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Space Vector Pulse Density Modulation Scheme For Multilevel Inverter With 18-sided Polygonal Voltage Space Vector

Anilett Benny, Dr.T. Ruban Deva Prakash

Space Vector Based Pulse Density Modulated scheme for multilevel inverter is proposed in this paper. A two level and three level inverters with three different DC input voltages are used to produce 18 stepped output sinusoidal voltage. First order sigma delta modulator is used to obtain Pulse Density Modulation. The vector space is divided into 18 segments for spatial quantization. Sixty degree co-ordinate system is used to avoid fractional arithmetic. The proposed scheme uses only switching vectors which lie on the vertices of 18 sided polygon. The scheme uses only sector identification for selecting the switching vectors without using lookup table and timer. The proposed scheme with 18 sided polygonal multilevel inverter results in elimination of 5th, 7th, 11th and 13th order harmonics when compared to two level inverter schemes. Simulation results of the proposed scheme are compared with that of two level inverter schemes. From the results, the total harmonic distortion (THD) of the output voltage of SVPDM based 2-level inverter is 31.13% and the 18-sided multilevel inverter with SVPDM is 10.11%. From the results, the validity of the SVPDM based 18-sided multilevel inverter has been confirmed. Zero voltage switching can be incorporated in future for achieving high efficiency