Analysis and Suppression of Low-frequency Oscillation in the SVG Multi-machine Parallel System

Static var generator (SVG) is an essential mean to mitigate power quality issues in the grid. However, SVGs operate in harsh grid environments and are often connected to grids in parallel with multiple machines, making the system prone to low-frequency instability. To address low-frequency oscillations in multi-machine parallel systems, this paper develops a model of the output impedance of a multi-machine parallel system and analyzes the effects of controller parameter perturbations on system stability. Therefore, a stabilizing control strategy based on capacitive voltage feedforward and proportional resonant-repetitive controller (PR-RC) parameter optimization is proposed. Finally, the validity of the stability control strategy is verified experimentally.