Large & small signal modeling of dual active bridge converter using improved first harmonic approximation

The paper derives a technique to develop large and small signal state-space models of a single-phase dual active bridge (DAB) based DC-DC converter operated in phase-shift mode. An improved first harmonic approximation (I-FHA) method is proposed by introducing a correction factor to the conventional first harmonic approximation (FHA) technique. The output DC voltage and the two orthogonal components of first harmonic of transformer current, corresponding to active and circulating powers, are used as state-variables. The large-signal model, thus derived, is of simple form and accurate for ideal converter. A small-signal model is also developed from the I-FHA model. Finally, the large and small signal models are validated through time-domain simulations and experimental results.