There is a growing interest in investigating the high order contingency events that may result in large blackouts, which have been a great concern for power grid secure operation. The actual number of high order contingency is too huge for operators and planner to apply a brute-force enumerative analysis. This thesis presents a heuristic searching method based on particle swarm optimization (PSO) and tabu search to select severe high order contingencies. The original PSO algorithm gives an intelligent strategy to search the feasible solution space, but tends to find the best solution only. The proposed method combines the original PSO with tabu search such that a number of top candidates will be identified. This fits the need of high order contingency screening, which can be eventually the input to many other more complicate security analyses. Reordering of branches of test system based on severity of N-1 contingencies is applied as a pre-processing to increase the convergence properties and efficiency of the algorithm. With this reordering approach, many critical high order contingencies are located in a small area in the whole searching space. Therefore, the proposed algorithm tends to concentrate in searching this area such that the number of critical branch combinations searched will increase. Therefore, the speedup ratio is found to increase significantly. The proposed algorithm is tested for N-2 and N-3 contingencies using two test systems modified from the IEEE 118-bus and 30-bus systems. Variation of inertia weight, learning factors, and number of particles is tested and the range of values more suitable for this specific algorithm is suggested. Although illustrated and tested with N-2 and N-3 contingency analysis, the proposed algorithm can be extended to even higher order contingencies but visualization will be difficult because of the increase in the problem dimensions corresponding to the order of contingencies.

The declining cost of photovoltaic (PV) modules has enabled the vision of ubiquitous photovoltaic (PV) power to become feasible. Emerging PV technologies are facilitating the creation of intentionally non-flat PV modules, which create new applications for this sustainable energy generation currently not possible with the traditional rigid, flat silicon-glass modules. However, since the photovoltaic cells are no longer coplanar, there are significant new requirements for the power electronics necessary to convert the native form of electricity into a usable form and ensure maximum energy harvest. Non-uniform insolation from cell-to-cell gives rise to non-uniform current density in the PV material, which limits the ability to create series-connected cells without bypass diode or other ways to shunt current, which is well known in the maximum power tracking literature. This thesis presents a modeling approach to determine and quantify the variations in generation of energy due to intentionally non-flat PV geometries. This will enable the power electronics circuitry to be optimized to harvest maximum energy from PV pixel elements – clusters of PV cells with similar operating characteristics. This thesis systematically compares different geometries with identical two-dimensional projection "footprints" for energy harvest throughout the day. The results show that for the same footprint, a semi-cylindrical surface harvests more energy over a typical day than a flat plate. The modeling approach is then extended to demonstrate that by using non flat geometries for PV panel, the availability of a remotely located stand-alone power system can be increased when compared to a flat panel of same footprint. These results have broad application to a variety of energy scavenging scenarios in which either total energy harvested needs to be maximized or unusual geometries for the PV active surfaces are required, including building-integrated PV. This thesis develops the analysis of the potential energy harvest gain for advanced non-planar PV collectors as a necessary first step towards the design of the power electronics circuits and control algorithms to take advantage of the new opportunities of conformal and non-flat PV collectors.

There is a growing interest in investigating the high order contingency events that may result in large blackouts, which have been a great concern for power grid secure operation. The actual number of high order contingency is too huge for operators and planner to apply a brute-force enumerative analysis. This thesis presents a heuristic searching method based on particle swarm optimization (PSO) and tabu search to select severe high order contingencies. The original PSO algorithm gives an intelligent strategy to search the feasible solution space, but tends to find the best solution only. The proposed method combines the original PSO with tabu search such that a number of top candidates will be identified. This fits the need of high order contingency screening, which can be eventually the input to many other more complicate security analyses. Reordering of branches of test system based on severity of N-1 contingencies is applied as a pre-processing to increase the convergence properties and efficiency of the algorithm. With this reordering approach, many critical high order contingencies are located in a small area in the whole searching space. Therefore, the proposed algorithm tends to concentrate in searching this area such that the number of critical branch combinations searched will increase. Therefore, the speedup ratio is found to increase significantly. The proposed algorithm is tested for N-2 and N-3 contingencies using two test systems modified from the IEEE 118-bus and 30-bus systems. Variation of inertia weight, learning factors, and number of particles is tested and the range of values more suitable for this specific algorithm is suggested. Although illustrated and tested with N-2 and N-3 contingency analysis, the proposed algorithm can be extended to even higher order contingencies but visualization will be difficult because of the increase in the problem dimensions corresponding to the order of contingencies.

High concentrations and fluxes of dissolved organic carbon (DOC) in fluvial systems are associated with the dark brown water colour familiar in many upland, peat-dominated areas and may indicate a depletion of the terrestrial carbon store. The removal of this colour can also be problematic and expensive for water companies as well as affecting the ecological functioning of the water body through factors such as reduced light penetration through the water column. Disturbance resulting from activities such as land use change can also enhance the loss of carbon and this may manifest itself in elevated concentrations and fluxes of DOC from aquatic systems. This thesis describes and explains patterns of change in DOC quantity and quality from the Crosswater, Crosswater of Luce and Tig catchments draining Arecleoch Forest, a peatland in south Ayrshire, Scotland, from 2008 to 2010. This time period incorporates the installation of a 60-turbine wind farm built and operated by Scottish Power Renewables (SPR). Water samples were collected from Arecleoch at different spatial scales ranging from catchments to soil pore water and temporal scales ranging from daily to seasonally. Concentrations of DOC were measured and fluxes estimated at the catchment scale. DOC concentrations from all three catchments exhibited the well-established seasonal pattern with maxima in late August/early September and minima seen in February/March. The Tig catchment experienced the greatest burden of disturbance from the wind farm development and returned the highest DOC concentrations and fluxes. The Crosswater catchment, used as a control site due to its isolation from wind farm activities, had higher DOC concentrations than the Crosswater of Luce throughout the monitoring period possibly due to a greater proportion of forest cover. ii DOC flux ranged from 35.0 g C m-2 yr-1 from the Crosswater of Luce catchment in 2008 to 55.0 g C m-2 yr-1 from the Crosswater in 2009. The Tig catchment was not monitored for the whole period but returned the highest DOC fluxes of the three catchments between January and June 2010 (15.7 g C m-2). These values are considered high for UK peatlands. It is possible to make a tentative estimate of an extra 12 g C m-2 being exported from the Crosswater of Luce in 2009 that may have been a result of wind farm and/or forestry activities in the catchment. At the sub-catchment scale, “hot spots” of high DOC concentrations (up to 113.4 mg L-1) were found during the final survey of headwater streams inside the development area of the wind farm site during construction in August 2010. Further surveys are recommended to assess whether DOC concentrations have decreased since completion of the wind farm. Daily water samples were collected upstream and downstream of turbine 33 during the excavation of the turbine base. DOC concentrations were higher downstream before work began on the turbine base and although the gap between upstream and downstream DOC concentrations increased over the monitoring period, statistical comparisons of these differences before and after the start of excavation work were not significant at the 95 % confidence level. Challenges arose from the practicability of conducting robust research on a construction site and novel approaches to monitoring DOC were developed. Activity scores were used to quantify the effect of peatland disturbance on DOC concentrations at the catchment scale. The results suggest that this approach may have merit but requires comprehensive site records from the developer. The non-linear nature of the individual wind farm development and forestry activities made it impractical to disentangle the impact of each, particularly for forest harvesting. iii Activity scores could, together with other information gathered from site records, be useful to developers as an indicator of the most likely periods for peat disturbance. Knowledge of the differing disturbance potential of the various activities could also provide useful information to feed into the carbon payback calculator. DOC quality was explored using ultraviolet (UV) absorbance, specific UV absorbance (SUVA) and E4/E6 ratios. The latter metric identified changes in the composition of DOC related to disturbance with water samples from areas draining land subject to disturbance having lower E4/E6 ratios indicating a greater degree of humification of the DOC. This research provides one of only three studies to investigate concentrations and fluxes of DOC in water courses draining land subject to disturbance relating to wind farm construction. It is the only study that incorporates a period of time prior to work beginning and takes in the whole of the development phase. In this respect it provides a valuable addition to our understanding of the way in which peatlands respond to land use change and may provide useful tools to assist developers in minimising the impact of their activities on these valuable carbon stores.

Cadmium sulfide (CdS) and cadmium telluride (CdTe) are two leading semiconductor materials used in the fabrication of thin film solar cells of relatively high power conversion efficiency and low manufacturing cost. In this work, CdS/CdTe solar cells with a varying set of processing parameters and device designs were fabricated and characterized for comparative evaluation. Studies were undertaken to elucidate the effects of (i) each step in fabrication and (ii) parameters like thickness, sheet resistance, light absorptivity solution concentration, inert gas pressure etc. Best results were obtained when the thickness of CdS planar film for the window layer was in the range of 150 nm to 200 nm. Also, CdS nanowires were fabricated for use as the window layer in CdS-CdTe solar cells. Their materials characteristics were studied with scanning electron microscopy (SEM) and X-ray Diffraction (XRD). Spectral absorption measurements on the planar CdS films and nanowire CdS layers were performed and results compared. It was established that the nanowire CdS design was superior because its absorption of sunlight was far less than that of planar CdS film, which would lead to enhanced performance in the CdS-CdTe solar cell through higher short circuit current density and higher open circuit voltage. Diode behavior of CdS-CdTe devices on planar CdS and nanowire CdS was analyzed and compared. KEYWORDS: Thin Film Solar Cell, Nanowire, UV Absorption, Open-circuit Voltage, Close Space Sublimation

Portland General Electric has proposed coupling one or more water tanks with two heat pumps in order to perform load-shifting in residential customer heating and cooling applications. By using the water tanks as a thermal storage unit, this project attempts to partially decouple energy consumption from generation to provide peak demand reduction and to better facilitate the integration of variable renewable energy resources. A scoping study was performed to evaluate the potential impact of this project if implemented in single family homes in Portland, Oregon. This study revealed that the system could provide meaningful savings in the cost of electricity to both the customer and utility. Additionally, an optimization algorithm was developed to dictate system operation and to maximize gains to the utility. Evolutionary algorithms were explored in an attempt to increase the effectiveness of the algorithm's search in limited computation time. Ultimately, an evolution strategy was selected as the most suitable based on tests run in winter and spring months. A genetic algorithm was then developed to handle fixed-speed heat pump operation for compatibility with an alpha-system prototype that has been developed by the research team.

In preparation for the influx of renewable energy sources that will be added to the electrical system, flexible and adaptable control schemes are necessary to accommodate the changing infrastructure. Microgrids have been gaining much attention as the main solution to the challenges of distributed and intermittent generation, but due to their low inertia, they need fast-acting control systems in order to maintain stability. Multi-Agent Systems have been proposed as dynamic control and communication frameworks. Decentralized arrangements of agents can provide resiliency and the much-desired “plug and play” behavior. This thesis describes a control system that implements droop control and the diffusion communication scheme without the need of a centralized controller to coordinate the Microgrid agents to maintain the frequency and stable operating conditions of the system. Moreover, the inter-agent communication is unaffected by changing network configurations and can achieve optimal economic dispatch through distributed optimization.

Two key solutions to reduce the greenhouse gas emissions and increase the overall energy efficiency are to maximize the utilization of renewable energy resources (RERs) to generate energy for load consumption and to shift to low or zero emission plug-in electric vehicles (PEVs) for transportation. The present U.S. aging and overburdened power grid infrastructure is under a tremendous pressure to handle the issues involved in penetration of RERS and PEVs. The future power grid should be designed with for the effective utilization of distributed RERs and distributed generations to intelligently respond to varying customer demand including PEVs with high level of security, stability and reliability. This dissertation develops and verifies such a hybrid AC-DC power system. The system will operate in a distributed manner incorporating multiple components in both AC and DC styles and work in both grid-connected and islanding modes. The verification was performed on a laboratory-based hybrid AC-DC power system testbed as hardware/software platform. In this system, RERs emulators together with their maximum power point tracking technology and power electronics converters were designed to test different energy harvesting algorithms. The Energy storage devices including lithium-ion batteries and ultra-capacitors were used to optimize the performance of the hybrid power system. A lithium-ion battery smart energy management system with thermal and state of charge self-balancing was proposed to protect the energy storage system. A grid connected DC PEVs parking garage emulator, with five lithium-ion batteries was also designed with the smart charging functions that can emulate the future vehicle-to-grid (V2G), vehicle-to-vehicle (V2V) and vehicle-to-house (V2H) services. This includes grid voltage and frequency regulations, spinning reserves, micro grid islanding detection and energy resource support. The results show successful integration of the developed techniques for control and energy management of future hybrid AC-DC power systems with high penetration of RERs and PEVs.

In recent years, the security of networked control systems (NCSs) has been an important challenge for many researchers. Although the security schemes for networked control systems have advanced in the past several years, there have been many acknowledged cyber attacks. As a result, this dissertation proposes the use of a novel time-delay switch (TDS) attack by introducing time delays into the dynamics of NCSs. Such an attack has devastating effects on NCSs if prevention techniques and countermeasures are not considered in the design of these systems. To overcome the stability issue caused by TDS attacks, this dissertation proposes a new detector to track TDS attacks in real time. This method relies on an estimator that will estimate and track time delays introduced by a hacker. Once a detector obtains the maximum tolerable time delay of a plant’s optimal controller (for which the plant remains secure and stable), it issues an alarm signal and directs the system to its alarm state. In the alarm state, the plant operates under the control of an emergency controller that can be local or networked to the plant and remains in this stable mode until the networked control system state is restored. In another effort, this dissertation evaluates different control methods to find out which one is more stable when under a TDS attack than others. Also, a novel, simple and effective controller is proposed to thwart TDS attacks on the sensing loop (SL). The modified controller controls the system under a TDS attack. Also, the time-delay estimator will track time delays introduced by a hacker using a modified model reference-based control with an indirect supervisor and a modified least mean square (LMS) minimization technique. Furthermore, here, the demonstration proves that the cryptographic solutions are ineffective in the recovery from TDS attacks. A cryptography-free TDS recovery (CF-TDSR) communication protocol enhancement is introduced to leverage the adaptive channel redundancy techniques, along with a novel state estimator to detect and assist in the recovery of the destabilizing effects of TDS attacks. The conclusion shows how the CF-TDSR ensures the control stability of linear time invariant systems.

For the past several decades, we have experienced the tremendous growth, in both scale and scope, of real-time embedded systems, thanks largely to the advances in IC technology. However, the traditional approach to get performance boost by increasing CPU frequency has been a way of past. Researchers from both industry and academia are turning their focus to multi-core architectures for continuous improvement of computing performance. In our research, we seek to develop efficient scheduling algorithms and analysis methods in the design of real-time embedded systems on multi-core platforms. Real-time systems are the ones with the response time as critical as the logical correctness of computational results. In addition, a variety of stringent constraints such as power/energy consumption, peak temperature and reliability are also imposed to these systems. Therefore, real-time scheduling plays a critical role in design of such computing systems at the system level. We started our research by addressing timing constraints for real-time applications on multi-core platforms, and developed both partitioned and semi-partitioned scheduling algorithms to schedule fixed priority, periodic, and hard real-time tasks on multi-core platforms. Then we extended our research by taking temperature constraints into consideration. We developed a closed-form solution to capture temperature dynamics for a given periodic voltage schedule on multi-core platforms, and also developed three methods to check the feasibility of a periodic real-time schedule under peak temperature constraint. We further extended our research by incorporating the power/energy constraint with thermal awareness into our research problem. We investigated the energy estimation problem on multi-core platforms, and developed a computation efficient method to calculate the energy consumption for a given voltage schedule on a multi-core platform. In this dissertation, we present our research in details and demonstrate the effectiveness and efficiency of our approaches with extensive experimental results.