Open-Circuit Fault Diagnosis and Tolerance Strategy Applied to Four-Wire T-Type Converter Systems

• Published in: IEEE transactions on power electronics Vol. 34; no. 6; pp. 5764 - 5778
• Main Authors: Wang, Ke, Tang, Yi, Zhang, Chuan-Jin
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Circuit faults; Circuits; Computer simulation; Converters; Data buses; Electric potential; Fault diagnosis; Fault location; Fault tolerance; Fault tolerant systems; four-wire system; Offsets; Strategy; Switches; System effectiveness; T-type topology; Topology; Wire
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2018.2869396

Due to the zero-sequence currents in the four-wire systems, the three-phase currents become more complex on both amplitudes and phases in the unbalanced load conditions, so that the existing open-circuit (OC) fault diagnosis methods of the switching devices cannot be directly used. In this paper, an OC fault diagnosis strategy applied to four-wire T-type converter systems is proposed, which is implemented by decomposing the circuit model into a positive- and negative-sequence model and a zero-sequence model, and locating the OC fault based on the law of positive- and negative-sequence voltage error offsets and zero-sequence voltage error offsets. The proposed diagnosis method is suitable for both unbalanced load and unbalanced input voltage conditions. Meanwhile, the differences of fault-tolerant control between four-wire and three-wire systems are analyzed and compared. An effective fault tolerance strategy for inner OC faults applied to four-wire T-type converter systems is presented, which owns the ability to suppress dc bus imbalance. Simulation and experimental results are presented to verify the correctness of the proposed strategy.