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 non-stationary signals. Moreover new algorithms have been examined carefully and developed to attain high levels of accuracy, flexibility and efficiency through STFT-PD (Power Distribution), Particularly, optimized interpolation formulas were used, derived from the windowing theory to reduce the negative effects due to leakage during instantaneous frequency changes. The effectiveness of the 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 has been proven by means of suitable simulations.