Research on coordinated control technology for AC/DC hybrid system in China

As the power industry is rapidly developing in China, the regional grid interconnections are now under construction. Based on the existing planning national grid configuration, the AC/DC coordinated control technology for regional interconnected power grid is developed in this paper. By 2013, there have been six High Voltage Direct Current (HVDC) transmission lines delivering power from Central China to East China. Based on the planning Ultra High Voltage (UHV) power grid in China, a series of simulation tests is carried out. The following topics are investigated in this paper: 1) How multiple HVDC systems support each other under the loss of bipolar HVDC transmission capacity; 2) How the HVDC system is applied to providethe emergent power support for the parallel AC power corridors when severe faults occur in the AC system; 3) How is the impact of the AC/DC coordinated control on the AC system. According to several simulation experiments under the typical kinds of faults, the conclusions can be drawn as follows: 1) Once the bipolar fault occurs at any one of above six HVDC lines, the power transferring and voltage fluctuation of AC network after fault could be dramatically diminished when the power running up is issued to the other five HVDC lines 2) Once a large amount of generation lost occurs in East China Power grid, power run up of above six HVDC lines can significantly improve the stability margin of Central China Power Grid — East China Power Grid. Finally, a suggestion of establishing a coordinated control center is proposed so as to realize the cooperative control among multiple HVDC lines in case of various system emergencies.