Abstract：As the carrier of the distributed generation, micro grid can avoid the disadvantages of the direct connection with the main power grid while the power generated by the distributed generation is reasonably allocted. The seamless switching process between micro grid operation modes directly affects its security, stability and reliability. According to the process of micro grid from the island mode to the grid connected mode, the mathematical relationship between the variables of the inverters is obtained based on Kirchhoff's law, and the mathematical model of the micro grid inverters with unbalanced three-phase load from island mode to grid connected mode is constructed. The model is a dynamic optimization one, and the dynamic optimization algorithm based on Radau configuration method is used to discretize it, and the optimization time is divided into several intervals. The collocation points at each interval are determined by the orthogonal collocation method, and then the optimization results at each configuration point are obtained. The optimal control trajectories of the control variables are obtained by MATLAB.

Keyword：micro grid;seamless switching;dynamic optimization;Radau configuration;inverter;