Spread spectrum scheme for two-level inverters using Space Vector Sigma-Delta Modulation

A novel Space Vector based Sigma Delta Modulation (SDM) scheme for Voltage Source Inverters to disperse the discrete switching harmonics as a wide-spectrum noise is presented in this paper. The proposed Space Vector Sigma Delta Modulation (SVSDM) scheme comprises first order Sigma-Delta Modulator with two dimensional Space-Vector Quantization to generate switching vectors. The space vector region in the proposed work is divided into seven voronoi regions and a method is presented to code these regions as part of the vector quantisation from instantaneous reference phase amplitudes without using any lookup table. The spectrum of inverter output is spread so that large concentrations of power at discrete frequencies are avoided. The proposed SVPDM scheme is implemented for a 11.5 kVA two-level inverter driving 2-HP three phase induction motor. Experimental results of proposed scheme, including operation in over modulation region, and comparison of spectra with Space Vector PWM are presented.