A novel frequency-adaptive PLL for single-phase grid-connected converters

This paper presents a novel frequency-adaptive Phase-Locked Loop (PLL) for single-phase grid-connected power converters. The orthogonal component in the rotating reference frame is generated by a synthesis circuit which utilizes the detected amplitude and phase. It´s frequency-adaptive without using any additional circuits. Moreover, a special improved synthesis circuit PLL is proposed to make sure the PLL work well under low-order harmonics distortion condition. These structures are simple and easy implementation. In this paper, the method is analyzed and its performance is evaluated by both simulations and experiments.