This study examines flexible interconnection technologies for medium-voltage distribution grids to improve the power supply reliability of radial lines in order to meet the challenges posed by the high percentage of new energy access and the growth of electric vehicle loads. The study improves the reliability and flexibility of the grid’s power supply by establishing efficient interconnections, with a particular focus on the application of power electronics to enhance the operational efficiency of the grid. This article talks about the creation and use of boosted back-to-back voltage source-type converter (B2B VSC), multilevel converter (MMC-type) B2B VSC, and series-compensated current controller (DUPFC) technologies, as well as how they are used in distribution grids. A multi-objective optimization model of flexible internet configuration under the constraints of system and equipment parameters is constructed with the objectives of improving the power supply reliability of 6 kV radial lines and balancing the line loading ratio as the flexible trend control objective, and the effects of three typical control strategies, namely, the current inner-loop control, the voltage outer-loop control, and the power outer-loop control, are evaluated through experiments. Among them, the voltage deviation of the system and the total active network loss throughout the day have been reduced by about 21% and 46%, respectively, compared to the initial system under power outer-loop control. The experimental results show that flexible interconnection technology can effectively improve the reliability of power supply lines, increase the grid’s access capacity to new energy sources, and optimize load distribution. In addition, the application of such technologies helps the grid transform from the traditional passive access mode to a smart grid that can actively regulate and optimize energy flows, laying the foundation for achieving green and low-carbon development goals.