Analysis of voltage and frequency operation risks under sending end AC faults

Regarding the operational risks of system voltage and frequency under sending end AC faults, firstly, the operational characteristics of key power electronic devices at the sending end are analyzed in this paper. Then, by examining the variations of DC electrical quantities and control parameters during fault and recovery periods, the risk of commutation failure is analyzed. Additionally, the reactive power surplus of new energy units during faults leads to transient overvoltage upon recovery, increasing the risk of commutation failure. During sending end AC faults, the system experiences a low voltage-high frequency process, while during recovery phase faces commutation failure risks. During commutation failure and recovery periods, the system experiences transient processes of low voltage-high frequency and high voltage-high frequency, respectively. Finally, a simulation model is built using DIgSILENT/PowerFactory, and the simulation results validated the correctness of the mechanism analysis.