New approach to damp subsynchronous resonance by reshaping the output impedance of voltage-sourced converters

This paper analyzes and investigates the effect of a voltage-source converter (VSC) on subsynchronous resonance and system damping interaction in a series-compensated system with multi-mass synchronous generator. The incremental output impedance/admittance of a VSC that is constructed by the circuit components and control parameters of a VSC is the key element for interactions with the grid. It has been shown that a VSC system might introduce negative damping (due to its negative resistance) that degrades the system damping from one side, and its reactive proprieties might affect (shift) the network resonance frequency and alter the damping prolife on the other side. An active damping controller is developed to reshape the output impedance of the interfacing VSC and minimize its associated negative impact. With little modification, the proposed damping technique is also able to damping the SSR, in a series-compensated system, as a new approach to damping SSR. Time-domain simulation results are presented to validate the theoretical analysis and show the effectiveness of the proposed active damping technique.