Low-frequency Oscillation Suppression in Power System Based on the Sensitivity of Damping Ratio of Critical Mode with Respect to DFIG’s Stator Voltage

Integration of doubly-fed induction generators (DFIGs) affects the low-frequency oscillation (LFO) in the power system. This paper analyzes the impact of the stator voltages of DFIGs with the constant voltage control on the damping ratios of critical modes and proposes a suppression strategy of the LFO. The analysis model for small-signal stability is established for the power system with the synchronous generators (SGs) and the constant-voltage-controlled DFIGs, followed by the identification of critical modes. The elements affected by DFIG’s stator voltage in the coefficient matrix are analyzed. With the help of the power flow equations, the sensitivity of the coefficient matrix with respect to the DFIG’s stator voltage is derived. Then, the sensitivity model of damping ratio of critical mode with respect to the DFIG’s stator voltage is proposed. The quasi-proportional resonance (QPR) control is applied based on the sensitivity model to adjust the stator voltage of the DFIG to suppress the LFO. The simulation validates the proposed sensitivity model and the effectiveness of the QPR control on suppressing the LFO.