Abstract
Fault-tolerance is critical in power electronics, especially in Uninterruptible Power Supplies, given their role in protecting critical loads. Hence, it is crucial to develop fault-tolerant techniques to improve the resilience of these systems. This paper proposes a non-redundant fault-tolerant double conversion uninterruptible power supply based on 3-level converters. The proposed solution can correct open-circuit faults in all semiconductors (IGBTs and diodes) of all converters of the system (including the DC-DC converter), ensuring full-rated post-fault operation. This technique leverages the versatility of Finite-Control-Set Model Predictive Control to implement highly specific fault correction. This type of control enables a conditional exclusion of the switching states affected by each fault, allowing the converter to avoid these states when the fault compromises their output but still use them in all other conditions. Three main types of corrective actions are used: predictive controller adaptations, hardware reconfiguration, and DC bus voltage adjustment. However, highly differentiated corrective actions are taken depending on the fault type and location, maximizing post-fault performance in each case. Faults can be corrected simultaneously in all converters, as well as some combinations of multiple faults in the same converter. Experimental results are presented demonstrating the performance of the proposed solution.
Highlights
Power electronics converters play a major role in numerous critical applications, causing internal converter faults to carry significant consequences
This paper proposes a new non-redundant fault-tolerant technique for a complete double-conversion Uninterruptible Power Supply (UPS), based on multilevel topologies and leveraging the versatility of FCS-Model Predictive Control (MPC)
The fault-tolerant approach proposed for the 3-Level DC-DC (3LDC) converter is based on the same design principles as the one previously presented for the 3Level Neutral-Point-Clamped (3LNPC) case
Summary
Power electronics converters play a major role in numerous critical applications, causing internal converter faults to carry significant consequences. The solutions in [27,31] provide fault-tolerant capabilities to 3-level NPC rectifiers and motor drive inverters and consider a subset of the initial control set for fault-tolerant operation In these cases, switching states affected by the fault are excluded from the control set only when current in the faulty phase flows in a specific direction (affected by the fault), which allows the converter to still use them in other conditions. Despite the great versatility of FCS-MPC, its application to fault-tolerant solutions has been relatively limited, focusing mostly on the study of single-converter systems (most frequently of 2-level type) and correcting only IGBT faults. The proposed solution leverages the power and versatility of FCS-MPC to enable a selective switching state exclusion and implements highly differentiated corrective action for different faults, maximizing post-fault performance.
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