Transient Stability of Droop-Controlled Inverter Networks With Operating Constraints

Due to the rise of distributed energy resources, the control of networks of grid-forming inverters is now a pressing issue for the power system operation. Droop control is a popular control strategy in the literature for frequency control of these inverters. In this article, we analyze transient stability in droop-controlled inverter networks that are subject to multiple operating constraints. Using a physically meaningful Lyapunov-like function, we provide two sets of criteria (one mathematical and one computational) to certify that a postfault trajectory achieves frequency synchronization while respecting operating constraints. We show how to obtain less-conservative transient stability conditions by incorporating information from loop flows, i.e., net flows of active power around cycles in the network. Finally, we use these conditions to quantify the scale of parameter disturbances to which the network is robust. We illustrate our results with numerical case studies of the IEEE 24-bus system.

Automated summary

This article analyzes the transient stability of droop-controlled inverter networks subject to multiple operating constraints and provides two sets of criteria for achieving frequency synchronization in postfault trajectories. By incorporating information from loop flows, less-conservative transient stability conditions are obtained, and the robustness of the network to parameter disturbances is quantified.