Stability assessment for multiple grid-connected converters based on impedance-ratio matrix and Gershgorin’s Theorem

Abstract

Recent years have witnessed emerging oscillatory stability issues in power systems with high-penetration renewable and large power electronic loads. These issues are generally caused by the dynamic interaction between the AC/DC grid and power electronic converters. However, the traditional impedance analysis has some limitations to study the small disturbance stability of multiple grid-connected converters. In this paper, the system is modeled as a medium and high dimensional negative feedback system with a stable open-loop function, which the equivalent open-loop function is defined as impedance-ratio matrix. Moreover, a sufficient stability criterion based on Gershgorin’s Theorem is developed through directly estimating the possible range of eigenvalues. Finally, the validity of the criterion is verified by a 7-infeed converters system. Theoretical analysis and electromagnetic transient simulations show this criterion has the potential to assess the high-order system small disturbance stability problems with low computational complexity. Moreover, its low conservatism as a sufficient criterion is helpful to guide the parameter design for grid-connected system.