A Simple Approach to Damp SSR in Series-Compensated Systems via Reshaping the Output Admittance of a Nearby VSC-Based System

This paper presents a new technique to damp subsynchronous torsional oscillations in a series-compensated system with multimass synchronous generator by reshaping the output impedance of an electrically nearby voltage-source converter (VSC; e.g., interfacing a high-voltage dc transmission system or wind farm). The incremental output admittance of a VSC that is constructed by the circuit components and control parameters of a VSC is the key element for VSC-grid interactions. The proposed subsynchronous resonance damping controller is based on reshaping the virtual output admittance of the interfacing VSC-based system to ensure positive damping in the vicinity of torsional modes. The proposed reshaping technique uses the voltage at the point of common coupling in cascaded compensators to magnify the positive resistance without using generator or turbine speed and/or torque perturbations. Time-domain simulation results and laboratory-scale experimental results are presented to validate the theoretical analysis and show the effectiveness of the proposed approach.