Digital Synchronization Method for Three Phase Systems

This article presents a digital signal processing method designed to obtain utility grid synchronism. This method is based on varying sampling frequency so as to generate sampling pulses in phase and at a frequency multiple of the main frequency. It is suitable for obtaining the reference in on-line power converters and for measuring harmonics in the utility grid. Even though it operates with a variable sampling frequency, a model in z-transform space is developed and contrasted with simulations. Design equations for a close loop controller which produces a response with no overshot are also developed herein.