PLL based on extended trigonometric function delayed signal cancellation under various adverse grid conditions

Abstract

Phase-locked loop (PLL) plays an important role in the grid-connected converters. PLL should have the ability of filtering the harmonics under the non-ideal grid voltage. Recently, the signal cancellation technique is one of the advanced methods for filtering the harmonics. However, the existing signal cancellation techniques are not able to filter all harmonics by finite operators. This study proposes an extended trigonometric function delay signal cancellation (ETFDSC) to filter all harmonics completely under the adverse grid conditions. Furthermore, the proposed ETFDSC can be flexibly applied to eliminate the harmonic series fast under the various grid conditions. Consequently, a novel PLL based on the ETFDSC (ETFDSC-PLL) is designed to track the grid phase very accurately and fast. It is noteworthy that the grid phase can be extremely fast detected by proposed ETFDSC-PLL under some adverse grid conditions, especially under unbalanced conditions. Furthermore, the ETFDSC-PLL is self-adjustable to the fundamental frequency deviations, and the excellent filtering capability and fast dynamic response can be achieved, even under large frequency variations. Finally, the simulation and experimental results are presented to validate the filtering capability and transient performances of the proposed PLL.