【作者】 刘芙蓉；

【导师】 康勇；

【作者基本信息】 华中科技大学 ， 电力电子与电力传动， 2008， 博士

【摘要】 近年来随着能源问题和环境问题的日益严峻,新能源获得了各国政府的大力支持,并网光伏发电系统日益增多。孤岛检测是并网光伏系统必须具备的功能,其实现方法分为两类:被动式孤岛检测方法和主动式孤岛检测方法。被动式孤岛检测方法通过监控公共点电压及参数变化来识别孤岛,实现简单、成本低,但检测盲区较大。主动式孤岛检测方法对系统施加一定扰动,使孤岛状态能通过参数变化反应出来而得到辨识,大大减小了孤岛检测的盲区,但实现相对复杂、容易对电网电能质量产生不良影响。主动移频式孤岛检测方法、主动移相式孤岛检测方法、电压正反馈式孤岛检测方法这三种方法是公认的高效率、低成本的主动式孤岛检测方法。该文围绕这三种方法展开了深入研究,主要内容有:(1)提出了一种实用的孤岛检测盲区描述方法,用于对主动移频式孤岛检测方法和主动移相式孤岛检测方法的检测盲区进行描述。一方面,将检测盲区用平面图精确表示,便于不同孤岛检测算法检测能力的比较,另一方面,盲区位置的负载参数具有唯一性,方便了实验验证。(2)对主动移频式孤岛检测方法和主动移相式孤岛检测方法的检测盲区进行了分析、比较,得出孤岛检测算法参数与盲区分布间的关系,找到了算法中影响孤岛检测性能的关键因素,并给出了工程应用中优化孤岛检测算法的解析依据。(3)结合算法优化,对主动移频/相式孤岛检测方法产生的逆变器输出电流畸变进行了讨论,综合电能质量、孤岛检测能力两方面对主动移频式孤岛检测方法与主动移相式孤岛检测方法的优劣进行了比较。(4)建立了电压正反馈式孤岛检测方法的数学模型,分析了电压正反馈式孤岛检测方法的适用对象、特点、导致孤岛检测失败的因素,推导并给出了电压正反馈式孤岛检测方法成功的充分条件,以及解析关系。(5)分析了多逆变器并网运行对孤岛检测的影响,特别是并网逆变器采用不同孤岛检测方法对孤岛检测能力的影响,以及相应对策。更多还原

【Abstract】 Grid-connected photovoltaic systems are increasingly applied due to the limitation of fossil fuels in terms of sustainability and pollution. For the interconnection of PV systems and utility grids, islanding detection is an indispensable feature for PV-systems and many algorithms have been developed in the past decade. These methods may be divided into two basic categories: passive methods and active ones. Among them frequency-shift techniques, phase-shift techniques and voltage-shift techniques are good choice because of high effectiveness and low cost. The thesis discussed some key issues of these three techniques:(1) None-detection zones (NDZ) are important index to evaluate the performance of anti-islanding methods. A proper mapping method is important as it set up relationship between NDZ and load characters, which are complex in real world. A new mapping method is proposed which can fully depict the performance of anti-islanding in a plain plot, which is compliance with IEEE standard certification.(2) The NDZs of frequency-shift techniques and phase-shift techniques are analysed in the thesis. Based on analysis the relationship between NDZ and algorithm parameters are decuced, which can be expressed as a mathematics inequation and provide range for algorithm parameters to gurantee anti-islanding protection. The inequation is simple and accurate, thus can be taken as a good guideline in algorithm parameters setting.(3) The influence of anti-islanding algorithm on inverter output current distortion is discussed. The current total harmonics distortion increased by anti-islanding is discussed in conjunction with anti-islanding algorithm optimization. It provides comparison between phase-shift techniques and frequency-shift techniques on anti-islanding efficiency as well as the adverse impact on power quality.(4) A mathematics model of voltage-shift technology is proposed. Based on it, the characteristics of voltage-shift technology are discussed. Key factor that lead to anti-islanding failure is sugguested and a mathematic inequation to gurantee anti-islanding protection is provided.(5) Islanding detection assessment of multi-inverter systems are developed, especially some new issues result from parallel operation. Possible solutions are suggested at the end of discussion.更多还原