A high performance frequency insensitive quadrature phase shifter and its application in reactive power measurements

This paper describes a high precision circuit for quadrature phase shifting in which frequency controlled signal amplification is introduced so that the amplitude of the phase shifted signal is not dependent on the frequency of the input signal. The proposed quadrature phase shifting method is aimed at high accuracy reactive power measurements in ac power systems. The implementation of the new phase shifter at the voltage input of a watt/watt hour meter allows for high accuracy var/varh measurements. A prototype of the quadrature phase shifter has been built with magnitude and phase errors within /spl plusmn/15/spl middot/10/sup -6/ and less than 40 /spl mu/rad, respectively. Its performance was further confirmed when the QPS was used for reactive power measurements.