Small signal stability in microgrids with high penetration of power electronics interfaced sources

In this paper, effect of power electronics interfaced sources on small signal stability in the presence conventional sources (synchronous generators) in a microgrid is studied. A detailed mathematical model for small signal analysis is presented. The models are linearised around operating point and state space matrix is used to find the eigenvalues at that point. Eigen value analysis is done to study the effect of placement of inverter and/or synchronous generator in a system on its stability. The effect of droop system response is also studied. Steady state stability of microgrid with different combinations of inverters and synchronous generators is presented and maximum allowable droop gain and damping factor for these cases is determined. From the analysis it is found that inverters at some locations tend to make system critical. It is also found that replacing these inverters with synchronous generators increase the stability margin. The results is validated by simulation (eigen value analysis) in MATLAB.