Design of sub-synchronous oscillation proportional resonance damping controller for doubly-fed wind turbines based on impedance analysis

Doubly fed induction generators are widely used in wind power generation because of their efficient and low-cost power generation and active-reactive power decoupling control features. For the problem of sub-synchronous oscillation generated by the grid-connected doubly-fed wind turbine through series compensation line, this paper firstly carries out the eigenvalue participation factor analysis of the small signal model including the multi-physical control links of grid-connected system, and an impedance model is constructed for the quantitative analysis of the sub-synchronous oscillation damping characteristics. Applying impedance analysis on the above model, it is concluded that the negative equivalent resistance under the resonant frequency is the cause of sub-synchronous oscillation. Then a controller was designed that uses a high-pass filter in series with a proportional-resonant link to generate an additional oscillation damping component in the rotor winding modulation voltage. Based on the analysis of how controller parameters affect the impedance characteristics, the inequality constraint conditions for the parameter design to optimize the controller’s impedance compensation characteristics and robustness to oscillation frequency is proposed. Finally, the oscillation suppression effect of the controller is analyzed by time domain simulation and it is tested that the controller can suppress sub-synchronous oscillation and has adaptability in scenarios with different parameters.