电力系统电能质量分析方法的研究

【作者】 肖冰；

【导师】 梁军；

【作者基本信息】 山东大学 ， 电力电子与电力传动， 2005， 硕士

【摘要】 随着科技的迅猛发展,电网负荷加大,特别是非线性负荷及冲击性、波动性负荷,使得电网出现谐波、电压跌落、电压波动和闪变、三相不平衡、频率偏移等电能质量问题。 本论文首先介绍了电能质量问题的定义与种类、危害和补偿方法。在各种电能质量问题中,电压跌落是危害最严重的动态电能质量问题,而且随着大功率冲击性、波动性负荷大量接入电网,使得某些供电系统的电压波动达到了不能容忍的程度。这表明动态电能质量问题已成为目前影响供电可靠性的主要干扰。然而,人们对于电能质量中诸如谐波、电压偏差、频率偏移等方面的研究相对电压跌落、电压波动和闪变来说要多得多,研究得也较成熟。对电压跌落、电压波动和闪变的研究则起步比较晚,还存在许多问题。因此,本论文确定将电能质量问题中的电压跌落和电压波动及闪变现象作为主要研究对象。 对于电压跌落,将各文献上提出的检测算法作了分析和比较指出其优缺点,进而确定以派克变换理论为基础,提出一种基波电压正序分量的离散检测新算法,对dqO坐标系下直流分量的提取作了改进,用复化积分代替了滤波器滤除谐波。该方法不受电压畸变影响,并能应用于具有不对称负荷的情况,具有动态响应时间为半个工频周期,检测结果精度高而且稳定,易于在DSP编程实现等优点。采用Matlab对电压跌落检测算法进行研究。实验结果表明该方法能正确地检测电压跌落的幅值、持续时间和相位跳变的信息。 对于电压波动和闪变,首先总结了各文献上提出的检测算法,提出了利用Hilbert变换（HT）对配电系统中的电压闪变水平进行实时检测,该方法在数学上更简单,实现更容易。而且,HT能够检测配电系统中的电压闪变和系统频率的变化,精度高,使电压闪变补偿装置更容易控制。采用了不同的电压闪变信号验证该方法。通过Matlab仿真,简述了影响检测精度的不同因素。仿真结果验证了HT的检测能力,表明HT在检测电压闪变方面具有良好的性能。 根据国际电工委员会（IEC）的有关标准,衡量电压波动和闪变的主要指标是短时间闪变值P_st,该文又研究了IEC闪变仪的模拟和数字化实现。首先介绍了更多还原

【Abstract】 With the rapid development of new technology, the sudden increase of loads, especially the incessant increase of nonlinear, impulsive and fluctuating loads, power quality problems often occur, such as harmonic, voltage sag, voltage fluctuation and flicker, unsymmetrical voltage, etc..This paper firstly introduces the definition, classification, harms, and compensating strategies of power quality problems. In various power quality problems, voltage sags are the worst dynamic power quality problems. With high-power impulsive and fluctuating loads accessing electrical network, voltage fluctuations can’t be tolerated in some power supply networks. This indicates dynamic power quality problems have become primary disturbances influencing supply reliability now. But the research in those aspects such as harmonic, voltage deviation, frequency deviation and etc. of power quality is more than in voltage sag, voltage fluctuation and flicker. The research about voltage sag, voltage fluctuation and flicker started so late and still has many problems. So this paper mostly studies the algorithm of detecting voltage sag, voltage fluctuation and flicker in power quality problems.In order to detect voltage sags, this paper makes analysis and comparison among the methods of detecting voltage sags in every relative literature, points out their advantages and shortcomings. And then this paper proposes a new discrete method that is used to detect fundamental positive-sequence voltage based on park transformation. With complex integral algorithm replacing filter, the accuracy of detecting direct current component can be improved. This method can’t be influenced by voltage distortion, and can be apply on the case of unsymmetrical loads. Its dynamic response time is half of fundamental period. The result of this method detecting voltage sags is stable, and possesses very high calculation accuracy. This method can be realized easily. Matlab is adopted to simulate the algorithm fordetecting voltage sags. The simulation result indicates that this method can accurately detect the magnitude, duration and phase jump information of voltage sags.In order to detect voltage fluctuation and flicker, this paper firstly summarizes methods of detecting voltage fluctuation and flicker in every relative literature. Then, the Hilbert transform (HT) are introduced in this paper as an effective and real-time approach for detecting the voltage flicker levels in distribution systems. Compared with the commonly used algorithms in the literature, the proposed technique is simpler in math, and is implemented easier. Moreover, the HT is capable of detecting the variations of the voltage flicker and supply frequency in distribution systems with high precision. Such accurate detecting facilitates the implementation of the control of flicker mitigation devices. Many different voltage flicker signals are adopted to validate the approach. Matlab simulations of the proposed approach for detecting voltage flicker that profile the different factors affecting tracking accuracy are presented. The simulation results are provided to verify the detecting capabilities of the HT and indicate the superior performance of the HT in detecting voltage flicker.According to IEC standards involved, short-time flicker Pst is primary indexscaling voltage fluctuation and flicker. This paper studies the analogue and digital realization of IEC flickermeter. Detecting methods in flickermeters are introduced. Then the principle of IEC flickermeter and both the analogue and digital realization methods are expounded as emphases. At the same time, all parts of flickermeter are designed. Linear interpolation method is adopted to calculate Pst. Matlab simulationand calculation results indicate that this flickermeter meets IEC’s accuracy standards. Finally, this paper is summarized, and prospect of this topic is viewed.更多还原