As a new type of HVDC converter equipment

the controllable line-commutated converter (CLCC) valve can realize the converter bridge arm actively turn off by adopting a dual-branch topology composed of fully semi-controlled power electronic devices

which fundamentally eliminates the commutation failure of the conventional DC system and ensures the safe and stable operation of the DC system. To fully test the transient steady-state operation performance and engineering availability of the CLCC valve

this paper first introduces the working principle and operation characteristics of the CLCC valve. It proposes the type test assessment items and requirements of the CLCC valve through the electrical stress analysis of transient steady-state operation conditions of the converter valve

combined with the LCC valve test standard. Secondly

according to the special operating conditions of the CLCC valve

the equivalent test circuit and scheme are studied

and the equivalent test platform of forced commutation force of the controllable commutation converter valve is developed. Finally

relying on the ±500kV UHVDC transformation project from Gezhouba to Nanqiao

a complete set of type test scheme was developed and more than 40 insulation and operation tests were passed. The test results show that the CLCC valve meets the operation requirements of the project

and has low extinction angle (7.7°) operation and continuous large current turn-off capability

which can completely avoid the commutation failure caused by AC fault.