Understanding Subsynchronous Oscillation in DFIG-Based Wind Farms with Rotor-Side Converter Control Based on the Equivalent RLC Model

This paper aims to reasonably demonstrate the role of the rotor-side converter (RSC) in subsynchronous oscillation (SSO) and investigates the influence and relationships of all control parameters. Thus, the equivalent circuit of a doubly fed induction generator (DFIG) that considers the RSC is imperative. First, the pertinent equivalent model of a DFIG with RSC control is established. Compared with previous works, this paper innovatively merges the RSC and induction generator with flux and voltage, obtains a complete analytical expression for the equivalent power supply and impedance containing all parameters of both the inner and outer loops of the RSC and then constructs a reasonable equivalent model. The action of the RSC is successfully demonstrated and reflects how the control loops and parameters of the RSC affect the circuit structures and properties of the equivalent model. Then, based on this proposed model, the influence mechanism of the RSC on the SSO of the grid-connected system is carefully analyzed.