基于分布式并网逆变器的微电网多谐振现象的建模分析和抑制机理研究

For the high penetration of distributed grid-connected inverters, microgrids are easy to have internal resonances from individual inverters, partial resonances due to the interaction of multiple inverters, and global system resonances of microgrids. Aiming at the harmonic interaction and resonance problems among multiple inverters, loads and the grid in microgrids, in this project a systematic modeling method for grid-connected inverters, which is suitable for the resonance research of microgrids, will be derived based on the proposed models of inverter output-characteristics by introducing nonlinear factors. With the established resonant-network model of microgrids, the root causes of multiple resonances in microgrid will be explored with respect to various static and dynamic stimulation factors and complex working conditions. Mitigation methods and common technology for the resonances in microgrids will be proposed based on improved control of various types of inverters. The influence on resonance problems and the application features on oscillation damping from various types of grid-connected inverters in microgrids will be addressed. Consequently, it will be expected to achieve core technology for the next-generation of grid-connected inverters for microgrid appplications and it will also be able to technically support to realization of reliable and stable operation of multiple distributed power generations in the grid, and to provide research basis for the reduction of grid harmonics, stability improvement of grids and applications of renewable energy.

由于分布式并网逆变器的高渗透率，微电网系统中容易引发单逆变器本体谐振、多逆变器交互的局部谐振以及微电网层面的全局谐振。针对微电网中多并网逆变器-电网-负荷之间潜在的谐波交互与谐振问题，探索引入非线性因素的逆变器外特性建模方法，建立适于微电网谐振研究的并网逆变器模型；基于提出的微电网谐振模型，发现微电网在不同静、动态谐振激励条件和复杂工况下多谐振现象的产生机理；探究基于不同控制类型逆变器算法改进的微电网谐振抑制方法与共性技术，阐明各控制型并网逆变器在微电网应用中对谐振影响及谐振抑制的特点。从而获得面向微电网应用的新一代并网逆变器核心关键技术，为实现分布式多并网发电单元在电网的可靠、稳定工作提供技术支持，为降低电网谐波成份，改善电网稳定性和促进新能源的并网应用等提供研究基础。

由于分布式并网逆变器的高渗透率，微电网系统中容易引发单逆变器本体谐振、多逆变器交互的局部谐振以及微电网层面的全局谐振。针对微电网中多并网逆变器-电网-负荷之间潜在的谐波交互与谐振问题，探索了电流控制型、电压控制型（VSG型、下垂控制型）并网逆变器的外特性建模方法，分析了其输出阻抗模型对关键参数扰动的敏感性，建立了适于不同控制类型逆变器组网下微电网谐振机理与抑制研究的阻抗分析模型；基于所建立的微电网谐振模型，详细阐述了VSG逆变器的并网低频振荡机理、高频逆-网交互谐振机理，并揭示了VSG集群的逆网交互谐振特性；重点研究了孤岛微电网中下垂控制逆变器的集群效应，以及与容性负荷之间的阻抗交互作用；为改善不同控制类型逆变器集群组网的稳定性提供研究思路。通过对比电流控制型、VSG型、下垂控制型逆变器集群和电网的交互特性，阐明各控制型并网逆变器在微电网应用中对谐振影响及谐振抑制的特点。揭示了VSG集群并网系统呈现的整体低阻抗频谱特性有利于弱化逆-网的交互影响，且并联台数的变化对谐振交互的频率区间影响很小；揭示了下垂控制型逆变器并联台数增多有助于提升孤岛微电网的稳定性，逆变器间的环流谐振由电压环主控制参数影响。同时，针对基于电流控制型的并网逆变器，提出了基于两种阻抗重塑基本形式的系列控制环路拓扑结构，提升并网稳定性；针对VSG逆变器整体低输出阻抗特性，提出了一种基于多谐振虚拟同步发电机控制结构的并网控制策略，保留VSG优势的同时可有效抑制并网电流的谐波；针对VSG并网逆变器，提出了一种基于双自由度协调控制的参数自适应控制策略改善低频振荡响应性能；针对下垂控制逆变器间的环流谐振问题，揭示了LC滤波器电容容值的增加有助于减小环流谐振的影响。本项目研究获得的面向微电网应用的不同控制类型并网逆变器的适用特点和并网稳定增强型关键技术，为实现分布式多并网发电单元在电网的可靠、稳定工作提供技术支持，为降低电网谐波成份，改善电网稳定性和促进新能源的并网应用等提供研究基础。