Multi-functional low voltage ride-through control strategies for grid-interfaced solar power plants: A comprehensive review

Low-Voltage Ride-Through (LVRT) is a feature allowing grid-connected photovoltaic inverters to remain in operation when voltage drops momentarily, by actively maintaining grid voltage through controlled reactive power injection. With the rise in PV penetration, LVRT has evolved into a requirement for protection, as well as crucial grid support, as mandated by stringent international grid codes. These codes emphasize the importance of reactive current, inverter current limiting, and rapid post-fault power recovery. The number of LVRT methods reported over the last decade is numerous; however, the reviews published so far have not conducted an exhaustive evaluation of the current advances in sequence control, current-reference generation, and combined voltage support. This work presents a systematic overview of the current state of the art in LVRT control strategies for grid-interfaced PV systems, examining recent developments. This review primarily focuses on control strategies for grid-following (GFL) photovoltaic inverters, which represent the prevailing architecture in present-day utility-scale and distributed PV systems. Firstly, the review aims to summarize and compare international LVRT grid-code requirements, highlighting their significance for inverter control design under both balanced and unbalanced faults. Secondly, the paper discusses more sophisticated voltage sag detection and synchronization schemes, including improved phase-locked loop methods and PLL-free methods, comparing them in terms of fault detection rate, sequence decoupling, and harmonic immunity. Thirdly, a structured taxonomy of current reference generation strategies is presented, covering reactive-current-priority control, current-constrained formulations, sequence-adaptive injection, voltage-support-oriented control, and power-oscillation mitigation techniques. The review further discusses DC-link voltage regulation schemes, PV-energy storage-assisted LVRT architectures, and inverter topology considerations. Finally, recent advances in Model Predictive Control (MPC), AI-assisted, and hybrid multi-objective controllers for grid-following PV inverters are analyzed, supported by insights from experimental, and real-time simulation (RTS) validation studies. The paper identifies key technical gaps and outlines future research directions to achieve resilient, grid-compliant PV systems.