Performance of droop-controlled microgrids with heterogeneous inverter ratings

This paper characterizes synchronization performance and total transient power losses in droop-controlled microgrids with heterogeneously rated inverters. We consider frequency and voltage dynamics for a Kron-reduced network model with highly inductive lines in the presence of impulse disturbances. We quantify the total transient frequency and voltage deviations from synchrony and the associated total transient resistive losses through the L2 norm of the system output. We derive closed-form expressions for this norm that depend on the heterogeneous droop gains and properties of the network. Our results indicate the importance of inertia in mitigating transient frequency deviations. We also show that if disturbances are uniform, the transient resistive losses are given by a monotonically decreasing function of the active power droop gains regardless of the network topology. Numerical examples further analyze these losses, revealing that they can be amplified by high droop gain heterogeneity. This relationship indicates that non-uniform power sharing requirements can limit performance.