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 implementation of the proposed quadrature phase shifter is aimed at high accuracy reactive power measurements in AC power systems. The implementation of the new phase shifter effectively reduces var/varh measurements to watt/watthour measurements. A prototype has been built and the test results are presented.