Modified DC-link voltage balancing algorithm for a 3-level neutral point clamped (NPC) traction inverter based electric vehicle PMSM drive

This paper presents a modified DC bus voltage balancing algorithm for a neutral-point clamped (NPC) three-level inverter based motor drives for permanent magnet synchronous machines (PMSM) used in electric vehicle applications. The topology used for DC bus voltage balancing is based on nearest three vectors (N3V) with a space vector pulse width modulation scheme (SV-PWM). In this scheme, the voltage space vectors are rearranged based on the four redundant small voltage vectors, to keep the two DC link capacitor voltages in their specific tolerance bands, even during fast transient conditions of the machine. This topology provides high stability and lower switching loss compared to the conventional N3V scheme. The performance of the proposed scheme is verified by simulation and hardware experimental tests.