The objective of the proposed research is to advance the power efficiency of wireless neural stimulating systems in inductively powered implantable medical devices (IMD). Several innovative system- and circuit-level techniques are proposed towards the development of power-management circuits and wireless neural stimulating systems with inductive power transmission to improve the overall stimulation power efficiency. Neural stimulating IMDs have been proven as effective therapies to alleviate neurological diseases, while requiring high power and performance for more efficacious treatments. Therefore, power-management circuits and neural stimulators in IMDs should have high power efficiencies to operate with smaller received power from a larger distance. Neural stimulating systems are also required to have high stimulation efficacy for activating the target tissue with a minimum amount of energy, while ensuring charge-balanced stimulation. These features provide several advantages such as a long battery life in an external power transmitter, extended-range inductive power transfer, efficacious and safe stimulation, and less tissue damage from overheating. The proposed research presents several approaches to design and implement the power-efficient wireless neural stimulating IMDs: 1) optimized power-management circuits for inductively powered biomedical microsystems, 2) a power-efficient neural stimulating system with adaptive supply control, and 3) a wireless switched-capacitor stimulation (SCS) system, which is a combination structure of the power-management circuits and neural stimulator, to maximize both stimulator efficiency (before electrodes) and stimulus efficacy (after electrodes).

Traditional methods of teaching magnetic induction with lab investigations using a battery, wire and compass are best reserved for demonstration purposes to introduce this particular topic. The modern student who sits in a physics course also lives in a world filled with an increasing number of small portable devices that will eventually be charged wirelessly using some form of magnetic induction. The topic of magnetic induction needs to be placed in the modern context it deserves since the future of transmitting power will eventually be through wireless means. The wireless power transfer kit described in this report is designed to improve student understanding and the application of magnetic induction in an engaging, relevant manner. / text

The wireless transfer of power is the enabling technology for realizing a true internet-of-things. Broad sensor networks capable of monitoring environmental pollutants, health-related biological data, and building utility usage are just a small fraction of the myriad of applications which are part of an ever evolving ubiquitous lifestyle. Realizing these systems requires a means of powering their electronics sans batteries. Removing the batteries from the billions or trillions of these envisioned devices not only reduces their size and lowers their cost, but also avoids an ecological catastrophe. Increasing the efficiency of microwave-to-DC power conversion in energy-harvesting circuits extends the range and reliability of passive sensor networks. Multi-frequency waveforms are one technique that assists in overcoming the energy-harvesting circuit diode voltage threshold which limit the energy-conversion efficiency at low RF input powers typically encountered by sensors at the fringe of their coverage area. This thesis discusses a systematic optimization approach to the design of energy-conversion circuits along with multi-frequency waveform excitation. Using this methodology, a low-power 5.8 GHz rectenna showed an output power improvement of over 20 dB at -20 dBm input power using a 3-POW (power-optimized waveform) compared to continuous waveforms (CW). The resultant efficiency is the highest reported efficiency for low-power 5.8 GHz energy harvesters. Additionally, new theoretical models help to predict the maximum possible range of the next generation of passive electronics based upon trends in the semiconductor industry. These models predict improvements in diode turn-on power of over 20 dB using modern Schottky diodes. This improvement in turn-on power includes an improvement in output power of hundreds of dB when compared to CW.

abstract: After a power system blackout, system restoration is the most important task for the operators. Most power systems rely on an off&ndashline; restoration plan and the experience of operators to select scenarios for the black start path. Using an off&ndashline; designed restoration plan based on past experience may not be the most reliable approach under changing network configurations and loading levels. Hence, an objective restoration path selection procedure, including the option to check constraints, may be more responsive in providing directed guidance to the operators to identify the optimal transmission path to deliver power to other power plants or to pick up load as needed. After the system is subjected to a blackout, parallel restoration is an efficient way to speed up the restoration process. For a large scale power system, this system sectionalizing problem is quite complicated when considering black&ndashstart; constraints, generation/load balance constraints and voltage constraints. This dissertation presents an ordered binary decision diagram (OBDD) &ndashbased; system sectionalizing method, by which the splitting points can be quickly found. The simulation results on the IEEE 39 and 118&ndashbus; system show that the method can successfully split the system into subsystems satisfying black&ndashstart; constraints, generation/load balance constraints and voltage constraints. A power transfer distribution factor (PTDF)&ndashbased; approach will be described in this dissertation to check constraints while restoring the system. Two types of restoration performance indices are utilized considering all possible restoration paths, which are then ranked according to their expected performance characteristics as reflected by the restoration performance index. PTDFs and weighting factors are used to determine the ordered list of restoration paths, which can enable the load to be picked up by lightly loaded lines or relieve stress on heavily loaded lines. A transmission path agent can then be formulated by performing the automatic path selection under different system operating conditions. The proposed restoration strategy is tested on the IEEE&ndash39; bus system and on the Western region of the Entergy system. The testing results reveal that the proposed strategy can be used in real time. / Dissertation/Thesis / Ph.D. Electrical Engineering 2010

A transferência de energia sem fio (WPT) rege um importante papel no carregamento de aparelhos remotos. Em um acoplamento indutivo ressonante há várias topologias de sistemas WPT que podem ser implementados para realizar a transferência de energia. Neste trabalho é utilizado uma topologia que utiliza quatro capacitores de compensação para realizar o ajuste da potência entregue a carga, onde estes capacitores são calculados através das fixações dos demais parâmetros do circuito elétrico. Quando o sistema WPT é projetado, uma distância fixa entre as bobinas é almejada, todavia há incertezas e movimentos que podem provocar a alteração desta distância. Há várias técnicas na literatura que buscam realizar a sintonia do acoplamento indutivo para compensar estes desalinhamentos gerado entre as bobinas. Este trabalho apresenta um método multivariável para maximização da potência entregue a carga em um sistema de transferência sem fio. O método proposto utiliza os conceitos de um capacitor variável e a variação de frequência a fim de variar a potência entregue a carga. Os resultados experimentais obtidos para os fatores de acoplamento magnético k > 0;3 mostraram que controlando a frequência e uma capacitância da rede de compensação o desempenho do sistema é melhor que os casos onde apenas uma dessas variáveis é controlada. / Wireless power transfer (WPT) plays an important rule in charging remote devices. In a resonant inductive coupling there are several topologies of WPT systems that can be implemented to perform the energy transfer. In this work, a topology is used that uses four capacitors of compensation to realize the adjustment of the power delivered to load, where these capacitors are calculated through the xations of the other parameters of the electric circuit. When the WPT system is designed, a xed distance between coils is desired, however there are uncertainties and movements that may cause this distance to change. There are several techniques in the literature that seek to realize the tuning of the inductive coupling to compensate for these misalignments generated between the coils. This work presents a multivariable method to maximize the power delivered to the load in a wireless transfer system. The proposed method uses the concepts of a variable capacitor and the frequency variation in order to vary the power delivered to the load. The experimental results obtained for the magnetic coupling factors k > 0:3 showed that controlling the frequency and capacitance of the compensation network system performance is better than the cases where only one of these variables is controlled.

The wireless sensor network (WSN) is increasingly used in many areas nowadays. It can be applied to provide the solutions to environmental problems, help increasing security and safety systems, and make the detection of the problems more efficient, e.g. the earthquake or tidal wave, which will harmful to humans. The WNS is durable and resistant to all types of terrain and climate, but while the WSN system is more and more widespread, one of the obstacles hindering the growth of this technology and the demand for WSN applications is the limited battery lifespan. Consequently, there is a significant requirement for techniques for prolonging the battery’s lifespan. Therefore, one potential solution is to use alternative energy sources combined with the sensor nodes in WSN, specifically energy harvesting from existing environmental sources. This research project reviews the characteristics of each kind of energy harvesting, understanding the various energy sources (solar energy, vibration energy and wind power), including wireless power transfer (WPT) by using electromagnetic (EM) radiation energy transfer or RF radio-frequency emission and magnetic coupled energy transfer. They are adopted for extending node’s life in the WSN, based on published information. Then it compares these diverse alternative energy methods and identifies for the most suitable energy harvesting method for application to wireless sensor nodes in order to prolong the lifespan of the battery. The major findings from the researcher include that wireless power transfer energy harvesting (WPT) using the magnetic field is the most appropriate tool for extending the lifespan of the WSN system. In addition, the author also designed an experiment to test this alternative energy, achieving by modelling the wireless power transfer with four coils. From the experimental results, it can be seen that the WPT technique using energy harvesting with magnetic inductive source can be applied to prolong the lifespan of the WSN system.

A transferência de energia sem fio (WPT) rege um importante papel no carregamento de aparelhos remotos. Em um acoplamento indutivo ressonante há várias topologias de sistemas WPT que podem ser implementados para realizar a transferência de energia. Neste trabalho é utilizado uma topologia que utiliza quatro capacitores de compensação para realizar o ajuste da potência entregue a carga, onde estes capacitores são calculados através das fixações dos demais parâmetros do circuito elétrico. Quando o sistema WPT é projetado, uma distância fixa entre as bobinas é almejada, todavia há incertezas e movimentos que podem provocar a alteração desta distância. Há várias técnicas na literatura que buscam realizar a sintonia do acoplamento indutivo para compensar estes desalinhamentos gerado entre as bobinas. Este trabalho apresenta um método multivariável para maximização da potência entregue a carga em um sistema de transferência sem fio. O método proposto utiliza os conceitos de um capacitor variável e a variação de frequência a fim de variar a potência entregue a carga. Os resultados experimentais obtidos para os fatores de acoplamento magnético k > 0;3 mostraram que controlando a frequência e uma capacitância da rede de compensação o desempenho do sistema é melhor que os casos onde apenas uma dessas variáveis é controlada. / Wireless power transfer (WPT) plays an important rule in charging remote devices. In a resonant inductive coupling there are several topologies of WPT systems that can be implemented to perform the energy transfer. In this work, a topology is used that uses four capacitors of compensation to realize the adjustment of the power delivered to load, where these capacitors are calculated through the xations of the other parameters of the electric circuit. When the WPT system is designed, a xed distance between coils is desired, however there are uncertainties and movements that may cause this distance to change. There are several techniques in the literature that seek to realize the tuning of the inductive coupling to compensate for these misalignments generated between the coils. This work presents a multivariable method to maximize the power delivered to the load in a wireless transfer system. The proposed method uses the concepts of a variable capacitor and the frequency variation in order to vary the power delivered to the load. The experimental results obtained for the magnetic coupling factors k > 0:3 showed that controlling the frequency and capacitance of the compensation network system performance is better than the cases where only one of these variables is controlled.

abstract: Electric power systems are facing great challenges from environmental regulations, changes in demand due to new technologies like electric vehicle, as well as the integration of various renewable energy sources. These factors taken together require the development of new tools to help make policy and investment decisions for the future power grid. The requirements of a network equivalent to be used in such planning tools are very different from those assumed in the development of traditional equivalencing procedures. This dissertation is focused on the development, implementation and verification of two network equivalencing approaches on large power systems, such as the Eastern Interconnection. Traditional Ward-type equivalences are a class of equivalencing approaches but this class has some significant drawbacks. It is well known that Ward-type equivalents "smear" the injections of external generators over a large number of boundary buses. For newer long-term investment applications that take into account such things as greenhouse gas (GHG) regulations and generator availability, it is computationally impractical to model fractions of generators located at many buses. A modified-Ward equivalent is proposed to address this limitation such that the external generators are moved wholesale to some internal buses based on electrical distance. This proposed equivalencing procedure is designed so that the retained-line power flows in the equivalent match those in the unreduced (full) model exactly. During the reduction process, accommodations for special system elements are addressed, including static VAr compensators (SVCs), high voltage dc (HVDC) transmission lines, and phase angle regulators. Another network equivalencing approach based on the dc power flow assumptions and the power transfer distribution factors (PTDFs) is proposed. This method, rather than eliminate buses via Gauss-reduction, aggregates buses on a zonal basis. The bus aggregation approach proposed here is superior to the existing bus aggregation methods in that a) under the base case, the equivalent-system inter-zonal power flows exactly match those calculated using the full-network-model b) as the operating conditions change, errors in line flows are reduced using the proposed bus clustering algorithm c) this method is computationally more efficient than other bus aggregation methods proposed heretofore. A critical step in achieving accuracy with a bus aggregation approach is selecting which buses to cluster together and how many clusters are needed. Clustering in this context refers to the process of partitioning a network into subsets of buses. An efficient network clustering method is proposed based on the PTDFs and the data mining techniques. This method is applied to the EI topology using the "Saguaro" supercomputer at ASU, a resource with sufficient memory and computational capability for handling this 60,000-bus and 80,000-branch system. The network equivalents generated by the proposed approaches are verified and tested for different operating conditions and promising results have been observed. / Dissertation/Thesis / Ph.D. Electrical Engineering 2012

abstract: In the United States, especially in metropolitan areas, transmission infra-structure is congested due to a combination of increasing load demands, declining investment, and aging facilities. It is anticipated that significant investments will be required for new construction and upgrades in order to serve load demands. This thesis explores higher phase order systems, specifically, six-phase, as a means of increasing power transfer capability, and provides a comparison with conventional three-phase double circuit transmission lines. In this thesis, the line parameters, electric and magnetic fields, and right of way are the criteria for comparing six-phase and three-phase double circuit lines. The calculations of the criteria were achieved by a program developed using MATLAB. This thesis also presents fault analysis and recommends suitable pro-tection for six-phase transmission lines. This calculation was performed on 4-bus, 9-bus, and 118-bus systems from Powerworld® sample cases. The simulations were performed using Powerworld® and PSCAD®. Line parameters calculations performed in this thesis show that line imped-ances in six-phase lines have a slight difference, compared to three-phase double circuit line. The shunt capacitance of compacted six phase line is twice of the value in the three-phase double circuit line. As a consequence, the compacted six-phase line provides higher surge impedance loadings. The electric and magnetic fields calculations show that, ground level electric fields of the six-phase lines decline more rapidly as the distance from center of the lines increase. The six-phase lines have a better performance on ground level magnetic field. Based on the electric and magnetic field results, right of way re-quirements for the six-phase lines and three-phase double circuit line were calcu-lated. The calculation results of right of way show that six-phase lines provide higher power transfer capability with a given right of way. Results from transmission line fault analysis, and protection study show that, fault types and protection system in six-phase lines are more complicated, com-pared to three-phase double circuit line. To clarify the concern about six-phase line protection, a six-phase line protection system was designed. Appropriate pro-tection settings were determined for a six-phase line in the 4-bus system. / Dissertation/Thesis / M.S. Electrical Engineering 2012

abstract: The worldwide demand for electric energy is slated to increase by 80% between the years 1990 and 2040. In order to satisfy this increase in load, many new generators and transmission lines are planned. Implementations of various plans that can augment existing infrastructure have been hindered due to environmental constraints, public opposition and difficulties in obtaining right-of-way. As a result, stress on the present electrical infrastructure has increased, resulting in congestion within the system. The aim of this research is to analyze three techniques that could improve the power transfer capability of the present electric grid. These include line compaction, use of high temperature low sag conductors and high phase order systems. The above methods were selected as they could be readily employed without the need for additional right-of-way. Results from the line compaction tests indicate that line compaction up to 30% is possible and this increases the power transfer capability up to 53%. Additional advantages of employing line compaction are the reduction in electric and magnetic fields, increase in system stability and better voltage regulation. High temperature low sag conductors that were applied on thermally limited lines were seen to increase the power transfer capability. However, a disadvantage of this technique was that the second most congested line, limits the power transfer capability of the system. High phase (six phase) order system was noted to have several advantages over three phase system such as lower voltage requirement to transfer equal amount of power and lower electric and magnetic field across the right of way. An IEEE 9 and 118 bus test system were used to evaluate the above mentioned techniques. / Dissertation/Thesis / M.S. Electrical Engineering 2012