In a hybrid AC to DC micro grid system one important task is to control the DC bus voltage. To improve the DC-bus voltage control dynamics, the non-linear disturbance observer based DC-bus voltage control is used, which does not need the remote measurement and enables the important plug-and-play feature. Based on this observer, a novel DC-bus voltage control scheme is developed to suppress the transient fluctuations of DC-bus voltage and improve the power quality in such a micro grid system. But it gives low stability and there is no feedback control loop. The efficiency of DC source utilization is less in DC grid.