Mitigating Sub Synchronous Oscillations in DFIG Based Wind Farms Connected to Series Compensated Transmission Lines Using a Damping Filter

The phenomenon of sub synchronous oscillations (SSOs) in the modern power grid, which arises from the interaction of renewable energy sources with different power electronic converters (PEC), is a significant concern. Out of the SSO scenarios in renewable energy systems, SSOs in doubly fed induction generator (DFIG) based wind farms connected to series compensated transmission lines is prominent. If SSOs are not adequately suppressed, they can intensify mechanical oscillations in the turbines, causing instability in the generating units and ultimately causing wind turbines to trip or other renewable energy units to shut down. Hence, it is essential to suppress these harmful SSOs in due time. The objective of this research is to design a damping filter to enhance damping of SSOs in DFIG based wind farms connected to series compensated transmission lines. The proposed damping filter is connected across the series compensation and it is tuned to cause parallel resonance at the system frequency and series resonance at the dominant sub synchronous frequency. Simulation results demonstrate the effectiveness of the proposed filter design. Further, the proposed tuning method is adaptive since the dominant sub synchronous frequency in DFIG systems varies due to changing wind speed, number of in service wind turbines and series compensation.