A New Neutral Point Voltage Control Strategy for NPC Three Level Inverters

Shuxi Liu, Shan Li, Xiaoduo Yang
2018 Proceedings of the 2018 2nd International Conference on Electrical Engineering and Automation (ICEEA 2018)   unpublished
Multi-level inverter is now becoming an efficient and promising technology in sorts of applications, especially in high level voltage inverters. However, the unbalanced voltages between two DC-link capacitors while operating the Neutral Point Clamped (NPC) three-level inverters is an inherent problem, which in a way can excessively affect the quality of the output voltage. In this paper, a new strategy for NPC three-level inverter in DC-link balancing control is proposed. The proposed strategy
more » ... s implemented by both adjusting the acting time of Ptype small vectors and N-type small vectors in the duration times of the nearest three vectors space vector modulation and changing the switching sequences of redundant small vectors of every switching period. These two modes are selected based on the difference value of the neutral point voltage. Hence it not only has the ability to limit the large neutral point voltage drift, but also reduced the switching loss. The proposed method is simple to achieve so that complex calculation and additional hardware circuits will not be needed. The results of simulation have shown that the strategy for balancing neutral point voltage is practical and effective. Keywords -NPC inverter; neutral point balancing; hysteresis loop; switching sequence selection      
doi:10.2991/iceea-18.2018.4 fatcat:lgw3aqarofbaljul3vefwjn5y4