Research on Neutral Point Potential Balance Control Strategy of NPC Three-Level Inverter for Permanent Magnet Synchronous Motor

Abstract

Aiming at the neutral point potential imbalance problem of three-level neutral point clamped (NPC) inverter, an improved neutral point potential balance control strategy depend on space vector modulation method is suggested. Firstly, the equilibrium mechanism of neutral point potential is analyzed by the coupling relationship between neutral point current and dc-link capacitor. In Accord with the influence of the change amplitude of the neutral point potential error variation and the redundant small vector on the direction of the neutral point current, the action time of the redundant small vector pair is corrected. On this basis, the balance control of neutral point potential is realized by using the space vector modulation method. The simulation results show that compared with the control strategy without neutral point potential balance, this approach can forcefully control the neutral point potential balance of NPC three-level inverter. It is of great significance for system stability and accurate control of permanent magnet synchronous motor.