Study on synthetic test technology of thyristor level with TCU in the converter valve of HVDC transmission

The converter valve is the core equipment in the HVDC transmission power system and the thyristor level is the basic unit of HVDC converter valve, its performance has a direct effect on the reliability, stability and efficiency of the whole power system. Thus, each thyristor level in the converter valve needs to be test routinely during the maintenance period of the electric equipment in order to grasp the state of the converter valve equipment. Currently there is no specific test scheme for the thyristor level with thyristor control unit (TCU). Therefore, it is particularly urgent to study the synthetic test technology of the thyristor level with TCU in the HVDC converter valve. In this paper, the synthetic test principle, content and methods for the thyristor level with TCU are presented based on the analysis of the thyristor level electrical principles and the IEC 60700-1-2008 standard in order to offer technical support for the operation and maintenance of the HVDC converter valve. In general, the reverse recovery period of thyristor level is the most vulnerable stage of thyristor operation process, so a transient high-voltage pulse is applied to the thyristor level during its reverse recovery period in order to test the damage characteristics of thyristor level. Then, the synthetic test system for the thyristor level is designed and applied to the converter valve test of ±800kV HVDC transmission power project, and the practical test result verifies the reasonability and validity of the proposed synthetic test technology, which meets the need of engineering application.