Space Vector based Spread Spectrum Modulation scheme for three-level inverters

A Spread Spectrum Modulation scheme based on Space Vector for three level inverter is proposed in this paper. The scheme disperses the power spectrum of the inverter output voltage as a wide-spectrum noise. The vector space of inverter reference space vector region is divided into voronoi regions to find out switching vectors. A new method is presented to code these voronoi regions with Vector Quantization using instantaneous reference phase amplitudes without using lookup table. The space-vector diagram of three-level inverter is simplified to two-level space-vector diagram by the principle of mapping. The switching vectors are determined for two-level inverter using the proposed scheme and these switching vectors are then translated to the actual switching vectors of the three-level inverter by reverse mapping. The proposed scheme naturally selects the outer vectors in the over-modulation condition and hence results in a smooth transition from linear to over-modulation region. The scheme is implemented for 2-HP three phase induction motor driven by three-level cascaded inverter topology.