Li Xinnian

Study on the impact of commutation failure on AC voltage of rectifier-side in UHVDC

In recent years, a lot of research work about the commutation failure of inverter has been made by many scholars in domestic and abroad. But most of the research is focused on inverter-side AC power system, especially on multifeeded AC systems. Whereas the impact of commutation failure on rectifier-side AC system is less. Based on EMTDC, the simulation model of Fulong-Fengxian ±800kV ultra high voltage direct current transmission(UHVDC) is built, and the sub-model of control and protection system completely comply with the practical project. In order to reappear the fault scene in July 5,2013, the auxiliary Station Power of Fulong is built in the simulation model, including sub-model of station transformer, load and frequency converters. Firstly, in the simulation model the fault is reappeared, and the model is confirmed effective, based on that, the impact of Fengxian and Fulong AC line fault on Fulong 400V bus voltage are researched respectively. The overvoltage of 400V bus and frequency converter of Fulong station caused by AC fault in different operation modes of DC system are studied. Meanwhile two solutions are proposed that protection setting of frequency converter is modified and start-up mode of main pump of water-cooling system is switched from frequency conversion control to soft start. The simulation results can be used as technology reference for the protection value setting of frequency converter and dispatching operation.