Method to control flux balancing of high‐frequency transformers in dual active bridge dc–dc converters

Due to non-ideal behaviours and switching characteristics, dc bias might be generated in the dual active bridge converters. It could be more serious in the high-frequency transformers because of small loop resistances. It could also restrict the range of operating flux density due to the threat of saturation. This study analyses the steady-state dc bias and divides it into two categories. Then an active flux-balancing control method is proposed to eliminate these dc biases. It uses separate proportional integral controls and adjusts duty ratios of both sides independently to achieve flux balance. A generalised average model is established to verify its dynamic performance and stability. Simulation and experimental verification on a laboratory prototype confirm the performance of this approach.