Research on the Mechanism of Neutral-point Voltage Fluctuation and Capacitor Voltage Balancing Control Strategy of Three-phase Three-level T-type Inverter Gangui Yan*, Shuangming Duan† , Shujian Zhao*, Gen Li**, Wei Wu* and Hongbo Li*

Research on the Mechanism of Neutral-point Voltage Fluctuation and Capacitor Voltage Balancing Control Strategy of Three-phase Three-level T-type Inverter Gangui Yan*, Shuangming Duan†, Shujian Zhao*, Gen Li**, Wei Wu* and Hongbo Li*

Corresponding Author: School of Electrical Engineering, Northeast Electric Power University, China. (33339371@163.com) * School of Electrical Engineering, Northeast Electric Power University, China. (yangg@neepu.edu.cn, zsj_neepu@foxmail.com, veil0814@126.com, dqlihongbo123@163.com)

 Abstract – In order to solve the neutral-point voltage fluctuation problem of three-phase threelevel T-type inverters (TPTLTIs), the unbalance characteristics of capacitor voltages under different switching states and the mechanism of neutral-point voltage fluctuation are revealed. Based on the mathematical model of a TPTLTI, a feed-forward voltage balancing control strategy of DC-link capacitor voltages error is proposed. The strategy generates a DC bias voltage using a capacitor voltage loop with a proportional integral (PI) controller. The proposed strategy can suppress the neutral-point voltage fluctuation effectively and improve the quality of output currents. The correctness of the theoretical analysis is verified through simulations. An experimental prototype of a TPTLTI based on Digital Signal Processor (DSP) is built. The feasibility and effectiveness of the proposed strategy is verified through experiment. The results from simulations and experiment match very well.
LINK
http://www.mediafire.com/file/cdwxgmn2dburlbu/E1EEFQ_2017_v12n6_2227.pdf