Application of Simulink for Simulation of the RMS Measurement Method Based on Low-pass Filtration

Abstract

Nowadays one of the most popular methods for the root square value (RMS) measurement is an approach based on low-pass filtration of squares of input signal samples. This method allows to measure RMS values of sinusoidal and polyharmonic signals. The simplicity of implementation, the low value of the methodological error, can be attributed to the advantages of this method. The methodological measurement error is determined by the parameters of the output low-pass filter - by the values of its frequency characteristics. The objective of this article is to search for options for constructing an output filter that allows to ensure a low value of the RMS measurement error with a low implementation complexity. There were obtained analytical relationships that allows to evaluate the influence of filter parameters on the RMS measurement error of the sinusoidal input signal. An estimate of the influence of the frequency deviation of the input signal on the RMS measurement error is also obtained. Different types of digital filters were considered: Butterworth, Chebyshev I type infinite impulse response (IIR) digital filters, a filter with a Kaiser window and a moving average filter. The application of a moving average filter is considered in more detail. A technique is proposed for determining the order of a filter of this type to minimize the RMS measurement error. Estimates of the RMS error are applied to the signals of real electric power networks by simulation modeling in Simulink software package. The obtained analytical dependences are confirmed by the coincidence of the results of simulation and analytical modeling at check points.