Optimization study of DC flexible control strategy based on frequency response and voltage characteristics of AC system

• Traditional DC transmission systems often ignore grid status and converter capacity during power allocation, impacting stability. • This study focuses on optimizing DC flexible control strategies based on AC frequency response and voltage characteristics. • The topology of flexible DC systems is analyzed, clarifying AC-DC and DC-AC conversion optimization strategies. • The AC node power correction equation is integrated into the AC system model to extract frequency and voltage characteristics, enhancing droop control. • Experimental results show improved frequency and voltage stability, reduced power exceedance probability, ensuring DC system stability. In order to address the instability issues in traditional direct current (DC) transmission systems caused by their independent operation from alternating current (AC) systems, this study proposes an optimized control strategy for Flexible DC transmission by integrating AC system frequency response and voltage characteristics. Through topology analysis of the Flexible DC system, optimized control strategies for AC-DC and DC-AC conversions are developed, utilizing an inverter module for flexible power transmission logic and incorporating an AC node power correction equation into the AC system model.This approach refines droop control by dynamically adjusting to frequency and voltage variations. Experimental results demonstrate enhanced power transfer capability of Modular Multilevel Converter 1 (MMC1), reduced risk of Modular Multilevel Converter 2 (MMC2) exceeding capacity, and significant improvements in system frequency and voltage stability, validating the effectiveness of the proposed method.