Phasor estimation methods in the presence of harmonics and noise: A comparative analysis

Abstract

Frequency is an important parameter that plays a crucial role in the monitoring, protection and control of power system. It provides an indication of the interconnection's generation/load balance. Normally nominal frequency is either 50 Hz or 60 Hz in most of the countries. Any deviation of frequency from nominal is an indication of abnormal condition or generation/load imbalance. Synchronized phasor measurement unit (PMUs) are providing a promising future for accurate phasor and frequency estimation. Initially Synchrophasor estimation was the main thrust and after amendments in IEEE standards researchers could able to provide solution for frequency and rate of change of frequency (ROCOF) estimation. The main concern now is to achieve accurate, fast, less computationally complex and economic frequency and ROCOF estimation algorithm. So far different algorithms have been proposed for commercial PMUs and are being claimed as in compliance with IEEE standards C37.118.2011. These standards are providing benchmark for justifying accuracy of commercial PMUs. For effective monitoring and control of these PMUs, their operation under transient and large dynamic oscillation demands quick and highly accurate estimation without any discrepancy in estimated phasor value, irrespective of different manufacturers. This paper presents a comparative analysis of fundamental phasor estimation algorithms namely Basic FFT, Recursive DFT and Non-Recursive DFT under normal operating condition and in presence of noise and harmonics.