一种新型的无变压器级联型多电平变换器拓扑

A Novel Transformerless Cascaded Multilevel Converter Topology

H桥级联多电平逆变器在高压大容量变频调速领域得到了广泛的应用,其最大的不足之处是必须使用庞大、复杂而昂贵的多绕组移相隔离变压器。为了省去传统H桥级联多电平变换器中的多绕组移相变压器,提出了一种新型的无变压器级联型多电平变换器拓扑结构。该拓扑由通用拓扑结构派生而来,全部由基本单元级联而成,不需要大量独立直流电源,省去了多绕组移相隔离变压器,具有模块性强、结构简单、易于扩展等优点。和现有的主要多电平拓扑结构相比,随着电平数的增多,使用元件较少,更适合于五电平及以上多电平使用。以五电平拓扑为例进行了研究,分析了其工作原理和悬浮电容电压平衡控制方法,仿真和实验结果验证了其可行性。

Cascaded H-bridge multilevel inverter is widely used in high-voltage high-power motor drivers.The biggest shortage is the use of multi-winding transformer which is bulk,complex and expensive.In order to eliminate the multi-winding transformer of the traditional cascaded H-bridge inverter,a novel transformerless cascaded multilevel converter is proposed in this paper.It＇s derived from the generalized multilevel inverter topology and consists of a number of cascaded basic cells.All the dc capacitors are floating and the separated dc sources are not needed,so the multi-winding transformer is no more needed.Due to its high modularity,it can be easily extended to higher levels.By comparing it with existing main multilevel topologies,the new topology needs fewer components while producing the same number of output voltage levels,so it is more suitable for converters with a high number of voltage levels.By taking a five-level new topology as example,the operating principle and voltage balancing method of the proposed topology are presented.The validity of the proposed topology and control method is verified by simulation and experimental results.