背靠背级联H桥型四象限五电平变换器

Research on a Back-to-back Cascaded H-bridge Four-quadrant Five-level Converter

为提高变换器的输出电压等级和容量,省去传统级联H桥型变换器中的工频变压器,降低系统体积和成本,并实现能量双向流动和电机的四象限运行,采取了将级联H桥型变换器进行背靠背连接的方案,形成了一种五电平变换器,分析了变换器的有效开关模式和等效电路,建立了开关脉冲模型,提出了变换器中电容电压的均衡控制算法,给出了变换器的调制策略。实验结果表明,变换器可以维持各直流母线电压恒定,实现五电平输出和四象限运行,提出的分析方法和调制策略正确。

In order to raise the voltage level, eliminate the linelfrequency transformers, reduce the size/cost of the con- verter, and make bi-directional power flow available, a back-to-back cascaded H-bridge four-quadrant five-level converter was proposed. Five-level output voltages can be realized, which can enlarge the capacity of the system with low rating voltage devices. The equalization circuit and legal switching states of the converter are presented. Moreover, the capacitor voltage balancing algorithm is built, a five-level three-phase experiment system is established, and the results validate the proposed topology and algorithm. The capacitor voltages can be maintained as constant, the power factor on the input side is as high as 1, and the converter can output five-level voltages. Also, the four-quadrant experiment is carried out, which validates the bi-directional power flow capability.