An Elliptic Model-Based Fast Estimation Method of Positive and Negative Sequence Amplitudes for Unbalanced Grid Voltages

In this paper, a novel elliptic algebraic model-based positive- and negative-sequence amplitude estimation method is proposed for unbalanced grid voltages. By exploiting the intrinsic elliptic trajectory of unbalanced voltage vectors in the αβ stationary reference frame, an explicit algebraic relationship between the sequence amplitudes and the elliptic geometric parameters is established. Consequently, the conventional sequence decomposition problem is reformulated as an elliptic parameter identification problem. Based on the proposed elliptic algebraic framework, an online parameter identification scheme is developed to estimate the elliptic parameters and reconstruct the sequence amplitudes. A Lyapunov-based global asymptotic stability analysis is also presented to verify the convergence property of the proposed identification framework. Experimental results further validate the effectiveness of the proposed method.