Stability Assessment of Pω and PV Droop Controls in Highly Resistive Microgrids using Analytical Impedance Models

Low-voltage microgrids usually exhibit highly resistive line impedances, complicating the choice of a suitable power-related control algorithm for the connected inverters. Pω and PV droop controls are the most common choices, being derived for a purely inductive and purely resistive grid impedance. While both have their pros and cons, both must be analysed accurately when it comes to stability issues arising due to parallel operation. The sequence impedances of the Pω and PV droop controls (and their reactive counterparts) are therefore derived and compared to each other. Both outer power-related controls provide a voltage reference to the inner cascaded voltage and current control, which is defined in the natural reference frame and is used for both controls to guarantee comparability. The impedance models are analytically derived by applying linearization and validated by time-domain simulations in MATLAB/Simulink and measurements in a power-hardware-in-the-loop setup.