A novel real-time magnitude and frequency estimation method using DFT zero-crossings

This paper presents a novel method for calculation of magnitude and frequency of single-phase voltage sources in hard real-time applications. It is developed for supervision of renewable power sources, both for converter and grid side. The method is based on Discrete Fourier Transform (DFT) of input signal, but it avoids the DFT errors due to off-nominal frequency operation. Steady-state error and second-harmonic oscillations in output signal are decreased within acceptable levels for all frequencies of interest. Accuracy of 20mHz for frequency and 0,2% for magnitude without harmonic content in input signal is obtained. The method described is applied on ARM7TDMI microcontroller platform and verified by experiments.