Harmonic Transfer-Function-Based Impedance Modeling of a Three-Phase VSC for Asymmetric AC Grid Stability Analysis

摘要: Impedance modeling and stability analysis of a grid-voltage source converters (VSC) system under symmetric ac grids have been extensively discussed in the literature, where dq domain impedances are usually adopted. As for asymmetric grids, impedance is no longer straightforward due to presence negative sequence components, linearization will result linear-time-periodically-varying system, making frequency-domain intractable. One way address this issue would be harmonic-transfer-function (HTF) approach. Although method conceptually clear, its application an unbalanced grid-VSC still challenging effective model missing here, therefore paper aims bridge gap. First, modeled HTF framework. Then HTFs truncated into four-by-four matrices by exploiting property frequency couplings. Based on this, equivalent load Nyquist-based established, they thoroughly verified measurements as well accuracy analysis. Finally, several concerns feasibility models grid clarified.