Application of MMC-UPFC in the 500 kV power grid of Suzhou

To solve the problem regarding the power supply capacity improving and ultra-high-voltage direct current (UHVDC) power assumption of 500 kV Suzhou power network in China, research on the feasibility for application of a unified power flow controller (UPFC) in 500 kV southern power grid of Suzhou is carried out. Furthermore, the scheme of the UPFC integrated and its topology structure is given, and the capacity of the UPFC is determined by system calculation. The principle for the selection of key parameters for the main equipment in the UPFC project is discussed. The effect on the power flow and voltage regulation of 500 kV Suzhou power grid is verified by simulation, which indicates that the regulating by UPFC can eliminate the overload of key transmission section as line tripped, under the heavy load condition in winter. During summer under heavy load conditions, it is beneficial to decrease the capacity of load shedding as the UHVDC bipolar is blocked. In addition, the reactive power control of the UPFC can provide the dynamic voltage support for the power grid, which reduces the probability and the time duration of the commutation failure of the UHVDC.