多电平变换器是实现高压大容量交流变频调速的主要途径之一，为解决传统二极管箝位型多电平拓扑输出电压等级低、箝位二极管数量多以及母线中点电压难以平衡等问题，本课题提出了一类新型有源中点箝位型多电平拓扑，具有结构简化、开关管电压应力小无直接串联、箝位器件数量少、电容电压完全可控等优点，是一种非常实用化的拓扑结构。本课题将针对该类拓扑的演化规律、调制策略、电容电压平衡控制算法以及分布式控制系统等关键问题展开深入研究，拟采用基于载波移相PWM和最优零序电压注入的多目标优化控制策略，实现悬浮电容电压和直流母线中点电压平衡控制、共模电压抑制、开关频率优化等多个控制目标。最终目标是实现一整套基于新型有源中点箝位型多电平变换器的性能好、效率高、成本低、可靠性高且控制功能完善的高压大容量变频调速系统解决方案，为其以后在工业上的推广应用奠定技术基础。

Multilevel converter is the main approach to achieve high-voltage high-power variable frequency speed regulation of AC motors. In order to overcome the drawbacks of the traditional neutral-point clamped (NPC) multilevel converters, such as low output voltage, mass clamping diodes and voltage imbalance of neutral-point potentials, a new type of active neutral-point clamped (ANPC) multilevel converters is proposed in this project, which possesses the advantage of simple structure, low voltage stress, few clamping devices and complete controllability of capacitor voltages and so is a very practical topology. The evolution rule, modulation method, capacitor voltage balancing method and distributed control system will be studied in this project. Based on carrier-shifted PWM and zero-sequence voltage injection, the voltage balancing of flying capacitors and DC-link capacitors, common-mode voltage reduction and switching frequency optimization can be achieved by selecting a comprehensive optimal zero-sequence voltage. The ultimate goal is to provide a complete solution of a variable frequency adjustable-speed system based on the new ANPC multilevel topologies with high performance, high efficiency, low cost, high reliability and perfect control function and lay a solid foundation for the future application in industry.