Stability Enhancement for IBRs Operating in Weak Grids Through Proper Coordination and Control

In this work, a coordination and control scheme for multiple inverter-based resources (IBRs) operating in weak grids is proposed to improve stability margin close to the steady-state power transfer limit. The scheme can achieve further stability enhancement even with well-designed individual IBR's control. The key philosophy is to have one set of IBRs providing modulated reactive current that can mitigate weak grid oscillations. This philosophy is realized through coordination or implementing a voltage feedback control to modulate the reactive current order of a set of IBRs. To test its robustness, three testbeds experiencing 3-Hz to 7-Hz oscillations are examined. Additionally, a grid-forming converter is also tested. In electromagnetic transient (EMT) computer simulation, the proposed coordination scheme is shown to improve both small-signal stability margin and large-signal stability. Furthermore, experiments have been conducted in a hardware testbed to demonstrate the efficacy of the coordination and control scheme.