INVESTIGATION OF DUAL ACTIVE BRIDGE (DAB) DERIVED POWER DENSE SINGLE-STAGE ISOLATED INVERTERS

Abstract

Power electronics converters are increasingly gaining importance in renewable energyapplications. Single-phase inverter, in particular, which converts direct current (DC) to alternating current (AC) power or vice versa, is one of the most promising applications of power electronics in avenues such as solar photovoltaic (PV) and electrified transportation. Traditionally, the architecture of isolated single-phase inverters requires two discrete power conversion stages, i.e. an isolated DC-DC stage with a voltage boost cascaded with an additional high voltage DC-AC stage. This Ph.D. dissertation proposes a study of isolated single-stage inverters based on dual active bridge (DAB) converters, which are typically used for DC-DC conversion. By studying the impact of topological modifications using direct matrix variations, this study extends the advantages of DAB converters for compact and high-efficiency inverter applications. This dissertation makes several key contributions toward the development of compact,high-performance single-stage DAB-based inverters for grid-tied applications. A frequency domain modeling framework is introduced to accurately capture the steady-state operation and phase-shift dependencies of DAB converters during AC line-cycle operation. Dual-phase shift modulation is used to regulate power flow, and a numerical optimization routine is developed to minimize current stress and switching losses while trying to meet zero-voltage switching (ZVS). To facilitate real-time implementation, a three-dimensional lookup table (3D LUT) with trilinear interpolation is employed to determine optimal modulation parameters across the AC line cycle. The models and control strategies are validated through hardware implementation in a 400W GaN-based inverter prototype. The dissertation also addresses battery reliability in low-voltage charging systems, wheresecond-order current ripple (SOCR) can lead to increased losses and degradation. A bidirectional single-stage AC-DC converter with an active boost compensation circuit is proposed to mitigate SOCR while preserving system compactness. This solution eliminates the need for bulky passive filters or large intermediate DC-link capacitors commonly used in two-stage converters. The proposed architecture supports galvanic isolation and bidirectional power flow, making it well suited for grid-to-battery (G2B) and battery-to-grid (B2G) applications. Experimental results confirm significant ripple attenuation and reduction in internal battery power loss, validating its application in residential storage and electric mobility. Additionally, integrated power decoupling (iPD) topologies are proposed to address secondorder ripple in single-phase systems without relying on external bulky components or additional active stages. These iPD configurations incorporate ripple buffering directly into the main power flow path. Detailed analysis of capacitor sizing and current profiles demonstrates that iPD topologies can significantly reduce system volume while maintaining performance. Overall, the research establishes a unified, compact, and efficient framework for single-stage DAB-based inverter systems in next-generation renewable energy and electrified infrastructure.