Magnetic Field Analysis And Structural Optimization Design Of Fast Repulsion Mechanism

With the development of flexible DC power transmission and distribution technology,multi-terminal DC power grids are the trend and direction of future smart grid development.However,multi-terminal DC power transmission systems have no current zero crossings and low circuit inductance.Once a fault occurs,the short-circuit current rises at a faster rate,high peak value.As a key equipment for DC grid control and protection,the rapidity of DC circuit breaker is the key to ensure successful interruption.The fast repulsion mechanism(ERM)has the advantages of fast response and high accuracy,and is widely used in the field of DC breaking,but its energy conversion efficiency and high-voltage long-stroke drive issues have become its main limiting factors.This article first analyzes the topology and working principle of the existing ERM,summarizes the advantages of each topology and the applicable field.From the aspect of structure,the design scheme of high-voltage long-stroke mechanism is put forward.Theoretical analysis and magnetic field are carried out for the double-coil ERM,it is found that the energy of the magnetic field is consumed seriously in the air,and the density of the magnetic field is closely related to the magnetic permeability of the medium.A magnetic field optimization scheme is proposed to increase the driving efficiency of the magnetically conductive material.Secondly,in order to design a high-efficiency ERM,this paper establishes a simulation model of ERM with double-coil structure based on the finite element analysis method.Firstly,the influence of coil turns,height and axial turns on the dynamic characteristics of fast repulsion mechanism is simulated and the optimal parameters of coil are determined.Then,in order to avoid the problems of magnetic saturation and power loss,the coil disc skeleton is analyzed and optimized from the aspects of magnetic conductive materials and structural parameters,and the optimal design parameters of the coil disc magnetic conductive components are obtained.Finally,based on the simulation analysis and optimization results,an experimental prototype and experimental test platform for a double coil ERM based on permanent magnet retention is established to verify the feasibility of the optimization scheme.Finally,the design idea of series hybrid repulsion mechanism(SHRM)suitable for long stroke is proposed.Based on the finite element analysis method,the simulation model is established.The motion characteristics of SHRM,wire disc mechanism and solenoid mechanism are compared and analyzed.The transient magnetic field distribution of SHRM and the influence law between mechanisms are studied to verify its feasibility.Then,a new type of hybrid repulsion mechanism(NHRM)is proposed,which provides a reference for the development of the high-stroke circuit breaker longstroke rapid repulsion mechanism.