Abstract: Compared with onshore wind power，the natural conditions at sea are bad and the traffic is

inconvenient to maintain the wind power system，so wind power system needs to be highly reliable. The system

reliability can be effectively improved by using fault-tolerant control. A fault-tolerant control strategy by injecting

reactive circulating current was proposed for open circuit fault of the parallel three-level converter outer IGBT. By

injecting reactive circulating current into the faulty converter，the converter operates at unity power factor，so that

the faulty phase current bypasses the faulty outer IGBT，and the system can operate in a fault-tolerant state

effectively. Compared with the fault-tolerant method of injecting d-axis current，injecting reactive circulating current can effectively reduce the copper consumption of the generator without changing the power factor of the entire system. The effectiveness and feasibility of the fault-tolerant control strategy were verified by simulation.

      Key words: parallel wind power converter；three-level；fault tolerant；reactive circulating current injection；

reliability