Based on the dilemma of analyzing the resonance stability of AC power grids using impedance models, it is demonstrated that the “negative resistance” mechanism of wideband oscillation is untenable. A general method for describing power electronic devices using wideband voltage-source converter models and wideband current-source converter models is proposed, thereby representing the nonlinear characteristics of power electronic devices with harmonic voltage sources and harmonic current sources. This allows the renewable energy power system to still be described by a linear system, and interprets the mechanism of wideband oscillation as a “harmonic amplification” phenomenon caused by network resonance, thus establishing a new framework for explaining the mechanism of wideband oscillation in renewable energy power systems. Through the analysis of two basic resonant circuits, the relationship between the damping ratio of resonant modes and the harmonic amplification factor is derived, laying a theoretical foundation for the analysis and suppression of wideband oscillation based on the s-domain nodal admittance matrix method and C-type damping filters. Based on the maximum damping criterion, a design method for C-type damping filters is proposed. The designed C-type damping filters exhibit strong broadband damping effects.
Zheng Xu (Wed,) studied this question.