A balancing control algorithm of neutral point potential for three-level neutral-point-clamped(NPC)inverter based on selective harmonics elimination pulse-width modulation(SHEPWM)is proposed. Firstly

the principle of neutral point potential balance for space-vector pulse-width modulation(PWM)and the mathematical model of SHEPWM are described. Then

the switching vector sequence and the switching angle corresponding to the three-phase SHEPWM waveforms at different modulation indices are analyzed

with three kinds of redundant vector adjustment schemes designed. Finally

in order to realize neutral point potential balance

the load current and the neutral point potential are detected

and the three-phase PWM signal can be directly adjusted on-line by the hysteresis controller and the control logic. Experimental results show that different vector adjustment schemes have different neutral point potential balancing speeds and average switching frequencies

none of which affects the harmonic elimination ability of line voltage. And the neutral point potential three-stage hysteresis controller can counterpoise the performance of the neutral potential balance

symmetrical waveform

amplitude of common-mode voltage

without increasing the number of times of switching. This work is supported by National Natural Science Foundation of China(No. 51677156).