Application Research Of MMC In Fuel Cell Power Generation And Grid Connection System

Modular multi-level converter(MMC)as a new type of converter topology,connects the power generation unit to the MMC sub-module through the DC/DC converter to improve the power level while avoiding the series and parallel connection of the power generation unit itself The adverse effects greatly increase the flexibility and reliability of the system.At the same time,with the rapid development of smart grids,clean energy is gaining more and more attention.Fuel cells have obvious advantages such as good environmental benefits and high power generation efficiency.Therefore,fuel cells are connected to MMC as a DC source to establish a high-power power generation system structure.Good application prospects and important significance.The research work carried out in this paper is as follows:First,the working principle of the fuel cell is deeply studied,and the fuel cell is connected to the Boost converter to build a DC source model.On this basis,combined with space vector modulation and traditional distributed power generation grid-connected system for research,and based on the traditional three-phase six Switching inverter power generation and grid connection model.Secondly,an in-depth theoretical analysis of the related topological structure,working principle and mathematical model of MMC was carried out.Focused on the MMC related modulation strategy,established a fuel cell voltage regulator controller,adding a PI controller to the Boost converter control system,boosting and ensuring the stability of the output voltage.Based on the research of the traditional MMC inner and outer loop decoupling control strategies,the inner loop controller is improved,and a fuzzy controller is added,so that when the power scheduling changes cause the system current to change,the controller parameters can be adjusted in time to ensure the stabilityof the system run.Finally,a MMC-based high-power fuel cell power generation and grid connection model was built in Matlab/Simulink.While verifying the correctness and effectiveness of the above control strategies,the traditional grid connection model was compared and analyzed,highlighting its large power level and flexibility High,low harmonic content and other advantages.Finally,the bridge arm circulating current is still dominated by the double frequency component in the structure of the high-power generation system.Based on this,the bridge arm circulating suppressor is built.Based on the analysis and research of sub-module faults,a redundant protection strategy is determined to ensure the normal operation of the power generation system.Finally,the controller is built in Matlab/Simulink.After simulation research,the effectiveness and superiority of the above-mentioned bridge arm circulation suppression strategy and redundant protection strategy are verified.