Harmonic modeling of three-phase neutral-point inverters

The paper derives a closed-form analytical approximation of the output currents harmonic spectra for the three-phase neutral-point inverters under the action of hysteresis current control. The model is an extension of the recently developed model for single-phase two-level hysteresis inverters. The model derives the instantaneous frequency of the inverter and then uses it to approximate the error currents by frequency-modulated sinusoids. The spectra of the error currents are simply the Fourier transforms of the signals' complex envelopes and are expressed in terms of Bessel functions of the first kind. The final expressions of the harmonic spectra are expressed in a suitable form for numerical calculations. MATLAB\Simulink
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studies are presented to validate the proposed model.