Micro-Grid Droop Control Strategy and Isolated Island Operation System Stability Analysis

-In the micro-grid, droop control strategy simulates traditional power system droop characteristics , by changing the output of active and reactive power to control the output voltage frequency and amplitude, thus the micro-grid system can work at the stabilize voltage point in island operation mode . And the voltage is more or less with the grid-connect mode,so that the transition is smooth when switching,which can guarantee the load work undisturbed. Microgrid based on droop control can achieve automatically adjust voltage and frequency, without the aid of communication, which can improve system reliability, and easy to implement micro-power and load plug and play. We designed specifically simulation circuit for the droop control strategy on PSIM . And the output waveform is studied. Simulation results show the schematic design of the control strategy is correct.We established an island microgrid complete small-signal state space model, which took into account the inverter power small-signal sub-model, network lines and the load small signal sub-model.It use eigenvalue method to analysis microgrid small signal model state matrix, to get the following conclusions: droop coefficient increases will reduce the stability of the micro-grid system; when the line impedance is smaller, micro-grid is easy to lose stability. Finally, We use the simulation tools to verify the small signal stability analysis conclusions is correct. Key-Words: microgrid, droop control, PSIM, Simulink, converter, small signal stability analysis