A Frequency Locked-Loop with Reduced Tuning Complexity for Single-Phase Grid-Tied System with Inherent DC-Offset Rejection Capability

To ensure the high performance of grid-connected systems, a synchronization unit plays a crucial role. The frequency-locked loop (FLL) has gained popularity for the synchronization and control of grid-tied converters in recent times. The presence of DC-offset in the measured grid voltage deteriorates the performance of the FLL and also affects system dynamics. The Second Order Generalized Integrator (SOGI)-FLL is widely accepted among researchers. However, achieving high performance with the SOGI-FLL depends on fine-tuned parameters. The SOGI-FLL involves trade-offs between gains, so attaining the optimal design of the gain parameters leads to more complexity. This paper proposes a simple FLL structure to enhance the performance of the FLL and grid-tied converter control under DC-offset and grid disturbances. The proposed FLL has reduced tuning complexity and robust DC-offset rejection capability with enhanced dynamic performance.