Abstract
Due to the trend of decentralized generation (DG) residing in low voltage distribution network, more inverters are connected to the grid in three-phase four-wire systems under asymmetrical condition. This paper presents an algorithm to balance DC-link capacitor voltages and minimize switching loss of three-level four-leg inverters which is suitable for asymmetrical condition. The algorithm is based on three-dimension space vector modulation (3D-SVM) in natural coordinates. The algorithm balances DC-link capacitor voltages by the selection of redundant standard vectors. Switching sequences are selected to minimize switching loss. Simulation results show that the method is able to balance DC-link capacitor voltages and reduce middle point voltage ripple.