A NOVEL CASCADED PASSIVITY-BASED CONTROL APPROACH FOR LCL GRID-CONNECTED CONVERTERS IN UNBALANCED NETWORKS

Abstract

Grid-connected converters are essential components in renewable energy systems such as photovoltaic (PV) systems, wind energy conversion systems, and smart grid applications. The increasing penetration of renewable energy sources into modern power systems introduces challenges related to power quality, harmonic distortion, and grid instability, especially under weak and unbalanced grid conditions. LCL filters are commonly used in grid-connected converters to reduce current harmonics and improve power quality. However, conventional control strategies often face stability and resonance problems under unbalanced network conditions. This paper proposes a novel cascaded passivity-based control approach for LCL grid-connected converters operating in unbalanced networks. The proposed method enhances system stability, suppresses harmonics, improves dynamic response, and maintains robust performance under weak grid conditions. The control strategy integrates passivity-based current control with cascaded voltage regulation to ensure stable power transfer and effective damping of LCL resonance. Simulation and analytical studies demonstrate that the proposed approach significantly improves converter performance compared to traditional proportional-integral (PI) control methods