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Photovoltaics panel (PV) integration with the utility grid has been installed throughout the globe. The fault-monitoring technology for photovoltaics (PV) panels is a method to save energy production losses and become a key contributor to overall cost reduction in variable operating costs for photovoltaics systems. PV researchers today explore factors such as reducing utility energy bills and CO2 emissions, grid voltage stability, peak demand shaving, supply of electric power off-grid areas, and many more. The technology discussed is easy to incorporate, requires no additional hardware, doesn't alter the system’s stability, is implemented at a steady state point, and is helpful to record changes in PV cell operation from forward bias to reverse bias state. PV panel AC impedance can be used as an early-stage fault indicator. Also, comparing AC impedance magnitude and phase at maximum power point (MPP) or near MPP can help identify the nature of the fault in a PV system. The focus of the thesis is proposing the fault detection of 300 W PV panels using online AC impedance measurement, utilizing existing panel-level power optimizers and microinverters in a PV system to actively perturb small signals into the PV panel and compute its small signal impedance. The technology is incorporated in a power optimizer with C2000 MCU and helps identify hot spot faults and short circuit faults in a 300 W rooftop PV panel. Multiple PV panel faults scenarios such as hot spot faults, short circuit faults, junction box faults, and capacitor faults are investigated to deduct further the effectiveness of the online impedance measurement using a small signal. This thesis’s focus areas are, first, modeling the PV panel and power converter and incorporating fault scenarios to identify the fault indicators. Secondly, measuring PV panel impedance under normal and faulty conditions using an equipment-based offline technique. Lastly, measuring PV panel impedance under normal and faulty conditions using a power optimizer. / M.S. / A Photovoltaics panel is a series and parallel combination of many photovoltaics cells to generate electricity from sunlight via a photoelectric process. The fault-monitoring technology for photovoltaics (PV) panels is a method to save energy production losses and become a key contributor to overall cost reduction in variable operating costs for photovoltaics systems. The PV panel, over a period of time, can degrade with fluctuations in temperature and weather. Photovoltaics panel (PV) integration with the utility grid has been installed throughout the globe. PV researchers today explore factors such as reducing utility energy bills and CO2 emissions, grid voltage stability, peak demand shaving, supply of electric power off-grid areas, and many more. The technology discussed is easy to incorporate, requires no additional hardware, doesn't alter the system’s stability, is implemented at a steady state point, and is helpful to record changes in PV cell operation from forward bias to reverse bias state. A PV panel operating at maximum power point (MPP) generates direct current (DC) and maintains a stable voltage across the PV panel load. A small signal injection in PV panel current or voltage is an addition of a sinusoidal signal with an amplitude of 10 % to the operating point of PV panel voltage or current and frequency sweep between 10 Hz to 200 kHz. The PV panel's AC impedance is measured under small signal injection and can be used as an early-stage fault indicator. Also, comparing AC impedance magnitude and phase at maximum power point (MPP) or near MPP can help identify the nature of the fault in a PV system. The focus of the thesis is proposing the fault detection of PV panels using online AC impedance measurement and utilizing existing panel-level power optimizers and microinverters in a PV system to actively perturb small signals into the PV panel and compute its small signal impedance. The technology is incorporated in a power optimizer with C2000 MCU and helps identify hot spot faults and short circuit faults in a 300 W rooftop PV panel. This thesis’s focus areas are, modeling the PV panel and power converter and incorporating fault scenarios to identify the fault indicators. Multiple PV panel faults scenarios such as hot spot fault, short circuit fault, junction box fault, and capacitor fault are investigated to further deduct the effectiveness of the online impedance measurement using a small signal. Secondly, measuring PV panel impedance under normal and faulty conditions using an equipment-based offline technique. Lastly, measuring PV panel impedance under normal and faulty conditions using a power optimizer.

Printed electronics is a combination of electronics and printing technologies commonly used in the publication industry such as screen, inkjet, and roll to roll printing. The measurements of conductive film particularly the conductive paste is the main objective of this thesis. The conductive paste consists of conductive filler, adhesive and solvent. Each component affects the electrical, and mechanical properties of the finished conductive film product. The measurements of conductive film have three field of study. The first category is the lifetime performance measurement of conductive film using environmental testing. A screen printed carbon, silver and a developmental paste were categorised to environmental testing and third harmonic measurement. The second category is the measurement AC Impedance and DC resistance of conductive ink during cure. During the curing of the pastes, the AC impedance and DC resistance were monitored. A LabVIEW program was developed to control the AC impedance analyser, DC resistance ohmmeter, and convection oven. Samples were measured whilst curing at different curing temperatures and for a range of particle loadings. Particle loading is the percentage of conductive filler against the rest of the chemical in the conductive paste. The last category was defect detection using the combination of electromechanical testing, a Scanning Electron Microscope (SEM) and an Infrared (IR) imaging technique. Printed carbon and silver were mechanically aged by bending the printed structure up to 100 k times. The results from the lifetime performance measurements on carbon, silver and the developmental paste showed the polymer resin behaviour in high humidity and high temperature environments. The increased oxidation rate due to the elevated temperatures affected the conductive particle of certain pastes. The third harmonic testing technique was able to detect failures on conductive film in the form of width reduction. The AC impedance measurement technique could indicate the final resistivity value. The AC impedance measurement was affected by the test frequency used while the ink is in liquid state. Correct test frequency setting will have less noise and less impedance value, vital in predicting the final cured resistance of the printed paste. The curing temperature affects the final cured resistance value while the particle loading affects the rate of curing of conductive film. The electrical measurement on mechanically aged samples showed that the carbon prints have its resistance readings below its initial value while the silver prints resistance increased. SEM images shows that the carbon print indicates no visual damage on the surface after 100 k bent cycle, while physical defects were observed in silver prints. The infrared measurements on carbon prints showed an increase in temperature while developments of heat patches were observed on silver prints. Difference in emissivity values of materials used provided the contrast effect which plays an important role in detecting defect using infrared imaging technique because. Third harmonic application to the printed electronics is new to this field. Normally, testing is done using environmental testing to determine the lifetime performance of the conductive film. This is effective however requires a lot of time and effort to produce a result. AC Impedance is used widely and the application can be seen on cured printed electronics. The application and measurement of AC impedance during cure and DC resistance measurement has indicated initial resistivity values. The measurement has further the effect of using AC impedance on different curing temperature and particle loading. The phase measurement as well has brought insight of degree of curing. The application of infra-red imaging technique to the mechanically aged device has produced a result that DC resistance and SEM imaging failed to detect. Normally DC resistance measurement was used as quality assessment tool but test shows on mechanically aged product failed to detect increase in resistance due to mechanical aging techqnique.

No description available.

This thesis applies the concept of a virtual-synchronous-machine- (VSM-) based control to a conventional 250-kW utility-scale photovoltaic (PV) inverter. VSM is a recently-developed control scheme which offers an alternative grid-synchronization method to the conventional grid-tracking control scheme, which is based on the dq phase-locked-loop- (PLL-) oriented vector control. Synchronous machines inherently synchronize to the grid and largely partake in the stabilization of the grid frequency during power system dynamics. The purpose of this thesis is primarily to present the design of a grid-forming control scheme based on the VSM and the derivation of the terminal dq-frame ac impedance of the small-signal model of the inverter and control scheme. This design is also compared to the design of the conventional grid-tracking control structure, both from a loop design and terminal dq-frame ac impedance standpoint. Due to the inherent lax power-balance synchronization, the grid-forming control scheme results in 1 to 2 decades' lower frequency range of negative incremental input impedance in the diagonal elements, which is a favorable condition for stability. Additionally, the stability of the grid-forming control scheme is compared to the conventional grid-tracking control using the generalized Nyquist criterion (GNC) for stability under three modes of operation of active and reactive power injection. It is found that the connection is stable for both control schemes under unity power factor and fixed reactive power modes; however, the grid-forming control is able to inject twice the amount of active power under the voltage regulation mode when compared to the grid-tracking control. / Master of Science / Concerns about the current and future state of the environment has prompted government and non-profit agencies to enact regulatory legislation on fossil fuel emissions. In 2017, electricity generation comprised 28% of total U.S. greenhouse gas emissions with 68% of this generation being due to coal combustion sources. As a result, utilities have retired a number of coal power plants and have employed alternative means of power generation, specifically renewable energy sources (RES). Most RES operate as variable-frequency ac sources (wind) or dc sources (solar) and are interfaced with the power grid through ac-dc-ac or dc-ac converters, respectively, which are power-electronic devices used to control the injection of power to the grid. Conventional converters synchronize with the grid by tracking the phase of the voltage at the point of common coupling (PCC) through a phase-locked loop (PLL). While power system dynamics significantly affect the performance of a PLL, and, subsequently, inverters' operation, the initial frequency regulation during grid events is attributed to the system's inherent inertia due to the multitude of synchronous machines (SM). However, with the steady increase of RES penetration, even while retaining the number of SM units, the net inertia in the system will decrease, thus resulting in prolonged responses in frequency regulation to the aforementioned dynamics. This thesis investigates the control of variable-frequency sources as conventional synchronous machines and provides a detailed design procedure of this control structure for photovoltaic (PV) inverter applications. Additionally, the stability of the connection of the inverter to the grid is analyzed using innovative stability analysis techniques which treat the inverter and control as a black box. In this manner, the inner-workings of the inverter need not be known, especially since it is proprietary information of the manufacturer, and the operator can measure the output response of the device to some input signal. In this work, it is found that the connection between the inverter and grid is stable with this new control scheme and comparable to conventional control structures. Additionally, the control based on synchronous machine characteristics shows improved stability for voltage and frequency regulation, which is key to maintaining a stable grid.

This thesis devotes to develop a wafer-level packaging technique of the planar AgCl-based micro reference electrode and to investigate its various electrochemical characteristics (including the potential stability and offset voltage, AC impedance, cyclic-voltammetry analysis, electrochemical noise and reproducibility). The miniaturized all-solid-state reference electrode can integrated with many biomedical or biochemical sensors for substantially reduce the dimension of the whole sensing system and improve the commercial capability of portable detecting products. This study reports firstly a smallest module of the micro reference electrode with dimension only about 9 mm (L) ¡Ñ 6 mm (W) ¡Ñ 1 mm (H) in the worldwide using the silicon bulk-micromachining technology, thin film deposition and chloridation techniques. The packaged reference electrode module is constructed by two bonded wafers with different functions. One wafer of this module is defined as ¡§electrode chip¡¨ and it has a Ti/Pd/Ag/AgCl planar quasi-reference electrode deposited on its surface. Another wafer is called as ¡§packaging chip¡¨ and it has two bulk-micromachined silicon cavities for the filling/sealing of 1.33 ~ 6.40 £gL KCl-gel (as the salt-bridge of electrode) and electrical connection. Many electrochemical characteristics of the encapsulated solid-state micro reference electrode are tested and improved for the commercial applications. Including a very stable cell potential (<4 mV in 30000 sec.), an approximately zero offset-voltage, a low AC impedance (1~20 K£[), and high reproducibility (drift less than 3~8 mV in 30000 sec. and the range of offset voltage is -6 ~ 3 mV) of the packaged micro reference electrode are demonstrated. Furthermore, stable CV curve of the packaged Ti/Pd/Ag/AgCl/KCl-gel reference electrode were proved by cyclic-voltammetry analysis and its low electrochemical noise spectrum was investigated and discussed in this work. Compared with the commercial reference electrode, the planar miniaturized AgCl reference electrode module developed in this thesis has displayed its many excellent characteristics and with a dimension only 250 times smaller than the conventional reference electrode.

The well-known lanthanide cuprates exist in two principal forms, T and T´, which behave as p-type and n-type conductors, respectively. In order to understand the structural properties and crystal chemistry from the T to T´ phase, the Nd₁.₈₋ₓLaₓPr₀.₂CuO₄ (NLPCO) system was studied varying the La substitution ratio (0≤x≤1.8) and then characterised using high temperature X-ray powder diffraction. From analysis of the X-ray diffraction patterns obtained at room temperature, there are clearly five distinguishable regions for the NLPCO system. They are, (1) monophasic T´ solid–solution (2) two phase mixture T´ + T´´ (3) monophasic T´´solid–solution (4) two phase mixture T´´ + O and finally (5) monophasic O phase solid–solution. The T´´ form has previously been suggested as an ordered form of T´; however here we show via high temperature X-ray diffraction studies that it is a non-transformable metastable phase formed on quenching of the T phase via an orthorhombically distorted variant. Also neutron diffraction and selected area electron diffraction (SAED) studies confirmed that the T ´´phase is 4- fold Cu coordinated. The structural, magnetic and electrical properties of this NLPCO series have been investigated for the selected compositions using X-ray diffraction, magnetization measurements, thermal analysis and conductivity measurements. The aim of the second half of this work was to discover the basic high temperature electrical characteristics of Nd₂₋ₓPrₓCuO₄ and investigate how this matches with those required for components on the SOFC cathode side to identify which dopant level shows highest conductivity and whether it is stable at different temperatures. The idea was to make a new concept in SOFC cathodes and current collector development, using n-type conductors instead of p- type conductors and to try to produce a high conductivity material which is stable under the chemical and thermal stresses that exist while under load that can be used in cathode or current collector applications. The Nd₂₋ₓPrₓCuO₄ (NPCO) series has been studied over a range of dopant levels (x=0.15 - 0.25) and maximum conductivity of 86.7 Scm⁻¹ has been obtained for the composition where x = 0.25. Also NPCO shows n-type semiconductor behaviour which gives operational advantages when operating at mild oxygen deficiency. AC impedance studies have been carried out on symmetrical cells to investigate the performance of NPCO as a cathode material. These studies mainly focused on polarization resistance and the activation energies of the cells. Low Rp values and low activation energies are obtained for a composite cathode compared to pure cathode material. Two configurations of NPCO as cathode materials were tested, pre-fired and in-siu fired. Pre-fired NPCO exhibited better performance than in-situ fired NPCO. Both in-situ and pre-fired current collecting NPCO still showed lowest activation energies which suggest good catalytic activity. From all of these studies, it is evident that the praseodymium doped neodymium cuprate material shows considerable promise as a potential cathode material for solid oxide fuel cell applications.

Für den Einsatz in Autobatterien gibt es besondere Anforderungen an den Elektrolyten im Bereich der Energie- und Leistungsdichten, um beispielsweise thermische Verluste gering zu halten. Hochleitfähige Elektrolyte mit Leitfähigkeiten im Millisiemensbereich sind hier ebenso notwendig wie auch sichere, d.h. möglichst nicht brennbare und einen niedrigen Dampfdruck besitzende Materialien. Um diese Vorgaben zu erreichen, ist es notwendig, einen polymeren Separator zu entwickeln, welcher auf brennbare organische Lösungsmittel verzichtet und damit eine drastische Steigerung der Sicherheit gewährleistet. Gleichzeitig müssen hierbei die Leistungsvorgaben bezüglich der Leitfähigkeit erfüllt werden. Zu diesem Zweck wurde ein Konzept basierend auf der Kombination von einer polymeren sauerstoffreichen Matrix und einer ionischen Flüssigkeit entwickelt und verifiziert. Dabei wurden folgende Erkenntnisse gewonnen: 1. Es wurden neuartige diacrylierte sauerstoffreiche Matrixkomponenten mit vielen Carbonylfunktionen, für eine gute Lithiumleitfähigkeit, synthetisiert. 2. Es wurden mehrere neue ionische Flüssigkeiten sowohl auf Imidazolbasis als auch auf Ammoniumbasis synthetisiert und charakterisiert. 3. Die Einflüsse der Kationenstruktur und der Einfluss der Gegenionen im Bezug auf Schmelzpunkte und Leitfähigkeiten wurden untersucht. 4. Aus den entwickelten Materialien wurden Blendsysteme hergestellt und mittels Impedanzspektrometrie untersucht: Leitfähigkeiten von 10-4S/cm bei Raumtemperatur sind realisierbar. 5. Die Blendsysteme wurden auf ihre thermische Stabilität hin untersucht: Stabilitäten bis 250°C sind erreichbar. Dabei wird keine kristalline Struktur beobachtet. / Within the field of energy storage and charge transfer, the lithium polymer batteries are one of the leading technologies, due to their low manufacture cost and their possible variety of packaging shapes. Despite their good thermal stability and very good weight to energy ratio, lithium ion batteries use as a electrolyte system a mixture of ethylene carbonate and diethyl carbonate as solvent which have a high risk of deflagration when they come in contact with water. Thus the developement of new materials for lithium-ion-batteries are necessary. For the electrolyte there are special requirements in terms of energy- and power density e.g. in order to minimize thermal loss. High conductivity electrolytes with conductivities in the range of milisiemens are as essential as safe materials, like non flammable non-volatile materials. To fulfill these requirements it is important to develop a polymeric lithium ion conductor, which is free of flammable organic solvents in order to ensure safety. Simultaneously it is also ,mandatory to achieve high performances in terms of ion-conductivity. Therefore a concept based on a combination of an oxygen rich polymeric matrix and ionic liquids was developed and verified. Following results were achieved . 1. Synthesis of new diacryalted oxygen rich matrix components with many carbonylfunctions for a good lithium ion transport. 2. Synthesis and characterization of new ionic liquids based on imidazol or ammonium compounds. 3. Investigation of the influences of the cation structure and counter ions for melting points and ion conductivity. 4. Creation of Blendsystems with the developed materials 5. Thermal investigations of these solid-state-electrolytes with DSC and TGA measurements, resulting in thermal stabilities up to 250°C.No crystallization were observed. 6. investigation of these solid-state-electrolytes via AC-impedance spectrometry, resulting in conductivities of 10-4S/cm at room temperature.

No description available.

In recent years, the demand for Li-ion-type batteries has been increasing significantly in various fields of applications including portable electronics, electric vehicles, and also in renewable energy support. These applications ask for a highly efficient charging strategy in order to maintain a long life cycle of the batteries. Recently, a new charging technique referred as sinusoidal ripple current-constant voltage charging (SRC-CV) technique has been proposed and is in certain publications claimed to realize an improved charging per-formance on Li-ion batteries than conventional constant-current constant-voltage charg-ing (CC-CV) techniques. In this thesis, the charging performance of the SRC-CV charging method applied to a prismatic Li-ion cell for an automotive traction application is inves-tigated. An existing experimental setup is upgraded to realize charging of the Li-ion cells using the SRC-CV charging method. Electrochemical impedance spectrums of three Li-ion cells have been obtained using electrochemical impedance spectroscopy (EIS). These spectrums were used to determine the charging ripple-current frequency where the mag-nitudes of the ac impedance of the cell are minimized. Key parameters like charging time, discharging time, and energy efficiency are calculated in order to compare the charg-ing performance of the CC-CV and SRC-CV charging techniques. The results reported from the experimental results obtained in this thesis indicate that there is no significant improvement with the SRC-CV charging method (implemented using a constant ripple-current frequency) compared to the CC-CV method in terms of charging time and energy efficiency. / På senare tid har behovet av batterier av Li-jontyp ökat kraftigt inom ett flertal applikationsområden inkluderande portabel elektronik, elfordon och miljövänlig elenergiproduktion. I dessa applikationsområden behövs en högeffektiv laddstrategi för att möjliggöra ett stort antal cyklingar av batterierna. Nyligen har en new laddmetod, benämnd sinusoidal ripple current-constant voltage-laddning (SRC-CV-laddning) föreslagits och har i vissa publikationer demonsterat en förbättring av laddprestanda hos Li-jonbatterier jämfört med konventionell constant-current constant-voltage-laddning (CC-CV-laddning). I detta examensarbete undersöks laddprestandan hos SRC-CV och CC-CV-laddning när de appliceras på prismatiska Li-jonceller avsedda för traktionsdrift. En existerande experimentuppsättning har uppgraderats för att realisera laddcykling med SRC-CV-laddning. Med hjälp av elektrokemisk impedansspektroskopi på tre Li-jonceller har den frekvens vid vilken magnituden på cellernas impedans är minimerad identifierats. Nyckelparametrar såsom laddtid, urladdningstid och energieffektivitet har uppmätts för både SRC-CV- och CC-CV-laddning. De experimentella resultaten visar ingen signifikant förbättring mellan SRC-CV-laddning (implementerat med en konstant rippelströmfrekvens) och konventionell CC-CV-laddning.