June-Seok Lee, Kyo-Beum Lee, and Frede Blaabjerg, "Open-Switch Fault Detection Method of a Back-to-Back Converter using NPC Topology for Wind Turbine Systems," IEEE Transactions on Industry Applications, vol. 51, no. 1, pp. 325–335, Jan./Feb. 2015. -SCI > Paper

In wind turbine generation (WTG) systems, a backto-back converter with a neutral-point-clamped (NPC) topology is widely used

because this topology has more advantages than a conventional two-level topology, particularly when operating at high power.

There are 12 switches in the NPC topology. An open-switch fault in the NPC rectifier of the back-to-back converter leads to the

distortion of the input current and torque vibration in the system. Additionally, an open-switch fault in the NPC inverter of the back-

to-back converter causes the distortion of the output current. Furthermore, the WTG system can break down in the worst case

scenario. To improve the reliability of WTG systems, an open-switch fault detection method for back-to-back converters using the

NPC topology is required. This study analyzes effects of inner and outer open-switch faults of the NPC rectifier and inverter and

describes a novel open-switch fault detection method for all possible open-switch faults in the back-to-back converter.