Based on the technology of passive islanding detection,a method of islanding detection is proposed which applies the discrete wavelet transform. According to the principle that the inverter-side power quality is unequal to the grid-side power quality at PCC,the characteristic harmonic high-frequency components of islanding can be extracted by the wavelet transform of voltages at PCC. Theoretically,the non-detection zone can be thoroughly eliminated by the extraction and identification of microscopic variables. Three types of distributed generation system are set in the environment of MATLAB/Simulink and simulative results show that,the existence of islanding is rapidly detected and the detection device functions properly under different operating conditions:voltage disturbance,different load types,load on-off switching, etc., which verifies the correctness of the proposed method.%在被动式孤岛检测技术的基础上,提出一种新的基于离散小波变换的孤岛检测方法.根据公共连接点( PCC)逆变器侧和主网侧电能质量不相等的原理,通过对PCC处电压进行小波变换提取出孤岛发生的特征谐波高频信号,理论上通过微观变量的提取和识别可彻底消除非检测区.在MATLAB/Simulink环境下,搭建3套分布式发电系统,仿真结果验证了所提方法的正确性,并表明在电网电压波动以及各类型负荷运行、投切等扰动下,检测装置不会误动作,能够迅速检测到孤岛的发生.
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