Fault-Tolerant Control Method With Enhanced Operational Range for T-Type Converter With Cascaded H-Bridge Under Submodule Faults

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Abstract
This paper investigates the operation of the T-type cascaded H-bridge (T2C-HB) converter following H-bridge submodule faults. Initially, through a detailed analysis of the fault, this paper clarifies that the reason for which voltage balance cannot be achieved under high output voltage conditions is the limited flexibility in selecting redundant switching vectors. In practical applications, to enhance output efficiency, converters are required to operate at high output voltages. However, a fault occurring under such conditions leads to distorted output currents. Existing fault-tolerant (FT) methods, due to the excessive modulation burden on the healthy phases, are only effective under low output voltage conditions. To enhance the reliability of converter operation, this paper introduces an innovative FT method that integrates harmonic injection with clamping techniques. This method enables the converter to rapidly return to normal operating state under nearly all output conditions when a submodule fault occurs. Simulation and experimental results validate the feasibility and effectiveness of the proposed method.
Funding Information
  • National Natural Science Foundation of China (62222309)
  • National Natural Science Foundation of China (62573256)
  • National Natural Science Foundation of China (U22A20245)
  • Major Scientific and Technological Innovation Project of Shandong Province (2024ZLGX04)

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