Fruit fly optimization algorithm multi-objective control method for MMC traction power supply system with unbalanced distribution network

When distribution voltage is unbalanced, the voltage and current on the AC side of the traction power supply system based on a modular multilevel converter (MMC) will have negative sequence components, causing reactive and active power fluctuations. At this time, the circulation current will also occur in the MMC, threatening the safety and operation of the system. Based on the analysis of the power fluctuation mechanism, this paper derives the expression of the multi-objective control function combined with the universal current calculation formula. The fruit fly optimization algorithm (FOA) minimizes the multi-objective function and achieves the purpose of suppressing the coordinated control of the three objectives of negative sequence current and active and reactive power fluctuations. The resonant vector controller (RVC) was used to suppress the circulation current in MMC system. A simulation model was built to verify the effectiveness of the proposed strategy and algorithm.