Impedance Decomposition for Design-Oriented Analysis of Grid-Forming Voltage-Source Converters

Abstract

<p>Grid-forming voltage-source converters (VSCs) tend to suffer from sideband oscillations in stiff grids. Conventional state-space eigenvalue analysis or impedance-based stability analysis based on generalized Nyquist stability criterion can only analyze how specific control parameters affect the overall system stability, which ends up with less insight into a controller design-oriented analysis. To tackle this challenge, this article starts with the impedance modeling and stability analysis of grid-forming VSCs in stiff grids. Then, an impedance decomposition approach to characterizing the impacts of multiple control loops is proposed, which benefits in a controller design-oriented analysis for stability enhancement. Finally, simulation and experimental results are provided to validate the approach.</p>

Review of Small-Signal Converter-Driven Stability Issues in Power Systems

“…11. That means the SSO instability tends to happen in a strong grid under the same droop gains in voltage-type VSCs, which coincides with results in [36,62].…”

“…To limit the scope of this paper, the dc-link dynamics are ignored considering only the dc/ac and ac/dc stages. [36,37]. 3.…”

“…It is found that the voltage-loop will make the converter prone to be less damped and lose system stability more easily since the stable region is reduced with inner V-I control. Besides, it is found in [36] that a larger voltage control bandwidth may enhance system SSO stability. Additionally, the Q-v droop impact on system stability is weaker than the p-f droop.…”