Power Optimization Allocation Method of Direct-Drive Wind Turbines for Mitigating Grid Transient Frequency Dip

With the increasing penetration level of wind power, the inertia and frequency regulation ability of the power grid will be significantly reduced. After fault occurrence, the wind turbines enter the low voltage ride-through (LVRT) and implement a post-fault delay active power recovery, causing a short-term large power shortage that may result in a serious frequency dip. This paper proposes a power optimization allocation method for direct-drive wind turbines to mitigate grid frequency dip. Firstly, the power response and energy conversion process of the wind farm (WF) and synchronous generator during the complete LVRT processes are analyzed. It is found that the energy shortage caused by WF during the LVRT recovery process can approximately reflect the frequency dip. Then, taking the wake effect into account, an optimization method is designed in which the objective is to minimize the energy shortage caused by WF during the LVRT recovery process by adjusting the pre-fault steady state power of upstream and downstream wind turbines. Finally, the effectiveness of the proposed optimization method is verified in different wind speed scenarios.