A Weighted Average Iteration Method for Improving Convergence of Short-Circuit Current Calculation with Controlled Current Source

Abstract

With the rapid development of renewable energy power generation represented by wind power and photovoltaic, the traditional short-circuit current calculation method based on the equivalent impedance has encountered challenges. Due to the existence of a high proportion of controlled current sources, the equations for short-circuit current calculation are nonlinear and need to be solved by iteration, but the iterative convergence of short-circuit current calculation is an important problem. To improve the iterative convergence, a weighted average iteration method is proposed in this paper. The calculation formulas of short-circuit current are redefined by replacing the open circuit voltage with the equivalent voltage source, which is related to mutual impedance and characteristics of the controlled current sources with control strategy. The iteration process using weighted average method is introduced, which achieves a balance between the current temporary expected value and the historical iteration value. Through a lot of short-circuit calculation and analysis based on actual power system data, the effects of different weighted average factors are compared in detail. It is proved that different weighted average factors have no obvious influence on the accuracy of the results but have a significant influence on the convergence. The final optimum factors that are sufficiently effective for improving the iteration convergence are recommended.