Discontinuous hybrid modulation technique for three-phase three-level neutral point clamped inverters

Multilevel converters are widely used in high-power applications such as motor drives, utility applications, and, more recently, photovoltaic and wind generation systems. A number of modulation strategies have been proposed in literature in the particular case of three-phase three-level NPC topology, each one focusing on the optimization of specific aspects and performance of the converter, such as efficiency and neutral point (NP) balancing. In this paper a new discontinuous hybrid modulation technique is presented, obtained by combining discontinuous (DPWM) and hybrid (HPWM) pulse width modulations. By sharing the advantages of both techniques a reduction of switching and conduction losses is obtained, control of the low frequency component of NP ripple is maintained and an additional degree of freedom for its active control is theoretically available. Simulation and experimental results based on a TMS320F28035 DSP controller and a NPC three level inverter are presented to confirm the effectiveness of the proposal.