Method and apparatus for efficiently computing symmetric sequence signals in a three phase power system

摘要

A real time three-phase analyzer stores digitized values of the signals of the three-phase circuits in memory so that they may be addressed according to circuit and sample number. Positive, negative and zero phase sequences are developed without the need for trigonometric calculation by combining samples offset in memory by a number of samples approximating 120 DEG . That number of samples may be determined for an arbitrary frequency of the three-phase system by identifying zero-crossing points of one such signal and assuming the number of samples equates to 360 DEG of phase of that circuit. The phase sequence of the three circuits necessary for the calculation of the positive, negative and zero phase sequences may be determined by comparing the relative position of positive going zero-crossings for each of the three circuits.