Novel Phase-locked loop Method for three-phase power grid based on double complex coefficient filter via cross decoupling

The significance of the phase-locked loop lies in its role as a crucial method for controlling inverters to achieve grid-connected synchronization. However, the existing quasi-type PLL faces a notable issue: it exhibits inadequate resistance against interference, particularly during shifts in grid voltage frequency. This inadequacy leads to significant errors in both detection frequency and phase. To address this, our paper introduces a novel phase-locked loop. This innovative approach is built upon cross-decoupling double complex coefficient filters. We establish a comprehensive understanding by presenting its small-signal model. Moreover, we delve into the impact of filter parameters on dynamic response and provide insights into the digital implementation strategy. Importantly, our proposed phase-locking algorithm demonstrates consistent performance even under the most challenging power grid conditions. The efficacy of our approach is validated through simulations and experimental results.