Unified Modular State-Space Modeling of Grid-Connected Voltage-Source Converters

Abstract

This article proposes a modular state-space modeling framework for grid-connected voltage-source converters, where the different control loops, including the ac current control, the phase-locked loop, the dc-link voltage control, and the ac voltage magnitude control, can be modeled separately as building blocks. Moreover, the mathematical relationship between state-space models in the rotating (dq-) frame and the stationary (αβ-) frame is explicitly established, and, thus, the modal analysis can be performed directly in the αβ-frame, which allows intuitive interpretation of voltage and current oscillation modes in the αβ-frame. Experimental tests of a 3-kW back-to-back converter system validate the effectiveness of the unified modular state-space modeling and analysis.