Transient Stability of Droop-Controlled Inverter Networks With Operating Constraints

• Published in: IEEE transactions on automatic control Vol. 67; no. 2; pp. 633 - 645
• Main Authors: Smith, Kevin D., Jafarpour, Saber, Bullo, Francesco
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.02.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Automation & Control Systems; Control stability; Distributed generation; Droop-controlled inverters; Energy sources; Engineering; Frequency control; Frequency synchronization; Inverters; Kuramoto–Sakaguchi model; Mathematical model; Networks; Numerical stability; Power system stability; Robustness (mathematics); Stability analysis; Stability criteria; stability of inverter networks; Transient analysis; Transient stability; Voltage control
• ISSN: 0018-9286; 1558-2523
• DOI: 10.1109/TAC.2021.3053552

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.