605 / 2017-05-15 16:23:47

Research on a novel bidirectional direct current circuit breaker

14277,14276,13546,14275

A novel medium voltage DC circuit breaker consisting of a high-speed switch and a bridge-type commutation branch, which is based on current injection, is proposed and analyzed in this paper. The commutation branch of this design adopts bridge type, which can break the bidirectional fault current rapidly by triggering different fast thyristor. Meanwhile, after the current is commutated to the commutation branch completely, the freewheeling diodes can provide time for dielectric recovery with zero recovery voltage across high-speed switch, as a consequence, the reliability of fault current breaking is improved. Firstly, the principle and operation sequence of current breaking of this new topology are described. Based on the simulation model of MATLAB's Simulink platform, the pre-charged voltage of capacitor and the stray inductance in the commutation branch, two key factors affecting the commutation process, are investigated. The relationship between the current commutation capability and the stray inductance at different pre-charged voltages of capacitor in commutation branch is discussed. Then, the operation scheme for different level of fault current with different stray inductance and pre-charged voltage are proposed. Besides, the breaking process in 10kV DC system with different fault current rates of rise are simulated. Finally, based on the simulation results, the prototype of 10kV DC circuit breaker is constructed, and the fault current breaking test is carried out for the current peak value of 25kA, which validates the feasibility and effectiveness of the topology and simulation model well.