Enhancement of a frequency estimation algorithm and its application to harmonic and flicker measurements

Frequency is an important index to represent electric power system quality, and it is often used to improve the accuracy of harmonic, flicker and inter-harmonic calculation for a distorted voltage waveform. Since the existing frequency calculation algorithms have some different problems, this paper proposes a scheme to enhance the algorithm of demodulation of two complex signals. This algorithm can be easily applied to a single-phase circuit, and its performance is first tested and validated by different synthesized waveforms including harmonic, flicker, and noise. Then, it is incorporated into a hybrid digital algorithm to improve the overall performances of a virtual instrumentation system for harmonic and flicker measurements. Field test results show that the algorithm is less sensitive to noise interference, and it also spends less calculation time than the original method.