The dual active bridge (DAB) is one of the key elements in different DC microgrid clusters. DAB also has isolation features and bi-directional power transfer capabilities between two power buses of similar or different levels, i.e. low voltage and high voltage buses. Due to the galvanic isolation and modularity nature of DAB, the output can be easily interconnected for efficient and reliable power sharing. In this paper, this advantage of modularity is applied in microgrid applications. A robust bi-directional power sharing control strategy is developed between DABs from different high voltage buses to low voltage buses in order to improve the voltage stability of the microgrid. The designed controller considering the non-linearity and uncertainty ensures stable DC bus voltage and reliable power sharing among DABs under different operating conditions.