Grid Synchronization and PLL for Distributed Power Generation Systems

Grid Synchronization is one of the key techniques for integration of distributed generation systems with high penetration of renewable energy sources into grid.In order to achieve the fast and accurate grid synchronization,a new phase-locked loop based on the crossing-decoupling frequency-adaptive complex filter was proposed.The operation principle was analyzed.Mathematical models in the frequency-domain and time-domain were built,which clarify the mechanism of decoupling the voltage positive and negative sequences.From the eigenvalue analysis point of view,the stability and dynamic performance were evaluated.The digital implementation method was also provided.In addition,its application to the single-phase system was discussed.Finally,the performance tests were carried out under the distorted and unbalanced grid voltage conditions.The experimental results verify the effectiveness of the proposed method.