Optimization Of Commutation Circuit Parameters And Research On Post-arc Dielectric Recovery For DC Vacuum Circuit Breaker

As the environmental problems caused by the consumption of non-renewable fossilenergy are becoming more and more serious, the new energy power generation has beenattached wide attention. Multi-terminal high voltage DC (HVDC) transmission is one of thekey technologies for improving the reliability and stability of the synchronization of newenergy power generation. Besides, HVDC circuit breaker (CB) becomes the bottleneck ofdevelopment and application for multi-terminal HVDC transmission. In this thesis, the activeDC vacuum circuit breaker (VCB) is taken as the research object. Meanwhile, the optimizationdesign of commutation circuit and the analysis of the post-arc dielectric recovery process forthe DC VCB have been realized.Commutation circuit is the core part of the DC VCB and the appropriate design canincrease the breaking performance and the economy. In this thesis, based on the Kirchhoff law,the differential equations for various stages of DC VCB breaking process are provided andnumerically calculated by using the variable step Runge-Kutta method. According to thecalculation results, the optimal breaking performance, the lowest cost and the shortest sheathdevelopment time are selected as the optimization objective function, respectively. Thecommutation circuit parameters are optimized by using the genetic algorithm (GA) todetermine the commutation inductance (CL) and commutation capacitor(CC) according todifferent operating conditions and different requirements. At the same time, the circuit withcorresponding optimization parameters is simulated and the characteristics of voltage andcurrent for each branch are obtained. The simulation results for different optimizationparameters are analyzed by using the comparative method.Ion, electron and metal vapor particle remain between the contacts in vacuum interrupter(VI) after current zero for the main circuit. If the residue dissipates quickly enough, the breakgap can withstand a certain recovery voltage and the VI can break successfully. Otherwise, thebreak gap reignites. In this thesis, the multi-parameter fusion model is used to analyze thepost-arc dielectric recovery process for the DC VCB. And the earlier stage dominated by thesheath development, the medium stage dominated by the metal vapor attenuation and the finalstage dominated by the static withstanding pressure are analyzed using different models.Moreover, the commutation circuit is re-optimized, combining the re-breakdown criterion. The breaking process for the DC VCB can be divided into arcing phase and post-arcdielectric recovery phase from the angle of arc. Arcing time, arcing energy and other factorsduring arcing phase determine the initial conditions of post-arc dielectric recovery to a certainextent. Post-arc dielectric recovery phase is the key for successful interruption. In this thesis,different influential factors on different stages of post-arc dielectric recovery phase areanalyzed specifically which provides the reference for controlling the post-arc dielectricrecovery characteristics.