Design Optimization & Control of High Power Density Converters using Wide Band Gap Devices

Abstract

In this dissertation various converter topologies are proposed and evaluated in view of the state of art solutions to optimize power density and converter efficiency for several applications including photovoltaic solar energy harvesting, energy storage, wind power generation, and medium voltage adjustable speed drives.

The first part of the dissertation, presents a comparison between mitigation techniques for double line frequency ripples in single phase micro-inverters based on Wide Band Gap devices. A topology based on an auxiliary DC-AC stage is adopted based on optimizing both power density and efficiency to achieve the pressing needs for the next generation of micro-inverters as announced by Google’s Little Box Challenge. An accurate yet simple control algorithm is proposed that provides a ripple-free DC current. Experimental results demonstrate the effectiveness of the presented topology and control algorithm to achieve high power density (55.8 W/in^3) micro-inverter rated at 2kW.

In the second part of the dissertation a new class of multilevel converters, namely Interconnected Modular Multilevel Converter (IMMC), is introduced and studied in detail. The IMMC provides a new framework for DC-DC and DC-AC conversion exploiting Wide Band Gap devices in a modular structure, achieving high power density in high voltage applications. The performance of the proposed IMMC is evaluated through theoretical analysis and experiments.