Active Power Measurement Accuracy Increasing by Additional Measurement of Shunt Voltage

Abstract

The broadband transfer power wattmeter with the correction of the own consumption error for measuring the active power against the background of large reactive components in the radio frequency range is considered in article. The objects of research are electromagnetic elements (chokes / transfor­mers), operating at high frequencies and have strongly distorted forms of signals. When measuring at high frequencies, the channels of the wattmeter become very sensitive to phase errors. It is necessary to minimize links that cause phase shifts. In this connection, it is important to correctly construct the input units of the wattmeter and to make such a transformation, which will provide operations with signal rms valueswithout links phase shifts. The proposed scheme allows this to be achieved, and required gain is carried out without taking into account the phase shift of the signals. In the basic scheme of the wattmeter(fig. 1), the input device is executed from the main shunt and parallel to the auxiliary distributed shunt connected to it, which is connected to the main resistance of the voltage divider, in which the value of all resistances of the input device is determined by conditions of invariance to the squares of the voltage and load current , and the partially distributed auxiliary shunt is calculated with additional weighting factors to provide the conditions for invariance of the squared of voltage and current and eliminate the error from its own revives. Features of the construction of the input link of the wattmeter of transfer power with additional measurement of shunt voltage are given in the article(fig.2). Active power with taking into account the influence of the shunt reactive component calculation formulas (7)-(14)is presented. The basic error of the wattmeter is the error of the low-ohm shunt. It is expedient to use coaxial or triaxial shunts to extend the frequency range. Transfer power wattmeter input link, which contains additional measurement of shunt voltage simulations was performed in the article(fig.3and table 1). The advantages of such wattmeter are: possibility to expand the frequency range by taking into account shunt resistance reactive component influence on the measurement final result , which can be achieved not only by hardware (shunt inductance reduction), but also the introduction of the calculated correction after measuring the values of the shunt active and reactive component; the values of the input device elements can be optimized by the criterion of maximum broadband, since the error from own consumption is taken into account; in the scheme one low-level shunt is used, which reduces the cost of the wattmeter; additive errors of the voltage conversion channel are minimized.

Keywords

• power measurement, active power, radio frequency range, phase noise, correction of own consumption errors, losses, shunt.