A Study on Mode-Switching Control of TCSC Based on Conditional Firing of Thyristor

The mode-switching control method of thyristor-controlled series capacitor is of great importance to power system stability. It is very difficult, if not impossible, to realize mode-switching only by changing firing angles. A method of predicting current zero-crossing time is proposed first to provide line current synchronization signals for switching control in time. In the switching strategy from capacitive mode to inductive vernier mode, the thyristor conditional firing is put forward. The thyristor will be fired and conducted on condition that both line current and capacitor voltage are in phase. Simulation and experimental results show that the proposed switching method can make the switching process faster with improved dynamic performance.