有源中点钳位型多电平变换器综合优化控制策略的研究

In order to improve the overall performance of the active neutral-point -clamped (ANPC) multi-level converter, the comprehensive optimization of multiple key control objectives is studied in this project. The control objectives include neutral-point potential, flying-capacitor potential, loss distribution, loss reduction and common-mode voltage. In order to realize the balancing control of the neutral-point potential and the flying-capacitor potential, a control strategy which combines the dynamic adjustment of the duty cycle of the three-phase redundant switching-states with the specific vector virtualization is proposed. Under different commutation modes, the influence of the load power factor on the loss distribution is studied. The control strategy of the loss distribution balancing and the capacitor potential balancing is proposed. The loss distribution of ANPC converter with the wide band gap semiconductor device will be studied. A novel virtual space vector modulation method is proposed to control the capacitor potential balancing and suppress the common-mode voltage simultaneously. The composition rules of virtual space vectors are redefined. According to the priority of the control objectives, the comprehensive optimization of multiple control objectives is realized by selecting different pulse sequences flexibly. Finally, the hardware-in-loop simulation and experimental study are implemented to verify the effectiveness of the proposed strategies. The major objectives of the project are to achieve a breakthrough in key technologies of the multi-level converter, to explore novel control strategies and modulation methods, and to promote the development of the multi-level converter and its comprehensive optimization method.

为了提升有源中点钳位型多电平变换器的综合性能，课题将对变换器多个关键控制目标的综合优化进行深入研究。研究的控制目标包括：直流侧中点电压、悬浮电容电压、损耗分布、损耗减小、共模电压等。为实现中点电压和悬浮电容电压平衡控制，提出了动态调整三相冗余开关状态占空比与特定区域矢量虚拟相结合的控制策略；研究了不同换流模式下负载功率因数对损耗分布的影响，提出了损耗分布与电容电压平衡结合的控制策略，并拟对采用新型宽禁带半导体器件的变换器损耗分布进行研究；提出了一种能同时控制电容电压平衡和抑制共模电压的虚拟空间矢量调制策略；对虚拟空间矢量的合成规则进行了重新定义，根据控制目标的优先级，通过灵活选择不同的脉冲序列实现了多个控制目标的综合优化。最后进行半实物仿真和实验研究。拟通过课题的研究，深入探索新的控制策略和调制方法，以求在多电平变换器关键技术上有所突破和创新，推动多电平变换器及其综合优化方法的研究和发展。

多电平拓扑结构具有输出容量大和谐波含量少等优点，在高压大功率和输出电能质量要求高的场合得到了广泛应用。有源中点钳位型(ANPC)拓扑是一种能够克服传统二极管钳位型和电容钳位型拓扑缺点的新型多电平变换器。本项目以ANPC为研究对象，针对直流侧中点电压、悬浮电容电压、损耗分布、共模电压等进行了深入研究，主要研究内容包括：（1）中点电压和悬浮电容电压平衡控制；（2）损耗分布平衡和电容电压平衡协同控制；（3）中点电压和共模电压的优化调制；（4）多目标综合优化控制策略。项目克服的难点主要有：（1）多个关键控制目标的解耦及其综合优化问题；（2）不同负载功率因数特性对开关器件损耗的影响；（3）基于不同控制目标的多电平虚拟空间矢量的合成规则。本项目采取理论探索、半实物仿真和实验研究相结合的方法，解决了以下关键科学问题：（1）悬浮电容电压与中点电压平衡的解耦；（2）中点电压平衡与共模电压抑制的协同优化；（3）不同换流模式下负载功率因数与开关损耗的量化分析；（4）变换器开关状态及其变化与中点电压、悬浮电容电压、共模电压及损耗的关系。本项目的研究成果：（1）在国际/国内著名学术期刊和IEEE学术会议上发表学术论文26篇，其中被SCI期刊和EI期刊收录论文9篇；（2）授权发明专利9项；（3）培养研究生6名；（4）提出了多电平ANPC变换器数学模型、综合优化控制与调制策略；（5）搭建了ANPC变换器优化控制的仿真模型、半实物仿真模型和实验平台；（6）获得2019年中国电工技术学会科学技术一等奖（排名2/15）和2021年安徽省科技进步二等奖（排名1/10）。本项目的研究成果对提高ANPC变换器的效率和运行性能有着重要的指导意义。