MMC系统动态特征及运行机制的研究

Modular multilevel converter (MMC) is a new technology, which draws much attention recently. The scientific research and practice process for MMC just start in the world. Plenty of problems is needed to be solved, especially for the following mechanism: 1) the impact on MMC dynamic behavior of its modulation system and control system and 2) the interaction and the optimal coordination of the control systems. We must pay much attention on: 1) How does the dynamic behavior of MMC impact on the stability of the system if wind energy connected to the system through MMC? 2) How can we control and avoid the disadvantage influence of MMC to the stability of the system? 3) How can we implement and optimize the advantage influence of MMC to the stability of the system? These are critical problems for the acceptance of the wind power through MMC to the system. Our proposal focuses on the dynamic behavior and the operation mechanism of the MMCs. The main contents are: the influence law and the process mechanism of the MMC primary circuit and controllers on its dynamic behavior; the model and theory for the optimization of multiple PI parameters for MMC control blocks and the quantitative analysis for the impact of critical PI parameters on the MMC dynamic behavior; the research on dynamic operation mechanism between MMC and AC system and the impact on the stability areas of the operation of controllers between wind power and MMC.

模块化多电平换流器（MMC）技术的科学研究和实践在全世界都刚刚起步，处于探索阶段，还存在很多问题，其中调制系统以及控制系统对MMC动态特征的影响机理以及多个PI控制器参数之间相互影响和协调优化控制的机理等一系列问题尚未得到解决。我们迫切需要回答这样几个问题：MMC的暂态特性对系统安全稳定和风电接入的影响若何？应该如何控制和避开MMC对系统稳定的不利影响？如何利用和优化MMC对系统稳定的有利因素？这些问题对风电经MMC换流器并网至关重要。本项目针对MMC系统动态特征及运行机制开展研究，主要包括：研究MMC一次回路及控制系统对MMC动态特征的影响规律及其过程机理；建立MMC控制回路中多个PI参数动态优化模型及理论，定量描述PI控制器参数对MMC动态过程的影响规律；研究MMC与交流系统间动态运行机制，分析风电接入控制和MMC控制优化协调对系统安全稳定域的影响。

本项目旨在研究模块化多电平换流器（MMC）一次侧运行机理和二次侧控保策略。主要研究内容包括：1）利用诺顿等效原理建立快速精准的MMC等效桥臂模型，可轻易满足大规模MMC系统实时仿真需求；2）分析MMC正常/故障运行机理，探究MMC一次侧参数对系统运行特性影响；3）针对MMC的各类运行问题，设计完备的关键控制保护策略，以确保MMC在各类工况下具备良好的动态特性；4）利用内点信赖域方法对MMC多个PI控制参数进行协调优化，以保证良好的控制效果；5）建立MMC控制系统的硬件控制平台，测试所提出控保策略和参数优化方法的有效性，并为工程实际应用提供重要参考依据。本项目取得成果丰硕，包括SCI论文7篇，EI论文7篇，国家发明专利10项（授权7项）。培养博士研究生2人，硕士研究生6人。所取得科研成果已应用于“南澳柔直项目”中，并产生重大的积极影响。