An Improved Generalized Average Model of DC-DC Dual Active Bridge Converters

Improvements are proposed for generalized average models of dual active bridge (DAB) converters. Generalized average modeling involves a trade-off between accuracy and tractability. To maintain an acceptable level of complexity, existing DAB models are derived using a first harmonic approximation. These models provide accurate small-signal representations, but are limited as large-signal analysis tools due to persistent steady-state error. This study proposes a modeling framework that provides accurate large and small-signal models without significant increases in overall complexity. The framework describes DAB operation with triple phase shift modulation, and is easily simplified for single, dual, or extended phase shift modulation schemes. The special case of single phase shift modulation, which experiences the most significant large-signal error, is given additional consideration. The framework is applied to open and closed-loop operation, and both large and small-signal models are discussed. Models are validated in simulation and hardware experiments using a small scale DAB prototype