| With the rapid development of high voltage direct current (HVDC) transmissionproject, novel energy and electrical equipment, vacuum circuit breaker (VCB) became oneof the focuses in the industrial research. The active DC VCB is taken as the research objectby comparing different DC breaking methods, designing the commutation parameters andresearching the magnetic properties.The commutation parameters of the active DC VCB determine the breaking capability.In this thesis, a novel method for designing the commutation parameters has beenproposed. And the commutation parameters are estimated based on the empirical formulaand the simplified circuit equations. Moreover, the circuit equations are given by theprinciple of the active artificial zero and solved using the variable step size fourth-orderDragon Kutta numerical method. And the constraints are determined according to the DCbreaking requirement and the commutation parameters are optimized using the geneticalgorithm (GA).Research of the topology of the medium voltage (MV) DC VCB. The commutationparameters for two different structures are estimated, optimized and compared based on thesimulations of breaking process. The results show that the novel non-trigger switchtopology has more advantages in terms of the cost of the commutation parameters. And thebreaking process of the MVDC VCB is simulated and the influences of differentcomponents is researched. Furthermore, the commutation parameters of the MVDC VCBwith snubber capacitor are optimized and the breaking process is researched under theoptimal parameters.Design of the commutation parameters of the HVDC VCB with single module andmulti-module. By simulating and comparing the breaking process of the single module,multi-module under synchronized and asynchronized case, it can seen that the singlemodule of HV DC VCB has advantages in terms of the capacitor cost and control.Analyses of the harmonic magnetic field of the VCB under different frequency alternating currents (AC) cases for studying the influence of AC frequency on the magneticfield. By numerically computing the transient magnetic field of the VI in DC breakingprocess with different commutation frequency, the distribution of surplus longitudinalmagnetic flux density in arc center plane at current zero under different commutationfrequency has been obtained. By sampling the typical points at center and rim regionwithin the arc center plane and comparing the transient magnetic field during the breakingprocess of DC VCB, the distribution of the surplus longitudinal magnetic flux density ofthe sampling points has been compared and analyzed, and the value in the center of the arcregion is larger than that of the rim region. |
