Delayless Extraction of Instantaneous Symmetrical Components in Power System Fault Conditions

In addition to the originally defined complex symmetrical components in phasor domain, the instantaneous ones are essential for power system studies in the time domain. From the basic definition, the instantaneous symmetrical components (ISCs), the zero-sequence one excluded, would be accessible following a significant time delay, making limitations on fast-responding applications. This brief develops an analytic approach for delayless extraction of the ISCs from the phase quantities in fault conditions. It takes advantage of the superimposed value of quantities as well as the principles underlying the sequence networks so as to derive the positive- and negative-sequence components without introducing any time delay. The proposed approach serves as a powerful tool for the accurate and swift time-domain analyses of power systems in fault conditions. Simulation studies in PSCAD/EMTDC evaluate and confirm the effectiveness of the proposed approach.

I. Introduction

Multi-Phase power systems are designed and constructed in a way as to be structurally symmetrical with identical parameters on each phase. Typically, they are also operated in balanced conditions. There exist, however, likely situations in which power systems undergo the asymmetry or imbalance. All types of short circuit faults, the three-phase one exempted, conductors break, and uneven loading of the phases are the cases giving rise to the imbalance [1]–[5].