Improving Stability Margins with Grid-Forming Damper Winding Emulation

Abstract

This work presents (i) a framework for certifying small-signal frequency stability of a power system with line dynamics and heterogeneous bus dynamics, (ii) a novel reduced-order model of damper windings in synchronous machines, and (iii) a proportional-derivative (PD) damper winding emulation control for voltage-source converters (VSCs). Damper windings have long been understood to improve the frequency synchronization between machines. However, the dynamics of the damper windings are complex, making them difficult to analyze and directly emulate in the control of VSCs. This paper derives a reduced-order model of the damper windings as a PD term that allows grid-forming controls for VSCs to emulate their effect on frequency dynamics. Next, a framework for certifying small-signal frequency stability of a network with heterogeneous bus dynamics is developed that extends prior results by incorporating line dynamics. Finally, we analytically demonstrate that PD damper winding emulation can improve the stability of grid-forming converter controls. These results are validated with electromagnetic-transient (EMT) simulation.