Voltage Sag Disturbance Recognition And The Detection Method Of Voltage Sags

With the development of electricity and large-scale applications of different kinds of sensitive equipments, people pay more and more attention on the impact of voltage sags.Different phenomenons of voltage sags caused by different sag sources are analyzed and two methods of voltage sag disturbance recognition based on RMS values and Mamdani fuzzy inference is introduced separately in this paper. The results can be gotten using the method based on RMS values when the instantaneous values of voltage can not be given by the monitor, and the Mamdani fuzzy method overcomes the limitation of the single threshold using the instantaneous values of voltage. The corrections of these two methods are proved by some simulations taken in the paper.At the same time, a voltage sag detection method suitable for DVR based on p-q-r theory and morphological filter is introduced in this paper. There is no PLL in the method, so the delay and error can be reduced. Because there are mainly some Boolean operations and a few sum or subtract in the morphological filter, comparing with the normal low-pass filters, the computation and the time delay are simple and short. The simulations prove the rapidity and reliability of this method.