【作者】 吴红春；

【导师】 周林；

【作者基本信息】 重庆大学 ， 电气工程， 2008， 硕士

【摘要】 电压暂降是动态电能质量问题中最受关注的热点之一。如今,大量新型电力电子设备得到广泛使用,这些设备特别是敏感电力电子设备的正常工作对电网电能质量(主要是电压暂降)的要求越来越高,而且电压暂降在电网中又具有一定的传播性。因此,无论从电网还是用户都迫切需要对电压暂降进行研究和治理。对电压暂降的检测是解决电压暂降的前提条件,其检测精度、速度及抗干扰能力直接关系到电压暂降的分析、控制和补偿。故本论文主要对电压暂降的检测方法进行研究。动态电压恢复器(DVR)是应用于电压暂降最有效,也是应用得最多的设备。DVR采用的检测方法是虚构的三相DQ分解法,本文对此方法进行分析总结后指出了它的一些不足。在总结分析目前应用于电压暂降的检测方法的基础上提出了一种新的电压暂降的检测方法,即基于小波及DQ算法的电压暂降检测方法。围绕电压暂降的所有特征量展开,进行理论推导,新DQ算法是利用单相电压进行构造来求解,它具有数据无延时的特点。而虚构三相DQ分解法是用单相数据延迟60度并经过一定的处理得到另外两相电压。进行比较得出的结论是此新方法可以克服原虚构三相DQ分解法的不足。基于理论分析对小波及DQ算法的电压暂降检测方法进行仿真,考虑了与电压暂降的相关扰动。以小波在奇异性检测方面的独特优势对电压暂降信号中的噪声进行预处理,同时对电压暂降信号进行精确定位,利用小波的分频特性提取电压暂降信号中的低频扰动。仿真验证了新方法对原三相DQ分解法不能处理信号起始60度范围内数据的同步性、此范围内存在的扰动的判定及暂降过程中的低频扰动等问题的有效性。另外,新DQ算法在检测的精度上也有了提高,表现在精确检测到暂降的起始和结束时间。并且此小波与新DQ算法结合的方法可以完整地实现对电压暂降幅值、持续时间、相角偏移、电网频率偏移、噪声干扰等的检测。在仿真中还发现,原虚构三相DQ变换在检测电压暂降时,起始时刻和暂降的开始与结束时刻均存在扰动,且扰动幅度较大,到达稳定的时间较长。而采用新方法后,检测暂降幅值和相角均很快达到平稳状态。更多还原

【Abstract】 The voltage sag is one of most hot topics in dynamic electric energy problems. Nowadays, masses of new power and electron facilities have been put into use widely by people, and the normal working of those facilities, especially those sensitive ones, require a high quality of electric network and power, chiefly the voltage sag. Moreover, the voltage sag can spread in the electric network. So people have every reason to research and develop the voltage sag. However, before developing the voltage sag, people have to test it, because the results of the test would directly influence its development. On account of the above, this essay will chiefly focus on the test methods of the voltage sags.DVR is the most effective and popular equipment in the voltage sag. And it uses the fictitious three-phase DQ decomposition method. For having found some deficiencies of that method, this essay puts forward a new kind of the voltage sag test method—based on the wavelet and DQ algorithm .This new DQ algorithm grounds on unidirectional voltage’s no time prolong structure, nevertheless, the fictitious three-phase DQ decomposition method can only get the other two voltage depends on the processing single-phase data. According to their different principles, the conclusion can be drew that the new method can overcome the latter’s shortage.Taking the voltage sag related perturbation into consideration, during the progress of emulation, people can use the small wave’s unique dominance in singularity testing to preprocess the voltage sag signal noise, and to pinpoint the voltage sag signal at the same time, and then utilize small wave’s frequency division to extract low-frequency perturbation among the voltage sag signal. The emulation of this new method proves the lack of the synchronism and availability in the three-phase DQ decomposition method. On the other hand, the new DQ algorithm increases the testing accuracy, and the combination of the small wave and the new DQ algorithm can test the voltage sag completely in many aspects, such as the time of duration, phase-angle offset, noise interference and so on. The emulation also shows the small wave and DQ algorithm based method can arrived stable condition sooner than the fictitious three-phase DQ decomposition method.更多还原