Open Theses & Dissertations

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A compact power supply for dielectric barrier discharge devices
(University of New Brunswick, 2016) Allen, Brad; Saleh, Saleh; Colpitts, Bruce
Plasma generation by dielectric barrier discharge (DBD) devices has recently become a topic of interest for researchers due to the growing number of industrial applications. Some applications of note include: generation of ozone gas for disinfecting and cleaning, aerodynamic flow control over an airfoil, light emission for plasma displays and CO2 lasers, and others. The emergence of these new applications, specifically aerodynamic flow control for aeronautical applications, has created significant need for adaptable, compact and lightweight power supplies. The majority of the required high-voltage and high-frequency AC supplies employed by DBD devices have been based on resonant-type power electronic converters (PEC’s). Nonetheless, resonant PEC’s typically are neither small nor lightweight, which make them less desirable for supplying DBD devices in aeronautical applications. In addition, resonant PEC’s are generally not adaptable as their AC outputs are produced over a narrow frequency range, and their operation requires complicated control schemes. In this work, the size and weight requirements of a DBD device for aeronautical applications will be achieved using multi-stage and multi-level switch mode PEC’s. The multi-stage structure will consist of multiple DC-DC step-up PEC’s supplied from batteries. These DC-DC PEC’s will feed a multi-level DC-AC PEC, which will be operated to produce high voltages over a wide range of high frequencies. The DC-DC and DC-AC PEC’s will be operated using switching signals generated by digital signal processing (DSP) platform in order to ensure high quality AC outputs. Moreover, desired switching signals will be generated to facilitate adjusting the magnitude and the frequency of the output AC voltage. Such adjustments will allow manipulation of the DBD body force and/or the plasma velocity, which alters the thrust and/or the boundary layer separation. This work focuses on the design, construction, performance testing, and optimization of the size and weight of a power supply for a DBD device for aeronautical applications. Modeling and simulation tests have been conducted for various operating conditions. An experimental prototype was constructed for performance evaluation of the multi-stage and multi-level power supply, test results are reported and compared to the predictions.
A digital modular protection for wind energy conversion systems with battery storage
(University of New Brunswick, 2018) Meng, Ryan, J.; S. Saleh
During the past few decades, there has been a substantial increase in the global installed wind energy capacity that is driven by growing demands for clean and sustainable energy sources. This has triggered rapid advancements in the technologies employed for wind energy conversion systems (WECS) to ensure reliable and stable integration into power systems. Increasing numbers of interconnected WECSs have created several challenges that can adversely impact the operation, control, and stability of the power system. These challenges have been addressed by several industrial codes aiming to minimize the possible impacts of interconnecting WECSs to their host power systems. The focus of such codes is to satisfy the requirements of cottage and frequency stability under the intermittent power production by WECSs. Industrial codes have also identified the deployment of energy storage systems (ESSs) to mitigate variations in power injected by WECSs. Control and protection of ESSs must ensure reliable operation, where response to any undesired even test be initiated with minimum disruption in the power injected to the host power system. The technologies utilized in WECSs are heavily dependent on power electronic converters (PECS) to facilitate extracting power for the wind, and to regulate the power injected to the host power system. On one hand, standardized designs of PECs require featuring them with built-in protection to limit the current flow and attenuate voltage transients across the switching elements. On the other hand, the controllers employed in WECSs and their ESSs operate PECs to meet the requirements of voltage and frequency stability as per the industrial codes. Built-in protection and controller actions can result in non-conventional behaviors of fault currents, this complicating the detection of faults involving a WECS and/or its ESS. A common protection practice for WECS and ESS is to coordinate the responses of multiple protective devices used in WECSs and their ESSs. The main challenge for the coordinated protection in WECSs with ESSs, is due to the use of several PECs, which can alter fault currents. In addition, conventional protective devices suffer limited accuracy in detecting faults involving PECs, where ineffective coordination can result in mal-function of protective devices. This research work aims to develop, implement, and test a new method for managing the responses of multiple protective devices employed in a WECS with ESSs. The proposed method is based on deploying multiple digital protective devices, each of which provides protection to a specific component in the WECS and its ESS. Each protective device is featured with phaselet-based fault detection, which can offer accurate, fast, and reliable detection of faults. The use of the a phaselet-based digital protective devices can help implement a reliable management of protection responses to isolate the faulty component(s). The proposed management of protection responses is called the digital modular protection, which is developed to have its outputs as signals to operate circuit breakers in different parts of the protected WECS and its ESS. The digital modular protection is implemented for performance testing on a WECS that has a battery-bank style storage system. Performance tests are conducted for various fault and non-fault events. Test results demonstrate accurate, fast, and reliable responses for fault and non-fault events with negligible sensitivity to the type and/or location of faults.
A dynamic approach to balance assessment using self-induced perturbations
(University of New Brunswick, 2020) Chambers, Neil Cameron; Scheme, Erik; Sensinger, Jonathon
A novel balance assessment method for older adults was developed using a balance platform that induces dynamic self-perturbations and which could use synchronization as an adjustable level of assistance. Rather than measure the subject’s performance, the proposed balance assessment measures how much assistance they need to reach a standard level of performance. A swaying balance platform was constructed and instrumented to conduct the balance assessment with different levels of assistance. Nineteen healthy young adults were tested with self-perturbations introduced by following swaying visual instructions that changed frequency instantaneously. Experimental results were unable to confirm if synchronization was capable of providing assistance, nor whether the assessment outcomes could benefit from applying different levels of assistance. Future studies should focus on understanding how to ensure that synchronization occurs in the combined subject/instructions system.
A dynamic spinning reserve energy management system to improve microgrid resilience
(University of New Brunswick, 2024-03) Shafiee, Mohammadreza; Cardenas Barrera, Julian; Hill, Eugene
This thesis focuses on enhancing microgrids' resiliency and operational planning during incidents leading to islanding operations. The importance of grid resilience and the need to enhance microgrid capability during islanded operations as a probabilistic phenomenon are highlighted. The development of a dynamic spinning reserve, as well as addressing the imbalances between generation and consumption, is considered. This work contributes by proposing a multi-objective optimization problem for maintaining a balance between resilient operation (socio-technical optimization) and economic operation (techno-economic optimization) by considering uncertainties. The research emphasizes the importance of considering low probability events with high impact on the grid, such as weather conditions, in operational planning to improve resilience and minimize load shedding. Mathematical models, objective functions, and solution methods such as Epsilon-constraint and Fuzzy Satisfaction Method (FSM) are used to accurately model the network, evaluate microgrid actors' behaviour, and solve the multi-objective optimization problem.
A fractional-bits-per-symbol communication system for low-power satellites using N-Point PSK constellations
(University of New Brunswick, 2022) Wedemire, Benjamin J.; Petersen, Brent
Low-Earth orbiting satellites are becoming more common and transmit to ground stations through slowly fading radio channels. Radio links operating in this channel cannot operate efficiently with static communication systems making adaptive communication links critical. A fractional-bits-per-symbol communication system is presented as a possible improvement on current adaptive systems. Fractional-bits-per-symbols are realized by utilizing N-point PSK constellations and sequences. Sequences allow for N-point constellations to transmit whole numbers of bits over a number of grouped symbols called a waveform. Equations governing sequences and waveforms are presented. Mapping schemes are used to map bit-strings to waveforms and are shown to have an effect on the performance. Results of simulations using fractional-bits-per-symbols are presented. Theoretical data throughput is compared for low-Earth orbiting satellites using fractional and non-fractional-bits-per-symbol systems.
A modular protection for grid-connected battery storage systems
(University of New Brunswick, 2018) McSheffery, Ryan; Saleh, Saleh
Power systems have been showing a growing interest in utilizing different types of energy storage systems (ESSs), which can be operated as interconnected components. Such ESSs are sought to accommodate high penetration levels of renewable energy, peak-demand management, smart grid functions, and energy markets. Battery units, flywheels, compressed gas, pumped hydro, super capacitors, and superconducting magnetic energy storage (SMES) units are among the popular energy storage systems that have shown potential application for interconnected operation. The design and operation of interconnected ESSs, along with improving the power density, have been subjects for several research works, which recommended the use ESSs with electric energy storage for high power applications. These recommended ESSs include battery units, supper capacitors, SMES units, compressed gas and pumped hydro. The majority of recommended ESSs require the use of power electronic converters (PECs) for charge and discharge operation. Nowadays, battery units, super-capacitors, and SMESs are commercially available with a wide range of power and voltage ratings. Despite the remarkable improvements in the efficiency, reliability, and power density of interconnected battery, super-capacitor, and SMES based ESSs, their protection remains a challenge for their host power systems. In the majority of grid-connected ESSs, the protection is designed using current-based and/or voltage-based protective devices. Several research works have been conducted to address the possible impacts of interconnected ESSs on utility-grade protective devices. The outcomes of these research works have suggested that interconnected ESSs can contribute to fault currents, and adversely impact the responses of upstream non-unit protective devices. Furthermore, these research works have recommended featuring the main controllers of interconnected ESSs with faster responses to changing conditions of the ESSs. However, meeting such a recommendation has to consider the controller characteristics, type of fault, maximum input and output currents, and state-ofcharge of protected ESSs. Other approaches have been developed to address the challenges facing protective devices due to interconnecting ESSs, including the directional relays, adaptive coordination, voltage relays, and communication-assisted relays. These approaches have shown some limited performance due to the impacts of PECs and their controllers on the voltage-current behaviors during and post fault conditions. Moreover, the ability of the relays used demonstrated limited capabilities to detect faults involving grid-connected PECs. The main objective of this research is to develop and test a new digital protection scheme for interconnected ESSs. The proposed digital protection will be designed using multiple digital relays that are located in different parts of the protected ESS. The overall response of the proposed digital protection will be set as a combination of responses by digital relays to maintain a reliable power flow to or from the host power system. The proposed digital protection will be tested for an interconnected battery ESS under different operating and fault conditions.
A multi-variate approach to predicting myoelectric control usability
(University of New Brunswick, 2020) Nawfel, Jena; Scheme, Erik; Englehart, Kevin
Pattern recognition techniques leveraging the use of electromyography (EMG) signals have become a popular approach to provide intuitive control of myoelectric devices. Performance of these control interfaces is commonly quantified using offline classification accuracy, despite researchers having shown that this metric is a poor indicator of usability. Several attempts have been made to find alternative training metrics that better correlate with online performance. Moderate correlations have been identified in some cases; however, the relationship between offline training and online usability has yet to be fully defined in the literature. The following work attempts to bridge this information divide by exploring combinations of offline training metrics capable of predicting myoelectric control usability. The results indicate that linear combinations of three offline training metrics provide superior predictive power of future online performance. Additionally, the role of feedback presented to the user during training is explored to determine its effect on performance and predictability. The results of this study suggest that properly designed feedback mechanisms can influence both the quality of the training metrics and the predictive ability of the developed linear models.
A Software Defined Radio Implementation of Direct Sequence Spread Spectrum Harmonic Radar
(University of New Brunswick, 2022-06) Kozma, Nicholas; Colpitts, Bruce G.
Proposed is a harmonic radar system back end that makes use of an off the shelf software defined radio to yield a low-form factor and light weight transceiver. This module, composed of the USRP b200 mini software defined radio and the Raspberry Pi 4 computer, forms a flexible test bed for harmonic radar waveform research and testing. Using the transceiver module a variety of direct sequence spread spectrum waveforms were used to detect a tag with the intention of testing the system and finding the most favorable sequence of the proposed options. Although an SDR is unlikely to outperform a custom transceiver optimized for a given application, it has been found that they make a suitable low cost alternative working best with coded radar waveforms.
Active power filters for harmonic mitigation in power systems
(University of New Brunswick, 2023-08) Siddique, Riashad; Meng, Julian
The use of power electronics in all types of industrial, commercial, and residential loads can cause system-wide reduction of the power quality from harmonic distortion of the AC waveform. Residential non-linear loads resulting from heavily used power electronic devices and renewable energy sources at the distribution power system level can significantly contribute to harmonic distortion. With excessive harmonic distortion, traditional mitigation methods such as using passive filtering has had limited success. As such, this thesis aims to utilize active power filters to improve the distribution power quality affected by unwanted harmonic components. Various time and frequency domain harmonic detections methods are proposed and implemented in a shunt configuration topology. The goal is to assess active filtering techniques based on previously published research with novel modifications to improve performance based on harmonic reduction and convergence speed (settling time) in time-varying conditions.
Aggregated load forecast and control for creating alternative power system resources using thermostatically controlled loads
(University of New Brunswick, 2021) Gong, Xun; Guerra, Eduardo Castillo; Barrera, Julian Cardenas
Power systems are evolving and are trying to use loads and communication infrastructure as a way to compensate the system generation for peak load shaving and ancillary services. Thermostatically controlled loads (TCLs) have electric operational flexibility that makes them suitable for the compensation via direct load control. Aggregated load forecast and control are critical to transform "TCLs with uncertain demand" into "manageable power system resources." The forecast provides predictive information about baseline loads showing normal energy demand of consumers. The control makes TCL aggregations fully responsive to its upper-level requests, which are the focus of this dissertation. This dissertation investigates two multi-horizon forecast engines for aggregated TCLs: (I) wavelet decomposition-based neural networks with K-means clustering (WNN), and (II) a convolutional neural network-based method (CNN). WNN demonstrates a way to achieve accurate aggregated TCL forecasting by using traditional NNs with proper structure design and predictor selection. CNN provides TCL aggregations a generic forecaster without the need to extract specific predictors. The two forecast engines were studied with different types of TCLs and different aggregation sizes, resulting in an enhanced performance when compared with benchmark algorithms. The dissertation also theoretically derives and analyzes aggregation effects showing the dependence between forecast accuracy and aggregation sizes. Additionally, a scalable forecast mechanism is proposed to aggregate forecasts from individual forecast engines, enabling fast forecast deployments with improved accuracy. The proposed mechanism relies on a bottom-up approach with a new Markov-based error reduction algorithm, leading to 20-80% performance improvement when the method is tested with different forecast horizons. Aggregated TCLs can be controlled to join electricity markets with a central hub, virtual power plant. However, there are two main concerns for aggregated load control. The first is associated with the dispatchability of virtual power plant against normal energy demand of individual TCLs in uncertain time-variant environments. The second refers to the tremendous increase of communication and computational requirements needed to perform direct load control on a large population of TCLs. This dissertation introduces aggregators between the direct load controller and TCLs with a novel robust control mechanism to reconcile these concerns. The control is implemented with two layers: the upper layer suppresses the control payback effect with a quadratic optimization model, and the lower layer addresses the power trajectory tracking with a novel payback tracking error model. The control method needs minimum sensing infrastructure since it requires power data only at the aggregation level. Simulations showed a robust reference power tracking characteristic of the aggregator with a percentage root mean squared error between 3.33% - 5.69% under uncertain time-variant environments. The continuous responsiveness indicates that the aggregators manage to convert the aggregated TCLs into "manageable resources" that ensure the dispatchability of virtual power plant. This approach could allow modern power systems to implement new trends such as "load following generation" which could save resources and reduce the environmental impact of power generation and distribution.
Aggregated modeling and control of domestic electric water heaters
(University of New Brunswick, 2022-12) Tuse, Shwaraj Rajkumar; Diduch, Chris
The rollout of Distributed Energy Resources (DERs) is coming into play to reduce the carbon footprint and provide better service to the consumers. However, balancing generation and demand by controlling individual DERs while maintaining grid stability is a crucial challenge. Domestic electric water heaters (DEWHs) are one of the significant contributors to the residential load in New Brunswick. According to previous studies [1] [2], the aggregated load profile of DEWHs follows a similar pattern as the total load profile. Thus, by managing the load curve of DEWHs, we can significantly change the shape of the aggregated residential load curve. The control strategy is to shift the aggregated load up or down relative to the baseline to track the desired load profile. This research focuses on maintaining end use devise performance to guarantee customer satisfaction. The research contributions are – • Development of a smart switch that maps the control variable to shift the operating setpoint of DEWH. • An algorithm that simulates water draw events across the fleet of water heaters by capturing water usage patterns. • A new aggregated load control system that tracks dispatch instructions precisely under certain conditions.
An exploration of EEG-based, non-stationary emotion classification for affective computing
(University of New Brunswick, 2020) Bendrich, Nicole; Scheme, Erik
The monitoring of emotional state is important in the prevention and management of mental health problems and is increasingly being used to support affective computing. Researchers are exploring various modalities from which emotion can be inferred, such as through facial images or via electroencephalography (EEG) signals. Current research commonly investigates the performance of machine-learning-based emotion recognition systems by exposing users to short films that are assumed to elicit a single known emotional response. Assuming static emotions, even for these brief periods, however, does not consider that emotions evolve. Moreover, in order to demonstrate better results, many existing models are not tested in ways that reflect realistic real-world implementations. In this thesis, the dynamic evolution of emotions induced using longer and variable stimuli is explored using EEG signals from the publicly available dataset, AMIGOS. A variety of feature engineering and selection techniques are applied and evaluated across four different cross-validation frameworks. The role of imperfect labelling of ground truth emotions and both data and gender-imbalances in the dataset are also investigated. Improved feature design and selection lead to up to 13% absolute improvement relative to comparable previously reported studies using this dataset. Alternative training configurations and a selective confidence-based classification scheme are proposed, leading to further possible improvements.
An investigation of transition-informed classifier adaptation for myoelectric control
(University of New Brunswick, 2023-12) Meneley, Julia; MacIsaac, Dawn; Scheme, Erik
Myoelectric prostheses use pattern recognition of surface electromyography (SEMG) to interpret a user’s intent. Over time, changes in the SEMG worsen the usability of these prostheses, requiring cumbersome retraining. Adaptive learning, although able to update the classifier, suffers from mislabelling errors during unsupervised use. This study aimed to overcome this by investigating the impact of transitions between classes, often associated with elevated misclassification, on the adaptation process. Several adaptation techniques, some based on explicitly avoiding transitions and others based on leveraging awareness of transitions to improve decision stream labelling, were explored. Finally, these transition-informed adaptation techniques were tested on two datasets that included sequences of transitions between known classes. Results suggest that an awareness of transience in the SEMG can inform the data selection process and improve the labelling of unsupervised data for adaptation. A resulting LC-SSL technique yielded significant (p¡0.05) improvement to several offline classifier performance metrics.
Antenna development for MIMO and UHF RFID applications
(University of New Brunswick, 2014) Rouse, Chris; Colpitts, Bruce; Petersen, Brent
Multiple-input multiple-output (MIMO) wireless communication systems are capable of achieving significantly higher channel capacities than single-antenna systems. Furthermore, there has been a trend toward installing a larger number of cellular base stations and wireless access points (APs) over the same physical coverage area in order to meet increasing capacity demands. An in-room MIMO system—in which an AP and a user with a portable device (PD) occupy the same room—is considered. The associated channel is dominated by line-of-sight (LOS) components, which tend to increase the received signal-to-noise ratio (SNR) but can degrade MIMO performance. Therefore, the application of elevation-directional (θ-directional) AP antennas which emphasize wall-reflected non-line-of-sight (NLOS) components is investigated to improve in-room MIMO capacity. Simulation results based on the experimental set-up suggest an improvement in mean MIMO capacity on the order of 13 % coupled with a 4 % increase in mean relative MIMO gain if the AP antenna radiation patterns strike a balance between improving MIMO channel conditions and maintaining an appropriate SNR. The associated measurements revealed only a 5 % improvement in mean MIMO capacity and a small reduction in mean relative MIMO gain due to the increased multipath richness associated with the real environment. However, the measured results validated the predicted relationship between the main lobe directions of the AP antenna radiation patterns and the resulting in-room MIMO performance, suggesting that more significant improvements could be achieved for in-room MIMO systems experiencing less multipath richness. In the design of ultra-high frequency (UHF) radio-frequency identification (RFID) tags, the cost of the tag antenna is significant relative to that of the entire tag. As a result, cost-effective alternatives to copper as a UHF RFID tag antenna conductor have been explored in recent years. The feasibility of constructing such antennas using electrically conductive paper is investigated through simulations and experimental measurements. Results suggest that the conductivity of the paper is prohibitively low; however, reasonable performance would be achieved if the paper conductivity were increased by an order of magnitude.
Assessment of vadose zone solute transport under a potato field by a 19 month time-lapse cross-hole resistivity imaging survey
(University of New Brunswick, 2017) Wang, Shuang; Petersen, Brent; Butler, Karl; Danielescu, Serban
Nitrate is a necessary nutrient for crops, however high concentrations of nitrate in surface water and groundwater can negatively affect aquatic ecosystems and human health. 3D cross-hole Electrical Resistivity Imaging (ERI) has been used to investigate the percolation of a conductive tracer (KCl) through a 17 m thick vadose zone as a proxy for the transport of nitrate under natural recharge conditions. Post-tracer surveys indicate that tracer movement has slowed significantly by early May, 2015 (about one month after tracer application), at the end of snow melt. The shallow conductivity anomaly produced by the tracer diminished significantly over the winter and spring of 2016, but showed little evidence of bulk matrix flow below approximately 6 m depth (top of the bedrock). It is speculated that fractures in the bedrock, too thin to be resolved by the ERI survey, conveyed tracer downward. After 18.5 months, there is no ERI evidence of tracer migrating through the matrix below approximately 6 m.
Autonomous assistance-as-needed control of a lower limb exoskeleton with guaranteed stability
(University of New Brunswick, 2020) Campbell, Samuel; Sensinger, Jonathon; Diduch, Chris
Lower-limb stroke rehabilitation is physically demanding on therapists and requires the concerted effort of multiple staff members. Researchers have accordingly begun investigating the use of lower-limb exoskeletons for rehabilitation. Unfortunately, if the exoskeleton ensures the correct trajectory regardless of whether or not the user contributes effort, rehabilitation can be ineffective as the patient can begin to slack. Recent research suggests using assistance-as-needed control to facilitate functional motor recovery by only applying torques if the patient deviates too far from the desired trajectory. Assistance-as-needed control has been difficult to employ in lower-limb exoskeletons, however, due to the need to ensure stability. This work demonstrates how virtual constraint control—a method used in prostheses and assistive exoskeleton control with robust stability properties—can be combined with a velocity-modulated deadzone to ensure stability. The simulations suggest the method can accommodate a large deadzone while remaining stable across a range of gait pathologies.
Baseline noise and model parameters in surface electromyography
(University of New Brunswick, 2017) Raghu, Shriram, Tallam Puranam; MacIsaac, Dawn; Parker, Philip
The Pairwise Attribute Noise Detection Algorithm has been recommended by others as a way to classify surface electromyography signals as clean or noisy. To train the algorithm, simulation can be used to generate clean examples. Used in this way, the algorithm has been shown to perform well for classifying simulated test signals, but not for in vivo SEMG records. This work investigated the poor performance with in vivo SEMG records in order to improve it, if possible. Impact of introducing instrumentation effects into simulated signals was shown to be negligible. Impacts from judicious selection of simulation parameters, including both embedded and user specified values was shown to significantly improve falsely classifying clean records as noisy. A genetic algorithm was developed to provide support for choosing user specified values and using this technique, false positive rates (i.e. classifying clean signals as noisy) decreased from 95 % to 20 %, without degradation of other classification rates (i.e. classifying noisy signals as noisy, clean signals as clean).
Co-simulation of power and communication networks
(University of New Brunswick, 2022-06) Fernandes, Jonas Philip; Meng, Julian; Cardenas, Julian
The smart grid uses information and communication technologies to improve the efficiency, reliability, sustainability, and resilience of the modern power system. The new cyber-physical power systems require simulation tools to consider the performance effects of the communication system. There have been several approaches to obtain multi-domain (power and communication domains) models for the smart grid, but integrating existing domain-specific simulators can leverage well-proved models, techniques, and professional knowledge already developed. This thesis focuses on this approach, called co-simulation, and proposes a framework suitable to study power systems with high penetration of distributed energy resources. The proposed co-simulation framework uses a master-slave architecture where two popular, domain-specific simulators collaborate under the commands of a co-simulation coordinator. The coordinator was designed to ensure proper time synchronization between the continuous time-based power, and the event-driven communication, simulations. Developed in Python, it uses a COM interface and a MySQL database to implement inter-process communications and data exchange mechanisms. OpenDSS and OMNeT++ were selected as power and communications simulators, respectively. The framework is evaluated using standard IEEE buses and real utility test cases. The results show the effectiveness of the solution to assess the impacts of communications on important operational parameters of the power system. Finally, the thesis outlines the contributions of the work and some improvements as future work.
Control in cogeneration islanding systems for Saudi Aramco Processing Facilities
(University of New Brunswick, 2015) Alkhaldi, Bader Saud; Hill, Eugene; Chang, Liuchen
The Saudi Aramco Processing Facilities (SAPF) are located in an eastern province of Saudi Arabia. While the plant has three industrial cogeneration units, and is connected to the Saudi national grid via two transmission lines, there is a possibility that both transmission lines will be isolated due to storms or other disturbances. If that happens SAPF would be in an isolated, or islanded, mode of operation. The three units would need to be coordinated to supply the required internal plant power demand in all cases where there initially was export to, or import from, the grid. To achieve this, a model is required that will ensure effective transition from interconnected to islanding mode. When islanding schemes function properly, the plant can continue operating under its own power generation despite interruptions in electrical supply from the utility grid. Without the implementation of the islanding mode of operation, any disturbance in the grid could cause a blackout, severely disrupting the plant operations, causing revenue loss and gas flaring. A fully functioning islanding scheme refers to the capability of the plant generators to withstand any disturbance to the power system and continue supplying the plant load. Continual balancing of active power generated and consumed is vital for power system security and stability, and to maintain frequency within an acceptable tolerance around nominal system frequency. Due to the large size of individual generators (150 MW each unit, a total of 450 MW) with respect to total in plant load (170 MW), the loss of a generator in a small island system can cause a large power imbalance and consequently a significant frequency excursion. Achievement of the above goal requires creation of an accurate model for the SAPF cogeneration and electrical network that includes gas turbine, governor, generator and power system. A simple model, the six-parameter linearized model, and the full nonlinear model have been used to represent the synchronous generator in different studies. The governor model is part of the turbine model in gas turbines. The excitation system and the power system stabilizer models have been based on the IEEE Standard. Specific models have been simulated in MATLAB®, and open inclusion of the transmission lines has been done in ETAP®. Critical scenarios that may lead to total blackout of the SAPF have been simulated and analyzed. This thesis provides a justification of future use of special protection systems on the SAPF power system to provide successful transition from interconnection mode of operation to islanding mode of operation during major disturbances. The special protection systems proposed are capable of handling cases of high export to the grid, and also import from the grid. Recommendations and future work are summarized at the conclusion of the thesis.
Coupled-mode theory for RF and microwave resonators
(University of New Brunswick, 2013) Elnaggar, Sameh; Tervo, Richard; Mattar, Saba
The case of two dielectric resonators inserted in a cavity is fully analyzed. It is shown that the three uncoupled modes interact to form three coupled ones. Accordingly, Energy Coupled-Mode Theory, a coupled mode formalism where energy is conserved, is developed to study the coupling of RF and microwave resonators. The governing equations are written in the form of an eigenvalue problem where the eigenvalues represent the square of the frequencies and the eigenvectors are the fields’ coefficients. Both external and internal boundary conditions are discussed. The coupled mode formalism is capable of analyzing a system consisting of an arbitrary number of resonators. Using the proposed equations, the physical origin of the coupling coefficient is found and interpreted based on the energy conservation principle. The interpretation is general and universal and is believed to encompass cases where dielectrics and conductors are present. An important electron paramagnetic resonance probe, namely a cavity with a tiny insert, is studied. It is shown that when the frequency of the cavity is equal to that of the insert, the resulting fields are complete mixes of the two uncoupled modes. This finding, together with others, finds applications in the magnetic resonance and dielectric measurements fields. Different practical scenarios (large/small cavities, high/moderate relative permittivity values) are discussed in detail. Expressions for field dependent parameters such as coupling coefficients, Q values, filling factors and resonator efficiency are derived. It is shown how these parameters contribute to the probe performance and how, in some circumstances, trade-offs need to be made. Design procedures for electron paramagnetic resonance probes, verified using finite-element simulations, are proposed. It is found that proper design can indeed enhance the electron paramagnetic resonance signal. Particularly, the shield can help in boosting the resonator efficiency of a lossy dielectric resonator. The method of images, area commonly used electromagnetic technique, is used together with the coupled mode theory to study cases where resonators are placed close to conducting planes. The aforementioned situations occur in the field of magnetic resonance spectroscopy when dielectric resonators are used as tuners. These situations also exist when conducting planes are used to enhance wireless power transfer using resonant inductive coupling.

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