Modification of the Integration-Differentiation Technique to Reduce the Reactive Power Measurement Error

Today, a large number of digital measurement methods have been developed to measure the reactive power of power network signals. The integration-differentiation method is characterized by a weak dependence of the error on the value of the signal frequency, which makes it effective for the case of measuring the reactive power of sinusoidal signals. However, the transmission coefficient at other harmonics is very different from unity, which results to a large error of the reactive power of individual harmonics for the situation when the measured signals are non-sinusoidal. To reduce this shortcoming, this paper proposes the application of a second-order IIR bandpass filter. The paper considers a integration-differentiation method implementation which is based on a three samples digital differentiator and an second-order digital integrator. The magnitude response of the resulting integration-differentiation block are obtained and the measurement error of reactive power is estimated for the case of application the specified differentiator and integrator. A technique for calculating the parameters of a digital IIR filter is considered. Estimates of the resulting reactive power error of main harmonic and in a given frequency band are obtained.