An improved phase coordinate method for fault analysis in inherently unbalanced power systems

The conventional symmetrical components fault analysis method may not be practically feasible in case of the analysis of simultaneous faults, especially in inherently unbalanced power systems because of the difficulties encountered in the assembly of sequence networks and their solution. To alleviate these problems, this paper presents a new algorithm for computer which is suitable for analyzing arbitrary complicated faults in inherently unbalanced power systems on the basis of multi-ports theory and transformed phase components. A common mathematical model for computer is developed that can be used to analyze all kinds of simple faults and complicated faults, including faults with various fault impedances in this algorithm. The effectiveness of the proposed method has been verified by theory analysis and programming calculations comparing with EMTP simulation results. In summary, the proposed algorithm is a general-purpose and flexible method for analyzing the arbitrary complicated faults of inherently unbalanced power system.