DC-Link capacitor voltage balancing in Neutral Point Clamped inverters using Space Vector Modulation

Neutral point balancing is an inherent problem of Neutral Point Clamped (NPC) inverter. In this paper, various techniques to balance neutral point voltage is presented. Most of these techniques uses the redundancy of Space Vector Modulation (SVM) for NPC inverter to mitigate this problem. Nearest Three Vector (NTV) is one of the technique which balances the neutral point voltage effectively. However, for NTV, at high modulation index (mi), there is low frequency ripple present which causes undesirable losses and stress on the DC-link capacitors. The Effect of mi on balancing is discussed from the concept of dominance duty time ratio for Small and Medium vectors. Simulation is performed on a real time platform and results are discussed in detail.