L/HVRT Technology of Offshore Permanent Magnet Wind Power Based on DC Chopper and Flexible Control Switching

In the offshore wind power transmission project, the failure of the onshore AC main network may cause voltage swells or drops in the offshore wind farm, and may even cause the entire system to be separated from the grid. Firstly,according to the control strategies of the generator-side and grid-side converters of offshore permanent magnet wind power system, this paper analyzes the changes of system operation under low/high voltage fault conditions, and studies the bases for the increase of DC link voltage. Secondly, a fault ride-through scheme based on the command value of DC unloading circuit and switching grid side converter controller is proposed to suppress the rapid increase of DC link voltage during low/high voltage faults, and also provide certain reactive power support for the AC main network during the fault period according to the fault type. For L/Hvrt, this article proposes a fault traversal scheme based on DC Chopper and switching the command value of the grid side controller for different faults, in order to suppress the rapid increase of DC voltage during the faults, and also supply certain reactive power support for the AC main network during faults based on the type of fault. Finally, MATLAB/SIMULINK simulation was used to verify the feasibility of the fault ride-through project.