Adaptive Trust Region Method for Stochastic Estimation of Voltage Sags

The conventional stochastic estimation methods on voltage sags are difficult to satisfy the requirement of the power systems with distributed generation and power-typed loads.The paper proposes a stochastic approach estimating voltage sags based on adaptive trust region algorithm for ill-conditioned power flow calculation under faulty conditions,in which distributed generation resources and load model are taken into account.From the voltage tolerance curve of sensitive loads,quadratic interpolation is adopted to calculate the voltage sag domain and evaluation indices of point of common coupling(PCC) under four fault types,respectively.The IEEE test systems are adopted to test the proposed method,the results show that the proposed method is good at computing expected sag frequency(ESF) indices more accurately,and the adopted adaptive trust region algorithm has better capability in global optimization and computational efficiency.