TCSC Control
When TCSC operates in the constant impedance mode it uses voltage and current feedback for calculating the TCSC impedance. The reference impedance indirectly determines the power level, although an automatic power control mode could also be introduced.
A separate PI controller is used in each operating mode. The capacitive mode also employs a phase lead compensator. Each controller further includes an adaptive control loop to improve performance over a wide operating range. The controller gain scheduling compensates for the gain changes in the system, caused by the variations in the impedance.
The TCSC is simulated as a controllable voltage source in each phase. The voltage magnitude is the product of equivalent complex impedance and the line current. The expression for the TCSC impedance is given in [1].