Fault ride-through and grid disturbance mitigation for the stability of grid-connected floating offshore wind energy conversion systems

Ensuring the stability of grid-connected floating offshore wind turbines (FOWTs) under grid disturbances, such as voltage sags, frequency deviations, and fault ride-through (FRT) events, is challenging, particularly when electrical measurements are transmitted over long-distance submarine cables, which can significantly degrade measurement accuracy. This degrades the control performance, making the control design highly sensitive to variations in grid parameters and increasing the complexity of both fault detection and control. To overcome these challenges, this paper proposes a novel fault-tolerant control (FTC) strategy that ensures adaptive and continuous power delivery to the electrical grid under various operating conditions. First, a high-gain observer is employed for online grid state estimation, enabling real-time monitoring. These estimations are used by a fault detection algorithm to determine the grid operating mode, namely normal operation, fault operation, or off-grid operation. Once a fault is detected, a classification algorithm identifies its type, such as voltage fault, frequency fault, or FRT fault. Furthermore, the FTC algorithm is activated to adapt the control strategy by generating dedicated reference signals for each operating mode, ensuring stable and continuous power injection to the grid under various conditions. The performance of the proposed system is evaluated through a semi-experimental protocol using a Processor-in-the-Loop (PIL) implementation on a TMS320F28027 LaunchPad. The obtained results demonstrate that the FTC algorithm accurately detects and classifies grid faults in real time. In addition, the proposed approach ensures power quality and maintains continuous energy delivery to the grid under fault conditions.