This paper analyzes the combination in a cascaded H-bridge multilevel inverter (CHBI) based on transformers with the different turn ratios for increasing the voltage level and proposes the switching method for achieving the output voltage distribution among H-bridge cells (HBCs). The transformers used in this paper are connected to the output of the respective HBCs, and the secondary sides of all the transformers are connected in series for generating the final output voltage. Only one of the transformers, in particular, has a different turn ratio for increasing the output voltage level. In this paper, the possible turn ratio of the special transformer with a different turn ratio is discussed in detail, and a switching method based on the level-shifted switching method for the topology used in this paper is proposed. To verify the effectiveness of the proposed method, a three-phase 21-level CHBI is experimentally tested.

中文翻译：

---

基于不同匝数比变压器的级联H桥多电平逆变器提高电压等级的组合分析及切换方法


本文分析了基于不同匝数比变压器的级联H桥多电平逆变器（CHBI）中的组合以提高电压等级，并提出了实现H桥单元（HBC）之间输出电压分配的切换方法。本文使用的变压器连接到各自HBC的输出，所有变压器的次级侧串联以产生最终输出电压。特别地，只有其中一个变压器具有不同的匝数比以增加输出电压电平。本文详细讨论了不同匝数比的特殊变压器可能的匝数比，并针对本文所采用的拓扑提出了一种基于电平移位开关方法的开关方法。为了验证该方法的有效性，对三相21级CHBI进行了实验测试。