Research On Modular Multilevel Voltage Balancing Strategy Optimization And Fault Tolerance Strategy

Through simulation sub-module of the modular multilevel converter(modular multilevel converter,MMC)equalizing strategy optimization and fault tolerance policy research.Firstly,the development history of MMC and the working principle,mathematical model,modulation strategy and other aspects of MMC are expounded.Secondly,the pressure equalization strategy of MMC is studied in depth,and a pressure-sharing strategy based on improved heap-ordered phase-shift modulation is proposed.Finally,a redundant fault-tolerant strategy is analyzed and researched,and the reliability of the strategy is verified by simulation.Aiming at the problem of large number of MMC submodules and the large amount of traditional sorting operations,a new strategy based on heap sorting algorithm for optimizing the pressure equalization of MMC is proposed.Through theoretical analysis of heap sorting,the mathematical formula of its time complexity is deduced.When the number of submodules is larger,the number of comparisons between push sorting and traditional sorting can be reduced by more than 60%,and the sorting operation rate is optimized;The complexity of the control system,combined with improved carrier modulation strategy,uses a shared modulation wave to modulate the sub-module capacitance voltage,improving the effect of voltage equalization.The MMC model was built by Matlab/Simulink for simulation analysis.The effectiveness of the pressure equalization optimization strategy based on the heap sorting algorithm combined with the improved carrier modulation was verified.While maintaining the voltage equalization effect,the heap sorting algorithm effectively solves the problem of large amount of calculation compared to the conventional sorting method.The MMC sub-module fault tolerance strategy research.First of all,the principle of fault module generation and its influence are analyzed.A variety of traditional redundancy fault-tolerance schemes were compared and analyzed.It was concluded that when separate measures such as hot-spacing and symmetrical resection were used,redundant modules could flow current to cause device damage and multiple bridges were added.The complexity of arm operation.Aiming at the problem of the MMC losing reliable operation due to the failure of the sub-modules,a redundancy fault-tolerant strategy based on phase-shifted carrier allocation was analyzed.This strategy solves the problem of failure and verifies the reliability of this strategy through simulation.