Fault tolerant‐topology and controls for a three‐level hybrid neutral point clamped‐flying capacitor converter

Abstract

This study details a three-level hybrid fault-tolerant converter. The definition of an original decoupling solution between the fourth flying capacitor (FC) leg and the three neutral point (NP) clamped-based phases overcomes topology hybridisation issues. Under normal conditions, a control strategy of the FC-based leg leads to a converter NP voltage balance, and decreases the DC side capacitors' volume and cost. Under fault conditions, the presented fault isolation and converter reconfiguration strategies generate a post-fault converter, which is able to operate safely with the added FC-based leg. The proposed topology is an interesting trade-off between converter fault-tolerant capability and its complexity and offers the ability to be simply reconfigured and controlled in the case of switch fault occurrence. Two operation modes under fault conditions are presented and their performances are shown and discussed through simulation results and first experimental tests.

Multi‐channel VSI fed large variable speed asynchronous hydro‐condenser: fault analysis, fault diagnosis and fault tolerant control

“…Fault detection based on current distortion approach was discussed in [25,26] which requires high computational efforts. Fault tolerant control for the various electric drives was discussed in [28][29][30][31][32][33], where [31] reviewed fault-tolerant and reconfiguration techniques in power converter fed electric drives. Further, back-to-back power converter redundancy issues in large rated HVDC stations were reported in [34].…”

An Advanced Three-Level Active Neutral-Point-Clamped Converter With Improved Fault-Tolerant Capabilities

“…The faulttolerant operation for the outer switch faults in the NPC rectifier was achieved based on modifying the modulation reference voltage to connect the associated faulty leg to the dc-bus neutral point. A hybrid fault-tolerant three-level NPC converter was introduced in [9]. The fault-tolerant capability of such topology is based on the introduction of a fourth flying capacitor phase leg to provide an active neutral point for the original three NPC phase legs.…”