Time Delay Stability Analysis and Control Strategy of Wind Farm for Active Grid Frequency Support

With the rapid development of wind turbines and rising penetration levels, grid codes now require wind farms to provide active frequency support. However, time delays in fast power response reduce the stability of system frequency modulation. This study focuses on integrated inertia control and droop control of wind turbines with explicit consideration of time delays. First, the frequency modulation process is analyzed, and the main sources of time delay are identified. A system frequency response model is then developed, incorporating the time delay link into the state-space equations. Based on this model, frequency-domain and linear matrix inequality methods are applied to analyze delay-independent stability and time delay margins of wind turbines. A PI controller for the synchronous unit is designed, and compensation parameters for wind turbine delay are calculated to enhance system stability. Simulation results show that with a wind penetration level of 50%, the system becomes unstable when the delay reaches 0.32 s. By applying the proposed strategy, stability can be maintained even with a delay of 0.5 s. These results confirm the effectiveness of the proposed strategy and highlight its potential for improving frequency regulation in high-renewable power systems.