Nowadays two main types of protection schemes widely used in protection of transmission lines are: distance protection and differential protection schemes. However, it has been noticed from industrial practice that the distance protection scheme used today generally is limited in tripping speed and selectivity. Also differential protection scheme is influenced by the time synchronization of samples in both relays installed at transmission line terminals. On the other hand, among various pilot protection schemes for protection of Extra High Voltage (EHV) / Ultra High Voltage (UHV) transmission lines, the schemes which use communication link only for exchange of local decision making about faults’ status are not affected by time synchronization. This master thesis is dealing with the issue of developing reliable and fast fault detection scheme for protection of EHV/UHV transmission lines which is a requirement in modern power systems. The protection algorithm proposed in this thesis is based on the detection and analysis of traveling waves on transmission lines at inception of the faults. This algorithm relies on directional comparison between initial arrivals of traveling waves at each end of the protected line. This will determine whether or not a fault is inside the protected zone. In addition to, based on high voltage transmission network protection requirements proper phase selection algorithm is developed to handle single- phase tripping. Finally, by simulations carried out in PSCAD environment practical design considerations for implementing the new developed protection algorithm in a numerical relay unit is investigated. The results of simulation show that the proposed pilot protection scheme solves several issues encountered by using the conventional schemes and provide reliable and high speed protection for transmission lines.

The aim of this study is to analyse the voltage regulation of a power grid when wind power parks are connected to an existing power grid. Secondary the project have studied the placement of these wind power parks and costs related to connecting them to the grid. The goal was to achieve this grid with a smaller than 5% voltage margin and preferably a low phase deviation. The power grid is located in the area around Lule älven. Several issues with constructing and connecting windpower parks to an electrical grid have been studied by numerical analysis of a fictive grid but with real world variables. A balanced and stable grid is achieved with wind and hydro power and is able to successfully operate without non-renewable energy sources.The data was simulated in Matlab to analyse the power grid and the modification of it when connecting the wind power parks. The method used is power flow analysis through Matlab. All required unknown voltages and phase angles are determined and whether they are within given specifications. This entails that a stable electrical grid can be constructed

Infrared antennas are employed in sensing applications requiring specific spectral, polarization, and directional properties. Because of their inherently small dimensions, there is significant interaction, both thermal and electromagnetic, between the antenna, the antenna-coupled sensor, and the low-frequency readout structures necessary for signal extraction at the baseband modulation frequency. Validation of design models against measurements requires separation of these effects so that the response of the antenna-coupled sensor alone can be measured in a calibrated manner. Such validations will allow confident extension of design techniques to more complex infrared-antenna configurations. Two general techniques are explored to accomplish this goal. The extraneous signal contributions can be measured separately with calibration structures closely co-located near the devices to be characterized. This approach is demonstrated in two specific embodiments, for removal of cross-polarization effects arising from lead lines in an antenna-coupled infrared dipole, and for removal of distributed thermal effects in an infrared phased-array antenna. The second calibration technique uses scanning near-field microscopy to experimentally determine the spatial dependence of the electric-field distributions on the signal-extraction structures, and to include these measured fields in the computational electromagnetic model of the overall device. This approach is demonstrated for infrared dipole antennas which are connected to coplanar strip lines. Specific situations with open-circuit and short-circuit impedances at the termination of the lines are investigated.

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With the growing load demand, Ultra high Voltage (UHV) transmission lines are utilized in many countries around the world for bulk power transmission from remote locations over long distance. UHV transmission lines have typical features and it poses a challenge to the power system design with respect to protection, insulation and reactive power compensation, etc. Protection is a key issue in UHV transmission since a relay failure can interrupt and damage the power system. There are distance and differential protection schemes in the transmission line which account for security of the power system.  This thesis report is based on analysis carried out to find out the typical features associated with the UHV transmission systems. Also the impacts of the UHV transmission line characteristics on line distance protection scheme are observed. The traditional distance relays based on the lumped line parameters are not suited for the UHV transmission lines of very long distances. In this case a simulation is carried out for a 765 kV transmission system modeled in PSCAD. In such a case the non-linearity is even more prominent and the relay is less dependable. In line with the simulation and the analysis for the challenges in UHV transmission system, it is observed that the fault impedance of the line is non-linear and this non-linearity causes the failure of relay operation for a fault location at the boundary of the zone of protection. The fault simulation was carried out in PSCAD and the quadrilateral distance relay characteristics were plotted using MATLAB. From the simulation and results, it is finally concluded that traditional distance protection relays with lumped parameter line modeling is not suitable for UHV transmission liens due to non-linearity in fault impedance and it leads to relay failure. / Ultra high voltage (UHV) transmissionsledningar används i många länder till följd av ett växande behov av överföra hög effekt från avlägset belägna produktionsanläggningar till konsumenter. UHV-transmissionsledningar har speciella egenskaper som innebär utmaningar vid designandet av kraftsystem. Några utmaningar är systemskydd, isolation, och reaktiv effektkompensering. Systemskydd är en viktig aspekt för UHV-transmission eftersom haveri av reläskydd kan orsaka driftstopp och även skada ett kraftsystem. Det finns distans- och differentialskydd i transmissionsledningar som utgör skydd för kraftsystemet.  Denna avhandling är baserad på analyser som har utförts för att åskådliggöra de typiska egenskaperna som är sammankopplade med UHV-transmissionssystem. Även inverkan på distansskydd orsakad av karaktäristiken av UHV-transmissionsledningar utvärderas. De traditionella distansreläskydden som baseras på de sammanslagna ledningsparametrarna är inte lämpade för UHV-transmissionsledningar som stäcker sig över långa avstånd. I detta fall har en simulering utförts i PSCAD för ett transmissionssystem med spänningen 765 kV. I ett sådant fall är karaktäristiken ännu mer olinjär och reläskydden ännu mindre pålitliga. Det observeras att felimpedansen för ledningen är olinjär och till följd av detta orsakas problem med reläskydden då ett fel uppkommer vid utkanten av den skyddade zonen. Denna observation överensstämmer med simuleringarna och de förväntade utmaningarna kopplade till UHV. Simuleringar av felfall utfördes i PSCAD och karaktäristiken av reläskydden plottades med hjälp av MATLAB. Från resultat presenteras i rapporten, konkluderas det att konventionella distansskyddsreläer med modellering av sammanslagna ledningsparametrar inte är lämpliga för UHV-transmissionsledningar på grund av att den olinjära felimpedansen leder till att reläskydden havererar.

Yes / The paper demonstrates an effective technique to significantly enhance the bandwidth and radiation gain of an otherwise narrowband composite right/left-handed transmission-line (CRLH-TL) antenna using a non-Foster impedance matching circuit (NF-IMC) without affecting the antenna's stability. This is achieved by using the negative reactance of the NF-IMC to counteract the input capacitance of the antenna. Series capacitance of the CRLH-TL unit-cell is created by etching a dielectric spiral slot inside a rectangular microstrip patch that is grounded through a spiraled microstrip inductance. The overall size of the antenna, including the NF-IMC at its lowest operating frequency is 0.335λ0 × 0.137λ0 × 0.003λ0, where λ0 is the free-space wavelength at 1.4 GHz. The performance of the antenna was verified through actual measurements. The stable bandwidth of the antenna for |S11|≤ - 18 dB is greater than 1 GHz (1.4-2.45 GHz), which is significantly wider than the CRLH-TL antenna without the proposed impedance matching circuit. In addition, with the proposed technique the measured radiation gain and efficiency of the antenna are increased on average by 3.2 dBi and 31.5% over the operating frequency band. / This work is partially supported by RTI2018-095499-B-C31, Funded by Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER,UE), and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

The challenge to put power electronics on the same cost reduction spiral as integrated signal electronics has yet to be met. In the ongoing work for achieving complete power electronic converter integration, it has proven to be essential to develop a technology for integration of electromagnetic power passives. This integration will enable the incorporation of resonant circuits, transformers, EMI filters and the like into the integrated power electronics modules. These integrated electromagnetic power passives have been realized in terms of distributed structures, utilizing magnetic layers, conductive layers and dielectric layers. Because of the compact structures and the special implementation techniques of these integrated modules, the high frequency parasitic resonance are normally significant and may have negative impact on the performance and EMI characteristics. However, the existing modeling technique can only predict the fundamental resonant frequency and showed neither the causes of the high frequency resonance nor how to calculate those accurately. In this dissertation, comprehensive research work towards higher order electromagnetic modeling of integrated passive components is presented. Firstly, an L-C cell is identified as the basic building block of integrated passives such as an integrated series resonator. As an essential mistake in the structure evolution process of the original resonant transmission line primitive, the well-known conventional transmission line equivalent circuit as well as the equations are not applicable for the unbalanced current in an integrated passive module. For this particular application, a generalized transmission structure theory that applies to both balanced and unbalanced current has to be developed. The impedances of a generalized transmission structure with various loads and interconnections have been studied. An open-circuited load and a short-circuited load lead to series resonance and parallel resonance, respectively. The equations are substantiated with experimental results. Some preliminary study indicates the advantages of this unbalanced current passives integration technique. Since the existing integrated passive components are no other than some combination of this generalized transmission line primitive, the theoretical analysis may be applied to the further modeling of all integrated passive components. As the extension of the generalized two-conductor transmission structure model developed for the two-conductor approach, the generalized multi-conductor transmission structure theory has been proposed. As multiple L-C cells are putting in parallel, magnetic and capacitive coupling between cells cannot be neglected. To determine the capacitance between two adjacent conductors on top of the same dielectric substrate, Schwarz-Christoffel transformation and its inverse transformation have been applied with the calculation results verified by measurement. Based on the original voltage and current equations written in matrix form, modal analysis has been conducted to solve the equations. All these provide the basis for any further modeling of an integrated passive structure. Based on the basic L-C cell structure, this dissertation proposes an alternative multi-cell approach to the integration of reactive components and establishes the principles for its design and operation. It achieves the 3-D integration and has a PCB-mount chip-like structure which may have the potential to be more manufacturable, modularizable and mechanically robust. Different functional equivalents can be obtained by different PCB interconnections. The experimental results confirm the functionality as integrated reactive components for applications such as high frequency resonators. To apply the multi-conductor generalized transmission structure model to practical integrated passives structures, three typical cases have been studied: spiral-winding structure integrated series resonator, multi-cell structure integrated series resonator and integrated RF EMI filter. All these structures can be treated as one or more multi-conductor transmission structures connected in certain patterns. Different connection patterns only determine the voltage and current boundary conditions with which the equations can be solved. After obtaining the voltages and currents at each point, the impedance or transfer gain of a structure can be obtained. The MATLAB calculation results correlate well with the measurement results. The calculation sensitivities with respect to variation of various parameters are also discussed and causes of resonance at different frequency range are identified. The proposed generalized transmission structure model based on matrix modal analysis is rather complex and takes a lot of computer time especially when the number of turns is large. Furthermore, the operating frequency of an integrated resonant module is normally around its 1st resonant frequency and up to the 2nd resonant frequency. Therefore, a more simplistic higher order lumped element model which covers the operating range up to the 2nd resonant frequency may be good enough for the general design purpose. A higher order equivalent circuit model for integrated series resonant modules as an example of integrated power passives is presented in this dissertation. Inter-winding capacitance is also considered compared to the conventional 1st order approximation model. This model has been verified by small-signal test results and can be easily implemented into the design algorithm as part of the high frequency design considerations. The wide band modeling and proposed new structure mentioned above provide a comprehensive basis for better design of integrated passive components. As a general frequency plane modeling approach, the work presented in this dissertation may be extended to other passive structures, such as multi-layer capacitors, planar magnetics, etc.. / Ph. D.

This dissertation aims to develop decision-making tools that aid power grid operators in mitigating extreme events. Two distinct areas are focused on: a) improving grid performance after a severe disturbance, and b) enhancing grid monitoring to facilitate timely preventive actions. The first part of the dissertation presents a proactive islanding strategy to split the bulk power transmission system into smaller self-adequate islands in order to arrest the propagation of cascading failures after an event. Heuristic methods are proposed to determine in what sequence should the island boundary lines be disconnected such that there are no operation constraint violations. The idea of optimal partitioning is further extended to the distribution network. A planning problem for determining which parts of the existing distribution grid can be converted to microgrids is formulated. This partitioning formulation addresses safety limits, uncertainties in load and generation, availability of grid-forming units, and topology constraints such as maintaining network radiality. Microgrids help maintain energy supply to critical loads during grid outages, thereby improving resilience. The second part of the dissertation focuses on wide-area monitoring using Phasor Measurement Unit (PMU) data. Strategies for data imputation and prediction exploiting the spatio-temporal correlation in PMU measurements are outlined. A deep-learning-based methodology for identifying the location of temporary power systems faults is also illustrated. As severe weather events become more frequent, and the threats from coordinated cyber intrusions increase, formulating strategies to reduce the impact of such events on the power grid becomes important; and the approaches outlined in this work can find application in this context. / Doctor of Philosophy / The modern power grid faces multiple threats, including extreme-weather events, solar storms, and potential cyber-physical attacks. Towards the larger goal of enhancing power systems resilience, this dissertation develops strategies to mitigate the impact of such extreme events. The proposed schemes broadly aim to- a) improve grid performance in the immediate aftermath of a disruptive event, and b) enhance grid monitoring to identify precursors of impending failures. To improve grid performance after a disruption, we propose a proactive islanding strategy for the bulk power grid, aimed at arresting the propagation of cascading failures. For the distribution network, a mixed-integer linear program is formulated for identifying optimal sub-networks with load and distributed generators that may be retrofitted to operate as self-adequate microgrids, if supply from the bulk power systems is lost. To address the question of enhanced monitoring, we develop model-agnostic, computationally efficient recovery algorithms for archived and streamed data from Phasor Measurement Units (PMU) with data drops and additive noise. PMUs are highly precise sensors that provide high-resolution insight into grid dynamics. We also illustrate an application where PMU data is used to identify the location of temporary line faults.

This research investigates the realization of parametric amplification in superconducting circuits and structures where nonlinearity is provided by Josephson junction (JJ) elements. We aim to develop a systematic analysis over JJ-based devices toward design of novel traveling-wave Josephson parametric amplifiers (TW-JPA). Chapters of this thesis fall into three categories: lumped JPA, superconducting periodic structures and discrete Josephson transmission lines (DJTL). The unbiased Josephson junction (JJ) is a nonlinear element suitable for parametric amplification through a four-photon process. Two circuit topologies are introduced to capture the unique property of the JJ in order to efficiently mix signal, pump and idler signals for the purpose of signal amplification. Closed-form expressions are derived for gain characteristics, bandwidth determination, noise properties and impedance for this kind of parametric power amplifier. The concept of negative resistance in the gain formulation is observed. A design process is also introduced to find the regimes of operation for gain achievement. Two regimes of operation, oscillation and amplification, are highlighted and distinguished in the result section. Optimization of the circuits to enhance the bandwidth is also carried out. Moving toward TW-JPA, the second part is devoted to modelling the linear wave propagation in a periodic superconducting structure. We derive closed-form equations for dispersion and s-parameters of infinite and finite periodic structures, respectively. Band gap formation is highlighted and its potential applications in the design of passive filters and resonators are discussed. The superconducting structures are fabricated using YBCO and measured, illustrating a good correlation with the numerical results. A novel superconducting Transmission Line (TL), which is periodically loaded by Josephson junctions (JJ) and assisted by open stubs, is proposed as a platform to realize a traveling-wave parametric device. Using the TL model, this structure is modeled by a system of nonlinear partial differential equations (PDE) with a driving source and mixed-boundary conditions at the input and output terminals, respectively. This model successfully emulates parametric and nonlinear microwave propagation when long-wave approximation is applicable. The influence of dispersion to sustain three non-degenerate phased-locked waves through the TL is highlighted. A rigorous and robust Finite Difference Time Domain (FDTD) solver based on the explicit Lax-Wendroff and implicit Crank-Nicolson schemes has been developed to investigate the device responses under various excitations. Linearization of the wave equation, under small-amplitude assumption, dispersion and impedance analysis is performed to explore more aspects of the device for the purpose of efficient design of a traveling-wave parametric amplifier. Knowing all microwave characteristics and identifying different regimes of operation, which include impedance properties, cut-off propagation, dispersive behaviour and shock-wave formation, we exploit perturbation theory accompanied by the method of multiple scale to derive the three nonlinear coupled amplitude equations to describe the parametric interaction. A graphical technique is suggested to find three waves on the dispersion diagram satisfying the phase-matching conditions. Both cases of perfect phase-matching and slight mismatching are addressed in this work. The incorporation of two numerical techniques, spectral method in space and multistep Adams-Bashforth in time domain, is employed to monitor the unilateral gain, superior stability and bandwidth of this structure. Two types of functionality, mixing and amplification, with their requirements are described. These properties make this structure desirable for applications ranging from superconducting optoelectronics to dispersive readout of superconducting qubits where high sensitivity and ultra-low noise operation is required.