Study On Detect And Trace Of Voltage Sag Of Power Grid With Distributed Generation

The voltage sag due to the frequent occurrence, the huge harm and economic loss has become the most serious power quality problems in modern society. With the increasing primary energy depletion and environmental pollution is worsening, driven by the dual pressures, new sustainable renewable energy has become the first choice of people and with the development of the smart grid, gradually, a lot of distributed generations are widely connected in the distribution network, which changed the operation mode of the distribution networks and direction of the trend, making the distribution network developed into a complex multi-supply network, the several existing detection and traceability methods has not met accurately. Voltage sag of distributed generations grid could be quickly and accurately detected and traceabilitied to develop power quality, improve reliability and electricity market process has very important significance.At first, this paper introduces the basic concepts of transient power quality and voltage sag of the concept and main features and classified the DG; then, from the theoretical analysis of the distribution network in two different ground ways, DG forming a voltage sag mechanismand under different conditions from distributed power capacity, location, etc. that impact fault short circuit current and voltage sag and summed up the law when connected in distribution network. For the common voltage drop detection methods were compared, then to conclude the advantages and disadvantages and different applicable scope of different detection methods. Improved dq method can accurately detect the amplitude and phase angle jump of the voltage sag, However, the starting and ending time of falling can't effective and accurate detection, and therefore, the paper use wavelet transform local singularity characteristics to accurately and effectively detect the starting and ending time of the the voltage sag, simulation results show that the wavelet transform to detect the start and end time of the voltage sag with high accuracy.Against the existing matrix positioning methods can not effectively trace of fault localization of distribution network with distributed generations. Based on feeder terminal unit, the paper presents a modified adaptive matrix to initially identify fault zone where the voltage sag interference source is located. In addition, the paper also used a hybrid algorithm of differential evolution algorithm and bat algorithm for fault-section location in distribution network with distributed generations, the introduction of differential evolution algorithm in the bat, so that the bat algorithm has the advantage of the differential algorithm.. Finally, by building a new switch function and section location evaluation model in distribution networkwith DG, which solved the problem of fault location in distribution network with DG. The simulation results indicate that the hybrid algorithm is capable of accurately and effectively trace of both single and multiple voltage sag source, and better fault tolerance.Then,determine the voltage sag source where the fault zone is located through the fault location method, the use of improved impedance method to trace of the voltage sag source. The simulation results show that this method has the advantage of a small amount of calculation and a good accuracy.