三电平NPC逆变器的开关器件由于耐压水平低、电网侧并网电压谐波含量少等优点，广泛应用于大功率整流场合。中性点电压平衡问题一直是该拓扑的研究关键。通过对每一个开关阶段直流侧两电容充放电的电荷波动数值检测，再通过公式变换，对传统空间矢量脉宽调制(SVPWM)的正负小矢量分次运行时间进行调整，使平衡点上下两电容充放电时间能够保持一致，达到中性点平衡控制的目的。仿真验证表明，该方法能够抑制中性点电压的波动。

The switching devices of three-level NPC inverter are widely used in high-power rectifier due to the advantages of low withstand voltage level and less harmonic content of grid connected voltage. The problem of neutral point voltage balance is always the key of the topology. Through the numerical detection of charge fluctuation of two capacitors at DC side in each switching stage, after formula transformation, the time of positive and negative small vectors of traditional space vector pulse width modulation (SVPWM) is adjusted, so that the charging and discharging time of the two capacitors at the balance point can be kept consistent, and the purpose of neutral point balance control can be achieved. Simulation results show that the method can suppress the fluctuation of neutral point voltage.