Small-Signal Analysis Framework for Microgrids

The primary control law in Distributed Energy Resources (DERs) within a microgrid strongly influences its dynamic response and can determine its stability. This control law involves the feedback of the active and reactive power or the dq currents at a local reference frame to compute the converter’s voltage and frequency. This study discusses a methodology for the small-signal stability analysis including the phase angle between the DERs and their point of coupling as part of the system state. The system is represented in a common reference frame rotating appropriately the primary control law, and the operating point is determined by solving a nonlinear system of equation. This method is akin to load flow analysis but includes the effect of the control law, and hence is more accurate. Subsequently, the system is linearized to compute its modes. The stability analysis is exemplified on a 10 kVA simulation microgrid prototype with two DERs. The results show variations in system response under different droop designs and provide valuable insights into the system response and its local stability.