High-precision time domain reactive power measurement in the presence of interharmonics

When interharmonics exist in power system signals, large errors emerge in traditional time domain reactive power measurement. In this paper, we present a novel time domain integral method with good effect of restraining interharmonics, synchronization error, and white noise, as well as the principle of the selection of the sampling periods when employing this approach. The current signal and phase-shifted voltage signal are reconstructed after the harmonic components of signals are extracted, so that the interharmonics are filtered. The influence of the synchronization error on the measurement is reduced through removing the weight coefficients of the reactive components. In the simulation, we apply several cosine windows to the proposed method and analyze signals containing both harmonics and interharmonics. The results show that, in the presence of interharmonics, synchronization error, and white noise （with a fundamental signal-to-noise ratio of 40 dB） all together, the relative errors are within the magnitude of 10^-4, which perfectly satisfies the practical requirement.