In order to meet the control requirements of micro-grid connection in distributed generation system, this paper introduces a method to extract the positive and negative sequence components of voltage signals in three-phase power grid as a tool for power grid signal processing and synchronization. The method based on multi-structure ANF can estimate the useful information of frequency, amplitude, fundamental wave and its orthogonal component of power grid signal. It also can detect the positive and negative sequence components of power grid system by using the information of fundamental wave and its orthogonal component, but when the amplitude or frequency of power grid signal changes, the performance of traditional multi-structure ANF method will be reduced. In this paper, an improved ANF structure is proposed by optimizing the dynamic equation of ANF, which has adaptability of frequency and amplitude. The improved multi-structure ANF is used to extract the positive and negative sequence components of power grid signals. MATLAB simulation results show that the proposed scheme has a high degree of anti-interference to the power system interference in the power grid signal. When the three-phase power grid signal is unbalanced, its frequency and amplitude estimation performance is better than the traditional multi-structure ANF positive and negative sequence extraction method.
