Research on Power Failure Mechanism of Bypass Trigger Board in Modular Multilevel Converter Submodules

This study addresses the reliability issues of bypass trigger boards in modular multilevel converters (MMC) for high-voltage direct current (HVDC) systems. Through fault diagnosis and experimental reproduction, it reveals the failure mechanism of ARCH power modules: Capacitance decay of primary-side electrolytic capacitors causes overvoltage breakdown of power management chips. An optimized solution replaces externally purchased modules with self-developed redundant power circuits. By adopting a differential-mode inductor-free topology to suppress voltage spikes induced by capacitor failure and implementing deep derating design for key components, system robustness is significantly enhanced. Validated by GB/T 17626 EMC tests, GB/T 2423 environmental adaptability tests (including 100 ℃ extreme temperature tests), and multi-project scenarios, the new solution achieves zero-failure operation. This research provides a feasible technical pathway for the self-reliant and controllable design of power supply systems in uhvdc flexible transmission projects, while addressing operational risks in converter valves.