Single-phase energy systems are becoming increasingly common due to the rise of resi-dential scale (∼3kW) renewable energy in the US. Integrating storage, sources, and loads poses many challenges associated with power balancing and being resilient to power supply variations or interruptions. A multi-port hub for integrating a single-phase utility connection, DC battery storage, DC photovoltaic (PV) generation, and critical customer loads is presented in this dissertation. At the core of the system is an electric machine that functions as a multiport rotating transformer, providing voltage conversion, galvanic isolation, 120 Hz ripple energy balancing for single-phase ports, and hold-up energy by use of intrinsic stored kinetic energy in rotation. The energy stored in rotation of the machine is orders of magnitude greater than that available in the capacitor bank often used in static systems and has no associated power versus energy trade-off. A transverse flux topology was chosen for the rotating transformer due to the topology’s true torque scaling with respect to pole pairs and its simple winding configuration. The transverse flux machine was chosen to be have a U-core topology for its relative ease of manufacturing. A convex optimization design method was used to determine the machine physical dimensions and operating speed. The number of stator poles and magnets was specifically chosen to minimize cogging. A prototype system has been constructed that demonstrates all the functionalities of the rotating transformer. The prototype system validates the multiport system with rotating transformer as an effective and cost efficient method for the integration of typical residential PV components. This dissertation covers the design and implementation of the rotating transformer, its mechanical suspension, the system control, and the system power electronic converters.

Mobile, wearable, and internet of things (IOT) electronic systems are typically powered by a single cell Lithium-Ion (Li-ion) battery. Increasing demand for battery life and the constraint of the overall platform size impose an emerging desire for an efficient and com- pact power conversion stage that can directly deliver power from the battery, which ranges from 3.2V to 4.2V, to the supplies of application/communication processors in the range of 1V. The conventional buck converter, dimensioned for the 3.2-4.2 V input range, requires switches that are not typically available in standard sub-micron CMOS technology. Efficient implementation of the conventional buck converter has required a rather bulky off-chip inductor. The switched capacitor (SC) converter, though promising for a fully integrated solution, is inefficient at voltage regulation and is limited in capacitor energy utilization. In addition, with the SC converter, to cover the input range of a Li-ion battery to the processor supply voltage, topology reconfiguration has to be adopted. This additional functionality requires some additional design and implementation complexity.

Given the limitations of either pure inductive or pure capacitive converter topologies, various hybridized power conversion architectures have been proposed recently. The hybrid approaches leverage minimum magnetic components to mitigate the intrinsic charge sharing loss in the standard SC operation while still maintaining a better switch utilization inherent in some SC topologies. This thesis introduces a hybrid dc-dc converter topology named stacked resonant switched capacitor (Stack-ResSC) that eliminates charge sharing losses with a small inductor. Consequently, capacitor energy utilization is improved and lossless voltage regulation is enabled. Since the necessary inductance is small, the magnetic component can still be tightly integrated within the package with a PCB trace or a bondwire. The proposed topology can also adapt to any N-to-1 conversion ratio, which extends the topology for wider applications. Harmonic averaging is used in this thesis to develop the large and small signal model of the converter. A tight load line regulation can be effected with the designed controller according to the developed small signal model.

In addition to the Stack-ResSC, this thesis also introduces the stacked dual active bridge (Stack-DAB) as a derivative of the Stack-ResSC. An integrated circuit example is demonstrated with a nominal 3:1 conversion ratio. It supports a 3.2V-4.2V input voltage with a continuous output regulation of 0.8V-1.5V. The circuit delivers 83.4% efficiency at a power density of 0.46 W/mm2. The converter also shows superior transient response compared to state-of-art integrated implementation. This work demonstrates the advantage of the pro- posed hybrid approach in terms of tight integration and voltage regulation. The scope of the resonant switched capacitor based DC-DC converter is thus further extended.

Addressing the challenge of climate change requires the large-scale development of significant renewable energy generation, but also requires these intermittent energy sources to be balanced by energy storage or demand management to maintain a reliable electric grid. In addition, a centralized generation paradigm fails to capture and utilize thermal energy for combined heat and power, abandoning a large portion of the available value from the primary energy source. A solar thermal electric system utilizing Stirling engines for energy conversion solves both of these shortcomings and has the potential to be a key technology for renewable energy generation. The ability to store thermal energy cheaply and easily allows the reliable generation of output power even during absences of solar input, and operating as distributed generation allows the output thermal stream to be captured for local heating applications. Such a system also can achieve relatively high conversion efficiencies, is fabricated using common and benign materials, and can utilize alternate sources of primary energy in an extended absence of solar input.

This dissertation discusses the design, fabrication, and testing of a Stirling engine as the key component in a solar thermal electric system. In particular, the design addresses the low temperature differential that is attainable with distributed solar with low concentration ratios and is designed for low cost to be competitive in the energy space. The dissertation covers design, fabrication, and testing of a 2.5 kW Stirling Engine with a predicted thermal-to-mechanical efficiency of 20%, representing 60% of Carnot efficiency, operating between 180°C and 30°C. The design process and choices of the core components of the engine are discussed in detail, including heat exchangers, regenerator, pistons, and motor/alternator, and the process for modeling, simulation, and optimization in designing the engine. Finally, the dissertation covers the assembly and experimental testing that validates the design in terms of heat exchanger performance, losses, kinematics, and cycle work.

This dissertation explores circuit, control, and optimization techniques for power electronics with the objective of enabling high performance electric networks for a variety of important applications. The motivation for this work is driven in part by societal-scale trends towards systems that are increasingly dominated by power electronics, including applications such as renewable energy integration, vehicle electrification, power management for mobile devices, and data center power delivery. A key approach demonstrated in this dissertation is the design of switching power converter circuits that naturally coordinate with larger networks in order to achieve system-level benefits, whether with respect to efficiency, power quality, or reliability. A central goal of this work is to have this coordination realized in a decentralized or autonomous fashion, such that scalability, modularity, and resiliency can be achieved inherently. In the first part of this dissertation, we explore techniques for improving the power quality of electric networks with high penetrations of switching power converters, in particular, techniques that can minimize aggregate power converter harmonics in an optimal sense while also eliminating the need for communication between distributed converters. In the second part of this dissertation, we explore methods for improving the reliability and fault tolerance of such networks, in particular, model- and estimation-based strategies that transform power converters into active probes that can detect, identify, and diagnose faults in real-time. Together, these contributions demonstrate how power electronics can be designed and collectively controlled and optimized to enable highly efficient, robust, and resilient electric networks.

High brightness LEDs have become a mainstream lighting technology due to their efficiency, life span, and environmental benefits. As such, the lighting industry values LED drivers with low cost, small form factor, and long life span. Additional specifications that define a high quality LED driver are high efficiency, high power factor, wide-range dimming, minimal flicker, and a galvanically isolated output. The flyback LED driver is a popular topology that satisfies all these specifications, but it requires a bulky and costly flyback transformer. In addition, its passive methods for cancelling AC power ripple require electrolytic capacitors, which have been known to have life span issues. This dissertation details the design, construction, and verification of a novel LED driver that satisfies all the specifications. In addition, it does not require a flyback transformer or electrolytic capacitors, thus marking an improvement over the flyback driver on size, cost, and life span.

This dissertation presents an integrated circuit (IC) LED driver, which features a pair of generalized multilevel converters that are controlled via sigma-delta modulation. The first is a multilevel rectifier responsible for power factor correction (PFC) and dimming. The PFC rectifier employs a second order sigma-delta loop to precisely control the input current harmonics and amplitude. The second is a bidirectional multilevel inverter used to cancel AC power ripple from the DC bus. This ripple-cancellation module transfers energy to and from a storage capacitor. It uses a first order sigma-delta loop with a preprogrammed waveform to swing the storage capacitor voltage. The system also contains an output stage that powers the LEDs with DC and provides for galvanic isolation. The output stage consists of an H-bridge stack that connects to the output through a small toroid transformer.

The IC LED driver was simulated and prototyped on an ABCD silicon test chip. Testing and verification indicates functional performance for all the modules in the LED driver. The driver exhibits moderate efficiency at half voltage. Although the part was only testable to half voltage, loss models predict that its efficiency would be much higher at full voltage. The driver also meets specifications on the line current harmonics and ripple cancellation.

This dissertation introduces multilevel circuit techniques to the IC and LED research space. The prototype's functional performance indicates that integrated multilevel converters are a viable topology for lighting and other similar applications.

This final reports the fault analysis of precision docking system and safety design of the safety critical elements for precision docking system. The report includes three Parts, including:

Part I provides a description of the Precision Docking System and reports analysis for fault diagnosis and safety design of automated steering controller and Electronic Control Unit (ECU) for steering actuator. It also reports a demonstration PATH conducted during the National Intelligent Vehicle Initiative demonstration organized by the US Department of Transportation Joint Program Office.

Part II report an analysis and design for a reliable direct drive for the steering wheel column of buses.

Part III reports power system reliability.

The report below is the Part II report: A Reliable Direct Drive for the Steering Wheel Column of Buses. It evaluates the feasibility of using a direct drive for the steering wheel column of buses and heavy trucks. Permanent magnet technology is proposed for the motor design, due to its proven advantages for medium- to low-power servo applications. A redundant set of windings is introduced in the motor, together with a fault-detection/isolation system, to provide fault tolerance and increase the actuator's reliability.The report is organized as follows: first, the design of the motor is described. Next, the power electronics and control strategy are analyzed. Finally, fault-detection and fault-isolation techniques are presented.

This final reports the fault analysis of precision docking system and safety design of the safety critical elements for precision docking system. The report includes three Parts, including:

Part I provides a description of the Precision Docking System and reports analysis for fault diagnosis and safety design of automated steering controller and Electronic Control Unit (ECU) for steering actuator. It also reports a demonstration PATH conducted during the National Intelligent Vehicle Initiative demonstration organized by the US Department of Transportation Joint Program Office.

Part II report an analysis and design for a reliable direct drive for the steering wheel column of buses.

Part III reports power system reliability.

The report below is the Part III report: Power Reliability.

Due to the massive increase in renewable energy deployment around the world, the distribution level of electric power grids has more active devices than ever before. Many distributed energy resources (DERs) were installed to output the maximum amount of power available without consideration of the grid's status or the presence of other devices. As a result, grid operators can encounter power quality issues, especially voltage volatility, which can stall the adoption of more renewable energy devices. Traditional grid devices that are intended to maintain distribution grid power quality may be insufficient to address today's challenges. While academic literature has proposed many types of approaches to device control, it can favor approaches that are optimization-based at the expense of being impractical for deployment on real distribution grids.

This thesis argues for the analysis of simple, flexible device controls to improve power quality and power delivery. We take a dynamical systems perspective, which provides transparency into the underlying device interactions. This perspective allows us to develop intuition for device interactions and develop safety guarantees that prevent dangerous behavior. For the important problem of computing DER power injections, we take a holistic approach to controller design, where control parameters and DER siting are analyzed to achieve improved voltage stability. Furthermore, this design is achieved without imposing restrictions on the DER communication network. Next, we consider device design under two important modeling scenarios. First, we consider the case of abnormal voltage events, in which there is a strict time limit during which DERs must recover the voltage before devices must disconnect. Then we model the interaction between inverter-based DERs and load-tap changer devices, to determine parameter relationships that guarantee against voltage oscillations. We conclude with a discussion of future work and as synthesize important principles for device control in power systems.

The traditional inductor-based buck converter has been the default design for switched-mode voltage regulators for decades. Switched capacitor (SC) dc-dc converters, on the other hand, have traditionally been used in low power (<10mW) and low conversion ratio (<4:1) applications where neither regulation nor efficiency is critical. This work encompasses the complete successful design, fabrication, and test of a CMOS based switched capacitor dc-dc converter, addressing the ubiquitous 12 V to 1.5 V board-mounted point-of-load application, which the buck converter has dominated. In particular, the circuit developed in this work attains higher efficiency (92% peak, and >80% over a load range of 5 mA to 1 A) than surveyed competitive buck converters, while requiring less board area and less costly passive components. The topology and controller enable a wide input range of 7.5 V to 13.5 V. Controls based on feedback and feedforward provide tight regulation under worst case line and load step conditions. This work shows that the SC converter can outperform the buck converter, and thus the scope of SC converter application can and should be expanded.