Analysis and Control of Smooth Transferring for Micro-Grid with Droop Control

The concept of micro-grid requires the system not only to operate in both islanding mode and grid- connected mode, but also transfer smoothly between these two modes. This paper presents a seamless transition strategy for droop-controlled inverters to operate in both islanding and grid-connected modes. The design method of the power outer loop and the stability of power loop are analyzed in quantity by mathematic modeling. Thus, the power loop is well designed to ensure the stability of the micro-grid. Then a new pre-synchronization control strategy is proposed for the micro-grid inverter to transfer smoothly between two different modes. Subsequently, simulation and experimental results show that the desired transient and steady-state responses can be obtained.