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

•A Multiple grid-connected converters is modeled as the negative feedback system with a stable open-loop function.•A sufficient stability criterion is proposed based on Gershgorin’s Theorem with low complexity, compared to GNC.•The proposed criterion involves simple algebraic operation with concise form and has less conservatism than norm criterion. 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.