提升弱电网光伏渗透极限关键技术研究

Power grids in remote area usually demonstrate weak grid characteristics, and the gradual increase of the photovoltaic (PV) permeability will cause negative influence on the weak grid power quality and stability. Focusing on the problems during weak grid research and technology blank, the project plan to start from the linearization of weak grid which is a nonlinear and a time-varying system and system modeling, study its electrical characteristics transformation rules and grid impedance real-time detection methods, and analyze interaction mechanism and restrictive relationship between PV generation system and weak grid in the area of power quality and stability; Study effective methods of improving PV generation system and weak grid power quality in the area of topology, control strategy and grid code; According to power quality restrictions, study PV permeability impact factors under different weak grid conditions and PV permeability limitation; Study steady-state and transient-state stability of weak grid from the demand side, and explore system instability mechanism; For the sake of improving PV power systems stability and weak grid stability, propose effective method that improves the ability of the weak grid to accept the PV capacity; Based on above research, summarize relevant weak grid control methods to form a theoretical system, which can provide a theoretical foundation to accelerate the continuous propulsion of grid-connected PV power generation project and the stable operation of power grid.

偏远地区电网通常呈现弱电网特性，而光伏渗透率的逐步提升对弱电网电能质量和稳定性造成负面影响。针对弱电网研究过程中出现的问题和技术空白，本项目拟从弱电网非线性时变系统线性化和系统建模入手，研究其电气特性变化规律和电网阻抗实时检测方法，分析光伏并网发电系统与弱电网在电能质量和稳定性方面的交互影响及制约关系；从拓扑结构、控制策略和并网导则三方面研究提高光伏并网发电系统和弱电网电能质量的有效方法；以电能质量为约束条件研究弱电网下的光伏渗透率影响因素和光伏渗透极限；从需求侧出发研究弱电网稳态和暂态稳定性，探索系统失稳机理；从提高光伏并网发电系统自身稳定性和弱电网稳定性两方面入手，结合电力弹簧、负载管理策略提出提高弱电网接纳光伏容量能力的有效方法；在此基础上，将弱电网相关控制方法形成理论体系，为推进光伏并网工程建设及电网稳健运行奠定理论基础。

随着可再生能源的不断利用，光伏渗透率的逐步提升对弱电网的电能质量和稳定性造成了严重负面影响。针对如何提升弱电网光伏渗透极限的关键问题，本项目从弱电网系统建模及阻抗检测方法、不同光伏渗透率下的弱电网电能质量、弱电网光伏渗透率及渗透极限研究、高渗透率光伏弱电网的鲁棒性与稳定性四个方面开展研究。主要研究成果包括：(1)建立了基于DIgSILENT仿真软件的弱电网模型，该建模方法对含新能源的低压配电网系统建模具有普遍指导意义；(2)提出了基于双谐波注入的弱电网阻抗在线检测方法，解决了常规单谐波电流注入法精度不高且运算复杂的问题；(3)提出了弱电网下光伏并网逆变器改进型电压功率控制方法，提高了弱电网电能质量，并实现了弱电网下光伏并网逆变器的离并网无缝切换，解决了传统控制策略在模式切换时存在较大的电压电流冲击和波形畸变等问题；(4)提出了弱电网下基于无源理论和功率前馈的并网控制方法，提高了系统的动态响应速度和鲁棒性，同时采用复合型虚拟同步机（VSG）控制方法，实现了弱电网的稳定运行；(5)依据弱电网下光伏渗透率计算方法，采用增加储能、无功补偿、PQ-U并网逆变控制方法、优化光伏发电系统在弱电网中的布局和容量，有效提升了光伏发电系统在弱电网中的渗透率。.截至目前，在国内外高水平期刊以及国际学术会议上共发表SCI或EI检索学术论文20篇，授权国家发明专利7项，培养研究生12名，其中博士研究生2名，硕士研究生10名。项目组成员参加相关国际学术会议6次，引进师资博士后1名，公派访问学者1名。