Instantaneous-power measurement in time-frequency domain

The paper deals with an original application of the Short-Time Fourier Transform (STFT) to instantaneous power measurements. This technique can be easily implemented in a dedicated instrument to perform accurate time-frequency analysis of the time-varying harmonic contents of network powers (in their active and imaginary components), which are typically nonstationary signals. Moreover, we examined carefully and developed new algorithms to attain high levels of accuracy, flexibility and efficiency through STFT-PD (Power Distribution). Particularly, we used optimized interpolation formulas, derived from the windowing theory to reduce the negative effects due to leakage during instantaneous frequency changes. We proved by means of suitable simulations the effectiveness of our suggested technique and, particularly, the high level of accuracy achieved in time-varying amplitude and frequency measurements of the analysed components of instantaneous powers and currents.