Three-phase inverter modeling using multifrequency averaging with third harmonic injection

Models of converters based on averaging have been used widely with numerous benefits. Multifrequency averaging (MFA) model can predict both the fundamental and switching behavior of converters and has the faster simulation run times associated with average-value models. Third harmonic injection is commonly used in the modulation signal for three-phase inverters to increase the inverter maximum output voltage while avoiding overmodulation. Herein, an MFA model for three-phase pulse width modulation inverters with third harmonic injection is proposed. The quasi-Fourier-series representation of the switching functions with third harmonic injection is necessary for constructing three-phase inverter MFA model. The third harmonic injection does not change the fundamental and third harmonic components of the state variables in a balanced three-phase system, but it changes the higher-order harmonics. As a result, the quasi-Fourier-series representation of the switching functions for three-phase inverters with third harmonic injection must include the third harmonics. The proposed MFA model is demonstrated in simulation, and the simulation results show that this model has high accuracy (including the switching behavior) and fast run times.