An Improved Method of Instantaneous Symmetrical Components and Its Detection for Positive and Negative Sequence Current

Abstract

The definition of traditional symmetrical components is based on the concept of phase in which magnitudes and phases are needed during the computation. Hence,it is only suitable for steady-state analyses of unbalanced faults and systems. To solve this problem,this paper presents a new method to calculate the instantaneous symmetrical components in time-domain,and gives its corresponding equations and results. The principle of the proposed instantaneous symmetrical components is based on the rotary phases which are calculated by use of three phase instantaneous variables. As a result,positive,negative and zero sequence components can be obtained. Additional advantages of the proposed method include:without triangular function calculation,good real-time performance. With rapid computation speed,the method is suitable for the application of practical engineering. As an example,the proposed method is used for the detection of positive and negative sequence current for an unbalanced three phase power system. The simulation results verify the correctness of the proposed method.