String Stability in Microgrids Using Frequency Controlled Inverter Chains

In this letter we identify, and propose a solution for, the string stability problem that may arise in frequency droop control schemes for a type of inverter-based microgrid. We consider a previously proposed frequency droop control with secondary control loop and we investigate the effect on the performance due to an increase in the number of inverters connected to the microgrid. To mitigate the observed performance deterioration, we propose a new controller that guarantees string stability of the inverter-based microgrid and show its performance via simulations.