Simple and robust PLL algorithm for accurate phase tracking under grid disturbances

Phase-locked loops (PLLs) are commonly used for the synchronization of grid connected power converters. However, the standard PLL structures are not able to reject grid disturbances such as voltage harmonics, unbalances or DC components in the measured voltage. Since the response of the power converters depends on the grid phase tracking, it is necessary to ensure an accurate synchronization even under distorted conditions. This paper proposes an enhanced PLL structure, which is able to perform fast synchronization even under weak grid conditions and frequency variations. Due to its low computational burden, the proposed PLL allows its implementation on low cost microprocessors.