The Effects of Integration Intervals on Recursive RMS Value and Power Measurement in Nonsinusoidal Conditions

The effects of integration intervals on recursive rms value and power measurement in the presence of nonsinusoidal conditions are considered. The presence of time measurement intervals of both fixed and variable durations is assumed. Suitable formulas to evaluate the errors introduced by the desynchronization of measurement interval for active and apparent powers, power factor, and voltage and current rms values are developed; formulas accounting the contributions to the error of the cross products between couples of components at different frequencies are also developed. Then, the errors are evaluated in the presence of smoothing of the results over a variable number of consecutive measurements by means of proper formulas. Some numerical and experimental case studies conclude the analysis showing the effects of the different contributions to the error and the improvements of accuracy that can be obtained by smoothing the results.