Improvement of Small Signal Stability of Islanded Microgrids by Adding the Selective Dynamic Droop Gains

In this paper, the improvement of small signal stability of islanded inverter-based microgrids by selective dynamic gains of droop are discussed. An acceptable improvement must be reached by using the possible minimum number of voltage source inverters in order to adding the proper dynamic gains to their droop characteristic. First, using the linearized equations of inverter-based islanded microgrids, a state-space equation of islanded microgrids is presented. Then, a microgrid test system is considered and a sensitivity analysis is applyied to its low-frequency eigenvalues wih a low damping factor. Using the sensitivity analysis, the more effective voltage source inverters are identifiyed such that the addition of proper dynamic gains only to their droop characteristic can increase the damping of low-frequency power oscillations of microgrid. A simulation study is carried out in order to verify the effectiveness of selective dynamic gains of droop in PLECS software.