Research on AC–DC High‐Frequency Interaction Mechanism and Valve‐Side High‐Frequency Oscillation Suppression Strategy of Flexible HVDC Converter

High‐frequency oscillation phenomena in flexible high‐voltage direct current (HVDC) transmission systems significantly compromise operational reliability in major power infrastructure projects. This study addresses the critical gap in device‐level high‐frequency interaction mechanisms by developing a comprehensive AC–DC high‐frequency model for flexible DC converter valves using convolution Fourier series analysis. The research establishes quantitative relationships between DC voltage oscillations and system parameters, identifying that high‐frequency harmonics in converter valve pole voltage are primarily influenced by high‐frequency control components, module voltage ratings, line parameters, and valve currents. A novel hardware solution integrating a DC matching reactor designed for impedance matching with AC reactance is proposed, avoiding modifications to existing system parameters. This approach is complemented by a dual‐strategy control scheme combining switching frequency optimization and active damping techniques. Experimental validation using a 7‐module physical test system demonstrated that the hardware solution reduced high‐frequency harmonics by approximately 50% when impedance matching conditions were satisfied. Real‐time simulations of a ±420 kV HVDC system further confirmed the effectiveness of the combined approach, reducing total harmonic distortion from 5.74% to 0.80% while decreasing power module switching frequency from 1500 Hz to 120 Hz. The high‐frequency modeling framework and suppression strategies presented in this study provide substantial improvements in both theoretical understanding and practical mitigation techniques for high‐frequency oscillations in flexible HVDC systems, offering enhanced stability for modern power transmission infrastructure.