Reduced common mode voltage based DC-bus voltage balancing algorithm for three-level neutral point clamped (NPC) inverter drive

A reduced common mode voltage (CMV) based DC-link voltage balancing strategy is proposed for a neutral point clamped (NPC) three-level inverter with permanent magnet synchronous machine. Compared to the earlier proposed strategy, it completely eliminates the V_dc/2 corresponding CMV by eliminating the two zero voltage vectors (PPP, NNN) from the space vector switching sequences. Hence, it uses only one zero voltage (OOO) vector with the other redundant voltage vectors to produce the reference vector in inner subsectors. Detailed simulation and experimental studies are also carried out to show the effectiveness of the proposed system with DC-link voltage balancing ability. Harmonic distortions are also compared with the previously proposed scheme. Dspace^® based real time operating system is used for real time implementation with 6.0 kW surface PMSM.