thesis tries to solve these two problems and starts with V2 control. For V2 control with single type of bulk capacitors, an accurate model has been proposed previously. In this thesis, an equivalent circuit model is proposed to get better physical understanding. This method makes use of previous current mode control modeling result and relates V2 control with current mode control. To model V2 control with composite capacitors, capacitor currents and output voltage time domain waveforms are analyzed. Based on describing function method, transfer function from control to output is derived. The modeling result shows that with more parallel ceramic capacitors, system has smaller stability margin. For average current mode control, the structure is compared with V2 control. Similarity between the structures of current compensator in average current mode and output capacitor network in V2 control is identified. V2 model is utilized for average current mode control. The modeling derivation process is simplified. For the current compensator in average current mode control, it is not desired to have a high frequency pole from stability point of view. As a conclusion, a circuit model for V2 control with bulk capacitors is proposed and another two problems are examined: modeling of V2 control with composite capacitors and modeling of average current mode control. It has been demonstrated that there is similarity between these two structures. The modeling results are verified through simulation and experiments. / Master of Science

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Bakgrunden till detta projekt är att Vattenfall Eldistribution AB (nedan kallat Vattenfall) kommer att införa ett avgiftssystem för inmatning av reaktiv effekt till sitt elnät. Avgiften införs till följd av problem på elnätet som orsakas av reaktiv effekt. Umeå Energi Elnät AB (nedan kallat Umeå Energi) har historiskt matat in reaktiv effekt vilket motiverade detta arbete som utreder den reaktiva effekten på Umeå Energis elnät samt bidrar med information om två alternativa tillvägagångssätt att bemöta avgiften. Alternativ 0 är att kompensationsutrustning inte installeras, utan att ett abonnemang på inmatning av reaktiv effekt upprättas. Alternativ 1 är att kompensationsutrustning installeras. För att utreda den reaktiva effekten erhölls och behandlades data på reaktiv effekt i Umeå Energis nät. Historisk kondensatordrift togs fram för år 2016 ur händelsehistoriken hos Umeå Energis driftcentral. Kondensatordriften år 2015 kunde enbart erhållas från ett tidigare arbete på Umeå Energi eftersom ett begränsat antal händelser lagras i händelsehistoriken. Genom att subtrahera kondensatorernas produktion från den reaktiva effekten i Umeå Energis anslutningspunkter som uppmätts av Vattenfall erhölls data som mer representerade underliggande fenomen på nätet. Utan kondensatordrift beräknades inmatningen enligt Vattenfalls definition uppgå till cirka 34 MVAr utifrån data från 2015 och 2016. För åren 2018 till och med 2023 beräknades ändringar i reaktiv effekt till följd av förändringar på Umeå Energis nät. Vid beräkningarna försummades ledningarnas induktiva karaktär, vilket gav ett tomgångsscenario med maximal produktion av reaktiv effekt. År 2023 beräknades inmatningen ska ha ökat till 59 MVAr till följd av förändringar på Umeå Energis nät. Med antagandet att Umeå Energi inte kommer att drifta kondensatorbatterierna så att inmatningen höjs föreslogs för alternativ 0 val av abonnemang på inmatning av reaktiv effekt för åren 2018 till och med 2023 utifrån de 34 MVAr som nämnts ovan och inverkan från förändringarna på nätet. År 2019 föreslogs ett abonnemang på 41 MVAr, och 2023 föreslogs ett på 59 MVAr. Kostnaderna för dessa beräknades enligt Vattenfalls tariff till 820 000 kr respektive 1 187 000 kr. Kostnaden för eventuell överinmatning av reaktiv effekt beräknades med tariffen för överinmatning årligen uppgå till maximalt 76 000 kr med 95 % sannolikhet enligt den korrigerade standardavvikelsen hos inmatningen utan kondensatordrift åren 2015 och 2016. Optimal kondensatordrift beräknades för åren 2015 och 2016 genom att addera den produktion av reaktiv effekt från befintliga kondensatorbatterier som gav minst absolutvärde i reaktiv effekt. Beroende på hur ofta kondensatordriften justerades erhölls olika resultat. En undersökning av störningar till följd av kondensatorkopplingar rekommenderas för att få en förståelse för förutsättningarna för optimal kondensatordrift. Det bedömdes inte ekonomiskt motiverbart med mer avancerad kompensationsteknik såsom statiska VAr-kompensatorer då variabla reaktorer kan kompensera dygns- och säsongsvariationer i reaktiv effekt. Den reaktiva effektproduktionen i ledningar är störst på 145 kV-nivån och kommer öka i framtiden på denna nivå. Det är därför sannolikt här kompensationsutrustning såsom reaktorer först bör installeras. För att kunna ta så bra beslut som möjligt angående den reaktiva effekten rekommenderas att snarast möjligt ingå ett arbetssätt som om avgiftssystemet redan tagits i bruk och utöka ett representativt dataunderlag. / The background of this project is that Vattenfall Eldistribution AB (hereinafter referred to as Vattenfall) will establish a system of fees for input of reactive power. This will be done due to problems in the grid caused by reactive power. Umeå Energi Elnät AB (hereinafter referred to as Umeå Energi) has historically input reactive power, motivating this work which investigates the reactive power in the grid of Umeå Energi and provides information on two alternative approaches to responding to the fee. Alternative 0 entails no installation of compensation technology, and that a subscription for reactive power input is established instead. Alternative 1 entails that compensation technology is installed. To investigate the reactive power, data on reactive power in the grid of Umeå Energi were obtained and processed. Historical operations of capacitor banks for the year 2016 were obtained from the history of events of the control center at Umeå Energi. The operations of the capacitor banks during 2015 could only be obtained from an earlier work at Umeå Energi since the number of events stored in the history is limited. By subtracting the capacitor banks’ production from the reactive power measured by Vattenfall in the connections of Umeå Energi, data more representative of underlying phenomena were obtained. Without capacitor production of reactive power, the input was calculated according to the definition of Vattenfall to about 34 MVAr, by using data from 2015 and 2016. For the years 2018 through 2023, changes in reactive power due to changes in the grid of Umeå Energi were calculated. These calculations did not consider inductances, and thus yielded zero-load scenarios with maximum reactive power production. By the year of 2023, the input was calculated to have increased to 59 MVAr due to changes in the grid of Umeå Energi. Assuming that Umeå Energi will not operate the capacitors so that the input is increased, for alternative 0 subscriptions for input of reactive power were suggested for the years 2018 through 2023 by considering the abovementioned 34 MVAr and the changes in the grid. Subscriptions of 41 MVAr and 59 MVAr were suggested for the years 2019 and 2023 respectively. The costs of these were calculated with the fee specified by Vattenfall to SEK 820,000 and SEK 1,187,000 respectively. Calculations with the applicable fee yielded that the yearly cost of possible over-input could amount to a maximum of SEK 76,000 with a 95 % probability, using the corrected standard deviation of the input without capacitor production of reactive power for the years 2015 and 2016. Optimal capacitor bank operations were calculated for the years 2015 and 2016 by adding the production of reactive power from existing capacitor banks which yielded the minimum absolute reactive power. Depending on how often the capacitors were operated different results were obtained. An investigation of power quality disturbances due to capacitor bank operations is recommended to achieve an understanding of the conditions for optimal capacitor bank operations. It was not deemed economically justifiable to install more advanced compensation technologies such as static VAr compensators since variable reactors are able to compensate daily and seasonal variations in reactive power. The production of reactive power in cables is the largest on the 145 kV level and will increase in the future on this level. It is therefore likely here compensation technologies such as reactors should be installed first. To be able to make as good decisions as possible concerning the reactive power, it is recommended to as soon as possible commence a working method as if the fee system had already come into effect; thus increasing the amount of representative data.

Electrochemical capacitors or supercapacitors or ultracapacitors are potential energy storage devices that could help bringing major advances in future energy storage applications. Unlike batteries that store energy in chemical reactants capable of generating charge, electrochemical capacitors store energy directly through charge separation. Most electrochemical capacitors rely on carbon-based structures utilizing electrical double-layer capacitance effect. By contrast, a pseudocapacitor relies on charge stored due to fast faradaic charge-transfer processes with surface atoms. A combination of faradaic and non-faradaic components would generate hybrid electrochemical capacitors or hybrid ultracapacitors that attain high capacitance for pulse power and sustained energy. This thesis comprises studies pertaining to design, development and applications R&D on substrate-integrated lead-carbon hybrid ultracapacitors. The thesis comprises ten chapters. Chapter 1 is a brief introduction on essentials of electrochemical capacitors explaining their operating principles, classification and applications. Chapter 2 describes studies on materials for electrical double-layer capacitors. Activated carbons are the most common materials for electrical double-layer capacitors. Various activated carbon samples are screened as suitable materials for electrical double-layer capacitor followed by their optimization under varying experimental conditions to form the negative plate in the substrate-integrated lead-carbon hybrid ultracapacitor. Chapter 3 deals with the studies on design and development of 2 V substrate-integrated lead-carbon hybrid ultracapacitors with flooded, absorbent-glass-mat and silica-gel sulfuric acid electrolyte configurations. Lead-carbon hybrid ultracapacitors comprise substrate-integrated lead dioxide sheets as positive plates and high surface-area-carbon-coated graphite-sheets as negative plates. Operating principle for 2 V lead-carbon hybrid ultracapacitors is explained and optimization of their operating conditions along with their electrochemical performance is studied. Chapter 4 is a study on the integration of 2 V substrate-integrated lead-carbon hybrid ultracapacitors to 12 V devices. 12 V substrate-integrated lead-carbon hybrid ultracapacitors with flooded, absorbent-glass-mat and silica gel sulfuric acid electrolyte are developed by connecting six 2 V cells in series. These hybrid ultracapacitors exhibit high power-density values and excellent cycle-life. The problem of uneven performance among the six 2 V cells in the 12 V hybrid ultracapacitors is addressed and resolved by applying voltage-management cell-balancing circuitry. Chapter 5 details the studies on kilo-Farad range 12 V substrate-integrated lead-carbon hybrid ultracapacitors. The hybrid ultracapacitors are performance tested through a standard protocol. Thermal runaway in these hybrid ultracapacitors at high load currents is studied by thermal imaging. Studies on performance comparison between 12 V lead-carbon hybrid ultracapacitors with substrate-integrated and conventional pasted-positive plates are presented in Chapter 6. For substrate-integrated-positive plate lead-carbon hybrid ultracapacitors, capacitance and energy-density values are lower but power-density values are higher than pasted-positive plate configuration due to their shorter response-time. Accordingly, internal resistance values are lower for substrate-integrated lead-carbon hybrid ultracapacitors. Both types of lead-carbon hybrid ultracapacitors exhibit similar faradaic efficiency and cycle-life in excess of 100,000 pulse charge/discharge cycles with only a nominal loss in their capacitance values. Chapter 7 is a study on the design and development of low-cost substrate-integrated lead-carbon hybrid ultracapacitors using poly-aniline organic metal. The hybrid ultracapacitor employs flexible exfoliated graphite sheets as negative plate current-collectors, which are coated with a thin layer of poly-aniline to provide good adhesivity to activated carbon layer and good substrate-conductivity. These ultracapacitors are estimated to cost about 4 US$/Wh as compared to 20-30 US$/Wh for presently available commercial ultracapacitors. In Chapter 8, an application R&D study on the suitability of a substrate-integrated lead-carbon hybrid ultracapacitor bank in powering medical gadgets is described. A practical application that provides 30 W power back-up to medical gadgets for use in grid-power-deficient rural areas is presented. Chapter 9 is another application R&D study in realizing a photovoltaic stand-alone lighting system using substrate-integrated lead-carbon hybrid ultracapacitors. At present, harnessing solar electricity generated through photovoltaic cells with lead-acid batteries remains the most compelling option. But lead-acid batteries have encountered problems in photovoltaic installations, mainly due to their premature failure. To circumvent this problem, substrate-integrated lead-carbon hybrid ultracapacitors are developed for solar energy storage for a lighting application. The last Chapter of the thesis comprises field studies on substrate-integrated lead-carbon hybrid ultracapacitors. In the study, hybrid ultracapacitors are installed for lighting applications for field tests. Grid-power chargers and mechanical dynamos are introduced as fast-charging tools for hybrid ultracapacitors. It is hoped that the studies presented in this thesis would constitute a worthwhile contribution to science and technology of electrochemical capacitors. Considering the technology need, availability, safety and cost, substrate-integrated lead-carbon hybrid ultracapacitors are set to play a seminal role in future energy storage and management.

Esta pesquisa tem como principal objetivo apresentar uma análise do comportamento dos elementos passivos mais utilizados para compensação reativa e na composição dos filtros passivos sintonizados: os capacitores de potência. Tal análise foi focada na comparação de resultados obtidos via simulação computacional com os resultados oriundos de ensaios laboratoriais em ambiente controlado, servindo de base para estabelecer os limites de validade do modelo computacional hoje implementado em softwares comerciais de simulação de fluxo de carga e fluxo de harmônicos de uso bastante difundido no ambiente industrial. Os resultados alcançados demonstram que o modelo clássico de capacitores apresenta uma excelente precisão quando operando em condições ideais. Porém, quando operando na presença de situações adversas às ideais, o modelo demonstrou possuir limitações que serão devidamente reportadas neste documento. / This research has as aim to present a behaviors analysis of the electrical power capacitors which are used for reactive compensation and in the tuned harmonic passive filters. Such analysis was focused on the results comparison obtained via computer simulation with the results obtained in laboratory tests done in a controlled environment, providing the basis to establish the validity limits of the computational model implemented in today\'s commercial load flow and harmonic flow software simulation widespread use in industrial environments. Results show that the classical model capacitor has excellent accuracy when operating under ideal conditions. However, when operating in presence of adverse situations the classical model has demonstrated limitations that will be duly and reported in this work.

Foram estudados filmes de oxinitreto de silício obtidos por PECVD à 320°C, a partir da mistura gasosa de N2O+SiH4+He, com diferentes valores de pressão e potência de deposição com o objetivo de produzir boa qualidade de interface deste material com o Si e de obter uma baixa densidade de carga efetiva visando a aplicação desses filmes em dispositivos semicondutores MOS. Os resultados mostraram que com uma pressão de deposição de 0,160 mbar e potências menores que 125 W/cm2 é possível obter um valor de densidade de estados de interface (Dit) de 4x1010 eV-1.cm-2, campo elétrico de ruptura (Ebd) de 13 MV/cm, valores comparáveis ao SiO2 térmico e uma densidade de carga efetiva (Nss) de 4x1011 cm-2. Segundo resultados experimentais esse valor de Nss é o mínimo possível que se pode atingir com a limpeza química utilizada em nosso laboratório. Pode-se dizer que estes são resultados bastante interessantes considerando que se trata de um material obtido por PECVD à baixa temperatura, porém viável para aplicação em dispositivos MOS. Iniciando os estudos com dielétricos de maiores valores de constante dielétrica optamos por estudar filmes de TiOx (k=40-100), obtidos por sputtering reativo, a partir da mistura gasosa de Ar+O2 e utilizando alvo de Ti. Foram fabricados capacitores MOS com estes filmes e obteve-se valores de constante dielétrica que variaram de 40-160. Porém esses materiais ainda apresentavam valores apreciáveis de corrente de fuga que foram minimizadas em ordens de grandeza quando utilizados dielétricos de dupla camada com SiO2 ou SiOxNy (otimizado neste trabalho) na interface, além de se observar uma melhora significativa da qualidade de interface. Utilizando dupla camada dielétrica com filmes de SiOxNy e SiO2, ainda espessos (³ 1nm) para camada intermediária, obteve-se uma constante dielétrica efetiva em torno de 20. Vale ressaltar que os dois filmes SiOxNy e TiOx, conseqüentemente a dupla camada, foram fabricados a baixas temperaturas. / Silicon oxynitride films obtained by the PECVD technique from N2O+SiH4+He gaseous mixtures, at 320°C, with different deposition pressure and RF power were studied intending to improve the interface quality with Si, decreasing the effective charge density and the interface state density in order to utilize them in MOS semiconductor devices. The results showed that with a deposition pressure of 0.160 mbar and a RF power density lower than 125 W/cm2 it is possible to obtain interface state density (Dit) values of 4x1010 eV-1.cm-2, Electrical Breakdown (Ebd) of 13 MV/cm, comparable with the obtained for thermally grown SiO2 , and an effective charge density (Nss) of 4x1011 cm-2. According with experimental results this Nss value is the minimum attainable with our chemical cleaning process. In this way it can be said that these results are very promising, considering that these materials were obtained by PECVD at low temperatures, but still viable for MOS devices application. In order to initiate studies with high dielectrics constant material, TiOx films (k= 40-180), obtained by reactive sputtering through the Ar+O2 gaseous mixture utilizing a Ti target, were chosen. MOS capacitors with these films were fabricated and dielectric constant values varying from 40 to 160 were obtained. However, until now, these materials have presented appreciable leakage current values, which were, minimize by orders of magnitude with the addition of a thin SiO2 or SiOxNy (optimized in this work) layer at the interface were utilized. This thin layer also resulted in a significant improvement of the interface quality. Utilizing double dielectric layer with SiOxNy or SiO2, still thick (³ 1nm) as intermediate layer a dielectric constant value of 20 was obtained. Its important to mention that the SiOxNy and TiOx films, and consequently the double layer, were deposited at low temperatures.