Correction of input circuits errors by measurements of three-phase current or voltage system unbalance

This paper presents a work in the sphere of measuring power quality characteristics in three-phase networks. Problems of measuring negative sequence voltage and current are considered. It is shown, that actual measurement techniques do not meet accuracy requirements at acceptable costs in full. In order to improve the accuracy, it was proposed to use a multiphase modulation method. The main contribution of the present work is that parameters of a measurement error introduced by asymmetry of input circuits (measure converters) of a measuring device are derived preliminarily with the help of a special correction unit in a "correction" operating mode. This error is then compensated through introducing an artificial unbalance into the main modulating system. The derived parameters of the error are used for calculating the parameters of the artificial unbalance. The paper presents a noninvasive and online method for accurate voltage and current unbalance measurement.