3D Space Vector Pulse Density Modulation Scheme for Two-Level Four-Leg Inverter

Four-leg inverters are widely used to mitigate the effects of unbalanced three phase supply and unbalanced three phase loads. The most popular switching signal generation technique for four-leg inverter are 3D Space Vector Pulse Width Modulation (3D SVPWM) schemes. In this paper a 3D Space Vector Pulse Density Modulation (3D SVPDM) scheme for two-level four-leg inverter is proposed. The proposed 3D SVPDM scheme uses abc coordinate system. The oversampling and noise shaping property of Pulse Density Modulation (PDM) provides better harmonic performance than SVPWM schemes. 3D SVPDM does not have any complex timing calculations. The proposed scheme can be used for active power filter applications. 3D SVPDM is validated through simulation by using Matlab/Simulink software. The simulation results of 3D SVPDM are compared with 3D SVPWM scheme and it is observed that 3D SVPDM shows better total harmonic distortion (THD) characteristics.