A solid-state transformer (SST) is one of the promising candidates to interface the renewable generation to a power distribution system. An emerging and attractive topology for the building block of the next generation SST is the multiple active bridge (MAB) dc-dc converter. The MAB converter technology has the inherent capability to reduce the number of the high-frequency magnetic links (HFMLs) and the overall complexity of the system, especially in multi-module-based SST configurations. However, an MAB converter suffers from the power unbalance issues due to the parameter mismatch of the HFML. As, several active bridges share a common HFML in an MAB converter, the controller architecture should ensure that the bridges share the same amount of power and the output port maintains a constant dc voltage. In this paper, an improved control architecture is proposed for the HFML-based MAB dc-dc converter for use in the SSTs. The simulation and experimental results show that the designed controller can effectively mitigate the power unbalance issues of the MAB converter due to the HFML parameter mismatch, while maintaining a constant dc voltage at the output.