A Control Scheme to Enhance Low Voltage Ride through and Current Limitation under Unbalanced Faults for Seven-Level Three-Phase Grid-Connected PV Inverters

This study emphasizes photovoltaic (PV) systems integration with the grid, underscoring the importance of robust control strategies for ensuring power quality and voltage stability during grid faults. It introduces an innovative approach to enhance Low Voltage Ride Through (LVRT) in a three-phase seven-level PV inverter, especially during unbalanced faults. Grid disturbances often compromise inverter performance, affecting power quality through non-sinusoidal current injection during voltage sags, leading to double-frequency components in active and reactive power. Multi-level inverters are favored for their benefits, such as decreased harmonic distortions, less electromagnetic interferences, as well as increased DC link voltage. The proposed strategy ensures sinusoidal current during unbalanced grid faults, uses efficient current limiting, employs a power tracking algorithm for the DC/DC converter, and enhances the seven-level inverter with a voltage inverting component. MATLAB simulations validate its efficiency in improving LVRT, reducing harmonic distortion, and overall performance during unbalanced grid faults, enabling stable PV integration while preserving grid power quality.