Grid Voltage Synchronization for Unbalanced Voltages Using the Energy Operator

This paper presents a novel synchronization technique which can identify the grid voltage frequency and phase angle under unbalanced grid voltage conditions. The method combines the features of two different energy operator (EO) schemes: the basic one for estimating the frequency of the grid voltages and the cross-EO for phase tracking. Using a moving data window of five samples, the algorithm can track the fundamental frequency and phase angle quickly and accurately. This paper discusses the fundamental principles of the method, highlights its features and filter requirements in implementation. An experimental implementation of this method is presented, which validates its performance for practical operation. The ability of the proposed method to enable a static compensator (STATCOM) riding-through unbalanced grid voltage condition is verified by the results from a power network simulation study.