Impedance Control of Thyristor Controlled Series Capacitor to Improve the Transfer Capability of Remote Wind Farms

In this paper, we put forward a new impedance control method of thyristor controlled series capacitor (TCSC) by modifying variable structure PID feedback of firing angle, aiming at improving the transfer capability of remote wind farms. TCSC can get the best results with nonlinear closed-loop control method, but it is very difficult, if not impossible, to be implemented because a huge amount of data is required. The impedance controller with variable structure PID feedback of firing angle is designed as follows: the coefficient of its integral part is equal to zero before or around the moment that measuring impedance reaches the desired impedance first time, meanwhile it´s called PD controller; then add the integral part and it becomes PID controller. When TCSC steps from different impedance values to the same, the value of error accumulator changes a little, and so a better approximate control effect is obtained. Digital simulation and dynamic experiment results show that this control method can improve the transfer capability with good dynamic and static performance.