Frequency-adaptive voltage sequence estimation for grid synchronisation

Grid synchronisation is one of the most important issues for integration of distributed generation into the grid. A challenge for grid synchronisation is how to quickly and precisely estimate the fundamental positive and negative sequence voltages under distorted and unbalanced conditions. A decoupled double complex-coefficient-filter based grid synchronisation method is proposed. It has a very simple structure, and can achieve the accurate and fast estimation of the positive and negative sequences from the polluted grid voltage in a frequency-adaptive way. Experimental results verify the theoretical analysis and the effectiveness of the presented method.