Application of the Short Time Fourier Transform for Calculating Electric Energy Losses under the Conditions of a Non-Sinusoidal Voltage

Abstract

The problem of calculating active electric energy losses under the conditions of a non-sinusoidal voltage in the 380 V network is considered. The network voltage is represented as a partially steady signal, with the time dependences of signal component frequencies or harmonic components being piecewise constant functions. This circumstance adds difficulty to the use of classic loss calculation methods, which do not allow the spectrum to be analyzed as a function of time. For solving the problem, the discrete-time short-time Fourier transform is applied. Based on the results of calculating the discrete-time short-time Fourier transform, the steadiness intervals are determined, in which the electric energy losses are subsequently calculated using the well-known formulas. For estimating the validity of the proposed approach, simulation is carried out of the electric network part containing an industrial load connected to a 380 V bus via a cable line in which the electric energy losses are calculated. A conclusion about the applicability of the short-time Fourier transform is drawn.