Research on the Closing Inrush Current and Overvoltage of 750kV AC Filter Breakers

The AC filter breaker is one of the primary equipment of a convertor station, mainly functioning as absorbing harmonics and providing the reactive power. Therefore, the AC filters need to change their state frequently following the need of the operation mode of the system and the load. In this paper, first, the model of 750kV AC filters in DC converter stations was built by PSCAD/EMTDC simulation software. Besides, the amplitude of the inrush current and overvoltage and the maximum energy absorption of the closing resistor while closing breakers of different filters were calculated. The result showed that the inrush current generated by the shunt capacitor is the highest, and the overvoltage of the main capacitor C1 is the most serious. Finally, the effects of different resistance value of the closing resistor on inrush current, overvoltage and heat were studied, and it was found that the $400 \Omega$ closing resistor is the best choice for the breakers of 750kV AC filters. This paper provided a certain theoretical reference for the selection of the insulation withstanding strength of each component, and proposed a more reasonable resistance value of closing resistors for 750kV AC filter breakers.