Comparative analysis of redundancy methods in medium-voltage multilevel voltage frequency converters based on cascaded H-bridges

This paper examines the most common power circuit topologies of medium-voltage multilevel frequency converters and the methods employed to enhance their fault tolerance. A comparative analysis assesses how failures of individual power cells affect industrial equipment performance. The cascaded H-bridge (ML-SCHB) configuration offers distinct advantages in terms of modularity and linear scalability, explaining its widespread adoption in high-power electromechanical systems operating at medium and high voltage levels. An overview of circuit design solutions reveals current trends in the domestic and international markets for medium-voltage frequency converters. Structural modeling compares two redundancy strategies: cell-level bypass and inverter neutral point shifting. Simulation results confirm that the neutral shift algorithm outperforms the cell-level bypass method in preserving electric drive functionality under fault conditions. When a single power cell fails in one phase, the neutral shift algorithm enables the drive to maintain rated electromagnetic torque and angular speed – a capability not achievable with cell-level bypass. These approaches can inform the design of fault-tolerant medium-voltage electric drives for applications in the oil and gas, mining, and power generation industries.

Authors: O. V. Nos, G. S. Sidorov

Direction: Electrical Engineering

Keywords: multi-level voltage inverter, cascaded H-bridges, emergency operation, redundancy, control algorithms, neutral shift

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