基于逆变器的光伏系统孤岛检测方法研究

发布时间：2018-11-27 18:28

【摘要】：随着全球化石能源的开采,能源问题日益严峻。据统计,2050年左右,全球的石油资源将开采殆尽,届时依赖传统能源的国家将深受其害。因此,积极发展可再生能源,降低化石能源的使用率,提高太阳能等可再生能源的使用成为全球大部分国家解决能源危机的关键因素。光伏发电是太阳能使用的一个重要途径,光伏并网逆变器的研究将成为光伏发电的研究重点。光伏并网逆变器必须具备孤岛检测功能,因此本文重点研究基于逆变器的光伏系统孤岛检测方法。本文选取了移频式孤岛检测方法和基于电网阻抗的孤岛检测方法作为研究对象,研究了这两种方法各自的检测性能并提出了改进的新算法。首先研究了光伏系统控制策略,并对孤岛检测主动式方法中的频率偏移法进行了深入研究,从物理性质层面分析了影响移频式孤岛检测失效的原因及相关参数,并针对低电压穿越时Sandia频率偏移法的检测性能进行了分析,根据以上研究结果提出了改进算法；之后分析了基于电网阻抗的孤岛检测方法并提出了新的阻抗孤岛检测算法。具体的创新点如下： (1)提出了基于SFS的自适应孤岛检测算法,利用系统频率的变化自适应整定初始阶段系数cf0,该算法提高了孤岛检测性能,同时降低了光伏系统并网运行时的谐波畸变率。 (2)分析了锁相环在非对称条件下锁相不准的原因,并在模型中使用了改进的SPLL方法; (3)提出了新的基于电网阻抗变化电容孤岛检测技术,利用双阀值、分层投切电容的方式实现了快速准确检测孤岛,并能有效避免出现伪孤岛时误判。本文在MATLAB/Simulink平台上搭建了光伏发电系统模型,并在仿真模型中嵌入所提出的孤岛检测新算法,验证方法的有效性。分析结果表明,本文提出的方法与原算法比较,能快速检测孤岛,且对电网电能质量影响较小。
[Abstract]:With the exploitation of fossil energy in the world, the energy problem is becoming more and more serious. According to statistics, around 2050, the world's oil resources will be exhausted, when countries relying on traditional energy will suffer. Therefore, developing renewable energy actively, reducing the utilization rate of fossil energy and increasing the use of renewable energy such as solar energy become the key factors to solve the energy crisis in most countries in the world. Photovoltaic power generation is an important way to use solar energy. The research of grid-connected photovoltaic inverter will become the focus of photovoltaic power generation. Photovoltaic grid-connected inverter must have islanding detection function, so this paper focuses on the research of photovoltaic system islanding detection method based on inverter. In this paper, the method of moving frequency island detection and the detection method of isolated island based on grid impedance are selected as the research object. The detection performance of the two methods is studied and a new improved algorithm is proposed. First of all, the control strategy of photovoltaic system is studied, and the frequency offset method in active detection of isolated island detection is deeply studied. The reasons that affect the failure of frequency shift islanding detection and related parameters are analyzed from the aspect of physical properties. The detection performance of Sandia frequency offset method for low voltage traversing is analyzed, and an improved algorithm is proposed based on the above research results. Then, the detection method of isolated island based on grid impedance is analyzed and a new detection algorithm of impedance island is proposed. The specific innovations are as follows: (1) an adaptive islanding detection algorithm based on SFS is proposed. The algorithm improves the detection performance of islanding by adaptive tuning initial phase coefficient cf0,. At the same time, the harmonic distortion rate of photovoltaic system is reduced. (2) the reason of phase-locked loop is analyzed under asymmetric condition, and the improved SPLL method is used in the model. (3) A new detection technique of capacitive isolated island based on impedance variation of power network is proposed. The method of double threshold and layer switching capacitor is used to detect the isolated island quickly and accurately, and the false island can be avoided effectively. In this paper, a photovoltaic system model is built on MATLAB/Simulink platform, and a new islanding detection algorithm is embedded in the simulation model to verify the effectiveness of the method. The analysis results show that compared with the original algorithm, the proposed method can detect isolated islands quickly and has little effect on power quality.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464

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