abstract: The government support towards green energy sources for the better future of the planet has changed the perspective of the people towards the usage of green energy. Among renewables, solar is one of the important and easily accessible resources to convert energy from the sun directly into electricity and this system has gained fame since the past three decades. SRP has set up a 6.36 kW PV and 19.4 kWh battery system on the rooftop of Engineering Research Center (ERC). The system is grid-connected and ASU (Arizona State University) has developed two load banks with a minimum step of 72 watts to simulate different residential load profiles and perform other research objectives. A customer benefit analysis is performed for residential customers with photovoltaic (PV) systems and energy storage particularly in the state of Arizona. By optimizing the use of energy storage device, the algorithm aims at maximizing the profit and minimizing utility bills in accordance with the demand charge algorithm of the local utility. This part of the research has been published as a conference paper in IEEE PES General Meeting 2017. A transient test is performed on the PV-battery during the on-grid mode and the off-grid mode to study the system behaviour during the transients. An algorithm is developed by the ASU research team to minimize the demand charge tariff for the residential customers. A statistical analysis is performed on the data collected from the system using a MATLAB algorithm. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

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This thesis explores design challenges and promising solutions for temperature sensors for high temperature environments such as combustion turbines. To survive this high temperature environment of over 1000 °C the sensors are required to be robust in their electrical and mechanical properties. Wire connections for these high temperature environments are a complex problem due to the physical limitations of most materials at those high temperatures. In this thesis, robust ceramic sensors based on microwave resonators are demonstrated for high temperature environments, with some studies into optimizing the techniques used to measure them, as well as the distance at which their responses can still be measured. Two types of temperature sensors are realized using rectangular reflective patches with different dielectric substrates. The sensors are realized with either alumina substrate or yttria-stabilized zirconia (YSZ), both of which have temperature dependent dielectric constants. The temperature is wirelessly detected by measuring the resonant frequency of the reflective patch. The reflective patch sensor works simultaneously as a resonator and a radiative element. The sensors were tested up to 800 °C. In these high temperature environments, it is important to be able to interrogate the sensor from a distance safe for the interrogating antenna, for this reason, the sensors must be designed with a high enough Q factor that their responses can be measured up to at least 2 inches of distance away from the interrogating antenna. While exploring designs of temperature sensors, a few measurement techniques on the vector network analyzer are studied to optimize the identification of the resonant frequency of the reflective patches. These measurements include the start and stop time of the time domain gating window, the start and stop frequency of the frequency span of the interrogating signal, and the gain/size of the interrogating horn antenna.

An increase in the demand for electrical power and tremendous growth of renewable energy sources has been seen in the last decade, which resulted in designing the wind turbine system components for higher load point performance, resulting in higher annual energy production. Cost optimization, weight reduction, and lower non-conformance cost are some of the expectations that the wind turbine needs to meet in the present stringent market condition. Overheating of the wind turbine system components is one of the primary challenges to overcome when the system operates at a higher load point. The overheating issue of the wind turbine generator system is the subject of this research. Windings and bearings are two primary components susceptible to failure in the wind turbine generator. Overheating accelerates the generator windings and bearings failure. A detailed investigation has been done on the air to the air-cooled generator in a test wind turbine in Europe. A unique cooling design has been proposed. The temperature rise in the test generator with a new cooling design found to be substantially lower, and the signification temperature dropped has been measured in winding and bearing temperature, which allows the machine to operate at the higher load point. All the risks and mitigation associated with the proposed design are thoroughly evaluated. The research presents the issue of generator winding strand tilt with a system approach and explains how the system performance can be evaluated with respect to a component level performance. The issue of measuring strand tilt is presented in a case study. Selecting a correct insulation system for the generator winding for the wind turbine application has been recommended to IEC/IEEE. The research presents a unique finding in the difference in drive and non-drive end bearing temperature. A proposal has been made to update IEC/IEEE standard to mitigate this potential problem. Higher availability of wind turbines lead to higher annual energy production from the turbine, this research contributes to increasing the availability of the wind turbine by addressing and proposing the overheating solution of the wind turbine generator.

Recent emergence of battery technology has resulted in increased interest in design of an integrated portable photovoltaic panel with a battery pack for stand-alone and grid-connected system. Lithium-ion batteries appear to be an optimal candidate due to high energy density, long cycling life, deep discharge ability, low self-discharge and different shapes such as cylindrical or prismatic styles to obtain an integrated design. The physical integration of the PV panel with batteries must feature scalability, adaptability and easy installation. These requirements validate the microinverter as desired power electronic solution for the proposed system. To eliminate the issues of the PV power fluctuation, various microinverter topologies have been proposed in this dissertation which integrate a battery as a storage element with PV panel. The integrated battery is dedicated to eliminating the intermittent and the excessive power concerns in PV system. This allows the PV, local energy storage, and a smart integrated micro-inverter to be consolidated and mounted as one module on the back of the PV panel. The efficient energy management system will provide stable predictable power in grid-connected applications. The topologies feature either five or six power flow scenarios based on the power generated by PV module, the grid requirement and the battery state of charge. The power flow scenarios can be as follows: 1) Only PV module providing power to the grid. 2) Only battery providing power to the grid. 3) PV module providing power to the grid while charging the battery. 4) Both PV and battery providing power to the grid. 5) PV module charging the battery. 6) The grid charging the battery. All power flow scenarios are achieved with single-stage conversion between three ports with faster response, low component counts, compact size and centralized control to manage the power among the ports.

With the demand increase for electricity, the ever-increasing awareness of environmental issues, coupled with rolling blackouts, the role of renewable energy generation is increasing along with the thirst for electricity and awareness of environmental issues. This dissertation proposes the design and implementation of PV-firming and optimization algorithms for three-port microinverters. Novel strategies are proposed in Chapters 3 and 4 for harvesting stable solar power in spite of intermittent solar irradiance. PV firming is implemented using a panel-level three-port grid-tied PV microinverter system instead of the traditional high-power energy storage and management system at the utility scale. The microinverter system consists of a flyback converter and an H-bridge inverter/rectifier, with a battery connected to the DC-link. The key to these strategies lies in using static and dynamic algorithms to generate a smooth PV reference power. The outcomes are applied to various control methods to charge/discharge the battery so that a stable power generation profile is obtained. In addition, frequency-based optimization for the inverter stage is presented. One of the design parameters of grid-tied single-phase H-bridge sinusoidal pulse-width modulation (SPWM) microinverters is switching frequency. The selection of the switching frequency is a tradeoff between improving the power quality by reducing the total harmonic distortion (THD), and improving the efficiency by reducing the switching loss. In Chapter 5, two algorithms are proposed for optimizing both the power quality and the efficiency of the microinverter. They do this by using a frequency tracking technique that requires no hardware modification. The first algorithm tracks the optimal switching frequency for maximum efficiency at a given THD value. The second maximizes the power quality of the H-bridge micro-inverter by tracking the switching frequency that corresponds to the minimum THD. Real-time PV intermittency and usable capacity data were evaluated and then further analyzed in MATLAB/SIMULINK to validate the PV firming control. The proposed PV firming and optimization algorithms were experimentally verified, and the results evaluated. Finally, Chapter 6 provides a summary of key conclusions and future work to optimize the presented topology and algorithms.

The extensive use of Integrated Circuits (ICs) means complex working conditions for these tiny chips. To guarantee the ICs could work properly in various environments, some special protection strategies are required to improve the reliability of system. From all the possible reliability issues, the electrostatics discharge (ESD) might be the most common one. The peak current of electrostatics can be as high as tens of amperes and the peak voltage can be over thousand voltages. In contrast, the size of semiconductor device fabricated is continuing to scale down, making it even more vulnerable to high level overstress and current surge induced by ESD event. To protect the on-chip semiconductor from damage, some extra "clamp cells" are put together to consist a network. The network can redirect the superfluous current through the ESD network and clamp the voltage to a low level. In this dissertation, one design concept is introduced that uses the combination of some basic ESD devices to meet different requirements first, and then tries to establish parasitic current path among these devices to further increase the current handling capability. Some design cases are addressed to demonstrate this design concept is valid and efficient: 1. A combination of silicon-controlled-rectifier (SCR) and diode cluster is implemented to resolve the overshoot issue under fast ESD event. 2. A new SCR structure is introduced, which can be used as "padding" device to increase the clamping voltage without affecting other parameters. Based on this "padding" device, two design cases are introduced. 3. A controllable SCR clamp structure is presented, which has high current handling capability and can be controlled with by small signal. All these structures and topologies described in this dissertation are compatible with most of popular semiconductor fabrication process.

The energy market is on the verge of a paradigm shift as the emergence of renewable energy sources over traditional fossil fuel based energy supply has started to become cost competitive and viable. Unfortunately, most of the attractive renewable sources come with inherent challenges such as: intermittency and unreliability. This is problematic for today's stable, day ahead market based power system. Fortunately, it is well established that energy storage devices can compensate for renewable sources shortcomings. This makes the integration of energy storage with the renewable energy sources, one of the biggest challenges of modern distributed generation solution. This work discusses, the current state of the art of power conversion systems that integrate photovoltaic and battery energy storage systems. It is established that the control of bidirectional power flow to the energy storage device can be improved by optimizing its modulation and control. Traditional multistage conversion systems offers the required power delivery options, but suffers from a rigid power management system, reduced efficiency and increased cost. To solve this problem, a novel three port converter was developed which allows bidirectional power flow between the battery and the load, and unidirectional power flow from the photovoltaic port. The individual two-port portions of the three port converter were optimized in terms of modulation scheme. This leads to optimization of the proposed converter, for all possible power flow modes. In the second stage of the project, the three port converter was improved both in terms of cost and efficiency by proposing an improved topology. The improved three port converter has reduced functionality but is a perfect fit for the targeted microinverter application. The overall control system was designed to achieve improved reference tracking for power management and output AC voltage control. The bidirectional converter and both the proposed three port converters were analyzed theoretically. Finally, experimental prototypes were built to verify their performance.