An Enhanced Transfer Delay Frequency Locked Loop Method for Single Phase Grid Voltage Synchronization

In this paper, an enhanced transfer-delay frequency-locked loop (ETD-FLL) is proposed to achieve grid synchronization for single-phase grids. Applying two transfer-delay units, a mathematic model is established to describe the integrated grid voltage in a linear regression form. Based on the proposed model, the ETD-FLL is proposed to estimate the frequency and phase angle. The proposed method has fast dynamics due to its TD-based structure. In addition, the usage of the integrator enhances the harmonic immunity of the proposed method. Finally, the experimental results show that the proposed ETD-FLL has good performance in terms of dynamics and harmonic immunity.