A Sub-synchronous and Hyper-synchronous Risk Assessment Method for Direct-drive Wind Turbine Based on Dynamic Characteristics

This paper proposes a sub-synchronous and hyper-synchronous risk assessment method for direct-drive wind turbine based on dynamic characteristics. Firstly, this paper establishes the linearization model of direct drive wind turbine and analyzes the influence of inner loop and outer loop control parameters of grid-side converter on oscillation mode, which points out that the oscillation mode is determined by the outer loop parameters of grid-side converter while the inner loop parameters have little effect. Secondly, based on dominant mode method the high-order transfer function of direct-drive wind turbine can be reduced to a second-order system. Thirdly, risk evaluation index of sub-synchronous and hyper-synchronous oscillation for direct drive wind turbine is proposed, which includes overshoot and adjusting-time to fully consider the initial amplitude caused by the disturbance and the attenuation speed of the oscillation after the disturbance. Finally, the feasibility of the proposed risk assessment method and the effectiveness of the evaluation index are verified through calculation example and simulation result.