Investigation into Harmonic Losses in a PWM Multilevel cascaded H-Bridge Inverter Fed Induction Motor

This paper presents harmonic loss considerations in a PWM multilevel cascaded H-bridge inverter fed induction motor. A non-sinusoidal waveform or voltage harmonic has influence on efficiency and performance of a drive system. Harmonic voltages depend upon PWM parameters such as modulation index, switching frequency, PWM schemes, and dc voltage levels etc. The comparison of additional losses between a conventional inverter drive and a multilevel cascaded H-Bridge inverter drive is evaluated through MATLAB/Simulink and experimental results. Harmonic loss evaluation under various PWM strategies such as sinusoidal pulse width modulation (SPWM), third harmonic injection pulse width modulation (THPWM) and space vector pulse width modulation (SVPWM) for multilevel cascaded inverters is given. PWM signals are generated by a dsPIC microprocessor. The harmonic loss calculation is based on frequency dependent loss functions. Moreover experimental results are also given. The results can be guidelines for designing multilevel inverters suitable for induction motor drives.