Digital Filter Performance for Zero Crossing Detection in Power Quality Embedded Measurement Systems

Power quality analysis involves the measurement of quantities that characterize the power supply waveforms such as RMS value, frequency, harmonic and inter-harmonic distortion or the presence of transients. The measurement of these quantities is regulated by internationally accepted standards from IEEE or IEC. In particular, for the evaluation of frequency and RMS values, the standard suggests the detection of the waveform zero crossings. Thus, accurate zero crossing detection is of utmost importance in power quality measurements. The undesirable effects of noise, harmonics and transients can be mitigated by filtering of the acquired waveforms, which induces a frequency dependent delay in the processed waveforms. This paper presents a comparative analysis between two types of filters. A comparative analysis is performed between the use of a fixed nominal delay and a frequency corrected delay. Additionally, the effect of the presence of noise and harmonics in the delay compensation is presented