High Voltage Ride-Through of DFIG-based Wind Turbines

With the rapid increase of large offshore wind farms in Europe, a new problem associated with the response of wind turbines to temporary overvoltages has arisen. This problem has not been a focus of discussion up to now. The majority of wind turbines use voltage source converters with a DC-link. When the grid voltage exceeds a certain limit the current flow through the line-side converter may reverse, resulting in a rapidly increasing DC voltage. To handle such situations, special countermeasures are required. This paper identifies and outlines the problem and recommends possible measures to ride through the overvoltage safely. Additionally, active voltage control structures to limit the overvoltages are proposed.