A grid synchronization technique based on a fractional-order complex-coefficient filter

In recent years, the complex coefficient filter (CCF) has received a lot of research attention in grid synchronization technology. However, a CCF-based phase locked loop (PLL) is basically similar to the PLL based on real coefficient filters in terms of mathematical models and dynamic performance. Thus, a three-phase PLL method with a front-up fractional-order CCF is put forward. First, by using fractional-order operators to construct a pre-stage filtering structure, pole assignment is used to determine the order’s value range, and it is shown that this structure can precisely separate the grid’s fundamental positive- and negative-sequence components. Secondly, linear mathematical modeling is conducted for fractional-order CCF-based PLL. The control performance of the entire PLL system is analyzed, with the third-order least resonance peak correction method being used to set up the controller’s parameters. Finally, simulations and comparative experiments are performed. The results show that the proposed PLL can deliver better dynamic indices and quality than the existing CCF-PLL during grid changes. © 2024 Power System Protection and Control Press. All rights reserved.