Linearization of the Multi-level SVPWM Signal Generation in the Over-Modulation Region Extending up to Six-step Mode Using Only the Sampled Amplitudes of Reference Phase Voltages

Abstract

A multi-level PWM signal generation with linear transfer characteristics between fundamental component of output voltage and modulation index is proposed in this paper for a n-level SVPWM signal generation. The reference signal to the PWM modulator is pre-scaled in over-modulation region, keeping the fundamental component of the modified signals same as the original signal. The modified reference signal is always confined within the carrier region. Thus linear transfer characteristics can be extended throughout the over-modulation region up to six-step mode to get the maximum utilization of DC link, for multi-level inverter drive control of any general n-level. In this paper, the principle of pre-scaling the reference signal, based on a look up table, for two-level PWM generation is extended to a general n-level SVPWM. The whole PWM signal generation is implemented using only the sampled amplitudes of reference phase voltages and the algorithm is very suitable for real time implementation on DSP processors. A five-level inverter configuration, using an open-end winding induction motor drive, is used for verifying the SVPWM generation scheme, experimentally.