The Measurement of the RMS Instantaneous Power for the Power Distortion Evaluation

Abstract

The measurement of both electric power and energy, especially in non sinusoidal conditions, is today a still open research problem in the metrology community. Harmonic distortion, noise, transients, over-voltages and voltage dips have increased the difficulty in achieving accurate measurements. Besides, many of non-active power component definitions that have been proposed cannot be implemented in the traditional electro-mechanical or solidstate meters. This paper goes on to investigate about the possibility to process the instantaneous power signal when harmonics are likely to occur. The intent is not to resolve theoretical controversies, but instead to investigate about the possibility to easily process the instantaneous power signal in order to reduce the meter cost.Specifically, in the paper the measurement of a power parameter A*, which is sensible to the harmonic interferences with the fundamental component of the instantaneous power, is proposed. This parameter can be adopted for the development of a simplified single-phase electric energy meter able to operate in non sinusoidal conditions and to supply distortion information. Additionally, some simulation results are proposed, to confirm the applicability of the proposed measurement technique.

Survey about Classical and Innovative Definitions of the Power Quantities Under Nonsinusoidal Conditions

“…In [22,23], a new approach for the definition of power quantities has been discussed, by adopting instantaneous power waveforms for the definition of apparent power and reactive power. A different definition of S is proposed; by introducing the measurement of P rms , it allows the evaluation of the actual power waveform features, avoiding losses of information related to the absence of the harmonic phases in the traditional definition of S. In contrast to S, which is directly obtainable from the p(t) waveform only under sinusoidal conditions, AS can be derived from p(t) under all conditions.…”

The measurement of actual apparent power and actual reactive power from the instantaneous power signals in single-phase and three-phase systems

“…As previously demonstrated [14], there is no direct relationship between the variations in apparent power and instantaneous power fluctuations in the presence of harmonic distortion. The measurement of the rms value of the instantaneous power under nonsinusoidal conditions as a possible index of harmonic distortion has been analyzed for adoption in low-cost power quality measuring devices [15]. Based on the above considerations, in this manuscript, the instantaneous power waveform has been investigated, focusing on the quantities that can be directly measured by processing it.…”

Comparison of calorimetric and electrical loss measurement methods in a frequency converter research and development application

“…In [5] a simplified system for calorimetric measurement is presented. The difficulties in measurement of non-sinusoidal power quantities are discussed in [6]. The known problem with shunt resistor phase shift is studied in [7].…”