中文摘要：

为了驱动高压大容量电机并将电机制动过程中的能量回馈入电网,提高电能的利用效率,提出了一种单相四象限五电平变换器。针对提出的拓扑结构,分析了变换器的工作模式,并建立了开关模型,并得出了开关脉冲与系统输出电压之间的关系。讨论了变换器不同开关状态下系统的等效电路,提出了一种判断开关状态是否合法的策略。分析了变换器中的电容电压均衡控制问题,提出了一种优化调制策略,给出了开关状态的计算流程图,实现了变换器的多电平输出。建立了实验样机平台,实验结果表明,提出的变换器可实现五电平输出,系统的控制策略和调制算法有效可行。

英文摘要：

In order to drive the high-voltage large capacity motor and deliver the power generated by the motor when breaking to the power grid, a single-phase four-quadrant five-level converter was proposed. The working scheme was discussed and the equivalent circuits were drawn. The model of the switches was built, and the relationship between the switch state and voltage was revealed. The relationship between the capacitor voltage and the modulation method was analyzed and the corresponding algorithm was found, which can output the desired voltage and maintain the capacitor voltage. An experimental system was built and the experimental results show that the proposed inverter works properly. Also, the proposed al- gorithm and control strategy are proved to be practical and available.