In order to achieve high reliability and flexibility, micro-grids need to be able in synchronous connection as well as asynchronous connection. Due to the different characteristics of micro-grids in these two cases, the functions of distributed power generators should fast and smoothly be adopted. Therefore, the concept of smart micro-grids is developed. In this paper, the enhanced principle of seamless grid connection and disconnection is developed and presented. The evaluation results prove that the distributed power generators with suitable sources and loads on the DC side (e.g. super capacitors, electric vehicles) can be applied as means of grid control. As a result, high reliability and flexibility in distributed power generation can be achieved by using our control principles.