混合9电平逆变器的H桥电容电压平衡控制

混合9电平逆变器是一种新型的多电平拓扑结构。文章在研究了H桥逆变电路直流电容电压充放电模型的基础上，得到了负载电流与电容电压变化之间的定量计算公式，进而详细分析了混合9电平逆变器H桥辅助逆变电路电容电压不平衡的内在机理，最后提出了一种基于电容电压不平衡预估计和零序电压注入的平衡控制方法。所提方法原理简单，实现容易，无需增加额外的硬件设备。通过仿真验证了在混合9电平逆变器的参考电压中注入零序电压后，混合9电平逆变器的H桥逆变电路电容电压得到平衡控制。

RESEARCH OF CAPACITOR VOLTAGE BALANCE CONTROL OF H-BRIDGE INVERTER OF HYBRID 9-LEVEL INVERTER

As a novel multilevel inverter topology, there are few published references on hybrid 9-level inverter, especially the investigation of the application of variable-voltage-variable-frequency drive systems. In this paper, the computation formula between the load current and capacitor voltage is attained based on the charging model of capacitor voltage of H-bridge inverter. And the inherent mechanism of capacitor voltage imbalance of the assistant H-bridge inverter of hybrid 9-level inverter is analyzed in detail. Then a capacitor voltage balance control method based on capacitor voltage predictive estimation and the injection of zero-sequence voltage is proposed. The principle of the proposed method is simple and easy to realize without additional hardware equipment. The simulation results demonstrate the validity of the proposed method. By the injection of zero-sequence voltage into the reference voltage of hybrid 9-level inverter, capacitor voltage balance of H-bridge inverter is achieved.