Ultra-high voltage alternating current(UHVAC)network is the key to balance the supply and demand of energy

as well as building strong smart grid and Energy Internet. UHVAC networks are under developing with a steady pace. Reactive power and voltage control is an important measure to ensure the security

reliability and economy of UHVAC networks. The reactive power and voltage characteristics of UHVAC transmission lines are summarized

and the problems of reactive power and voltage control in UHVAC networks are indicated. The reactive power and voltage control methods are reviewed including independent control

coordinated control with neighboring grids and global reactive power optimization of large power grids. At last

some future directions in the field of reactive power and voltage control in UHVAC networks are pointed out

according to the analysis of the current research status and the development trend of ultra-high voltage networks.