Study on detection method of distorted voltage sag in distribution network under the background of incorporating new energy

An advanced voltage sag detection method and compensation technique can improve the power quality of the distribution network to a entirely new level. A high performance voltage sag detection method demands fast response and good accuracy, even detecting distorted grid voltage sag caused by new energy accessing to distribution network. The voltage sag detection method, based on sliding window iterative discrete fourier transfer (DFT) algorithm, has excellent filtering ability but long detection time. On the other hand, the voltage sag detection method, based on nonrecursive DFT algorithm, has short detection time but poor filtering ability. Aiming to meet the requirements of fast response and good accuracy, this paper proposed a voltage sag detection method based on improved nonrecursive DFT algorithm. By means of disturbance filter, which is combined with several notch filters and a low-pass filter, the filter characteristic of nonrecursive DFT algorithm has been improved, and the detection delay time is reduced. The proposed algorithm can guarantee shorter detection time and higher detection accuracy. (paper)