Features of the Implementation of the Reactive Power Measurement Method Based on the Application of Integrator and Differentiator

The most informative parameters of modern electrical power grids are reactive power of fundamental component and reactive power of harmonics. In electric power industry, there are a large number of different techniques to measure these parameters, which characterizes some disadvantages. The most significant disadvantages include the strong influence of the error by the frequency deviation of the input signal and signal spectral components that are not included in the measurement frequency band. The paper proposes a modification of so-called integration-differentiation method, which makes it possible to measure reactive power with greater accuracy. Relationships are obtained that allows to estimate the error of reactive power due to the deviation of the input frequency and the presence of additional (not included in the measurement frequency band) spectral components of signal. The influence of signal parameters (amplitude, frequency, initial phase) and measuring system parameters (sampling frequency, measurement time) on the reactive power measurement error is analyzed. To reduce both error components, a band-pass digital filter is proposed. Analytical relationships are obtained that allows to calculate the filter parameters to achieve the required error of reactive power measurement. Variants of application of different types integrators and differentiators are considered. By the application of Simulink, a model of the researched technique was performed. The proposed modification is compared with the "classical" integration-differentiation method, as well as with the popular integration method and the differentiation method.