Research On Active Arc Suppression Method For Grounding Fault Of Distribution Network Based On Current Injection

With the heavy use of power cables and non-linear power electronics facilities in China,when a ground fault occurs in the distribution network system,not only capacitive currents but also some harmonic currents and active currents are present in the ground fault residual current.However,the traditional arc suppression coil can only compensate the capacitive current in the ground residual current,and cannot compensate the harmonic current and active current.This will inevitably cause the ground residual current value to be still large during the system ground fault,and the ground arc cannot extinguish itself.Therefore,there is an urgent need to study the arc suppression of flexible arc suppression coils in ground faults,so that the safety and stability of the power grid system can be significantly improved.To this end,this dissertation first discusses the background and significance of active arc suppression in small current grounding system.Secondly,the asymmetric voltage,neutral point displacement voltage during the normal operation of the small current grounding system,and the linear resistance grounding and arc grounding that occur when the system fails is made mathematical derivation and explanation.At the same time,arc grounding model is built to analyze its fault characteristics.Then for the asymmetrical power grid system when single-phase grounding is affected by the value of the transition resistance,the trajectory diagram of the zero-sequence voltage amplitude and phase is optimization analyzed.The asymmetry of the power grid is compensated by injecting a certain current value into the neutral point.Furthermore,a method of phase identification based on zero-sequence voltage phase angle variation is introduced.Next,the detailed analysis process of the arc suppression mechanism when a single-phase ground fault occurs in the distribution network system is given.Aiming at the advantages of active current arc suppression and active voltage arc suppression under different grounding resistances,a method to predict the value of grounding resistance is given to select between active current arc suppression and active voltage arc suppression.At the same time,the optimization principle of binary gradient descent method is introduced,and the existence of optimization of the optimal value of the injection current is proved.A kind of active voltage arc suppression based on the optimization control of binary gradient descent method is given,and the optimal current is injected into the neutral point of the system to achieve the stable arc extinction effect.Finally,Matlab/Simulink software is used to build the above mentioned related simulation models.The simulation experimental data also confirmed the feasibility and effectiveness of the principles introduced in this dissertation.In order to achieve the goal of clamping the system ground fault phase voltage to zero,this dissertation first solves the identification of the ground fault phase,then completes the prediction of the ground resistance,and finally obtains optimal current value injected into the neutral point of the system by precise optimization iteration.A relatively complete set of active arc suppression process is given.The dissertation has 59 pictures,8 tables,81 references.