UC Berkeley

Single-phase power converters enable people to connect any electronic device to the ac grid. As the electricity demand of our world continues to grow, it is crucial to continually research and develop novel power electronic technologies that have improved performance. Specifically, traits of minimal power loss, high volumetric power density, high gravimetric power density, high levels of reliability, and long lifetimes are desired.

In the first part of this thesis, a novel two-stage power converter design is proposed for the application of level-2 electric vehicle on-board charging. For the ac-to-dc rectification stage, a hybrid-switched capacitor converter, which utilizes the ultra-high energy densities of class two ceramic capacitors to minimize the passive component sizing of the converter, is proposed. For the energy buffer stage of the on-board charger, an active buffer topology that minimizes the system's physical volume and weight without compromising efficiency is presented. The active buffer topology in the electric vehicle charger is further investigated, with a novel control and circuit topology introduced that significantly reduces any voltage and current ripple along the dc-link.

In the second part of this thesis, a novel two-stage inverter solution is proposed for a residential microinverter. The inverting stage of the microinverter is divided into two parts: a step-up stage and an inverting stage. Both parts are implemented with hybrid switched-capacitor converter topologies to (1) reduce system volume through leveraging the high energy densities of capacitors and (2) increase system efficiency by utilizing lower voltage switches with high figures of merit and soft-switching techniques. The passive component volume and switching stress of the step-up stage are theoretically analyzed and compared to other converter topologies, showcasing it as a practical converter choice for the microinverter application space. This two-part inverting stage creates a high voltage dc bus where the energy buffer can be placed in the system. This reduces the required buffer capacitance, enabling the engineer to have a broader range of capacitor choices to design a more reliable and energy-dense system.

Overall, this thesis showcases the design and utilization of several hybrid switched-capacitor converters, active buffer topologies, and control in the single-phase application area. Modeling and theoretical analysis techniques of power converter volume and power stress are explained in detail. High-performance hardware prototypes, experimental results, and test setup designs are included.