A nonlinear adaptive synchronization technique for grid-connected distributed energy sources

This letter introduces a new adaptive notch filtering (ANF) approach as a powerful tool for synchronization of converter-interfaced distributed generation systems that can potentially stimulate much interest in the field and provide improvement solutions for both grid-connected and stand-alone (islanding operation) modes of micro-grids. The proposed technique is simple and offers a high degree of immunity and insensitivity to power system disturbances, harmonics and other types of pollution that exist in. the grid signal. A modified structure of the ANF-based synchronization technique is capable of decomposing three-phase quantities into symmetrical components, extracting harmonics, tracking the frequency variations, and providing means for voltage regulation and reactive power control. A prominent advantage of the proposed scheme is that it does not require a phase-locked loop for the synchronization. In addition, this very simple and very powerful power signal processor will simplify the control issues currently challenging the integration of distributed energy technologies onto the electricity grid. All converter-interfaced equipment, such as flexible ac transmission systems, custom power controllers, and active power filters, will benefit from this technique. Theoretical analysis is presented and the performance of the method is evaluated through simulation.