Novel SVPWM Overmodulation Scheme and Its Application in Three-Level Inverter

On the basis of study of existing overmodulation techniques published in literatures, two novel single-mode feed-forward carrier-less-based SVPWM overmodulation strategies are proposed. Their characteristics are studied and compared with that of published method. The first method is characteristic of precise linearity between modulation index and modified amplitude of reference voltage vector in overmodulation region and thus improved control precision of fundamental component of output voltage and reduction of required DSP memory and calculation time. While the second one has better THD index, but the control precise decreases little and it is more complicated. The first method is suitable for those applications that demand high control precision of fundamental component but hold little calculation resource and have no high harmonic index requirement. While the second one is for those requiring higher harmonic index and holding plentiful calculation resource. Experiment based on V/f feed-forward-controlled neutral-point-clamped three-level model inverter using one TI TMS320LF 2407A DSP had been carried out. The result of experiment confirms that the two proposed methods are correct and feasible