Space vector modulation for 3-level NPC converter with neutral voltage balancing and switching loss/noise reduction

This paper proposes an improved space vector modulation (SVM) method for the 3-level neutral point clamped (NPC) inverter that serves as a bidirectional power conversion system for renewable energy micro-grid. Conventional SVM for the NPC converter majorly deals with neutral point (NP) balance issue without considering switching loss. The proposed SVM method balances the NP voltage and minimize the switching loss/noise simultaneously. The coordinately selected redundant vectors consider both the NP charge and the pulse sequence so that the minimized NP ripple and switching events is guaranteed in one switching cycle. In addition, the switching events between switching cycles are also considered to reduce the total switching loss and noise. This method also guarantees evenly distributed phase leg loss and constant system efficiency under different power factors (PF). The control result for NP balance and loss reduction is verified by both simulation model and experiment on a 200kVA converter hardware.