双向Z源三电平逆变器中点电位动态平衡算法

双向串联型Z源三电平逆变器直流输入电压通过分压电容分压,存在中点电位平衡问题。但是,现有针对于Z源三电平逆变器的中点电位平衡算法具有以下缺点：1)不适用于双向变流器；2)由于中点电位平衡与Z源升压相互制约,且传统SVPWM策略整体升压能力小,中点电位平衡控制困难。针对以上问题,通过扩展直通状态的作用时间,提高SVPWM策略的整体升压能力；进而将动态平衡因子与Z源升压耦合,提出双向Z源三电平逆变器中点电位动态平衡算法。仿真结果表明：1)相比于传统SVPWM算法,基于改进SVPWM算法,改进拓扑的整体升压能力提高；2)在逆变、整流和低功率因数3种工况下,能够维持中点电位平衡。

The neutral-point potential dynamic balance method for the bi-directional Z-source NPC three-level inverter

The dc voltage of the bi-directional tandem type Z-source NPC three-level inverter is divided through voltage-divider capacitor. As a result, the neutral-point(NP) potential should be kept balance. However, the NP potential balancing methods, applied to the Z-source NPC three-level inverter, have the following disadvantages: 1)unsuitable for the bi-directional converter; 2)due to the interaction between the NP potential balance and Z-source boosting as well as low boosting ability of the traditional SVPWM modulation, it is difficult to obtain the NP potential balance. In order to solve the problems, by extending the shoot-through offset, the boosting ability of the advanced SVPWM modulation is improved. What is more, combining the dynamic balance factor with Z-source boosting, the NP potential balancing methods for the bi-directional Z-source NPC three-level inverter is proposed. The simulation results indicate that compared with the traditional SVPWM modulation, the boosting ability of the novel topology is improved based on the advanced SVPWM modulation. In addition, the NP potential is obtain balance in following 3 operations, including inverter, rectifier and low power factor operation.