Research on SSO Suppression of DFIG-Based Wind Farm by Impedance Scanning

Nowadays, doubly fed induction generators (DFIGs) are becoming the most widely used wind turbines in wind farms. However, in recent years, there were several subsynchronous oscillation (SSO) events occurred in the grid-connected system of DFIG-based wind farms. To address the issue, this paper obtains the impedance characteristics of the target system by impedance scanning method and proposes a novel scheme to suppress SSO. Firstly, for subsynchronous frequency band, this paper gives a subsynchronous circuit model of the system. Then based on the divergence mechanism of subsynchronous components, we develop a scheme that embeds the designed filters in rotor side converter (RSC) control loops to remove the subsynchronous components contained in the feedback signals. Through this scheme, we can block the divergence process of the subsynchronous components and increase the damping of the system to the subsynchronous components. Finally, the proposed scheme is verified by impedance scanning and time-domain simulation analysis.