A Method of Measuring RMS Value of AC Signal Based on PWM

Abstract

The invention provides a PWM-based AC signal effective value measurement method. The method comprises the steps of (1) conducting the absolute conversion on a to-be-measured AC periodic signal v(t) to obtain |v(t)|; (2) generating a centrally symmetrical triangular wave vc (t) by a triangular wave signal generator; (3) subjecting vc (t) and |v(t)| to the PWM modulation treatment to obtain a corresponding PWM modulation signal (img file='DDA000093622208000011.tif' wi='128' he='62' / ); (4) converting the zero point of the signal |v(t)| into an edge pulse signal vp(t); (5) capturing the falling edge of the edge pulse signal vp(t) by means of a controller, measuring the period T of the vc (t) and the conduction time (img file='DDA000093622208000013.tif' wi='85' he='68' / ) of the (img file='DDA000093622208000012.tif' wi='98' he='61' / ), storing the obtained result in an array Ton[K], and calculating the effective value (img file='DDA0000936222080000014.tif' wi='592' he='148' / ) of the to-be-measured AC periodic signal v(t). According to the technical scheme of the invention, the effective values of all AC periodic signals v(t) can be calculated, particularly AC periodic signals including DC components and harmonic components. Therefore, the problem of DC components and harmonic components in to-be-measured signals can be effectively solved. As a result, the method is wider in application range.

Description

technical field [0001] The invention belongs to the fields of instrumentation, signal processing and measurement and control, and in particular relates to a method for measuring the effective value of an AC signal based on PWM, which is used for measuring the effective value of an arbitrary AC periodic signal. Background technique [0002] The effective value measurement of AC periodic signal plays an important role in the fields of instrumentation, signal processing and measurement and control, and is an important part of electrical parameter measurement. At present, the commonly used AC periodic signal RMS measurement is mainly divided into two schemes: hardware measurement and software measurement. The hardware scheme measures the effective value of the AC periodic signal based on the average value of |v(t)| Calculate the effective value of AC periodic signal v(t) This is because for a sinusoidal AC signal: Therefore, the effective value can be calculated by measuri...

AI Technical Summary

Problems solved by technology

However, this method has the following disadvantages: ①The method is narrowly applicable and only suitable for sinusoidal signals; ②The sinusoidal signal cannot have a DC component; ③The sinusoidal signal cannot have harmonics

This method can measure the effective value of any periodic signal, but it has the following disadvantages: ① In order to ensure the accuracy, a high-speed processor must be used to realize high-speed sampling and high-speed calculation, so the processor has high requirements; ② When calculating the effective value V rms N times of multiplication, N times of addition, 1 division and 1 square root operation of floating-point numbers are required, which will occupy a large amount of CPU system memory and running time, especially in occasions with high real-time requirements.

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