“…Methods based on signal low-pass filtering for fundamental power measurements overcome the intrinsic downsides of methods that are based on the Fourier transform [6], which require adjustment of algorithms if the power frequency varies, e.g. resynchronisation of the sampling frequency [5,6] or software resampling [15] and the subsequent usage of the fast Fourier transform (FFT). Moreover, the re-synchronisation of the sampling frequency always take place awhile after the actual power frequency changes [16], which is hardly accurate in systems with a continuously varying frequency, like in microgrids [17,18].…”