Impact analysis of energy-based control structures for grid-forming and grid-following MMC on power system dynamics based on eigenproperties indices

Abstract

This paper addresses the impact of the modular multilevel converter (MMC) energy control in the system dynamics when grid-forming and grid-following control schemes are used in the same system. The MMC total energy control can be implemented in different approaches. Depending on the control architecture and the level of energy buffering capability the MMC can be used to mitigate the propagation of disturbances from the AC to the DC side and vice-versa. In order to study the effect of this MMC capability in the system dynamics and interactions, a point-to-point link including one grid-forming and one grid-following converter is studied in detail for four different energy-based control architectures combinations. In order to compare them, two eigenproperties indices have been derived. The first index quantifies the participation of the eigenvalues in the system response and the second one, quantifies which states rule on the system dynamics. This study is accompanied with detailed nonlinear models implemented in MATLAB Simulink used to verify the results via time-domain simulations.