Space Vector Pulse Density Modulation Scheme for Multilevel Inverters using Line Voltages Coordinate Transformation

This paper proposes a Space Vector Pulse Density Modulation (SVPDM) scheme that utilizes line voltage coordinate transformation. The scheme uses three first order Sigma Delta Modulators (SDM) for generating pulse density modulation, wherein the reference vector is vector quantized to generate the output switching vectors. The switching vectors for the inverters are derived without sector identification in this scheme making the algorithm computationally simpler. Voronoi region in the proposed Space Vector Quantizer (SVQ) are defined as a triangle with the inverter switching vectors as its vertices. The proposed SVPDM scheme retains the advantages over Space Vector Pulse Width Modulation (SVPWM) scheme such as avoidance of pulse width problem, calculation of duty ratio, use of look-up table. SVPDM has better spectral characteristics, ease of digital implementation, decreased electromagnetic interference, avoidance of complex timing calculations, and less acoustic noise of motor. The proposed scheme is simulated for a 5L Active Neutral Point Clamped (5L-ANPC) topology and result are verified.