A Unified State-Space Modeling Method for a Phase-Shift Controlled Bidirectional Dual-Active Half-Bridge Converter

In certain applications of phase-shift (PS) controlled dual-active half-bridge (DAHB) extended dc-dc converters, the duty cycle is not fixed at 50%. The existing state-space modeling methods are only suitable for modeling such a converter in two PSs directions separately, which results in a positive-PS model and a negative-PS model. This is inconvenient for study the converter operation where the PS direction changes online, such as in the energy storage applications. Hence, a unified approach is very desirable to include the two PS directions into a single model. However, this is very challenging for non-50% duty cycle. The current-fed dual half-bridge (CF-DHB) converter is one typical example of such converters. For the CF-DHB converter, this article proposes an approach for the bidirectional PSs unification. The approach is named the `conjugate PSs superposition technique.' A basic modeling method is also proposed based on the approach. A single model built by the method can be utilized for both positive and negative PSs, even with a non-50% duty cycle. A large-signal model and a small-signal model are established. Simulations and experiments are used to validate the PSs unification approach and the modeling method.