Analysis and Suppression of Characteristic Harmonic Amplification in LCC Sending-End Converter Stations Based on s-Domain Nodal Admittance Matrix

To address the harmonic amplification problem caused by the injection of characteristic harmonics into the AC side of an LCC sending-end converter station, this paper proposes a resonance localization and suppression method based on the harmonic amplification theory and the s-domain nodal admittance matrix. First, a frequency-domain nodal admittance matrix model of the AC-side system is established. Resonance mode analysis is performed to obtain the potential resonant frequencies, damping levels, and nodal voltage mode shapes, thereby identifying the risk frequency bands and sensitive nodes for characteristic harmonic amplification. Second, the nodal impedance matrix is obtained by inverting the nodal admittance matrix, and the mutual impedance characteristics between the harmonic source and various nodes, as well as the propagation and amplification mechanism of characteristic harmonics in the AC network, are analyzed. Third, a parameter perturbation method is adopted to analyze the influence of key electrical parameters on harmonic amplification, providing a basis for sensitive component identification and mitigation measure design. Finally, a C-type damping filter is installed at the identified resonance-sensitive nodes to suppress the resonance. The results show that the proposed method can effectively characterize the frequency-domain resonance characteristics of the AC side of the converter station, and the C-type damping filter can reduce the impedance peak in the target frequency band and enhance system damping, thus effectively suppressing characteristic harmonic amplification.