Research on overvoltage and fault of a UHV AC/DC hybrid system

In view of the overvoltage problem of an ultra-high-voltage DC (UHVDC) AC/DC hybrid system, this study analyses the overvoltage condition under various fault types and gives the identification criterion of the overvoltage form. Firstly, the model of the +/- 800kV UHVDC and 1000kV UHV AC hybrid system was established in Simulink. The relevant parameters of current and voltage in the hybrid system were simulated and analysed to verify the accuracy and effectiveness of the model. Secondly, the fault simulation of the two system models of AC and DC, respectively, is carried out, and the theoretical analysis of the internal overvoltage caused by the fault is made. Finally, the simulation of the overvoltage condition of the hybrid system under two conditions is carried out, and the waveforms of the important parameters of the AC system and the DC system are obtained. The waveform of each parameter is analysed and the conclusion is obtained. The type of the overvoltage fault of the UHV AC/DC hybrid system is analysed, which provides the basis for fault type judgement.