International standards from IEC and IEEE regulate power grid parameters such as the RMS value, frequency,
harmonic and interharmonic distortion, unbalance or the presence of transients, that are important to assure
the quality of distributed power. Standard IEC 61000-4-30 suggests the zero crossing algorithm for the
measurement of the power grid frequency, but also states that different algorithms can be used.
This paper proposes a new algorithm, the Fractional Interpolated Discrete Fourier Transform, FracIpDFT, to
estimate the power grid frequency, suitable for implementation in resource limited embedded measurement
systems. It is based on the non-integer Goertzel algorithm followed by interpolation at non-integer multiples
of the DFT frequency resolution. The proposed algorithm is validated and its performance compared with
other algorithms through numerical simulations. Implementation details of the FracIpDFT in an ARM
Cortex M4 processor are presented along with frequency measurement results performed with the proposed
algorithm in the developed system.