单相电流型多电平变流器自均流特性

Natural Current-Balancing Performance of a Kind of Single-Phase Multi-Level Current-Source Inverter

单相电流型多电平变流器拓扑一般都利用分流电感产生各级中间电平电流,为使各级中间电平电流保持平衡,必须研究电流型多电平变流器的均流特性。根据分流电感的连接方式,以一类最简单的单相电流型多电平变流器拓扑为例,通过建立其分流电感电压平均值的数学表达式,从理论上对该类变流器的自均流特性进行了详细分析,仿真实验获得了与理论分析相一致的结论。为改善不同负载特性下输出电流的谐波特性,提出了一种基于直流侧电流反馈、自动选择冗余开关组合的均流控制方法,实验结果验证了控制方法的正确性与有效性。

The sharing-inductors are used to generate the different current-levels for the single-phase multilevel current-source inverter （MCSI）. To keep the intermediate DC-link currents balanced, it is necessary to study the current-balancing characteristics of MCSI. In this paper, according to the connection modes of the sharing-inductors, a kind of single-phase MCSI which has simple circuit structures is introduced. By setting up mathematical expressions of the average-voltage across the sharing-inductors, the natural current-balancing performances of such MCSI are analyzed in detail, and the simulation results are in complete agreement with the theoretical conclusions. In order to improve the harmonic performances of output current at different load conditions, a practicable way to balance the intermediate DC-link current is proposed, which was implemented with automatically choosing the redundant switching-combinations based on the DC-link current feedback. Lastly, the correctness and validity of such control method are verified by the experimental results.