A leading power factor based DC-link voltage balancing algorithm for three-level neutral-point-clamped traction inverter drive

This paper presents three different virtual space vector based strategies to keep the neutral point potential fluctuation (NPPF) low in the field weakening region for an interior permanent magnet synchronous machine (IPMSM) drive. Out of three strategies, one even completely eliminates the NPPF. A detailed analytical study to demonstrate the root cause behind the high NPP fluctuation in the field weakening region for IPMSM inverter based traction drive is carried out. The duty ratios for all the vectors are separately derived based on the nearest three voltage vectors (NTV) for each strategy. Detailed simulation and experimental studies are then carried out to show the effectiveness of the proposed control strategies with a 6.0 kW IPMSM. Results show a considerable reduction in capacitor voltage deviation with the proposed strategies compared to the conventional one.