Fault tolerance control for outer switches of a 3-level rectifier in wind turbine systems

A three-level neutral point clamped (3L-NPC) topology is used in the most power converters in wind turbine systems. Interior permanent magnet synchronous generators (IPMSGs) have been chosen as the generator in wind turbine systems due to its advantage of size and efficiency. In wind turbine systems consisting of the IPMSG and 3L-NPC topology, to improve the reliability, tolerance controls for open-switch fault should be performed. This paper is focused on the open fault of outer switches (S_x1 and S_x4) when the 3L-NPC topology is used as a rectifier which is connected to IPMSG and is operated at any power factor. Additionally, the effect of S_x1 and S_x4 open-switch faults is analyzed, and based on it, a tolerance control is proposed. The proposed tolerance control maintains the normal operation under the open fault of outer switches by adding a compensation value to reference voltages. The effectiveness and performance of the proposed tolerance control are verified by the simulation.