Investigation on Dynamic Stability of an Islanded Microgrid and Optimization for Its Controller Parameters

In this paper, a framework for dynamic stability analyses of a typical inverter-based islanded microgrid is presented. The studied microgrid consists of energy storage systems, which are controlled by two kinds of strategies, namely active/reactive power (P/Q) control and voltage/frequency (V/f) control, and photovoltaic (PV) generation, which is assumed to work in the maximum power point tracking (MPPT) mode, and constant active/reactive load. The comprehensive dynamic model of the considered microgrid is developed, based on which a bunch of small-signal models are deduced at stable operating points. Then by means of eigenvalue-theorem-based stability analysis, the relation between damping modes and state variables can be derived. Afterward, a global optimal method is implemented to improve system stability, which is based on the investigation of the controller parameters that affecting the traces of eigenvalues. The simulation results show that the improved system is more stable after suffering small disturbance of a light intensity step down and a step up.