基于虚拟阻抗和锁相环的孤岛检测技术

An islanding detection based on virtual impedance and phase-locked loop

针对被动孤岛检测存在较大检测盲区,而传统的主动检测法会对电网电能质量造成影响,提出了一种结合锁相环和虚拟阻抗的孤岛检测方法。该方法通过锁相环的输出跟随本地负载谐振频率变化的特性,来对孤岛进行检测。正常并网时,锁相环的输出会稳定在线路频率上;而处于孤岛时,锁相环的输出则会跳变到本地负载的谐振频率处。同时,引入了虚拟阻抗技术对此方法进行了完善,应对频率出现匹配的情况。通过Matlab仿真和RT-LAB半实物仿真平台进行了实验验证,验证了理论推导的正确性及所提孤岛检测方法的有效性。

There is a large None Detection Zone(NDZ)for passive islanding detection,and the traditional active detection method will affect the power quality of the power grid.In this paper,a method of islanding detection based on Phase-Locked Loop(PLL)and virtual impedance is proposed.The method uses the output of the PLL to follow the resonant frequency of the local load to detect the islanded condition.When the grid is connected properly,the output of the PLL will stabilize at the line frequency.When it is on the islanded condition,the output of the PLL will jump to the resonant frequency of the local load.At the same time,the technology of the virtual impedance is used to help the method to deal with the frequency matching situation.Both the Matlab simulation and the RT-LAB hardware-in-loop simulation are used to verify the correctness of theoretical derivation and the effectiveness of the proposed island detection method.