1.NARI-Relays Electric Co.Ltd.，Nanjing211102，China;2.Shanghai Management Branch of SGOC，Shanghai201413，China

Based on the control and protection platform for high voltage direct current（HVDC）with independent intellectual property right，the prototype of control and protection system for ultra-high voltage direct current（UHVDC）is designed and developed.The control and protection devices are divided into pole level and converter level，the DC current regulator and voltage regulator are located at the converter level，while the DC current order is given by the pole level.The fire angle and tap are coordinated between two converters in one pole.The entry of converter is implemented by switching the reference of the current regulator.UHVDC protection block sequences are described，and two kinds of protection block sequences at the converter level are designed，one with bypass-pair and the other without.Simulation shows the good performance of the control and protection system for UHVDC.