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.