Transient Stability Analysis of Direct Drive Wind Turbine in DC-Link Voltage Control Timescale during Grid Fault

Transient stability during grid fault is experienced differently in modern power systems, especially wind-turbine-dominated systems. In this paper, transient behavior and issues of a direct drive wind turbine recovery DC-link voltage control timescale are studied. First, the motion equation model that depicts phase amplitude dynamics internal driven by unbalanced active reactive developed to physically depict characteristics itself. Considering switch induced climbing, two-stage employed. Based on model, single machine infinite bus system studied, analysis also divided into two stages: after climbing. During novel approximate analytical expression proposed clearly reveal frequency turbine, which identified as monotonicity at excitation After large-signal oscillation concerned. A idea combining time-frequency based Hilbert transform high order modes employed investigate nonlinear oscillation, characterized time-varying attenuation ratio. It found even related closely final point With large climbing rate, may lose stability. Simulated results MATLAB® presented verify theoretical analysis.