Abstract: The high-voltage direct current controllable line commutated converter (CLCC) is a hybrid converter valve with a parallel structure of main and auxiliary branches. The main branch flows through the current at steady-state conditions when an AC fault occurs by the auxiliary branch to take over the main branch current, after the main branch is restored and blocked, it actively turns off to achieve forced commutation, fundamentally solving the problem of phase change failure of the DC system, applicable to China's multi-feed into the DC receiving end of the power grid. To equivalently reproduce the electric and thermal stresses under the steady-state operation of the controllable line commutated converter valve and the transient high voltage, large current, and pulse energy generated by continuous forced commutation process during AC faults, it is necessary to research the controllable turn-off test method of valve components to verify the CLCC valve's ability to resist commutation failure. The transient high voltage and high current stress levels of each sub-valve are analyzed under a single-phase ground fault on the inverter side, which relies on the system simulation results of the Ge'nan DC renovation project, as well as extract the key stress indicators of each sub-valve under actual working conditions. Secondly, a multi-frequency resonant current source and a steady-state high-voltage source periodic composite test method are proposed, and the fault current continuous breaking test device parameter design is completed to simulate the controllable blocking and recovery ability of the bridge arm without external negative voltage application. The feasibility and equivalence of this experimental method have been verified through comparative analysis of experiments and simulations, providing theoretical and technical guidance for the subsequent controllable turn-off tests of controllable line commutated converter valves with different current levels.