光伏并网逆变器故障诊断及孤岛检测

发布时间：2018-04-03 00:06

本文选题：光伏并网逆变器　切入点：单位功率因数　出处：《中国矿业大学》2014年硕士论文

【摘要】：光伏并网发电系统主要由光伏阵列、并网逆变器和电网组成，三者都有可能发生故障，其中的并网逆变器单个开关管开路故障诊断与孤岛检测则是本文要进行深入研究的内容。并网逆变器能否可靠运行影响到其本身与电网的安全。并网逆变器主电路是由若干开关器件组合而成，而开关器件存在短路和开路故障。本文对单管开路故障特征量进行分析并根据光伏并网逆变器特点，给出一种三相光伏并网逆变器开关器件开路故障诊断方法。逆变器开关器件发生开路故障时电网中性点与直流侧负极之间的电压与正常工作时的电压不同，将该电压作为特征量。结合光伏并网逆变器单位功率因数并网特点，以电网电压矢量角度为参考，对开路器件进行诊断。仿真和硬件实验结果表明，该方法可以在一个电流周期内准确定位开路故障器件。孤岛效应是所有分布式发电系统都要面临的一个问题，孤岛效应发生时，可能会给电网设备和人员带来不利影响。本文介绍了常用的被动式和主动式孤岛检测方法的原理。采用P×Q坐标系对被动式孤岛检测算法的检测盲区进行分析。针对P×Q坐标系的不足，采用Qf0×Cnorm坐标系对基于频率的孤岛检测算法的检测盲区进行分析。针对孤岛检测算法中的主动频率偏移法进行深入研究，详细给出单相与三相主动频率偏移法的实现过程。由于传统的主动频率偏移法会造成逆变器输出电能质量恶化，本文给出一种变反馈系数主动频率偏移法。在电网频率波动小的时候，采用小反馈系数；在电网频率波动大的时候，采用大反馈系数。仿真和硬件实验结果证明该方法在逆变器正常并网时对输出电流的影响较小，当孤岛效应发生时检测能力比较突出，在孤岛检测的时间上也符合国家相关标准的规定。
[Abstract]:The photovoltaic grid-connected generation system is mainly composed of photovoltaic array, grid-connected inverter and power grid, all of which are likely to have faults. The open circuit fault diagnosis and islanding detection of grid-connected inverter are the contents of this paper.Whether the grid-connected inverter can run reliably will affect the security of itself and the power grid.The main circuit of grid-connected inverter is composed of several switching devices, which have short circuit and open circuit faults.According to the characteristics of photovoltaic grid-connected inverter, an open-circuit fault diagnosis method for switching devices of three-phase photovoltaic grid-connected inverter is presented in this paper.The voltage between the neutral point and the negative electrode of DC side is different from the voltage in normal operation when the switching device of inverter occurs open circuit fault, and this voltage is regarded as the characteristic value.Combined with the characteristics of grid-connected photovoltaic inverter with unit power factor, the open circuit device is diagnosed based on the voltage vector angle of the grid.Simulation and hardware experiments show that this method can accurately locate the open circuit fault devices in a current cycle.Islanding effect is a problem that all distributed generation systems have to face. When the islanding effect occurs, it may bring adverse effects to power grid equipment and personnel.This paper introduces the principle of passive and active island detection methods.The blind spot of passive isolated island detection algorithm is analyzed in P 脳 Q coordinate system.Aiming at the deficiency of P 脳 Q coordinate system, Qf0 脳 Cnorm coordinate system is used to analyze the blind spot detection of isolated island detection algorithm based on frequency.The active frequency migration method in islanding detection algorithm is studied in detail, and the realization process of single-phase and three-phase active frequency migration method is given in detail.Since the traditional active frequency offset method will cause the deterioration of the output power quality of the inverter, a variable feedback coefficient active frequency offset method is presented in this paper.The small feedback coefficient is used when the frequency fluctuation is small, and the large feedback coefficient is used when the frequency fluctuation is large.The results of simulation and hardware experiments show that the method has little effect on the output current when the inverter is grid-connected normally, and the detection ability is more prominent when the islanding effect occurs, and the detection time of the islanding detection is in accordance with the relevant national standards.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464

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