| Compared with alternating current transmission,direct current transmission has a series of advantages such as small transmission loss,high transmission capacity,and no system stability.DC transmission is the strategic choice of the development pattern of China’s large power grid.The high voltage DC circuit breaker is the core equipment for establishing and developing high voltage direct current transmission and flexible direct current transmission.Hybrid high voltage DC circuit breaker is one of the important research priorities because of its good dynamic characteristics and low-loss static characteristics,and its parasitic parameter analysis and optimization research is extremely lacking.However this is a key issue that must be recognized and solved in the development of hybrid DC circuit breakers.This thesis focuses on the problem of stray inductance of DC circuit breaker semiconductor modules.The combination of theoretical derivation,simulation calculation and experimental measurement is used to study the influence and optimization of stray inductance.Firstly the working principle of 500kV hybrid DC circuit breaker and the influence mechanism of stray inductance are analyzed,and the stage where the stray inductance has the most serious influence on the breaking performance of the DC breaker is clarified.Secondly,stray inductance extraction is performed for the typical structure of engineering semiconductor modules.At the same time,the influence of stray inductance on the two full bridge structures is also analyzed.Then,a simulation model of the diode full bridge module is established to analyze the influence of stray inductance on the IGBT turn-off voltage and snubber capacitor voltage.The sensitivity coefficient which can quantify the influence of stray inductance is defined,and the principle of stray inductance optimization design of diode full bridge component is proposed.The simulation model of the arrester unit is established,and the influence of the stray inductance of the transfer branch and the energy absorption branch on the snubber capacitor voltage is analyzed.Finally,a structural optimization design scheme of the diode full-bridge module and the arrester unit is proposed.The simulation results show that the optimization effect of the scheme is significant,the stray inductance level is significantly reduced,and the operational reliability of the hybrid DC circuit breaker can be effectively improved. |
