Small Signal Stability of a Series Compensated Microgrid Operating in Islanded Mode

Abstract

In this paper, small signal stability of a simple microgrid operating in islanded mode is analyzed by computing eigen value trajectories when the system is subjected to different parametric changes. Detailed mathematical modeling of a synchronous machine supplying a constant impedance load through a series compensated line is presented. The system is equipped with a speed governor and an Automatic Voltage Regulator (AVR) with a PI controller. Eigen value trajectories of the linearized system are computed by considering parametric changes in the load, degree of compensation, exciter gain and time constant, proportional and integral gains of the PI controller of the AVR and the droop of the speed governor. From the results obtained, it was observed that the system is subjected to oscillatory instability when the AVR parameters and the speed governor droop exceeded certain limits. Also, the system was completely stable when the load and the degree of compensation was varied in a wide range. These results indicate the importance of selection of proper values for parameters of microgrids operating in islanded mode.