A new converter protection scheme for doubly-fed induction generators during disturbances

Fault ride-through capability is one of the basic requirements for a large-scale wind farm. There are two aspects to fault ride-through: to continue power supply without breaking any part of the system and to resume normal operation after clearance of the fault. In this paper the transients of the doubly-fed induction generator is analyzed. The safe operating area characteristics of the IGBT converter are also considered. After this, the use of a high-power resistor as a traditional crowbar, DC-link braking resistor and a series dynamic resistor are discussed. From the discussion, a new protection control scheme, with a crowbar and a series dynamic resistor, is proposed. The new scheme is shown to reduce the rotor high current, maximize the working time of DFIG control then reduce the power, speed and torque fluctuations and protect it during disturbances. The method is verified using PSCAD/EMTDC simulations.