The periodic firing and extinction test method of STATCOM valve employing chain circuits is very important in its application. Combined with the design of ±50Mvar chain circuits topology STATCOM

the voltage and current stresses of valves during different states are studied based on simulation results. The circuits

method and mathematical model for periodic firing and extinction test are presented. Furthermore

the principle is also investigated elaborately and proved by simulation with PSCAD. Finally the test results are given

which verify the feasibility and correctness of the test method.