基于端口频率特性的微网基波频率谐振机理及抑制技术研究

Microgrids are significant solution for utilizing renewable energy in large-scale, where the interaction among power electronics converters is prone to cause system resonance. At present droop control between the power and fundamental frequency is adopted in more and more distributed sources of the microgrid for power sharing, which introduces fundamental frequency coupling among sources, and sources and loads, and further cause system resonance. While the frequency domain approach based on terminal characteristics model of converters is more suitable to study the resonance of microgrid than the time domain approach based on state space model of whole system, existing study on mechanisms and mitigation techniques of resonance in microgrid using terminal frequency characteristics of converters is less associated to the fundamental frequency resonance. Focusing on this scientific issue, this project is proposed to study the resonance mechanisms in two levels through terminal frequency characteristics of converters, which are the fundamental frequency resonance among the sources, and the one between the source subsystem and the load subsystem, and thus establish the architecture of fundamental frequency resonance mechanism in microgrid. Meanwhile, based on the architecture of mechanisms, the project is also proposed to study the resonance mitigation techniques through both improving inner structure of converters in microgrids and connecting active dampers, and propose effective implementation solution for resonance mitigation. The research fruit of this project will offer key technical support to stable and safe operation of microgrids, and thus presents a good application prospect.

微网是实现可再生能源规模化开发利用的重要手段，然而其内部变流器之间的相互作用易导致系统谐振。目前微网中越来越多的分布式电源采用功率-基波频率下垂控制实现功率分配，这将导致微网中电源之间、电源和负载之间形成基波频率耦合，进而引发系统谐振。基于变流器端口特性模型的频域方法较传统电力系统中基于系统状态空间模型的时域方法更适用于微网谐振研究；而现有基于变流器端口频率特性的微网谐振机理及抑制技术研究中尚未涉及到基波频率谐振。针对这一科学问题，本项目采用变流器端口频率特性，分别从电源之间基波频率谐振、电源子系统与负载子系统之间基波频率谐振两个层面展开研究，构建出微网基波频率谐振机理体系；同时基于该谐振机理体系，进一步分别从微网变流器内部控制结构改进和外接有源阻尼器两个方面对基波频率谐振抑制技术进行研究，提出有效的谐振抑制实现方法。本项目研究成果将为微网安全稳定运行提供关键技术保障，具有良好的应用前景。

针对下垂控制逆变器并联构成微网中基波频率谐振这一基本科学问题，本项目分别对电源之间、电源子系统与负载子系统之间基波频率谐振机理进行深入研究，进而提出相应的基波频率谐振抑制方法，主要研究成果如下。.在谐振机理方面，本项目先后建立了包含电压环动态在内的下垂控制逆变器以及电流环动态在内的功率控制逆变器的端口频率特性模型，并分析了下垂系数、电压调节器、锁相环、电流调节器等关键参数的影响；然后通过剖析各端口频率特性的矩阵特征，获得了能反映电源子系统谐振及微网系统谐振的特征轨迹解析式，进而提出了相应的简化稳定性判据；最后通过分析以上特征轨迹解析式中参数作用关系，揭示出电源子系统及微网系统谐振机理，为微网基波频率谐振预测及分析提供了重要依据。.在谐振抑制方面，本项目首先提出了改进型下垂控制策略，其通过对下垂控制逆变器控制结构中频率信号进行前馈，进而从根本上提升系统阻尼，有效解决了微网基波频率谐振抑制中的关键问题；同时本项目还对外接有源阻尼器进行了研究，提出了新型基于阻感支路的控制方法，有效提升系统谐振抑制的频率范围，为微网基波频率谐振抑制提供了重要手段。.本项目研究成果已发表国际期刊论文4篇，国内期刊论文1篇，国际会议论文3篇，国内会议论文1篇；项目负责人做大会特邀报告1次，技术专题讲座2次；获授权国家发明专利3项，国际期刊年度优秀论文一等奖1项。本项目相关研究成果已应用于2项校企合作课题中，为工程样机开发提供了重要支撑。