Optimization Research Of Active Voltage Arc Extinguishing Method Based On Double Closed Loop Control

In recent years,with the wide application of cable lines and power electronic equipment,the fault current of distribution network contains not only a large number of capactive currents to the ground,but also a large number of active and harmonic components when single-phase grounding fault occurs.The active componented and harmonic component can not be compensated by arc suppression coil,which leads to the large residual current after the single-phase grounding fault in distribution network,and the arc at the fault point is difficult to extinguish by itself.To this end,this paper presents an active voltage arc suppression control scheme based on closed-loop control,which achieves the goal of zero-residual flow at the fault point by clamping the fault phase voltage to a target value.In order to achieve this goal,it is necessary to identify the fault phase accurately,design the closed-loop control method and optimize the scheme of traditional active voltage arc suppression in low resistance grounding.In order to solve the above technical problems,this paper first analyzes the arc extinction mechanism of the small current grounding system and active voltage arc suppression,and gives the overall design scheme.Subsequently,the research on fault phase identification of asymmetric power grid is carried out.The asymmetry of the system is eliminated by injecting a current into the neutral point,and the accurate identification of the fault phase is realized by using the angle relationship between the neutral point voltage and the A-phase power supply voltage.In order to control the fault phase voltage to zero,the closed-loop control technology is adopted.The control algorithm based on double closed-loop quasi-proportional resonant controller is established,and the open-loop and closed-loop frequency characteristics of the outer voltage loop and the inner current loop are analyzed.The phenomenon of residual current increasing instead of decreasing in the case of active voltage arc suppression low-resistance grounding fault is analyzed theoretically,and the influence factors of residual current are verified by simulation.A new algorithm of voltage arc suppression is proposed.The functional relationship between the transition resistance and neutral point voltage and A-phase power supply voltage which is used to calculate it.When the transition resistance is less than the threshold value,the fault phase voltage is controlled in the voltage drop of the fault line to ensure that the fault point current will not increase.The optimized voltage arc suppression algorithm is simple to measure and easy to control.It has good arc suppression performance in low resistance and high resistance grounding faults.Finally,the relevant models are built by using the simulation software of Matlab/Simulink,and the above theoretical methods are verified by simulation.