The development and the application of fast decoupled load flow method for distribution systems with high R/X ratios lines

An improved Fast Decoupled Load Flow calculation method for distribution systems with high R/X ratio is proposed. This method is based on a coordinate transformation in Y-matrix for Jacobian matrix in the load flow method. The biggest advantage of so-called Fast Decoupled Load Flow(FDLF) method over the conventional Newton-Raphson method is the short computation time for large power systems which is achieved by the reduced size of Jacobian matrix. However, it is said to worsen convergence characteristics for distribution systems with lines of high R/X ratios compared to the conventional Newton-Raphson method. In order to overcome the problem, the authors employed a coordinate transformation in Y-matrix of the Fast Decoupled method. Better convergence processes in the improved Fast Decoupled method are demonstrated and some discussions are given in case of the analysis of the distribution systems with high R/X ratio lines.