Coordinated LADRC and GPOA-P&O MPPT for Robust Fault Ride-Through and Power Stability in Grid-Connected PV Systems

Grid-connected photovoltaic (PV) systems require low-voltage ride-through (LVRT) to function reliably, particularly in the presence of symmetrical and asymmetric disturbances. Conventional PI-based control systems occasionally show limited resilience, particularly in the presence of distorted or imbalanced grid voltage. This paper proposes an enhanced LVRT control strategy for three-phase grid-connected PV systems by integrating a new rapid indirect Global Peak-Oriented Adaptive P&O MPPT method, referred to as (GPOA-P&O), with LADRC and DSOGI-FLL synchronization. The GPOA-P&O algorithm improves maximum power tracking by identifying the global peak and avoiding local maximum points, thereby reducing power fluctuations. Meanwhile, the cascaded LADRC controllers provide accurate voltage and current regulation, effectively suppressing DC-link overvoltage during grid disturbances. DSOGI-FLL ensures accurate positive-sequence phase-locking, enabling compliant reactive current injection even under severe voltage asymmetry, in accordance with grid-code requirements. The proposed method also eliminates second-order power oscillations and maintains constant inverter current regardless of fault severity. Case studies in 2024a MATLAB/Simulink and hardware-in-the-loop experimental platform demonstrate superior stability, fault ride-through capability, and grid-support performance compared to conventional approaches such as PI control and optimized SCSO-tuned PI.