Robust Line-Voltage Sensorless Control and Synchronization of LCL -Filtered Distributed Generation Inverters for High Power Quality Grid Connection

This paper presents a robust control scheme for high power quality grid connection of inductor-capacitor-inductor (LCL)-filtered distributed generation (DG) inverters. The presence of the LCL filter complicates the dynamics of the inverter control system, particularly when the uncertain nature of the grid background distortion and system parameters is considered. The proposed scheme addresses such practical difficulties by providing: 1) robust and simple active damping control performance under grid and filter parameter variation; 2) suppression of grid-induced distortion without a-priori knowledge of the grid background distortion and unbalance via real-time generation of the frequency modes and disturbances that should be eliminated from the closed-loop current control system; 3) robust deadbeat digital control performance that maximizes the dynamic performance of the converter; and 4) robustness against interaction dynamics between active damping and current tracking controllers. Furthermore, the proposed control scheme facilitates line-voltage sensorless current control and grid-synchronization performance, which enhances the reliability and cost measures of the DG interface. Theoretical analysis and comparative evaluation results are presented to demonstrate the effectiveness of the proposed control scheme.