Design And Analysis Of Quick Operating Mechanism Of Mechanical Low-voltage DC Vacuum Circuit Breaker

In the DC power system,when a fault occurs,the fault current rises rapidly.In order to prevent the expansion of fault scope and ensure the stability and reliability of system operation,higher requirements are put forward for the fast mechanism of mechanical DC vacuum circuit breaker.In this dissertation,the fast operating mechanism for mechanical low-voltage DC vacuum circuit breaker is taken as the research object,and the rapid operating mechanism structure optimization design and the mechanical characteristic have been analyzed.The main research work includes:Research on the model and design method of electromagnetic machine system with vacuum interrupter and fast mechanism.Based on the finite element electromagnetic calculation,the reaction force and the work done by the reaction force are quantitatively analyzed,and the topology and parameter design scheme of the external circuit of the repulsive force structure are proposed.The physical mathematical model of the coil repulsive disk and the equivalent second-order circuit model of the mutual inductance coupling circuit are established,and the field circuit coupling analysis is carried out.In order to ensure the interrupting speed of the repulsive structure,the RLC second-order circuit in series should be operated in underdamped state.Research on optimization design method of fast operating mechanism based on multi-objective particle swarm optimization algorithm.The parameters of external circuit with repulsion structure are taken as optimization variables.And the objective of the optimization design is to minimize the time for reaching the peak value of the electromagnetic repulsion force and maximize the work of the electromagnetic repulsion force in its action time.The working condition of the underdamped circuit is beyond the constraint condition.The adaptive mesh multi-objective particle swarm optimization algorithm is used to optimize the mechanism parameters,and the parameter combination of the concentrated repulsive force of the non-dominated solution satisfying the design requirements is obtained.Based on the above model modeling,numerical simulation and optimization combined with the whole system parameters of the fast mechanism,the finite element software Maxwell is used to simulate the mechanical characteristics to verify the feasibility of the design method.In addition,based on the simulation analysis of the influence of coil shell material and shell structure on the magnetic circuit,the energy conversion efficiency control method of the fast mechanism is proposed.On this basis,in order to reduce the bounce of the moving parts at the end of the opening process,when the gap between the moving and static contacts reaches the safe distance,the electromagnetic buffer is introduced to reduce the speed at the end of the opening process,for satisfying the reliability design requirements of the mechanical characteristics.