Study On Impedance Control Of Thyristor Controlled Series Capacitor (TCSC)

Physical simulation experiments of TCSC device can reflect truly the operating characteristics of TCSC to a large extent in real power system. It is of great significance for the practical engineering application of TCSC to resolve the problems in time which are discovered by verifying the basic performaces and control strategies of TCSC equipment.Firstly, the design and application of a set of experimental device for dynamic simulation of TCSC is described in this dissertation, which includes the main TCSC circuit, the protection system and the control system. The components of TCSC are modularized and can be flexibly combined. In addition, the structual parameters of TCSC can be regulated according to the requiremet of the simulation experiment. Hierarchical structure is applied to the controller of this TCSC experimental device and the controllers in different layers perform different control objectives, so the research on various control strategies can be conveniently conducted. The experiment results show that the physical simulation platform is an effective tool to study FACTS devices. It has the capability to carry out measurement, protection and control schemes in real-time.Whether the performance of TCSC device can be implemented or not depends on its impedance control. The PID control is the most widely-used method in TCSC impedance control. The robustness of the traditional PID control is analyzed when TCSC steps to different impedances.The results show that the PID parameters should be adjusted on-line to keep good robustness. The relationship between the PID parameters and ordering impedance is described based on digital simulation. The PID parameters have nothing to do with the impedance before TCSC steps. These parameters should be adjusted according to ordering impedance.The close-loop PID control can play a role in the high impedance mode. When ordering impedance is higher, the effect of integral and differential should be enhanced but the effect of proportion should be weakened. When ordering impedance is lower, the case is the opposite. The single neuron self-adaptive PID control method is presented for TCSC impedance control. The PID parameters are adjusted by the self-adaptive neuron in this method. Compared with the traditional PID control, the simulation results show that the proposed method has good robustness to different ordering impedances and has good static and dynamic performance.The medial layer impedance control of TCSC is directly related to the effectiveness of the top layer control strategies. It is observed that the fundamental impedance performance curve changes according to the line current during digital simulation and physical simulation experiments. And this phenomenon will cause obvious errors when open loop impedance control strategy is used. The formula of TCSC fundamental impedance is deduced when considering the thyristor conduction characteristic and using the line current synchronization, from which the reason why fundamental impedance performance curve changes with the line current is ascertained. Digital simulation considering the thyristor conduction characteristic is performed and some useful conclusions are abtained. At last the method to eliminate the effect of the thyristor conduction characteristic is presented.