弱电网暂态下光伏并网发电系统多目标协同控制研究

Photovoltaic (PV) power generation as a clean energy form can ameliorate energy structure and solve energy demand in the remote areas. But the grids of remote areas usually demonstrate weak grid characteristics, and cause negative influence on control performance, power quality and stability of grid-connected PV power generation system. The project focuses on the multi-degree of freedom, strongly nonlinear characteristics of weak grid, and investigates the following topics: Firstly, to establish the finite difference equations and form a weak grid mathematical model with multiple sources and loads. Secondly, to analyze the transient characteristics of weak grid and reveal the hybrid property, bilinear property and underactuated property of the weak grid model. Thirdly, to investigate the interactive influence degree and evaluation methods between weak grid and the grid-connected PV power generation system in power quality and stability. Fourthly, to propose some methods which can improve the grid-connected inverter current quality from aspects of novel topology,DC component inhibition,grid synchronization technology,islanding detection methods and reuse inverter's own resources. Fifthly, to explore comprehensive control strategies which can enhance the system transient stability, fault crossing ability and robustness combining with the bifurcation theory and grid on-line state detection function to realize stable operation of grid-connected PV power generation system in weak grid transient. Based on above research work, the related control methods of PV power generation system under weak grid transient are combined to form a theoretical system, which provides the theoretical foundation for high performance grid-connected PV power generation system to popularize in wider areas.

光伏发电作为一种清洁能源形式有利于改善能源结构、解决偏远地区的能源需求，但由于偏远地区电网通常呈现弱电网特性，会对光伏并网发电系统控制性能、电能质量和稳定性造成负面影响。本项目针对弱电网多自由度、强非线性特点，建立有限差分方程并组建多源、多负载弱电网数学模型，分析弱电网暂态特性并揭示其蕴含的混杂特性、双线性和欠驱动性等本质特性；确立弱电网与光伏并网发电系统在电能质量、稳定性方面的交互影响程度和评估方法；从新型拓扑结构、直流分量抑制、电网同步技术、孤岛检测方法和复用光伏并网逆变器自身资源等角度提出改善逆变器并网电流质量的具体措施，结合分叉理论和电网在线状态检测功能提出增强系统暂态稳定性、故障穿越能力和鲁棒性的综合控制策略，实现光伏并网发电系统在弱电网暂态下的稳健运行；在此基础上，将弱电网暂态下光伏发电系统相关控制方法形成理论体系，为高性能光伏并网发电系统向更广区域内推广应用奠定理论基础。

光伏发电作为一种清洁能源形式有利于改善能源结构、解决偏远地区的能源需求，但由于偏远地区电网通常呈现弱电网特性，会对光伏并网发电系统控制性能、电能质量和稳定性造成负面影响。针对光伏并网发电系统并入弱电网存在的问题，本项目主要研究内容包括：①弱电网建模与电气特性分析；②弱电网与光伏并网发电系统交互影响研究；③弱电网下提高光伏逆变器并网电流质量的方法研究；④弱电网暂态下光伏并网逆变器鲁棒性、稳定性研究。.重要研究成果主要包括：.结合弱电网定义和相关标准要求，利用DIgSILENT 仿真软件，搭建了33节点弱电网系统仿真模型。并以此为基础，分析了弱电网电气特性变化规律以及弱电网与光伏并网发电系统的交互影响因素和方面。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。提出了弱电网下光伏并网逆变器自适应准PRD控制方法，解决了由电网阻抗变化引起的并网电流质量下降和系统动态响应性能变差等问题。提出了弱电网下光伏并网逆变器锁频环同步方法，解决了传统过零检测锁相方法在电网电压振荡或畸变时容易出现锁相失效的问题。提出了弱电网下光伏并网逆变器虚拟电抗控制方法，解决了不改变实际滤波电感的电感量和滤波电容的电容量就可增大逆变器输出阻抗的问题。提出了单相全桥交错并联光伏并网逆变器拓扑结构，解决了传统并网逆变器存在并网电流纹波大，系统动态响应慢、滤波装置体积大等问题。提出了弱电网下光伏并网逆变器低电压穿越方法，解决了解决低电压穿越期间逆变器输出电流过流问题，同时为稳定弱电网的电压提供支撑作用。提出了弱电网下光伏并网逆变器无源控制方法，解决了逆变器在电网阻抗较大、电压不稳定等弱电网环境下的鲁棒性。.结合本项目的研究，培养硕士4名，在国际学术期刊、国际会议及国内核心期刊上发表论文10篇，被SCI收录1篇，EI收录8篇，获国家发明专利5项。.