Resonance Suppression Method Based on Virtual Filter for Grid-Following and Grid-Forming Converter Interconnected Systems

With the advancement of power electronics technology, converters achieve compactness and high power density by increasing switching frequency and reducing passive components. However, this compromises the filtering capability to suppress high-frequency harmonics and intensifies high-frequency resonance issues in multi-machine interconnected systems. The problem becomes even more complex in grid-following (GFL) and grid-forming (GFM) converter interconnected systems due to their distinct dynamic characteristics. Traditional active damping methods fail to effectively mitigate such high-frequency resonances. For GFL converters, this paper investigates the interaction mechanisms between various active damping techniques and high-frequency harmonics, and proposes a virtual-filter-based active damping method that feeds back capacitor voltage through a quasi-resonant controller. This approach effectively suppresses high-frequency resonance, maintains high control bandwidth, and avoids the drawback of conventional capacitor-voltage feedforward, which tends to amplify high-frequency disturbances. For GFL-GFM interconnected systems, the paper further analyzes how different active damping strategies affect system damping characteristics and the interaction between GFL and GFM converters, leading to a rational active damping configuration. The proposed scheme successfully suppresses high-frequency resonance while preserving fast dynamic response, with experimental results confirming its effectiveness and feasibility.