June-Seok Lee, Kyo-Beum Lee, and Frede Blaabjerg, "Open-Switch Fault Detection Method of an NPC Converter for Wind Turbing Systems," in Proc. ECCE Conf., Sep. 2013, pp. 1696–1701. > Paper

In wind turbine generation (WTG) systems, the neutral-point-clamped (NPC) topology is widely used as the part of a back-to-back

converter since the three-level NPC topology has more advantages than the conventional two-level inverter especially for high power.

There are twelve switches in the NPC topology and an open-switch fault of the NPC converter leads to current distortion and the

torque ripple in the system. Furthermore, WTG systems can breakdown in the worst case by this ripple. To improve the reliability of

WTG systems, an open-switch fault detection method is required. The open-switch detection method of the NPC converter is different

from that of the NPC inverter due to the different current paths of the NPC converter. This paper proposes the open-switch fault

detection method of the NPC converter connected the permanent-magnet synchronous generator (PMSG). Moreover, the open-

switch fault effects on the current are analyzed by considering the input current magnitude and the modulation index.