One cycle AC RMS calculations for power quality monitoring under frequency deviation

Measuring and monitoring quality parameters of AC power systems requires several calculations, such as RMS values of voltage and current. These calculations are performed with samples of the monitored waveforms, at a sample frequency equal to N times the nominal frequency of waves. Conventional algorithms regard N as a constant integer. When the actual frequency has a deviation from its nominal value, errors are introduced in the calculations, and averages are used over several cycles to reduce these errors. However, for instantaneous quality parameters, these calculations must be performed every cycle for quick disturbance detection; averages are impracticable. The purpose of this article is to introduce a method to minimize these errors making N variable and a noninteger.