Drivetrain Oscillation Analysis of Grid Forming Type-IV Wind Turbine

The grid forming strategy can be applied in the wind turbine system and offer better grid supporting service than the traditional grid following strategy. A popular method is to implementing the grid forming strategy in the grid side converter (GSC) system while the machine side converter (MSC) system controls the DC-link voltage. Compared to the grid following wind turbine (GFL-WT), the role of GSC and MSC are exchanged in the grid forming wind turbine (GFM-WT), therefore the electrical torque response of GFM-WT is different from the one of GFL-WT and the drivetrain oscillation caused by the incompatibility between electrical torque response and drivetrain model needs to be analyzed. This paper investigates the drivetrain oscillation of the virtual synchronous generator (VSG) based type-IV wind turbine. The mechanism of drivetrain oscillation is explained by the linearized model in frequency domain. Then, a damping control strategy is proposed to suppress the drivetrain oscillation, and its effectiveness is verified by time domain simulation.