Simulation and Analysis of Monitoring Signals of Thyristor Level Control Unit Considering Parameters Deterioration of Converter Valve

The thyristor control unit (TCU) is the core component of the electric-controlled converter valve control and protection system. It is of great significance to explore the monitoring signal rules of the TCU in depth for real-time monitoring and evaluation of the operation status of the converter valve. Based on the analysis of the working principle of the TCU for the thyristor level of the converter valve and the timing characteristics of the monitoring feedback signal, this article combines the I-V curve characteristics of the thyristor in the converter valve measured on-site. Using MATLAB/Simulink, a six-pulse converter valve simulation model considering multistage thyristor series connection is established. In view of the typical statistical distribution of degradation of series devices, the influence of degradation parameters such as damping capacitors and equivalent insulation resistances of thyristor on the voltage waveform and monitoring signal timing distribution characteristics of each thyristor level in the TCU is studied, and a simulation test verification platform was built.. The results show that when the circuit parameters of the thyristor deteriorate, its feedback signal will appear ahead of the healthy thyristor, and the timing difference will increase with the degree of deterioration. In addition, compared with the deterioration of the damping capacitance parameter, the timing of the feedback signal is more sensitive to the insulation deterioration of the thyristor. When the insulation of the thyristor deteriorates, the healthy thyristors will bear a higher voltage compared to the deteriorated thyristor, and the voltage borne by the thyristor with a deteriorated damping capacitance will increase. Finally, the relevant conclusions obtained from the simulation were verified through experiments. This research can provide support for further real-time online evaluation of the health status of key components of the valve based on TCU unit monitoring signals.