Stability-Constrained Adaptive Droop for Power Sharing in AC-MTDC Grids

A secure operation of AC-multiterminal dc (MTDC) grids following an (N-1) contingency (e.g., converter outage) is of a major concern for the system planners and operators. For the case of converter outage, the concept of adaptive droop control enables the healthy converters to share the burden of power mismatch in an effective manner. However, certain settings of the droop coefficients may lead to instability of the AC grid where multiple converters are connected and one of them goes out. This paper proposes a stability-constrained adaptive droop approach for autonomous power sharing following the outage of a converter in an MTDC grid. A trajectory sensitivity analysis-based approach is presented to impose the constraints on the adaptive droop gains that can be an outcome of dynamic security assessment performed by the system operators. The robustness of the proposed approach for post-contingency system is demonstrated through nonlinear time-domain simulation results using models developed in MATLAB/Simulink.