中文摘要：

传统对称分量法在频域中定义，用相量表示，需要计算变量的模值和相位，故只能应用于电力系统不对称故障的稳态分析，而不能对暂态过程中的电量进行分析。针对该问题，提出一种基于时域测量量的改进瞬时对称分量法，并给出了相关计算公式和结果。所提方法的基本原理是利用三相电压或电流的瞬时值构造一个无延迟的旋转相量，并以复数的形式直接计算三相电量的正序、负序和零序值。由于该算法简单，不需进行三角函数计算，计算速度较快，实时性好，易于在工程上的实现。基于瞬时对称分量理论，提出了一种新型的正、负序电流检测方法，并用PSCAD／EMTDC仿真软件进行了验证，结果表明所提方法是正确、可行的。

英文摘要：

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.