A Fault-Tolerant Control Strategy of Modular Multilevel Converter with Sub-Module Faults Based on Neutral Point Compound Shift

Abstract

In view of the complex calculation and limited fault tolerance capability of existing neutral point shift control algorithms, this paper studies the fault-tolerant control method for sub-module faults in modular multilevel converters on the basis of neutral point compound shift control strategy. In order to reduce the calculation complexity of shift parameters in the traditional strategy and simplify its implementation, an improved AC side phase voltage vector reconstruction method is proposed, achieving online real-time calculation of the modulation wave adjustment parameters of each phase required for fault-tolerant control. Based on this, a neutral point DC side shift control method is proposed to further improve the fault tolerance capability of the modular multilevel converter (MMC) system by compensating the fault phase voltage with non-fault phase voltage. By means of the compound shift control strategy of the DC side and AC side of the neutral point, an optimal neutral point position is selected to ensure that the MMC system output line voltage is symmetrical and the amplitude is as large as possible after fault-tolerant control. Finally, the effectiveness and feasibility of the proposed control strategy are verified by simulation and low-power MMC experimental system testing.

Energy Efficiency in Electric Motors, Drives, Power Converters and Related Systems

“…However, no experimental results related to such a type of converter are known in the technical literature. On the contrary, the MMC concept attracts the attention in high-power and high-voltage applications [40,62,63,[77][78][79]: electrical drives [80], HVDC [81][82][83][84][85], photovoltaic [86] and in stationary installations that supply the primary lines of German railways (i.e., from 110 kV-50 Hz three-phase to 110 kV-16.7 Hz single-phase).…”

“…The study of PET involves a widespread range of topics that require accurate investigations: [43,[60][61][62][63][64][65][66][67][68].…”

Challenges and Design Requirements for Industrial Applications of AC/AC Power Converters without DC-Link

“…The power stage of converters contains power transistors with a heatsink and heat dissipation system, a DC-link capacitor, an input filter to provide a unit input power factor, and measurement and control units. In medium-voltage industrial systems, multilevel converters with DC-link are commonly used [12,13]. Multilevel converters offer numerous advantages compared with the two-level converter, e.g., better power quality and lower switching losses, low transistor voltage stress, and high voltage capability.…”

Solid-State Transformers in Locomotives Fed through AC Lines: A Review and Future Developments

“…More submodules can be put side by side or on top of each, with a great exploitation of the available space. On the contrary, the MMC concept attracts the attention in high-power and high-voltage applications [40,62,63,[77][78][79]: electrical drives [80], HVDC [81][82][83][84][85], photovoltaic [86] and in stationary installations that supply the primary lines of German railways (i.e., from 110 kV-50 Hz three-phase to 110 kV-16.7 Hz single-phase).…”

“…Transient behavior in case of pantograph bouncing from the line (frequent event and lasting < 15 ms).• Study of failure modes, fault detection and fault tolerance with bypass of the faulted module[43,[60][61][62][63][64][65][66][67][68].…”